Introduction & Content
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What if you could finally understand the entire skin – its layers,
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glands, hair, nails and even the breast? In this video, I’ve compiled the most important
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anatomy and function of the skin into one visual presentation you can follow step by step.
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First, we’ll answer a simple question: what is the integument? We’ll treat the skin as an
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organ in its own right, and talk in detail about its function in protection, thermoregulation,
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immunity, vitamin D production, and so on. Then we’ll look at the surface patterns of
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the skin, the stuff you can see just by looking at your hand, like fingerprints and dermal ridges.
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After that, we’ll go into the layers of the skin and see what each layer is doing.
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Once we’ve done that, we’ll talk through the skin appendages such as sweat and sebaceous glands,
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hair follicles and nails. And finally, we’ll zoom out to the breast and see how the mammary
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gland is built as a modified skin gland. I’ll also throw in a few clinical notes
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along the way, and by the end, you should be able to look at your own
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skin and actually understand what you’re seeing. What’s up everyone, my name is Taim. I’m a medical
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doctor, and I make animated medical lectures to make different topics in medicine visually easier
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to understand. If you’d like a PDF version or a quiz of this presentation, you can
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find it on my website, along with organized video lectures to help with your studies.
What is the Integument?
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Alright, let’s start with that first question: what exactly is the integument?
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So, when we say integument, we’re not just talking about “skin” in the casual sense.
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In anatomy, the integumentary system is this whole outer covering of the body plus its accessories.
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That includes the skin with its layers, the hair, the nails, the sweat glands, the sebaceous glands,
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and in the chest region the mammary glands as well. If you put all of that together,
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it’s not a small structure either. In an average adult it covers around 1.5–2
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square metres and weighs several kilos, which makes it the largest organ of the body by area.
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Now, it helps to think of skin the same way you’d think of the liver or the heart. It’s
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an organ with specific jobs and every detail we go through later in the video will plug into one
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of these jobs, so before we cover any parts of the skin, we’ll quickly make sense of what the
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integument is actually doing for you all the time. First, protection is the most obvious one. The
Function 1: Protection
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outer layer of the epidermis is full of keratinised, dead cells that form a tough,
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waterproof barrier. These cells are packed into multiple layers with lipids between them. Because
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of that structure, mechanical forces such as rubbing or minor impacts are spread out over many
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layers instead of tearing through living tissue immediately. The lipid component slows down
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evaporation of water from the surface, so even though the air around you is often drier than the
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inside of your body, water does not just freely escape through the skin. We see how important
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this barrier is when it is lost, for example in large burns, where fluid loss through the damaged
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skin can become life-threatening. The integument also contributes to protection against sunlight.
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Melanocytes in the deeper epidermis produce melanin, and this pigment absorbs part of the
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UV radiation that would otherwise damage DNA. The integument is also central for
Function 2: Thermoregulation
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thermoregulation. In the dermis there is a network of blood vessels that can dilate when you need to
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lose heat and constrict when you need to conserve it. When the vessels dilate, more warm blood is
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brought close to the surface, and because of that heat is transferred to the environment, and the
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skin often looks redder and feels warm. Eccrine sweat glands then add another layer of control
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by secreting sweat onto the surface. When this sweat evaporates, it takes heat with it, which
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cools the skin and the blood flowing underneath. In cold conditions the vessels constrict so less
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blood reaches the surface, and that reduces heat loss from the core to the environment.
Function 3: Excretion & Barrier For Water
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At the same time, the integument helps with water balance and a small amount of excretion. Sweat
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does not only contain water, it also carries sodium, chloride and small amounts of urea and
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other substances to the surface. If you sweat a lot without replacing fluids and electrolytes,
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you notice the consequences as thirst, dizziness or muscle cramps. In the background, even when
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you are not visibly sweating, there is a small continuous “insensible” water loss through the
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skin, but the keratinised barrier keeps this within a narrow range. When that barrier is
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damaged, much more water can escape, which is one of the reasons why patients with extensive skin
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disease or burns can become dehydrated so quickly. The integument is also a very active part of the
Function 4: Immunity
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immune system. The physical barrier of the epidermis makes it difficult for bacteria,
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viruses and fungi to enter in the first place. The surface of the skin is slightly acidic and covered
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by a mixture of sweat and sebum that contains antimicrobial molecules, and it is colonised by
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a normal skin flora that competes with potential pathogens. Inside the epidermis, Langerhans cells
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move between keratinocytes, pick up antigens that have managed to cross the surface, and carry
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them to regional lymph nodes to present them to T-cells. In the dermis you also find mast cells,
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macrophages and lymphocytes ready to react. So the integument is constantly sampling the environment
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and feeding information to the immune system. One function that is easy to forget is its role in
Function 5: Vitamin D metabolism
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vitamin D metabolism. In the deeper layers of the epidermis there is a cholesterol-related molecule
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called 7-dehydrocholesterol. When this part of the skin is exposed to UV-B light from the sun,
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that energy changes the structure of 7-dehydrocholesterol into pre-vitamin D₃,
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which then spontaneously becomes vitamin D₃, or cholecalciferol. This vitamin D₃ enters
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the bloodstream and is carried to the liver, where it is converted to 25-hydroxyvitamin D,
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and then to the kidneys, where it is converted to 1,25-dihydroxyvitamin D, also called calcitriol.
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Calcitriol is the active form of vitamin d, which acts as a hormone that helps regulate
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calcium and phosphate balance and supports normal bone mineralisation. Studies on vitamin D status
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in different populations consistently show that low sun exposure or living at high latitudes can
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lead to lower vitamin D levels, because the first step in that pathway depends on the skin seeing
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enough UV-B. So in that sense, your integument is also the first organ in an endocrine chain.
Function 6: Sensation and Communication
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Finally, the integument is a huge sensory and communication surface. It contains free nerve
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endings that detect pain and temperature, and specialised receptors that detect light touch,
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pressure and vibration. These receptors are especially dense in areas such as the
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fingertips and lips, which is why you can feel very small differences in texture and shape
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there. The skin also participates in non-verbal communication through changes in colour and
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texture, such as blushing, paling or getting goosebumps when arrector pili muscles contract
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in response to emotional or thermal stimuli. So those are the main functions of the skin.
Surface Patterns of the Skin
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With that in place, we can now move from the overall definition to the first things
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you can actually see on your own skin, the surface patterns like fingerprints, ridges and lines.
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If you look closely at the back of your hand in good light, you’ll see that the
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skin is not really smooth by nature. It’s divided into tiny, almost rhomboid fields.
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The shallow grooves that border these fields are called skin sulci. Between them you have small
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slightly raised islands of skin, called skin areas. These areas look a bit swollen compared
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to the grooves because the collagen and elastic fibres in the dermis pull up on them from below.
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These sulci and areas aren’t random. In most regions they form an irregular but recognisable
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pattern of small rhombs or polygons. This surface pattern reflects what is happening
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deeper in the dermis. In the reticular layer – which we’ll look at in more detail later – the
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thicker collagen bundles are not arranged as a chaotic tangle. They tend to run in preferred
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directions that vary from region to region on the body. If you imagine connecting the
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long axes of many neighbouring skin areas, you can trace out lines that follow this dominant
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direction of tension. These are the tension lines, also called cleavage lines or Langer’s lines.
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Historically, Langer mapped these lines on cadavers by making small circular cuts in the
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skin and observing how the circles deformed. In most places they stretched into ellipses,
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and by joining the long axes of these ellipses he produced a map of the predominant collagen
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orientation in the dermis. In clinical practice, surgeons often try to place incisions along these
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lines, or at least parallel to the local pattern of tension, because wounds that
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follow them usually heal with narrower, less conspicuous scars than cuts that cross them.
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On the surface, many natural skin folds line up with these directions of tension,
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for example flexion grooves around joints, the creases on the palms and several common facial
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and body wrinkles. With age, as elastic fibres degenerate and the skin loses some of its recoil,
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these folds deepen and new wrinkles tend to appear along the same lines. That is why facial
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wrinkles have fairly predictable orientations. Now, if you look at the palm, the pattern changes.
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Instead of a fine net of rhomboid areas, you see strong ridges running in arcs and loops.
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These are dermal ridges or papillary ridges. They correspond to large dermal papillae that
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project up into the epidermis, especially in thick skin regions like the palms and soles.
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The overlying epidermis follows these ridges and grooves, and together they form the fingerprints
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and footprints that are unique to each person. The reason these ridges are so prominent here
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is partly mechanical and partly functional. Mechanically, they improve grip by increasing
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friction between the skin and whatever you are holding or standing on. Functionally,
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they increase the surface area available for sensory receptors and sweat pores. Many of
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the tactile receptors in the dermis sit close to these ridges, so when you touch an object, tiny
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differences in texture and pressure are translated into small distortions along the ridges, which are
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then picked up by the receptors beneath. At several points on the palm the ridged
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skin forms low, rounded pads – at the tips of the fingers, between the base of the fingers,
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and in the pads at the base of the thumb and the little finger. These pads are called
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tactile elevations. They are areas where the palmar skin is a bit thicker and packed with
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sensory nerve endings, so they are the main contact zones when you press or grip objects.
Layers of the Skin
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So now that we’ve looked at the surface patterns, let’s start moving down through the
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layers themselves and see how the skin is actually built from the outside in.
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So let’s cover the layers of the skin now. When you take a cross-section of skin, you
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can divide it into three main parts: the epidermis on top, the dermis underneath, and then a deeper
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subcutaneous tissue, or hypodermis, that blends into the fat and fascia of the body. Each of these
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has its own structure and its own job, so we’ll take them one by one, and we will start with the
Epidermis
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epidermis. The epidermis is a stratified squamous keratinised epithelium. That basically means it
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is made of several layers of flat cells, and the cells at the surface are packed with keratin and
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have lost their nuclei. If we start at the bottom and work our way up, the first layer you meet is
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the basal layer. This is a single layer of mostly cuboidal cells sitting on the basement membrane.
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These basal cells are mitotically active, so they keep dividing and pushing new cells
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upwards. It also contain melanocytes and Merkel cells, which we will come back to in a moment.
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Just above that is the spinous layer. Under the microscope, the cells here look like they have
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little spines or prickles between them. Those “spines” are actually desmosomes,
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which are junctions that link the cells together. As the basal cells move up into this layer,
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they start producing more keratin and become slightly larger and flatter.
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Above the spinosum lies the granular layer. The cells here are flatter again and contain dark
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keratohyalin granules. These granules are full of proteins that will later help bundle the keratin
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filaments together. At the same time, the cells start to release lipid-rich contents from lamellar
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granules into the spaces between them. Those lipids act like a seal between the cells, which is
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an important part of why the surface of the skin is water-resistant. So in this layer, the cell
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is basically preparing to die in a very organised way, and at the same time it is helping build the
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barrier that stops water and many substances from passing freely across the epidermis.
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In thick skin, like on the palms and soles, you then see a thin, pale layer called the stratum
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lucidum. The cells here have lost their nuclei and organelles, and they look clear and homogeneous
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in histological sections. Not all textbooks emphasise this layer in thin skin, but in thick
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skin it is a clear “transition zone” between the granular layer and the fully keratinised surface.
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On top of that you have the stratum corneum. This is a stack of dead,
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flattened cells packed with keratin, embedded in lipids. There are no nuclei, no organelles,
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and no active metabolism here. The combination of stiff keratin and intercellular lipids gives this
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layer its toughness and its low permeability. When you rub your skin or when you wash your hands, you
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are mostly interacting with this dead corneum, not with living tissue underneath. The very outermost
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sheets of the corneum, which are in the process of flaking off, are sometimes referred to as
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the stratum disjunctum. These are the cells that are just about to be shed into the environment.
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Within these layers, you don’t just have one type of cell. The majority are keratinocytes. They are
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born in the stratum basale, gradually move upward, accumulate keratin, lose their nuclei and finally
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get shed at the surface. This constant turnover is what allows the skin to renew itself and repair
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minor damage. Mixed in with them, especially in the basal layer, are melanocytes. These cells make
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melanin in melanosomes and transfer these pigment granules into surrounding keratinocytes. Inside
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those keratinocytes, the melanin tends to sit like a cap over the nucleus and absorbs UV radiation,
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which helps protect the DNA in that cell from UV-induced damage. The number of melanocytes is
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fairly similar between individuals; most of the visible difference in skin colour comes from how
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much melanin they produce and how it is packaged. Also in the epidermis you find Langerhans cells.
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These are dendritic cells that come from the bone marrow. They move between keratinocytes in the
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spinosum and other layers, sampling antigens that get into the epidermis. When they pick
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up something suspicious, they can migrate to local lymph nodes and present these antigens to
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lymphocytes, which links the skin to the adaptive immune system. In the basal layer, especially
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in areas of fine touch like the fingertips, you also find Merkel cells. These are cells
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that sit in close contact with afferent nerve endings, forming what are called Merkel discs.
Dermis
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Under the epidermis lies the dermis. The dermis is made of connective tissue rather than epithelium.
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It contains the bulk of the skin’s collagen and elastic fibres, the capillary networks that feed
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the epidermis, most of the sensory receptors, and the deeper parts of hair follicles and glands. We
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usually split it into two layers: the papillary layer on top and the reticular layer beneath.
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The papillary layer sits just under the epidermis. It is made of a looser connective tissue with thin
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collagen and elastic fibres. It forms small projections called dermal papillae that push
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up into the underside of the epidermis. Where these papillae are especially large and regularly
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arranged, they form the dermal part of the ridges you see as fingerprints and the ridged pattern on
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the palms and soles. Inside these papillae you find capillary loops that supply oxygen
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and nutrients to the avascular epidermis, and you often find Meissner’s corpuscles
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and other touch receptors here as well. So this layer is important both for nourishing
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the epidermis and for creating the fine surface patterns and tactile sensitivity of the skin.
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Deeper down is the reticular layer. This is thicker and denser. The collagen fibres here
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are larger and form a network of bundles that intersect and loop around, creating a mesh
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that gives the skin much of its tensile strength. Those bundles are not oriented randomly; they have
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preferred directions depending on the region of the body, which is what we saw earlier as tension
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lines and Langer’s lines at the surface. Elastic fibres woven through this collagen network give
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the skin some ability to stretch and then recoil. Within the reticular dermis you find the roots of
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hair follicles, sebaceous glands, the secretory coils of sweat glands, larger blood vessels and
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many of the deeper sensory receptors. When you get a deep cut that reaches into this layer,
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you are more likely to damage these structures and to create a scar, because you are disrupting
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the main supporting framework of the skin. Below the dermis, the connective tissue
Hypodermis
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gradually becomes looser and starts to accumulate more fat. This is the subcutaneous tissue,
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the hypodermis. The hypodermis is composed mainly of adipose tissue with a thickness that varies a
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lot between body regions and between individuals. It tends to be thickest in areas like the abdomen,
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buttocks and thighs, where it serves as an energy store, a cushion and an insulating layer.
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Running from the dermis down through the subcutaneous tissue to the deep fascia you
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find strands of connective tissue called skin ligaments. Where these ligaments are short and
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strong, like in the palm, the skin is tightly anchored and hardly moves over the underlying
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structures. Where they are longer and more lax, the skin can glide more freely, like over the back
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of the hand. In some locations, especially over bony prominences such as the elbow or patella, you
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can also find small subcutaneous synovial bursae. These are fluid-filled sacs that reduce friction
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between the skin and the bone when the joint moves or when there is pressure from outside.
Appendages of the Skin
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Now that we’ve built the layers of the skin, the next step is to look at what is actually
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connected to this wall. The skin is not just a flat sheet of tissue. It has a whole set of
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appendages that grow out of it and sit inside it: the sweat glands, the sebaceous glands,
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the hair and the nails. All of these develop from the epidermis, but they extend down into the
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dermis and sometimes into the hypodermis, and they are a big part of how the integument does its job.
Sweat Glands
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We’ll start with the sweat glands. The most common type is the eccrine sweat gland. Under the
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microscope, each eccrine gland looks like a simple coiled tube. The secretory portion is a tight ball
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of tubules deep in the dermis or upper hypodermis, and from that ball a straight duct runs up through
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the dermis and epidermis and opens directly onto the skin surface as a tiny pore. These glands
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are scattered almost everywhere on the body, but they are especially dense on the palms,
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soles and forehead. The fluid they produce is a thin, watery sweat made mostly of water
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with sodium, chloride, small amounts of potassium, urea and other solutes.
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The second main type is the apocrine sweat gland. These glands are also coiled tubular glands,
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but they are larger, sit deeper, and instead of opening directly onto the skin they usually empty
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into the upper part of a hair follicle. They are present at birth but do not become fully
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active until puberty, when they are influenced by androgens. The secretion they produce is more
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viscous than eccrine sweat and contains proteins and lipids. On its own it has little smell,
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but when skin bacteria break down its components on the surface, they produce volatile compounds
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that give body odour. These glands are mainly under adrenergic sympathetic control and tend
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to respond to emotional stress as well as to thermal stimuli, which is why people
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often notice dampness and odour in the axilla during anxiety or embarrassment even if the
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rest of the body is not particularly warm. Several other glands can be thought of as
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modified sweat glands that have specialised for local tasks. The mammary gland, which we
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will cover in more detail later, is essentially a highly developed, modified apocrine gland in the
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anterior thoracic wall that produces milk. There are other modified apocrine glands aswell like
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around the areola, that help lubricate and protect the nipple during breastfeeding. In the eyelids,
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along the lash margin, there are ciliary glands. Inflammation of these can produce a stye. In
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the external acoustic meatus you have ceruminous glands that produce cerumen,
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or earwax, which protects the canal. In the nasal vestibule there are small nasal
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sweat glands. All of these variations are adapted to the needs of a particular region.
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Running alongside the sweat glands are the sebaceous glands that look like a cluster of small
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units, or acini, that open into a short duct. The cells in these acini fill up with lipids and then
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disintegrate, releasing their contents into the duct. Because the entire cell is sacrificed to
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deliver the secretion, this is called a holocrine type of secretion. Most sebaceous glands are
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attached to hair follicles and empty into the follicular canal. From there, the oily mixture,
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called sebum, spreads over the surface of the skin and along the hair shaft. Sebum contains
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triglycerides, wax esters, squalene and some breakdown products, and it helps to lubricate the
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skin and hair, reduce water loss from the surface and provide a hydrophobic barrier. There are also
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“free” sebaceous glands that open directly onto the skin without a hair follicle. You see them,
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for example, on the lips or at the margin of the eyelids. Sebaceous activity increases under the
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influence of androgens at puberty, which is one reason acne tends to flare at that time. When
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the duct of a sebaceous gland becomes blocked, sebum can accumulate and form comedones or cysts.
Hair
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If we look at hair next, each hair is built as a small organ in its own right. It starts with
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a hair follicle. At the base of this follicle is an expanded region called the hair bulb. Pushing
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up into the base of the bulb from below is a projection of dermal connective tissue
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called the dermal papilla. This papilla carries capillaries and connective tissue that supply the
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growing hair matrix cells with nutrients and signalling molecules. As matrix cells divide
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and move upwards, they differentiate, fill with hard keratin, and form the shaft of the hair,
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much like keratinocytes in the epidermis but in a more focused, cylindrical arrangement.
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The part of the hair you can see above the skin is the hair shaft. Inside the skin, the portion
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from the surface down to the bulb is called the hair root. You can also see an outer cortex and,
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in many hairs, a central medulla. The cortex contains densely packed keratinised cells with
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pigment granules, which give the hair its colour. The medulla, when present, is made
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of more loosely arranged cells and air spaces. Attached to the side of each follicle is a small
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smooth muscle called the arrector pili muscle. One end is fixed to the dermis, and the other
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end attaches to the connective tissue sheath of the follicle. When this muscle contracts,
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it pulls the hair into a more vertical position and causes a slight depression
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of the skin surface on one side, which makes the surrounding area bulge up. This is what you see
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as goosebumps. In furry animals this mechanism increases the thickness of the insulating air
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layer trapped in the coat. In humans it has less physiological importance, but it is still
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part of the sympathetic “fight-or-flight” response and of thermoregulatory reflexes.
Nail
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Finally, the third major appendage is the nail. A nail is a specialised plate of hard keratin
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that sits on a modified patch of skin. The visible part of the nail is the nail body, or nail plate.
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It has two lateral borders which are tucked into shallow grooves formed by the surrounding skin,
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and a free border distally, which grows over the tip of the finger or toe. Proximally,
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the nail plate extends under a skin fold. The portion of the nail hidden under this fold is
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the nail root. Deep to the root lies the nail matrix. This is the region of proliferating
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cells that actually produce the nail. As these matrix cells divide and keratinise, they push the
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older cells distally, and that slow, continuous movement is what causes the nail to grow forward.
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The pale, half-moon shaped area you can see at the base of some nails is the lunule,
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which is the superficial part of the matrix shining through a slightly opaque overlying plate.
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The skin around the nail forms the proximal and lateral nail folds. At the proximal end,
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where the skin overlaps the base of the nail plate, the epidermis forms a thin cuff called
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the eponychium. This is what people often call the “cuticle”. It helps protect the newly formed
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nail as it emerges from the matrix. Distally, under the free edge of the nail, the skin is
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called the hyponychium. Beneath the nail plate itself lies the nail bed. This is a specialised
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dermis with a rich capillary network that gives the nail its pink colour where the plate is
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thin and translucent. Because the nail bed is so vascular and the plate is relatively transparent,
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the nail can act as a quick visual “window” to assess peripheral perfusion and oxygenation,
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for example by looking at capillary refill or at changes in colour in hypoxia.
Breast (Mammary Glands)
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Now that we’ve covered the main skin appendages, I want to zoom out for a
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moment and look at one special structure that is built on the same principles, the breast.
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The breast is a specialised area of skin and subcutaneous tissue that contains a
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modified apocrine gland called the mammary gland, together with fat and connective tissue. So even
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though we often think of it as its own organ, it is still part of the integumentary system.
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On the surface we can see two landmarks: the areola, which is the circular pigmented skin
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around the nipple, and the nipple, which is basically a small projection containing
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the openings of the lactiferous ducts. When the smooth muscle in the nipple and areola contracts,
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for example in response to cold or stimulation during breastfeeding, the nipple becomes more
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prominent and firmer, which helps the infant latch on. Scattered in the areolar skin you
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can see small bumps called the areolar glands. These are modified sebaceous and sweat glands
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that secrete an oily, protective fluid onto the surface. That secretion helps lubricate
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the nipple and areola and may also have a role in scent cues during breastfeeding.
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Deep to this surface, the mammary gland itself is arranged into lobes and lobules
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embedded in a background of fat. In a typical adult breast there are about
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fifteen to twenty lobes of glandular tissue. Each lobe is made up of many smaller lobules,
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and each lobule contains clusters of secretory units called alveoli. The epithelial cells in the
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alveoli are the ones that actually produce milk during lactation. Around them sit myoepithelial
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cells that can contract and help squeeze the milk out. From each lobe, the small ducts draining the
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alveoli join to form a single larger lactiferous duct. These ducts converge towards the nipple,
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and just before they reach it, each one widens slightly into a lactiferous sinus
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and then narrows again to open on the nipple surface. When the breast is not active, for
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example before pregnancy, the glandular component is relatively small and much of the volume is fat.
28:03
During pregnancy and lactation, the glandular elements proliferate and the alveoli enlarge,
28:09
so the proportion of glandular tissue increases and the breast becomes fuller and heavier.
28:14
Holding all of this together is a framework of connective tissue called the suspensory ligaments
28:19
of the breast. These are fibrous bands that run from the dermis of the overlying skin down
28:25
through the breast tissue to the deep pectoral fascia. They divide the breast into lobes and
28:31
help maintain its general shape and position on the chest wall. Because they connect the gland to
28:36
the skin, any process that pulls on them, such as a fibrotic tumour, can cause dimpling or puckering
28:43
of the overlying skin, which is one of the classic clinical signs you look for on breast examination.
Ending
28:48
And with that, we’ve now covered the detailed anatomy of the skin and its appendages – from
28:54
the basic layers and surface patterns to glands, hair, nails and even the breast.
28:58
I really hope you found that helpful. I’ve made free courses for other topics
29:02
here on YouTube if you wanna keep learning, otherwise if you want a handmade PDF version
29:06
of this lecture or take a quiz to test your knowledge, or access an organized list of all
29:09
my videos, you can find everything on my website. Thanks for watching! See you in the next one.Introduction & Content
0:00
What if you could finally understand the entire skin – its layers,
0:04
glands, hair, nails and even the breast? In this video, I’ve compiled the most important
0:10
anatomy and function of the skin into one visual presentation you can follow step by step.
0:17
First, we’ll answer a simple question: what is the integument? We’ll treat the skin as an
0:23
organ in its own right, and talk in detail about its function in protection, thermoregulation,
0:28
immunity, vitamin D production, and so on. Then we’ll look at the surface patterns of
0:33
the skin, the stuff you can see just by looking at your hand, like fingerprints and dermal ridges.
0:39
After that, we’ll go into the layers of the skin and see what each layer is doing.
0:44
Once we’ve done that, we’ll talk through the skin appendages such as sweat and sebaceous glands,
0:49
hair follicles and nails. And finally, we’ll zoom out to the breast and see how the mammary
0:55
gland is built as a modified skin gland. I’ll also throw in a few clinical notes
1:00
along the way, and by the end, you should be able to look at your own
1:03
skin and actually understand what you’re seeing. What’s up everyone, my name is Taim. I’m a medical
1:08
doctor, and I make animated medical lectures to make different topics in medicine visually easier
1:12
to understand. If you’d like a PDF version or a quiz of this presentation, you can
1:16
find it on my website, along with organized video lectures to help with your studies.
What is the Integument?
1:20
Alright, let’s start with that first question: what exactly is the integument?
1:25
So, when we say integument, we’re not just talking about “skin” in the casual sense.
1:30
In anatomy, the integumentary system is this whole outer covering of the body plus its accessories.
1:37
That includes the skin with its layers, the hair, the nails, the sweat glands, the sebaceous glands,
1:43
and in the chest region the mammary glands as well. If you put all of that together,
1:48
it’s not a small structure either. In an average adult it covers around 1.5–2
1:53
square metres and weighs several kilos, which makes it the largest organ of the body by area.
2:00
Now, it helps to think of skin the same way you’d think of the liver or the heart. It’s
2:04
an organ with specific jobs and every detail we go through later in the video will plug into one
2:10
of these jobs, so before we cover any parts of the skin, we’ll quickly make sense of what the
2:15
integument is actually doing for you all the time. First, protection is the most obvious one. The
Function 1: Protection
2:21
outer layer of the epidermis is full of keratinised, dead cells that form a tough,
2:27
waterproof barrier. These cells are packed into multiple layers with lipids between them. Because
2:33
of that structure, mechanical forces such as rubbing or minor impacts are spread out over many
2:38
layers instead of tearing through living tissue immediately. The lipid component slows down
2:44
evaporation of water from the surface, so even though the air around you is often drier than the
2:49
inside of your body, water does not just freely escape through the skin. We see how important
2:53
this barrier is when it is lost, for example in large burns, where fluid loss through the damaged
2:59
skin can become life-threatening. The integument also contributes to protection against sunlight.
3:05
Melanocytes in the deeper epidermis produce melanin, and this pigment absorbs part of the
3:10
UV radiation that would otherwise damage DNA. The integument is also central for
Function 2: Thermoregulation
3:16
thermoregulation. In the dermis there is a network of blood vessels that can dilate when you need to
3:22
lose heat and constrict when you need to conserve it. When the vessels dilate, more warm blood is
3:28
brought close to the surface, and because of that heat is transferred to the environment, and the
3:33
skin often looks redder and feels warm. Eccrine sweat glands then add another layer of control
3:38
by secreting sweat onto the surface. When this sweat evaporates, it takes heat with it, which
3:45
cools the skin and the blood flowing underneath. In cold conditions the vessels constrict so less
3:50
blood reaches the surface, and that reduces heat loss from the core to the environment.
Function 3: Excretion & Barrier For Water
3:56
At the same time, the integument helps with water balance and a small amount of excretion. Sweat
4:02
does not only contain water, it also carries sodium, chloride and small amounts of urea and
4:07
other substances to the surface. If you sweat a lot without replacing fluids and electrolytes,
4:13
you notice the consequences as thirst, dizziness or muscle cramps. In the background, even when
4:18
you are not visibly sweating, there is a small continuous “insensible” water loss through the
4:23
skin, but the keratinised barrier keeps this within a narrow range. When that barrier is
4:30
damaged, much more water can escape, which is one of the reasons why patients with extensive skin
4:35
disease or burns can become dehydrated so quickly. The integument is also a very active part of the
Function 4: Immunity
4:41
immune system. The physical barrier of the epidermis makes it difficult for bacteria,
4:46
viruses and fungi to enter in the first place. The surface of the skin is slightly acidic and covered
4:52
by a mixture of sweat and sebum that contains antimicrobial molecules, and it is colonised by
4:58
a normal skin flora that competes with potential pathogens. Inside the epidermis, Langerhans cells
5:04
move between keratinocytes, pick up antigens that have managed to cross the surface, and carry
5:10
them to regional lymph nodes to present them to T-cells. In the dermis you also find mast cells,
5:15
macrophages and lymphocytes ready to react. So the integument is constantly sampling the environment
5:21
and feeding information to the immune system. One function that is easy to forget is its role in
Function 5: Vitamin D metabolism
5:27
vitamin D metabolism. In the deeper layers of the epidermis there is a cholesterol-related molecule
5:33
called 7-dehydrocholesterol. When this part of the skin is exposed to UV-B light from the sun,
5:40
that energy changes the structure of 7-dehydrocholesterol into pre-vitamin D₃,
5:45
which then spontaneously becomes vitamin D₃, or cholecalciferol. This vitamin D₃ enters
5:51
the bloodstream and is carried to the liver, where it is converted to 25-hydroxyvitamin D,
5:57
and then to the kidneys, where it is converted to 1,25-dihydroxyvitamin D, also called calcitriol.
6:04
Calcitriol is the active form of vitamin d, which acts as a hormone that helps regulate
6:09
calcium and phosphate balance and supports normal bone mineralisation. Studies on vitamin D status
6:15
in different populations consistently show that low sun exposure or living at high latitudes can
6:21
lead to lower vitamin D levels, because the first step in that pathway depends on the skin seeing
6:26
enough UV-B. So in that sense, your integument is also the first organ in an endocrine chain.
Function 6: Sensation and Communication
6:33
Finally, the integument is a huge sensory and communication surface. It contains free nerve
6:39
endings that detect pain and temperature, and specialised receptors that detect light touch,
6:44
pressure and vibration. These receptors are especially dense in areas such as the
6:49
fingertips and lips, which is why you can feel very small differences in texture and shape
6:54
there. The skin also participates in non-verbal communication through changes in colour and
7:00
texture, such as blushing, paling or getting goosebumps when arrector pili muscles contract
7:05
in response to emotional or thermal stimuli. So those are the main functions of the skin.
Surface Patterns of the Skin
7:11
With that in place, we can now move from the overall definition to the first things
7:15
you can actually see on your own skin, the surface patterns like fingerprints, ridges and lines.
7:20
If you look closely at the back of your hand in good light, you’ll see that the
7:24
skin is not really smooth by nature. It’s divided into tiny, almost rhomboid fields.
7:30
The shallow grooves that border these fields are called skin sulci. Between them you have small
7:36
slightly raised islands of skin, called skin areas. These areas look a bit swollen compared
7:42
to the grooves because the collagen and elastic fibres in the dermis pull up on them from below.
7:47
These sulci and areas aren’t random. In most regions they form an irregular but recognisable
7:52
pattern of small rhombs or polygons. This surface pattern reflects what is happening
7:58
deeper in the dermis. In the reticular layer – which we’ll look at in more detail later – the
8:03
thicker collagen bundles are not arranged as a chaotic tangle. They tend to run in preferred
8:08
directions that vary from region to region on the body. If you imagine connecting the
8:13
long axes of many neighbouring skin areas, you can trace out lines that follow this dominant
8:19
direction of tension. These are the tension lines, also called cleavage lines or Langer’s lines.
8:25
Historically, Langer mapped these lines on cadavers by making small circular cuts in the
8:30
skin and observing how the circles deformed. In most places they stretched into ellipses,
8:36
and by joining the long axes of these ellipses he produced a map of the predominant collagen
8:41
orientation in the dermis. In clinical practice, surgeons often try to place incisions along these
8:47
lines, or at least parallel to the local pattern of tension, because wounds that
8:51
follow them usually heal with narrower, less conspicuous scars than cuts that cross them.
8:56
On the surface, many natural skin folds line up with these directions of tension,
9:02
for example flexion grooves around joints, the creases on the palms and several common facial
9:07
and body wrinkles. With age, as elastic fibres degenerate and the skin loses some of its recoil,
9:14
these folds deepen and new wrinkles tend to appear along the same lines. That is why facial
9:19
wrinkles have fairly predictable orientations. Now, if you look at the palm, the pattern changes.
9:25
Instead of a fine net of rhomboid areas, you see strong ridges running in arcs and loops.
9:31
These are dermal ridges or papillary ridges. They correspond to large dermal papillae that
9:37
project up into the epidermis, especially in thick skin regions like the palms and soles.
9:42
The overlying epidermis follows these ridges and grooves, and together they form the fingerprints
9:48
and footprints that are unique to each person. The reason these ridges are so prominent here
9:54
is partly mechanical and partly functional. Mechanically, they improve grip by increasing
9:59
friction between the skin and whatever you are holding or standing on. Functionally,
10:04
they increase the surface area available for sensory receptors and sweat pores. Many of
10:09
the tactile receptors in the dermis sit close to these ridges, so when you touch an object, tiny
10:16
differences in texture and pressure are translated into small distortions along the ridges, which are
10:22
then picked up by the receptors beneath. At several points on the palm the ridged
10:26
skin forms low, rounded pads – at the tips of the fingers, between the base of the fingers,
10:32
and in the pads at the base of the thumb and the little finger. These pads are called
10:36
tactile elevations. They are areas where the palmar skin is a bit thicker and packed with
10:42
sensory nerve endings, so they are the main contact zones when you press or grip objects.
Layers of the Skin
10:47
So now that we’ve looked at the surface patterns, let’s start moving down through the
10:52
layers themselves and see how the skin is actually built from the outside in.
10:56
So let’s cover the layers of the skin now. When you take a cross-section of skin, you
11:01
can divide it into three main parts: the epidermis on top, the dermis underneath, and then a deeper
11:07
subcutaneous tissue, or hypodermis, that blends into the fat and fascia of the body. Each of these
11:13
has its own structure and its own job, so we’ll take them one by one, and we will start with the
Epidermis
11:18
epidermis. The epidermis is a stratified squamous keratinised epithelium. That basically means it
11:24
is made of several layers of flat cells, and the cells at the surface are packed with keratin and
11:30
have lost their nuclei. If we start at the bottom and work our way up, the first layer you meet is
11:36
the basal layer. This is a single layer of mostly cuboidal cells sitting on the basement membrane.
11:42
These basal cells are mitotically active, so they keep dividing and pushing new cells
11:47
upwards. It also contain melanocytes and Merkel cells, which we will come back to in a moment.
11:53
Just above that is the spinous layer. Under the microscope, the cells here look like they have
11:58
little spines or prickles between them. Those “spines” are actually desmosomes,
12:03
which are junctions that link the cells together. As the basal cells move up into this layer,
12:09
they start producing more keratin and become slightly larger and flatter.
12:13
Above the spinosum lies the granular layer. The cells here are flatter again and contain dark
12:19
keratohyalin granules. These granules are full of proteins that will later help bundle the keratin
12:26
filaments together. At the same time, the cells start to release lipid-rich contents from lamellar
12:32
granules into the spaces between them. Those lipids act like a seal between the cells, which is
12:38
an important part of why the surface of the skin is water-resistant. So in this layer, the cell
12:43
is basically preparing to die in a very organised way, and at the same time it is helping build the
12:49
barrier that stops water and many substances from passing freely across the epidermis.
12:55
In thick skin, like on the palms and soles, you then see a thin, pale layer called the stratum
13:00
lucidum. The cells here have lost their nuclei and organelles, and they look clear and homogeneous
13:06
in histological sections. Not all textbooks emphasise this layer in thin skin, but in thick
13:12
skin it is a clear “transition zone” between the granular layer and the fully keratinised surface.
13:18
On top of that you have the stratum corneum. This is a stack of dead,
13:23
flattened cells packed with keratin, embedded in lipids. There are no nuclei, no organelles,
13:28
and no active metabolism here. The combination of stiff keratin and intercellular lipids gives this
13:35
layer its toughness and its low permeability. When you rub your skin or when you wash your hands, you
13:40
are mostly interacting with this dead corneum, not with living tissue underneath. The very outermost
13:46
sheets of the corneum, which are in the process of flaking off, are sometimes referred to as
13:51
the stratum disjunctum. These are the cells that are just about to be shed into the environment.
13:57
Within these layers, you don’t just have one type of cell. The majority are keratinocytes. They are
14:03
born in the stratum basale, gradually move upward, accumulate keratin, lose their nuclei and finally
14:08
get shed at the surface. This constant turnover is what allows the skin to renew itself and repair
14:15
minor damage. Mixed in with them, especially in the basal layer, are melanocytes. These cells make
14:22
melanin in melanosomes and transfer these pigment granules into surrounding keratinocytes. Inside
14:28
those keratinocytes, the melanin tends to sit like a cap over the nucleus and absorbs UV radiation,
14:34
which helps protect the DNA in that cell from UV-induced damage. The number of melanocytes is
14:40
fairly similar between individuals; most of the visible difference in skin colour comes from how
14:46
much melanin they produce and how it is packaged. Also in the epidermis you find Langerhans cells.
14:53
These are dendritic cells that come from the bone marrow. They move between keratinocytes in the
14:58
spinosum and other layers, sampling antigens that get into the epidermis. When they pick
15:04
up something suspicious, they can migrate to local lymph nodes and present these antigens to
15:08
lymphocytes, which links the skin to the adaptive immune system. In the basal layer, especially
15:14
in areas of fine touch like the fingertips, you also find Merkel cells. These are cells
15:20
that sit in close contact with afferent nerve endings, forming what are called Merkel discs.
Dermis
15:26
Under the epidermis lies the dermis. The dermis is made of connective tissue rather than epithelium.
15:33
It contains the bulk of the skin’s collagen and elastic fibres, the capillary networks that feed
15:38
the epidermis, most of the sensory receptors, and the deeper parts of hair follicles and glands. We
15:45
usually split it into two layers: the papillary layer on top and the reticular layer beneath.
15:52
The papillary layer sits just under the epidermis. It is made of a looser connective tissue with thin
15:57
collagen and elastic fibres. It forms small projections called dermal papillae that push
16:03
up into the underside of the epidermis. Where these papillae are especially large and regularly
16:09
arranged, they form the dermal part of the ridges you see as fingerprints and the ridged pattern on
16:14
the palms and soles. Inside these papillae you find capillary loops that supply oxygen
16:20
and nutrients to the avascular epidermis, and you often find Meissner’s corpuscles
16:25
and other touch receptors here as well. So this layer is important both for nourishing
16:29
the epidermis and for creating the fine surface patterns and tactile sensitivity of the skin.
16:35
Deeper down is the reticular layer. This is thicker and denser. The collagen fibres here
16:41
are larger and form a network of bundles that intersect and loop around, creating a mesh
16:46
that gives the skin much of its tensile strength. Those bundles are not oriented randomly; they have
16:52
preferred directions depending on the region of the body, which is what we saw earlier as tension
16:57
lines and Langer’s lines at the surface. Elastic fibres woven through this collagen network give
17:03
the skin some ability to stretch and then recoil. Within the reticular dermis you find the roots of
17:09
hair follicles, sebaceous glands, the secretory coils of sweat glands, larger blood vessels and
17:14
many of the deeper sensory receptors. When you get a deep cut that reaches into this layer,
17:20
you are more likely to damage these structures and to create a scar, because you are disrupting
17:24
the main supporting framework of the skin. Below the dermis, the connective tissue
Hypodermis
17:29
gradually becomes looser and starts to accumulate more fat. This is the subcutaneous tissue,
17:34
the hypodermis. The hypodermis is composed mainly of adipose tissue with a thickness that varies a
17:40
lot between body regions and between individuals. It tends to be thickest in areas like the abdomen,
17:46
buttocks and thighs, where it serves as an energy store, a cushion and an insulating layer.
17:51
Running from the dermis down through the subcutaneous tissue to the deep fascia you
17:56
find strands of connective tissue called skin ligaments. Where these ligaments are short and
18:01
strong, like in the palm, the skin is tightly anchored and hardly moves over the underlying
18:06
structures. Where they are longer and more lax, the skin can glide more freely, like over the back
18:12
of the hand. In some locations, especially over bony prominences such as the elbow or patella, you
18:18
can also find small subcutaneous synovial bursae. These are fluid-filled sacs that reduce friction
18:24
between the skin and the bone when the joint moves or when there is pressure from outside.
Appendages of the Skin
18:29
Now that we’ve built the layers of the skin, the next step is to look at what is actually
18:34
connected to this wall. The skin is not just a flat sheet of tissue. It has a whole set of
18:39
appendages that grow out of it and sit inside it: the sweat glands, the sebaceous glands,
18:45
the hair and the nails. All of these develop from the epidermis, but they extend down into the
18:50
dermis and sometimes into the hypodermis, and they are a big part of how the integument does its job.
Sweat Glands
18:57
We’ll start with the sweat glands. The most common type is the eccrine sweat gland. Under the
19:02
microscope, each eccrine gland looks like a simple coiled tube. The secretory portion is a tight ball
19:09
of tubules deep in the dermis or upper hypodermis, and from that ball a straight duct runs up through
19:15
the dermis and epidermis and opens directly onto the skin surface as a tiny pore. These glands
19:21
are scattered almost everywhere on the body, but they are especially dense on the palms,
19:26
soles and forehead. The fluid they produce is a thin, watery sweat made mostly of water
19:32
with sodium, chloride, small amounts of potassium, urea and other solutes.
19:38
The second main type is the apocrine sweat gland. These glands are also coiled tubular glands,
19:44
but they are larger, sit deeper, and instead of opening directly onto the skin they usually empty
19:50
into the upper part of a hair follicle. They are present at birth but do not become fully
19:55
active until puberty, when they are influenced by androgens. The secretion they produce is more
20:00
viscous than eccrine sweat and contains proteins and lipids. On its own it has little smell,
20:07
but when skin bacteria break down its components on the surface, they produce volatile compounds
20:12
that give body odour. These glands are mainly under adrenergic sympathetic control and tend
20:18
to respond to emotional stress as well as to thermal stimuli, which is why people
20:22
often notice dampness and odour in the axilla during anxiety or embarrassment even if the
20:28
rest of the body is not particularly warm. Several other glands can be thought of as
20:33
modified sweat glands that have specialised for local tasks. The mammary gland, which we
20:38
will cover in more detail later, is essentially a highly developed, modified apocrine gland in the
20:44
anterior thoracic wall that produces milk. There are other modified apocrine glands aswell like
20:49
around the areola, that help lubricate and protect the nipple during breastfeeding. In the eyelids,
20:55
along the lash margin, there are ciliary glands. Inflammation of these can produce a stye. In
21:00
the external acoustic meatus you have ceruminous glands that produce cerumen,
21:04
or earwax, which protects the canal. In the nasal vestibule there are small nasal
21:09
sweat glands. All of these variations are adapted to the needs of a particular region.
21:16
Running alongside the sweat glands are the sebaceous glands that look like a cluster of small
21:21
units, or acini, that open into a short duct. The cells in these acini fill up with lipids and then
21:28
disintegrate, releasing their contents into the duct. Because the entire cell is sacrificed to
21:33
deliver the secretion, this is called a holocrine type of secretion. Most sebaceous glands are
21:39
attached to hair follicles and empty into the follicular canal. From there, the oily mixture,
21:44
called sebum, spreads over the surface of the skin and along the hair shaft. Sebum contains
21:50
triglycerides, wax esters, squalene and some breakdown products, and it helps to lubricate the
21:56
skin and hair, reduce water loss from the surface and provide a hydrophobic barrier. There are also
22:02
“free” sebaceous glands that open directly onto the skin without a hair follicle. You see them,
22:07
for example, on the lips or at the margin of the eyelids. Sebaceous activity increases under the
22:12
influence of androgens at puberty, which is one reason acne tends to flare at that time. When
22:18
the duct of a sebaceous gland becomes blocked, sebum can accumulate and form comedones or cysts.
Hair
22:25
If we look at hair next, each hair is built as a small organ in its own right. It starts with
22:30
a hair follicle. At the base of this follicle is an expanded region called the hair bulb. Pushing
22:35
up into the base of the bulb from below is a projection of dermal connective tissue
22:40
called the dermal papilla. This papilla carries capillaries and connective tissue that supply the
22:45
growing hair matrix cells with nutrients and signalling molecules. As matrix cells divide
22:51
and move upwards, they differentiate, fill with hard keratin, and form the shaft of the hair,
22:57
much like keratinocytes in the epidermis but in a more focused, cylindrical arrangement.
23:03
The part of the hair you can see above the skin is the hair shaft. Inside the skin, the portion
23:08
from the surface down to the bulb is called the hair root. You can also see an outer cortex and,
23:14
in many hairs, a central medulla. The cortex contains densely packed keratinised cells with
23:20
pigment granules, which give the hair its colour. The medulla, when present, is made
23:24
of more loosely arranged cells and air spaces. Attached to the side of each follicle is a small
23:31
smooth muscle called the arrector pili muscle. One end is fixed to the dermis, and the other
23:36
end attaches to the connective tissue sheath of the follicle. When this muscle contracts,
23:41
it pulls the hair into a more vertical position and causes a slight depression
23:46
of the skin surface on one side, which makes the surrounding area bulge up. This is what you see
23:52
as goosebumps. In furry animals this mechanism increases the thickness of the insulating air
23:58
layer trapped in the coat. In humans it has less physiological importance, but it is still
24:03
part of the sympathetic “fight-or-flight” response and of thermoregulatory reflexes.
Nail
24:08
Finally, the third major appendage is the nail. A nail is a specialised plate of hard keratin
24:15
that sits on a modified patch of skin. The visible part of the nail is the nail body, or nail plate.
24:22
It has two lateral borders which are tucked into shallow grooves formed by the surrounding skin,
24:27
and a free border distally, which grows over the tip of the finger or toe. Proximally,
24:32
the nail plate extends under a skin fold. The portion of the nail hidden under this fold is
24:38
the nail root. Deep to the root lies the nail matrix. This is the region of proliferating
24:44
cells that actually produce the nail. As these matrix cells divide and keratinise, they push the
24:50
older cells distally, and that slow, continuous movement is what causes the nail to grow forward.
24:56
The pale, half-moon shaped area you can see at the base of some nails is the lunule,
25:01
which is the superficial part of the matrix shining through a slightly opaque overlying plate.
25:07
The skin around the nail forms the proximal and lateral nail folds. At the proximal end,
25:13
where the skin overlaps the base of the nail plate, the epidermis forms a thin cuff called
25:17
the eponychium. This is what people often call the “cuticle”. It helps protect the newly formed
25:23
nail as it emerges from the matrix. Distally, under the free edge of the nail, the skin is
25:29
called the hyponychium. Beneath the nail plate itself lies the nail bed. This is a specialised
25:35
dermis with a rich capillary network that gives the nail its pink colour where the plate is
25:40
thin and translucent. Because the nail bed is so vascular and the plate is relatively transparent,
25:46
the nail can act as a quick visual “window” to assess peripheral perfusion and oxygenation,
25:52
for example by looking at capillary refill or at changes in colour in hypoxia.
Breast (Mammary Glands)
25:57
Now that we’ve covered the main skin appendages, I want to zoom out for a
26:00
moment and look at one special structure that is built on the same principles, the breast.
26:06
The breast is a specialised area of skin and subcutaneous tissue that contains a
26:11
modified apocrine gland called the mammary gland, together with fat and connective tissue. So even
26:16
though we often think of it as its own organ, it is still part of the integumentary system.
26:22
On the surface we can see two landmarks: the areola, which is the circular pigmented skin
26:27
around the nipple, and the nipple, which is basically a small projection containing
26:31
the openings of the lactiferous ducts. When the smooth muscle in the nipple and areola contracts,
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for example in response to cold or stimulation during breastfeeding, the nipple becomes more
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prominent and firmer, which helps the infant latch on. Scattered in the areolar skin you
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can see small bumps called the areolar glands. These are modified sebaceous and sweat glands
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that secrete an oily, protective fluid onto the surface. That secretion helps lubricate
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the nipple and areola and may also have a role in scent cues during breastfeeding.
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Deep to this surface, the mammary gland itself is arranged into lobes and lobules
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embedded in a background of fat. In a typical adult breast there are about
27:14
fifteen to twenty lobes of glandular tissue. Each lobe is made up of many smaller lobules,
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and each lobule contains clusters of secretory units called alveoli. The epithelial cells in the
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alveoli are the ones that actually produce milk during lactation. Around them sit myoepithelial
27:33
cells that can contract and help squeeze the milk out. From each lobe, the small ducts draining the
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alveoli join to form a single larger lactiferous duct. These ducts converge towards the nipple,
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and just before they reach it, each one widens slightly into a lactiferous sinus
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and then narrows again to open on the nipple surface. When the breast is not active, for
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example before pregnancy, the glandular component is relatively small and much of the volume is fat.
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During pregnancy and lactation, the glandular elements proliferate and the alveoli enlarge,
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so the proportion of glandular tissue increases and the breast becomes fuller and heavier.
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Holding all of this together is a framework of connective tissue called the suspensory ligaments
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of the breast. These are fibrous bands that run from the dermis of the overlying skin down
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through the breast tissue to the deep pectoral fascia. They divide the breast into lobes and
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help maintain its general shape and position on the chest wall. Because they connect the gland to
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the skin, any process that pulls on them, such as a fibrotic tumour, can cause dimpling or puckering
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of the overlying skin, which is one of the classic clinical signs you look for on breast examination.
Ending
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And with that, we’ve now covered the detailed anatomy of the skin and its appendages – from
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the basic layers and surface patterns to glands, hair, nails and even the breast.
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I really hope you found that helpful. I’ve made free courses for other topics
29:02
here on YouTube if you wanna keep learning, otherwise if you want a handmade PDF version
29:06
of this lecture or take a quiz to test your knowledge, or access an organized list of all
29:09
my videos, you can find everything on my website. Thanks for watching! See you in the next one.