Description

General Overview of the Digestive System

This video covers the general structures of the digestive system, including the oral cavity, pharynx, oesophagus, stomach, small intestine, large intestine, and accessory digestive organs.

1. General Structures of the Digestive System:

• Main Digestive Tract:
  • Oral Cavity
  • Pharynx
  • Oesophagus
  • Stomach
  • Small Intestine
  • Large Intestine
• Accessory Digestive Organs:
  • Teeth
  • Tongue
  • Salivary Glands
  • Liver
  • Pancreas
  • Gallbladder

2. External Structures of the Mouth:

• Upper Lip (Labium Superior)
• Lower Lip (Labium Inferior)
• Oral Angle (Labial Commissure)
• Nasolabial Sulcus (Sulcus Nasolabialis)
• Philtrum
• Mentolabial Sulcus (Sulcus Mentolabialis)
• Oral Fissure (Rima Oris)

3. Division of the Oral Cavity:

• Oral Vestibule (Vestibulum Oris)
  • External Borders: Lips and Cheeks
  • Internal Borders: Teeth and Gums
• Oral Cavity Proper (Cavitas Oris Propria)

4. Anatomy of the Lips:

• Frenulum of the Upper Lip (Frenulum Labii Superioris)
• Frenulum of the Lower Lip (Frenulum Labii Inferioris)
• Labial Glands (Glandulae Labialis)

5. Anatomy of the Cheeks:

• Buccinator Muscle (Musculus Buccinator)
• Buccopharyngeal Fascia
• Buccal Fat Pad (Bichat’s Fat Pad)
• Layers of the Skin (Cutis)
• Tunica Mucosa
• Parotid Duct (Ductus Parotideus)
• Papilla of the Parotid Duct (Papillae Ductus Parotidei)

6. Anatomy of the Teeth:

• Basic Tooth Structures:
  • Crown of the Tooth (Corona Dentis)
  • Root of the Tooth (Radix Dentis)
  • Neck of the Tooth (Cervix Dentis)
  • Periodontium
  • Gomphosis (Dentoalveolar Joint)
  • Dental Pulp (Pulpa Dentis)
  • Root Canal (Canalis Radicis Dentis)
  • Apical Foramen (Foramen Apicis Dentis)
  • Dentin (Dentinum)
  • Enamel (Enamelum)
  • Cement (Cementum)
• Types of Teeth:
  • Milk Teeth (Dentes Decidui) – 20 teeth, appear between 6-24 months.
  • Permanent Teeth (Dentes Permanentes) – 32 teeth.
  • Wisdom Teeth (Dentes Serotinus) – Appear between 17-24 years.

7. Tooth Arrangement:

• European system: Teeth are divided into 4 quadrants.
• Each quadrant contains:
  • 2 Incisors (Dentes Incisivi)
  • 1 Canine (Dentes Canini)
  • 2 Premolars (Dentes Premolares)
  • 3 Molars (Dentes Molares)
• Total: 8 teeth per quadrant × 4 quadrants = 32 permanent teeth.
• Milk Teeth: 2 Incisors, 1 Canine, 2 Molars per quadrant.

8. Anatomy of the Gums (Gingiva):

• Alveolar Mucosa – Covers the root of the tooth.
• Gum Proper – Attached to the periosteum.
• Gingival Papillae (Papillae Gingivales)
• Gingival Margin (Margo Gingivalis)
• Gingival Sulcus (Sulcus Gingivalis)

9. Sources:

• Memorix Anatomy, 2nd Edition by Hudák Radovan, Kachlík David, and Volný Ondřej.
• Biorender.
• University notes and lectures.

Transcript

Introduction
0:04
What’s up, Meditay here, Let’s talk about the anatomy of the oral cavity.
0:07
Now since this is my first video of the digestive system, I wanna spend a quick minute giving you a
0:12
little overview of the whole digestive system. And to do that, we’ll use this chocolate
0:16
cheesecake to highlight al the structures it’s gonna go through within your digestive
0:20
system. The reason why I chose a cheesecake is because it most probably starts you salivating
0:26
because you probably wanna eat it. That implies that the Oral cavity is the first part of the
0:30
digestive system. After the oral cavity is the Pharynx. Then when you swallow the food,
0:36
it’s going to go through the esophagus, and then all the way down to your stomach.
0:41
After it’s been processed by the hydrochloric acid in the stomach, it’s then going to enter
0:46
the small intestine, which consists of the duodenum, then the jejunum, and then the
0:50
ileum. And after the Ileum, it’s going to enter the Large Intestine, which consists of the caecum
0:56
and the colon, and then the rectum. And by the time it gets to here,
0:59
this is how the cheesecake’s gonna look like. And the fuller the rectum gets,
1:03
the higher you feel the urge to poop. So those are all the structures of the digestive system.
1:09
But we also have a system of accessory structures which help us digest the food we eat. Those
1:15
include the Teeth, Tongue and Salivary glands. And then in the abdominal cavity, there’s
1:20
the Liver, the Gallbladder and the Pancreas. Our goal is to go through the detailed anatomy
1:27
of all of these structures, one by one. And we’ll start with the oral cavity.
1:31
So in this video, we’re first going to talk about the main external structures of the mouth.
1:37
Then we’re gonna go through the division of the oral cavity, basically how we divide the
1:42
oral cavity. After that, we’re gonna talk about the structures associated with the
1:46
borders of the oral vestibule, which include the anatomy of the Lips, Cheeks and the Teeth.
1:52
Then in the next video, we’ll focus on the other part of the oral cavity,
1:55
which is the oral cavity proper. So here you see the external mouth.
External Structures of the Mouth
2:01
You probably didn’t know this, but here’s the upper lip, and here’s the lower lip.
2:05
They both meet at the lateral ends as the Oral angle, or the labial commissure. Above the lips,
2:12
you’re gonna have two grooves on either side, as you see here, called the Nasolabial Sulcus.
2:17
And then in the middle, there’s going to be a depression called the Philtrum. And then under the
2:22
lips, there’s going to be another Sulcus, called the Mentolabial Sulcus, or mentolabial Fold.
2:29
Now, remember the muscle that’s located inside of your lips?
2:33
The Orbicularis Oris Muscle? This muscle is going to help regulate the opening of your Mouth,
2:39
And that opening is called the Oral fissure, or in Latin Rima Oris, and that my friends are going
2:45
to be the opening of our digestive pathway. Now. We generally divide the oral cavity into
Division of the Oral Cavity
2:51
two parts. There’s the Oral Vestibule here in green, and the Oral Cavity Proper, here in blue.
2:57
And the dividing line between these two parts are gonna be the teeth and the gums. Alright.
Oral Vestibule
3:03
So again, In this video, we’re mainly gonna focus on the Oral vestibule. And we’re gonna do that
3:08
by going through the structures associated with the external and the internal borders.
3:12
The external borders of the Oral vestibule are going to be the Lips and the cheeks. And the
3:18
internal borders of the oral vestibule are the teeth and the gums. Awesome. So let’s go through
3:23
the anatomy of these, starting with the Lips. Now, the most basic things you need to know
Anatomy of the Lips
3:27
about the anatomy of the lips is that the inner and outer sides of the lips are covered
3:33
by different types of epithelium; there is a transitional zone between the two sides
3:41
The upper lip is attached to the gums through the Frenulum of the upper lip.
3:46
And the lower lip is attached to the gums through the Frenulum of the lower lip.
3:50
And within the mucosa of the lips, you’ll find minor salivary glands called labial glands,
3:56
which continuously produces saliva that lubricates the inner side of the lips. And keep in mind the
4:01
structures we went through earlier; they’re also associated with the upper and lower lips.
4:06
Awesome. Now let’s talk about the cheeks, or the Buccae.
Anatomy of the Cheeks
4:10
The shape of the cheek is formed by the buccinator muscle, which is this one.
4:15
On top of the buccinator muscle, there’s a fascia called the buccopharyngeal fascia,
4:20
which remember covers the buccinator, then goes backwards behind the pharynx.
4:25
On top of the Buccopharyngeal fascia, you’ll find the buccal fat pad (Bichat’s fat pad). The buccal
4:31
fat pas, together with the subcutaneous connective tissue gives the cheek its definitive appearance.
4:38
Now externally to the fat pad, you’ll find all the layers of the skin.
4:43
And on the inner side of the muscle, you’ll find the mucous membrane, or tunica mucosa.
4:49
Now the tunica mucosa of the cheeks, at around this region, you’ll find the opening of the
4:56
parotid duct, which is the duct of the parotid gland as you see here. And around the opening
5:03
of the parotid duct, you’ll find the Papilla of the parotid duct. Which is just gonna be a small
5:08
elevation around where the parotid duct opens into the oral vestibule. And here just to help
5:14
you visualize it. Imaging for a second that this hole is the opening of the parotid duct. And this
5:20
is how the papilla of the oral vestibule looks like. Just some elevations around the opening.
5:25
So that was everything I had for the anatomy of the cheeks.
Anatomy of the Teeth
5:29
Now let’s cover the Inner surface of the oral vestibule and start with the anatomy of the teeth.
5:34
So, let’s take this tooth right here, and pull it out. And then slice the tooth in
5:38
half in order to see the inside as well. The tooth actually have a very straight
5:42
forward anatomical structures despite its comprehensive development. It’s usually divided
5:48
into three regions. First we have the Crown of the tooth, which is the visible part of the tooth.
5:54
Then we have the Root of the tooth which is imbedded in the dental alveolus.
5:58
And between these two parts is a neck, which is the transition between the crown and the root.
6:05
The neck is covered by the gums as you see here. Now. The root of the tooth is fixed inside the
6:12
dental alveolus, right`? And this fixation is supported by something we call periodontium,
6:19
which forms the so called gomphosis, which is a vert strong fibrous connection
6:24
between the root of the tooth and the periosteum on the inner surface of the dental alveolus.
6:29
The gomphosis is a type of joint we call the dentoalveolar joint.
6:35
Within the actual tooth, there’s a cavity. And within the cavity, you’ll find the dental pulp,
6:42
which is a type of loose connective tissue that is rich in neurovascular structures.
6:46
The pulp cavity will continue downwards as the root canal,
6:50
and then at the very bottom of the root, there’s an opening called
6:54
the apical foramen, which is where blood vessels and nerves from enter the tooth.
6:59
Around the pulp cavity, you’ll find the Dentine, which makes up the basic substance of the tooth.
7:06
And at the crown region, the dentine is covered by the enamel,
7:10
which is a very mineralized tissue. And in the region of the neck and the root, you’ll find
7:15
the Cementum lying just superficial to the enamel, which is a calcified structure around the enamel.
7:22
And here’s a little more detailed view of the layers around the root of the tooth.
7:26
First you have the Dentin. Then the Cement around the Dentin. And then around the cementum,
7:32
you’ll find the periodontal ligament. So that’s the general anatomy of the tooth.
7:37
Now. Throughout out lives, we have two different sets of teeth. The first set of teeth are called
7:42
milk teeth, and there’re 20 milk teeth usually. They begin to show up at around 6 months of life,
7:49
and then by the time we’re 24 months old approximately,
7:53
we should have a full set of milk teeth. As we start to grow. The milk teeth are
7:58
gradually starting to fall off between the age of 6-12 years, and they start to get replaced by the
8:04
permanent teeth. The permanent teeth consist of 32 teeth, and the last set of teeth which appear
8:10
at around the age of 17-24 years are called the wisdom teeth. They’re called wisdom teeth because
8:17
they appear later, after all other teeth have appeared. So milk teeth and permanent teeth.
8:23
Now. The arrangement of the teeth are categorized in a specific way. I learned recently that the
Tooth Arrangement
8:30
way we divide the teeth in Europe might differ from the way the teeth are divided in the US,
8:36
so keep in mind that this might differ depending on where your sources are from.
8:41
I study in Europe so I’ll go with that. First, we divide the teeth into four equal
8:48
quadrants. Starting from the midline. The first two teeth from the midline are called the incisor
8:53
teeth. And they get the numbers 1 and 2. So you start counting from 1 at the midline and then 2
8:59
and then 3 and so on. So when I say we have two incisor teeth, I mean we have 8 incisor teeth,
9:05
right? Since you count 2 from midline on both the upper and lower row.
9:11
The Incisor teeth consist of only one root and usually only one root canal. So the 3rd tooth is
9:17
called Canine tooth. Which also contain one root. So we have 4 canine teeth. Then number 4 and 5 are
9:25
called the Premolar teeth, and number 6, 7 and 8 are called Molar teeth. The last one being the
9:31
wisdom tooth. And if you count 8 teeth on each quadrant. So 8 times 4 equals 32, that means that
9:44
we’re looking at the permanent teeth now. Since remember the permanent teeth consists of 32 teeth.
9:49
The milk teeth differ a little bit, but they’re divided in the same way.
9:53
They have 2 incisor teeth. 1 canine teeth and 2 molar teeth. So they don’t have any
9:59
premolar teeth. And that is the main difference between the milk teeth and the permanent teeth.
10:06
And here you see that the incisors and canine teeth usually have one root,
10:10
but the premolar and molar teeth might have more roots as you see here.
Anatomy of the Gums
10:15
Now. Let’s talk about the gums, or the gingiva! From the anatomical point of view,
10:20
the gum is a mucous membrane covering the alveolar processes of the maxilla and
10:25
Mandible. And they form a place for the teeth to be rooted in as you see here. Now, the gums are
10:30
mainly composed of dense fibrous tissue, but the actual consistency of the gums differ depending on
10:37
which region of the gums you’re looking at. From the clinical point of view
10:41
the gum is divided into the alveolar mucous membrane, and the gum proper.
10:46
The alveolar mucosa covers the alveolar processes at the level of the root of the tooth,
10:52
as you see here in blue. This region contains a lot of submucosal connective tissue and is
10:58
therefore mobile. So, it moves if you touch it. The gum proper is the mucosa located at the
11:05
same level of the neck and crown of the tooth, as you see here in yellow.
11:09
The mucosa itself doesn’t have a lot of connective tissue here at the region of the gum proper,
11:14
because it’s attached to the periosteum underneath. That’s why if you try to move the gums
11:19
at around the neck of the tooth, you’ll see that it’s immobile. The gums here don’t move at all.
11:31
Anatomically, you can divide the gums into certain regions.
11:35
The gingival papillae are the projections you see between the necks of the teeth.
11:41
The gingival margin is the elevated margin of the gum around the tooth
11:46
And the gingival sulcus is the groove between the margin of the gum and the tooth
11:52
So that was all I had for the anatomy of the Oral vestibule.
12:00
In the next video, we’ll cover the anatomy of the Oral cavity Proper.