Digestive System Lecture 32

Question 1

Name of gum

Answer 1

Gingiva

Question 2

Structure of enamel

Answer 2

• Crystalline rods or prisms of calcium phosphate & carbonate
• No cells
• Hardest tissue of the body
• No sensation

Question 3

Structure of dentin

Answer 3

• Similar to bone but cells (odontoblasts in specific locations) occur nearby in the pulp instead of scattered through the dentin

Question 4

Structure of pulp

Answer 4

• Soft tissue
• Blood vessels, nerves, lymphatics

Question 5

Structure of cementum

Answer 5

• Calcified connective tissue covering the root

Question 6

Structure of periodontal ligament

Answer 6

• Collagen fibres linking the bone of the socket (alveolar bone) to the cementum
• Rapid turnover
• The ligament’s rapid collagen turnover requires a significant amount of collagen synthesis.

Question 7

What is a co-factor in collagen synthesis?

Answer 7

• Vitamin C is a key co-factor in collagen synthesis.
• Vitamin C is obtained from fresh fruits and vegetables.
• Insufficient Vitamin C leads to impaired collagen synthesis.

Question 8

What is scurvy?

Answer 8

Scurvy results from a deficiency in Vitamin C, leading to improper collagen synthesis.
Without strong collagen synthesis, the periodontal ligament cannot properly anchor the tooth to the socket, leading to loosened teeth and potential tooth loss.

Question 9

What happens with braces?

Answer 9

Braces work by manipulating the properties of the periodontal ligament, specifically through mechanoreceptors.
These mechanoreceptors sense mechanical forces applied by the braces.
The mechanical forces activate osteoblasts and osteoclasts, which remodel the jawbone and realign the teeth.

Question 10

Scurvy

Answer 10

When the periodontal ligament becomes loose and teeth fall out

Question 11

What are the two types of Muscles:

Answer 11

Intrinsic muscles: Responsible for altering the shape of the tongue.
Extrinsic muscles: Move the tongue in various directions but are not covered in this discussion.

Question 12

Answer 12

Question 13

What are the tongue muscles called when they go from anterior to posterior?

Answer 13

Longitudinal muscles (superior top, inferior bottom)

Question 14

Lateral view of tongue

Answer 14

Shows the tongue from the side

Question 15

Superior view of tongue

Answer 15

Looking down on the tongue

Question 16

Longitudinal Muscles

Answer 16

When these muscles contract, they shorten the tongue and retract it backward.

Question 17

Vertical Muscles

Answer 17

These muscles contract vertically, which shortens the distance from top to bottom, flattening the tongue.

Question 18

Transverse Muscles

Answer 18

These muscles run left to right across the tongue. When they contract, they narrow the tongue.

Question 19

Functionality of the tongue muscles

Answer 19

The combination of these muscles allows for the manipulation of the tongue into different shapes, essential for articulation in speech, both verbal and non-verbal.

Question 20

What allows taste perception?

Answer 20

The apical surface (top) of the tongue is textured due to papillae, which play a role in taste perception.

Question 21

Filiform Papillae

Answer 21

Appearance: Sharp, jagged, file-like structures, but they are flexible and bendy rather than rigid.
Function: Provide texture to the tongue but do not have taste buds.
Memory aid: “Fili-“ like “file” to remember their rough texture.

Question 22

Fungiform Papillae

Answer 22

Appearance: Mushroom-shaped, resembling small oyster mushrooms.
Function: Some fungiform papillae have taste buds, but they primarily contribute to texture as well.

Question 23

Vallate Papillae

Answer 23

Appearance: Large, circular structures surrounded by a trench or moat.
Function: These papillae are the main site for taste buds. The taste buds are embedded along the boundary of the moat around the papillae.

Question 24

Taste Perception Pathway

Answer 24

Taste buds located in papillae sense flavors and send signals via cranial nerves.
These signals travel to the medulla, then to the thalamus, and eventually reach the primary gustatory cortex in the brain, where the sensation of taste is perceived.

Answer 25

Answer 26

Answer 27

Question 28

Major salivary glands

Answer 28

• secrete following parasympathetic stimulation induced by seeing, smelling, tasting or thinking about food

Question 29

What are the three pairs of glands?

Answer 29

Parotid gland: Contains only serous cells, which produce a watery secretion rich in enzymes.
Sublingual and submandibular glands: Contain a mixture of serous and mucus cells.
Mucus cells secrete a viscous solution, aiding in lubrication.
These secretions, along with the watery ones, help moisten the oral cavity.

Question 30

How do you get saliva?

Answer 30

Saliva = water + mucus + enzymes

Question 31

What are the enzymes involved?

Answer 31

Amylase (breaks down starchy debris around teeth) and lysozyme (antibacterial)

Question 32

What cells are involved?

Answer 32

Question 33

Digestion

Answer 33

The chemical breakdown of ingested food into absorbable molecules. Requires secretion

Question 34

Absorption

Answer 34

Movement of nutrient, water and electrolytes through the epithelial lining of gut into blood or lymph.

Question 35

Secretion

Answer 35

Saliva: Enzymes (amylase + lysozyme)
Mucus

Question 36

Coiling the Gut

Answer 36

The intestines are highly coiled (gross convolutions), similar to DNA, to increase surface area for absorption.
Gross convolutions refer to the visible coiling of the intestines.

Question 37

Luminal Folds

Answer 37

Circular folds (plicae circularis): Found in the small intestine, these folds increase surface area.
Longitudinal folds (rugae): Found in the stomach, also help to increase surface area, but are distinct from circular folds.

Question 38

Projections into the Lumen

Answer 38

Evaginations (projections): Finger-like projections into the lumen.
Villi: Protrusions found in the small intestine that increase surface area.
Microvilli: Microscopic projections on villi, further increasing the surface area for absorption.

Question 39

Projections Away from the Lumen (Invaginations)

Answer 39

Glands: Invaginations into the surrounding connective tissue.
Examples: Gastric glands in the stomach and intestinal glands in both the small and large intestines.

Question 40

The Element of Time

Answer 40

Time plays a crucial role in digestion and absorption.
If material stays longer in one place, it allows acids, enzymes, and other secretions to act on it effectively.
Rushing material reduces time for digestion and absorption.

Question 41

Mucosa (mucous membrane) consists of

Answer 41

• epithelium, (specialised for protection or absorption or secretion or combinations of all three).
• Ulceration occurs when this layer is breached.
• lamina propria, (a soft fibrous bed of loose connective tissue on which the epithelium rests;
  carries nerves and blood capillaries, populated with defensive cells).
• muscularis mucosae, (two thin layers of smooth muscle, inner circular and outer
  longitudinal). This provides the mucosa with some movement independent of the external
  muscle coat (e.g. contractions squeeze secretions from glands or lymph along lacteals)
  Not involved in peristalsis.

Question 42

Submucosa

Answer 42

A thick bed of loose connective tissue carrying larger blood vessels,
lymphatic vessels and nerves (submucosal plexus). It connects the mucosa to the external muscle
coat, but allows some movement between the two.

Question 43

Muscularis externa (external smooth muscle)

Answer 43

In two layers to produce peristalsis.
The inner layer is circular, the outer is longitudinal. The myenteric nerve plexus occurs between the
layers.

Question 44

Serosa

Answer 44

A slippery outer covering for the gut tube (except oesophagus). It is two-
layered, with outer mesothelium sitting on a bed of connective tissue. The serosa is also known as
the visceral peritoneum (refer lab 1 notes). Where a structure is not in contact with the body cavity,
the outermost connective tissue layer is referred to as the adventitia.
Throughout the length of the gut tube we can recognise four tunics making up the wall. The example
shown below is the small intestine. Other regions of the tube differ principally in the specialised
features of the mucous membrane; the outer three tunics are less variable.

Question 45

Enteric Nervous System

Answer 45

The enteric nervous system is a self-governing branch of the nervous system controlling the gut, influenced by the autonomic nervous system.
Sympathetic nervous system: Generally inhibits gut activities.
Parasympathetic nervous system: Enhances gut activities, such as salivation and digestion (as seen with smelling food).