Digestion 1: Tooth and gut

Question 1

What are the layers of the tooth from out to in (root and crown)

Answer 1

Root: Periodontal ligament, Cementum, Dentin, Pulp
Crown: Enamel, Dentin, Pulp

Question 2

What is the structure, cells, and function of enamel

Answer 2

• Cystalline rods or prisms of CaP & carbonate making it the hardest tissue in the body
• Has no cells and nerves so lacks sensation and cannot be replaced in adulthood
• in the crown only

Question 3

What is the structure, cells and function of Dentin

Answer 3

This is a calcified connective tissue with higher hydroxyapatite content that gives tooth it’s shape.
- Has odontoblasts that are not scattered throughout but near to the pulp.

Question 4

What is the structure, cells and function of Pulp

Answer 4

This is the soft tissue that contains the bv, nerves and lymphatics.
- These nerves contain mechanoreceptors that monitor how much force is on the tooth and stops the tooth getting damaged from excessive force

Question 5

What is the structure, cells and function of Cementum and Periodontal ligament

Answer 5

The periodontal ligament has a large SA to secure the tooth root to the bone of the socket (alveolar bone) by attaching collagen fibres to the cementum.
- This has a very fast turnover.

Cementum is a calcified connective tissue covering the root of tooth.

Question 6

What is the effect of vit C deficiency on teeth health

Answer 6

Vit c needed for synthesis of collagen so periodontal ligament rapid turnover not supported and teeth fall out.

Question 7

What are the 3 papillae of the tongue

Answer 7

They are projections of the lamina propria

1. Fungiform - mushroom with 5 tastebuds each
2. Filiform - entire surface- no tastebuds but tactile receptors that increase friction
3. Valate - big, has moat and the most tastebuds, back of the tongue

Question 8

Describe the 3 intrinsic muscles of the tongue

Answer 8

1. Longitudinal muscles cause shortening length of the tongue
2. The vertical muscles cause flattening of the tongue
3. the horizontal/ transverse muscles cause narrowing of the diameter of the tongue

Question 9

What / Where are the 3 major salivary glands and which secretory cells do they have

Answer 9

1. Parotid : under the ear -Serous cells
2. Submandibular : mouth floor- mixed mucous and serous
3. Sublingual : underneath tongue: mostly mucous

Question 10

Compare the composition and function of the serous cells secretion vs mucous cells secretion

Answer 10

Serous cells have dark staining granules of watery, enzyme rich secretion.
-Enzymes Amylase breaks down starchy debris around teeth and Lysozome kills bacteria

Whereas Mucous cells secrete a light staining viscous secretion which lubricates the food bolus.

Question 11

What is the overall composition of saliva and what is the nerve stimulation for saliva secretion

Answer 11

Composition: water + mucus + enzymes

Stimulated by parasympathetic ANS by seeing, smelling, thinking about food

Question 12

What are the 4 key roles of organs in the digestive system and where do they vary in along the gut tube

Answer 12

1. Digestion = chemical breakdown of ingested food into absorbable molecules. In the mouth, stomach, duodenum and small intestine. cecum by bacteria
2. Absorption= movement of nutrients from gut to blood/lymph. In the stomach (water ions drugs) DJ Ilieum, (majority) and large intestine
3. Secretion: saliva etc occurs along entire GI tract
4. Transport to do 1 and 2. occurs along entire GI tract

Question 13

What are the 5 ways that secretion and transport occurring in the gut epithelium is increased by increasing SA ( from biggest to smallest modification)

Answer 13

1. Gross convolution: twisting to fit more tube in the same space
2. Luminal folds : Large circular folds, in intestines as plicae circularis or longitudinal rugae in stomach (core of submucosa, covering mucosa)
3. Projections toward the lumen (ie villus- core of lamina propria covering epithelium- microvilli core of cytoplasm)
4. Projections away from the lumen (ie glands)
5. Having more time: increases the amount of food can absorb

Question 14

List the 4 layers of the gut tunic from the lumen to deep

Answer 14

1. Mucosa (mucous membrane
2. Submucosa
3. Muscularis externa (external smooth muscle)
4. Serosa (visceral peritoneum or adventitia)

Question 15

Describe the tissue component and function of Mucosa

Answer 15

1. Closest to the lumen is the epithelium for (secretion, absorption and/or protection)
2. Underneath is the Lamina Propria: a soft bed of loose connective tissue that carries nerves, capillaries and have defense cells.
3. Muscularis Mucosa: double layered smooth muscle (inner circular, outer longitudinal) that provides independent movement of mucosa from the external muscle coat.

Question 16

Describe the tissue component and function of Submucosa

Answer 16

This is a Thick bed of loose connective tissue that carries larger bv, lymphatic vessels and nerves (eg. submucosal plexus for mucose and submucosa).
Function is to connect the mucosa to external muscle but allows some movement between the two.

Question 17

Describe the tissue component and function of Muscularis externa

Answer 17

Two layers of smooth muscle :
1. An inner layer of circular muscle
2. an outer layer of longitudinal muscle
Work together to produce peristalsis and coordinated by the myenteric nerve plexus that occurs between the two muscle layers

Question 18

What Nervous system controls the plexes in the 4 layers of the gut tube and what are its interactions with the ANS

Answer 18

The enteric nervous system controls the submucosal and myenteric nerve plexus and is stimuated by the parasympathetic nerve system of the ANS and inhibited by the sympathetic nerve system

Question 19

Describe the tissue component and function of Serosa

Answer 19

This is the slippery outer covering of the gut tube made of connective tissue and then outermost layer of mesothelial cells that secrete serous fluid. (visceral peritoneum) if the structure is in contact with the body cavity.
For the oesophagus, the outermost connective tissue layer is the adventitia (organ next to organ).