Digestion

Question 1

What is the function of the oesophagus?

Answer 1

transit

Question 2

What is the function of the stomach?

Answer 2

STORAGE H+/Chemical and physical breakdown

Secretion of intrinsic factor

Question 3

What are the functions of the: Duodenum, Jejunum, and Ileum?

Answer 3

• Fat, protein, carbohydrate digestion & absorption
• Water and electrolyte abs.
• Bile salt transport vitamin B12 absorption

Question 4

What are the functions of the colon, rectum and anus?

Answer 4

-STORAGE / water and
electrolyte transport
-Defecation

Question 5

What does the mucous secrete?

Answer 5

alkaline mucus (glycoprotein) protects lining (epithelium) against the acidity

Question 6

What do the parietal cells secrete?

Answer 6

• gastric acid (HCI)

- intrinsic factor (glycoprotein for absorption of B12)

Question 7

What do the Enterochromaffin cells secrete?

Answer 7

histamine, stimulate the parietal cells to produce gastric acid

Question 8

What do the chief cells secrete?

Answer 8

• Pepsin (proteins → peptides)

- gastric lipase (lipid hydrolysis)

Question 9

What do the D- cells secrete?

Answer 9

Somatostatin: inhibit gastric acid, effects cell proliferation

Question 10

What do the G- cells secrete?

Answer 10

Gastrin, stimulate parietal cells to secrete gastric acid and chief cells - pepsinogen

Question 11

What is the main function of the stomach?

Answer 11

mechanical and chemical breakdown of food into small particles.

Question 12

What is the function of the mucus secreting cells?

Answer 12

-provide protection against gastric acid

Question 13

What is the function of the parietal cells?

Answer 13

Secrete HCI; intrinsic factor that binds ingested vitamin B12 and enables it to be absorbed by the small intestine. THIS IS ONLY ESSENTIAL FUNCTION OF STOMACH

Question 14

What is the main function of the endocrine cells (G, D and ECL CELLS)?

Answer 14

Secrete hormones into the blood stream.

Question 15

What do the stomachs of newborn infants produce?

Answer 15

RENNIN and GASTRIC LIPASE, which are absent in adult

Question 16

What is the STRESS RELAXATION

or PLASTICITY. (Laplace’s law)?

Answer 16

Stomach expands as it fills but tension
in muscle cells re-adjusts to maintain a
normal level of contraction

Question 17

What is segmentation?

Answer 17

Facilitates mixing of contents thereby aiding absorption

Question 18

What does myogenic not need input from?

Answer 18

Does not require any input from nerves

Question 19

What does neurogenic need input from?

Answer 19

Requires input from local intrinsic nerves

Question 20

What is peristalsis?

Answer 20

Distension of GI wall induces contraction behind and relaxation in front leading to forward movement of contents.
Over short range (XX cm)

Question 21

What are inherent properties of GI tract?

Answer 21

Segmentation and peristalsis

Question 22

What is myogenic and what is neurogenic?

Answer 22

Segementation is myogenic and peristalsis is neurogenic

Question 23

What can both segmentation and peristalsis be influenced by?

Answer 23

External autonomic and hormonal effects.

Question 24

Where does mass peristalsis occur and what does it do?

Answer 24

-Occurs predominantly in the large intestine. Moves contents over longer distances triggering defecation reflex. Triggered by arrival of food in Stomach

Question 25

What are 'housekeeper' contractions?

Answer 25

The fasting state segmentation stops and waves of long-range contractions sweep through the GI tract.

Question 26

Why is giving saline counter productive to the ORT (Oral rehydration therapy)?

Answer 26

Na+ can’t be absorbed therefore neither can water: More Na+ in lumen increases osmotic pressure further resulting in more water loss

Question 27

Why is adding glucose productive to ORT?

Answer 27

Add glucose to the solution and a new mechanism operates. Glucose can still be absorbed. Glucose enters by a Na+ co-transporter. Equimolar amounts of glucose and Na+ taken up. Restores osmotic gradient and H20

Question 28

How do amino acids, di and tri peptides enter the ORT?

Answer 28

by co-transporters providing potential for co-transporters

Question 29

What is the first line of defence in the gut?

Answer 29

mucous layer on top of epithelia; acts as a barrier to acid and peptides. Also traps bicarbonate secreted by epithelial cells, helps neutralise aicd

Question 30

How is penetrating acid detected?

Answer 30

detected by chemosensory neurons results in secretion of NO, CGRP and VIP which cause vasodilation ►► aids removal of acid

Question 31

What is restitution?

Answer 31

``` rapid movement of neighbouring cells to cover damaged Epithelia (~30 mins). Cells not functional until replaced by new correctly differentiated cells. Growth Factors (ie. EGF) and trefoil proteins aid repair process. ```

Question 32

What is Prostoglandin E2?

Answer 32

Multi-factorial: Enhances mucus and bicarbonate secretions, also increased gastric blood flow. However, (+ve) effects are inhibited by non-steroidal anti-inflammatory drugs (Asprin, Ibuprophen etc)

Question 33

What all decrease acid production?

Answer 33

Noradrenalin, CCK. VIP and CGRP

Question 34

What cells does acid induce and what is secreted?

Answer 34

Acid induces D cells to secret somatostatin which inhibits gastrin secretion which in turn inhibits acid production

Question 35

What does secretions from pancreatict duct do?

Answer 35

Secretions from pancreatict duct cells very alkaline, helps balance corrosive effects of chyme in duodenum.