digestive system including liver anatomy and physiology

Question 1

what is he function of the gi tract

Answer 1

• motility - propels ingested food from mouth to rectum
• secretion - aids in the ingestion and absorption of food
• digestion - chemical and mechanical break down of food into absorbal units
• absorption - active or passive transfer of substances from lumen to the ECF

Question 2

what are the two ways the gi smooth muscles contract

Answer 2

• segmentation contractions = the propulsion of food-
  where it moves food from the gut to the anus in contraction and relaxing waves along the gut - this unusually occurs in the esophagus and small intestine
• segmentation contraction. = non propulsive, the mixing of food
  it aids digestion by mixing the food sna d helps to keep it in contact with the epithelium
  they have circular and longitudinal muscle contractions . this dominates in the gut
  there is no net forward motion

Question 3

what substances are secreted

Answer 3

enzymes will be secreted by the exocrine glands - such as the salivary glands and pancreas enzymes. as well as epithelia cells in the muscosa of the stomach

mucus is alos sec rested by the mucous cells in the stomach, and goblet cellls in the small intestine

water and electrolytes are also secreted by the gi epithelia cells

Question 4

what types of substances are digested at each site.

Answer 4

• mouth = starch
• stomach = proteins
• small intestine = proteins, starch and fats
• large intestine = fermentation of carbohydrates and proteins by bacteria.

Question 5

what are the reflex action involved in swallowing

Answer 5

• closure of epiglottis
• opening of upper esophageal sphincter
• peristaltic wave down the esophagus
• opening of lower esophageal sphincter.

Question 6

what is the fu cation of the esophagus

Answer 6

• secretes mucus
  moves food from the throuat to the stomach using peristaltic movement
• if acid goes there it causes heart burn

Question 7

what is the function of the stomach

Answer 7

• stores food eaten and breaks it down into tiny pieces
• mixes food with digestive juices with enzymes to break it down
• ## add to kill bacteria

Question 8

what is the function of the small intestine

Answer 8

• they hav villi to increase surface area
• the villi are covered in microvilli to further increase surface area
• nutrients pass through small intestine walls into blood
• they absorb 80% water, vitamins, minerals, carbohydrates, proteins and lipids

Question 9

what is the structure of the walls in the gi tract

Answer 9

• gastric pits
• mucosa
• neck cells - secrete mucus
• chief cells - secrete pepsinogen ( this is secreted into the enzyme pepsin - this breaks down proteins into polypeptides)
• parietal cells - secrete acid
• gastric glands

Question 10

what triggers the neural and hormone response to the gastric phase ( this is once the food has been eaten and reached the stomach)

Answer 10

neural response -
- triggered b y stretch and chemoreceptors
- stimulates partitas and chief cell secretion which will stimulate gastric acid and pepsinogen
- stimulates mixing waves - segmentation contractions

hormonal response - enteroendocrine cell response

• gastric release from G cells, triggered by the neuronal activity and chyme peptides
• histamine is released by mast cells which is triggered by stretch

Question 11

what is neural and normal response to the intestinal phase

Answer 11

neuronal response
- stimulates updated by increase acid level in the first part of the small intestine
- suppresses gastric acid secretion
- decreases gastric acid motility

hormonal response
- I cells in the small intestine secrete CHOLECYTOKINN ( CCK), GASTRIC INHIBITATORY PEPTIDE (GIP) this is triggered by the lipids in the food.
- the hormone secretin is released due to the drop in ph to les than 4.5
- gastrin is also triggered by partially ingested food