Gastro-intestinal Tract

Question 1

List main functions of digestive system

Answer 1

The main function is to break down foods until small enough to be absorbed through gut wall into blood so nutrients are utilised and get rid of waste eg cholesterol, absorb water and synthesise vitamins.

Question 2

Describe structure and functions of organs in digestive tract

Answer 2

GI Tract: has sphincters which stop acid coming up and divides tube to allow each to complete its function, many layers adventitia(peritoneum) smooth muscle layers not voluntary sub mucosal plexus network of nerves, epithelium mucous membrane. Has goblet cells that release mucous protection from eating and drinking and to stop tract from digesting itself. Movement three ways peristalsis (moves food forward) segmentation (contracts at various points to break food into bits) mass flow ( rapid movement forward near rectum).

Peritoneum: a serous membrane sac that holds organs in place contains infection and reduces friction of organs as it acts as a lubricant and friction can cause inflammation.

Question 3

List main functions of liver with reference to bile secretion

Answer 3

Produces bile that is used to emulsify fats, the liver cells have receptors that detect whether blood glucose levels is too high or too low. Main functions to detoxify substances eg ethanol (alcohol) to undergo deamination of amine from amino acids.

Question 4

Describe the structure of carbohydrates, proteins and lipids and function in body

Question 5

Discuss the digestion of carbohydrates, proteins and fats with reference to relevant organs and enzymes

Question 6

Discuss excretion of waste to include physiology of defecation

Answer 6

Gut has healthy microbes (bacteria) produce vitamins and orevent disease, greater numbers in colon and play role in our health. Infants gut is sterile but gains bacteria when passing mother’s vagina (c-section babies have reduced initially). Faeces temporarily stored in colon and moved 1-2 times daily to rectum when rectum fills it alerts us to defecate.
Anus: two sphincters internal (involuntary) external (voluntary) internal allows stool to pass through rectum to anus external we find a toilet to defecate.

Question 7

Describe structure and functions of organs in digestive tract pt 2

Answer 7

Mouth: mastication (chewing) break down of food with teeth saliva and tongue, hard palate anterior soft posterior, digestive enzymes released from saliva (amylase) also saliva maintains oral hygiene and lubricates food bolus. Tongue needed for delgutition (swallowing) anchored to floor by frenulum covered in papillae contain taste buds.

Pharynx: 3 sections naso(nose to throat)-,oro-(back of throat), laryngo(further down to stomach)-pharynx from oral to oesophagus via pharynx.

Oesophagus: rapid transport of bolus to stomach through pharynx from pharynx to stomach.

Sphincters: thick circular rings of muscle keep GI a one way system.

Question 8

Describe structure and functions of organs in digestive tract pt 3

Answer 8

Stomach: storage facility, produce chyme (from gastric juice and bolus), physical and chemical breakdown. Three muscle layers to churn food, diff directions to help churn, mucous membrane in folds (rugged) enabling it to stretch when need be. Stomach produces gastric juice this activates pepsinogen to pepsin to break down proteins. Chyme is acidic very conc.

Duodenum: first part of small intestine c shaped curve chyme neutralised here water enters through gut to neutralise.

Liver: composed of hepatocytes produces bile synthesis of proteins detoxifies blood energy storage.

Gallbladder: connected liver above it and duodenum below stores and concentrates bile contracts when fat detected in duodenum releasing bile into duodenum.

Question 9

Describe structure and functions of organs in digestive tract pt 4

Answer 9

Bile: contains salts emulsifies fats into small droplets allows absorption of cholesterol and fatty acids.

Pancreas: endocrine function insulin/glucagon, exocrine, pancreatic juice contains enzymes for digestion (trypsinogen inactive initially to not digest GI tract walls).

Jejunum: next section of small intestine after duodenum. Secretion of alkaline intestinal juice, final digestion, nutrient absorption.

Ileum: last section of small intestine. Water/electrolyte absorption.

Large intestine: caecum, colon (ascending, transverse, descending, sigmoid) rectum, anal canal. Final water/electrolyte absorption temporary storage secretes mucous to lubricate waste moving.

Caecum: wide pouch acts as storage once full waste moves along large intestine (allowing large stools).

Rectum: defecation