Anatomy and Physiology of the Gastrointestinal System

Question 1

What is digestion?

Answer 1

Produced nutrients absorbed into bloodstream and distributed around the body.

Question 2

What role does the mouth play in digestion?

Answer 2

Tongue helps with chewing (mastification). Saliva starts process of food digestion. Helps lubricate food and keep mouth clean and moist. Tongue rolls food into bolus. During swallowing, tongue rises, pushing bolus into pharynx. Soft palate moves up, preventing bolus entering naval cavity. Epiglottis also lowers to cover opening to trachea.

Question 3

What role does the oesophagus play in digestion?

Answer 3

Bolus enters oesophagus. Wall of oesophagus contains circular and longitudinal muslces. Circular muscles behind bolus contract and longitudinal muscles relax. Muscles in front of bolus act in opposite way. Actions cause bolus to move from oesophagus to stomach. Actions causes peristalsis.

Question 4

What role does the liver play in digestion?

Answer 4

Bile synthesised in liver, stored in gall bladder. Contains water, mineral salts, mucus, bile pigments (mainly bilirubin), bile salts, and cholesterol. Help with fat digestion. Bile salts increase absorption of cholesterol and fatty acids. Fat soluble minerals (A, D, E, K) more readily absorbed. Bilirubin produced when ageing red blood cells break down - excreted via faeces in bile - excess in blood causes yellow disclouration (jaundice)

Question 5

What are the 2 main functions of the pancreas?

Answer 5

1. produce pancreatic juice containing enzymes - digest proteins, carbs and fats
2. secrete hormone insulin and glucagon to control blood glucose level.

Question 6

What role does the stomach play in digestion?

Answer 6

Food enters stomach through oesophageal sphincter - then closes to prevent contents travelling back up. Process of digestion starts in stomach, producing chyme which passes into small intestine through pyloric sphincter. Water, alcohol, and few specific drugs are absorbed in the stomach. Stomach muscles churn food and mechanically break it down. Food mixes with gastric juices to begin chemical breakdown.

Question 7

What do gastric juices contain?

Answer 7

1. water (liquify food)
2. hydrochloric acid (creates acidic environment to kill microbes on food)
3. pepsins (break down protein. Only work in acidic environment of stomach)

Question 8

What are the main features of the large intestine?

Answer 8

1. Absorption
2. Mass movement
3. Defaecation

Question 9

What role does the small intestine play in digestion?

Answer 9

Chyme enters duodenum from stomach and travel through jejunum and ileum by peristalsis before moving into large intestine. Small intestine main site of absorption of nutrients from foods. Villi and microvilli project into lumen of small intestine and greatly increase surface area for absorption of nutrients. Acid chyme from stomach moves into small intestine where it mixes with pancreatic juices, bile and intestinal juices - digestion of nutrients is complete.

Question 10

What enzyme is used for the digestion of proteins?

Answer 10

Peptidases (secreted by pancreas) break down proteins into smaller peptides and amino acids.

Question 11

What enzyme is used for the digestion of carbohydrates?

Answer 11

Amylase (secreted by pancreas) converts startches into disaccharides.

Question 12

What enzyme is used for the digestion of fats?>

Answer 12

Lipase converts fats into fatty acids and glycerol. Bile aids digestion of fats.