Animal digestion

4 stages of food processing

Ingestion, digestion, absorption, elimination

2 functions of the gastrovascular cavity

Digest food and distribute nutrients

Peristalsis

The involuntary contraction and relaxation of longitudinal and circular muscles throughout the digestive tract

In the oral cavity

salivary amylase + mucin + food = bolus

Volume of saliva produced in a day

1 L

Human accessory glands

Salivary glands, gall bladder, liver, pancreas

Pancreas

Has both endocrine and exocrine functions

Enzymes secreted by the pancreas

Proteases, amylases, lipases, nucleases, bicarbonate

Endocrine function

Acts on distant cells via circulation (secretion of insulin and glucagon in the blood)

Exocrine function

Acts via ducts and channels (secretes digestive enzymes into the duodenum)

Liver

Produces bile

Gall bladder

Stores bile

Bile composition

Bile salts (emulsifiers) and pigments from red blood cells

Enterogastrone

Secreted by the duodenum, slows down digestion by inhibiting peristalsis and acid secretion

Gastrin

Secreted by the stomach, stimulates the production of gastric juices

Secretin

Secreted by the duodenum, stimulates production of sodium bicarbonate

Cholecystokinin

Secreted by the duodenum, stimulates the release of digestive enzymes from the pancreas and bile from the gall bladder

Absorption of nutrients

In the small intestine, by the epithelial cells

Length of the small intestine

6 m

Surface area of small intestine

30-40 m²

Length of colon

1.5 m

3 role of the colon

Reabsorption of water, production of faeces, absorption of vitamins

Inactive form of pepsin

Pepsinogen

Chyme

Gastric juices + partly digested food