Nutrient Exchange in Animals Flashcards
What are the four stages of nutrient absorption in humans?
- Ingestion
- Digestion
- Absorption
- Elimination.
State the function of the mouth in the digestive system.
Food breaks down with chewing and saliva, which has digestive enzymes and is secreted by salivary glands around the mouth.
State the function of the oesophagus in the digestive system.
It is a tube like organ for transportation. it has skeletal and smooth muscle tissue that produces wave-like contractions called peristalsis that moves food to the stomach.
State the function of the stomach in the digestive system.
It receives food and stores it for up to five hours. its walls have three layers of muscle tissue that mix and grind food into smaller particles, increasing the surface area to volume ratio for decomposition by gastric juice.
State what gastric juice is and its function
It is a mixture of water, hydrochloric acid, mineral ions and pepsin (digestive enzyme) secreted by epithelial cells lining the stomach. Its function is to break down food into a liquid called chyme which is transferred to the small intestine.
State the liver’s function in the digestive system
Produces an alkaline material called bile that is secreted into the small intestine. It increases the small intestine’s pH to support digestive enzymes and aids absorption of fat.
State the function of the pancreas in the digestive system
secretes enzymes into the small intestine that break down proteins, fats and carbohydrates for blood absorption
State the function of the gall bladder in the digestive system
holds bile before transportation to the small intestine
What is peristalsis?
the constriction and relaxation of the muscles which creates wave-like movements that push the contents forward.
What happens in the small intestine?
Nutrient absorption occurs here. chyme enters from the stomach and moves through the lumen (interior) by peristalsis, while nutrients are absorbed as it moves over the surface of the small intestine.
Describe the structure of villi.
Each villus is lined with a thin layer of epithelial cells called enterocytes that absorb nutrients from food. They have a specialised cell membrane called a brush border containing up to 1000 microvilli.
What is the purpose of the enterocytes’ brush border?
The microvilli increase the surface area to volume ratio.
Describe the role of the large intestine in the digestion system.
Any undigested material is moved into it, where water and salts are reabsorbed. the remaining material is excreted by defacation.
what do digestive enzymes do?
They break down macromolecules including proteins, polysaccharides and lipids into smaller nutrients that are absorbed into the blood through the enterocyte brush border.
What does peptidase do?
breaks down proteins into amino acids
