Digestion Flashcards
Explain mechanical digestion
This takes place in the mouth where solid foods are torn apart, ground, shaken, mixed with juices to be dissolved, and prepared for chemical digestion.
Explain chemical digestion
This involves mainly enzymes as well as the secretion of acids in the stomach to breakdown food.
describe the phase of digestion that takes place in the mouth
teeth and jaws crush and grid food into smaller particles. Here it will mix with saliva, which contains enzymes and antibodies that kill harmful bacteria, and also amylase, an enzyme that starts the breakdown of carbohydrate into smaller, more usable, simple sugar molecules.
describe the phase of digestion that occurs during swallowing
Food is then swallowed as a bolus or ball, and travels down the oesophagus, the tube that connects the mouth to the stomach. The symmetrical muscular contractions, known as peristalsis, ensure that the bolus travels toward the stomach and prevent it re-entering the mouth.
describe the phase of digestion that occurs in the stomach
Once the food bolus reaches the stomach, movement of the smooth muscular walls churns it into chyme. The enzyme pepsin is released and mixed with the chyme to begin the breakdown of protein; the addition of hydrochloric acid into the mix provides an ideal environment for the pepsin to work, and also kills any bacteria.
describe the phase of digestion that occurs in the small intestine
From the stomach the chime passes into three segments within the small intestine, the first being the duodenum where the macronutrients are broken down. Here the enzymes disaccharidase and amylase complete the breakdown of carbohydrates, and pepsin the breakdown of protein. The breakdown of triglycerides (fats) also begins through the release of lipase. The absorption of nutrients begins in the second segment of the small intestine, the jejunum. This has a huge surface area, with a deeply folded inner surface covered with finger-like projections known as villi. These make the jejunum extremely effective at absorbing nutrients. As fat does not mix as well into the chyme mixture as other nutrients, it is emulsified, or separated, by bile to help with absorption. Finally in the third segment, the ileum, the digestion and absorption.
describe the phase of digestion that occurs in the large intestine
What remains of the chime then moves into the large intestine. Here water continues to be reabsorbed but no further digestion takes place.
how is the mouth relevant to digestion?
Forms the start of the alimentary canal. Also known as the gastrointestinal (GI) tract, this is a flexible tube measuring about 8m long in adults. It starts in the mouth and travels through the oesophagus, stomach, small intestine, large intestine and rectum.
what is the oesophagus
The oesophagus: A muscular tube connecting the mouth.
what is the liver and how is it relevant to digestion?
The second largest organ in the body after the skin weighing 1.4kg. To filter blood coming from the digestive tract and remove any toxic substances such as alcohol or drugs. To store carbohydrates as glycogen, and release them as glucose to supply the brain or top up blood sugar levels when required. To secrete bile which is involved in breaking down fat. To produce protein components involved in blood clotting. To provide a storage point for many vitamins and mineral
what is the stomach and how is it relevant to digestion?
A large musclar sac 15-25cm long, with a smooth musclar walls and sphinters at each end to ensure food travels in one direction.
what is the gall bladder?
A storage sac located beneath the liver.
what is the pancreas and how is it relevant to digestion?
A large gland located behind and underneath the stomach. Rich in enzymes that break down fats, carbohydrates and proteins, and also releases sodium bicarbonate that neutralises stomach acid. It is also responsible for the production of insulin and glucagon, the two hormones that regulate blood sugar levels.minerals
what is the large intestine?
A 1.5 metre long diameter tube that follows on from the small intestine.
what is the small intestine?
This is divided into three functionally different segments, the duodenum, jejunum and ileum.
