The Digestive System

Outline some ways in which the diet can affect the functioning of the intestines.

Larger meals push through into the intestines much quicker while high protein meals or high concentration meals have a slow digestion rate. Alcohol and caffeine can stimulate movements of the stomach.

Describe the mechanical and chemical digestion that occurs in the stomach.

Mechanical digestion consists of kneading the chyme and churning it up, the chemical digestion is gastric juice, containing hydrochloric acid, mucus and digestive enzymes.

Distinguish between mechanical and chemical digestion

Mechanical digestion is digestion that physically alters the food by breaking it down into smaller pieces. Chemical digestion is the altering of the chemical makeup of the food.

Describe peristalsis and the role played by the circular and longitudinal muscles.

Peristalsis is a wave of contraction that move the food along the alimentary canal. Circular muscle are the ones that allow for peristalsis to occur. Longitudinal muscles occur in the stomach along with circular to allow 2 directions of contraction

Describe the mechanical and chemical digestion that occurs within the mouth.

The mechanical digestion is chewing and making the food smaller and into more manageable pieces increasing SA. The chemical digestion come from the salivary glands and begins to digest starch.

List the ways in which the surface area of the small intestine is maximised for absorption.

There are a number of folds around the circumference increasing surface area, there are villi that are 1mm long that increase SA and on them there are micro-villi that further increase SA.

Describe the mechanical and chemical digestion that occurs in the small intestine.

There is no physical digestion, the chemical digestion is; pancreatic amylase which breaks down starch, trypsin spilts proteins into much smaller units, pancreatic lipase are enzymes that break down fats into fatty acids and glycerol.

Outline the functions of the large intestine

To reabsorb water, absorb vitamins and mineral nutrients.

Describe the structure of a villus and explain how this structure makes the villus ideally suited to its function.

Within the villi there are blood vessels and a lymph vessel called a lacteal. Water and water-soluable vitamins are absorbed into the blood capillaries by diffusion. Glucose & amino acids are absorbed through active transport. Fatty acids and glycerol are absorbed by simple diffusion into the lacteal, the fat droplets recombine back in the lacteal.

Define digestion

All metabolic processes that take place within cells.

Describe the structure, giving the basic chemical makeup and the names of each monomer, of carbohydrates, proteins and lipids.

Carbohydrates have C,H,O with a 2:1 ratio of H to O. Protein C,H,O,N. Fats are C,H,O

Distinguish between elimination and excretion.

Elimination is the removal of non-digestible waste from the body, excretion is the removal of waste from digestion.

Describe the types, numbers and functions of teeth.

Four incisors, used for bitting and cutting, two canines, used for tearing. Four premolars, and six molars, crushing and grinding food.

List the 6 basic actives of digestion.

Ingestion of food and water Mechanical digestion of food Chemical digestion of food Movement of food along the alimentary canal Absorption of digested food Elimination of material that is not absorbed.

List the digestive enzymes (amylase, protease, lipase) produced by the salivary glands, stomach, pancreas and small intestine, give the substrate they act on and the products formed.

Salivary Gland: Salivary Amylase - Breaks down starches (polysaccharides) into disaccharides. Disaccharides are then broken down into polysaccharides by pancreatic amylase. Stomach: Pepsin (from pepsinogen) - Breaks down proteins into large peptides. Small Intestine (from pancreas): Pancreatic Amylase - Continues the breakdown of starch from disaccharides to monosaccharides. Intestinal protease - Continues the breakdown of protein from dipeptides to amino acids. Lipase - Breaks down fat.

List the key nutrients in food and I've the basic function of each

Simple Sugars - They are major sources of energy for cells. Amino Acids - They are the building blocks for proteins. Fatty Acids - They are necessary to make vital fats for normal body functions. Vitamins - Small organic molecules that do not provide any energy but are essential for cells to gain energy from carbohydrates. Minerals - They are essential for the normal functioning of human cells. Water - The body needs fluid to survive as two thirds of bodies are water, they replenish fluids.

Define absorption

Take in or soak up (energy or a liquid or other substance) by chemical or physical action.

Describe the relationship between the alimentary canal and the digestive system.

The alimentary canal is the continuous tube that run from the mouth to the anus.