Digestion and Absorption Along the Alimentary Canal Flashcards
What is the alimentary canal?
It is a long muscular tube that runs from the mouth to the anus and includes all the organs involved in digestion and absorption of food.
What are the main stages of digestion in the alimentary canal?
Ingestion, digestion (mechanical and chemical), absorption, assimilation, and egestion.
What happens in the mouth during digestion?
Food is broken down physically by the teeth and chemically by salivary amylase in saliva. The tongue rolls the food into a bolus for swallowing.
What is salivary amylase and its function?
It is an enzyme in saliva that begins the chemical digestion of starch by breaking it into smaller sugar chains.
What is peristalsis?
It is a wave-like muscle contraction that pushes food along the oesophagus to the stomach.
What is the function of the epiglottis?
It is a flap-like structure that prevents food from entering the trachea during swallowing.
What happens in the stomach during digestion?
Food is mixed with gastric juice (mucus, pepsin, hydrochloric acid). Proteins begin to be digested by pepsin. The food becomes a semi-liquid called chyme.
What are the contents of gastric juice and their roles?
Mucus: protects the stomach lining.
Hydrochloric acid: kills bacteria and provides acidic pH.
Pepsin: digests proteins into smaller peptides.
What are peptic ulcers and their cause?
Peptic ulcers are sores in the stomach lining caused by the bacterium Helicobacter pylori, not just excess stomach acid.
What is the role of the duodenum?
It receives chyme from the stomach and secretions from the pancreas and gall bladder for further digestion.
What is bile and what does it do?
Bile is a substance produced by the liver, stored in the gall bladder. It emulsifies fats—breaking them into smaller droplets to increase the surface area for enzyme action.
What are the main enzymes in pancreatic juice and their functions?
Amylase: continues starch digestion.
Lipase: breaks down fats into fatty acids and glycerol.
Trypsin: breaks down proteins into polypeptides.
Why is sodium hydrogencarbonate in pancreatic juice important?
It neutralizes the acidic chyme from the stomach, creating an alkaline environment for enzymes to work.
What is the role of the ileum in digestion?
It is the site of absorption where nutrients (glucose, amino acids, fatty acids, glycerol, vitamins, minerals, and water) enter the bloodstream or lymph.
What structures in the ileum aid absorption?
Villi and microvilli increase surface area.
Epithelial cells have mitochondria for active transport.
Capillaries absorb nutrients into the blood.
Lacteals absorb fatty acids and glycerol.
What is the function of the colon (large intestine)?
It reabsorbs water from the remaining undigested food to prevent water loss.
What is stored in the rectum and what is egested?
Faeces (undigested cellulose, bacteria, and cells from the gut wall) are stored and then passed out of the body through the anus.
What is constipation and what causes it?
It is the difficulty in egesting waste caused by low dietary fibre, which can lead to haemorrhoids or even colon cancer.
What is assimilation?
It is the use of absorbed nutrients by body cells for energy, growth, and repair.
How is glucose used in the body after absorption?
Used for respiration.
Excess stored as glycogen in liver/muscles.
Extra converted to fat and stored under the skin or organs.
What happens to amino acids after absorption?
Used for growth, repair, and making hormones/enzymes.
Excess deaminated in the liver and converted to urea.
Some converted to glycogen or fat.
What happens to fatty acids and glycerol after absorption?
Stored under the skin or around organs.
Used to build membranes.
Used for energy in some cases.
What are some key functions of the liver in digestion?
Stores glycogen, vitamins, and minerals.
Breaks down amino acids and toxins.
Produces bile.
Synthesizes plasma proteins.
Breaks down red blood cells.
Produces heat for body temperature regulation.
What causes tooth decay?
Eating sugary foods, especially sweet and sticky foods that remain on the teeth.
What do the acids produced by bacteria do to the teeth?
They destroy the calcium salts in the enamel and then damage the dentine.
How do sugary foods lead to tooth decay?
Bacteria ferment the sugars to produce acids.
What happens when the decay reaches the pulp cavity?
It causes severe toothache and can worsen the cavity.
What serious problem can occur if bacteria reach the pulp cavity?
Bacteria can enter the bloodstream and cause diseases.
