Chapter 9- Digestion Flashcards
what are the 6 basic functions of the digestive system?
- ingestion of food and water
- mechanical digestion of food
- chemical digestion of food
- movement of food along the alimentary canal
- absorption of digested food and water into the blood and lymph
- elimination of material that is not absorbed
what is the function of the digestive system?
to extract nutrients from the food we consume, transport them via blood to cells and then absorbed by cells for use in chemical reactions
what happens at the mouth?
intake of food (ingestion)- the action of the jaw and teeth begins mechanical digestion where food is broken up into smaller pieces
what are the 3 pairs of salivary glands?
parotid salivary (front of ear), sublingual salivary (under the tongue), submandibular salivary (deep in the mouth)
what kinds of teeth do we have and how many?
4 incisors, 2 canines, 4 premolars, 6 molars
what are the functions of incisors?
biting and cutting
what are the functions of canines?
tearing
what are the functions of premolars?
tear and crush food
what are the functions of molars?
crushing and grinding food
what is the function of the oesophagus?
pushes food from the mouth to the stomach by a wave of circular muscular contractions called peristalsis- the mucus prevents friction
what kind of muscle surrounds the oesophagus?
circular muscle
what is the stomach?
a muscular organ located on the left side of the upper abdomen- it secretes acid and enzymes that digest food
how is mechanical digestion achieved in the stomach wall?
waves of muscular contraction that move along the stomach wall- the muscle has an oblique muscle layer as well as a circular and longitudinal layer
what is the thick, soapy liquid the stomach converts food into called?
chyme
what is mucosa?
the lining of the stomach
what is gastric juice?
a digestive juice that is responsible for chemical digestion in the stomach
what is the thick, circular muscle that results in constriction?
pyloric sphincter
what is the small intestine?
the longest part of the alimentary canal; receives material from the stomach (6m long)
what is the first part of the small intestine called?
duodenum
what is intestinal juice?
the digestive juice secreted by the glands of the small intestine
what is pancreatic juice?
the liquid secreted by the pancreas
what is bile?
a secretion of the liver, stored in the gallbladder and released into the small intestine
what is pancreatic amylase?
an enzyme in pancreatic juice that breaks down starch
what is trypsin?
an enzyme in pancreatic juice that breaks down protein
what is ribonuclease?
an enzyme in pancreatic juice that digests RNA
what is deoxyribonuclease?
an enzyme in pancreatic juice which digests DNA
what are pancreatic lipases?
an enzyme in pancreatic juice which breaks down fats
what are bile salts?
substances that break fats into tiny droplets
what is lacteal?
a lymph capillary in the small intestine which absorbs fat from digested food
what is the large intestine?
the part of the intestine between the small intestine and the anus; it is made up of caecum, colon and rectum
how long does it usually take for the material to pass through the large intestine?
18-24 hours
what is faeces?
material passed out of the rectum
what is excretion?
the removal of metabolic wastes- waste that has been produced by chemical activity of the body cells
what is mucosa?
a mucous membrane; in this case the membrane that forms the internal lining of the alimentary canal
what are villi?
projections from the internal lining of the small intestine
what are microvilli?
microscopic projections from the membranes of cells lining the small intestine- increase the surface area for absorption
what is mechanical digestion?
the mechanical breakdown of food into smaller particles ie chewing food
what is chemical digestion?
the chemical breakdown of food into smaller molecules ie enzymes and acids breaking down food
what enzymes break down carbohydrates?
carbohydrase and amylase
what are proteins?
very large organic molecules made up of amino acids
what are lipids?
large organic molecules made up of fatty acids and glycerol
how does the diet affect the digestive system?
a healthier diet can increase blood flow and metabolism for a smoother digestion- healthier foods improve the digestive tract and prevent sicknesses and diseases (ie constipation)
why is fibre so important in terms of digestion?
both soluble and insoluble fibre are found in foods derived from plants- contains pectins, gums and mucilage- links to lower cholesterol levels in the blood, decreased risk of heart disease or cancer and beneficial effects on blood glucose levels- decreased fat absorption
what is constipation?
a condition where water from the faeces is absorbed making it hard and dry- resulting in difficulty carrying out bowel movements- can be caused by lack of roughage in diet (cellulose)
what is diarrhoea?
frequent defecation of watery faeces- caused by irritation of the small or large intestine- can be a result of a bacterial or viral infection, food poisoning, etc
what is bowel cancer?
or colorectal cancer is uncontrolled growth of cells in the wall of the large intestine- can be linked to an unhealthy diet, high alcohol consumption, smoking, obesity etc
what is coeliac disease?
a condition where gluten is intolerable- immune system responds by damaging or destroying villi in the small intestine- without healthy villi, nutrients cannot be absorbed and the person can become malnourished
what is peristalsis?
the muscular contractions that occur within and surround both the intestines to force food throughout the system- waves of contraction
