chapter 9 Flashcards
function of digestive system
extract nutrients from food we eat and transport them via blood to the cells where there are absorbed and used in chemical reactions
the mouth
mechanical:
jaw and teeth cut, tear, crush and grind food
tongue mixes it up with mucus into a round lump called bolus
chemical:
salivary amylase ptyalin begins starch breakdown
salivary glands
3 types, 2 of each
- parotid salivary gained (front of ear)
- sublingual salivary gland (under the tongue)
- sub mandibular salivary gland (under mandible bone)
upper jaw=
lower jaw=
maxilla
mandible
types of teeth and their function
incisors: (4) biting and cutting, chisel shaped
canines: (2) tearing, pointy edge
premolars: (4) crushing and grinding
molars: (6) crushing and grinding
32 together
tongue to stomach
food is swallowed
bolus is pushed into pharynx by tongue
oesophagus: made of mucosa, muscle (circular and longitudinal)
oesophagus pushes food from the mouth to the stomach by a wave of circular, muscular contractions called PERISTALSIS. movement lubricated by mucosa, prevents friction
the stomach
after passing the diaphragm, the oesophagus reaches the stomach
mechanical:
waves of muscular contraction churns food and mixes it with gastric juices (HCl and enzymes) into thick soupy liquid called chyme
stomach has third muscle (oblique) to assist with churning
chemical:
gastric juices made in gastric glands of mucosa, contains enzyme pepsin (gastric protease) that begins protein breakdown. pepsin works in acidic conditions, that’s why it need activated by Hal to go from pepsinogen to pepsin
absorption: only alcohol and drugs absorbed in to blood
stomach wall lining
deep folds called rugae line stomach to help it expand to increase volume
first is the cardiac sphincter then it is the pyloric sphincter
thick mucus walls
stomach to small intestine
chyme goes into the duodenum (1st part of small intestine), through the pyloric sphincter (prevents food spilling into the duodenum too soon)
transferred by peristalsis (2-8hrs)
3 parts of small intestine
- duodenum
- jejunum
- ileum
the duodenum and jejunum
mechanical:
waves of muscular contractions (L&C walls of small intestine),churn the food, peristalsis
bile stored in gall bladder, and made in liver, is secreted through duct and emulsifies fats
chemical:
pancreatic juices from the pancreas enter the duodenum (pH8) and neutralises the chyme, contains enzymes
- pancreatic protease: proteins to amino acids
-pancreatic amylase: carbohydrates to simple sugars
-pancreatic lipase: fats to fatty acids and glycerol
intestinal juice fro intestinal glands in the mucosa completely chemical digestion
bile
emulsifies fats (breaks them down to tiny droplets, doest chemically change it)
has salts in it, not an enzyme
travels via duct to duodenum, helps neutralise chyme
increases surface area of fats so pancreatic lipase cancan quicker
ileum/ small intestine
most products of digestion (V+M, H2O) are absorbed into the blood capillaries of the villi through diffusion, osmosi and active transport (depends on conc)
fast and fat soluble vitamins absorbed into the lacteals of the lymphatic system and transported to the chest, where they enter the blood and go to the liver
lacteals are permeable to larger fat molecules
villi and microvilli in small intesine increase surface area to increase absorption rate
large surface area of small intestine
very long (6m)
inner mucosa lining has many folds
mucosa has villi on it, cells covering villi have further projections (microvilli)
has dense network of capillaries to absorb nutrients
epithelium is very thin (1 cell thick)
ileum to large intestine
waste products of digestion go through large intestine
1.5 m long, no villi but mucosa is secreted to lubricate
bacteria breakdown remaining organic compounds
vitamins, minerals and water absorbed into blood, leaving contents semi-solid
faeces stored in rectum and eliminated through anus
faeces consists of, undigested cellulose, bacteria, bile, pigments, cells.
FUN FACT: cellulose stimulates movements of the alimentary canal.
