mouth
aka oral cavity, contains tongue, teeth, hard and soft palate, uvula, and salivary glands. opens to throat
teeth
masticates food via cutting, tearing, and grinding. 32 permanent ones.
salivary glands
produces saliva via ducts (exocrine system) to moisten food. contains salivary amylase (ptyalin), bicarbonate ions (HCO3-), and mucins
parotid gland
salivary gland, found near front of the ears
submandibular gland
salivary gland, found deep in floor of mouth
sublingual gland
salivary gland, found beneath the tongue
salivary amylase/ptyalin
hydrolyzes starch into maltose. produced by salivary glands
bicarbonate ions (HCO3-) for salivary glands
buffer, keeps pH between 6.5-7.5. produced by salivary glands
mucins in mouth
lubricates bolus. produced by salivary glands
bolus
soft ball of food, composed of food and saliva
tongue
contains receptors for taste, composes a bolus for swallowing
skeletal muscles
muscles you can control and contract quickly, performs wide range of movements and function
soft palate
posterior of roof of mouth. closes nasopharynx to prevent food from entering nasal cavity, uvula hangs from here
hard palate
anterior of roof of mouth, bony + hard
nasopharynx
upper part of pharynx (throat) behind nose, connects nasal passages to rest of respiratory system
uvula
when hit by bolus, triggers swallowing reflex
pharynx (throat)
funnel-shaped pathway, leads to esophagus (into stomach) and trachea (to lungs)
swallowing reflex
food → bolus → tongue + hard palate moves → pharynx → soft palate closes → epiglottis flips down → esophagus and peristalsis → cardiac sphincter relaxes and tightens
epiglottis
flap which covers glottis. prevents food from entering lungs
glottis
trachea opening
trachea
airway that leads to lungs
esophagus
muscle tube, dorsal to trachea, unflattens and squeezes rhythmically to pass bolus to stomach via peristalsis
peristalsis
involuntary, triggered contraction and relaxation of muscles, forming a wave down a tube
cardiac sphincter
close to heart, relaxes to allow bolus into stomach and tightens to prevent contents from coming back up
sphincter
ring of muscle
pyloric sphincter
relaxes to allow small amount of chyme to enter small intestine
stomach
thick, muscular j-shaped sac responsible with storing food for up to 4 hours, secreting substances to dissolve and degrade food, and controlling rate of food entering small intestine
rugae
folded inner surface of stomach, allows expansion for food. composed of columnar epithelium
columnar epitheleium
column-shaped cells, covers end of esophagus to beginning of rectum
gastric pits
divisions of columnar epithelium, leads to gastric glands
gastric glands
produces gastric juice, composed of g-cells, chief cells, mucous cells, and parietal cells
g-cells
secretes gastrin
gastrin
stimulates secretion of gastric acid/HCl
gastric acid/HCl
degrades food, kills food-borne bacteria, activates pepsinogen to pepsin
chief cells
secretes pepsinogen
pepsinogen
inactive enzyme, becomes pepsin when exposed to gastric acid/HCl
pepsin
hydrolyzes proteins into smaller chunks at tyrosine and phenylalanine
mucous neck cell
secretes mucin-containing mucus
mucins in stomach
buffer for gastric acid/HCl, prevents stomach wall from digesting itself (no ulcers!)
parietal cell
secretes gastric acid/HCl. → actives pepsinogen
gastric juice
produced by gastric glands, 2L per day. contains water, mucus, HCl, and pepsin
does not require digestion
vitamins, minerals (elements), water, and cellulose
chyme
thick green semiliquid composed of semi-digested food and gastric juices
pancreas
contains exocrine and endocrine cells
pancreas exocrine cells
secretes pancreatic juices into pancreatic duct into duodenum
pancreas endocrine cells
produces hormones like insulin and glucagon into blood
pancreatic juice contains
P ancreatic Juice
L ipase
A mylase
N uclease
T rypsin
S odium Bicarbonate
bicarbonate ions (HCO3-) for pancreatic juice
buffer, neutralizes acidic chyme to keep pH of duodenum 8-9
pancreatic amylase
digests starch
starch + H2O → (amylase, hydrolysis) → maltose
trypsin
active form of trypsinogen, digests proteins
proteins + H2O → (trypsin) → peptides
lipase
catalyzes breakdown of lipids into fatty acids and glycerol molecules
fat droplets + H2O → (lipase) → glycerol and 3 fatty acids
bile salts
works with lipase to emulsify lipids
lipids + H2O → (bile salts) → fat droplets
pancreatic nuclease
acts in small intestine, degrades nucleic acids into nucleotides
nucleic acid + H2O → (pancreatic nuclease) → nucleotides
pancreatic islets/islets of Langerhans
composes endocrine section of pancreas. secretes insulin and glucagon (hormones)
insulin
released after eating, when blood glucose level is high. decreases concentration of glucose in blood via cell stimulation to take up and metabolize glucose
glycogen
polysaccharide. the stored version of monosaccharides, liver and muscles stimulated by insulin to promotes fat buildup, inhibiting their use as energy source
“bank for a rainy day”
glucagon
stimulates breakdown of glycogen into glucose for release into blood
what is the body sugar level based on?
the opposing action of insulin (storing of monosaccharides) and glucagon (breaking apart of glycogen)
diabetes mellitus/type 1 (early onset) diabetes
insulin deficiency, treated with insulin injections
type 2 (maturity onset) diabetes
pancreas makes enough insulin, but body cells don’t respond due to receptor protein problem. treated with weight loss, exercise, medication (Glucophage or Metformin), and/or insulin
pancreatic ‘burnout’
can be triggered by obesity
small intestine
receives Chyme (stomach), Bile (liver), and Pancreatic secretions (pancreas). mechanically breaks down chyme, absorbs nutrients, and transports waste to large intestine. its epithelial cells packed with mitochondria
duodenum
small intestine start. bile and pancreatic juices are secreted into here.
jejunum
small intestine middle. secretes digestive enzymes
ileum
small intestine longest and final section. joins cecum to ileocecal valve.
cecum
‘pouch’ that forms start of large intestine/colon.
ileocecal valve
sphincter, at junction of ileum and colon. allows waste to enter colon.
mucosa
moist inner lining of some organs and body cavities
villi
finger-like projections in the small intestine mucosa. greatly increases absorption surface area. contains capillary network and lymph vessel/lacteal
capillary networks
found in villi. absorbs vitamins (A, C) and minerals (Na, Ca) from waste
lymph vessel/lacteal
found in villi. absorbs fat and fat-soluble vitamins taken from waste
absorption
occurs when food molecules brush through microvilli/brush border. passage of nutrient molecules from GI tract into bloodstream via mesenteric veins
microvilli/brush border
micro projections on villi surface, greatly increases absorption and secretion surface area,
mesenteric vein
drains blood from the large intestine, carries nutrient molecules
vitamins (A, C) and minerals (Na, Ca) and GI tract
moves through unaltered, absorbed through mucosa into capillaries
intestinal juice
I ntestinal nuclease
M altases
P eptidases
peptidases
completes protein digestion
peptide + H2O → (peptidases) → amino acids
maltases
completes maltose digestion
maltose + H2O → (maltase) → glucose + glucose
intestinal nuclease
completes nucleic acid digestion
nucleotides + H2O → (nuclease) → nitrogenous base + monosaccharide + phosphate group
amino acids (protein), monosaccharides (carbs), and nucleotides (nucleic acids)
facilitated/active transport into epithelial cells of small intestine. diffuses into blood capillaries in villi
triglycerides (lipids)
diffuses across lipid bilayer into villi since fat-soluble. glycerol and fatty acids → epithelial cell ER → triglyceride → chylomicron → lacteals
chylomicron
rich in triglycerides. enters villi lacteal
gastrin
gastrointestinal hormone. stimulated by chyme, increases stomach mobility and gastric juices in stomach
secretin
gastrointestinal hormone. stimulated by HCl, increases pancreatic juices and stomach mobility, reduces gastric juices. produced and used by duodenum
Cholecystokinin (CCK)
gastrointestinal hormone. stimulated by proteins and lipids. produced by duodenum, stimulates gall bladder to release bile
hepatic portal vein (organ→vein→organ)
receives blood from venules from villi of small intestine, transports to liver
liver
consists of 2 lobes, receives blood from small intestine
detoxifies/destroys
poisonous substances in blood
old red and white blood cells
produces
plasma proteins (contributes to tonicity)
urea
stores
glycogen
iron and fat-soluble vitamins A, D, E, K
regulates
blood cholesterol (cholesterol → bile)
urea
waste product of protein breakdown, produced by liver.
gall bladder
small, muscular, bulb-like structure under liver’s right lobe. stores bile. induced by CCK to release bile
bile duct
carries bile from gall bladder to duodenum
bile
emulsifies fat to smaller droplets for lipase to act. made in liver, stored in gallbladder
large intestine/colon
extends from ileocecal valve to anus. absorbs water, salts, and bile to be recycled/used, compacts feces, houses beneficial bacteria
Escherichia coli (E. coli)
beneficial bacteria, housed in the colon/large intestine. produces vitamins and helps break down plant matter
rectum
terminal portion of large intestine, stores feces
distension
enlargement/ballooning of rectum. causes anus to relax
feces
waste. composed of water, fibre, dead GI cells (friction), bacteria
cecum
bottom of ascending colon. ‘blind’ pouch
appendix
small finger-like pouch connected to cecum, believed to play a role in immunity
anus
composed of internal and external sphincters, relaxes to allow feces to leave body. tightens to collect feces in rectum