Digestive System Flashcards
structures of the GI tract
mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus
mechanical digestion
breakdown of large food particles into small particles by physical means (i.e the teeth grind and mash food into smaller bits)
chemical digestion
chemical alteration of food (i.e protein is chemically digested into amino acids)
2 forms of movement
segmentation: alternate contraction and relaxation of stomach muscles digest food mechanically and mix with digestive juices
peristalsis: a rhythmic alternating contraction and relaxation that pushes food forward through the GI tract
serosa
made up of: mesentery, mesocolon (peritoneal membranes//behind GI organs), and omentum (front)
helps anchor the digestive organs, blood/lymph vessels, and nerves to the abdominal organs
ENS
enteric nervous system
regulates GI motility and secretion; its activity is modulated via autonomic nerves, the parasympathetic nervous system
mouth
digestion begins immediately
includes: teeth, tongue, salivary glands, and several other structures
teeth
masticate (chew)
deciduous (baby teeth)
gingiva (gums)
dentin
majority, bonelike material of tooth
pulp
nerves, blood vessels, and CT
beneath dentin: pulp cavity
periodontium
the tissues that surround the teeth include: gums, bone, soft tissue
tongue
func.
facilitates chewing, swallowing, and repositioning of food
contains taste buds
frenulum
anchors tongue to floor of mouth
salivary glands
parotid (largest), submandibular, sublingual (smallest)
digestive enzyme: salivary amylase (ptyalin)
hard & soft palates
hard: anterior, separates oral cavity from nasal
soft: uvula blocks food from entering nasal cavity
pharynx
involved in deglutition (swallowing)
only the oropharynx and laryngopharynx are part of the GI tract
esophagus
hollow tube that carries food from pharynx to stomach via the pharyngoesophageal sphincter and the LES (relax: open // contraction: closed)
pyrosis
heartburn
GERD
gastroesophageal reflux disease
stomach
func.
1) secretion of gastric juices, includes: digestive enzymes, hydrochloric acid (HCl), and intrinsic factor
2) digestion of food. mostly mechanical, limited chemical
3) absorption of small quantities of water and dissolved substances… absorbs only alcohol quickly
4) secretion of gastric hormones
5) regulation of rate at which partially digested food is delivered to the duodenum via pyloric sphincter
layers of stomach
mucosa, submucosa, muscle, and serosa
muscle layers
longitudinal, oblique, circular
glands of the stomach
exocrine: {gastric juice} 3 secretory cells; mucous cells: secrete mucus, chief cells: secrete digestive enzymes, parietal cells: secrete HCl and intrinsic factor
neuroendocrine: g cells: secrete gastrin [released in response to vagus nerve stimulation and the presence of amino acids and small peptides in the stomach]
small intestine
func.
1) receives chyme from stomach and digestive juices from liver (bile) and pancreas (digestive enzymes); digestion is completed in small intestine
2) absorbs the end-products of digestion and key substances as iron and vitamins
3) moves the unabsorbed content into large intestine
small intestine
parts
{most digestion and absorption occur in the duodenum and first third of the jejunum}
duodenum: receives chyme and other digestive enzymes from liver, pancreas, and gallbladder
jejunum
ileum: func. to complete the process of absorption of end-prod, b12, and bile salts; ileocecal sphincter prevents reflux of contents from the cecum
wall of small intestine
microvilli
villi; within each villus
{absorptive capillaries}
{lacteal}
Protein, Carbs, Fats digest order
Protein and Carbs go to the liver first before being distributed throughout the body
Fats breakdown later and the end-products enter the lacteal, forming a milky-white lymph called chyle
hormones of the small intestine
secretin: stims pancreas to release sodium bicarbonate {nature’s own antacid}; makes chyme alkaline
cholecystokinin: stims gallbladder to contract releasing bile; stims pancreatic release of digestive enzymes; slows gastric emptying
large intestine
sect.
cecum
colon {ascending, transvers, descending, sigmoid}
rectum
anal canal
anus
tenia coli: connective band causing pucker
haustra: bulbous pouches
large intestine
func.
1) absorption of water and electrolytes
2) synthesis of certain vitamins by intestinal bacteria (K and some B)
3) Temp. storage of feces
4) Elimination of waste from body (defecation)
liver
func.
Main: Synthesis of bile salts and secretion of bile
2) synthesis of plasma proteins
3) storage; glycogen // fat-soluble vitamins
4) detoxification
5/6) metabolize carbs and proteins
7) metabolize fat
8) phagocytosis
pancreas
func.
{pancreatic enzymes are the most important of all digestive enzymes}
secretes both exocrine and endocrine substances
exocrine: digestive enzymes and alkaline secretion (neutralizes highly acidic chyme)
gallbladder
func.
pear-shaped sac attached beneath the liver
concentrate and store bile
carbohydrates
types
sugars: monosaccharides (glucose, fructose, galactose)& disaccharides (sucrose, maltose, and lactose)
starches: polysaccharides
polysaccharides breakdown
1) amylases breakdown poly into disacc
2) dissacharidases breakdown dissac’s into mono
protein
types
digested by?
building blocks = amino acids
several amino acids together = peptide
many amino acids together = polypeptide
very long chains of polypeptides = protein
enzymes called proteases
protein
types
digested by?
building blocks = amino acids
several amino acids together = peptide
many amino acids together = polypeptide
very long chains of polypeptides = protein
enzymes called proteases
fat
types
digested by?
long-chain fatty acids attached to a glycerol
enzymes called lipases
bile emulsifies the large fat globules into thousands of tiny particles that lipases breakdown for absorption
bile
func.
emulsification of fat
prevent reformation of large fat globules
help with absorption of fat-soluble vitamins (A, D, E, K)
