digestive system Flashcards
muscosa
simple columnar epithelium
mucus
found in stomach
mucous
secreted by goblet cells
protects digestive organs
eases food passage
lamina propria
loose areolar CT
contains capillaries for nourishment and absorption
lymphoid follicles (MALT) that defend against microorganisms
muscularis mucosae
SM
aids in local movements of mucosa
submucosa
loose areolar CT
contains blood, lymphatic vessels, lymphoid follicles, submucosal nerve plexus
serosa
part of visceral peritoneum
loose areolar CT covered w/ mesothelium in most digestive organs
replaced w/ fibrous adventitia in esophagus
peristalsis
adjacent segments of the alimentary tract organs which alternately constrict and relax moving food along the tract distally
occurs in esophagus, stomach, small intestine, and large intestine
initiated by rise in hormone motilin in late intestinal phase
segmentation
nonadjacent segments of alimentary tract organs which alternatively contract and relax moving food forward then backward;
food mixing and slow food propulsion
occurs in small intestine
parasympathetic NS increases while sympathetic decreases
long ANS fibers
synapse w/ enteric plexus
control digestion by either sympathetic or parasympathetic stimulation
sympathetic stimulation
inhibit digestive activities
decreases gastrin secretion
parasympathetic stimulation
stimulate digestive activities
increases gastrin secretion
short ANS fibers
synapse w/ submucosal nerve plexus and myenteric nerve plexus
submucosal nerve plexus
regulate glands and SM in the mucosa
myenteric nerve plexus
controls GI tract motility
buccal cavity
oral mucosa (stratified squamous epithelium)
teeth
salivary glands
tongue
uvula
salivary glands
produce saliva
parotid, submandibular, sublingual
parotid gland
anterior to ear
external to masseter muscle
opens into oral vestibule next to the 2nd upper molar
serous
submandibular gland
medial to body of mandible
opens at the base of the lingual frenulum
serous
sublingual gland
anterior to submandibular gland under the tongue
opens via 10-12 ducts into the floor of the mouth
mucous
saliva
97-99.5% of water
slightly acidic
consists of electrolytes, salivary amylase and lingual lipase, mucin, urea and uric acid, lysozyme, IgA, defensin
crown
covered by enamel
cement
calcified CT
covers root and attaches it to peridontal ligament
peridontal ligament
forms gomphosis
gingival sulcus
groove where the gums border the tooth
pulp cavity
surrounded by dentin
contains pulp embedded in root canal and extends to root
pulp
houses blood vessels and nerves
deciducus teeth
20
erupt 6-24 months of age
fall out b/w ages 6-12
permanent teeth
32
functions of saliva
moistening and lubricating
initiation of digestion
protection of oral tissues
buffering action
taste
oral hygiene
dentin
bone-like material under enamel
enamel
made up of hydroxyapatite
wisdom teeth
aka third molars
may erupt at ages 17-25, or may not erupt at all
functions of buccal cavity
mechanical digestion via chewing or mastication
initiation of digestion via amylase
taste
formation of bolus
initiation of swallowing
filiform
whitish
gives tongue roughness and provides friction
fungiform
reddish
scattered over tongue
contains taste buds
vallate
V-shaped row in the back of tongue
contains taste buds
foliate
on lateral aspects of posterior tongue
contains taste buds that are found primarily in infants and children
tongue
skeletal muscle
reposition and mix food while chewing
formation of bolus
initiation of swallowing, speech, and taste
hard palate
palatine bones and palatine processes of maxillae
slightly corrugated to help create friction against tongue
soft palate
formed mostly of skeletal muscle
closes off nasopharynx during swallowing
contain uvula
pharynx
stratified squamous epithelium and mucus producing glands
divided into oropharynx and laryngopharynx
allows the passage of food, fluids, and air
esophagus
stratified squamous epithelium and esophageal glands that secrete mucus
muscularis externa (skeletal-superior, mixed-middle, smooth-inferior)
adventita
deglutition
involves tongue, soft palate, pharynx, and esophagus
consists of buccal and pharyngeal-esophageal phase
buccal phase
voluntary contraction of tongue
pharyngeal-esophageal phase
involuntary stimulation due to the vagus nerve
control center in medulla and lower pons
stomach
4 tunics
greater and lesser curvature
greater and lesser omentum
muscularis externa (3 layers of SM and inner oblique layer)
mucosa composed of simple columnar epithelium with goblet cells
gastric pits that contain gastric glands (produce gastric juice)
mucosal barrier made up of bicarbonate-rich mucus and tight junctions
parietal glands
secrete HCl and IF
chief cells
secrete pepsinogen and lipases
enteroendocrine glands
secrete serotonin (inhibitory), histamine, somatostatin (inhibitory), and gastrin
functions of stomach
mechanical digestion
secretion of gastric juices
regulation of gastric emptying
inner oblique layer
allows stomach to churn, mix, move, and physically break down food
pepsinogen
digests proteins
inactive enzyme
activated to pepsin by HCl or pepsin itself
lipases
digests ~15% of lipids
cephalic phase
conditioned reflex triggered aroma, taste, sight, thought
gastric phase
lasts 3-4 hrs
2/3 gastric juice released
stimulated by low acidity, distension, peptides, gastrin
Ach, histamine, gastrin necessary for max HCl secretion
enteroendocrine G cells
stimulated by caffeine, peptides, increased pH
intestinal phase
when partially digested food enters SI, it triggered gastrin release
release inhibited via chyme, fats, peptides, and irritating substances
enterogastric reflex
inhibits vagal nuclei in medulla
inhibits local reflexes
activates symp fibers
inhibits gastrin secretion
enterogastrones
secretes secretin, CCK, VIP
inhibits gastrin secretion
emesis
caused by extreme stretching and intestinal irritants such as bacterial toxins, alcohol, spicy foods, drugs
chemical/sensory impulses stimulate the emetic center of the medulla
liver
4 lobes (right, left, caudate, quadrate)
falciform and round ligament
common, hepatic, cystic bile duct
lobules hexagonal in structure and composed of hepatocytes
central vein in longitundinal axis
portal triad at each corner of a lobule (hepatic artery, portal vein, bile duct)
liver sinusoids
stellate macrophages
falciform ligament
separates larger right lobes from smaller left lobes
suspends liver from diaphragm and anterior abdominal wall
common hepatic duct
leaves liver
cystic duct
connects to gallbladder
bile duct
formed by the union of common hepatic and cystic duct
hepatocytes
increased rough and smooth ER, golgi, peroxisomes, and mitochondria
filter and process nutrient-rich blood
produce bile
perform detoxification
store fat-soluble vitamins
stellate macrophages
kupffer cells
remove debris and old RBCs
liver sinusoids
leaky capillaries b/w hepatic plates
functions of liver
detoxification
production of bile
regulation of cholesterol levels
bile
composed of bile salts, bilirubin, cholesterol, triglycerides, phospholipid, electrolytes
stored in gallbladder
released into SI following food ingestion, hormonal stimulation (CCK, secretin, gastrin)
function of bile
emulsification of fats
facilitation of fat digestion and absorption
gallbladder
stores, concentrates (absorbs water and ion), and releases bile
circular folds
force chyme to slowly spiral through lumen of SI
increases nutrient absorption
villi
extensions of mucosa w/ capillary beds and lacteals for absorption in SI
microvilli
brush border
contains enzymes for carbs and protein digestion
intestinal crypts
house secretory cells that produce intestinal juice (enteroendocrine and paneth cells)
enteroendocrine cells
secrete enteroendogastrones
paneth cells
secrete defensins and lysozyme
duodenum
curves around head of pancreas
shortest part
jejunum
extends from the duodenum to the ileum
2.5 m long
ileum
joins the large intestine at the ileocecal valve
3.6 m long
functions of SI
absorption
nutrient transport
regulation of pH and digestive enzymes
immune functions
secretion of hormones
bile acid sequestrants
cholestryramine, colesevelam, colestipol
decreases cholesterol by binding to bile acids in the intestines, preventing reabsorption
increases excretion of bile acids and production of new bile
4 tunics of digestive organs
mucosa
submucosa
muscularis externa
serosa or adventitia
amylase
digest carbs
lacteals
found in villi of SI
nutrient absorption of dietary lipids
carb digestion
starch and disaccharides via salivary and pancreatic amylase in mouth (salivary glands) and pancreas
further broken down into monosaccharides via brush border enzymes in SI
glucose and galactose are absorbed via co-transport w/ Na+ ions
protein digestion
proteins broken down to large polypeptides via pepsin in stomach
large polypeptides broken down to small polypeptides and peptides via pancreatic enzymes in pancreas
further broken down to AA’s via brush border enzymes in SI
AA are absorbed in intestinal cells via co-transport w/ Na+ ions
some dipeptides and tripeptides are absorbed via cotransport w/ H+ and hydrolyzed to AA within cells
infrequently, transcytosis of small peptides occurs
lipid digestion
unemulsified triglycerides broken down into monoglycerides via lingual lipase in the mouth (tongue), gastric lipase in the stomach, pancreatic lipase in the pancreas, and bile in the liver
fatty acids and monoglycerides enter the intestinal cells via diffusion
nucleic acid digestion
pancreatic ribonuclease and deoxyribose->nucleotide monomers in SI
brush border enzyme nucleosidases and phosphatases-> free bases, pentose sugars, phosphate ions in SI
units enter intestinal cells by AT via membrane carriers
nutrient absorption
all absorbed into capillary blood in the villi of SI and transported to the liver via the hepatic portal vein
absorbed via FD for carbs and proteins.
pancreas
endocrine cells consist of pancreatic islets that secrete insulin and glucagon
exocrine cells consist of acini that secrete pancreatic juice
secretes pancreatic amylase, lipase, and nuclease
pancreatic juice
watery, alkaline solution
neutralized chyme
pH of 8
consists of electrolytes and enzymes (amylase, lipase, protease)
protease
secreted in inactive form
activated in duodenum w many other enzymes such as trypsinogen, procarboxypeptidase, and chymotrypsinogen
CCK
induces the secretion of enzyme-rich pancreatic juice via acini
relaxes hepatopancreatic sphincter
secretin
causes the secretion of bi-carbonate rich pancreatic juice via duct cells
large intestine
simple columnar epithelium
abundant crypts w/ goblet cells
teniae coli
haustra
cecum
appendix
ascending, descending, transverse, sigmoid colon
rectum
anal canal
internal and external anal spincters
anal canal
stratified squamous epithelium (withstands abrasion)
functions of large intestine
absorption of water and electrolytes
formation and storage of feces
synthesis of vitamins (vitamin K)
immune functions (MALT)
peristalsis
fermentation of indigestible carbs
release of gases and fecal matter
feces
composed of undigested material (fiber and cellulose), water, bacteria, dead cells, mucus, stercobilin
formed by the gradual accumulation and processing of waste material in the large intestine
stored in rectum until defecation occurs
defecation
- distention of rectum initials spinal defecation reflex
- parasympathetic NS is activated and stimulates the contraction of the sigmoid colon and rectum, as well as relaxes the internal anal sphincter
- concious control allows relaxation of the external anal sphincter
- feces is expelled from anus
trypsinogen
activated to trypsin via enteropeptidase
trypsin
activates procarboxypeptidase and chymotrypsinogen
illeocecal sphincter
relaxes and admits chyme into large intestine when gastroileal reflex enhances force of segmentation in ileum and gastrin increases motility of ileum
internal anal sphincter
smooth muscle
external anal sphincter
skeletal muscle
gastrocolic reflex
initiates mass movement in the LI
osmosis
used to absorb water from the intestine
hepatopancreatic sphincter
regulates flow of bile from the liver and pancreatic juice from the pancreas into the duodenum of the SI
gastroileal reflex
movement of food from the stomach to the SI
emulsification
bile salts in bile interact with the fat molecules, breaking them down into smaller droplets
increases the SA of the fat, making it easier for digestive enzymes called lipases to access and break down the fats into fatty acids and glycerol, which can then be absorbed by the small intestine
micelles
composed of bile salts, phospholipids, cholesterol, fatty acids
formed in SI during lipid digestion and absorption (dietary fats and fat-soluble vitamins)
transport lipids across intestinal epithelial cells for absorption