Pre 9/14/22 Flashcards
oral cavity
mouth + pharynx + salivary glands
functions of oral cavity
- gustatory
- mastication
- digestion swallowing
- speech
- respiration
main enzyme in saliva
alpha-amylase (aka ptyalin)
lingual lipace
alpha-amylase function
hydrolyzes internal (alpha 1-4) bonds within starch
lingual lipase function
hydrolyzes dietary triglycerides in mouth and stomach
salivary glands must keep good regulation of…
conc of water
stimulation of salivary glands
- tactile stimuli
- taste
- other inputs: olfactory, visual, etc.
mechanics of digestion first two steps
- mastication (chewing): releases nutrients and increases total surface area of foods
- swallowing
swallowing is…
highly regulated
stages of swallowing
- voluntary stage
- pharyngeal stage
- esophageal stage
voluntary stage of swallowing
pressure of tongue squeezes and rolls bolus to pharynx
swallowing can’t be stopped
everything else is involuntary
pharyngeal stage
initiate a series of automatic pharyngeal contractions
forces bolus into upper esophagus
esophageal stage of swallowing
bring food rapidly from esophagus to stomach
primary and secondary peristalsis
primary digestive system organs
- mouth
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
secondary organs in the digestive system
- salivary glands
- liver
- gallbladder
- pancreas
what are the main functions of the oral cavity
eating, speaking, beginning digestion
which phase/s of swallowing is/are voluntary
voluntary phase/preparatory/oral phase
phase 1
which part of nervous system controls swallowing
CNS
pancreas anatomy
- ductless endocrine cells that secrete hormones into the blood
- acinar exocrine cells
acinar exocrine cells
produce digestive juice and enzymes
pancreas 3 parts
- head
- body
- tail
pancreatic exocrine cells secrete
pancreatic digestive enzymes
lots of bicarbonate released into pancreatic ducts
pancreatic enzymes + bicarbonate flow
pancreatic duct –> common bile duct to release
what triggers pancreatic enzymes
chyme in upper portion of small intestine
insulin is secreted by…
pancreas
directly into blood by Islets of Langerhaans
pancreatic juice contains
- bicarbonate
- electrolytes (sodium, potassium, chloride), calcium
- pancreatic digestive enzymes
- -zymogens: proteases
- -other enzyme: amylase, lipace, RNase and DNase
exocrine cells produce and release
bicarbonate soln into ducts
during post prandial period,
pancreas responds to acid in small intestine
secretes bicarbonate to restore neutral pH
S cells
cells in proximal small intestine
release secretin in response to deacrease in pH
secretin causes release of bicarb
enterokinase
secreted from duodenal epihtelial cells
secretes zymogens
trypsin inhibitor
synthesized by pancreas
protexts pancreas by binding to trypsin if protease is accidentally activation within pancreas
largest internal organ
liver
right lobe and left lobe
liver lobes are made up of
lobules
made of hepatocytes
central veins
drain blood from liver and bring nutrients into circulation through hepatic veins, then inferior vena cava
blood passes through…
sinusoids: act as channels
sinusoids arise from branches of hepatic artery and portal vein
portal vein
brings blood from digestive tract to liver
bile canaliculi
transports bile to main bile duct in liver
Kupffer cells
macrophage like cells in liver
stellate cells
liver cells
store Vitamin A
liver functions
- centralize and segregate absorbed nutrients for metabolism, storage, or transport
- produce bile acids and salts
- excretes metabolic waste
- detoxification
bile
alkaline soln (pH 7.6-8.6) composed of:
1. bile acids and salts
2. cholesterole and phospholipids
3. bile pigments (bilirubin and biliverdin)
2 primary bile acids
- chenodeoxycholic acid
- cholic acid
made in hepatocytes from cholesterol
combine with sodium, potassium, calcium to form bile salts
conjugate with glycine or taurine
conjugation of bile acids with amino acids helps
ability to form micelles
bile acids function
biological detergent
emulsify and break down large fat globules into small fat droplets
increases surface area
what are the main anatomical/functional areas of pancreas?
what are the main components of pancreatic exocrine secretions?
what are the main components of pancreatic endocrine secretions?
what are the main enzymes secreted by pancreas?
Lipase, amylase, protease
what are the components (hormones, cells, and chemical compounds) and sequence of events in the mechanism for the regulation of pH in the duodenum?
What are the main cell types in the liver and what are their functions?
What components (nutrients, gases, excretion products, etc.) are mainly treansported by the hepatic artery, the portal vein, and central vein, respectively?
Hepatic artery: oxygenated blood
Portal vein: nutrients toxins from digestion
Central vein:
what are the main biochemical components of bile?
what are the main biochemical modifications of bile salts? what is the functional purpose?
what are the main functions of bile?
esophagus
connects pharynx to stomach
lined by mucosa (a type of epithelial tissue)
how does food enter the esophagus
bolus is sent from pharynx to esophagus
upper esophageal sphincter (UES) relaxes AND larynx pushes upwards to open UES and allow entry
is upper esophageal sphincter under voluntary or involuntary control?
voluntary
allows for breathing, eating, swallowing
closed lower esophageal sphincter
prevents stomach acid and contents from traveling backwards
closed lower esophageal sphincter
prevents stomach acid and contents from traveling backwards
is upper esophageal sphincter under voluntary or involuntary control?
involuntary
stomach histology: muscularis
has oblique layer
allows mechanical digestion by churning
stomach epithelial lining is made of
ONLY surface mucous cells
secrete protective coat of alkaline mucous
cardiac glands
found in a narrow rim at the juncture of the espohagus and the stomach
oxyntic glands
aka gastric glands
found in the body and fundus of the stomach
pyloric glands
located primarily in the pyloric antrum
secrete mucous and gastrin
stomach glands are made up of
parietal cells
cief cells
enteroendocrine cells
somatostatin
main regulator of gastric motility and acid secretion
what is the main type of digestion in the stomach?
mechanical!
stomach: digestion role
- initiates protein hydrolysis/degradation by releasing pesinogen
- limited continuation of starch hydrolysis
- limited lipolysis
- absorption of water, alcohol, and a few drugs and mineralas
- intrinsic factor release
why is starch hydrolysis limited in stomach?
acid induced inactivation of saliary amylases limits starch digestion in the stomach
gastric lipase in stomach digestion
limited lipolysis of short- and medium chain triglycerides (EX: ones in milk)
only organ that releases intrinsic factor (IF)
stomach
small intestine 3 regions
duodenum, ileum, jejunum
small intestine: ileocecal sphincter
last segment of small intestine
cecum
first segment of large intestine
duodenum
receives secretions from gallbladder via common bile duct
where do pancreatic secretions go in the small intestine?
pancreatic duct which drains to common bile duct
Sphincter of Oddi
regulates flow of secretions into duodenum
small intestine surface area
very large!
small intestine mucosa and submucosa are arranged in circular folds called
folds of Kerckring
prutrude into lumen of small intestine
villi
each villus is made of enterocytes (absorptive cells)
folds of Kerckring are covered by
finger-like projections called villi
each villi has a capillary network and lymphatic vessel
enterocytes
absorptive cells
covered with microvilli
brush border is made up of
microvilli
impact nutrient absorption
how does chyme move through the small intestine? (type1)
mixing movements: pushed back and forth within adjacent segments of intestine
circular muscles alternate contracting and relaxing
chyme flow
bidirectional bc of segmentation contractions
how does chyme move through the small intestine? (type 2)
propulsive movements: peristaltic waves
takes 3-5 hours for chyme to go from duodenum to ileocecal valve
pathway of movement after entering large intestine
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
- anal canal
functions of colon:
- absorption of water and exchange of electrolytes (proximal half)
- storage of fecal amtter (distal half)
- habitat of gut microbiome
movements of large intestine
slower, but similar to small intestine (mixing movememnts and propulsive movements)
takes 12-20 hours
poor motility in colon leads to…
excessive absorption of water
hard feces, constipation
excess motility in colon leads to…
less absorption of water and diarrhea
mechanism of defacation
constriction of internal and external anal sphincter
anal sphincters are made of
striated voluntary muscle
external anal sphincter is control by which nervous system
nerve fibers from somatic nervous system
voluntary conscious/subconscious control
intrinsic reflex of defecation
- feces enters rectum
- distention of rectal wall initiates peristaltic waves in descending colon (forces feces towards anus)
- internal anal sphincter releaxation
- if external anal sphincter is also voluntarily relaxed at the same time, defecation occurs
parasympathetic defecation reflex
signals from sacral cord intensify the peristaltic waves and relax the internal anal sphincter
what are the main anaotmical features of the esophagus?
what are the main regions of the stomach?
what are the main glands of the stomach?
which are the main cells in the oxyntic gland and what coumpound/s they secrete?
what are the main parts of the small intestine?
what are the folded structures of the small intestine (i.e. villi) and what are the main functions?
what are the main movements of the small intestine?
what are the main parts of the large intestine?
what are the main functions of the large intestine?
which are the phases of the mechanism of defecation and how is it controlled??
