Digestive Flashcards
primary foodstuffs
proteins, carbohydrates, fats
four major functions of the digestive tract
- motility
- secretion
- digestion
- absorption
motility movements
propulsion and mixing
what portions of the digestive tracts are skeletal muscles?
mouth and anal sphincter
what portion of the digestive tract is controlled by the sympathetic nerve? what does it do?
the first half, slows down food movement
what portion of the digestive tract is controlled by the parasympathetic nerve? what does it do?
the second half, it speeds up smooth muscle activity
secretion
energy demanding
- digestive juices and enzymes
- higher number of mitochondria
digestion
hydrolysis is used to break down into absorbable units
- splits chemical bonds of large nutritive material
absorption
transfer absorbable units, water, electrolytes, and vitamins into blood from the digestive lumen
mucosa
contains endocrine glands to release gastrointestinal hormones based on the content in the lumen
muscularis externa
longitudinal muscles
circular muscles
what portion of digestive anatomy drive movement of the muscularis externa?
submucosal plexus
mylenteris plexus
what makes up the mucosa?
serosa, laminar cells, muscular area and mucus
mesentery
the portion of digestive anatomy that holds the tract to the body wall
serosa
outer connective tissue covering the digestive tract, secretes a watery fluid called serous fluid
mucous membrane
an inner epithelial layer that serves as a protective surface
submucosa
a thick layer of connective tissue that provides the digestive tract with its distensibility and elasticity
submucosal plexus
lies within the submucosa, a nerve network
myenteric plexus
a nerve network, lies between the two muscle layers
what helps regulate gut activity?
submucosal and myenteric plexuses, along with GI hormones, local chemical mediators
mouth
oral cavity
- tongue is base
- separate from nasal passages
mastication
chewing
yout tongue does what?
turns chemical signals into electrical ones
saliva contents
95.5% water
4.5% proteins and electrolytes
major salivary proteins
amylase, mucus, lysozymes
the mouth is the first location of ______ digestion
carbohydrate
other roles of saliva (5)
- mucous for lubrication
- lysozymes for killing bacteria
- taste
- speech
- carries HCO3- to neutralize food
deglutition
swallowing
two stages of deglution
- oropharyngeal (1 second)
- esophageal (1-5 seconds)
what happens during the oralpharyngeal stage of swallowing? (6)
- respiratory centers inhibited
- tongue moves to palate
- uvula elevated to prevent food from entering nasal passages
- vocal chords seal the glottis to prevent food into trachea
- epiglottis falls back on closed glottis
- pharyngoesophageal sphincter retracts to allow food to enter
what happens during the esophageal stage of swallowing? (3)
peristalsis
- trigger vagus nerve to contract circular muscles
progressive movement of food
gastroesophageal sphincter
connects stomach and esophagus
- underdeveloped/damage can cause heartburn or spitting up in infants
fundus
top portion of the stomach
- thin muscles
- onythic mucosa
- contains air/gas
- above sphincter
- no food storage
stomach body
- food storage
- thin muscle
- oxyntic mucosa
- feeble mixing
- important for gastric filling
- receptive relaxation
receptive relaxation
rugae folds respond to chime in the stomach and unfold
anthrum
- thick muscle
- strong peristaltic movements
- lots of gastric mixing and emptying
- retropulsion
- secretes hormone gastrin
- PGA = pyloric gland area
four primary functions of the stomach
- store ingested food
- secrete HCl
- absorb intrinsic factor B
- start protein digestion
retropulsion
- stimulus triggers the BER on pacemaker cells in anthrum
- increased AP frequency to increase gastric emptying
stimuli on pacemaker cells in the anthrum (5)
- increase in chyme, distension, large amounts of fluid intake
- sadness/fear decrease motility
- pain inhibits gastric movement entirely
- anger/aggression increases gastric movement
- increase parasympathetic (vagus) to increase peristalsis
four stimuli detected by the small intestine (stops)
- high amounts of fat
- high levels of acid
- hypertonicity - lots of units with digestive breakdown
- distension - too much chyme
surface epithelial cells
secrete mucus and alkaline contents
mucus neck cells
- secrete mucus
- pluripotent
- regenerate entire stomach in 3 days
parietal cells
- secrete HCl
- absorb intrinsic factor B12 for bone marrow
chief cells
secrete pepsinogen
what is pepsinogen cleaved by to make pepsin?
HCl
what does pepsin do?
cleaves proteins to amino acids
HCl roles
- cleaves pepsinogen to pepsin
- break down muscle and connective tissue
- helps kill pathogens
PGA
pyloric gland area
gastrin
- positively upregulates pepsinogen from chief cells
- positively regulates HCl secretion
- stimulates growth factor release to help regenerate stomach and small intestine
six signals to increase gastrin
- protein in the stomach
- chewing/chemosensory transduction from tastebuds
- smell/taste
- caffeine
- alcohol
- distension of protein in the small intestine
three signals to decrease gastrin
- when the body of the stomach begins to empty
- high acidity in the anthrum
- stops in the small intestine
small intestine
- site of most digestion and absorption
- exclusive site of fat digestion
- indiscriminately digests all food stuffs, 100% absorbed
- iron/calcium uptake is adjusted to body needs
five enzymes in the doudenum
- trypsinogen (trypsin)
- chymotrypsinogen (chymotrypsin)
- procarboxypeptidase (carboxypeptidase)
- pancreatic lipase
- pancreatic amylase
- 1, 2, 3 are for proteins
- 4 is for fats
- 5 is for carbos
duct cells
- secrete H2O, mucus, NaCl, no enzymes
acinar cells
have zymogen granules with 3 different enzymes
bile composition
- bile salts - allow formation of micelles
- cholesterol - can aggregate to form gallstones
- bilirubin
- lecithin
- NaHCO3 - balance acidity
- no digestive enzymes
bilirubin
breaks down dead red blood cells/heme, can form gallstones, cause of jaundice
bile salts are responsible for _____
emulsification
four key parts of the small intestine
- segmentation
- brush border
- crypts of Lieberkühn
- absorption mechanisms
segmentation of the small intestine
- contraction of circular muscles that alternate to mix chyme with enzymes
- not sweeping movement like peristalsis
- differential moves food forward
- 12 contractions/min —–> 9 contractions/min
small intestine brush border
circular folds —> villus projections —> villi —> epithelial cells —> 5-6 thousand microvilli per epithelial cell
apex of the brush border
- shedding about 100 million cells a minute
- cells here are the most enzymatically active, highest absorption, and most sensitive to radiation
how long does it take cells to move from the crypt to apex of the brush border?
3 days
what absorbs proteins and carbos in the brush border?
the capillaries
what absorbs fats in the brush border?
lymphatic system
