Digestive Flashcards
digestive tract path
mouth
pharynx: oropharynx, hypopharynx
trachea
asophagus
stomach
large intestine
accessory digestive organs
liver
gall bladder
pancreas
food processing parts
- motility/propulsion
- chemical/mechanical digestion
- absorption
- defecation
motility is due to
muscular contractions and mixing food with digestive juices
1. swallowing: oropharynx
2. peristalsis: esophagus, stomach, small intestine large intestine
parts that do mechanical digestion
- chewing: mouth
- Churning: stomach
- segmentation: small intestine
parts that do Absorption
- small intestines: nutrients, water to blood/lymph vessels
- Large intestine: water to blood vessels
digestive tunics
lumen
1. epithelium (mucosa layer)
2. lamina propria (mucosa layer) areolar CT can have lymphatic patch and blood vessels to provide nutrients and remove waste from epithelium
3. muscularis mucosa (mucosa layer):thin layer of smooth muscle can cause epithelium to fold to increase contact with food being digested
4. submucosa/nervous plexus: normally areolar CT may have glands and nervous tissue
5. muscularis 2 layers: inner circular outer longitudinal smooth muscle
6. serosa or adventitia depending on where in digestive tract. serosa for movement, adventitia melds with surrouding CT
peritoneum
largest serous membrane in the body found in the abdominal cavity and associated with digestive tract
Parts of peritoneum
- lesser omentum
- mesocolon
- mesentary
- greater omentum/fatty apron
lesser omentum characteristics
liver to the stomach
mesocolon characteristics
the transverse colon to posterior abdomen wall
greater omentum characteristics
hangs down in front of the small and large intestines. folds over itself and makes 2 layers of double membrane
mesentary characteristics
surrounds the small intestine connects the posterior ab wall. is like a fan around the small intestine
falciform ligament characteristics
connects liver to the anterior of the ab wall. looks like its dividing the liver
serous membrane
2.5 layers
1. visceral: against the organs
1.5 paritoneal cavity has paritoneal fluid between membranes for blood vessels nervs and lymph vessels to access organs
2. parietal: lines the wall of the cavity
salivary glands
- parotid gland: carries saliva and amylase through the parotid duct to the upper cheeck by second molar. largest, between the ear and masseter.
- submandibular gland: carries amylase and mucus. 2nd largest. along the mandible
- sublingual gland: only saliva/mucus. about 10-12 small ducts to release saliva
How much saliva per day
1.5 L. parasympathetic (relax and digest) stimulates flow
which nervous system is for digestion
parasympathetic. sympathetic inhibits it and gives dry mouth
saliva composition
- 99% water: dissolves food for taste, provide H2O for hydrolysis
- IGA immunoglobulin: antibacterial
- Phosphate ions/salts
- HCO3- : buffers pH
- Cl- : activates saliva amylase
- Amylase: digests amylose part of starch/carbs
- lysoszomes: damage bacteria cell walls
- mucus: lubricates food for easier swallowing
Saliva function
- moisten mouth, aid in swallowing
- Start digestion of starches with amylase
- clean/get things away from teeth
- inhibit bacteria growth
- dissolves food molecules which stimulates taste buds
extrinsic tongue muscle
Cranial nerve 12 controls, moves tongue fwd, back, side-side
FIlliform papillae
smallest of taste papillae, no taste buds only texture
esophagus locatin
6th cervical-11th thoracic, posterior to trachea, peirces diaphram through esophageal hilus meets stomach at cardiac orifice
esophagus characteristics
same basic tunics as digestive system
mucosa is nonkaratinized stratified ssquamous due to friction of food.
upper esophageal sphincter: upper part has skeletal muscle (you control swallowing)
lower esophageal sphincter: lower part smooth muscle (automatic)
swallowing phases
- voluntary: tongue pushes bolus to the oropharynx
- pharyngeal phase: involuntary. food goes down esophagus
- esophageal phase: bolus to stomach through peristalsis. circular muscle closes behind, longitundinal contracts to be smaller the circular muscle contracts and pushes the bolus down
stomach holds how much food and for how long
2-4L
2-4hrs
stomach functions
- digestion
- storage
pyloris
stomach area next to the exit to the small intestine: exit controled by pyloric sphincter
Chyme
name for contents in stomach
where is a gastric gland located
bottom of the gastric pit that extends to the lamina propria
how often is epithelium in stomach replaced
3-6 days
stomach muscularis layers
- longitudinal (outside)
- circular (mid)
- oblique (deepest)
how often does the stomach mix food
15-20s
cells that line gastric pits
- chief cells: secrete pepsinogen precurser to pepsin
- parietal cells: make HCL and intrinsic factor
- mucous cells: protect epithelium
- G-cells: secrete hormone gastrine (enteroendocrine)
Pepsin
cuts C terminal of carboxyl end of: phenylalaine, leucine and glutamic acid. activated by HCL and activated pepsin
pensinogen secreted by cheif cells
Intrinsic factor
secreted by parieta cells
need intrinsic factor to absorb B12 which is needed to make mature RBC
only necessary for life function stomach does
Gastric juice properties
pH 2
2-3L/day is made
pernicious anemia cause
insufficient B12 absorption
Small intestine time with chyme
3-5hrs
duodenum function
extremely active in chemical digestion
ducts from pancreas and liver deliver digestive juices to it
no mesentary
circular muscle little thicker than long muscle
jejunum and ileum functin
mostly absorbs nutrients has mesentary
you get more _____ the further along small intestine
lymphatic/peyers patches
plicae circulares
Helps slow movement of chyme, permanent deep ridges make little shelves. submucosa layer of small intestine makes “circular folds” on top of which have villi
gets smaller the further you go
duodenal/bruners glands
secrete alkaline digestive juice with bicarb ion and peptidase enzyme
samll intestine increases SA by how much
600x by
plicae circulares
villi
microvilli
villi characteristics
“fingerlike” projections w/ columnar cells: inside are lamina propria, lacteals, blood vessles, litle smooth muscle to wave around and increase contact with chyme
brushborder
microvili in small intestine called this. has enzymes but none are secreted by the cells, it is just held there by the border
carbohydrate brush boarder enzymes
- maltase breaks down disacharride into monosacharide
- sucrase disacharride into monosacharide
- lactase disacharride into monosacharide
Protein brush boarder enzymes
- dipeptidase: cuts peptide bond between 2 amino acids (2-1 amino acid)
- carboxypeptidase: removes from carboxyl end of amino acids
- aminopeptidase: removes amino acids from amino end of of polypeptide chain
- Enterokinase: from pancreas, activates trypsin enzyme
- phosphatase: removes phosphate group from DNA/RNA in food. breaks down NAs
intestinal glands/crypts of lieberkuhn
small glands on small intestine floor between villi that have microvilli in mucosal layer.
intestinal gland properties
1-2L intestinal juice/day secreted
pH 7.4-7.8 slightly alkaline
intestinal gland cells
- goblet cells: secrete mucous
- enteroendocrine cells: secrete digestive hormones: secretin, cholecytokinin and gastric intestinal peptide (GIP)
- Paneth cells: antibacterial, secrete lysozymes and can phagocytize
IN small intestine
Pancreas cells are primarily for
99% for digestion enzymes
which part of the pancreas is closest to the duodenum
the head
Pancreatic juice amount and pH
1L/day
pH 7.2-8.2
pancreatic juice contains
- sodium bicarbonate: buffers HCl of chyme. reason for pH 7.2-8.2
- Pancreatic amylase: digest amylose portion of starch/carb
- protien break down enzymes: trypsinogen, chymostpsinogen, carboxypeptidase
- lipase: break lipids
- DNAse/RNAse: Nucleic acid break down
protein break down enzymes in pancreatic juice
- trypsinogen: turns into trypsin by enterokinase in brushborder. cut C term of amino acids lysine and arginine
- chymotrypsinogen: activated by trypsin cut C term of aromatic amino acids: phenylalanine, tyrosine, tryptophan
- carboxypeptidase in brush border: removes amino acids from carboxyl term of polypeptide
hepatopancreatic ampulla
Ampulla of Vater: opens into the major duodenal papilla through the sphincter of Oddi
in the head of the pancreas where pancreatic duct joins common bile duct mixes bile and pancreatic juice together
accessory duct for pancreas
duct of santorini: connects to minor duodenal papilla, branches off pancreatic duct before it reaches the common bile duct
how much of the liver is needed to regenerate
25% can keep working
where does the liver get its blood
75% deoxygenated from hepatic portal vein sys
25% from hepatic arteries
Liver functions
- secrete bile. emulsifies to break down fats so pancreatic lipase can break it down to triglycerides
- carbohydrate regulation: liver converts access glucose from hepatic portal sys to glycogen for later
- lipid metabolism: regulates cholesteral and triglycerides in blood. low and high density lipoproteins can be modified by the liver to affect levels in blood
- protein metab: production of plasma protiens: albumin, clot factor, angiotensinogen
- processing/detox drugs/hormones/toxins
- vitamin storage: lipid soluble A,D,E,K,B12
- mineral storage: iron and copper
- Kupffer cells/modified WBC phagocytize bacteria
- Key role in Activation of Vitamin D into calcitriol
portal triad
branch hepatic artery and vein +bile duct that run through the liver together
how much bile can the liver make
600-1000mL/day
bilirubin
bile pigment made from recycled hemoglobin molecules. bacteria in intestines can metabolize bilirubin into urobilinogen. 80% urobilinogen reabsorbed in intestines and returned to liver for recycling/reuse. not absorbed is poop color
jaundice
hepatocytes not working properly: causes yellow staining of tissues in the body by free/bound bilirubin circulating in the blood not properly removed by the liver
cirrhosis
caused by hepatitis infections (inflamation of liver) some parasites can cause it, alcohol/drug abuse, chemical exposure: normal liver tissues replaced by fibrous CT or adipose and it reduces liver function
gall stones
deposits in gallbladder formed by cholesterol and inorganic salts precipitating out of solution. caused by imbalance in proportions of cholesterol and bile salt
large intestine functions
- complete absorption after the small intestine
- form poop and poop
- manufacture vitamins: K
time chyme spends in large intestine
36hrs avg. 4-72hrs
cecum
first part of large intestine: a pouch slightly bigger than most of the large intestine, can do slight storage. appendix is attached here.
ileocecal sphincter normally
partly closed
digestive reflexes
Gastroiliel
haustra
gastrocolic
gastroiliel reflex
triggered by food in stomach
stimulates release of hormone gastrin and minor iliuj activity. iliocecal sphincter relax and move contents of the ilium into the large intestine to make room for new meal to move into the small intestine
haustra reflex
3-12 contractions/min
churning: when 1 haustra fills up and contents pushed into next haustra. mixing happens as this occurs aka colonic peristalsis
gastrocolic reflex/mass peristalsis
triggered by food in stomach causes mass movementof colon content. about half colon content starting in the transvere colon will move toward rectum. stronger reflex in babies and small children.
microflora in colon
over 800 species
density is 10^11bacteria/gram
microflora in colon
10^3/gram density
bacterial flora functions
- intestinal gas production: Hydrogen, CO2, nitrogen, methane produced due to fermentation of bacteria on foods in the colon. they digest things not digested in small intestine
- decompose bilirubin into urobilinogen to be recycled
- vitamin synthesis: Vitamin K, b-complex vitamins. most vitamin absorbed is made by colon microflora like e-coli and some b complex vitamins
- immune health: c diff requires poop transplant because the bacteria went bad
feces are made of
30% bacteria
30% fiber
10-20%fat
the rase is proteins in mucus, some salts, epithelial cells, water, urobilogenin
water in digestive tract
1L saliva+2L gastric juice+1L bile+2L pancreatic juice+1L intestinal juice=9L
8L water reabsorbed by small intestine
1L almost water reabsorbed by large intestine
100mL ends up in poop
Vitamins
- A: retinal for vision
- D: dietary calcium absorption. liver/kidney convert it into hormone calcitrol that aids in Calcium ion absorption in digestive tract
- E: antioxident inactivates O2 free radicals, byproducts of aerobic metabolism
- K: important for clotting factor bacteria in large intestines make it and from foods:
- C:for collagen synthesis, acts as antioxidant, enhances absorption of iron ion and aids in immune functions
- B12; absorbed w/ aid from intrinsic factor . needs to e active transport because of its size b12 needed for hemoglobin synthesis
- water soluble vitamins absorbed by simple diffusion not stored need a regular supply
Dietary minerals
absorbed along small intestine. if doesn’t need will be excreted through kidneys in the urine
1. Iron absorbed in proportion to body needs: need for hemoglobin. active transport
2. calcium: absorbed in proportion to body needs: bone strenght and blood clotting. need for muscle contraction and nerve conduction
3. potassium ions: needed for action potential generation in muscles and nerves
4: sodium: water balance, muscle and nerve impulses
5. sulfer: some hormones
6. Magnesium: muscle and nerve function
7. Cl- ion: acid base balance in blood/cloride shift and HCl in the stomach
8. Iodine: for thyroid hormone
gastrin
gastrin: made by G-cells in gastric pits triggers gastroileal reflex
1. triggered by stomach distention and food into stomach.
2. can be stimulated by partially digested protein and caffeine in stomach.
3. high pH promotes gastrin secretion.
4. dilutes HCl cuases pH to rise
5. Gastrin increases can cause increase of HCl secretion from parietal cells and increase of pepsinogen secretion from chief cells.
6. causes gastroesophageal sphincter to contract to protect against GERD.
7. increases motility of stomach contractions and relaxes pyloric sphincter.
Secretin digestive hormone
made by enteroendocrine cells in small intestines
1. triggered by acidic chyme in duodenum
2. increases pancreatic juice secretion rich in bicarbonate to neutralize acidic chyme.
3. causes increase in bile and intestinal mucous secretion
CCK: cholecystokinin
digestive hormone made by enteroendocrine cells in small inestine
1. stimulated by fatty chyme in duodenum
2. decreases gastric motility/regulates activity
3. increases secretion of pancreatic juice rich in digestive enzymes
4. increase bile ejection from gallbladder because of the fatty chyme
5. relaxes sphincter of Oddi to allow pancreatic juice mixed with bile to enter the duodenum
neural rgulation of digestive secretion/motility
1: cephalic phase of digestion: see/smell/think of food receptors in head trigger hypothalamus and medulla oblongata to send signals to stomach and begin secreting in anticipation of food
2. Gastric phase: actual presence of food in stomach. distends and mechanoreceptors send signal to medulla which sends signal to plexus of auerbach to increase peristaltic waves and increase gastric juice flow so basically stomach increases activity and secretion when food enters. when stomach no longer distened, gastric phase turned off by negative feedback
3. Enterogastric reflex (gut-stomach): food enters duodenum causing extension. signal via vagus nerve to medulla then to stomach to inhibit gastric secretions and motility to slow down movement of food from stomach into the duodenum.
Pernicious anemia
insufficient B12 normally insufficient intrinsic factor to absorb b12
signs/symptoms: tired, pale, cold intolerance.
B12 needed for RBC maturation. intrinsic factor only stomach function essential for life
Lactose intolerance
undigestive lactose in ilium digested by colon bacteria produce gas grom fermentation and can cause diarrhea
ulcers
associated w/ bacterium helicobacter pylori
digestive/mucous lining damaged by helicobacter pylori and stomach acid/enzymes damage stomach lining. bacteria invace stomach lining causing open sore in stomach.
so foods high in amino acids tryptophan and phenylalanine most potent stimulators of secretion of gastrin/HCL so it hurts more. usually PPI for medication
hydrolysis
breakdown of molecules split by water.
sugar split in half with water ion on the ends: 1 side keeps Hydrogen ion and other keeps hydroxide.
involved in nutrient/carb/protein/lipid breakdown
Carb/polysaccharide digestion. into glucose/glactose/fructose
- mouth salivary amylase starts starch breakdown
- bolus from esophagus to stomach
- low stomach pH inactivates salivary amylase. slow process because salivary amylase keeps working until HCL hits it when bolus breaks up
- No direct digestion of carbs happens in the stomach
- passes into duodenum where starch digestion happens: pancreatic amylase cuts amylose chains to di/trisacharids. amylase can’t break branch points of carbs
- brush border enzymes: lactose, maltose, sucrose break down disach into monosacharrides
- monosach allows for absorbtion by facilitated diffusion: fructose or cotransport with sodium ions (glucose and galactose) into absoptive cells in small intestine.
- exit absorptive cells into enteric blood cap by facilitated diffusion. monosachar too big for simple diffusion
9 most go through hepatic portal sys to liver where excess monosach removed for storage
Protien digestion
- No mouth digestion
- stomach begins protein digestion process. pepsinogen activates into pepsin and digests proteins. HCl denature/unfolds proteins so pepsin can break it down
- smaller proteins enter duodenum where gastric juice enzymes trypsin (basic amino acids) and chymotrypsin (aromatic amino acids) break down the middle of polypeptide chain
- brush border enzymes. carboxypeptidase, aminopeptidase, dipeptidase cutup the amino acids
- amino acids absorbed primarily by simple diffusion few by active sodium transport and diffuse into capillaries
- few di/tripeptides can be absorbed by cells and broken down to individual amino acids before going in the blood
