GI Flashcards
food is required to the body for?
production of energy
repair of tissues
protein and carbs provide how many clas of energy to the body?
4 cal
lipids provide how many cals of energy?
9 cal
alcohol provide how many cals of energy?
7 cal
an average human being consumes how much solid food and liquid?
1 kg of food and 1-2 liters of fluid
women consume — cal per day
1.6-2.4 kcal
men consume how many cal per day?
2-3 kcal
what is the alimentary canal?
its a continues tube stretching from the mouth to anus
what is the function of the GI system?
ingestion
digestion
absorption
propulsive movement
secretion
host defense
elimination
what is propulsive movement?
its peristalsis movement which a food moves at a rate optimal for digestion and absorption
peristalsis moves the bolus forward
what type of secretion happen in the GI?
water
salt
electrolyte
digestive enzymes
what does elimination do in the GI?
it removes indigestible remains and hydrophobic substances
what is host defense?
means the GI system has its own immune system
what is the defense mechanism found in the oral cavity?
IgA and lysozyme
what is the immune tissue found in the stomach?
Hcl and pepsin which have bactericidal effect
what is the immune tissue found in the small intestine?
payers patch which is a lymphoid tissue that differentiate into B cells and T cells that produce anti bodies
major source of antibody production
GI in fluid balance
its responsible for fluid balance of circulatory system in systemic and any factor that affects the fluid balance of the GI has direct effect on disturbing the circulatory system
how much secretions in the GI lumen daily?
7 liters of fluid are secreted and 2 liters of water is drank daily
so 9 lit is added into GI daily
how much liquid is absorbed by the GI daily?
7.5 liters of water absorbed from the small intestine
1.4 from the large intestine
how much fluid is excreted by the GI daily?
only 50- 100 ml of fluid
list the functional layers of the GI
mucosal
submucosal
muscularis externa
serosa
what are the 3 layers of the mucosal layer?
epithelium
lamina propria
muscularis mucosae
the epithelium is made from
columnar or stratified squamous cells and it covers the lumen of the GI
the epithelium covers
fibrous in esophagus
and serous in most of GI tract
____have lots of foldings
mucosal layer
the lamina propria contains?
capillaries which are responsible for micro exchange for absorption
lymph nodules for immunological defense
the muscularies mucosae?
is a thin layer of smooth muscle which have 2 longitudinal and circular
it changes the degree of folding in lumen as it contracts and relaxes
the submucosa contains?
contains large blood vessels, glands and nerve fibers
the submucosa also have___ which control GI secretions
high neural plexus which control blood flow and GI secretions
whats the nerve plexus found in submucosa called?
messiners plexus or submucosa plexus
where is the messiners plexus located?
between sub mucosa and circular smooth muscles
what is muscularis externa ?
smooth muscle of the GI which contains circular and longitudinal layers
____ is found between the layer of the muscularis externa( longitudinal and circular)
myeinteric plexus
myeinteric plexus is responsible for?
to control motility of the GI
contraction of the circular muscles will…
decrease the lumen
contraction of the longitudinal muscles will…
decrease the length of the GI tract
what is the serosa?
its the outer layer which contains connective tissues which are fibro-serous covering
its a protective layer
what are the voluntary segments of the GI?
mouth, tongue, upper 1/3 of the esophagus and external anal sphincter
what are the involuntary segments of the GI?
GI smooth muscles which are visceral or unitary type of smooth muscles
what do GI smooth muscles exhibit?
they show functional syncytium meaning stimulation of the smooth muscles at one point will result in synchronous excitation
the individual cells work with adjacent cells for coordinated action. Rapid transmission of electrical impulses transfers between cells to trigger simultaneous contraction
GI functions are controlled by?
intrinsic mechanisms and extrinsic mechanisms
intrinsic mechanisms are?
enteric nerve system
extrinsic mechanisms are?
ANS and hormones
___is similar to the pacemaker cells of the heart
enteric nerve system
enteric nerve system is composed of?
messiners and myeinteric plexus
which ANS increase the GI function: sympathetic or parasympathetic?
parasympathetic
___is also known as the little brain of the GI and why?
enteric nerve system and its because it can act independently and control local reflexes
what are the 2 types of the GI motility?
segmentation and peristaltic movements
what is segmentation?
also known as mixing movement that occurs in the small intestine and it mixes food with digestive juices
segmentation last about
it lasts only 5-30 sec
how does segmentation happen?
it involves local ring like rhythmical contraction and relaxation of the gut in short and regular intervals
what is the use of segmentation?
it provides an increase in surface area for mixing of digestive juices with chyme
during segmentation there occurs a peristalsis, true or false
false
what is peristaltic movement?
is a progressive wave of strong contraction preceded by relaxation and it moves the bolus forward
what is receptive relaxation?
occurs in peristalsis and its where the muscular walls ahead of the ring relaxes
what stimulates peristalsis?
distension or stretch of the gut wall
which nerve plexus and nerve is responsible for coordination of peristalsis?
myenteric plexus and vagus nerve
propulsive segment happens when?
longitudinal muscle relaxes and circular muscle contracts
receiving segment happens when?
when longitudinal muscle contracts and circular muscle is inhibited
which neurotransmitter affects contraction in the GI?
Ach
which neurotransmitter is responsible for the relaxation of the GI?
NO or nitric oxide
what are the 2 principal control mechanisms involved in the regulation of GI?
neural and hormonal( endocrine and paracrine)
what are the 2 principal control mechanisms involved in the regulation of GI?
neural and hormonal( endocrine and paracrine)
neural control of GI involves?
somatic and the ANS
innervations of the digestive tract controls?
muscle contraction
secretion
absorption
blood flow
which part of the GI tract is controlled by somatic nerves?
the upper esophagus and external anal sphincter, these are voluntarily in action
true or false: somatic nerves regulate striated muscle indirectly
false they regulate it directly
autonomic regulation other name?
extrinsic regulation
vagus nerve or CN X innervate which part of the GI?
lower esophagus
stomach
small intestine
proximal large intestine
pelvic nerve innervates which part of the GI?
distal large intestine
sigmoid
rectum
anus
ANS influence___
ENS or enteric nervous system
what are the neurotransmitters of parasympathetic nerve?
cholinergic
Ach
VIP
from where does the parasympathetic originate from?
cranio- sacral (s2-4)
what does the parasympathetic do on the GI?
excitatory function :
->increase tone of the GI
->cause strong contraction of smooth muscles of the GI
->increase motility
->increase GI secretions
at the sphincters the parasympathetic does?
it causes dilation of circular smooth muscle which is lower esophageal and internal anal sphincters
parasympathetic terminates___
the ENS ganglia
what are the neurotransmitters of the sympathetic nerve?
adrenergic
nor adrenaline
adrenaline
what does the sympathetic does on the GI?
It has an inhibitory action which causes the relaxation of the smooth muscles of the GI
it reduces intestinal blood flow
at sphincters it causes constriction of the circular smooth muscles
it originates from thoraco-lumbar region (T5-L2)
intrinsic regulation is another name for?
enteric nervous system
___ is the primary neural control mechanism of the GI function
enteric nervous system
what does the enteric nervous system produce?
many stimulatory or inhibitory neurotransmitters that enhance or block GI motility
another name for Meissner’s plexus is?
inner plexus
other name for myenteric plexus is?
aurbache’s plexus or outer plexus
enteric nervous system is composed of 2 plexus, what are they?
aurbache’s plexus and sub mucosal plexus
the myenteric plexus controls?
GI motility
the Meissner’s plexus controls?
mainly absorption
secretion
blood flow
what is the name of the hormone that control the GI?
peptide hormones
the peptides hormones that act on the GI work through?
endocrine or paracrine pathways
what’s the effect of the peptide hormones ?
motility and secretary activities of the GI
list the hormones that are released in the GI
gastrin
cholecystokinin ( CCK)
secretin
motilin
how is gastrin secreted in the GI?
secreted by the G cells of the antrum of the stomach
antrum is the lower part of the stomach
what stimulates the secretion of gastrin?
ingestion of a meal or distention of the stomach
products of proteins and gastrin releasing peptide
what is the primary action of gastrin?
stimulation of HCL
how is the CCK secreted in the GI?
secreted by the i cells of duodenum and jejunum
the CCK is secreted in response to what?
in response to fatty acids. monoglycerides, peptides and amino acids
what is the function of the CCK?
it stimulates contraction of the gallbladder to release bile salts
it relaxes the sphincter of oddi ( the muscular valve surrounding the exit of the bile duct and pancreatic duct into the duodenum)
it stimulates pancreatic enzyme secretion
inhibits gastric emptying
How is secretin secreted?
secreted by the S cells of duodenum
what’s the stimulation for the secretion for secretin?
it’s secreted in response to HCL acid in the lumen of the duodenum and also fatty acids
what is the function of secretin?
it promote pancreatic secretion of HCO3 which neutralize the acid in the small intestine
it inhibits H+ secretion by gastric parietal cells
how is motilin secreted?
it’s secreted by the upper duodenum during fasting
what is motilin function?
it increase gastrointestinal motility
when does the secretion of motilin is inhibited?
after ingestion of food
how much blood supply does GI get?
at rest 25% of the cardiac output flows the GI
why 25% of blood goes to the GI?
for absorption
the GI blood glow is called?
splanchnic circulation
what is splanchnic circulation?
it is GI blood flow which includes the gut, spleen and pancreas
what happens in splanchnic circulation?
venous blood is collected from the gut, spleen and pancreas and pass through the portal circulation and end in the liver
what happens to the blood after it pass through the portal circulation and end in the liver?
it goes into liver sinusoids then hepatic vein then will enter inferior vena cava
what is the advantage of portal circulation?
harmful agents that come with the blood are destroyed by the macrophages of the liver which are called reticuloendothelial cells or Kupffer cells
what part of the brain controls food intake?
hypothalamus
hunger and feeding is stimulated by which part of the brain?
lateral hypothalamus
the satiety feeling is stimulated by which part of the brain?
medial hypothalamus or ventromedial nucleus
____is the voluntary intake of goof and drink
ingestion
____is a part responsible for mechanical digestion of food by mastication
oral cavity
what is chewing?
it’s mixing food with saliva and lubricating it to facilitate swallowing
it mixes ingested carbohydrate(CHO) with salivary amylase and begin the CHO digestion
what is swallowing?
it’s movement of food from oral cavity into esophagus
when is swallowing voluntarily and involuntary?
first it’s initiated voluntarily because the upper 1/3 of esophagus is skeletal so its regulated by somatic nerves and the rest is smooth muscle which will make the action involuntary which is regulated by ANS via enteric nervous system or directly
the smooth muscle of the esophagus is innervated by?
the vagus nerves that synapse with myenteric neurons
swallowing reflex 3 phases?
oral phase which is the only voluntary phase
pharyngeal
esophageal
how much time does the swallowing reflex take?
8-10 secs
the swallowing reflex is first initiated by___ and how?
by the tongue and it pushes the bolus against soft palate and back of the mouth triggering the swallowing reflex
which part of the brain has the swallowing reflex center?
medulla oblongata
what happens in the pharyngeal phase?
the medulla oblongata stimulate the closure of the nasal and tracheal opening and cause inhibition of respiration
upper esophageal sphincter relaxes while epiglottis closes to keep swallowed material out of airways
what causes the esophageal phase?
caused by the stimulation of solid food on the walls of the esophagus
what happens during the esophageal phase?
upper esophageal sphincter closes and creates a pressure powerful enough to push the bolus down the stomach
food moves downward into the esophagus propelled by peristaltic waves and gravity
true or false: at rest upper and lower esophageal sphincter are opened?
false, they are closed and there is no backflow if gastric contents unless we are vomiting or belching( burping)
what are the 2 types of protein secretions of saliva?
serous secretion
mucous and immunoglobin secretions
what is serous secretion?
watery secretion that contains alpha amylase which is the dissolved zymogen granules
mucous and immunoglobin secretions contain?
protein mucin that helps with lubrication, surface protection and anti bacterial effect
list the constituents of saliva
water 99.5%
electrolyte like Na+, Cl_, K+, HCO3, Iodine…
enzymes like salivary amylase, lingual lipases, lysozymes, IgA, mucus…
how much saliva we produce a day?
1-1.5 liters
list the salivary glands
parotid gland
submandibular
sublingual
what is the parotid gland?
it secrets mainly serous or watery fluid that is rich in ptyline which is amylase dissolved zymogen granules
what is ptyline?
ptyline is salivary amylase
the parotid gland is supplied by?
inferior salivary nucleus
submandibular gland produce?
both serous or watery fluid and mucous fluid but no zymogen granules
sublingual gland produce?
secret mainly thick mucous with little serous fluid
what does the superior salivary nucleus supply?
both sub mandibular and sub lingual glands
list the function of saliva
digestion
protection
speech facilitation
secretes HCO3
lubrication
oral hygiene
solvent for taste stimuli
what is the digestion function of the saliva?
CHO digestion begins in the oral cavity by saliva
how does saliva digest CHO?
by ptyline which breaks starch to maltose
also has lingual lipase which hydrolyze triglycerides
what is the protection function of saliva?
it contains lysozyme and IgA that kills microbes
why does profuse salivation occurs before vomiting?
the saliva protects the esophageal mucosa from corrosive action of HCl and chyme
what is HCO3 function in the saliva?
its useful to make neutral media in the oral cavity and this is useful for ptyalin or salivary amylase action which is used for CHO digestion cause it does not work under acidic condition
what is the lubrication function of saliva?
mucin is found in the saliva which facilitates moistening in the mouth
explain the reflex control of salivation
Smell, test or touching of food ⇓
Activation of receptors in the oral (nasal) cavity
Sensory fibers from the tongue & nasal cavity send impulse to the nuclei in brain stem medulla oblongata, so called salivatory nuclei
Activation of parasympathetic fibers –act on salivary glands to increase salivary secretion
✓ Salivation can also be controlled by higher centers like hypothalamus appetite center which has nerve connections with salivatory nuclei in the medulla oblongata also involved in reflex control of salivation.
secretion in the esophagus?
mucous glands secrete mucus which provide lubrication to facilitate swallowing and protect it from HCl during reflux
list disorders of esophagus
gastro esophageal reflux disease or heart burn
achalasia
heart burn occurs when?
when the cardial sphincter remains open or incompetence of the lower esophageal sphincter and this cause acid reflux in the lower esophagus causing a sensation of hurt burn
achalasia occurs when?
when the lower esophageal sphincter remains closed and contracted and this will result bad smell and dilation of esophageal walls
list the 3 functional regions of the stomach
fundus
body
antrum
list the functions of the stomach
storage
mixing
controlled emptying of the chyme
secretion
protein digestion
anti septic action
what is chyme?
it’s a semi fluid mixture of food with gastric secretion
how does the stomach control emptying of chyme into the small intestine?
by pylorus sphincter
list the active form of secretion in the stomach
parietal cells
chief cells
G cells
entrochromaffin cells
surface mucous cells
D cells
parietal cells produce?
HCl and intrinsic factor
chief cells produce?
pepsinogen
G cells produce?
gastrin
Entrochromaffin cells produce?
histamine
surface mucous cells produce?
mucus and bicarbonate
D cells produce?
somatostatin
what is the active form of pepsinogen?
pepsin, so pepsinogen is the inactive form
how is pepsinogen converted into pepsin?
HCl creates an acidic media in the stomach and that media is responsible for the conversion
how does the G cells produce gastrin?
gastrin is produced during parasympathetic stimulation and this gastrin is responsible for the production of HCl
protein digestion begin in?
the stomach cause of pepsin
what’s the purpose of mucous secretion in the stomach?
it prevent the effect of HCl inside the stomach lumen
___is a proteolytic enzyme
pepsin
what happens during the cephalic stage of secretion?
vagal stimulation will cause chief cells to produce pepsinogen
what happens during the gastric phase?
low PH activates pepsinogen secretion and the low PH will convert it into pepsin
explain the HCl secretion
H+ ions that result from the dissociation of H2O in the cytoplasm of the parietal cells are continuously pumped through the membrane of the gland (canaliculi) into the gland lumen
Within the cell cytoplasm CO2 and OH- combine to produce bicarbonate ions, HCO3
Cl- are transported from the blood into the parietal cell and finally into the lumen of the gland by facilitated diffusion.
HCO3 in exchange to Cl-is transported in reverse direction (from the cytoplasm into the blood, charge balance).
Finally, H+ and Cl-ions combine in the lumen of the gland (pit) and produce HCl that is collected and stored in the pit until used for different physiological functions.
gastric ulcer can develop when?
mucous layer and HCO3 production is minimized
how does mucosal layer protect the lumen from acid attach?
because epithelial cells can produce thick mucous, HCO3 secretion and form tight junction
what is gastric emptying?
it occurs when the chyme is small enough to pass through the pyloric sphincter so it’s highly dependent on the size, fluidity of the chyme
which content can move past the pyloric sphincter easily?
CHO then protein and then fat( this being the least)
which hormones facilitate and delay gastric empting?
CCK and secretin delay it by constricting pylorus
gastrin stimulates emptying by increasing stomach motility
how does parasympathetic and sympathetic affect gastric emptying?
parasympathetic increase the rate by opening the pyloric sphincter
sympathetic delay emptying by constricting pyloric sphincter
what is enterogastric reflex?
this reflex delay emptying
when fat and protein chyme reaches the duodenum sends impulses to enteric nerves of the stomach which inhibit motility and secretion
what are physiological advantage of delaying gastric emptying ?
gives time for nutrients to stay in the stomach and be digested by gastric juice
it prevents HCl to not be damped into duodenum cause this might cause duodenal ulcers
its gives time for pancreatic secretions to reach duodenum and neutralize the acid HCl
prevent overwhelming of the small intestine with chyme
what are the things that are being absorbed by the stomach?
alcohol
certain drugs like aspirin and morphine
small quantities of water
what are the things that are NOT being absorbed by the stomach?
organic nutrients like glucose, amino acids
what organ do we find adjacent to duodenum
the pancreas
the pancreas act as?
function as both endocrine and exocrine glands
list the function of the pancreas
produce digestive enzymes necessary to digest CHO, fat and protien
produce bicarbonates to neutralize gastric jucie
produce water and electrolytes like Na+ mnamn
the digestive enzymes and electrolytes are produces by the pancreas are secreted by ?
acinar cells of the pancreas
HCO3 and water are produces by the pancreas are secreted by ?
the cells lining the pancreatic duct cells
the acinar cell is aided to produce enzymes by which neurotransmitters?
CCK and ACh
duct cells are aided to produce HCO3 by which neurotransmitters?
secretin
secretin is released from?
acid from the stomach release secretin from the wall of duodenum and fats and amino acids cause release of CCK
enzymes are released into acini by?
vagal stimulation
secretin causes___ and CCK causes___
secretin causes copious secretion of pancreatic fluid and HCO3
CCK causes secretion of enzymes
list digestive enzymes produced by pancreas exocrine cells
amylases
protease and peptidases
lipases
nucleases
which digestive enzyme produced by the exocrine cells digest proteins and peptides?
protease and peptidases
which digestive enzyme produced by the exocrine cells digest carbohydrates?
amylases
which digestive enzyme produced by the exocrine cells digest fats?
lipases
which digestive enzyme produced by the exocrine cells digest nucleic acids?
nucleases
pancreatic protease include?
chymotrypsin
trypsin
carboxypeptidase
which protease enzyme protein to polypeptides?
chymotrypsin and trypsin
which pancreatic enzyme splits polypeptides to amino acids?
carboxypeptidase
which pancreatic enzyme is secreted in it’s active form?
pancreatic amylase and pancreatic lipase
pancreatic amylase digest all carbohydrate except?
cellulose
which compounds are changed to disaccharides by pancreatic amylase?
glycogen and starch
___is secreted in its active form and it digests fat
pancreatic lipase
what is the inactive from of trypsin?
trypsinogen
trypsinogen is converted into trypsin by?
enterokinase
what is the inactive form of chymotrypsin?
chymotrypsinogen
chymotryspinogen is converted to chymotrypsin by?
trypsin
acinar cells are filled with what?
secretary granules that contain different inactive protein proenzymes
the acinar cells of pancreas must produce inactive pro enzymes because?
in order to avoid self destruction of its own tissues
what does the pancreas do to avoid premature activation of proenzymes?
the acinar cells secrete trypsin inhibitor to inhibit the conversion of trypsinogen to trypsin
what stimulates pancreatic secretion?
when fat food and HCl reach the duodenum evoke secretin and CCK secretion
how does secretin stimulate pancreatic secretion?
secretin stimulates duct cells and produce large no of pancreatic juice that’s reach in bicarbonate
how does CCK stimulate pancreatic secretion?
by stimulating acinar cells to release digestive enzymes
what the significance of pancreatic enzyme secretion by CCK in small intestine?
digestion of fats and protein in small intestine
what the significance of pancreatic bicarbonate secretion by secretin in small intestine?
neuralization of intestinal acid
what is CCK role in gallbladder?
contraction
what is CCK role in pancreas?
acinar secretion
what is CCK role in stomach?
reduced emptying from the pylorus to small intestine
what is CCK role in sphincter of oddi?
relaxation
what’s the overall function of CCK?
protein, carbohydrate and lipid absorption and digestion
matching of nutrient delivery to digestive and absorptive capacity
what is the function of liver in GI?
detoxify and eliminate toxins, drugs and metabolites
storage, metabolism and release of nutrients and some vitamins
synthesis of biologically important plasma protein like albumin, prothrombin clotting factors and apolipoproteins
synthesis and secretion of bile that optimizes the absorption of fats
role in immune function and clearance of intestinally absorbed bacteria
the liver receives___ blood from the intestine
venous blood
the digestive and excretory function of the liver are associated with____
the secretion of bile via the biliary tractthe secretion of bile via the biliary tract
what are general features of bile?
it’s an alkaline fluid with Ph 8 that’s secreted in the liver
have bitter taste
dark green to yellowish brown fluid
250-1500 ml secreted daily
where is bile stored? and when is it discharged?
stored in gallbladder during inter digestive period and discharged into duodenum during eating
what are the constituents of bile?
bile salts or acids
bilirubin (bile pigment)
cholesterol, lecithin and protein
electrolytes
water, 84%
what is the function of bile?
emulsification of fat and excretion of several toxic end products from the blood
how does bile emulsify fats?
by changing large droplets of fats into smaller so they can be attacked by pancreatic lipase so it helps the absorption of fat from the small intestine
what are toxic end products of blood that are excreted by bile?
bilirubin and excess cholesterol
when CCK act on gallbladder what happens?
it contracts and increases bile flow into common bile duct
when CCK acts on sphincter of oddi what happens?
it relaxes it and increase flow of bile into duodenum
how does the gallbladder store bile?
it concentrates bile by reabsorbing water and electrolyte
through what does gallbladder release bile to the duodenum?
through cystic and common bile duct
how does gallstones occur?
when gallbladder is reabsorbing bile salts, bilirubin and cholesterol it becomes increasingly concentrated and they form solid crystals and as they become larger they form gallstones
what does gallstones do?
they block the flow of bile which is known as obstructive jaundice
which part of the SI does the pancreas head fit in?
duodenum
what does duodenum mainly secretion?
mucous
hormones and
enzymes
which part of the SI does the digestion begins in full spate?
jejunum
what enters through jejunum?
bile and pancreatic enzymes
___is part of SI where vigorous digestion and absorptive function takes place
ileum
what type of diseases can develop due to fault of the SI?
mal absorption syndrome and short bowel syndrome
what innervate the SI?
enteric and vagal nerves
the inner lining of SI is greatly folded due to?
to increase the surface area for absorption
what increase the surface of SI?
the microvillus
villi
greater foldings or plica circulares
what are villi?
numerous finger like projections that emerge from the mucous membrane
where can we find brush border?
at the surface of each villi
what is brush border?
are minute microvilli, a layer of absorptive epithelial cells
the epithelial cells of villi contain?
digestive enzymes like sucrase, maltase lactase and peptidases
what does villi contain?
centrally located blood capillaries
lymphatic or lacteals
nerve fibers
connective tissues
what are enzymes secreted in the SI?
brush border enzymes
pancreatic enzymes like sucrase, maltase and lactase
intestinal lipase
peptidases
what does mucus inside the SI do?
it protects the intestinal wall and neutralize HCL
where does almost all CHO digestion occur?
in the small intestine
what digests CHO into disaccharides in SI?
pancreatic a-amylase
what digests the disaccharides into monosaccharides in SI?
intestinal brush border enzymes like maltase, lactase and sucrase
what is the end product of CHO?
fructose, glucose and galactose
explain the summary of digestion of carbohydrates?
in the mouth polysaccharides are turned into shorter chains by salivary amylase, also disaccharides are turned into sucrose and lactose and these are turned into fructose or glucose and galactose or glucose in the SI respectively
in the SI pancreatic amylase turns oligosaccharides, dextrin and maltose into glucose, here sucrase, maltase and lactase have huge contributions too
what is pepsin?
pepsinogen + H+
list brush border enzymes
aminopeptidase
carboxypeptidase and dipeptidase
explain the summery of digestion of proteins
in the stomach pepsin will turn polypeptides into shorter chains
inside SI brush border enzymes will turn shorter polypeptides and dipeptides into amino acids, here pancreatic enzymes like trypsin, chymotrypsin and carboxypeptidase also have contributions
explain emulsification of lipids and why it happens
lipids must be emulsified or broken into smaller droplets by bile acid before being digested and this is for to increase the surface area for digestion
explain the summary of digestion of fats
in the SI un-emulsified fat will get emulsified by bile from liver which is released by gallbladder and then this emulsified fat by the help of pancreatic enzyme called lipase it will turn into glycerol, fatty acids and monoglycerides
what happens after vigorous digestion and absorption in the SI?
the remnants live and enter the large intestine and they are water insoluble
list functions of the LI
absorption of water from the slurry and convert it into feces
electrolyte absorption mainly NaCl
mucous and bicarbonate secretion
storage, transport and evacuation of feces
absorption of vitamins and some drugs like aspirin
microbial fermentation
what is microbial fermentation in LI?
the microbes in the colon synthesis vitamin K and B groups
what are common diseases of LI?
colorectal cancer
appendicitis
constipation
what are the 2 movements of colon?
haustrations and propulsive movement
what is haustrations?
its a mixing movement of contractions that occur slowly and this will roll fecal matter and help expose it to the mucosal surface of the colon
what is the importance of haustrations?
promotes efficient absorption of fluid and electrolyte from the colon
what is mass or propulsive movement?
its produced by slow and continues haustral contractions and modified by peristaltic actions and this forces feces into rectum and the desire for defecation occurs
when does mass movement occur?
1-3 days or once after a breakfast
explain defecation reflex?
first pressure in rectum from mass movement sends afferent stimuli to spinal cord
parasympathetic stimuli cause contraction of rectal muscle and relaxation of internal anal sphincter
voluntary stimuli relax external sphincter and cause abdominal contraction
____moves external anal sphincter during defecation
voluntary motor neuron
what is the composition of feces?
normal feces have 75% water and 25% solid
what is the bulk of fecal solids?
bacteria and undigested organic matter and fibers or cellulose
what causes the brown color in feces?
due to urobilinogen produced by bacterial degradation of bilirubin
what causes the odor in feces?
results from gases produced by bacterial metabolism like skatol, inodle and hydrogen sulfide
