physiology Flashcards
4 functions of the digestive system
digestion, secretion, absorption, motility
what type of connective tissue is the submucosa
thick irregular connective tissue
what are the two nerve plexuses in the submucosa
myenteric and submucosal plexus
what nerve contributes to sympathetic control of the digestive system
splanchnic nerve
what are the two types of starch called
a amylose and amylopectin
what is transported when glucose and proteins are absorbed by co transport and why
water because an osmotic gradient is created
what is the transporter that cotransports glucose and NA
SGLT1
what is the transporter that transports fructose across the apical membrane
GLUT 5
what is the transporter that transports carbs across the basolateral membrane
GLUT 2
what are the 2 types of exopeptidase
aminopeptidase and caboxylpeptidase
how are di/tripeptides transported across the apical membrane
NHE3 pump pumps H+ ions out into the lumen and NA ions into the cell then PEP T1 transporter cotrasnports dipeptides with the H+ ions in
what are micelles made of
bile salts, phospholipids, fatty acids, monoglycerides
what happens to fats when they cross the apical membrane
reassembled in the smooth ER to triglycerides and coated in amphiphatic protein to stop reagregation then transported to the Golgi. here they leave the cells as chylomicrons and enter the lacteals
why do chylomicrons enter lacteals and not the blood
can’t pass through the endothelial cells tight junctions
what does iron bind to if not absorbed into the blood
ferritin
what does iron bind to in the blood
transferrin
what is vitamin B12 needed for
to mature blood cells
what are the two classes of vitamins
water soluble and fat soluble
what are fat soluble vitamins
A, D, E, K
what are water soluble vitamins
B group, C, folic acid
what are the three layers of the muscularis externa in the stomach
oblique, longitudinal, circular
what is saliva composed of
water, mucins, amylase, electrolytes, lysozymes,
what are the 3 salivary glands
submandibular, sublingual, parotid
what does parasympathetic control of saliva lead to
watery solution
what does sympathetic control of saliva lead to
thick mucous- lots of mucous (a1 ) and amylase (b2)
what occurs in the oral phase of swallowing
tongue pushes the bolus to the back of the mouth
what occurs in the pharyngeal phase of swallowing
soft pallete covers nasopharyngeal opening, epiglottis goes over, pharynx muscles contract
what is the final phase of swallowing
oesophageal phase
function of the stomach
produces intrinsic factor, dissolve food, sterilise food, mix up food,
how are the exocrine glands arranged in the pacreas
arranged in lobules that are composed of acinar cells and duct cells. lobules- intercalated ducts- interlobular ducts, interlobular ducts, main pancreatic ducts
what are the electrical impulses for peristaltic waves conducted through
gap junctions in the longitudinal muscle layer
what causes the BER to surpass threshold
gastrin, distension of the stomach causes long/short reflexes, if there’s fat in the duodenum it reduces contractions
what are enterogastrones
hormones released from glands in the duodenum (secretin and cck) they act to inhibit gastric acid secretion and gastric emptying.
what regulates the secretion of acid
parasympathetic- ACh, gastrin, prostaglandis, histamine
how is acid neutralised in the duodenum
by bicarbonate released from brunners glands. bicarbonate binds with HCL which forms carbonic acid which breaks down to water and CO2
what stimulates the release of bicarbonate from brunners glands
secretin and acid arriving in the stomach causes long and short reflexes
what is secretin released from
S cells
what are the septa
the branches of connective tissue that forms the hexagonal lobules
what is bile made of
bile pigments, bile acid, lecithin, cholesterol, toxic metals, bicarbonate
what are bile pigment s
break down products of haemoglobin- bilirubin
what are bile acids
made in the hepatocytes from cholesterol, when joined with glycine and Taurine they become soluble (bile salts)
what is different about the histology of the gall bladder
no submucosa
what two ducts join to form the bile duct
common hepatic duct and cystic duct
how does the secretion of CCK affect the secretion of bile
causes sphincter of oddi to relax and the gall bladder to contract
what are the blood vessels in the liver called
hepatic sinusoids
role of the large intestine
reasbsorb water, vitamin K production, digest short chain fatty acids,
what causes the start of the defecation reflex
parasympathetic causes MMC which push the material to the rectum this causes it to distend. the distension triggers the reflex
how is water secreted into the large intestine
chlorine is released from the crypts, which causes water to go into the lumen too
how does chlorine enter the crypts
enters via Na/K/cl channel in basolateral membrane and leaves via chlorine channel in apical membrane
what initiates the MMC
hormone- motilin
what is the ileoceacal relfex
gastric emptying causes an increase in segmentation, this triggers the opening of the ileocaecal valve so chyme enters the colon and causes distension this then causes the valve to close
what cells produce mucus in the intestine
goblet cells
symptoms of constipation
headaches, nausea, loss of appetite, abdominal distension
what are enterotoxic bacteria
bacteria that produce enterotoxins, these maximally turn on cl secretion, by elevating second messengers so too much water enters the intestine
what are enterokinases
the enzyme bound in the brush border which converts trypsinogen to trypsin
