Lecture 4 Flashcards
what are Enterocytes:
epithelial cells in the crypts, located in between the villi continuously undergo mitosis
Important for nutrient absorption and to provide a barrier that prevents bacteria from entering the bloodstream or the lymphatic system
how often is Enterocytes, layer of cells renewed
every 3-5 days,
what are the hair like structures of the Enterocytes called
brush border
(where digestive enzymes are mostly found)
Glycocalyx:
glycoproteins that maintain a stable environment for the enzymes to hold onto
Enterocytes filter the nutrients depending on the type, If the nutrient is water soluble:
If the nutrient is water soluble, it enters capillaries which drain to the portal vein
which drains towards the liver (liver is the first organ that sees what is coming from digestion)
Nutrient → enterocyte → water soluble → capillaries → portal vein → liver
Enterocytes filter the nutrients depending on the type, If the nutrient is fat soluble:
If the nutrient is fat soluble, it enters the lymphatic system
Fat soluble → lymphatic system
Liver function:
Produces bile
Is bile acidic or alkaline
alkaline
(pH about 7.6-8.6)
bile composed essentially of…
bile acids, salts, cholesterol, phospholipids, and pigments and bilirubin/biliverdin
what are bilirubin and biliverdin
waste products of hemoglobin degradation
- these are byproducts of the breakdown of RBCs; have a lifespan of about 3 months
what make up 80% of the body’s total bile acids
Chenodeoxycholic and cholic acids
when Bile acids conjugate with amino acid glycine it produces what
glycocheno-deoxycholic and and glycocholic acids
when Bile acids conjugate with taurine it produces what
taurocholic
taurodeoxycholic
taurochenodeoxycholic acids
When bile acids conjugate with sodium and potassium, what does it produce
bile salts
function Bile Acids/Salts:
1.Detergents that emulsify large fat globules by fractionating them into small lipid droplets
-
Also serves to eliminate substances that cannot be excreted through the urine; ex. bilirubin - it binds to albumin in the circulation, but it is excreted in
the faeces when released into the duodenum
where is bile stored?
Gallbladder
How does the gallbladder know when to release bile?
As soon as acidic chyme enters the duodenum, it senses it and sends a signal (CCK is released by enteroendocrine cells/I-cells) which stimulates the gallbladder to contract and release
bile into the small intestine
Acidic chyme → duodenum → release of CCK (via enteroendocrine cells)→ gallbladder release bile → small intestine
Gallstones:
How is it formed:
result of formation:
Formed when bile becomes supersaturated with cholesterol
In-Depth explaination:
Cholesterol precipitates and provides a crystalline-like structure in which calcium, bilirubin, phospholipids, and other compounds deposit to form a ‘stone’
Causes inflammation in the gallbladder and may also block the flow of bile (choledocholithiasis) into the duodenum or clog the pancreatic duct and
cause pancreatitis
We don’t really know how the excessive formation of cholesterol occurs to begin this process of forming gallstones
what does the pancreas release
Releases pancreatic juice containing bicarbonate (to buffer acidic product), electrolytes, and digestive enzymes
How does the pancreas know how to release pancreatic juice?
As soon as acidic chyme enters the duodenum, it senses it and sends a signal (CCK is released by
enteroendocrine cells/I-cells) which stimulates the
pancreas to contract and release pancreatic juices into the small intestine
Same process as gallbladder
what stimulates pancreatic exocrine secretion
Secretin
CCK
neuropeptide substance P
vasoactive intestinal polypeptide (VIP)
present in neurons within the gut stimulate pancreatic exocrine secretions
Enzymes in pancreatic juice:
Trypsinogen, chymotrypsinogen, proelastase, and collagenase (proteases)
Enzymes in pancreatic juice (for CHO digestion):
A-amylase
Enzymes in pancreatic juice (for fat-digestion)
Pancreatic lipase and co-lipase
Whatever is not digested in the small intestine goes into the….
large intestine
chyme enters the large intestine through
ileum
Lots of bacteria in the cecum, and if there is an imbalance or they don’t function properly, this causes an infection leading to…
Appendicitis
(Appendicitis is a medical condition characterized by the inflammation of the appendix. )
path of chyme through large intestine
(look at notes on page 10 help understanding)
Ileum →
cecum →
ascending colon →
right hepatic flexure →
transverse colon →
left splenic flexure →
descending colon →
sigmoid colon →
rectum →
anal canal
what lines the large intestine
endothelial cells
Large Intestine primary function
To absorb water and electrolytes (5-7 litres of fluid per day)
Store faecal matter
Essentially dries and stores the undigested material present in the chyme
The large intestine houses more than 400 different species of bacteria that can produce…
vitamin K (anti hemorrhagic)
biotin (coenzyme for carboxylase reactions)
short-chain fatty acids (acetic, propionic, and butyric acids)
why does fibre plays a large role in bacteria
because it feeds bacteria
and these bacteria produce important molecules that play a role in our metabolism
short-chain fatty acids are derived from the fermentation of the fibre by bacteria
Composition of the Faeces (don’t really gotta remember exact numbers just remember trend)
30% bacteria
30% undigested fibres and dried components of digested juice
10-20% fat
10% inorganic matter (minerals)
2-3% protein
what are Probiotics
Bacteria that promote health and lowers risk of colon cancer, reduce cholesterol and BP, and support immune function and weight control
what foods contain Probiotics
dairy, soy, yogurt, and dietary supplements
what are Prebiotics
non-digestible substances that promote the growth and activity of beneficial microorganisms, such as bacteria, in the gastrointestinal tract
what is food for bacteria in digestive system
Fibre (food for bacteria and allows their proliferation and survival in large intestine)
