Part 4.6: Digestion Flashcards
Hepatic portal vein containing blood from the gut flows across the sinusoids and then the ___ __
central vein.
hepatocytes dump bile into the ___ ___
bile canalculi
components of bile
bile salts, cholesterol, lecithin
purpose of bile
assists in fat digestion by emulsifying larger fat droplets in aqueous environment of duodenum. emulsifying larger fat droplets into smaller micells increases surface area for lipase.
bile salts have a ____ soluble end and a ____ soluble head. Outline the general structure of a bile salt.
bile salts have a LIPID soluble end and a WATER soluble head.
_____ breaks up triglycerides into monoglycrerides and hydrophobic fatty acids, but they still need to be absorbed. Normally, they would float on top of aqueous chyme. How does bile prevent this?
bile helps to form MICELLES, which are a milion times smaller than emulsified fat droplets that have a water solbule surface but a LIPID SOLUBLE CORE. allows the fat to be absorbed. also allows some fat soluble vitamins to be absorbed too.
opening of the bile duct into the duodenum is controlled by the ___ ___ ___, and is stored in the ____ until this opens.
controlled by SPHINCTER OF ODDI, and is stored in the gall bladder.
___ released by duodenum stimulates contraction of ___ ___ and relaxation of the sphincter of ____ for bile release
CCK released by duodenum stimulates contraction of GALL BLADDER and relaxation of the sphincter of ODDI for bile release
how are bile salts retained in the body?
via enterohepatic circulation that starts in the terminal ileum. we have special transporters of bile salts back into blood in the terminal ileum, then back into hepatic portal system. Only about 5% is lost in feces.
bilirubin is derived from:
Purpose of bilirubin?
the breakdown of old red blood cells. aids in the ultimate produce of heme removal pathway. bilirubin is created by old heme by KUPFER cells.
liver necrosis or blockage of liver ducts resulting in the inability to get rid of bilirubin leads to
Jaundice. production of bilirubin is faster than it can be removed. Causes yellow color of skin and white of the eyes. normally, bilirubin moves through the sinusoids of the liver gest excreted in the urine.
4 layers to the wall of the digestive tract
1) mucosa (epithelial lining, lamina propria, muscularis mucosa) 2) submucosa 3) muscularis externa 4) serosa. + the mesentary holding things together
3 layers of the mucosa and what are their purposes?
1) mucous membrane. protective layer with sites for secretion and absorption. endocrine cells and epithelial cells. - endocrine: signalling cells -epithelial cells: typically used for absorption
2) lamina propria - connective tissue with blood vessels, lymph vessels, nerve fibers. - GALT to protect against bacteria (immune system)
3) muscularis mucosa. outer layer of smooth muscle. helps to move fat a little bit, but isn’t respondible for peristalsis.
the submucosa is made of ___ ___. Purpose of the submucosa
connective tissue. allows the intestine to be distensible and elastic.
how many layers in the muscularis externa?
2 layers of smooth muscle. - inner circular, outer longitudinal.
purpose of the serosa
connective tissue covering the digestive tract. secretes watery fluid which lubricates organs and surrounding viscera.
mesentery purpose
holds up the digestive tract like a sling. Attaches it to the peritoneum
adaptations for increasing surface area (3) for absorption
1) folding of the mucosal surface (plicae circulares)
2) microscopic villi project into the lumen
3) microvilli that project from the villi. also called the brush boarder.
how are villi dynamic in a python?
villi are dynamic because their epithelial cells can increase rate of digestion. the dynamic villi allows the intestine to increase in size. energy cost to the python= 1/2 of the energetic value of the meal just to maintain the cells.
the brushborder purpose
1) houses carriers for specific nutrients and electrolytes
2)digestive enzymes are associated ON the brushborder to complete last minute protein and carbohydrate digestion.
components of villi structure. purpose of the central lacteal?
1) capillary network 2) lymphatic vessel called CENTRAL LACTEAL, which occupies the center of the villus core. It’s important for dealing with intestinal bacteria
purpose of central lacteal in villi
important for dealing with intestinal bacteria.
after nutients get absorbed by the villi, they flow into the ____ fluid
interstitial
T/F small intestine undergoes peristalsis.
false, they undergo segmentation contraction that is much slower than peristalsis. one segment contracts while adjacent segments relax. digesta moves in both directions out of the area of contraction. improves mixing of bile and food.
