Chapter 65 - Guyton Flashcards
The chemistry of digestion is simple because, in the case of all three major types of food, the same basic process of ________ is involved.
hydrolysis
Major carbohydrates in the diet.
sucrose, lactose, starches
ptyalin
alpha-amylase (secreted mainly by the parotid gland)
Represents more than 80% of the final products of carbohydrate digestion.
glucose
What is the importance of pepsin in protein digestion?
it can break down collagen, the primary binding constituent of intracellular connective tissue of meats
Within 15-30 minutes after the chyme empties from the stomach into the duodenum and mixes with pancreatic juice, virtually all the ___________ will have become digested.
carbohydrates (pancreatic juice has high amylase which will complete CHO digestion)
Lactose
glucose + galactose
Sucrose
glucose + fructose
Maltose
glucose + glucose
Where are lactase, sucrase, and maltase located?
in the enterocytes covering the intestinal microvilli brush border
Most protein digestion occurs under the influence of proteolytic enzymes from pancreatic secretion..where does this occur?
in the upper small intestine, in the duodenum and jejunum
This enzyme is important in the final stage of protein digestion occurring in the cytosol of the enterocyte (cleaving the tripeptides and dipeptides into amino acids).
peptidase
Most abundant fats of the diet.
triglycerides
Perform the detergent function for the digestion of fats.
bile salts and lecithin
The most important enzyme for the digestion of triglycerides.
pancreatic lipase
The bile salt _______ act as a transport medium to carry the monoglycerides and free fatty acids to the brush borders of the intestinal epithelial cells.
micelles
valvulae conniventes (or folds of Kerckring)
increase the surface area of the absorptive mucosa of the small intestine
Which three structures increase the absorptive surface area of the mucosa.
folds of Kerckring, villi, microvilli
Water is transported through the intestinal membrane entirely by?
diffusion
When a person becomes dehydrated, this hormone is secreted and greatly increases sodium (and water) reabsorption throughout the intestinal tract.
aldosterone
Bicarbonate secreted by the intestinal membrane is often exchanged for absorption of which ion?
chloride
This hormone activates vitamin D and then vitamin D causes increased calcium absorption.
parathyroid hormone
Glucose is actively transported inside the cell by what mechanism?
sodium co-transport
Fructose and a few amino acids do not require sodium co-transport but instead are absorbed through which mechanism?
facilitated diffusion
How are short and medium-chain fatty acids absorbed?
direct diffusion of these short-chain fatty acids from the intestinal epithelial cells directly into the capillary blood of the intestinal villi (do not require lymphatics)
How are triglycerides ultimately absorbed?
micelles to get into cells then released in the form of chylomicrons through the base of the epithelial cell, to flow upward through the thoracic lymph duct and empty into the circulating blood
The primary function of the proximal colon versus distal?
absorption; storage
Absorption of sodium and chloride ions creates an osmotic gradient across the large intestinal mucosa, which in turn causes absorption of?
water