Module 7.9 Small Intestine Flashcards
The small intestine is composed of three sections:
- the _____\_,
- _____\_ and
- _____\_,
which connect the stomach to the _____\_
The small intestine is composed of three sections:
- the duodenum,
- jejunum and
- ileum,
which connect the stomach to the l_arge intestine_
- The entrance to the small intestine is sealed by the ________ ________
- the exit from the small intestine is sealed by the ________ ________ and ________
- The entrance to the small intestine is sealed by the pyloric sphincter
- the exit from the small intestine is sealed by the ileocecal sphincter and valve
The small intestine is involved in all four digestive system processes:
- ______\_,
- ______\_,
- ______\_ and
- ______\_
and is the primary site of ______\_and ______\_ in the digestive system
The small intestine is involved in all four digestive system processes:
- motility,
- secretion,
- digestion and
- absorption
and is the primary site of nutrient digestion and absorption in the digestive system
Motility in the small intestine occurs through
- the processes of _______\_
- the ___________\_
Motility in the small intestine occurs through
- the processes of segmentation
- the migrating motility complex
Segmentation involves _______ _____ of _________ muscle initiated by the ________cells of the ______\_
Segmentation involves _alternating contraction_s of circular muscle initiated by the pacemaker cells of the small intestine
The frequency of the basic electric rhythm (BER) from the duodenum to the ileum, which allows for both and of the chyme to occur through the small intestine
The frequency of the basic electric rhythm (BER) decreases from the duodenum to the ileum, which allows for both mixing and propulsion of the chyme to occur through the small intestine
Segmentation is regulated by? (3)
Segmentation is regulated by:
- distension of the duodenum
- the hormone gastrin
- autonomic system innervation
Image: Segmentation in the intestine:
Neighbouring segments of intestine alternatively and in response to waves of resulting in the back and forth mixing of .
Image: Segmentation in the intestine:
Neighbouring segments of intestine alternatively contract and relax in response to waves of contraction resulting in the back and forth mixing of chyme.
The migrating motility complex is a series of ___________ that move from the ____\_to the _____\_ in between meals
The migrating motility complex is a series of short-distance peristaltic waves that move from the duodenum to the ileum in between meals
What is the function of the migrating motility complex?
The function of the migrating motility complex is to move any remaining chyme left behind during segmentation toward the large intestine
What hormone regulates the migrating motility complex?
Regulation of the migrating motility complex occurs through the hormone motilin
Motilin, the hormone that regulates the migrating motility complex. is secreted by the ______ cells of the small intestine in the absence of _____
Motilin, the hormone that regulates the migrating motility complex. is secreted by the endocrine cells of the small intestine in the absence of chyme
What is the function of the ileocecal sphincter and valve? serve to regulate the emptying of the small intestine contents into the large intestine and to prevent bacterial contamination of the small intestine from the large intestine.
To regulate the emptying of the small intestine contents into the large intestine and to prevent bacterial contamination of the small intestine from the large intestine
Relaxation of the ileocecal sphincter is regulated by _____\_and by ____\_ of the ____\_, which triggers a short reflex pathway.
Relaxation of the ileocecal sphincter is regulated by gastrin and by distension of the ileum, which triggers a short reflex pathway.
The secretion produced by the small intestine is known as ________\_
The secretion produced by the small intestine is known as succus entericus
What is succus entericus and what is its function?
- An aqueous salt and mucous secretion
- succus entericus functions to provide protection and lubrication for the small intestine
Succus entericus is secreted proximally in the ______\_and is absorbed distally in the _____\_
Succus entericus is secreted proximally in the duodenum and is absorbed distally in the ileum
The duodenum is also the site of entry for the secretions produced by the ____\_and ____\_.
The duodenum is also the site of entry for the secretions produced by the pancreas and liver.
The apical surface of small-intestine epithelial cells contains plasma membrane enzymes, which are referred to as ____________\_.
The apical surface of small-intestine epithelial cells contains plasma membrane enzymes, which are referred to as brush-border enzymes.
The brush border enzymes include
- _______
- _______
- _______
The brush border enzymes include
- enterokinase (which activates pancreatic trypsinogen),
- disaccharidases (which are involved in the digestion of disaccharides),
- aminopeptidases (which are involved in the digestion of peptides)
What is the function of the brush border enzyme:
- enterokinase
activates pancreatic trypsinogen
What is the function of the brush border enzyme
disaccharidases
involved in the digestion of disaccharides
What is the function of the brush border enzymes
aminopeptidases
involved in the digestion of peptides
Thus, the digestion that occurs in the small intestine is the result of _____________\_, as well as ______\_ and ____\_ enzymes.
Thus, the digestion that occurs in the small intestine is the result of brush-border enzymes, as well as pancreatic and hepatic enzymes.
Most absorption of nutrients, water, and electrolytes is completed within the _____\_and ____\_ of the small intestine
Most absorption of nutrients, water, and electrolytes is completed within the duodenum and ileum of the small intestine
With the exception of ______\_and _____\_, absorption is not regulated, allowing for maximum absorption
With the exception of calcium (Ca2+) and iron, absorption is not regulated, allowing for maximum absorption
The small intestine is anatomically arranged to have a _________\_, which maximizes its absorptive capabilities
The small intestine is anatomically arranged to have a large surface area, which maximizes its absorptive capabilities
How is the small intestine anatomically arranged to have a large surface area? (3)
Large surface area is the result of the presence of circular folds, villi, and microvill
The small intestine contains circular folds, villi and microvilli which all serve to ____________and maximize ____\_ capability.
The small intestine contains circular folds, villi and microvilli which all serve to increase surface area and maximize absorptive capability.
The epithelial cells of the small intestine also have __________\_ specific for the absorption of key nutrients and minerals.
The epithelial cells of the small intestine also have transport proteins specific for the absorption of key nutrients and minerals.
Carbohydrates are absorbed as _______\_
Carbohydrates are absorbed as monosaccharides
Carbohydrates are absorbed as monosaccharides. This process involves transport across the apical surface by _______ ______ ______ _____\_transport proteins and transport across the basolateral surface by _______ _______ ______\_ proteins
Carbohydrates are absorbed as monosaccharides. This process involves transport across the apical surface by sodium (Na+)-dependent secondary active transport proteins and transport across the basolateral surface by facilitated diffusion carrier proteins
Carbohydrate digestion and absorption across the epithelial cells of the small intestine:
(1) Starch and glycogen are converted to the disaccharide maltose by ______ _____\_and ______ _____\_.
(2) The disaccharides lactose, maltose and sucrose are converted to their respective monosaccharides by the _____\_(lactase, maltase and sucrose) located in the ______ _____\_ of the _____\_ cells.
(3) Monosaccharides are absorbed into the interior of the cell by ______ ______ ___________\_and move across the basolateral surface by ______ ______ ______ _____\_. ______ _____\_located in the basolateral membrane maintain the _____ _____\_required for the apical membrane transport of monosaccharides.
Carbohydrate digestion and absorption across the epithelial cells of the small intestine:
(1) Starch and glycogen are converted to the disaccharide maltose by salivary amylase and pancreatic amylase.
(2) The disaccharides lactose, maltose and sucrose are converted to their respective monosaccharides by the disaccharidases (lactase, maltase and sucrose) located in the brush borders of the epithelial cells.
(3) Monosaccharides are absorbed into the interior of the cell by Na+-dependent secondary active transport and move across the basolateral surface by facilitated diffusion carrier proteins. Na+/K+ ATPases located in the basolateral membrane maintain the Na+ gradient required for the apical membrane transport of monosaccharides.
Proteins are absorbed across the apical membrane as:
- ____ ___\_,
- ___\_ or
- ___\_
by:
- ____ ____ ___\______ ___\__
or
- by ____ ____ ____ ___\_.
Proteins are absorbed across the apical membrane as:
- amino acids,
- dipeptides or
- tripeptides
by:
- Na+-dependent secondary active transport proteins
or
- by facilitated diffusion carrier proteins.
Intracellularly, all peptides must be catabolized to their _____ ____\_ form
Intracellularly, all peptides must be catabolized to their amino acid form
Transport of amino acids across the basolateral membrane occurs by _____ _____ _____ _____.
Transport of amino acids across the basolateral membrane occurs by facilitated diffusion carrier proteins.
Protein digestion and absorption across the epithelial cells of the small intestine:
(1) Dietary and endogenous proteins are converted to small peptides and amino acids by ____ ___\_and ____ ____ ___\_.
(2) Amino acids, dipeptides and tripeptides are absorbed across the apical membrane by ____ ____ ____ ____ ___\_.
(3) Small peptides are catabolized to their amino acid form by ___\_in the brush border of the epithelial cells or by ____ ___\_.
Transport of amino acids across the basolateral membrane occurs by facilitated diffusion carrier proteins. ___\_located in the basolateral membrane maintain the____\__ required for the apical membrane transport of small peptides and amino acids.
Protein digestion and absorption across the epithelial cells of the small intestine:
(1) Dietary and endogenous proteins are converted to small peptides and amino acids by gastric pepsin and pancreatic proteolytic enzymes.
(2) Amino acids, dipeptides and tripeptides are absorbed across the apical membrane by Na+-dependent secondary active transport proteins.
(3) Small peptides are catabolized to their amino acid form by aminopeptidases in the brush border of the epithelial cells or by intracellular peptidases.
Transport of amino acids across the basolateral membrane occurs by facilitated diffusion carrier proteins. Na+/K+ ATPases located in the basolateral membrane maintain the Na+ gradient required for the apical membrane transport of small peptides and amino acids.
Fats are absorbed as _____\_and _____\_, both of which are capable of _____\_across the ______ _____\_ of _____\_ cells
Fats are absorbed as monoglycerides and fatty acids, both of which are capable of diffusing across the plasma membrane of epithelial cells
Intracellularly, monoglycerides and fatty acids enter the _____ ______ _____\_and reform _____\_ which are then send to the ____\_appartus for packaging into ______\_
Intracellularly, monoglycerides and fatty acids enter the smooth endoplasmic reticulum (SER) and reform triglycerides which are then send to the Golgi appartus for packaging into chylomicrons
Chylomicrons are exocytosed across the basolateral membrane where they enter into the ____\_ system
Chylomicrons are exocytosed across the basolateral membrane where they enter into the lymphatic system
Fat digestion and absorption across the epithelial cells of the small intestine:
(1) Dietary fat is emulsified by _____ ____\_.
(2) _____ ____\_ converts triglycerides into monoglycerides and free fatty acids.
(3) ____\_ are formed from bile salts interacting with monoglycerides and free fatty acids.
(4) Monoglycerides and free fatty acids leave the micelle upon contact with the _____ ____\_ of the epithelial cell.
(5) Monoglycerides and free fatty acids are resynthesized into ____\_.
(6) Triglycerides aggregate and are coated with lipoprotein to form ____\_ which are exocytosed across the basolateral membrane of the epithelial cell.
(7) Chylomicrons enter the ____\_vessels called the _____ ____\_.
Chylomicrons are unable to cross the ____\_ membrane of blood capillaries.
Fat digestion and absorption across the epithelial cells of the small intestine:
(1) Dietary fat is emulsified by bile salts.
(2) Pancreatic lipase converts triglycerides into monoglycerides and free fatty acids.
(3) Micelles are formed from bile salts interacting with monoglycerides and free fatty acids.
(4) Monoglycerides and free fatty acids leave the micelle upon contact with the apical surface of the epithelial cell.
(5) Monoglycerides and free fatty acids are resynthesized into triglycerides.
(6) Triglycerides aggregate and are coated with lipoprotein to form chylomicrons which are exocytosed across the basolateral membrane of the epithelial cell.
(7) Chylomicrons enter the lympathic vessels called the central lacteals.
Chylomicrons are unable to cross the basement membrane of blood capillaries.
The small intestine is also the site of vitamin absorption. ______\_vitamins are transported in ____\_, along with monoglycerides and fatty acids, and are ____\_absorbed by ____ ____\_
The small intestine is also the site of vitamin absorption. Fat-soluble vitamins are transported in micelles, along with monoglycerides and fatty acids, and are passively absorbed by simple diffusion
Water-soluble vitamins require ___\_and ______ ______ _____\_ for absorption
Water-soluble vitamins require apical and basolateral transport proteins for absorption
Vitamin B12 is absorbed only when bound to _________\_, which is a protein secreted by the ______ _____\_ cells.
Vitamin B12 is absorbed only when bound to intrinsic factor, which is a protein secreted by the gastric parietal cells.
Unlike the absorption of nutrients and vitamins, the absorption of both ___\_and ___\_ is regulated
Unlike the absorption of nutrients and vitamins, the absorption of both iron and Ca2+ is regulated
Iron is ____\_absorbed by the small intestine epithelial cells and can be stored in a granular form called ____\_ or transported into the blood, where it binds to a plasma protein carrier called ____\_
Iron is actively absorbed by the small intestine epithelial cells and can be stored in a granular form called ferritin or transported into the blood, where it binds to a plasma protein carrier called transferrin
Iron absorption across the epithelial cells of the small intestine:
Dietary iron that can be absorbed will be:
a) moved into the ____\_, where it is transported bound to the plasma protein carrier ____\_,
or
b) stored in the epithelial cell, where it is bound to the protein ____\_.
Excess iron circulating in blood can also be moved into the epithelial cell for storage bound to ferritin.
Iron that is not absorbed by cells and that is stored in epithelial cells being sloughed is ____\_from the body in the ____\_.
Iron absorption across the epithelial cells of the small intestine:
Dietary iron that can be absorbed will be:
a) moved into the blood, where it is transported bound to the plasma protein carrier transferrin,
or
b) stored in the epithelial cell, where it is bound to the protein ferritin.
Excess iron circulating in blood can also be moved into the epithelial cell for storage bound to ferritin.
Iron that is not absorbed by cells and that is stored in epithelial cells being sloughed is eliminated from the body in the feces.
Ca2+ must bind to a ___________\_ for endocytosis into the small intestine epithelial cell
Ca2+ must bind to a brush-border calcium-binding protein for endocytosis into the small intestine epithelial cell
Ca2+ Transport across the basolateral membrane occurs by a __________\_
Ca2+ Transport across the basolateral membrane occurs by a Ca2+ -ATPase.
Ca2+ absorption is regulated by the hormones ____\_hormone and ___\_.
Ca2+ absorption is regulated by the hormones parathyroid hormone and calcitriol.
Water molecules _____\_follow the absorption of other molecules, allowing water to be absorbed _____\_
Water molecules osmotically follow the absorption of other molecules, allowing water to be absorbed passively
About 95% of the water present in the duodenum is absorbed by the time the chyme reaches the ____ ____\_
About 95% of the water present in the duodenum is absorbed by the time the chyme reaches the large intestine
