The Small Intestine Flashcards
What features of the small intestine increase its surface area?
Large circular folds
Villi
Microvilli
What is contained in the core of each villus?
Vessels
Lacteals (lymphatics)
Cells
What does the lamina propria of the small intestine contain?
Plasma cells Lymphocytes Macrophages Eosinophils Mast cells
What are the crypts of Leiberkuhn?
The spaces between the bases of the villi
Where are enterocytes formed?
At the bottom of the crypts of Leiberkuhn
What is present on the luminal side of the small intestine enterocytes?
A gelatinous layer called the glycocalyx
What are scattered between epithelial cells of the small intestine?
Mucin secreting goblet cells
Intraepithelial lymphocytes
Paneth cells
Which artery supplies most of the blood supply to the small intestine?
Superior mesenteric artery
Which two plexuses are the enteric nervous system’s neutrons split between?
Myenteric plexus
Submucosal plexus
When does the MMC occur?
During fasting
What are the three phases of the MMC?
Period of motor inactivity
Period of irregular contractile activity
Short burst of regular phasic contraction that propels secretion, residual food and desquamated cells towards the colon
How is starch absorbed in the small intestine?
- Starch broken up into oligo-, di- and monosaccharides
- Oligo- and disaccharides are further broken up on the microvilli to form monosaccharides
- The monosacchraides are then able to be transported across the enterocytes into the blood
How is protein absorbed in the small intestine?
- Protein is broken down into amino acids and peptides
- Enzymes are activated, allowing them to break down the peptides into oligopeptides
- Some di- and tripeptides are absorbed and the remainder are broken down to amino acids on the microvilli before being absorbed
What enzyme breaks down the majority of starch?
Pancreatic amylase
Which enzymes break down peptides to oligopeptides?
Trypsin
Chymotrypsin
Elastase
How is fat absorbed in the small intestine?
- Pancreatic lipase breaks down the triglycerides in fat to fatty acids and monoglycerides
- The products of fat digestion form mixed micelles along with bile acids and phospholipids
- The lipid contents of the micelles are absorbed into enterocytes and the bile salts remain in the lumen
- Inside the cells the monoglicerides and fatty acids are resynthesised to triglycerides which are incorporated into chylomicrons to be transported into the lymph
What does dietary fat consist of?
Mainly triglycerides
Cholesterol
Fat-soluble vitamins
What happens to the bile salts that remain in the lumen after lipid products are absorbed into enterocytes?
Bile salts pass through the small intestine to be absorbed in the terminal ileum.
They are then transported back to the liver
How can patients with pancreatic exocrine or bile salt insufficiency supplement their fat absorption?
With medium chain triglycerides that are transported via the portal vein