Small Intestine & Associated Structures Flashcards
What is the purpose of the small intestine?
Carry chyme away from the stomach and deposits it in the large intestine
What are the 3 structures of the small intestine?
Duodenum, jejunum, ileum
How is the small intestine suspended in the abdominal cavity?
Mesentery
What happens in the duodenum?
Receives chyme through pyloric sphincter
What runs alongside the descending duodenum and next to the greater curvature of the stomach?
Pancreas
What happens in the jejunum?
Most chemical digestion and absorption (longest part)
What happens in the ileum?
Peyer’s patches - help protect the animal from disease by controlling bacteria, functioning in antibody production and aiding in filtration
Where does the ileum empty?
Horse - large intestine at cecum
Dog/ cat - colon
Ruminant/ pig - cecum and colon
What adaptations help increase the surface area of the small intestine?
Plications, villi containing microvilli (brush border), intestinal crypts (crypts of Langerhans)
What is found in the intestinal crypts?
Undifferentiated cells that undergo cell division to replace worn down villi
What are lacteals?
Lymphatic capillaries - carry absorbed lipids and fat-soluble substances to thoracic duct and into vena cava
What is found in the villi that collects nutrients in the GI tract and transports them to the liver?
Blood capillaries
What two hormones does the duodenal mucosa secrete?
CCK and secretin
What is the function of CCK?
Inhibits gastric emptying - allows chyme to exit stomach at a controlled rate allowing it more time to neutralize
Causes increased secretion of bicarbonate and pancreatic digestive enzymes
Stimulates secretion of enteropeptidase
What stimulates the secretion of CCK and secretin?
High amino acid or fatty acid concentrations or low pH of chyme entering duodenum
What is the function of secretin?
Decreases HCl production in the stomach
Increases pancreatic and biliary bicarbonate secretions
Why is it important for chyme to be more alkaline than acidic as it exits the stomach?
Digestive enzymes from the pancreas function more optimally
What are the two functions of the pancreas?
Endocrine & exocrine
What does the endocrine part of the pancreas consist of and what hormones does it produce?
Pancreatic islets - beta cells secrete insulin to lower glucose levels, alpha cells produce glucagon to increase glucose levels
What does the exocrine portion of the pancreas consist of?
Groups of acini
What does the exocrine pancreas secrete?
Bicarbonate and digestive proenzymes
What causes an increase in pancreatic secretions?
Anticipation of food, neural and endocrine stimuli
What enzymes secreted by the pancreas are vital to digestion?
Lipase - breaks down lipids
Amylase - breaks down starches
Nuclease - breaks down nucleic acids
Protease - breaks down proteins
All proteolytic enzymes are secreted by the pancreas in an inactive form called ______________
Proenzyme
What activates the proenzymes in the pancreas?
CCK
What is the largest digestive gland in the body?
Liver
What are the functions of the liver?
Secretes substances essential for digestion and absorption of nutrients
Synthesizes nutrients and regulates their release into the bloodstream
Excretes toxic substances
Produces plasma proteins, cholesterol, blood coagulation factors
What are the two surfaces of the liver?
Diaphragmatic surface - in contact with diaphragm
Visceral surface - in contact with abdominal organs
What ligament attaches the liver to the diaphragm?
Falciform ligament
The mammalian liver consists of what?
Lobes
Why is the liver strategically placed?
To process blood leaving the GI tract
The area of the liver known as the triad consists of what?
Hepatic portal vein, hepatic artery, bile ducts
The liver receives blood from what two sources?
Hepatic portal vein from the GI tract and the hepatic artery (branch of cardiac artery)
The hepatic artery and portal vein come together in the liver and empty their blood into the ______________
Sinusoids
What protein producing cells can we find in the liver?
Hepatocytes
What macrophages can we find in the liver?
Kupffer cells
How is bile excreted in the liver?
By hepatocytes into ductules called canaliculi
What is bile excreted by the liver necessary for in the intestines?
Lipid digestion
What is the purpose of the gall bladder?
Concentrates and stores bile until needed
What species lacks a gall bladder?
Horse
What is bile composed of?
Bile salts, phospholipids, cholesterol, bile pigments
What stimulates contraction of the gall bladder and relaxation of the sphincter of Oddi?
CCK
What is enterohepatic circulation?
The pathway for bile from the liver to the intestine to the hepatic portal vein and back to the liver
What is a breakdown product of hemoglobin that is eliminated through bile?
Bilirubin (dead red blood cells)
If the level of bilirubin in the blood becomes elevated, what symptoms will we see?
Jaundice
What 2 vital rolls does the liver play that keeps blood glucose levels normal?
Metabolizes glucose to produce energy
Fructose and galactose are converted to glucose
Excess glucose is stored as glycogen where?
Liver, skeletal muscle, adipose cells
What is glycogenolysis?
Glycogen is broken down to glucose when needed
What is gluconeogenesis?
Synthesis of glucose from non-carbohydrate sources (ketosis)
What proteins does the liver produce?
Plasma proteins including albumin and blood clotting proteins
What is peristalsis?
Propels content
What is segmentation?
Mixing action
What are the methods of active processes when it comes to absorption across intestinal mucosa?
Transport molecules
Antiport - one molecule is exchanged for another
Secondary active transport - glucose moves by cotransport with sodium
Facilitated diffusion - uses a carrier molecule
What is the 4 step process to digest/ absorb fat?
Emulsification
Hydrolysis
Micelle formation
Absorption
What is a passive process when it comes to absorption across intestinal mucosa?
Simple diffusion
