Lecture 23: LARGE INTESTINE AND LIVER Flashcards
Why is the large intestine called the large intestine?
Because of its large diameter
What does the large intestine consist of?
Cecum, colon and rectum
What does the ileum empty into?
The cecum
What is the colon divided into?
Ascending, transverse, descending and sigmoidal
What is between the ascending and transverse colon?
Right colic (hepatic) flexure
What is between the transverse and descending colon?
Left colic (splenic) flexure
Where are the ascending and descending colon?
Retroperitoneal
Where are the transverse and sigmoidal colon?
Intraperitoneal
Where is the iliocecal valve?
At the junction between the small and large intestine
What does the ileocecal valve do?
Regulates the passage of material into the cecum and prevents back flow
What is found in the appendix?
A reserve of large intestine bacteria population. Also contains lymphoid tissue so could have an immune role
Where is the appendix found?
In a variety of locations
What does inflammation of the appendix cause?
Appendicitis
What does a barium enema enable?
X ray images of the large intestine to be taken to assess function
What are features of the large intestine?
Teniae coli, haustra and omental appendices
What are the teniae coli?
Bands of longitudinal smooth muscle
What are haustra?
Series of pouches in the wall of the colon separated by semilunar folds
What are omental appendices?
Sacs of fat for storage
What are teniae coli a modification of?
The muscularis layer (inner circular is still the same)
How many teniae coli are there?
Three bands of (outer) longitudinal smooth muscle
What does the teniae coli allow?
Stronger contraction to move things through the large intestine
Is there villi in the large intestine?
No, because the large surface area for absorption isn’t required
What does the mucosa do in the large intestine?
invaginate to form intestinal glands
What does the mucosa consist of?
Epithelium, lamina propria and muscularis mucosae
Does the muscularis mucosae invaginate?
No
what is the function of the mucosa of the large intestine?
Water and salt/electrolyte absorption
How does the large intestine mucosa perform its function?
Goblet cells produce mucous (protection and lubrication)
What marks the boundary where the epithelium changes?
Anal columns
What is the epithelium before the anal column?
Simple columnar
What is the epithelium after the anal columns?
Stratified squamous which becomes continuous with the epidermis of the skin
Why does the anal canal have stratified squamous epithelium?
For protection from abrasion
What is the internal anal sphincter?
Smooth muscle under involuntary control
What is the external anal sphincter?
Skeletal muscle under voluntary control
What does movement of faeces into the rectum do?
Stimulates stretch receptors
What happens to the internal anal sphincter when the stretch receptors are stimulated?
They relax (involuntary)
What happens to the external anal sphincter when the stretch receptors are stimulated?
It is contracting until a conscious decision to defacate is made and it relaxes
Where is the liver found?
In the superior right quadrant of the abdominopelvic cavity
what is the function of the liver?
It has lots but primarily produces bile which is stored in the gall bladder found under the liver
How much of cardiac output does the liver receive?
Approximately 25%
Where s 1/3 of the livers blood supply from?
The hepatic artery which branches off the abdominal artery
Where is the rest of the livers blood supply from?
The hepatic portal vein which carries nutrient rich, deoxygenated blood from the small intestines to be processed by hepatocytes
What do the hepatic portal vein, hepatic artery and bile duct travel through?
The lesser omentum
What is the liver made up of?
Functional hexagonal units called lobules
What are liver cells called?
Hepatocytes
How are hepatocytes arranged?
In rows
What do hepatocytes do?
Produce bile
What are between rows of hepatocytes?
Liver sinusoids
What is between hepatocytes?
Bile canalicul (channels to reach the duct)
What is a portal triad made of?
Branch of hepatic artery, branch of portal vein and a bile duct
Where does blood flow in the liver?
Towards the central vein
What happens with blood in the liver?
It is processed by the hepatocytes (removes toxins) which produce bile
Where is bile secreted?
Into canaliculi and travels to the bile duct
What do central veins drain into?
The hepatic vein which drains into the inferior vena cava
Where does bile from the live travel?
To the gall bladder where it is stored and concentrated
What does the bile duct join with?
The pancreatic duct at hepatopancreatic ampulla to form the hepatopancreatic duct
