lecture 23 - large intestine & liver Flashcards
What are the parts of the large intestine?
Caecum, colon, rectum
What are the parts of the colon?
Ascending, transverse, descending and sigmoidal colons
Which parts of the colon are retroperitoneal?
Ascending and descending colons
Which parts of the colon are intraperitoneal?
Transverse and sigmoidal colons
What valve regulates the passage of material from the SI to LI?
The ileocecal valve
Where does material pass from the SI to LI?
From the ileum of the small intestine to the caecum of the large intestine via the iliocecal valve
What is the appendix?
A finger shaped pouch that projects from the colon and is a reserve of large intestine bacteria
Where is the appendix located?
Variety of locations, on the inferior left side projecting from the colon of the LI
What are the functions of LI bacteria?
Digestion, energy, hormone secretion, pathogen defence
What type of tissue is prevalent in the appendix?
Lymphoid tissue
What are the teniae coli of the LI?
Bands of longitudinal smooth muscle on the surface of the colon - a modification of the muscularis externa
Where are teniae coli found?
All parts of the colon
What are haustra?
A series of pouches in the LI wall that allow for expansion
What feature of the LI is used for fat storage?
Omental appendages
What are the omental appendages of the LI?
Sacs of fat on the surface of the LI that provide fat storage
What is the teniae coli a modification of?
The muscularis layer of the LI
What is the structure of the teniae coli?
Made up of 3 bands of longitudinal muscle surrounding the Large Intestine
What is the function of the teniae coli?
Contract to move faeces along the large intestine
Why does the large intestine have no villi?
Very little absorption of nutrients happens in the LI - ~10%
How does the mucosa of the LI form glands?
The mucosa (except for the muscularis mucosae layer) invaginates
What layers of the GI tube invaginate to form glands in the LI?
The epithelium and lamina propria of the mucosa
What is the function of the mucosa in the LI?
Water and salt absorption - goblet cells also produce mucous for protection and lubrication
Where does the epithelium change in the rectum?
The anal columns mark the boundary
How does the epithelium change in the rectum?
Before the anal columns, it is simple columnar, afterwards it stratified squamous for protection from abrasion
What are the 2 sphincters that control defecation?
Internal and external anal sphincters
Which anal sphincter is under voluntary control?
External anal sphincter
Which anal sphincter is under involuntary control?
Internal anal sphincter
What muscle type is the internal anal sphincter made up of?
Smooth muscle
What muscle type is the external anal sphincter made up of?
Skeletal muscle
What is the process of the defecation reflex?
When faeces moves into the rectum, it stimulates stretch receptors causing the involuntary relaxation of the internal anal sphincters. The conscious decision must then be made to relax the external anal sphincter
What is the digestive function of the liver?
Produce bile for fat digestion
Where is bile stored?
The gall bladder
What proportion of cardiac output goes to the liver?
~25%
What are the 2 sources of blood supply to the liver?
Hepatic artery, Hepatic portal vein
What percentage of the liver’s blood supply is from the hepatic artery?
~33%
What percentage of the liver’s blood supply is from the hepatic portal vein?
~67%
What is delivered by the hepatic artery to the liver?
Oxygenated blood from the general circulation
What is delivered to the liver from the hepatic portal vein?
Nutrient-rich,deoxygenated blood from the small intestine.
What processes nutrient-rich, deoxygenated blood from the hepatic portal vein?
Hepatocytes in the liver
What do the hepatic portal vein, hepatic artery and bile duct travel within?
The lesser omentum
What are the functional units of the liver?
Lobules
What cells within the liver produce bile?
Hepatocytes
What is the name for the capillaries between rows of hepatocytes in the liver?
Liver sinusoids
WHat is the name for the tubes between cells in the liver that receive secreted bile?
Bile canuliculi
What is a portal triad?
A component of a hepatic lobule found in its corner that contains a branch of the hepatic artery and hepatic portal vein, as well as a bile duct
What is the basic process of bile production?
Blood flows towards central vein of hepatic lobule, is processed by hepatocytes which produce bile, bile secreted into caniliculi & travels to bile duct
How many portal triads does each lobe of the liver have?
6 - one at each corner of a six sided lobule
What is the structure of a liver lobule?
6 portal triads, hepatocytes arranged in linear cords between a capillary network, with a central vein
What is the venous drainage of the liver?
Central veins of lobules drain into the hepatic vein which drains into the inferior vena cava
What happens to bile when it reaches the gall bladder?
It is stored and concentrated
