Lecture 23: Large Intestine and Comments on the Liver Flashcards
What three parts does the large intestine consist of?
the cecum
the colon
the rectum
What are the four parts of the colon called?
the ascending colon
the transverse colon
the descending colon
the sigmoidal colon
What is the cecum and where is it located?
A blind ended pouch that makes up first part of the large intestine that the small intestine flows into. It sits in the right iliac fossa.
Which parts of the colon are retroperitoneal and which parts are intraperitoneal?
the ascending and descending colon are both retroperitoneal
the cecum, transverse and sigmoidal colon are all intraperitoneal
What are the names of the bends in the colon and where are they located?
the ascending colon bends into the transverse colon at the hepatic flexure and the transverse colon bends into the descending colon at the splenic flexure
If the the ascending and descending colon are both retroperitoneal, how are they anchored in the body?
they are both fixed to the posterior wall but are covered anteriorly with visceral peritoneum
What is the name of the valve that regulates the passage of material forwards and prevents back flow of material from the large intestine into the small intestine?
the ileocecal valve
What does the appendix contain and how does this relate to potential function?
it contains lymphoid tissue so can have an immune role
it also contains gut bacteria which could be used to reestablish the healthy bacteria in the gut following an illness such as diarrhoea
What is the danger of the appendix swelling and causing appendicitis?
It could burst which means that faeces can be released into the peritoneal cavity. Because of the optimal conditions for growth (warmth) the bacteria can flourish in the cavity and cause peritonitis.
What are three features of the large intestine?
- teniae coli
- haustra
- omental appendices
What are the omental appendices?
Sacs of fat
What are haustra?
They are pouches in the large intestine.
What separated haustra?
semilunar folds
What is the purpose of haustra?
faeces move from haustra to haustra causing distention of the wall which causes contraction to keep the faeces moving through the large intestine
What is one modification to the muscularis (externa) present in the large intestine.
the teniae coli
What are the teniae coli and what it its purpose?
it is a band of longitudinal smooth muscle to cause stronger contractions
Describe the muscularis (externa) in the large intestine
The inner layer is continuous around the tube but the longitudinal smooth muscle layer is modified to form bands (teniae coli) to generate greater force
How is the mucosa modified in the large intestine?
There is no villi
The mucosa form glands invaginating into the lamina propia
the muscularis mucosa is flat (it doesn’t invaginate)
What is the function of the mucosa in the colon?
for water and salt absorption
What is the primary epithelium in the colon?
Simple columnar epithelium
As well as the simple columnar epithelium, there are lots of _______ ______ present. Why is this?
goblet cells
because if the large intestine is removing water from the faeces, the faeces will be very dry and so it needs lubrication
it is also for protection
Superior to the anal columns, there is what type of epithelium?
simple columnar epithelium
Inferior to the anal columns, there is what type of epithelium?
stratified squamous epithelium
Why do we have stratified squamous epithelium in the rectum?
for protection from abrasion
What are the two sphincters in the rectum?
the internal anal sphincter and the external anal sphincter
The internal anal sphincter is under ________ control from _________ muscle
involuntary
smooth
The external anal sphincter is under _________ control from _________ muscle
voluntary
skeletal
Describe the defecation reflex
As the faeces moves along the sigmoid colon into the rectum, it causes distention of the rectal wall to activate stretch receptors to initiate a reflex. This causes the contraction of the rectum to propel the faeces further down to trigger relaxation of the internal sphincter but we control when the external sphincter relaxes
What is the location of the liver?
superior right quadrant of abdominopelvic cavity
What is one function of the liver
produce bile
Describe the liver’s blood supply
1/3 comes from the hepatic artery
the rest comes from the hepatic portal vein
What is the blood what comes to the liver via the hepatic portal vein?
deoxygenated, nutrient rich blood from the small intestines
The blood that arrives at the liver is processed in which cells?
Hepatocytes
The hepatic portal vein, the hepatic artery, and the bile duct travel within the ________ _________
lesser omentum
What are the functional units of the liver called
lobules
What do lobules contain?
rows of hepatocytes surrounding a central vein
What do the rows of hepatocytes produce?
bile
What is in between each hepatocyte?
bile canaliculi
What is in between each row of hepatocytes?
sinusoids
The portal triad is made up of what three vessels?
a branch of the hepatic artery
a branch of the hepatic portal vein
a bile duct
Describe the flow of blood and bile passed hepatocytes in the liver
Blood from both the hepatic artery and hepatic portal vein flows in the sinusoids towards the central vein
Bile is produced as a byproduct when the hepatocytes process blood to detoxify it. Where does the bile go?
into the canaliculi and out via through the bile duct
Does the blood and the bile flow in the same or opposite directions?
opposite
Where does the detoxified blood flow from the central vein?
Blood from the central veins meet at the hepatic vein (not the hepatic portal vein) which drains into the inferior vena cava
What is the difference between the hepatic vein and the hepatic portal vein?
The hepatic vein flows from the liver to the inferior vena cava and the hepatic portal vein flows from the small intestine to the liver
Describe the flow of bile from the liver
it travels in the bile duct to the gallbladder to be stored
when we contract the gallbladder, we get the bile to flow into the bile duct to ultimately join the pancreatic duct at the hepatopancreatic ampulla and then into the duodenum via the duodenal papilla
