GI system: L28 - Large intestine and the liver Flashcards
Describe the location of the different regions of the large intestine in the abdomino-pelvic cavity.
The ascending and descending colons are retroperitoneal both covered in visceral peritoneum when then forms mesentery. The transverse colon moves across body beneath liver and stomach, peritoneal. The sigmoid colon is when the colon goes to the midline and the rectum goes down the midline.
What are the taeniae coli?
Triple banded smooth muscle running along colon for stronger contractions than a single layer when they would be same size.
What are Haustra pouches?
Inner circular layer of muscle forms semilunar folds that divide the large intestine into pouches.
Name the 5 section of large intestine.
Caecum, ascending colon, transverse colon, descending colon, sigmoid colon.
What is the ileocaecal valve?
Allows free passage of waste to large intestine from the ileum, without backflow.
What are the flexures called of the large intestine and where are they located.
Hepatic flexure (right colic) and splenic flexure (left colic)
What is the vermiform appendix, where is it found and the theorised function?
The vermiform appendix is a distal continuation of the wall of the large intestine. It can be found in many different positions, which is why it can be tricky to find. The appendix contains many bacteria that is also found in our large intestine so it is thought it’s role is to repopulate the intestines if there was to be a complete flush of bacteria due to gastroenteritis.
Why might the vermiform appendix be a problem?
If it becomes inflamed, the lumen of the appendix is obstructed and become filled with mucous and swell up, it can burst and spill it’s contents into the peritoneum meaning a lot of bacteria spreading throughout the peritoneum to cause wide spread inflammation.
What are some 4-layered variations of the large intestine wall?
The mucosa contain mucous secreting glands which is important for helping move the waste material through the tract. These mucous glands are tubular structures called crypts that extend from the muscularis mucosae. They are formed by closely packed goblet cells and absorptive cells.
The lamina propria contains many blood and lymphatic vessels. It contains collagen and immune cells that defend against any invading pathogens.
The muscularis layer of the large intestine is discontinuous with the outer longitudinal layer forming taeniae coli and inner circular layer forming haustra.
The peritoneum forms fat-filled pouches on the surface of the large intestine called the appendices epiploicae.
What are structures of the rectum and anus and their function?
Mucous = not cause damage
Valves = holding material, defy gravity
Anal column, have lots of plexus of veins.
Internal anal sphincter = smooth muscle, parasympathetic control.
External anal sphincter = skeletal muscle, voluntary response, stretch receptors tell cerebral cortex control if full.
Name the regions of the liver and where do the secretions deliver to.
Has left and right lobes, falciform ligament in between. Lobes>Sectors>Segments. Secretions of the liver, gallbladder and pancreas all deliver to duodenum.
Explain the bile pathway from secretion to the duct it travels.
There is continuous secretion of bile by the liver. Ducts carrying bile gather together throughout the liver until they merge on the left and right hepatic ducts. These merge to form the common hepatic duct. This common hepatic duct then merges with the cystic duct to form the common bile duct. Half of this bile is delivered to the duodenum, the other half is stored in the gallbladder.
