The Colon - Anatomy Flashcards
What is the caecum?
Most proximal part of the large intestine and is located between the ileum and the ascending colon.
Blind ending sac
Where can the caecum be found?
In the right iliac fossa of the abdomen. It lies inferiorly to the ileocaecal junction and can be palpated if enlarged due to faeces, inflammation or malignancy.
Superiorly, what is the caecum continuous with?
The ascending colon
Is the caecum intra or retroperitoneal?
Intraperitoneal
What is present between the caecum and the ileum?
The ileocaecal valve
What is the function of the ileocaecal valve?
Prevents reflux of large bowel contents into the ileum during peristalsis and is thought to function passively, as opposed to be a defined muscular sphincter
Where is the caecum derived from?
The embryological midgut
What is the caecum supplied by?
Via branches of the superior mesenteric vessels
Where is arterial supply of the caecum from?
The ileocolic artery - a branch of the SMA
The ileocolic artery divides into anterior and posterior caecal arteries which supply the caecum
What is venous drainage of the caecum provided by?
The corresponding ileocolic vein, and empties into the superior mesenteric vein
How is the caecum innervated?
By the ileocolic branch of the superior mesenteric plexus which follows the same course as the ileocolic artery and carries vagal and sympathetic nerve fibres.
Where is lymph from the caecum drained into?
The ileocolic lymph nodes (which surround the ileocolic artery).
What is the appendix?
A narrow blind-ended tube that is attached to the posteromedial end of the caecum
What does the appendix contain?
A large amount of lymphoid tissue but is not thought to have any vital functions in the human body
What is the appendix supported by?
The mesoappendix, a fold of mesentery which suspends the appendix from the terminal ileum
Where is the appendix derived from?
The embryologic midgut
Therefore, the vascular supply is via branches of the superior mesenteric vessels
Where is the arterial supply of the appendix from?
The appendicular artery
Where is the appendicular artery derived from?
The ileocolic artery, a branch of the superior mesenteric artery
Where is the venous drainage of the appendix via?
The corresponding appendicular vein
Where is the appendicular artery and vein contained?
Within the mesoappendix
What innervates the appendix?
The ileocolic branch of the superior mesenteric plexus. It accompanies the ileocolic artery to reach the appendix.
Where do the sympathetic afferent fibres of the appendix arise from?
T10 of the spinal cord - thus explaining why the visceral pain of early appendicitis is felt centrally within the abdomen.
Where does lymph fluid from the appendix drain into?
Lymph nodes within the mesoappendix and into the ileocolic lymph nodes (which surround the ileocolic artery).
Where is pain from appendicitis referred?
Initially, pain from the appendix and its visceral peritoneum is referred to the umbilical region. As the appendix becomes increasingly inflamed, it irritates the parietal peritoneum, causing the pain to localise to the right lower quadrant.
What can prolonged appendicitis lead to?
It can become necrotic and rupture, resulting in peritonitis (inflammation of the peritoneum).
What are the 4 parts of the colon?
Ascending, transverse, descending, sigmoid