Large intestine
The caecum and appendix
- Caecum lies below level of ileocaecal valve
- Situated in right iliac fossa
- Completely cover with peritoneum
- Peritoneal folds create
- Superior ileocaecal fossa
- Inferior ileocaecal fossa
- Retrocaecal fossa
- Has three longitudinal bands of muscle knows as the teniae coli
- Converge on base of appendix
- Anterior relations include the greater omentum and anterior
abdominal wall
- Posterior relations include the psoas and iliacus muscle and femoral
nerve
- Blood supply is from the anterior and posterior caecal arteries
- These are branches of the ileocolic artery
Appendix
- Appendix contains a large amount of lymphoid tissue
- Has a complete covering of longitudinal muscle formed from the
teniae coli
- Base is attached to the posterior medial surface of the caecum
- Arises below the ileocaecal valve
- Covered in peritoneum and has a short mesentery known as the
mesoappendix
- Related to anterior abdominal wall one third away along a line
joining the anterior superior iliac spine and umbilicus
- Tip do the appendix can be found in various positions including:
- Hanging down into the pelvis related to the right pelvic wall
- Behind the caecum in the retrocaecal fossa
- Projecting upward along the lateral side of the caecum
- In front or behind the terminal ileum
- Blood supply is from the appendicular artery a branch of the
posterior caecal artery
The colon
- The colon is divided into
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Blood supply of the colon is as follows
- Ascending colon is from the ileocolic and right colic arteries
- Proximal transverse colon is from the middle colic artery
- Distal transverse colon is from the superior left colic artery
- Descending and sigmoid colon is from the inferior left colic
artery
- The ileocolic, right and middle colic arteries are branches of the
superior mesenteric artery
- The superior and inferior left colic arteries are branches of the
inferior mesenteric artery
- Venous and lymphatic drainage follows the blood supply
The rectum
- 15 cm long
- Begins in front of third sacral vertebra
- Passes through pelvic diaphragm
- Continuous with anal canal
- Peritoneum covers
- Anterior and later surfaces of upper third
- Anterior surface only of middle third
- Lower third has no peritoneal covering
- Outer longitudinal and inner circular muscle coat
- Mucous membrane forms three transverse folds
Blood supply
- Arterial supply if superior, middle and inferior rectal arteries
- Superior rectal artery is a branch of the inferior mesenteric
artery
- Middle rectal artery is a branch of the internal iliac artery
- Inferior rectal artery is branch of the internal pudendal artery
- Venous drainage corresponds to arterial supply
- Superior rectal vein drains into inferior mesenteric vein
- Middle rectal vein drains into internal iliac vein
- Inferior rectal vein drains into internal pudendal vein
- Site if important porto-systemic anastomosis
Lymphatic drainage
- Lymphatic drainage is into pararectal nodes
- Follows superior mesenteric artery to inferior mesenteric nodes
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