Large Bowel Flashcards
Gross anatomy of Large bowel
Approx. 1.5m in length
Extends from ileum to anus
Externally has a haustrated appearance
4 sections of large bowel
Caecum
Colon
Rectum
Anal canal
Layers of large bowel
Mucosal layer- simple columnar epithelium. Mucous secreting glands
Submucosal layer- contains vessels and nerves
Muscular layer- inner circular, outer longitudinal
Serous- peritoneum
Gross anatomy of caecum
Lies in the right iliac fossa
Approx 6cm long and 7.5cm wide
Below ends blind but continuous with colon above
Ileocaecal offrice guarded by the iliececal valve
Gross anatomy of colon
4 parts: ascesnding, transverse, descending and sigmoid
Hepatic flexure
Splenic flexure
Gross anatomy of rectum
Commenced at the Lowe end of the sigmoid colon and the level of S3
12cm
Passes downwards following curve of sacrum and coccyx
Gross anatomy of anal canal
4cm
Surrounded by internal anal sphincter
Surrounding the internal sphincter is a band of voluntary muscle
What is covered by the peritoneum
Intraperitoneal
- caecum
- transverse colon
- sigmoid colon
Retroperitoneal
- ascending colon
- descending colon
- rectum
Blood supply
Superior mesenteric artery supplies caecum and most of transverse colon
Inferior mesenteric artery supplies last portion of transverse colon to sigmoid colon
Internal iliac arteries
Functions of large bowel
Absorption of water, electrolytes and vitamins Secretion of mucous Storage of indigestible food Production of vitamin K Défaecation
What happens with cellulose
Cannot be digested
Therefore increased fibre diet leads to an increased bulk in faeces which stimulates paerstalsis
Outline defaecation
Stretching the rectal wall triggers nerve receptors
Relaxing of internal anal sphincter
Reflex contraction of sigmoid colon
No peristalsis in large intestine
