Lower Gi Tract Flashcards
How long is the Lower GI tract and where does it extend from
1.5m long, 6,5 cm in diameter and extends ileum to the anus
What does the lower GI tract consist of?
Caecum Appendix Colon Rectum Anal canal Anus
Functions of large intestine
Absorption of water
Absorption of vitamins liberated by bacteria resident in the intestine
Compaction of faeces
Expulsion of faeces from the body
Special features of the large intestine
Teniae coli- longitudinal bands of smooth muscle
Haustra- series of pouches which give the colon a segmented appearance
Epiploic appendages - small punches of fat that are attached to the teniae
What is the caecum and function
First part of the large intestine
Blind-ended pouch, located in the right iliac fossa
The ileum opens into the large intestine at the ileocaecal junction
The orifice of the ileocaecal junction is guarded by the ileocaecal valve
What is the Appendix and function
A slender, blind ended tube with a narrow lumen
Arises from the posteromedial aspect of the caecum
The wall of the appendix contains a large amount of lymphoid tissue
May function as a lymphoid organ but can live without it
What are the 4 parts of the colon
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
What is the ascending colon
Ascends on the right side of the abdomen
Extends from the caecum to the hepatic flexure
Retroperitoneal- fixed to posterior abdominal wall
what is the transverse colon
Crosses the abdomen from right to left
Extends from the hepatic flexure to the splenic flexure
Suspended from the posterior abdominal wall by the transverse mesocolon
What is the descending colon
Descend on the left side of the abdomen
Extends from the splenic flexure to the sigmoid colon
Sigmoid colon
Terminal Portion of the colon
S shaped segment that is continuous with the rectum
Suspended from the posterior abdominal wall by the sigmoid mesocolon
Rectum
Continuous superiorly with sigmoid colon
Continuous inferiority with anal canal at the anorectal junction
Expandable organ which provides temporary storage for faeces
What is the anal canal?
extends from anorectal junctions to the anus
Internal anal sphincter- involuntary
External anal sphincter- voluntary
Haustral churning
Haustra are the small pouches which give the large intestine it’s segmented appearance
Haustra distend when they fill with chyme
This stimulates smooth muscle contraction
The chyme is compressed and compacted and moved on to the next haustral
Explain Mass movement
Occur in large intestine
Powerful peristaltic contractions that push boils into rectum
Stimulates by distension of stomach and duodenum
Occur a few times daily
Can produce the urge to defecate
