The Large Intestine Flashcards
what are the three main sections of the large intestine
- caecum
- colon
- rectum
what is the colon
the distal part of the gastrointestinal tract that extends away from the caecum at the right iliac fossa to the anal canal
what is the caecum
- the most proximal part of the large intestine, located between the ileum and the ascending colon.
- acts as a reservoir for chyme which it receives from the ileum
- found in the right iliac fossa of the abdomen, lying inferiorly to the ileocecal junction
- can be palpated if enlarged due to faeces, inflammation or malignancy
- continuous with the ascending colon
- intraperitoneal
which section of the large intestine is the most proximal
the caecum
where in the abdomen is the caecum located
right iliac fossa
when can the caecum become palpated
when there are faeces, inflammation or malignancy
what does the caecum derive its name from
inferior blind end - caecus means blind in latin
what is the caecum continouus with superiorly
the ascending colon
is the ascending colon within the peritoneum
no
what is found between the caecum and the ileum
the ileocaecal valve
what is the function of the ileocaecal valve
preventing reflux of large bowel contents into the ileum during peristalsis - thought to function passively
what can the colon be divided into
four parts; ascending, transverse, descending and sigmoid. the sections form an arch, encircling the small intestine
what are the four parts of the colon
ascending
transverse
descending
sigmoid
describe the ascending colon
beginning of the colon, and is a retroperitoneal structure which ascends superiorly from the caecum
rises upward and sits behind the peritonel, moving away from the caecum
how long is the colon
150cm
what is the transverse colon
the second section of the colon that extends from the right colic flexure to the spleen
the least fixed part of the colon, variable in position and is intraperitoneal
in what way is the transverse colon variable in position
can dip into the pelvis in tall and thin individuals
which section of the colon is the least fixed
the transverse colon
what is the descending colon
third section of the colon that is retroperitoneal in the majority of individuals, meaning it sits behind the peritoneum. located anteriorly to the left kidney
when does the descending colon become the sigmoid colon
when it begins to turn medially
describe the sigmoid colon
40cm long sigmoid colon located in the left lower quadrant of the abdomen, extending from the left iliac fossa to the level of the s3 vertebra. interperitoneal
journey gives the sigmoid colon its characteristic s shape
what is the hepatic flexure
the angle formed when the ascending colon becomes the transverse colon. also known as the right colic flexure, and marks the start of the transverse colon
where is the hepatic flexure
the 90 degree turn of the ascending colon by the liver where the transverse colon begins
what is the splenic flexure
the 90 degree turn as the transverse colon goes to the descending colon, also known as the left colic flexure.
where is the splenic flexure
where our spleen is, at the point where the transverse colon becomes the descending colon
what are the taenia coli
3 longitudinal bands of smooth muscle on the outside of the ascending, transverse and descending colon that help to differentiate between the large and small intestine
what is the haustra
circumferential contraction of the inner muscular layer of the colon
what are the appendice epipliocae
pouches of peritoneum filled with fat mainly on the transverse and sigmoid colon, though not the rectum
what is the rectum
the most distal segment of the large intestine, with an important role as a temporary store of faeces
describe the route of the rectum
begins as a proximal continuation of the sigmoid colon, that terminates into the anal canal
how is the rectum distinct from the colon
absence of haustrations, taenia coli and omental appendices
what do the rectal valves do
they support the weight of the faeces and slow movement to the anus, which produces the feeling of wanting to defecate. contains circular muscle
describe the internal haemorrhoidal plexus
a collection of veins in the rectum that communicate directly between the portal and systemic venous system
why do drugs given rectally act quicker than those taken orally
they bypass metabolism by passing through the gut
where is the internal haemorrhoidal plexus found
either side of the anal canal
what are the haemorrhoidal plexuses
big collections of veins located at the lower end of the rectum
what is the internal anal sphincter
involved in the involuntary control of the passage of faeces which gives the feeling wanting to go to the toilet. people gain control of it by 2