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Human Systems and Anatomy > The Large Intestine > Flashcards

The Large Intestine Flashcards

1
Q

what are the three main sections of the large intestine

A
  • caecum
  • colon
  • rectum
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2
Q

what is the colon

A

the distal part of the gastrointestinal tract that extends away from the caecum at the right iliac fossa to the anal canal

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3
Q

what is the caecum

A
  • 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
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4
Q

which section of the large intestine is the most proximal

A

the caecum

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5
Q

where in the abdomen is the caecum located

A

right iliac fossa

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6
Q

when can the caecum become palpated

A

when there are faeces, inflammation or malignancy

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7
Q

what does the caecum derive its name from

A

inferior blind end - caecus means blind in latin

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8
Q

what is the caecum continouus with superiorly

A

the ascending colon

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9
Q

is the ascending colon within the peritoneum

A

no

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10
Q

what is found between the caecum and the ileum

A

the ileocaecal valve

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11
Q

what is the function of the ileocaecal valve

A

preventing reflux of large bowel contents into the ileum during peristalsis - thought to function passively

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12
Q

what can the colon be divided into

A

four parts; ascending, transverse, descending and sigmoid. the sections form an arch, encircling the small intestine

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12
Q

what are the four parts of the colon

A

ascending
transverse
descending
sigmoid

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13
Q

describe the ascending colon

A

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

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14
Q

how long is the colon

A

150cm

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14
Q

what is the transverse colon

A

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

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15
Q

in what way is the transverse colon variable in position

A

can dip into the pelvis in tall and thin individuals

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16
Q

which section of the colon is the least fixed

A

the transverse colon

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17
Q

what is the descending colon

A

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

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18
Q

when does the descending colon become the sigmoid colon

A

when it begins to turn medially

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19
Q

describe the sigmoid colon

A

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

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20
Q

what is the hepatic flexure

A

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

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21
Q

where is the hepatic flexure

A

the 90 degree turn of the ascending colon by the liver where the transverse colon begins

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22
Q

what is the splenic flexure

A

the 90 degree turn as the transverse colon goes to the descending colon, also known as the left colic flexure.

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23
where is the splenic flexure
where our spleen is, at the point where the transverse colon becomes the descending colon
24
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
25
what is the haustra
circumferential contraction of the inner muscular layer of the colon
26
what are the appendice epipliocae
pouches of peritoneum filled with fat mainly on the transverse and sigmoid colon, though not the rectum
27
what is the rectum
the most distal segment of the large intestine, with an important role as a temporary store of faeces
28
describe the route of the rectum
begins as a proximal continuation of the sigmoid colon, that terminates into the anal canal
29
how is the rectum distinct from the colon
absence of haustrations, taenia coli and omental appendices
30
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
31
describe the internal haemorrhoidal plexus
a collection of veins in the rectum that communicate directly between the portal and systemic venous system
32
why do drugs given rectally act quicker than those taken orally
they bypass metabolism by passing through the gut
33
where is the internal haemorrhoidal plexus found
either side of the anal canal
34
what are the haemorrhoidal plexuses
big collections of veins located at the lower end of the rectum
35
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
36
what is the external sphincter in control of
the voluntary control of expulsion of faeces
37
describe barium enema
filling the large intestine with diluted barium liquid while the x ray images are being taken. the barium enemas are used to diagnose disorders of the large intestine and rectum. these disorders may include colonic tumours, polyps, diverticula and anatomical abnormalities
38
what are diverticula
abnormal out pouches
39
what are barium enemas used for
diagnosing disorders of the large intestine and rectum
40
what can be included in the disorders of the large intestine
- colonic tumours - polyps - diverticula - anatomical abnormalities
41
what is the ileo-ceacal junction
this is the junction between the caecum and ileum, and is also known as a valve. it is a fold of mucosa that allows chyme to pass from the small intestine to the large intestine
42
what leads off from the caecum
the vermiform appendix
43
does the caecum have an essential function in human beings
no
44
compare the structure of the large intestine to the small intestine (similarities)
the basic structures are the same: - the same epithelium of simple columnar goblet cells - intestinal crypts of leiberkuhn - mucosal glands to produce mucous
45
describe the differences between the structure of the large intestine and the small intestine
large intestine lacks villi and has an incomplte layer of longitudinal muscle called taenia coli ring like arrangement of haustrae the mucosal folds can look like epithelium but they are not
46
describe the histological layers of the large intestine
- mucosa (epithelium) on the surface - underlying lamina propria - muscularis mucosae - submucosa - muscularis externa
47
what are crypts
the glands found in the epithelial lining of the small intestine and colon. covered by two types of epithelium - goblet cells and enterocytes
48
what are goblet cells
cells that secrete mucous
49
what do enterocytes produce
water and electrocytes
50
what are crypts and intestinal villi coverd by
goblet cells and enterocytes
51
where is the anal canal located
extraperitoneal between the anorectal junction and the anus
52
what are the zones of the anal canal
columnar zone intermediate zone cutaneous zone
53
what is the columnar zone of the anal canal
anal columns anal cushions valves crypts of morgagni dentate line
54
what is found in the intermediate zone of the anal canal
anoderm
55
what is found in the cutaneous zone of the anal canal
perianal skin
56
break down the blood supply of the anal canal
- above the dentate line is the superior rectal artery - below the dentate line is the middle and inferior rectal arteries
57
how much of the anal canal is above the dentate line
two thirds
58
how much of the anal canal is found below the dentate line
a third
59
what supplies blood to the superior two thirds of the anal canal
the superior rectal artery
60
what supplies blood to the inferior third of the anal canal
middle and inferior rectal arteries
61
describe the venous drainage of the anal canal above the dentate line
superior rectal vein followed by the hepatic portal circulation
62
describe the venous drainage of the inferior third of the anal canal
middle and inferior rectal veins followed by the vena cava circulation
63
describe the innervation of the anal canal above the dentate line
inferior mesenteric plexus pelvic splanchnic nerves inferior hypogastric plexus
64
describe the innervation of the anal canal below the dentate line
pudendal nerve
65
what epithelium is found in the colorectal zone of the anal canal
simple columnar
66
what epithelium is found in the transitional zone of the anal canal
simple columnar and stratified squamous epithelium
67
what epithelium is found is the anoderm
stratified squamous non keratinised epithelium
68
what epithelium is found in the cutaneous zone
stratified squamous keratinised epithelium
69
what are the functions of the anal canal
faecal continence and defecation
70
what does the colon function in
absorption of fluids and electrolytes from the chyme within the small intestine as it passes into the caecum
71
what volume of chyme enters the large intestine from the ileum
0.5-1 litre
72
what does the colon absorb from the small intestine chyme
fluid and electrolytes
73
what can failure to absorb fluid and electrolytes lead to
diarrhoea
74
what is the role of the intestinal flora found within the large intestine
- fermenting dietary fibres like cellulose and lipids - producing flatus (gas) - synthesise some vitamins like the vitamin b complex and vitamin k
75
describe the vitamin b complex
8 different types of b vitamins direct impact on energy levels, brain function and cell metabolism helps prevent infections and good cell health, growth of red blood cells and nerve function
76
what is vitamin k
fat soluble and needed for blood clotting to help wound healing
77
describe the motility of the large intestine
- churning - similar to segmentation in the small intestine - contraction of circular muscles to break things down locally - squeezing action on chyme - mainly in the caecum and the ascending colon
78
what are propulsive movements describing
the motility of the large intestine
79
what are the different propulsive movements of the large intestine
peristalsis and mass movements
80
describe peristalsis
short range peristalsis in transverse and descending colon, propelling semi solid faecel matter toward the rectum
81
describe mass movements
infrequent, more sustained contractions usually made after meals
82
what is rectal distension associated with
the desire to defaecate
83
what is defaecation
ejection of faecal matter from the rectum via the anal canal an involuntary reflex
84
what are the muscles used for defaecation
the internal and external sphincters, composed of smooth muscle controlled by the autonomic nervous system
85
how can some diseases of the large bowel be managed
removal of a portion of the colon
86
describe how a colostomy occurs
proximal end of the gut tube is brough out through the abdominal wall, creating an opening called a stoma which can be emptied into a bag a hole is made in the abdomen and the free end of the colon is pulled through the hole and stitched to the abdomen to create the colostomy
87
describe an ileostomy
a small bowel is diverted through an opening in the abdominal wall, creating a stoma. can be needed as either a temporary measure or permanent. could be done for healing after bowel cancer resection, to relieve inflammation of inflammatory bowel disease.
88
describe diarrhoea
characterised by excessively watery stools and is caused by gastrointestinal tract infections and failure of fluid absorption could be associated with reduced colonic motility, as there is less mixing and less fluid absorption results in dehydration and electrolyte imbalance defined as loose stools for 3 or more times in a day
89
how is diarrhoea a killer
infection accounts for 1 in 9 deaths in children worldwide per year
90
describe constipation
- characterised by hard faeces, difficult to pass - due to increased fluid absorption - associated with gastrointestinal spasm, side effect of some drugs like opiates, and a role of dietary fibre - Not defaecting at least 3 times per week, hard, dry and lumpy and straining when going to the toilet - Associated with gastrointestinal spasm. - the more dietary fibres that we have the less constipation we will experience
91

Human Systems and Anatomy (57 decks)

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