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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
Q

where is the splenic flexure

A

where our spleen is, at the point where the transverse colon becomes the descending colon

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24
Q

what are the taenia coli

A

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

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25
Q

what is the haustra

A

circumferential contraction of the inner muscular layer of the colon

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26
Q

what are the appendice epipliocae

A

pouches of peritoneum filled with fat mainly on the transverse and sigmoid colon, though not the rectum

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27
Q

what is the rectum

A

the most distal segment of the large intestine, with an important role as a temporary store of faeces

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28
Q

describe the route of the rectum

A

begins as a proximal continuation of the sigmoid colon, that terminates into the anal canal

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29
Q

how is the rectum distinct from the colon

A

absence of haustrations, taenia coli and omental appendices

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30
Q

what do the rectal valves do

A

they support the weight of the faeces and slow movement to the anus, which produces the feeling of wanting to defecate. contains circular muscle

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31
Q

describe the internal haemorrhoidal plexus

A

a collection of veins in the rectum that communicate directly between the portal and systemic venous system

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32
Q

why do drugs given rectally act quicker than those taken orally

A

they bypass metabolism by passing through the gut

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33
Q

where is the internal haemorrhoidal plexus found

A

either side of the anal canal

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34
Q

what are the haemorrhoidal plexuses

A

big collections of veins located at the lower end of the rectum

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35
Q

what is the internal anal sphincter

A

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

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36
Q

what is the external sphincter in control of

A

the voluntary control of expulsion of faeces

37
Q

describe barium enema

A

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
Q

what are diverticula

A

abnormal out pouches

39
Q

what are barium enemas used for

A

diagnosing disorders of the large intestine and rectum

40
Q

what can be included in the disorders of the large intestine

A
  • colonic tumours
  • polyps
  • diverticula
  • anatomical abnormalities
41
Q

what is the ileo-ceacal junction

A

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
Q

what leads off from the caecum

A

the vermiform appendix

43
Q

does the caecum have an essential function in human beings

A

no

44
Q

compare the structure of the large intestine to the small intestine (similarities)

A

the basic structures are the same:
- the same epithelium of simple columnar goblet cells
- intestinal crypts of leiberkuhn
- mucosal glands to produce mucous

45
Q

describe the differences between the structure of the large intestine and the small intestine

A

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
Q

describe the histological layers of the large intestine

A
  • mucosa (epithelium) on the surface
  • underlying lamina propria
  • muscularis mucosae
  • submucosa
  • muscularis externa
47
Q

what are crypts

A

the glands found in the epithelial lining of the small intestine and colon. covered by two types of epithelium - goblet cells and enterocytes

48
Q

what are goblet cells

A

cells that secrete mucous

49
Q

what do enterocytes produce

A

water and electrocytes

50
Q

what are crypts and intestinal villi coverd by

A

goblet cells and enterocytes

51
Q

where is the anal canal located

A

extraperitoneal between the anorectal junction and the anus

52
Q

what are the zones of the anal canal

A

columnar zone
intermediate zone
cutaneous zone

53
Q

what is the columnar zone of the anal canal

A

anal columns
anal cushions
valves
crypts of morgagni
dentate line

54
Q

what is found in the intermediate zone of the anal canal

A

anoderm

55
Q

what is found in the cutaneous zone of the anal canal

A

perianal skin

56
Q

break down the blood supply of the anal canal

A
  • above the dentate line is the superior rectal artery
  • below the dentate line is the middle and inferior rectal arteries
57
Q

how much of the anal canal is above the dentate line

A

two thirds

58
Q

how much of the anal canal is found below the dentate line

A

a third

59
Q

what supplies blood to the superior two thirds of the anal canal

A

the superior rectal artery

60
Q

what supplies blood to the inferior third of the anal canal

A

middle and inferior rectal arteries

61
Q

describe the venous drainage of the anal canal above the dentate line

A

superior rectal vein followed by the hepatic portal circulation

62
Q

describe the venous drainage of the inferior third of the anal canal

A

middle and inferior rectal veins followed by the vena cava circulation

63
Q

describe the innervation of the anal canal above the dentate line

A

inferior mesenteric plexus
pelvic splanchnic nerves
inferior hypogastric plexus

64
Q

describe the innervation of the anal canal below the dentate line

A

pudendal nerve

65
Q

what epithelium is found in the colorectal zone of the anal canal

A

simple columnar

66
Q

what epithelium is found in the transitional zone of the anal canal

A

simple columnar and stratified squamous epithelium

67
Q

what epithelium is found is the anoderm

A

stratified squamous non keratinised epithelium

68
Q

what epithelium is found in the cutaneous zone

A

stratified squamous keratinised epithelium

69
Q

what are the functions of the anal canal

A

faecal continence and defecation

70
Q

what does the colon function in

A

absorption of fluids and electrolytes from the chyme within the small intestine as it passes into the caecum

71
Q

what volume of chyme enters the large intestine from the ileum

A

0.5-1 litre

72
Q

what does the colon absorb from the small intestine chyme

A

fluid and electrolytes

73
Q

what can failure to absorb fluid and electrolytes lead to

A

diarrhoea

74
Q

what is the role of the intestinal flora found within the large intestine

A
  • fermenting dietary fibres like cellulose and lipids
  • producing flatus (gas)
  • synthesise some vitamins like the vitamin b complex and vitamin k
75
Q

describe the vitamin b complex

A

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
Q

what is vitamin k

A

fat soluble and needed for blood clotting to help wound healing

77
Q

describe the motility of the large intestine

A
  • 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
Q

what are propulsive movements describing

A

the motility of the large intestine

79
Q

what are the different propulsive movements of the large intestine

A

peristalsis and mass movements

80
Q

describe peristalsis

A

short range peristalsis in transverse and descending colon, propelling semi solid faecel matter toward the rectum

81
Q

describe mass movements

A

infrequent, more sustained contractions usually made after meals

82
Q

what is rectal distension associated with

A

the desire to defaecate

83
Q

what is defaecation

A

ejection of faecal matter from the rectum via the anal canal
an involuntary reflex

84
Q

what are the muscles used for defaecation

A

the internal and external sphincters, composed of smooth muscle controlled by the autonomic nervous system

85
Q

how can some diseases of the large bowel be managed

A

removal of a portion of the colon

86
Q

describe how a colostomy occurs

A

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
Q

describe an ileostomy

A

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
Q

describe diarrhoea

A

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
Q

how is diarrhoea a killer

A

infection accounts for 1 in 9 deaths in children worldwide per year

90
Q

describe constipation

A
  • 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
Q
A

Human Systems and Anatomy (54 decks)

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