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Clinical Anatomy > Abdomen 3 - Large Intestine, Rectum & Anal Canal > Flashcards

Abdomen 3 - Large Intestine, Rectum & Anal Canal Flashcards

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1
Q

what are the 4 parts of the colon?

A

ascending (on right side)
transverse
descending
sigmoid

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2
Q

what is the primary function of the large intestine?

A

mainly absorbs water and electrolytes

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3
Q

what is the taenia coli? where do they extend from exactly?

A

three longitudinal muscle bands - extend from the base of the appendix to the rectosigmoid junction

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4
Q

what type of muscle is the taenia coli?

A

longitudinal muscle

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5
Q

what happens to the taenia coli past the rectosigmoid junction?

A

spread out & form a continuous muscle layer

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6
Q

what are haustra?

A

pouches/saccules of the colon (give it a segmented appearance) separated by semilunar folds

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7
Q

what separates individual haustra?

A

semilunar folds - don’t fully encircle colon’s lumen

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8
Q

what are omental appendices?

A

small fatty projections from the colon’s surface

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9
Q

what feature gives the colon its segmented appearance?

A

haustra

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10
Q

what separates the pouches of the colon?

A

semilunar folds

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11
Q

what are the fatty projections off the colon’s surface?

A

omental appendices

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12
Q

do semilunar folds go all the way around the colon’s lumen?

A

no - they separate the haustra but don’t form a continuous ring

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13
Q

muscle layers of the colon?

A

inner circular muscle
outer longitudinal muscle - forms the taenia coli

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14
Q

where does the taenia coli extend from?

A

from the base of the appendix to the rectosigmoid junction - forms a continuous muscle layer past the rectum

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15
Q

what is the first part of the large intestine?

A

cecum

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16
Q

where is the cecum located regionally?

A

in the lower right quadrant - within the iliac fossa

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17
Q

what is the peritoneal status of the cecum?

A

intraperitoneal (but lacks a a mesentery; it’s closely related to the posterior abdominal wall)

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18
Q

function of the ileocecal valve?

A

acts as a passive valve to prevent backflow of colonic contents

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19
Q

is the ileocecal valve an anatomical sphincter?

A

no - has minimal circular muscle, just passively prevents backflow of colonic contents

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20
Q

what is the primary function of the cecum in humans?

A

water absorption

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21
Q

where does the appendix originate from?

A

extends as a blind-ended diverticulum from the cecum - inferior to the ileocecal junction

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22
Q

what anatomical structure helps locate the base of the appendix?

A

McBurney’s point
- located 1/3 of the way along a line from the anterior superior iliac spine (ASIS) to the umbilicus

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23
Q

what is the most common position of the appendix?

A

retrocecal (position highly variable)

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24
Q

what is the significance of the taenia coli in relation to the appendix?

A

taenia coli converge at the base of the appendix - forms a continuous outer longitudinal muscle layer

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25
what are the two main functions of the appendix?
immunological role - contains mucosa-associated lymphoid tissue reservoir for gut flora - helps restore beneficial bacteria after infections
26
what is appendicitis?
inflammation of the appendix
27
what are the two main causes of appendicitis?
1. lymphoid hyperplasia - often following infections 2. fecalith/ hardened stool - blocks lumen, leads to fluid build-up and distension
28
why does pain in appendicitis start as vague and then become well-localized?
initial pain is *visceral pain* referred to the T10 dermatome (periumbilical region) as inflammation spreads to the parietal peritoneum it becomes *sharp & localised* at McBurney's point visceral peritoneum has autonomic innervation; parietal peritoneum has somatic innervation - explains transition between general colicky pain to well-defined sharp pain
29
key diagnostic sign of appendicitis?
transition from poorly localized, colicky pain to sharp, well-defined pain in the right lower quadrant (McBurney’s point)
30
why is a ruptured appendix dangerous?
can lead to *peritonitis* - release of bacteria/faeces into peritoneal cavity, causing infection
31
what is the common surgical approach to removing the appendix?
appendectomy - incision at McBurney's point
32
where is McBurney's point? what is it used for?
located 1/3 of the way along a line from the anterior superior iliac spine (ASIS) to the umbilicus used to locate the position of the appendix
33
what is the mesoappendix?
portion of mesentery - mainly connects appendix & post. ab wall; small slip of it connects it to ileum
34
what does the mesoappendix connect?
mainly connects appendix to the posterior abdominal wall small slip of it connects appendix to terminal ileum
35
peritoneal relationship of the ascending colon?
secondary retroperitoneal
36
what structure of the ascending colon forms a potential space lateral to it?
right paracolic gutter
37
what is the clinical significance of the right paracolic gutter?
potential space lateral to the ascending colon allows for fluid movement between the liver and pelvis - important in infection spread
38
where does the ascending colon extend between?
ileocolic junction to hepatic (right colic) flexure
39
what happens to the ascending colon at the hepatic flexure?
turns 90° to the left - goes below liver & under gallbladder fundus
40
once the colon turns at the hepatic flexure, what is its relationship relative to the liver & galbladder?
below liver (inferior) under gallbladder fundus (posterior)
41
what is the longest part of the colon?
transverse colon - approx. 50cm
42
what is the most mobile part of the colon? why?
transverse colon intraperitoneal organ - has a mesenteric connection via the *greater omentum/ gastrocolic ligament* connecting it to the stomach AND it blends with the *transverse mesocolon*
43
peritoneal classification of the transverse colon?
intraperitoneal - suspended by transverse mesocolon
44
where is the midgut-hindgut boundary in the transverse colon?
2/3 of the way along the transverse colon (or at the splenic flexure) - no clear anatomical landmark
45
what is the transverse mesocolon?
double layer of peritoneum - suspends the transverse colon to the posterior abdominal wall
46
what surgical significance does the transverse mesocolon have?
provides access to the omental bursa (lesser sac) via two surgical routes
47
how does the transverse mesocolon affect abdominal compartmentalization?
separates the greater sac into the supracolic and infracolic compartments
48
how is the transverse mesocolon connected to the greater omentum?
its anterior layer merges with the posterior layer of the greater omentum
49
where does the descending colon extend between?
from the splenic flexure to the sigmoid colon
50
what is the peritoneal classification of the descending colon?
secondary retroperitoneal - fused with the posterior abdominal wall during gut rotation
51
what paracolic gutter is closely related to the deacending colon?
left paracolic gutter
52
what is the function of the left paracolic gutter?
allows for fluid movement between the pelvis and upper abdomen
53
how does infection spread differently via the left vs. right paracolic gutter?
right paracolic gutter provides a direct path between the pelvis and liver for infection spread left paracolic gutter doesn't - BUT infections can still spread from the lesser omentum → omental foramen → subhepatic space → right paracolic gutter → pelvis
54
what is the peritoneal classification of the sigmoid colon?
intraperitoneal - suspended by the sigmoid mesocolon
55
where does the root of the sigmoid mesocolon extend from and to?
from the left iliac fossa to S3
56
why is the sigmoid colon prone to volvulus?
has the longest mesentery in the large intestine - more mobile & more prone to twisting/volvulus
57
which colonic mesentery is more prone to volvulus?
sigmoid colon
58
what is the main function of the sigmoid colon?
final water absorption (even though most of the water has already been absorbed)
59
what is the state of stool by the time it reaches the sigmoid colon?
more solid - most of the water has been absorbed
60
where in the colon is diverticulosis most likely to occur? why?
sigmoid colon has highest pressure build-up & weak areas where blood vessels penetrate between the taenia coli
61
what are the main causes of diverticulosis?
ageing low fibre diet increased intraluminal pressure - e.g. chronic constipation, straining weak points int he bowel wall
62
which region of the colon has the most weak points in the bowel wall? what does this mean, clinically?
sigmoid colon - has the weakest areas with only one muscle layer between taenia coli where blood vessels penetrate more prone to diverticulosis & diverticulitis
63
exactly where along the sigmoid colon are diverticula more likely to form?
in the gaps between taenia coli - weakest areas; only one muscle layer there
64
what is diverticulosis?
formation of small outpouchings (diverticula) in the mucosa and submucosa through weak spots in the muscle layer
65
what is diverticulitis?
infection & inflammation of diverticula
66
in what abdominal region would you expect pain with divertculitis?
left lower quadrant
67
symptoms of diverticulitis?
left lower quadrant pain fever blood in faeces
68
in what abdominal region would you expect diverticulitis pain?
left lower quadrant
69
which medication class increases the risk of diverticulitis and why?
opioids - they slow bowel motility, increasing constipation and pressure build-up
70
which one of these ISN'T a symptom of diverticulitis? A: left lower quadrant pain B: left kidney pain C: fever D: blood in stool
B: left kidney pain
71
what is volvulus?
twisting of a mobile part of the intestine - leads to lumen obstruction and ischemia
72
what happens as a consequence of when an intestinal loop twists around itself?
bowel obstruction & no passage of faeces ischaemia - vessel compression with twisting
73
which locations of the intestine are more prone to volvulus? why?
sigmoid colon ileum & jejunum loops - have long mesenteries
74
if volvulus doesn't resolve spontaneously, what complications can arise?
severe constipation ischaemia necrosis
75
treatment for persistent volvulus?
potential surgery
76
at what vertebral level does the rectum begin?
S3 - at rectosigmoid junction
77
what are the peritoneal relations of the three 1/3s of the rectum?
upper 1/3 = intraperitoneal middle 1/3 = retroperitoneal lower 1/3 = subperitoneal
78
peritoneal classification of the middle 1/3 of the rectum?
retroperitoneal
79
peritoneal classification of the lower 1/3 of the rectum?
subperitoneal
80
peritoneal classification of the upper 1/3 of the rectum?
intraperitoneal
81
what happens to the taenia coli at the rectosigmoid junction?
merge into a continuous longitudinal muscle layer (no longer three separate bands)
82
what is the anorectal flexure?
an 80-degree posterior bend where the rectum perforates the pelvic diaphragm
83
what is the landmark at which the rectum perforates the pelvic diaphragm? why is this important?
anorectal flexure - the 80 degree bend helps maintain continence
84
how does the anorectal flexure change during defecation?
straightens to allow stool to pass more easily
85
where is the lowest point of the peritoneal cavity in MALES?
rectovesical pouch - between rectum & bladder
86
where is the lowest point of the peritoneal cavity in FEMALES?
rectouterine pouch - between rectum & uterus
87
why is the rectouterine pouch clinically significant?
fluid collects here in certain clinical conditions - ascites, peritonitis, ruptured ectopic pregnancy fluid can be collected to test for these conditions (infection/ ruptured ectopic pregnancy)
88
how can fluid be collected from the rectouterine pouch?
needle inserted through the posterior fornix of the vagina

Clinical Anatomy (52 decks)

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