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Y2S2-Anatomy-GI > Anatomy of the large intestine > Flashcards

Anatomy of the large intestine Flashcards

1
Q

Describe the large intestine and its subdivisions

A
  • It extends from the ileocecal junction to the muco-cutaneous junction of the anal canal
  • It is about 1.5 meters long
  • It subdivisions are:

1) Cecum & appendix (appendix is retrocecal)

2) Colon:

2a: Ascending colon
2b: Transverse colon
2c: Descending colon
2d: sigmoid colon

3) Rectum

4) Anal canal

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2
Q

What are the characteristic features of the large intestine?

A

1) Taeniae coli: They consists of longitudinal muscle fibers that are thickened and shortened in 3 places forming 3 pouches/haustrations

  • All taenia converges at the base of the appendix and distally it extends up to the sigmoid colon

2) Haustrations/sacculation: These are small pouches that are caused by the sacculation which gives the colon a segmental appearance

3) Appendices epiploicae: These are fatty pouches that projects from the wall only the colon (they are absent in the cecum, appendix & rectum)

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3
Q

What is the clinical significance of taenia coli?

A

They can be used to trace the point where they merge (at the base of the appendix)

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4
Q

What is the cecum?

A
  • It is a blind sac, situated in the right iliac fossa
  • It is completely enveloped in the peritoneum but has no mesentery (which makes it difficult to move)
  • It receives the ileum from the medial side and ascends upwards as the ascending colon
  • There is a structured named vermiform appendix (diverticulum) which arises from its posteromedial wall
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5
Q

What are the three bands of teniae coli?

A

1) Mesocolic (Transverse and mesocolon attaches to it)

2) Omental (To which the omental appendices attaches)

3) Free

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5
Q

What binds the cecum to the lateral abdominal wall?

A

The cecal folds

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6
Q

Describe the interior of the ileocecal junction

A
  • The ileocecal orifice opens to the medial wall of the rectum
  • It is surrounded by a thickening of the circular muscle (the ileocecal sphincter), which prevents the reflux of the cecum contents into the ileum
  • Guarded by an ileocaecal valve
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7
Q

What guards the ileocecal junction, and describe its structure

A
  • Guarded by the ileocaecal valve, which demonstrates an anatomical thickening of the circular muscle forming an anatomical sphincter, which prevents the backflow of contents from the cecum
  • The valve shape is:

1) Labial form ( “seen in cadavers” meaning that it has an upper and lower lip)

2) Papillary form (seen in living people)

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8
Q

What is the difference between the labial and papillary forms of the ileocaecal valve?

A

In the cadaveric picture, the GI muscle has lost its tone, leading to the appearance of labia (‘lips’), whereas the living picture shows a papillary appearance

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9
Q

How does the caecum acts as a guide for surgery in intestinal obstruction?

A

1) If a caecum is distended (then it means that an obstruction has occurred in the large gut)

  • Distended as kaka filled it due to a obstruction in the L.I

2) If a caecum is empty (then it means that the obstruction occurred in the S.I)

  • If caecum is empty it means the obstruction is before the ileocecal junction
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10
Q

What is the paracolic groove?

A

It is seen around the ascending and descending colon, between the reflection of the peritoneum and the colon, if it forms a deeper depression is become a paracolic gutter

  • If it gets deeper than that it will form a mesentery, making the colon unfixed and mobile
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11
Q

What is the vermiform appendix?

A
  • It is a work-like, blind narrow diverticulum
  • It arises from the posteromedial aspect of the cecum, inferior to the ileocecal orifice
  • It has a variable length of 2-20cm
  • Suspended by the mesoappendix
  • It is movable
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12
Q

What is the mesoappendix?

A
  • It is a triangular peritoneal fold which is derived from the mesentery of the terminal ileum
  • It contains a appendicular artery
  • Features of the large intestine like (sacculation, taenia coli, appendices epiploicae) are also seen here
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13
Q

What are the peritoneal folds at the terminal ileum?

A

1) Mesoappendix

2) Superior ileocecal fold

3) Inferior ileocecal fold (blood-less fold of treves)

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14
Q

Where is the superior ileocecal fold located?

A
  • It is a fold of the peritoneum that goes over the ileum and to the cecum, underneath it lies the superior ileocolic branch
  • It lies in front of the terminal ileum, between the base of the mesentery and the anterior wall of the cecum
  • There is a space behind it (where the large intestine can herniate 6-13% of all hernias) called the superior ileocecal recess
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15
Q

What can we find in the superior ileocecal fold?

A

It contains the anterior cecal artery

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16
Q

Where is the superior ileocecal recess located?

A

Behind the superior ileocecal fold, a potential site of large intestine herniation

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17
Q

Where is the inferior ileocecal fold located?

A
  • AKA bloodless fold of treves
  • It is a small fold that extends from the terminal ileum to the front of the mesoappendix
  • The space between it and the mesoappendix is named as the inferior ileocecal fold
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18
Q

What is the boundaries of the inferior ileocecal fold?

A

1) Inferior ileocecal fold which extends from the terminal ileum to the front of the mesoappendix

2) Mesoappendix

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19
Q

What is the artery that is found in the mesoappendix?

A

The appendicular artery

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20
Q

The superior mesenteric artery ends by anastomosing into which artery?

A

The ileocolic branch

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21
Q

Which artery is of close proximity to the superior ileocecal fold?

A

The anterior cecal artery, care must be taken during surgery not to injure it

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22
Q

Where is the appendix positioned?

A
  • It caries from one individual to another but most commonly:
  • Retrocecal (65%)
  • Pelvic (30%)
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23
Q

What and where is the McBurney’s point?

A
  • It is the location of the root of the appendix which is fixed in position
  • It lies at the junction of the lateral 1/3 and medial 2/3 of the right spino-umbilical line (between the right ASIS and the umbilicus)
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24
Q

What is the clinical significance of the McBurney’s point?

A

In appendicitis, digital pressure over the point will cause maximum abdominal tenderness

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25
Q

What is appendicitis?

A

1) Due to the occlusion of the appendicular orifice/lumen, distension will occur and thus inflammation & pain

  • Then

2) Secretions cannot escape

3) Distention of the wall

4) The stretching of the visceral peritoneum causes the sensation of pain which is referred to the region around the umbilicus (as the pain fibers passes through the sympathetic fibers and enters T10 segment of the spinal cord)

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26
Q

In which quadrant is the pain felt in appendicitis?

A

At the right iliac fossa (right lower quadrant)

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27
Q

From what part to what part does the ascending colon span?

A
  • It extends from the ileocecal orifice to the right colic (hepatic) flexure
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28
Q

Where in the abdomen is the ascending colon located?

A
  • It is located retroperitoneally, as it is covered by the peritoneum anteriorly and on its sides
  • Covered by the peritoneum anteriorly and on the lateral sides only
  • It also might have a mesentery “congenital anomaly” in the inferior part (mobile ascending colon), where a volvulus can be expected
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29
Q

What is the paracolic gutter?

A
  • Lies on the right side and it is connected superiorly to the right subphrenic space (this is a direct connection with the right subphrenic space, meaning that inflammatory fluids associated with infection can spread upwards)
  • It is a depression between the ascending colon and the lateral abdominal wall
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30
Q

Do we have a gutter in the left side of the abdomen?

A

No, due to the presence of the phrenicocolic ligament

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31
Q

What is the sub-phrenic space?

A

It is a peritoneal space that lies between the anterior part of the liver and the diaphragm, and it is separated into right and left by the falciform ligament, and bounded via the coronary ligament posterosuperiorly

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32
Q

Describe the anatomy of the transverse colon

A
  • It is suspended from the posterior abdominal wall by the transverse mesocolon
  • It extends from the right (hepatic) to the left colic (splenic) flexures
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33
Q

What attaches the splenic flexure to the diaphragm?

A

A fold of peritoneum nammed (phrenico-colic ligament)

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34
Q

Where does the root of the transverse mesocolon lie?

A
  • It extends across the anterior infra-ampullary segment of the second part of the descending duodenum and the head of the pancreas, it divides the peritoneal cavity into supracolic and infracolic spaces
  • The majority of the root can be found at the anterior border of the pancreas
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35
Q

Where does the root of the mesentery lie?

A
  • About 15cm long, it extends from the duodenojejunal flexure obliquely downwards and to the right of the ileocecal junction
  • It crosses the third part of the duodenum, the aorta, right ureter, right gonadal arteries and the inferior vena cava
36
Q

What is the relations of the second part of the transverse colon?

A

1) Anteriorly:

  • Gallbladder
  • Right lobe of the liver
  • Transverse colon, root of the transverse mesocolon, and the coils of the small intestine

2) Posteriorly:

  • Right kidney
  • Right renal vessels
  • Right edge of the IVC
  • Right psoas major muscle

3) Medially:

  • Head of the pancreas

4) Laterally:

  • Right colic flexure & the right lobe of the liver
37
Q

What are the relations of the third part of the intestine?

A

1) Anteriorly:

  • Root of the mesentery
  • Superior mesenteric vessels
  • Coils of the jejunum

2) Posteriorly:

  • Right psoas major
  • Right ureter
  • IVC
  • Abdominal aorta
  • Right gonadal vessels

3) Superiorly:

  • The head of the pancreas
  • Uncinate process

4) Inferiorly:

  • Coils of the jejunum
38
Q

Describe the anatomy of the descending colon

A
  • It extends retroperitoneally, from the splenic flexure to the pelvic brim, where it continuous as the sigmoid colon
  • Anteriorly & on both sides it is covered by the peritoneum forming a left paracolic gutter but it is not connected to the left subphrenic space due to the phrenicocolic ligament, which helps in limiting the upward spread of the infection
39
Q

Describe the shape of the sigmoid colon

A

It is an S-shaped loop of a variable length situated in the left iliac region

40
Q

What is the extension of the sigmoid colon?

A

It extends from the pelvic brim to the front of the 3rd sacral segment

  • It lies intra-peritoneally and hence freely mobile
41
Q

What suspends the sigmoid colon from the posterior pelvic wall?

A

The peritoneal folds (sigmoid mesocolon), which covers it completely

42
Q

What part of the gut acts as an exception to the rule that intraperitoneal structures are movable?

A

The cecum (it has limited movement)

43
Q

The apex of the sigmoid mesocolon is related to what structures posteriorly?

A

1) Left ureter

2) Bifurcation of the left common iliac artery

3) Left sacro-iliac joint

44
Q

What is meant by diverticulosis (pouches)?

A

-It is a mucosal herniation of the large intestine, usually in the sigmoid through the muscle wall, that occurs when small defects in the muscle wall allows small pockets or pouches to form

  • Occurs due to the perforation of the nutrient arteries to the muscle coat (a weak point) in order to reach to the submucosa
45
Q

What is the blood supply of the large intestine?

A
  • They are branches from the superior mesenteric artery

1) Ileocolic artery which divides into:

1a: Ascending/colic branch (anastomoses with the right colic artery)

1b: Descending branch; it divides into 4 branches

1b.1: Anterior caecal
1b.2: Posterior caecal
1b.3: Appendicular artery
1b.4: ileal (can be a branch of the descending branch or a branch of the appendicular)

2) Right colic artery (supplies the ascending colon, it divides into ascending and descending branches then it anastomoses with the middle colic and the colic/ascending branch of the ilocolic artery)

3) Middle colic artery (it supplies the right 2/3rd of the transverse colon

46
Q

What are the blood supply of the colon?

A

1) Ileocolic artery

2) Right colic artery

3) Middle colic artery

47
Q

What are the branches of the ileocolic artery?

A

1) Ascending/colic branch

2) Descending branch

48
Q

What are the four branches of the descending branch of the ileocolic artery?

A

1) Anterior caecal

2) Posterior caecal

3) Appendicular artery

4) Ileal

49
Q

What are the branches of the right colic artery and with which artery does it anastomose?

A

It divides into ascending and descending branches, it anastomoses with the ileocolic and middle colic arteries

50
Q

What part of the colon is supplied by the middle colic artery?

A

The right 2/3rd of the transverse colon

  • The middle colic gives right and left branches
51
Q

What parts of the L.I is supplied by the superior mesenteric artery?

A
  • the SMA supplies the first 2/3rd of the transverse colon (till the end of the midgut), while the remaining 1/3rd from the start of the hindgut is contributed by the IMA
52
Q

What is the origin of the inferior mesenteric artery?

A

L3, the anterior aspect of the abdominal aorta, inferior to the duodenum and it descends towards the left

  • It supplies the lateral 1/3 of the transverse colon, descending colon, sigmoid, & rectum
53
Q

What are the branches of the inferior mesenteric artery?

A

1) Left colic artery

2) Sigmoid artery

3) Superior rectal artery (it is the terminal branch, it is a continuation of the inferior mesenteric artery beyond the pelvic brim)

54
Q

What does the left colic artery supply?

A

The transverse and descending colons

55
Q

With which artery does the ascending branch of the left colic (a branch of the inferior mesenteric artery) anastomose with?

A

The middle colic and sigmoid arteries

56
Q

What is supplied by the superior rectal artery?

A

The rectum and the upper 2/3rd of the anal canal

57
Q

What is the marginal artery of drummond?

A

It is a continuous anastomotic arcade along the mesenteric border of the large intestine, providing a collateral circulation between the branches of the superior and inferior mesenteric arteries which supplies the large intestine

58
Q

What is arch of riolan?

A

It is a structural variation that might be founded sometimes connecting the left and middle colic arteries (making the avascular window vascular)

  • Mnemonic: Hence, the marginal artery of Drummond runs Distally and the arc of Riolan proximally to the root of the mesentery
59
Q

What is the avascular window?

A
  • Left by the middle colic artery (a large avascular window) in the transverse mesocolon
  • It is the site of surgical access to the lesser sac and the posterior wall of the stomach
60
Q

What is the venous drainage of the colon?

A

1) Superior mesenteric vein (drains the midgut)

2) Inferior mesenteric vein (drains the hind part)

  • Inferior mesenteric vein is a tributary of the splenic vein which will then join with the superior mesenteric vein to form the portal vein (behind the neck of the pancreas)
61
Q

REMEMBER: what 3 structures do we see in the right free margin of the lesser omentum?

A

1) Hepatic artery

2) Common bile duct

3) Portal vein

62
Q

What drains the lymphatic of the colon?

A
  • The lymph flows in the following sequence:

1) Epicolic nodes (found directly on the gut)

2) Paracolic nodes (found along the mesenteric border)

3) Intermediate (meso-) colic nodes (which are found along the colic arteries (ileo- , right, middle, and left)

4) Superior or inferior mesenteric nodes (they will drain into the intestinal lymph trunks to the cysterna chyli → thoracic duct → junction between the internal jugular & subclavian veins)

63
Q

What are the lymph node groups in the abdomen?

A

1) Pre-aortic (related to the three ventral branches of the aorta

2) Para-aortic (lumbar): which is related to the lateral branches of the aorta

64
Q

Bilateral organs of the abdomen like the kidneys, suprarenal glands, and the gonads are supplied by which group of lymph nodes?

A

The para-aortic lymphnodes

65
Q

Unilateral organs of the abdomen like the stomach, duodenum, etc are supplied by which group of lymph nodes?

A

The pr-aortic lymph nodes

66
Q

What are the 3 main groups of preaortic lymph nodes?

A

1) Celiac (foregut)

2) Superior mesenteric (midgut)

3) Inferior mesenteric (hindgut)

67
Q

Which pre-aortic lymph nodes supplies the foregut?

A

The celiac

68
Q

Which pre-aortic lymph nodes supplies the midgut?

A

The superior mesenteric

69
Q

Which pre-aortic lymph nodes supplies the hindgut?

A

The inferior mesenteric

70
Q

What are the organs that are drained (lymphatically) by the coeliac trunk?

A

1) Stomach

2) Liver

3) Spleen

4) Pancreas

71
Q

What is the sympathetic innervation of the large intestine?

A

1) Lesser splanchnic nerve

2) Lumbar splanchnic nerve

72
Q

What is the parasympathetic innervation of the colon?

A
  • It is from the cranio-sacral outflow
  • The cranio part is the vagus nerve (and it ends after 2/3 of the transverse colon)
  • The sacral part is the pelvic nerve (which supplies from the last 1/3 of the transverse colon till the end of the tract), it transports parasympathetic innervation from the S2-S4 spinal nerves to the prevertebral plexus (inferior hypogastric plexus)
73
Q

The sympathetic supply is derived from which spinal cord segment?

A

T10-L2

74
Q

What is the ganglia of the sympathetic nerve that innervates the colon?

A

1) The lesser splanchnic goes to the superior mesenteric ganglion (midgut)

2) The lumbar splanchnic nerve goes to the inferior mesenteric ganglion (hindgut)

75
Q

The parasympathetic supply is derived from which spinal cord segment?

A

S2-S4

76
Q

What is a splanchnic nerve?

A

They are a set of nerves that transports fibers from the sympathetic trunk (sympathetics) or the spinal nerves (parasympathetic) to the prevertebral plexus

77
Q

What are the sympathetic splanchnic nerves?

A

1) Greater splanchnic

2) Lesser splanchnic

3) Least splanchnic

4) Lumbar splanchnic

5) Sacral splanchnic

78
Q

From which vertebral level does the greater splanchnic nerve carry sympathetic innervation?

A

T5-T9

79
Q

What are the prevertebral plexus that are innervated by the greater splanchnic?

A

1) Celiac

2) Superior mesenteric

3) Suprarenal

80
Q

From which vertebral level does the lesser splanchnic nerve carry sympathetic innervation?

A

T10-T11

81
Q

What are the prevertebral plexus that are innervated by the lesser splanchnic?

A

1) Celiac

2) Superior mesenteric

3) Aorticorenal

82
Q

From which vertebral level does the least splanchnic nerve carry sympathetic innervation?

A

T12

83
Q

What are the prevertebral plexus that are innervated by the least splanchnic?

A

1) Inferior mesenteric

2) Aorticorenal

84
Q

From which vertebral level does the lumbar splanchnic nerve carry sympathetic innervation?

A

L1-2

85
Q

What are the prevertebral plexus that are innervated by the lumbar splanchnic?

A

1) Inferior mesenteric

2) Inferior hypogastric

86
Q

From which vertebral level does the Sacral splanchnic nerve carry sympathetic innervation?

A

L1-2

87
Q

What are the prevertebral plexus that are innervated by the sacral splanchnic?

A

acral splanchnic are post-ganglionic sympathetic fibers that exit the sacral ganglia on route to the hypogastric plexuses

Y2S2-Anatomy-GI (6 decks)

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