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BIOL21291 > Lecture 10 - Large intestines > Flashcards

Lecture 10 - Large intestines Flashcards

1
Q

The components of the large intestines

A
  • Vermiform appendix
  • Caecum
  • Ascending colon
  • Right colic flexure (hepatic flexure)
  • Transverse colon
  • Left colic flexure (splenic flexure)
  • Descending colon
  • Sigmoid colon
  • Rectum
  • Anal canal
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2
Q

Large intestines: function

A

To absorb water and electrolytes from indigestible intestinal contents and compact this undigested material for excretion as faeces

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3
Q

Taenia Coli

A

Three thickened bands of longitudinal muscle, contracting makes them act like drawstrings, compressing the haustra, squeezing water and electrolytes out of faecal matter

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4
Q

Semilunar folds

A

Folds in between the haustra - very pronounced, bulges/bags formed between each semilunar folds

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5
Q

Haustra

A

Sacculations of the wall between Taenia coli

Very pronounced, bulges/bags formed between each semilunar folds

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6
Q

Epiploic appendages

A

AKA - Omental appendices

Small pouches of fat-filled omentum

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7
Q

Crypts of Lieberkühn: what cell types are presennt?

A

Absorptive cells - more near the lumen
Mucous-secreting goblet cells - More near bases of crypts, useful in lubricating faecal matter

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8
Q

Caecum: what is it, where is it located, and what are its relations?

A

Saclike part of the large intestines

1st part of the large intestine - lies in the right lower quadrant (RLQ)

  • Ileum opens into its medial aspect
  • The appendix opens into its medial aspect inferiorly
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9
Q

Ileocolic lips and ileal orifice

A

Located at the connection between the ileum and caecum

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10
Q

Vermiform appendix: what is it, what are its relations, and what are some key facts?

A

A blind-ended diverticulum

Taenia coli converge at this point – easy to find during surgery

  • Supported by mesoappendix - mesentery supporting the appendix
  • Contains lots of lymphoid tissue
  • Appendicitis may occur
  • The Appendix is variable in length and position, which affects how easy it is to palpate
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11
Q

McBurneys point

A

The reason that appendicitis is so painful

McBurney’s point lies 1/3 the way from the ASIS to the umbilicus - at the appendix base

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12
Q

Why do patients complain of pain in the umbilical region?

A

Think about visceral afferent fibres

T10 is the nerve that is a receptor for the pain, causing poor localisation

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13
Q

Large intestine’s blood supply

A

Right and left sides of the large intestines are supplied by the SMA and the IMA respectively

Right side - SMA:
* Middle colic - Transverse colon
* Right colic - Ascending colon
* Ileocolic - supplies the caecum and lower parts of the large intestines
* Appendicular - splits from the ileocolic, supplies the appendix

Left side - IMA:
* Marginal artery - supplies the transverse colon
* Left colic - supplies the splenic flexure and the descending colon
* Sigmoidal branches - supply the ((descending colon and)?) sigmoid colon
* Superior rectal - supplies the rectum

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14
Q

Large intestine’s venous drainage

A

Right and left sides of the large intestines are supplied by the SMV and the IMV respectively - but the IMV flows into the SMV along with the splenic vein

Right side (midgut) - SMA:
* Middle colic - Transverse colon
* Right colic - Ascending colon
* Ileocolic - drains the caecum and lower parts of the large intestines
* Appendicular - splits from the ileocolic, drains the appendix

Left side (hindgut) - IMA:
* Marginal vein - drains the transverse colon
* Left colic - drains the splenic flexure and the descending colon
* Sigmoidal branches - drains the ((descending colon and)?) sigmoid colon
* Superior rectal - drains the rectum

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15
Q

Large intestines lymphatic drainage

A

ileocolic vein -> superior mesenteric vein -> portal system

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16
Q

Ascending colon: where is it located, how big is it, what is its peritoneum like, is mesentery present, and what are its relations?

A

From caecum to hepatic flexure, in RLQ

12-20 cm long, narrower diameter than caecum

Retroperitoneal, covered with peritoneum anteriorly, medially, and laterally

Has short mesentery in 25% of people

  • Small intestine, abdominal wall and greater omentum anteriorly
  • Illiacus, iliac crest, quadratus lumborum and lower pole of right kidney posteriorly
  • Hepatic flexure at level of 9th or 10th rib
17
Q

Transverse colon: where is it located, how big is it, how is it held in place, and what are its relations?

A

From hepatic to splenic flexures, hangs downward with a variable position (sometimes reaching as far as the pelvis)

40 cm long - the longest part of the colon

Supported by transverse mesocolon
Suspended from the anterior border of the pancreas

  • Abdominal wall and greater omentum anteriorly
  • Second part of the duodenum, head of the pancreas and jejunum & ileum posteriorly
18
Q

Descending colon: where is it located, how big is it, what is its peritoneum like, is mesentery present, and what are its relations?

A

From splenic flexure to pelvic brim, about 15 cm from the anus - faeces stored in the sigmoid colon until just before defaecation

About 25 cm long

Retroperitoneal, covered by the peritoneum anteriorly, and laterally, the peritoneum binds it to the posterior abdominal wall

Short mesentery in 33% of people

  • Small intestine, abdominal wall and greater omentum anteriorly
  • Left psoas major, illiacus, iliac crest, quadratus lumborum and lateral border of the left kidney posteriorly
19
Q

Sigmoid colon: where is it located, what is it, how big is it, how is it held in place, what is volvulus, what is Taenia coli, and what are its relations?

A

From iliac fossa to S3

Named for its S-shape

25 to 38 cm long

Supported by sigmoid mesocolon, therefore mobile

Volvulus is a possibility - occurs when a loop of intestine twists around itself and the mesentery that supplies it, causing a bowel obstruction - this may occur in any part with mesenteries

Taenia coli vanish as longitudinal muscle broadens to form a complete layer in rectum - three longitudinal muscles becomes just one layer

  • Males: urinary bladder
  • Females: uterus & superior vagina
  • Posterior relations - rectum and sacrum
20
Q

Mesenteries: which parts of the large intestines lie outside of the peritoneal cavity, which parts are retroperitoneal, and which parts are subperitoneal?

A

The ascending and descending colons, rectum and anal canal lie outside of the peritoneal cavity

The ascending and descending colons are
retroperitoneal - they are not supported by mesenteries

The rectum (inferior 1/3) and anal canal are
subperitoneal

21
Q

Large intestines innervation

A

Midgut: sympathetic fibres from superior mesenteric plexus, parasympathetic fibres from vagus nerve

Hindgut: sympathetic fibres from inferior mesenteric plexus, parasympathetic fibres from sacral nerves 1 to 3 via pelvic splanchnic nerves

Visceral afferent fibres: T8 – S4

BIOL21291 (13 decks)

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