Anatomy of Large Bowel

Question 1

Parts of the large Bowel?

Answer 1

Caecum, appendix, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, rectum

Question 2

Where are paracolic gutters?

Answer 2

Found on the lateral aspects of the ascending and descending colon, they are part of the greater sac

Question 3

What are haustra?

Answer 3

Bumps formed by tonic contraction of teniae coli

Question 4

Teniae coli?

Answer 4

3 longitudinal smooth muscle bands running from caecum to sigmoid colon

Question 5

Primary functions of large bowel?

Answer 5

Net absorption of Na, Cl, H2O

Net sceretion of HCO3, mucus and K+

Question 6

Colonic Flora role?

Answer 6

• Helps with intestinal immunity
• Promotes motility
• Synthesizes vit K and free fatty acids
• Helps in drug absorption

Question 7

What does the levator ani muscle do for defaecation?

Answer 7

Relaxes

Question 8

What does the levator ani do in

• resting conditions
• sneezing/coughing?

Answer 8

Tomically contracts to hold pelvic organs

Contracts further during cough/sneeze

Question 9

What muscles is the levator ani made up of?

Answer 9

puborectalis
pubococcgyeus
ileococcygeus

Question 10

What is the levator ani supplied by?

Answer 10

Pudendal nerve

S2,3,4

Question 11

Where does the rectum become the anal canal?

Answer 11

Anterior to coccyx

Question 12

Where does the sigmoid colon become the rectum?

Answer 12

Anterior to S3

Question 13

Difference between rectal varrices and rectal haemorrhoids?

Answer 13

Varrices- dilation of collateral veins

Haemorrhoids- prolapse of rectal venous plexuses

Question 14

What are haemorrhoids due to?

Answer 14

Increased pressure

Question 15

What are rectal varices due to?

Answer 15

Related to portal hypertension

Question 16

Common term for levator ani?

Answer 16

Pelvic floor

Question 17

Contraction of which muscle helps maintain continence?

Answer 17

Puborectalis

Question 18

The external anal sphincter is contracted all of the time. True or False?

Answer 18

FALSE

Internal is contracted all of the time

Question 19

How is IAS contracted?

Answer 19

By sympathetic nerves

Question 20

What type of muscle is the IAS?

Answer 20

Smooth muscle

Question 21

What type of muscle is the EAS?

Answer 21

Skeletal

Question 22

How is the extrenal sphincter contracted?

Answer 22

Puodendal nerve

Question 23

Where is a risk site for abscess formation?

Answer 23

Ishioanal fossae (either side of anal canal)

Question 24

What is the pectinate line?

Answer 24

Embryological line between endoderm (GI Tract) and ectoderm (skin)

Question 25

What is above the pectinate line?

Answer 25

• Visceral (all hindgut)
• ANS
• IMA supply
• Venous drainage to HPV
• IM lymph nodes

Question 26

Below pectinate line?

Answer 26

• Parietal
• Somatic & pudendal nerves
• Internal iliac artery
• Venous drainage to systemic veins
• Superficial inguinal nodes

Question 27

Sympathetic nerve supply to rectum and AC?

Answer 27

Cause contraction of IAS

Inhibits peristalsis

Question 28

Parasympathetic nerve supply to rectum and AC?

Answer 28

Inhibits IAS

Stimulates peristalsis

Question 29

Visceral afferents for R & AC?

Answer 29

• Run with parasympathetics

- Sense stretch

Question 30

Rhyme to help remember what vertebrae nerves for rectum and ac enter?

Answer 30

S2,3,4 keeps the 3 ps off the floor.

Pee, poo, penis