Part III: Rectum Pg 109-112

Question 1

Pelvic end of alimentary tract where feces accumulate prior to defecation

Answer 1

Rectum

Question 2

Rectosigmoid junction located anterior to what vertebral level

Answer 2

S3

Question 3

Is the rectum intraperitoneal, retroperitoneal or extraperitoneal or sub peritoneal?

Answer 3

• Superior third of rectum is retroperitoneal

- Inferior third of rectum is subperitoneal

Question 4

What happens to the teniae coli as the transition from sigmoid colon to rectum?

Answer 4

Teniae coli of sigmoid colon expand into continuous layer on rectum

NOTE: Epiploic appendages, haustra and sacculations are also absent from rectum

Question 5

What is the sacral flexure?

Answer 5

Where the rectum follows contour of sacrum and coccyx

Question 6

What is the anorectal flexure?

Answer 6

Where the rectum takes a sharp turn at coccyx and pierces pelvic diaphragm

Question 7

What is the functional significance of the anorectal flexure?

Answer 7

Approximately 80 degree posterior turn important for maintaining fecal continence

Question 8

What maintains the 80 degree posterior turn of the anorectal flexure?

Answer 8

tonus of Puborectalis M at rest

• Puborectalis M must actively contract to resist peristaltic contractions in rectum and prevent defecation

Question 9

Conscious initiation of defecation requires:

Answer 9

relaxation of Puborectalis M

Question 10

3 sharp lateral flexures are present in rectum (superior, intermediate, inferior) and correspond to:

Answer 10

Transverse Rectal Folds of mucosa and submucosa

Question 11

dilatable terminal region of the rectum lying above and supported by Levator Ani M

Answer 11

Ampulla

Question 12

What is the function of the ampulla of the rectum?

Answer 12

Relaxes to hold accumulating fecal material prior to defecation

Question 13

What is the function of the rectovesical pouch (in males), rectouterine pouch (in females) and pararectal fossae (in both sexes)?

Answer 13

All of these provide space for rectum to distend as it fills with feces

Question 14

Posteriorly in both sexes, the rectum is associated with:

Answer 14

• Sacral vertebrae and coccyx
• Sacral plexuses and inferior ends of sympathetic trunks
• Median Sacral AV

Question 15

Anteriorly in males, the rectum is associated with:

Answer 15

• Fundus of urinary bladder and terminal parts of ureters
• Ductus deferens, seminal vesicles and prostate
• Separated from these structures by rectovesical pouch

Question 16

Anteriorly in females, their rectum is associated with

Answer 16

• Vagina, posterior fornix and cervix of uterus

- Separated from these structures by rectouterine pouch

Question 17

What is the arterial supply to the proximal part of rectum?

Answer 17

Superior Rectal A - branches from Inferior Mesenteric A

Question 18

What is the arterial supply to the anorectal junction and anal canal of the rectum?

Answer 18

Inferior Rectal A - branches from Internal Pudendal A

Question 19

There are three arteries that supply the rectum. What are they?

Answer 19

• Superior Rectal A - branches from Inferior Mesenteric A
• Middle Rectal A - branches from Internal Iliac (anterior division)
• Inferior Rectal A - branches from Internal Pudendal A

Question 20

What is the venous drainage of the rectum?

Answer 20

• Superior Rectal V drains to hepatic portal venous system
• Middle and inferior Rectal V drain to systemic system via Internal Iliac V
• Anastomoses between these veins create an important portacaval anastomosis

Question 21

Lymphatic drainage of superior portion of the rectum is through:

Answer 21

pararectal to inferior mesenteric and lumbar nodes

Question 22

Lymphatic drainage of inferior portion of the rectum is through:

Answer 22

internal iliac lymph nodes

Question 23

Sympathetic innervation of the rectum is via:

Answer 23

lumbar splanchnic N through superior hypogastric plexus

NOTE: Possibly vasomotor but not functionally significant

Question 24

Parasympathetic innervation of the rectum is via:

Answer 24

pelvic splanchnic N through inferior hypogastric plexus

Question 25

Parasympathetic innervation to the rectum function:

Answer 25

Motor fibers to rectal muscularis externa

Question 26

Visceral afferents (conveying both pain and/or distension) from the rectum pass through

Answer 26

pelvic splanchnic N to S2-S4

Question 27

What happens to anal sphincters when the ampulla is empty?

Answer 27

- Internal Anal Sphincter M is contracted | - External Anal Sphincter M is relaxed

Question 28

Defecation is controlled by innervation mediated through:

Answer 28

pelvic splanchnic N

Question 29

When feces accumulates in ampulla and sufficiently distends it, what happens to the anal sphincters?

Answer 29

- Internal Anal Sphincter M reflexively relaxes | - External Anal Sphincter M reflexively contracts

Question 30

What initiates the external anal sphincter M to reflexively contract?

Answer 30

visceral afferents in pelvic splanchnic N

Question 31

Defecation requires voluntary override of:

Answer 31

reflexive External Anal Sphincter M contraction NOTE: Puborectalis M also must voluntarily relax

Question 32

Parasympathetic stimulation to the rectum during defecation does what?

Answer 32

increases peristaltic activity in rectum

Question 33

The terminal part of large intestine (approximately 3cm) that extends from pelvic diaphragm (Puborectalis M) to anus

Answer 33

Anal canal

Question 34

Thickened circular smooth muscle around the superior two-thirds of anal canal

Answer 34

Internal Anal Sphincter

Question 35

Is the internal anal sphincter under voluntary or involuntary control?

Answer 35

Involuntary NOTE: Normally contracted (sympathetic) to prevent leakage of feces or flatus but reflexively relaxes in response to pressure of feces/gas in rectal ampulla

Question 36

Broad band of skeletal muscle surrounding inferior two-thirds of anal canal

Answer 36

External Anal Sphincter

Question 37

Is the external anal sphincter under voluntary or involuntary control?

Answer 37

Voluntary

Question 38

The external anal sphincter is attached anteriorly to ______ & posteriorly to _______.

Answer 38

- perineal body | - coccyx (via anococcygeal L)

Question 39

The external anal sphincter blends superiorly with:

Answer 39

Puborectalis M

Question 40

What voluntarily contracts to prevent defecation or relax to allow defecation?

Answer 40

External anal sphincter and puborectalis M

Question 41

What innervates the external anal sphincter?

Answer 41

Inferior Rectal N (S4) from Pudendal N

Question 42

longitudinal ridges of mucosa in superior half of anal canal

Answer 42

Anal columns

Question 43

What part of the anus contains terminal branches of Superior Rectal AV

Answer 43

Anal Columns

Question 44

What landmark is located at superior ends of anal columns

Answer 44

Anorectal Junction

Question 45

What structure is located at inferior ends of anal columns

Answer 45

Anal Valves

Question 46

The small recesses located just superior to anal valves in the anal columns that produce mucous to facilitate passage of feces

Answer 46

Anal sinuses

Question 47

irregular line formed by anal valves

Answer 47

Pectinate lines

Question 48

What is the arterial supply to the anal canal above the pectinate line?

Answer 48

Superior Rectal A (from Inferior Mesenteric A) NOTE: Middle Rectal A forms anastomoses with Superior/Inferior Rectal A

Question 49

What is the arterial supply to the anal canal below the pectinate line?

Answer 49

Inferior Rectal A (from Internal Pudendal A) NOTE: Middle Rectal A forms anastomoses with Superior/Inferior Rectal A

Question 50

What is the venous drainage of the anal canal superior to pectinate line?

Answer 50

Hepatic portal system via Superior Rectal V

Question 51

What is the venous drainage of the anal canal inferior to pectinate line?

Answer 51

IVC via Inferior Rectal V, Internal Pudendal V

Question 52

What is the lymphatic drainage of the anal canal superior to pectinate line?

Answer 52

internal iliac lymph nodes

Question 53

What is the lymphatic drainage of the anal canal inferior to pectinate line?

Answer 53

superficial inguinal lymph nodes

Question 54

Autonomic innervation to the anal canal above the pectinate line is via:

Answer 54

inferior hypogastric plexus

Question 55

Sympathetic innervation of the anal function:

Answer 55

maintain tonus of Internal Anal Sphincter

Question 56

Parasympathetic innervation of the anal canal function:

Answer 56

relax Internal Anal Sphincter and initiate peristalsis

Question 57

Sympathetic and parasympathetic innervation is responsive to”

Answer 57

distension/stretching but insensitive to touching/cutting

Question 58

Somatic innervation of the anal canal below pectinate line is via:

Answer 58

Inferior Rectal N (Pudendal N)

Question 59

Somatic innervation to the anal canal function:

Answer 59

- Motor innervation to External Anal Sphincter | - Responsive to pain, touch, temperature