Rectum/Anal Canal

Question 1

The rectum is technically a part of what gastrointestinal structure?

Answer 1

Large intestine (between the sigmoid colon and the anal canal)

Question 2

What is the rectosigmoid junction of the rectum and where is it located?

Answer 2

Upper limit of the rectum located at the middle of the sacrum

Question 3

What is the anorectal junction and where is it located?

Answer 3

The lower limit of the rectum located at the upper border of the pelvic diaphragm

Question 4

What muscles forms a sling around the rectum at the anorectal junction?

Answer 4

Puborectalis

Question 5

What is the rectal ampulla and where is it located?

Answer 5

Dilated terminal portion of the rectum located immediately above the pelvic diaphragm

Question 6

How many transverse rectal folds are there?

Answer 6

Three

Question 7

Does the rectum have mesentery, omental appendices, or haustra?

Answer 7

No.

Question 8

Does the rectum have taeniae coli?

Answer 8

Yes, but it’s spread out as a complete layer unlike the intestines

Question 9

Peritoneum covers what parts of the upper third of the rectum?

Answer 9

Front and sides

Question 10

Peritoneum covers what parts of the middle third of the rectum?

Answer 10

Front

Question 11

Peritoneum covers what parts of the lower third of the rectum?

Answer 11

There is no peritoneal covering here

Question 12

The anal canal is between what two structures?

Answer 12

Pelvic diaphragm and anus

Question 13

About how many anal columns lie in the anal canal?

Answer 13

5-10

Question 14

What vascular structures do each anal column contain?

Answer 14

Small branch of the superior rectal artery and a small tributary of the superior rectal vein

Question 15

What are the longitudinal folds of mucosa which lie in the upper half of the anal canal?

Answer 15

Anal columns

Question 16

What are the crescent-shaped folds which connect the lower ends of the anal columns?

Answer 16

Anal valves

Question 17

What are the recesses located between the anal valves and the wall of the anal canal?

Answer 17

Anal sinuses

Question 18

What marks the lower limit of the anal valves around the circumference of the anal canal?

Answer 18

Pectinate line

Question 19

What is the bluish white zone located inferior to the pectinate line?

Answer 19

Anal pecten

Question 20

What is the distal termination of the anal canal where it meets the skin?

Answer 20

Anocutaneous line

Question 21

Which anal sphincter is under involuntary control?

Answer 21

Internal anal sphincter

Question 22

Which anal sphincter is a continuation of the smooth muscle layer of the rectum below the pelvic diaphragm?

Answer 22

Internal anal sphincter

Question 23

What are the three parts of the external anal sphincter?

Answer 23

Subcutaneous, superficial, and deep parts

Question 24

What is the nerve supply of the external anal sphincter?

Answer 24

Nerve to external anal sphincter (S4)

Question 25

What is the function of the external anal sphincter?

Answer 25

Closes anal orifice

Question 26

Which anal sphincter is under voluntary control?

Answer 26

External anal sphincter

Question 27

From where does the superior rectal artery arise?

Answer 27

Inferior mesenteric artery

Question 28

From where does the middle rectal artery arise?

Answer 28

Internal iliac artery

Question 29

From where does the inferior rectal artery arise?

Answer 29

Internal pudendal artery

Question 30

From where does the median sacral artery arise?

Answer 30

Abdominal aorta

Question 31

What arteries make up the blood supply of the rectum and anal canal?

Answer 31

Superior, middle, and inferior rectal arteries and the median sacral artery

Question 32

What are internal hemorrhoids?

Answer 32

Varicosities of the superior rectal vein

Question 33

Internal hemorrhoids cause bulging of what anal structures?

Answer 33

Anal columns

Question 34

Are internal hemorrhoids painful?

Answer 34

No, painless

Question 35

Where do internal hemorrhoids occur?

Answer 35

Above the pectinate line

Question 36

What are external hemorrhoids?

Answer 36

Varicosities of the inferior rectal vein

Question 37

Where do external hemorrhoids occur?

Answer 37

Below the pectinate line

Question 38

Are external hemorrhoids painful?

Answer 38

Can be very painful

Question 39

What are the causes of both types of hemorrhoids?

Answer 39

Pregnancy, heavy lifting, sitting, straining-chronic constipation, portal hypertension

Question 40

Why can heavy lifting cause hemorrhoids?

Answer 40

Due to the increased intra-abdominal presure

Question 41

What would be a possible morbid underlying cause of hemorrhoids?

Answer 41

Portal hypertension

Question 42

What group of people are at a high risk for developing hemorrhoids?

Answer 42

Long distance trunk drivers

Question 43

What is the epithelium like in the anal canal above the pectinate line?

Answer 43

Columnar or cuboidal

Question 44

What is the epithelium like in the anal canal below the pectinate line?

Answer 44

Stratified squamous

Question 45

What is the nerve supply of the anal canal above the pectinate line?

Answer 45

Autonomic fibers

Question 46

What is the nerve supply of the anal canal below the pectinate line?

Answer 46

Pudendal nerve

Question 47

What is the venous supply of the anal canal above the pectinate line?

Answer 47

Superior rectal

Question 48

What is the venous supply of the anal canal below the pectinate line?

Answer 48

Middle, inferior rectal

Question 49

Which lymph nodes are found in the anal canal above the pectinate line?

Answer 49

Internal iliac

Question 50

Which lymph nodes are found in the anal canal below the pectinate line?

Answer 50

Superficial inguinal

Question 51

The upper visceral 2/3 of the anal canal is from which embryologically derived structure?

Answer 51

Hindgut

Question 52

The lower somatic 1/3 of the anal canal is from which embryologically derived structure?

Answer 52

Proctodeum

Question 53

What part of the GI tract accumulates fecal matter?

Answer 53

Sigmoid colon

Question 54

What is usually contained in the rectum?

Answer 54

Nothing; it is usually empty

Question 55

How does the sigmoid colon empty its contents into the rectum?

Answer 55

Through mass peristaltic movement

Question 56

During defecation, what muscles contract to increase pressure within the rectum?

Answer 56

The longitudinal muscle layer of the rectum and the anterior abdominal wall muscles

Question 57

What muscle relaxes during defecation to decrease the angle of the perineal flexure?

Answer 57

Puborectalis

Question 58

What is opened due to the increase in pressure within the rectum during defecation?

Answer 58

Internal anal sphincter

Question 59

What is relaxed under voluntary control during defecation?

Answer 59

External anal sphincter

Question 60

What are the steps of defecation?

Answer 60

1. Sigmoid colon empties contents into rectum by mass peristalsis 2. Muscles contract to increase rectal pressure 3. Puborectalis relaxes 4. Internal anal sphincter opens 5. External anal sphincter relaxes