Pelvic Skeletal Anatomy, Anal Triangle

Question 1

What 2 muscles form pelvic walls?

Answer 1

1. Piriformis

2. Obturator internus

Question 2

What 2 muscles form pelvic diaphragm (floor)?

Answer 2

1. Levator ani

2. Coccygeus

Question 3

What are the 5 boundaries of pelvic outlet?

Answer 3

1. Pubic symphysis
2. Ischiopubic rami
3. Ischial tuberosities
4. Sacrotuberous ligaments
5. Coccyx

Question 4

How can pelvic outlet be divided?

Answer 4

(Line between two ischial tuberosities)

1. Anterior: urogenital triangle
2. Posterior: anal triangle

Question 5

What separates abdomen from pelvis?

Answer 5

Pelvic outlet

Question 6

From a medial perspective, what plane is urogenital triangle in?

Answer 6

Perpendicular to coronal (// with floor)

Question 7

From a medial perspective, what plane is anal triangle in?

Answer 7

Almost // with plane of pubic inlet (makes 45* angle with plane of urogenital triangle)

Question 8

What is a method of obstetric anesthesia?

Answer 8

Blockage of pudendal nerve at ischial spine

Question 9

What does pudendal nerve innervate?

Answer 9

All muscles of pelvis and perineum (via inferior rectal and perineal nerves)

Question 10

What spinal segments contribute to pudendal nerve?

Answer 10

S2, S3, S4

Question 11

What is the effect of anesthetizing pudendal nerve?

Answer 11

1. Anesthesia of much of perineal skin (less pain)
2. Relaxation of perineal muscles (facilitating birth)
   (Would the patient void their bladder and bowel?)

Question 12

Where does L5 vertebrate meet sacrum?

Answer 12

Sacral promontory

Question 13

What defines the false and true pelvises?

Answer 13

False: superior to pelvic inlet
True: inferior to pelvic inlet

Question 14

What single nerve innervates external rectal sphincter?

Answer 14

Inferior rectal nerve

Question 15

What spinal segments compose pudendal nerve?

Answer 15

S2-S4