Anatomy - Pelvis & Perineum

Question 1

What bone lies at the posterior of the pelvis? How is it joined to the other pelvic bones?

Answer 1

Sacrum

Sacro-iliac cartilage

Question 2

What are the three pelvic bones? What joins them all together?

Answer 2

Ilium (supero-lateral)
Ischium (inferior)
Pubis (anterior)

Triradiate cartilage

Question 3

What joint is at the anterior aspect of the pelvis?

Answer 3

Pubic symphysis

Question 4

What structure is located within the right iliac fossa? What about in the left iliac fossa?

Answer 4

Right: Caecum

Left: Sigmoid colon

Question 5

How is the pelvis orientated when standing in anatomical position?

Answer 5

It is tilted forwards, the superior anterior iliac spines are basically right above the pubic symphysis

Question 6

What is the true pelvis? What is the false pelvis?

Answer 6

True - the pelvis below the arcuate line (which is at the level of the upper border of the pubic symphysis)

False - the entire pelvic setup?

Question 7

Where is the arcuate line?

Answer 7

At the superior border of the pubic symphysis and around the pelvic inlet (it is a circle around the inlet)

Question 8

What are some of the key differences between the male and female pelvis?

Answer 8

• Male is thicker and heavier
• Female’s is wider and shallower (think of it like the male pelvis has been pressed in from the sides)
• Female pelvic outlet is larger
• Sub-pubic angle is more narrow in males

Question 9

Where does puborectalis insert and originate? How is this important in GI physiology?

Answer 9

Originates on one pubis, goes round the rectum and inserts on the other pubis

Creates a kink in the rectal outlet which helps maintain faecal continence, on defaecation the puborectalis relaxes which opens up the rectal pathway

Question 10

What tendon do many of the muscles of the pelvic floor arise from?

Answer 10

Arcuate tendon of the obturator internus