Session 25: Bisection of the pelvis and the pelvis cavity

Question 1

What three ossifications make up the hemi-pelvis/innominate bone?

Answer 1

1. ) Pubic bone
2. ) Ilium bone
3. ) Ischium bone

Question 2

How do these ossifications develop and join

Answer 2

• Fuse together at the end of puberty
• Connected in the midline at the front with a secondary cartilaginous joint
• connected posteriorly to the sacrum through the sacro-iliac joints

Question 3

Details of the pubic bone

Answer 3

• L shaped
• Fused with the ilium
• Consists of a superior pubic ramus/pubic tubercle/body of the pubis/first 1/3rd of the inferior pubic ramus

Question 4

What does the ischium consist of?

Answer 4

1.) 2/3rds of the inferior pubic ramus

Question 5

Details of the ilium bone

Answer 5

• Fuses to the ischium and the pubic bone

- Consists of a big wing of bone

Question 6

What separates the lower third of the abdomen from the middle third of the abdomen

Answer 6

The intertubercular plane: between the tuberosities on the iliac crest

Question 7

What is the intercristal plane

Answer 7

From the highest point of the pelvis to the highest point of the pelvis

Question 8

Where does the intercristal plane pass through?

Answer 8

Passes between the spinous processes of L4 and L5 vertebrae

Question 9

Why is the sacroiliac joint a mixed joint?

Answer 9

• has fibrocartilage between the bones

- has some synovium + a synovial cavity

Question 10

Where does the sciatic nerve exit

Answer 10

Leaves through the greater sciatic nutch into the buttock

Question 11

What is the name of the ligament that extends from the ischial tuberosity to the sacrum

Answer 11

The ischiosacral ligament

Question 12

What is the name of the ligament that extends from the spinous process to the sacrum

Answer 12

The spinosacral ligament. Creates a foramina: the greater sciatic foramina

Question 13

Differences between a male and female pelvis

Answer 13

1. ) Angle between the inferior pubic rami: in males it is a V shape but in females it is an open shallow angle
2. ) In males the spine of the ischium points directly towards the sacrum + is a short distance. In females the spines point posteriorly. Large gap between spinous processes and the sacrum
3. ) Prominent lumbo-sacral junction in males. Little prominence in females

Question 14

What is the muscle present in the pelvis?

Answer 14

The levator ani muscle

Question 15

Function of this muscle

Answer 15

Prevent the bowel falling out of the pelvic outlet

Question 16

Details of the levator ani muscle

Answer 16

• At the centre of it lies the anal canal
• It is attaches to the back of the pubis/ the fascia on the obturator internus/ the spin eof the ischium/the sacrum and coccyx

Question 17

How do the fibres of the muscle attach?

Answer 17

They run down + medially. Attach to the midline raphe

Question 18

What happens when the muscles contract

Answer 18

Raises the anal canal upwards

Question 19

What is present posterior to the most posterior fibre of the muscle?

Answer 19

The greater sciatic orifice