Week 1 Anatomy Tutorial - Pelvic bone and foetal skull

Question 1

The pelvis is divided into two separate regions, the false/greater pelvis and the true/lesser pelvis. What is the true pelvis bounded by? Is the true pelvis also known as the greater pelvis?

Answer 1

The true pelvis, in which the pelvic organs sit, is bounded superiorly by the pelvic inlet and inferiorly by the pelvic outlet. True pelvis is the lesser pelvis False pelviis is the greater pelvis

Question 2

What are the bones/bony features that form the pelvic inlet?

Answer 2

The sacral promontory of S1 The ala of the sacrum The arcuate line of the ilium The pectineal line and pubic crest - both pubic bone The pubic symphysis

Question 3

What is the arcuate line? What is the pectineal line? What is it also known as?

Answer 3

The arcuate line of the ilium is a smooth rounded border on the interanl surface of the ilium The pectineal line aka the pecten pubis is a ridge on the superior ramis of the pubic bone

Question 4

Is the pubic crest or pubic tubercle medial? What do the pubic crest, arcuate line and pectineal line all make?

Answer 4

The pubic crest lies slighlty medial to the pubic tubercle Linea terminalis - pubic crest + pectineal line + arcuate line

Question 5

What forms the pelvic outlet? Anterior to posterior

Answer 5

Pelvic outlet

Anteriorly - the pubic arch/symphysis , down the inferior pubic ramus and along to the ischial tuberosities psoteriorly before the inferior margin of the sacrotuberous ligament posteriormedially and to the tip of the coccyx

Question 6

Describe the bony attachments of the sacrospinous and sacrotuberous ligaments. Which ligament lies posteriorly?

Answer 6

• Sacrospinous ligaments - attaches to the sacrum and ischial spine
• Sacrotuberous ligament - attaches to the sacrum and ischial tuberosity (larger of the two ligaments)

The sacrotuberous ligament lies posterior to the sacrospinous

Question 7

Why does the pelvis differ between males and females?

Answer 7

The differences in structure of the bony pelvis are related to function Male is designed specifically for bipedalism Female is a compromise between bipedalism and allowing childbirth to occur

Question 8

How does the pelvis differ between males and females? Do males or females have a deeper pelvic cavity?

Answer 8

https://s3.amazonaws.com/classconnection/403/flashcards/11907403/png/pjpgpngjpg-15FDB2B96B02F227D5D.png

Question 9

Are the AP and transverse diameters of the pelvic inlet and outlet greater in males or females?

Answer 9

Both AP and transverse diameters of the pelvic inlet and outlet are greater in females

Question 10

Fractures of the bony pelvis almost always occur as multiple fractures, or in combination with a joint dislocation, and are usually a result of either direct trauma, or of force being transmitted to the pelvis from the lower limbs during falls. Fractures most often occur in weaker areas of the pelvis What are the weaker areas of the bony pelvis?

Answer 10

The acetabulum The sacroiliac joints The ala of the ilium The pubic rami

Question 11

Which bony landmarks of the pelvis are palpable? Are they palpable on internal or external examination?

Answer 11

External examination Ilium - ASIS, PSIS, Iliac crest Ischium - ischial tuberositie, ischiopubic ramus on deep palpation Pubic bone - pubic symphysis, pubic tubercle, ischiopubic ramus on deep palpation Ischial spines palpable on internal avginal examination in the 4 and 8 oclock areas (parts of sacrum and coccyx also palpable)

Question 12

It may be necessary to palpate bony landmarks in a number of clinical scenarios When you need to palpate the ischial spines or the pubic symphysis?

Answer 12

Ischial spine. * To deterermine the station of the baby - ie if the babies head is above the ischial spines (negative station), if below then positive station * To provide a pudendal nerve block - nerve crosses the lateral aspect of the sacrospinous ligament, near its attachment to the ischial spine Pubic symphysis - can be used to measure the fundal height (estimates foetal development - gestation in weeks = height in cm)

Question 13

. Which structures does the pudendal nerve innervate and which spinal cord levels does the nerve originate from?

Answer 13

Innervates the structures within the perineum and the pelvic floor muscle So inferior part of vagina, inferior rectum, and muscles located between pelvic floor and skin of perineum S2,3,,4

Question 14

What nerve modalities travel within the pudendal nerve?

Answer 14

Somatic sensory fibres Somatic motor fibres Sympathetic nerve fibres Parasympathetics run alongiside, not within and are therefore not carried oby the pudendal nerve

Question 15

What are the fontanelles in baby? WHich is the largest and how many/which suture arise from it?

Answer 15

Anterior fontanelle - largest - frontal suture, sagittal suture, the right and left coronal sutures all comes from this Posteior fontanelle Anterolateral fontanelle (sphenoidal fontanelle) Posterolateral fontenelle (mastoid fontanelle)

Question 16

What joins the anterior and posterior fontanelles? What sutures arise from the posterior fontanelle? What is the metopic suture better known as?

Answer 16

The anterior and posterior fontanelles are joined by the sagittal suture Sutures arising from posterior fontanelle - sagittal, and the right and left lambdoidal sutures Metopic suture is better known as the frontal suture

Question 17

What is meant by the term moulding and how do the fontanelles relate to this? How long will it take for the skull to return to normal after the moulding process?

Answer 17

The presence of the fontanelles allows the shape of the fetal skull to change during birth (moulding), by allowing the bones to pass over each other. This means that the skull can pass through the pelvis during labour. The shape of the skull will return to normal within a few days of birth.

Question 18

What is the vertex of the skull formed by?

Answer 18

This is a diamond shaped structure formed by the anterior and posterior fontanelles and the parietal eminences laterally

Question 19

Consider the diameters of the fetal skull and determine which diameter is largest

Answer 19

Have the occipitofrontal diameter and the biparietal diameters The occipitofrontal diameter is greater than the biparietal diameters

Question 20

Describe the preferred position of the fetal head as it descends through each region of the pelvis during labour, through to delivery. Understand and describe why these rotations have to occur.

Answer 20

https://s3.amazonaws.com/classconnection/403/flashcards/11907403/png/pjpgpngjpgpngjpg-15FE956BAE018B0078D.png