Foetal Skull

Question 1

Describe the skull

Answer 1

• Consists of 29 bones
• Ovoid shaped
• Consists of vault, base and face

Question 2

What are the skull bones divided into?

Answer 2

• Vault
• 2 frontal
• 2 parietal
• 2 temporal
• 1 occipital

Question 3

What is the vault?

Answer 3

Dome-shaped part between the orbital ridges and the nape of the neck

Question 4

Describe the occipital bone

Answer 4

• Lies at the back of the head

- Ossification centre = occipital protuberance

Question 5

Describe the parietal bones

Answer 5

• Lie on either side of the skull

- Ossification centres = parietal eminences

Question 6

Describe the frontal bones

Answer 6

• Form the forehead and sinciput

- Ossification centres = frontal eminences

Question 7

What is the base?

Answer 7

Firmly united bone protecting the vital centres of the medulla oblongata

Question 8

Describe the face

Answer 8

• 14 small bones
• Firmly united and non-compressible
• Extends from orbital ridges to neck
• The point between the eyebrows in known as the glabella

Question 9

What are the 4 regions of the foetal skull?

Answer 9

1. Forehead/ Sinciput region (brow)
2. Vertex
3. Occiput
4. Face

Question 10

Describe the forehead/ sinciput region

Answer 10

Extends from the anterior fontanelle and the coronal suture to the orbital ridges

Question 11

Describe the vertex

Answer 11

Bounded by the posterior fontanelle, the 2 parietal eminences and the anterior fontanelle
- Vertex positing = head first

Question 12

Describe the occiput

Answer 12

• Lies between the foramen magnum and posterior fontanelle

- The part below the occipital protuberance is known as the sub-occipital region

Question 13

Name 3 landmarks

Answer 13

1. Occipital protuberance
2. Mentum (chin)
3. Glabella

Question 14

What is a suture?

Answer 14

• The cranial joints formed when 2 bones meet
• Soft, fibrous tissue where ossification is not complete
• Allows moulding during labour and birth and expansion of brain development

Question 15

What is ossification?

Answer 15

The hardening of the bones of the vault from the ossification centre outwards

Question 16

What are the 4 sutures called?

Answer 16

1. Frontal - between 2 halves of the frontal bone
2. Sagittal - between 2 parietal bones
3. Lamboidal - separates occipital bone and 2 parietal bones
4. Coronal - separates front bones from parietal bones

Question 17

What is a fontanelle?

Answer 17

A membranous non-ossified area where 2 or more sutures meet

Question 18

Describe the anterior fontanelle

Answer 18

• Diamond/kite shaped
• Formed by junction of sagittal, coronal and frontal sutures
• Larger than the posterior fontanelle
• Closes at 18 months of age

Question 19

What should the anterior fontanelle feel like during a VE?

Answer 19

• 4 sutures felt emanating from the fontanelle
• Demonstrates de-flexed head
• Alerts practitioners to larger diameter coming through pelvis
• Indicates direct occipital position

Question 20

What is another name for the anterior fontanelle?

Answer 20

Bregma

Question 21

Describe the posterior fontanelle

Answer 21

• Triangular
• Smaller than the anterior fontanelle
• Formed by junction of lamboidal and sagittal sutures
• Closes at 6 weeks

Question 22

What should the posterior fontanelle feel like during a VE?

Answer 22

• 3 sutures felt emanating from fontanelle
• Well-flexed head position
• Smaller diameter presenting
• Indicated occipitoanterior position

Question 23

What is another name for the posterior fontanelle?

Answer 23

Lambda

Question 24

What are the 9 diameters of the foetal skull?

Answer 24

1. Suboccipitobregmatic
2. Suboccipitofrontal
3. Occipitofrontal
4. Mentovertical
5. Submentovertical
6. Submentobregmatic
7. Biparietal
8. Bisacromial
9. Bitrochanteric

Question 25

Describe the suboccipitobregmatic diameter

Answer 25

- Below the occipital bone to the centre of the anterior fontanelle - 9.5cm

Question 26

Describe the suboccipitfrontal diameter

Answer 26

- Below the occipital bone to the centre of the frontal bone/ suture - 10cm

Question 27

Describe the occipitofrontal diameter

Answer 27

- The occipital protuberance to the glabella (frontal bone) | - 11.5cm

Question 28

Describe the mentovertical diameter

Answer 28

- From the point of the chin straight upwards to the highest point on the vertex - 13.5cm

Question 29

Describe the submentovertical diameter

Answer 29

- From the point where the chin meets the neck, straight upwards to the highest point on the vertex - 11.5cm

Question 30

Describe the submentobregmatic diameter

Answer 30

- From the point where the chin meets the neck to the centre of the bregma - 9.5cm

Question 31

Describe the biparietal diameter

Answer 31

- Stretched between the parietal eminences and is the engaging/crowning diameter - 9.5cm

Question 32

Describe the bisacromial diameter

Answer 32

- Stretched between the acromion processes on the 2 shoulder blades - Articulation of the clavicles on the sternum may reduce this diameter slightly - 12cm

Question 33

Describe the bitrochanteric diameter

Answer 33

- Stretches between the greater trochanters of the femurs - This is the presenting diameter in breech presentation - 10cm

Question 34

What are the 3 main types of presentation?

Answer 34

1. Vertex 2. Face 3. Brow

Question 35

Describe vertex presentation

Answer 35

- When head is well-flexed, sub-occipitobregmatic and biparietal diameters present - Sub-occipitofrontal diameter distends vaginal orifice - When head is deflexed, presenting diameters are occipitofrontal and biparietal - This arises when occiput is in posterior position - If this remains, occipitofrontal diameter distends vaginal orifice

Question 36

Describe face presentation

Answer 36

- When head is completely extended, presenting diameters are submentobregmatic and bitemporal - Submentovertical diameter distends the vaginal orifice

Question 37

Describe brow presentation

Answer 37

- Occurs when head is partially extended and mentovertical and bitemporal diameters present - Vaginal birth unlikely

Question 38

What are the 5 main possible presenting parts?

Answer 38

1. Cephalic 2. Breech 3. Face 4. Brow 5. Shoulder

Question 39

Define moulding

Answer 39

The change in shape of the foetal head that takes place during its passage through the birth canal

Question 40

Why does moulding occur?

Answer 40

- Bones of vault allow a slight degree of bending as they are soft and able to override sutures - Results from pelvic girdle pressure - Enables skull to alter shape and negotiate pelvis - Diameters can be increased/decreased up to 1.5cm - Frontal bones pushed to anterior edge of 2 parietal bones and occipital bone pushed under parietal bones

Question 41

What relevance do sutures and fontanelles have to practice?

Answer 41

- To diagnose position of foetal head in labour - Check foetal head for moulding - Placing SE clip away from fontanelle - Position is important for fixing ventouse cup

Question 42

What is the favourable position for labour?

Answer 42

``` Lie - longitudinal Presentation - cephalic Position - left/right occipitoanterior Attitude - flexion Denominator - occiput Presenting part - posterior part of anterior parietal bone ```

Question 43

Why is it important for the midwife to understand normal labour?

Answer 43

- To detect normal progresses of labour - Awareness of abnormal mechanisms - Aids delivery technique - Assists in recognising shoulder dystocia

Question 44

What does it mean if the fontanelle is sunk/ raised?

Answer 44

``` Sunk = dehydrated Raised = infection ```

Question 45

What may cause bleeding in the great cerebral vein?

Answer 45

A tear in the tentorium cerebella

Question 46

What is a caput succedaneum?

Answer 46

- Swelling caused by fluid under the skin - Caused by pressure on the cervix at delivery - Resolves within 24 hours

Question 47

What is a cephalic haematoma?

Answer 47

- Swelling seen over 1 of 2 parietal bones - Results in blood escaping from ruptured blood vessels between skull and periosteum - Caused by trauma during delivery (e.g. forceps, ventouse) - Occurs a few hours after birth up to 18 months