Fetal Skull Flashcards

1
Q

List three evolutionary adaptations that enable human birth?

A

Birth while the fetus’ brain is immature (with rapid development after birth), the ability to flex the head, and moulding of the skull.

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2
Q

What are the layers of the scalp?

A

Skin, dense connective tissue, epicranial aponeurosis, loose areolar connective tissue and the periosteum.

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3
Q

What are the layers of the skull?

A

The periosteum, skull bone, dura mater, subdural space, subarachnoid space, brain.

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4
Q

The fetal skull is divided into which three regions?

A

The vault, base and face.

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5
Q

Describe the vault.

A

The large, dome-shaped part of the skull. Divided by an imaginary line between the orbital ridges and the nape of the neck.

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6
Q

The vault is comprised of which 7 bones?

A

The occipital bone, two parietal bones, two frontal bones and two temporal bones.

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7
Q

Describe the base.

A

Contains 8 bones that are fused. Provides protection for the brain steam.

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8
Q

Describe the face.

A

Extends from the orbital ridges and the root of the nose to the junction of the chin and neck.

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9
Q

Define fontanelle.

A

Where three or more sutures meet. A membranous gap between the edges of skull bones.

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10
Q

What are sutures?

A

Membranous divisions between the skull bones where ossification is incomplete.

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11
Q

What are the advantages of sutures and fontanelles?

A

They allow moulding during birth and expansion of the brain during childhood.

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12
Q

What are the main sutures?

A

The frontal suture, sagittal suture, lambdoidal suture and coronal suture.

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13
Q

Describe the position of the frontal suture.

A

Runs between the two frontal bones.

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14
Q

Describe the position of the sagittal suture.

A

Runs between the two parietal bones.

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15
Q

Describe the position of the lambdoidal sutures.

A

Run between the parietal and occipital bones

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16
Q

Describe the position of the coronal sutures.

A

Run between the frontal and parietal bones.

17
Q

What is another term for the anterior fontanelle?

A

Bregma

18
Q

What is another term for the posterior fontanelle?

A

Lambda

19
Q

Describe the anterior fontanelle.

A

It is kite shaped, and found at the junction of the sagittal, coronal and frontal sutures. It is 3-4cm long.

20
Q

Describe the posterior fontanelle.

A

It is small and triangular and found at the junction of the lambdoidal and sagittal sutures.

21
Q

When does the anterior fontanelle close?

A

It is usually closed by the time the child is 18 months old.

22
Q

When does the posterior fontanelle close?

A

It is usually closed by 6 weeks of age.

23
Q

What are the two transverse diameters of the fetal skull?

A

The biparietal and bitemporal diameters.

24
Q

How long is the biparietal diameter?

A

9.5cm

25
Q

How long is the bitemporal diameter?

A

8.5cm

26
Q

How many longitudinal diameters of the fetal skull are there?

A

6

27
Q

How long is the sub-occipito bregmatic diameter?

A

9.5cm

28
Q

How long is the sub-occipito frontal diameter?

A

10.5cm

29
Q

How long is the occipito-frontal diameter?

A

11.5cm

30
Q

How long is the mento-vertical diameter?

A

13.5cm

31
Q

How long is the sub-mento bregmatic diameter?

A

9.5cm

32
Q

How long is the sub-mento vertical diameter?

A

11cm.

33
Q

What does the attitude of the fetal head describe?

A

The degree of flexion or extension of the head on the neck.

34
Q

Why is it optimal that the sub-occipito bregmatic and biparietal diameters present?

A

It is a vertex presentation, where both diameters are the same length. The presenting area is therefore circular, and is most favourable for even dilatation of the cervix.

35
Q

Moulding can reduce/extend the skull in different directions by what length?`

A

1-1.5cm.