Fetal Skull Flashcards
List three evolutionary adaptations that enable human birth?
Birth while the fetus’ brain is immature (with rapid development after birth), the ability to flex the head, and moulding of the skull.
What are the layers of the scalp?
Skin, dense connective tissue, epicranial aponeurosis, loose areolar connective tissue and the periosteum.
What are the layers of the skull?
The periosteum, skull bone, dura mater, subdural space, subarachnoid space, brain.
The fetal skull is divided into which three regions?
The vault, base and face.
Describe the vault.
The large, dome-shaped part of the skull. Divided by an imaginary line between the orbital ridges and the nape of the neck.
The vault is comprised of which 7 bones?
The occipital bone, two parietal bones, two frontal bones and two temporal bones.
Describe the base.
Contains 8 bones that are fused. Provides protection for the brain steam.
Describe the face.
Extends from the orbital ridges and the root of the nose to the junction of the chin and neck.
Define fontanelle.
Where three or more sutures meet. A membranous gap between the edges of skull bones.
What are sutures?
Membranous divisions between the skull bones where ossification is incomplete.
What are the advantages of sutures and fontanelles?
They allow moulding during birth and expansion of the brain during childhood.
What are the main sutures?
The frontal suture, sagittal suture, lambdoidal suture and coronal suture.
Describe the position of the frontal suture.
Runs between the two frontal bones.
Describe the position of the sagittal suture.
Runs between the two parietal bones.
Describe the position of the lambdoidal sutures.
Run between the parietal and occipital bones
Describe the position of the coronal sutures.
Run between the frontal and parietal bones.
What is another term for the anterior fontanelle?
Bregma
What is another term for the posterior fontanelle?
Lambda
Describe the anterior fontanelle.
It is kite shaped, and found at the junction of the sagittal, coronal and frontal sutures. It is 3-4cm long.
Describe the posterior fontanelle.
It is small and triangular and found at the junction of the lambdoidal and sagittal sutures.
When does the anterior fontanelle close?
It is usually closed by the time the child is 18 months old.
When does the posterior fontanelle close?
It is usually closed by 6 weeks of age.
What are the two transverse diameters of the fetal skull?
The biparietal and bitemporal diameters.
How long is the biparietal diameter?
9.5cm
How long is the bitemporal diameter?
8.5cm
How many longitudinal diameters of the fetal skull are there?
6
How long is the sub-occipito bregmatic diameter?
9.5cm
How long is the sub-occipito frontal diameter?
10.5cm
How long is the occipito-frontal diameter?
11.5cm
How long is the mento-vertical diameter?
13.5cm
How long is the sub-mento bregmatic diameter?
9.5cm
How long is the sub-mento vertical diameter?
11cm.
What does the attitude of the fetal head describe?
The degree of flexion or extension of the head on the neck.
Why is it optimal that the sub-occipito bregmatic and biparietal diameters present?
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.
Moulding can reduce/extend the skull in different directions by what length?`
1-1.5cm.
