Anatomy of the Skull Flashcards
What are the 2 parts of the skull?
cranium + mandible
What are the 2 parts of the cranium?
- neurocranium
- calvaria (skull cap)
- basicranium (cranial base) - viscerocranium
What are the subdivisions of the skull bones?
- cranial
- facial
Functions of the cranial bones?
- Site for head muscle attachment
- Encase brain and particular sense organs
Functions of facial bones?
- Site for facial muscle attachment
- Cavities for particular sense organs
i.Gustation
ii. Olfaction
iii. Vision - Framework for the face
- Openings for air and food passage
- Secure teeth
The cranium consists of?
Components?
- Calvaria
– dome shaped roof (skullcap)
– Forms the superior, lateral and posterior aspects as well as the forehead - Cranial base
– floor consisting of ethmoid, sphenoid , and parts of temporal and occipital bones
What is the cranial cavity?
Enclosed by?
the cavity covered by the calvaria and cranial base
What are the cavities of the skull?
- Cranial - contains Brain
- Orbits - Eyeballs
3.Paranasalsinuses- Nasal cavity - Middle and inner ear
What are the terms to describe various depressions and openings of the cranium?
Fissure - narrow opening between adjacent parts of bones for nerves and vessels
Foramen - hole, opening
Fossa - shallow depression
Sulcus - groove
Meatus - tube like passageway
What are sutures?
connections (joints) between bones of skull
- present with all bones of the skull except mandible
Name the cranial bone sutures?
a. Coronal
b.Sagittal
c.Squamous
d.Lambdoid
What are the characteristics of a fetal skull?
- Skull bones are unfused at birth
- Joined by membranes called Fontanelle
What are fontanelles?
- areas of fibrous tissue membrane separating the bones of the calvaria
- major fontanelles:
1. anterior
2. posterior
3. anterolateral (sphenoidal)
4. posterolateral (mastoid)
What is the function of fontanelles?
Fontanelles allow for rapid stretching and deformation of theneurocraniumas the brain expands faster than the surrounding bone can grow
Describe the anterior fontanelle?
- diamond/rhomboid in shape
- located at the junction of the sagittal, coronal and frontal sutures
- future site of bregma (point of junction of the coronal and sagittal sutures of the skull)
- ossifies by 18 months
Describe the posterior fontanelle?
- triangular in shape
- size = 1.2 x 1.2 cm
- formed by junction of 3 suture lines: sagittal suture anteriorly and lambdoid suture on either side
- begins to close during first 2 to 3 months after birth
Describe the closure and obliteration of sutures?
- cranial sutures start to ossify by age 8
- sutures on facial skeleton ossify earlier
- obliteration of cranial sutures progresses with age : between 20 - 30 years + before 40 years
- obliteration begins in the coronal suture then extends into sagittal and lambdoid sutures
Describe the closure of fontanelles at different ages?
- 6-8 weeks - posterior fontanelle
- 12-18 months - anterior fontanelle
- 12 years - sutures unable to be separated by increased intracranial pressure