Cranium, meninges and brain Flashcards
What is meant by a craniotomised cadaver
Top of skull has been removed, dissected in a way that the brain has been removed- see structures inside the skull without the brain.
Summarise the head
The head is composed of a series of compartments, which are formed by bone and soft tissues. They are: the cranial cavity two ears two orbits two nasal cavities, and an oral cavity
What is meant by the cranial cavity
The cranial cavity is the largest compartment and contains the brain and associated membranes (meninges)
What is meant by the orbits
The two orbits contain the eyes. They are cone-shaped chambers immediately inferior to the anterior aspect of the cranial cavity, and the apex of each cone is directed posteromedially. The walls of the orbits are bone, whereas the base of each conical chamber can be opened and closed by the eyelids.
Which regions of the head does the scalp cover
The scalp coveres the superior, posterior, and lateral regions of the head.
Summarise the bones of the skull
Skull consists of 22 bones (excluding ossicles of ear)
Cranium:
Vault
Base
Mandible Facial skeleton (viscerocranium)
What can the cranium be subdivided into
An upper domed part (the calvaria or the vault)- which covers the cranial cavity containing the brain- basically houses the brain
a base- which consist of the floor of the cranial cavity
a lower anterior part- the facial skeleton (viscerocranium)
What forms the cranium
The skull has 22 bones, excluding the ossicles of the ear. Except for the mandible, which forms the lower jaw, the bones of the skull are attached to each other by sutures, are immobile and form the cranium.
List the bones forming the cranium
Frontal Parietal x2 Occipital Temporal x2 Sphenoid- deep in centre of skull Ethmoid- top of nose
List the bones forming the viscerocranium (facial skeleton)
Maxilla x2- teeth Zygoma x2- cheek Nasal x2 Lacrimal x2 Vomer Inferior conchae x2 Palatine x2 Mandible- largest bone in skull
Explain the two parts of the cranium
Neurocranium- houses the brain- contains the base- where the brain sits- where things enter and leave- cranial vault
Viscerocranium- facial skeleton (front of skull)
Describe the bones forming the calvaria
Mainly the paired temporal and parietal bones, and parts of the unpaired frontal, sphenoid and occipital bones.
Describe the bones forming the base
Parts of sphenoid, temporal and occipital
Describe the bones forming the facial skeleton
paired nasal bones, palatine bones, lacrimal bones, zygomatic bones, maxillae and inferior nasal conchae and unpaired vomer
What is important to remember about the mandible
Not part of the cranium nor part of the facial skeleton
Why do we sniff when we cry
Lacrimal bone- inside the orbit- related to the drainage apparatus of the lacrimal glands- which are found in the top corner of the eyes- drain across to the medial side into nasal cavity.
Summarise the vomer
single bone in the middle of the skull which points upwards into the nasal cavity
Summarise the conchae
infolding bones which form the nasal cavity- increase SA and humidify the air
Summarise the palatine bones
Hard bones at the roof of the mouth
What is meant by the sutures
The many bones of the head collectively form the skull. Most of these bones are interconnected by sutures, which are immovable fibrous joints
What is special about the skull in the fetus
Bones not fully fused
In the fetus and newborn, large membranous and unossified gaps (fontanelles) between the bones of the skull, particularly between the large, flat bones that cover the top of the cranial cavity. These allow:
the head to deform during its passage through the birth canal
These fontanelles are tough- not easy to damage
postnatal growth
Two frontal bones- separated by metopic suture
See diagram!!
What happens to these fontanelles
Most of the fontanelles close during the first year of life. Full ossification of the thin connective tissue ligaments separating the bones at the suture lines begins in the late twenties, and is normally completed in the fifth decade of life
Posterior fontanelle- closes between first 2-3 months
Anterior fontanelle- closes between first 18-24 months
Describe the bones of the superior view of the skull
Forms the superior part of the calvaria
Anterior to posterior:
The unpaired frontal bone articulates with the paired parietal bones at the coronal suture
The two parietal bones articulate with each other in the midline at the saggital suture
The parietal bones articulate with the unpaired occipital bone at the lamboid suture (also known as lamba)
What are the bregma and lambda seen in the superior view
Bregma- junction of the sagittal and coronal sutures
lambda- junction of sagittal and lamboid sutures