The Scalp and Brain Flashcards
What are the layers of the scalp?
The scalp refers to the layers of tissue that cover the bones of cranial vault
Skin Contains sebaceous glands and hair follicles
Connective tissue Contains the nerves and vessels of the scalp
Aponeurosis Tough layer of dense fibrous tissue
Loose areolar tissue Contains emissary veins which pass into cranium
Periosteum Dense connective tissue covering outer skull surface
Label this
Describe blood supply to the scalp
These main branches supplying the scalp are all branches of the external carotid artery (a branch of the common carotid artery)
Superficial temporal runs along the temporal bone. Occipital runs along the occipital bone. Posterior auricular runs behind the ear (auricle is latin for ear)
How firmly attached are blood vessel walls to the scalp and what can this lead to?
The blood vessel walls are firmly attached to the connective tissue layer.
When lacerated, the cut ends of the scalp vessels do not readily constrict and retract.
Even a small scalp wound may bleed profusely creating a large haematoma. Scalp haematomas can be seen following ventouse delivery of a newborn, but will eventually be fully resorbed.
What are sutures?
Sutures are areas of contact between different bones of the skull and in these areas of contact we find fibrous tissue made of collagen.
What is this suture?
The coronal suture separates the frontal bone from the parietal bones.
The metopic/frontal suture splits the frontal bone in half. Present in infants but usually gets reabsorbed during development.
What is this suture?
The sagittal suture, which separates the parietal bones.
What is this suture?
The lambdoid suture which separates the occipital bone from the parietal bones.
What are these 2 sutures?
The squamous suture separates the squamous part of the temporal bone from the parieta bone.
The occipitomastoid suture separates the occipital bone from the mastoid part of the temporal bone
Label this
Why is this circled area important?
This is the pterion: found at the junction of the frontal, parietal, temporal and sphenoid bones. It’s thin bone and is the weakest part of the skull.
The anterior division of the middle meningeal artery (branch of maxillary artery) lies beneath the pterion.
A traumatic blow to the pterion may rupture the middle meningeal artery.
Pterion= crucial surgical landmark to approach the middle meningeal artery esp for lesions and brain tumors.
What are these junctions called?
The junction of the coronal and sagittal sutures is called the bregma.
The junction of the sagittal and occipital sutures is called the lambda
What are the names of the most posterior and anterior protruding points of the neurocranium?
The most posterior protruding point of the neurocranium= opistocranion
The most anterior protruding point of the neurocranium= glabella.
This measurement is used in studies of craniofacial growth to determine some craniofacial abnormalities
label the GREEN landmarks only
What are fontanelles?
A fontanelle is a soft membranous gap between the cranial bones that make up the calvarium (cranial vault) of a fetus/infant. Made of connective tissue
Fontanelles allow passage of the head through the birth canal w/o compressing the skull bones.
Allows deformation of the neurocranium as the brain expands rapidly in the first months of life.
Label and describe these fontanelles
The frontal metopic suture usually closes before the first year of life.
The sphenoid fontanelle fuses at ~6m.
The mastoid fontanelle fuses between 6-18m.
The anterior fontanelle closes between 18-24m. The posterior one fuses within 3 months after birth
How will each fontanelle close?
Each fontanelle will close by intramembranous ossification (direct conversion of mesenchymal tissue into bone).
In other cases, the mesenchymal cells differentiate into cartilage, which is later replaced by bone.
Clinical examination of a young child includes assessing the anterior fontanelle. What could a depressed fontanelle indicate? What could a bulging fontanelle indicate?
Ultrasound analyses the underlying brain and explores any potential pathologies.
Cranial ultrasound is not possible once the fontanelles have fused bc US waves cannot penetrate through bone.
Describe the cranial base and fossa
The internal side of the cranial base (skull cap/calvarium being removed), the floor of the cranial cavity can be subdivided into:
The anterior cranial fossa, which houses the frontal lobes of the brain.
The middle cranial fossa, which contains the temporal lobes of the brain and the pituitary gland.
The posterior cranial fossa which houses the brainstem and the cerebellum.
Which bones are in the cranial fossa?
Describe the internal view of the anterior cranial fossa
The anterior cranial fossa has 3 important elements:
The cribriform plate: olfactory nerve enters the nasal cavity through the ethmoid bone.
The bony ridge at the centre of the cribriform plate= crista galli. Anterior to it= foramen cecum. This is a small notch from the articulation between the frontal and ethmoid bone
Trauma to the front of the head may destroy the cribriform plate and olfactory nerve to cause anosmia (lack of smell)
Describe the internal view of the middle cranial fossa
In the middle cranial fossa hay a series of foramina which cranial nerves pass thru:
Superior orbital fissure provides passage to 3 motor nerves of the extraocular muscles (oculomotor, trochlear and abducens nerves).
Foramen rotundum allows passage of the maxillary nerve
Foramen ovale allows passage of the mandibular nerve
Describe the internal view of the posterior cranial fossa
Has other important foramina such as
The jugular foramen (allows the passage of the internal jugular vein)
Internal acoustic meatus (allows passage of the vestibulo- cochlear nerve which serves the auditory system)
Foramen magnum (point where cranial base articulates w C1. Allows the passage of the spinal cord. It’s forward position helps maintain fully erected bipedal locomotion).
What is labelled here?
