Scalp and Cranial Cavity Flashcards
What is the scalp?
The skin and subcutaneous tissue that covers the neurocranium from the superior nuchal line of the occipital bone to the supraorbital margins of the frontal bone
Laterally it extends over the temporal fascia to the zygomatic arch
What is the face?
The anterior aspect of the head from forehead to chin and from one ear to the other
What are the layers of the scalp?
Skin
Dense connective tissue
Epicranial aponeurosis
Loose connective tissue
Pericranium
Describe the skin of the scalp
Outermost layer
Contains hair follicles, sweat and sebaceous glands, thickest over the occipital bone
Describe the dense connective tissue of the scalp
Subcutaneous layer richly vascularised with cutaneous nerves
Describe the epicranial aponeurosis of the scalp
Tendon and muscle of occipitofrontalis
Prevents superficial wounds from gaping open - when this layer is compromised (laceration) gaping wounds result that require sutures to close
Describe the loose connective tissue of the scalp
Loose areolar tissue that allows free movement of outer layers over underlying calvaria
Contains spaces susceptible to distension with fluid or infection spread
Describe the pericranium of the skull
External periosteum of the skull
Why can fluid or infection spread to the eyelids or root of nose?
Between the aponeurosis and pericranium there are potential spaces for accumulation of fluid eg - blood
The frontal belly of the occipitofrontalis inserts into skin and subcutaneous tissue - not bone
Spread via emissary veins
Which nerves nerves innervates the scalp?
C2,3
CN V (1,2 and 3)
Which branches of CN Va innervate the scalp?
Supraorbital
Supratrochlear
Infratrochlear
External nasal
Lacrimal
Which branches of CN Vb innervate the scalp?
Zygomaticotemporal
Zygomaticofacial
Infraorbital
Which branches of CN Vc innervate the scalp?
Auriculotemporal
Buccal
Mental
Which branches of C2 and 3 innervate the scalp?
C2 - greater occipital
C3 - third occipital
C2,3 - great auricular and lesser occipital
What supplies the skin over the angle of the mandible?
Not CN V but by the cervical plexus with the great auricular nerve (C2 and 3)
Describe blood supply and drainage of the scalp
Arterial supply is from both the internal (anterior scalp) and external (lateral and posterior scalp) carotid arteries
Veins run alongside the arteries and have the same names draining to the EJV with the exception of the occipital vein that drains to the IJV
Which branches of the internal carotid artery and vein supply and drain the scalp?
Supraorbital
Supratrochlear
Which branches of the external carotid artery and vein supply and drain the scalp
Superficial temporal
Posterior auricular
Occipital - (occipital vein drains to IJV)
Why is profuse bleeding common in scalp lacerations?
Arterial anastomoses are prevalent in the scalp and these lie superficially
Describe lymphatic drainage of the scalp?
Posterior - mastoid and occipital nodes drain to deep cervical nodes
Anterior - pre-auricular and parotid nodes
Describe the anterior cranial fossa
Frontal ethmoid and sphenoid bones
Shallowest part of the cranial base
Occupied by the frontal lobes
What role does CN I play in the anterior fossa?
Olfactory bulbs receive nerve fibres from the nasal cavity via the foramina of the cribriform plate (olfaction)
How may cribiform plate fractures present?
With CSF rhinorrhoea
Describe the middle cranial fossa
Sphenoid and temporal bones
Occupied by the temporal lobes
Where is the pituitary gland found in the middle cranial fossa?
In the hypophyseal (pituitary) fossa - deepest part of the sella turcica
What surrounds the pituitary gland?
4 clinoid processes and 2 superior projections - dorsum sellae posteriorly and tuberculum sellae anteriorly
What foramina are found in the sphenoid bone?
Foramen rotundum - lateral
Pterygoid canal - medial
What are the main features of the sphenoid bone?
Greater wing
Lesser wing
Sphenoid sinus
Superior orbital fissure
Dorsum sellae
Medial pterygoid plate
Lateral pterygoid plate
What is the space between the medial and lateral pterygoid plates called?
The pterygoid fossa
Describe the posterior cranial fossa
Sphenoid, occipital and temporal bones
Occupied by the cerebellum and brainstem
What foramina are found in the posterior cranial fossa?
Foramen magnum
Jugular foramen
Hypoglossal canal
What are granular foveolae?
Arachnoid granulations that return CSF to the venous circulation
Describe the bone structure of the calvaria
Pericranium
External table
Diploë (compact bone)
Internal table
Dura
What are buttresses?
Thicker portions of cranial bone (pillars) that transmit forces around weaker regions of the cranium (bypassing orbits and nasal cavity)
Describe the frontonasal buttress
From the region of the canine teeth between the nasal and the orbital cavities to the central frontal bone
Describe the zygomatic arch-lateral orbital margin buttress
Describe the occipital buttresses
Transmit forces received lateral to the foramen magnum from the vertebral column
Name the different buttresses
Frontosagittal buttress
Frontonasal buttress
Zygomatic arch-lateral orbital margin buttress
Occipital buttress
What are cranial meninges?
Membranous layers that help in protection of the brain
Name the different cranial meninges
Dura mater
Arachnoid mater
Subarachnoid space
Pia mater
Describe the layers of the dura mater
Periosteal layer - attached to bone
Meningeal layer - in contact with arachnoid mater
These two layers separate at venous sinuses and dura folds
Describe the arachnoid mater
Lines the dura mater
Trabeculae project from internal surface, across the subarachnoid space and are continuous with the pia mater
Describe the subarachnoid space
Contains CSF and blood vessels
Arachnoid villi reabsorb CSF into the venous system
What are arachnoid granulations and where are they found?
Collections of arachnoid villi found in the sagittal sinus and lateral lacunae
Describe the pia mater
Thin membrane attached to the surface of the brain
As it adheres to the brain surface, it enters the sulci of the brain
What do dura mater folds do?
The limit the movement of the brain within the cavity
Name the dura mater folds
Falx Cerebri
Tentrorium cerebelli
Falx Cerebelli
Diaphragma Sellae
What supplies the dura mater and calvaria?
Meningeal arteries in the periosteal layer:
Anterior meningeal arteries
Middle and Accessory meningeal arteries
Posterior meningeal arteries
