8 - Scalp and cranial cavity Flashcards
What is the scalp?
- skin and subcutaneous tissue from superior nuchal line of occipital bone to supraorbital margins
- laterally scalp extends over temporal fascia to zygomatic arch
- covers the neurocranium
What is the face?
- anterior aspect of head from forehead to chin, and ear to ear
- covers viscerocranium
What are the different layers of the scalp?
- skin
- dense connective tissue
- epicranial aponeurosis
- loose connective tissue
- pericranium
What is the scalp proper?
- first 3 layers of scalp tissue
- skin, dense connective tissue. epicranial aponeurosis
- move together against the bottom two layers
Describe the skin of the scalp.
- outermost layer
- contains hair follicles, sweat and sebaceous glands
- thickest over occipital
Describe the dense connective tissue of the scalp.
- subcutaneous layer
- very vascularised (when lacerated, bleeds profusely)
- cutaneous nerves
Describe the epicranial aponeurosis.
- epicranius
- tendon and muscle layer of scalp called the occipitofrontalis
- prevents superficial lacerations from gaping open (when this layer is lacerated, these wounds gape)
What is the action of the occipitofrontalis?
Frontal belly - wrinkles forehead
Occipital belly - smoothes forehead
Describe the loose connective tissue of the scalp.
- loose areolar (“packing”) tissue
- allows movement of outer layers (scalp proper)
- described as spongy
- contains spaces that could be susceptible to infection
Describe the pericranium of the scalp.
- external periosteum of skull
- firmly attached and continuous with sutures (forms fibrous joints)
What is the danger area of the scalp?
- between the aponeurosis and pericranium there can be potential spaces for fluid accumulation or spread of infection
- infection can spread to eyelids or the root of the nose
- infection spreads forward as the occipitofrontalis inserts into soft tissue instead of bone
- infection spread via emissary veins
Describe the innervation of the scalp.
- cutaneous innervation is by the trigeminal (CN V) and cervical nerves C2 and C3
- aponeurosis is supplied by the facial (CN VII)
What are the branches of CN V1 and what area of the scalp/face do they innervate?
- supraorbital
- supratrochlear
- infratrochlear
- external nasal
- lacrimal
- forehead to external corner of the eye, to the tip of the nose
What are the branches of CN V2 and what area of the scalp/face do they innervate?
- zygomaticofacial
- zygomaticotemporal
- infraorbital
- temples, anterior portion of the cheekbones, upper lip, Ala of the nose
What are the sensory branches of CN V3 and what area of the scalp/face do they innervate?
- buccal
- mental
- auriculotemporal
- temporal fossa, anterior half of the ear, posterior portion of the cheekbones, lower lip, chin
What are the branches of C2 and what area of the scalp do they innervate?
- greater occipital
- vertex -> superior nuchal line,
What are the branches of C3 and what area of the scalp do they innervate?
- third occipital
- back of the neck, inferior to superior nuchal line
What are the branches of the cervical plexus and what area of the scalp do they innervate?
- great auricular
- lesser occipital
- posterior half of the ear, angle of the mandible, lateral side of the neck
What is the arterial supply of the scalp?
Anterior - ICA
Lateral - ECA
Posterior - ECA
What are the branches of the ICA that supply the scalp?
- supraorbital
- supratrochlear
What are the branches of the ECA that supply the scalp?
- superficial temporal
- posterior auricular
- occipital
What is the venous drainage of the scalp?
- EJV
- IJV
Describe the lymphatic drainage of the scalp.
Anterior - pre-auricular and parotid nodes
Posterior - mastoid and occipital nodes, drain into deep cervical nodes
What are the 3 fossa of the cranial cavity?
- anterior (most shallow)
- middle
- posterior
What divides the anterior and middle cranial fossa?
Sphenoid crest
What divides the middle and posterior cranial fossa?
Superior border of petrous temporal bone
Describe the anterior cranial fossa.
- frontal, ethmoid and sphenoid bones
- occupied by the frontal lobes
What is the crista galli?
- ridge in ethmoid
- site of attachment for falx cerebri
Where are the olfactory bulbs located?
- CN I
- receive fibres from the nasal cavity via the foramina in the cribriform plate
- lateral to cristi galli
Describe the middle cranial fossa.
- sphenoid and temporal bones
- occupied by temporal lobes
Where is the pituitary gland located?
- hypophyseal or pituitary fossa
- found in the deepest part of the sella turcica
- surrounded by bony projections (clinoid processes and dorsum sellae)
Describe the posterior cranial fossa.
- sphenoid, occipital and temporal bones
- occupied by brainstem and cerebellum
What is the clivus?
Where brainstem enters the foramen magnum (pons)
What is the foramen magnum?
- large foramen in the base of the skull
- medulla oblongata located here
What are granular foveolae?
Small indentations caused by arachnoid granulations that return CSF to venous circulation
What are buttresses?
- thicker portions of cranial bone that transmit forces around the weaker areas
- bypasses orbital and nasal cavity
Describe the frontonasal buttress.
- region of canine teeth
- between nasal and orbital cavities in the frontal bone
Describe the zygomatic arch-lateral orbital margin buttress.
Region of molars to lateral frontal and temporal bones
Describe the occipital buttress.
Transmits forces received lateral to foramen magnum from the vertebral column
What are the cranial meninges?
- membranous layer that help protect the brain
- dura mater
- arachnoid mater
- subarachnoid space
- pia mater
Describe dura mater.
- 2 layers, periosteal and meningeal
- periosteal layer is attached to bone
- menenigeal layer is in contact with arachnoid layer (in health)
- layers separate at venous sinuses and dural folds
Describe arachnoid mater.
- lines dura mater (in health)
- trabeculae project from in the internal surface and are continuous with Pia mater
- granulations project from external surface to return CSF to venous drainage
Describe the subarachnoid space.
- filled with CSF and blood vessels
- granulations project into sinuses to return CSF to venous drainage
Describe pia mater.
- thin membrane attached to surface of brain
- enters sulci of brain
What are the dura mater folds?
- falx cerebri
- tentorium cerebelli
- falx cerebelli
- diaphragma sellae
Describe the location of falx cerebri.
- largest
- runs along sagittal sinus between the two lobes
Describe the location of falx cerebelli.
- runs in midline
- separates the two lobes of the cerebellum
Describe the location of tentrorium cerebelli.
- runs transverse
- separates the cerebrum from the cerebellum
Describe the location of diaphragma sellae.
- smallest
- forms roof over pituitary fossa
What is the function of the dura mater folds?
Limit movement of the brain within the cavity.
What is the arterial supply of the dura mater?
- anterior meningeal arteries
- middle and accessory meningeal arteries
- posterior meningeal arteries
