7.12&13&14&15 - Head, Neck & Spine 1 Flashcards
What are the features of the top of the skull?
- frontal bone
- parietal bone
- occipital bone
- coronal suture - separates frontal bone from parietal bone
- sagittal suture
- lambdoid suture - separates occipital bone from parietal bone
- bregma - where sagittal suture meets coronal suture
- lambda - where sagittal suture meets lambdoid suture
What is the squamous suture?
- separates squamous temporal bone and parietal bone
What are the features of the skull?
- bones - frontal, parietal occipital, temporal, sphenoid, maxilla, zygomatic ethmoid, palatine
- cranial fossae - anterior, middle, posterior
- main sutures - coronal, sagittal, lambdoid
- main fissures - superior orbital, inferior orbital
- mandible
What differences to an adult skull can we see when looking at a neonatal skull?
- juvenile skull - anterior and posterior fontanelles
- anterior fontanelle are where there is unfused bone, which gives the skull mild flexibility in case the birth canal is too tight
- also allows the brain to grow, and the bones to expand
- this ‘soft spot’ on the top of the baby’s head closes up at 18-24 months
Which joint in the head can move?
- the temporomandibular joint
- the sutures are rigid, immobile, thick fibrous joints
What is the name of the spot where the four cranial bones come together?
- pterion
- weakest part of the skull - a blow to this area may rupture the middle meningeal artery which runs beneath the pterion
- rupture may give rise to an epidural haematoma
What are the major bones of the skull?
- frontal
- parietal
- occipital
- temporal
- sphenoid (bow-shaped bone behind eyes)
- zygomatic (cheekbones, just below eyes)
- mandible (jawbone)
- maxilla (upper jaw, houses teeth)
- nasal
- lacrimal (located in eye socket)
- ethmoid (roof of nose, separates nasal cavity from brain)
- palatine (sides of nose)
- vomer (inside nose, divides right and left sides of nasal cavity)
Base of skull foramina
- foramina on cribriform plate
- optic canal
- superior orbital fissure
- foramen rotundum
- foramen lacerum - anterior to the opening of the carotid canal
- foramen spinosum
- foramen ovale (second biggest)
- internal acoustic meatus
- jugular foramen
- foramen magnum (biggest hole)
- hypoglossal canal
- opening of carotid canal
- stylomastoid foramen
What are the layers of the SCALP?
- skin
- connective tissue
- aponeurosis
- loose areolar tissue
- pericranium/periosteum
Blood supply of the scalp
External carotid artery branches:
- superficial temporal
- occipital
- posterior auricular
Internal carotid artery branches:
- supraorbital
- supratrochlear
- venous drainage through veins corresponding to the named arteries, and through emissary veins to the dural venous sinuses
Why do deep lacerations to the scalp tend to bleed profusely?
- the pull of the occipitofrontalis muscle prevents the closure of the bleeding vessel and surrounding skin
- blood vessels to the scalp are adhered to dense connective tissue, preventing the vasoconstriction that normally occurs in response to damage
- the blood supply to the scalp is made up of many anastomoses, which contribute to profuse bleeding
What is the falx cerebri?
- AKA cerebral falx
- large, crescent-shaped fold of meningeal layer of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres
What are dural reflections?
- the meningeal layer of dura mater folds inwards upon itself to form four dural reflections
- these reflections project into the cranial cavity, dividing it into several compartments - each of which houses a subdivision of the brain:
- falx cerebri - projects downwards to separate the right and left cerebral hemispheres
What are dural venous sinuses?
- venous drainage of the brain occurs through a system of cerebral and cerebellar veins, which in turn drain into the dural venous sinuses
- dural venous sinuses ultimately empty into the internal jugular veins which, together with the external jugular vein (draining the scalp and face), returns blood from the head and neck region back to the heart
- most are found adjacent to the falx cerebri and tentorium cerebelli
- cavernous sinus is clinically the most important dural venous sinus
What are the seven major dural venous sinuses?
- seven major dural venous sinuses located within the cranial cavity, specifically between the periosteal and meningeal layer of the dura mater
- superior sagittal
- inferior sagittal
- straight
- transverse
- sigmoid
- cavernous
- superior petrosal sinuses
Middle meningeal artery
- largest meningeal artery
- branch of the maxillary artery that arises from the external carotid artery
- provides major blood supply to the dural mater
- this artery enters the skull via the foramen spinosum (sphenoid bone)
Explain the anatomical basis of extradural and subdural haemorrhages
- haematoma - collection of blood - as the cranial cavity is effectively a closed box, a haematoma can cause a rapid increase in intra-cranial pressure –> death
- extradural haematoma (EDH) - arterial blood collects/clots between the skull and peiosteal layer of the dura - causative vessel is usually the middle meningeal artery, tearing as a consequence of brain trauma
- subdural haematoma (SDH) - venous blood collects/clots between the dura and the arachnoid mater - results from damage to cerebral veins as they empty into the dural venous sinuses
What do the CT scans for haemorrhages look like?
- SDH = crescent/banana shaped
- EDH = lens shape
- SAH - dark spaces whitish
Where can epidurals be delivered?
- there is an epidural space within the vertebral column, but not in the cranial cavity
- anaesthetist can use epidural/extradural space to deliver epidural anaesthetics e.g. mothers in labour
Where is the foramen magnum and what happens there?
- the big hole where the brainstem and spinal cord come together
Which arteries go through the carotid canal?
Internal carotid arteries
What is the vertebral column?
- series of vertebrae arranged on top of each other to support body weight and transmit it to the lower limbs through pelvic girdle
- 33 vertebrae - 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused into sacrum) and 4 coccygeal (fused)
- antero-posterior view - vertebral column appears as a vertically straight column
- lateral view - 4 curvatures in cervical, thoracic, lumbar and sacral regions
- curves in C and L regions are convex anteriorly (secondary curvatures) whereas curves in T and S regions are concave anteriorly (primary curvatures)
- first cervical vertebra (atlas) articulates with the skull base at the occipital condyles
What is the structure of a typical vertebra?
- typically, a vertebra has a vertebral body, two pedicles, two laminae, two transverse processes and a single spinous process
- the body, pedicles and laminae form the boundaries of a central space, the vertebral foramen
- most vertebrae have a pair of superior and inferior articular processes to form interlocking joints to allow some degree of flexibility
- foramina of the adjacent vertebrae of the vertebral column form the vertebral canal in which the spinal cord and the meninges are located
- pedicles have superior and inferior vertebral notches on superior and inferior aspects respectively
What is an intervertebral foramen?
- when adjacent vertebra are stacked on top of each other, the inferior vertebral notch of the vertebra above and the superior vertebral notch of the vertebra below form an intervertebral foramen
- the segmented spinal nerves from the spinal cord pass through the intervertebral foramen
What are intervertebral discs?
- adjacent vertebral bodies are united by intervertebral discs forming a secondary cartilaginous (symphysis) type of joint
- the disc has a central core of soft hydrophilic material, the nucleus pulposus, and an outer part made of tough annulus fibrosus
Lumbar puncture
- in adults, the spinal cord ends between L1 and L2 vertebrae
- the meningeal coverings and subarachnoid space contains CSF and extends up to the level of the S2 vertebra
- a sample of CSF can be obtained without damaging the spinal cord by accessing the subarachnoid with a lumbar puncture needle between the levels of L3-L5
- the site for lumbar puncture is chosen between L4&L3 or L4&5
- the L4 vertebra lies at a plane that passes through the highest points of the iliac crests - easily surface marked on posterior surface of the trunk by palpating top of iliac crests
Spinal cord anatomy (clockwise)
- dorsal horn
- grey matter
- ventral horn
- white matter
- ventral rootlets
- ventral root - efferent neurone
- mixed spinal nerve
- dorsal root ganglion
- dorsal root - afferent neurone
- dorsal rootlets
What is the structure of the spinal cord?
- composed of segments - each gives rise to a pair of mixed spinal nerves
- cervical (8), thoracic (12), lumbar (5), sacral (5), coccygeal (1)
- nerves emerge through intervertebral foramina
- relationship between nerves and foramina changes between cervical and thoracic regions
- nerves C1-C7 emerge above vertebrae
- nerves C8-Co1 emerge below vertebrae
Which cranial nerve passes through the cribriform plate?
olfactory nerve (CN I)
Which cranial nerve passes through the optic canal?
optic nerve (CN II)
Which two cranial nerves pass through the internal acoustic meatus?
facial (VII) and vestibulocochlear (VIII)
Which cranial nerve passes through the foramen ovale?
mandibular nerve (CN V3) - type of trigeminal nerve
Which four cranial nerves pass through the superior orbital fissure?
- oculomotor nerve (CN III)
- trochlear nerve (CN IV)
- ophthalmic nerve (CN V1) - type of trigeminal nerve
- abducens nerve (CN VI)
Which cranial nerve passes through the foramen rotundum?
maxillary nerve (CN V2) - type of trigeminal nerve
The facial nerve exits the skull base through which foramen?
stylomastoid foramen
Which cranial nerve, artery and vein passes through the foramen spinosum?
- meningeal nerve of the mandibular nerve (CN V3)
- middle meningeal artery
- middle meningeal vein
Which three cranial nerves pass through the jugular foramen?
- glossopharyngeal (IX)
- vagus (X)
- accessory (XI)
Which cranial nerve passes through the hypoglossal canal?
- hypoglossal nerve (CN XII)
