Anatomy Practical 1 Flashcards
Which are the cranial bones?
Frontal, parietal, occipital, temporal, sphenoid, ethmoid
Which are the facial bones?
Mandible, maxilla, zygomatic, nasal, lacrimal, palatine, vomer
What are the features of the temporal bone?
- petrous part
- zygomatic process -> zygomatic arch
- mastoid process
- styloid process
- external acoustic meatus
- internal acoustic meatus
What is the petrous part?
Thicker part of temporal bone
houses middle and inner ear
What passes through the internal acoustic meatus?
- vestibulocochlear nerve
- facial nerve
What is the zygomatic process?
Bar like part of temporal bone
Forms the zygomatic arch (cheek bone)
What is the mastoid process?
Anchoring site for some neck muscles
What is the styloid process?
Needle like
Attachment for tongue and pharynx
What are the features of the sphenoid bone?
Butterfly shaped
Articulates with all the other cranial bones
- central body, greater wings, lesser wings, 4 pterygoid plates
- foramen (5)
What are the 5 foramen in the sphenoid bone?
SOF Optic canals Foramen Rotundum Foramen Ovale Foramen Spinosum
What is the pterion?
Temple
Position of anterior branches of middle meningeal artery
Union of frontal, parietal, temporal, sphenoid bones
Skull at its thinnest point
Periosteum - groove which runs middle meningeal artery
What does the middle meningeal artery supply?
Dura and bone
When is middle meningeal artery impacted?
Intracranial haemorrhage
What are the features of the ethmoid bone?
Sieve through which air can pass
Cribiform plate on superior surface where olfactory bulbs of olfactory nerve sits
What are fontanelles?
Where bones of skull do not contact
Wide areas of fibrous tissue
Which bones contain air sinuses?
Frontal, sphenoid, ethmoid, 2 maxillary bones
What are paranasal air sinuses and what do they do?
Mucosa-lined air filled sinuses
Lighten the skull and enhance resonance of the voice
How many vertebrae are there in the spine and what are they separated by?
33
Intervertebral discs which act as shock absorbers
What are the common features of the vertebrae?
Body
Vertebral arch forming vertebral foramen where spinal cord passes through
Transverse and spinous process (attachment for muscles of back)
What is C1?
Atlas
vertebra which articulates with occipital condyles of the skull
What is C2?
Axis
Vertebra with a dens process, acts like a pivot, allows atlas to pivot around horizontal axis (shaking head to say no)
What is the sacrum?
Triangular Forms back of pelvis Formed by 5 fused vertebrae Laterally articulates with 2 hip bones forming sacroiliac joints Vertebral canal continues inside
What is the coccyx?
Triangular bone consisting of 4 fused vertebrae
What are the developmental parts of the brain?
Telencephalon (cerebral hemispheres) Diencephalon (thalamus, hypothalamus) Mesencephalon (midbrain) Metencephalon (pons, cerebellum) Myelencephalon (medulla oblangata)
What developments parts make up the forebrain, midbrain and hindbrain?
Forebrain - telencephalon, diencephalon
Midbrain - mesencephalon
Hindbrain - metencephalon, myelencephalon
What are the features of the midbrain on the ventral surface of the brainstem?
Short
Cerebral peduncles
What are the cerebral peduncles?
Massive bundles of nerve fibres descending from cerebral motor cortex to the brainstem and spinal cord carrying corticospinal tract
What are the features of the pons on the ventral surface of the brainstem?
Bridge like
Sharply demarcated
Ridged appearance
4 pairs of cranial nerves - CN V to VIII
Which cranial nerves are associated with the pons?
CNV-VIII Trigeminal Abducens Facial Vestibulocochlear
What are the features of the medulla on the ventral surface of the brainstem?
Medullary pyramids
Decussation for the corticospinal tracts
Inferior olive laterally
CN IX-XII
What cranial nerves are associated with the medulla?
CN IX-XII Glossopharyngeal Vagus Accessory Hypoglossal
What are the features of the midbrain on the dorsal surface of the midbrain?
2 paired swellings - inferior and superior colliculi
Buried beneath overlying cerebral hemispheres
CN III-IV
What is the obex?
1/3 of the way up the medulla
central canal
opening of the 4th ventricle
What is the function on the 4th ventricle?
Contains CSF that drains into the central canal of the spinal cord inferiorly and into the cerebral aqueduct superiorly
Where does the blood supply to the brainstem arise from?
Vertebral arteries
What do the internal carotid and vertebral arteries supply?
Internal carotid - anterior/superior of cerebrum
Vertebral arteries - posterior/inferior of cerebrum
What does the internal carotid divide into? What do these vessels supply?
Anterior cerebral in midline of cerebrum - lower limbs
Middle cerebral in lateral cerebrum - upper parts of body
What is the significance of the pontine-midbrain junction?
Basilar artery splits into the posterior cerebral artery
What branches does the basilar artery give off?
AICA - anterior inferior cerebellar artery
SCA - superior cerebellar artery
What is PICA derived from?
Posterior inferior cerebellar artery is derived from the vertebral arteries
Which arteries supply the cerebellum?
Posterior inferior cerebellar
Anterior inferior cerebellar
Superior cerebellar
What is the pathway of the olfactory nerve?
Receptor neurons in mucosa in roof of nasal cavity -> through cribiform plate of ethmoid bone -> reach olfactory bulbs in anterior cranial fossa where nerves synapse on
How can the olfactory nerve be damaged?
Olfactory fibre loss with aging
Injury to nasal mucosa/olfactory bulbs
Olfactory neurons torn away as pass through cribiform plate
What are the optic nerves surrounded by?
Extensions of cranial meninges and subarachnoid space
What are pathways of the optic nerves?
Pass in the orbit through optic canal and enter middle cranial fossa forming optic chiasm to then form optic tract
What happens at the optic chiasm?
Fibres from nasal/medial half of each retina decussate and join uncrossed fibres from lateral/nasal half of retina forming optic tract
What is the pathway of the oculomotor nerve?
Exit the midbrain -> through cavernous sinus -> divides into superior and inferior branches -> both pass through SOF -> innervate extraocular muscles and send presynaptic PS fibres to ciliary ganglion to innervate ciliary muscle and sphincter pupillae
Which muscles does the oculomotor nerve innervate?
All extra-ocular muscles except lateral rectus and superior oblique:
medial rectus, inferior oblique, inferior rectus, superior rectus, levator palpebrae superioris
How can lesions of the oculomotor nerve occur?
Pressure from herniating uncus
Fracture involving cavernous sinus
Aneurysms
Where is the uncus?
At the anterior and most medial portion of the temporal lobe
What is the pathway of the trochlear nerve?
Arises from posterior surface of midbrain -> passes anteriorly around brainstem -> pierces dura mater at tentorium cerebella -> passes lateral wall of cavernous sinus -> through SOF to superior oblique
What cranial nerves are on the dorsal surface of the brainstem?
Only trochlear
When may the trochlear nerve be damaged?
Torn when severe head injuries as has long intracranial course
What is a sign of trochlear nerve damage and why?
Double vision - diplopia when looking down
Superior oblique assists inferior rectus I depressing pupil and is only muscle to do so when eye is adducted
What is the pathway of the abducens nerve?
Emerges from the brainstem between the pons and medulla -> pierce dura -> enter SOF -> to lateral rectus
What can the abducens nerve be affected by and why?
By increased intracranial pressure - because of long intradural course and sharp bend along petrosal part of temporal bone
- pressure from atherosclerotic plaque in internal carotid
- cerebral aneurysm of circle of Willis
- septic thrombosis of sinus due to infection in nasal cavities or paranasal air sinuses
What does complete abducens nerve damage cause?
Medial deviation due to unopposed action of medial rectus
Diplopia
What is the pathway of the trigeminal nerve?
- Arises from lateral pons -> ganglion housed in dural recess lateral to cavernous sinus -> peripherally forms V1 ophthalmic V2 maxillary V3 mandibular
- motor root is smaller -> passes inferior to ganglion -> fibres join V3 supplying muscles of mastication
What is the pathway of the V1 ophthalmic nerve?
Passes anteriorly through lateral wall of cavernous sinus and through SOF
Divides into frontal nerve, nasociliary and lacrimal nerve
What is the pathway of the maxillary nerve?
Exits middle cranial fossa through foramen rotundum
What are the 3 divisions of the trigeminal sensory to?
V1 - cornea, upper conjunctiva, upper nasal mucosa, frontal and ethmoid sinus, anterior dura, superior eyelid, forehead/scalp
V2 - dura, middle cranial fossa, inferior conjunctiva, upper dentition and skin and mucous membranes associated with upper jaw
V3 - oral mucosa, anterior 2/3 of tongue, lower teeth and jaw, temporal regions of face and external ear
What is the pathway of the V3?
Leaves middle cranial fossa through foramen ovale
What are the 2 branches of the mandibular nerve?
Lingual nerve
Inferior alveolar nerve
What muscles does the mandibular nerve supply?
Lateral medial pterygoid Masseter Temporalis Mylohyoid Anterior belly of digastric Tensor tympani
What is the pathway of the facial nerve?
Arises from the pontine medullary junction lateral to abducens -> larger motor roots and smaller intermediate nerve carrying taste and PS fibres -> exits posterior cranial fossa through internal auditory meatus -> courses through temporal bone close to tympanic cavity -> gives rise to other nerves -> exits temporal bone through stylomastoid foramen -> enters parotid gland giving rise to terminal motor branches
What does the facial nerve give rise to in the temporal bone?
- greater petrosal nerve (PS to lacrimal gland)
- nerve to stapedius (dampens vibrations of stapes)
- chorda tympani (special sensory to anterior 2/3 of tongue, PS to submandibular ganglion)
Which cranial nerve is most frequently paralysed?
Facial nerve
What happens when there is damage to the facial nerve?
Depends on location of damage
Can cause paralysis of facial muscles with or without loss of taste or altered secretion from lacrimal or salivary glands
How can the facial nerve be damaged?
Motor branches are superficial so damaged through cuts, birth injury, fractured temporal bone, surgery to parotid or submandibular surgery
What is Bell’s palsy?
Unilateral facial paralysis of sudden onset
Lesion of facial nerve
Lesion near origin of facial nerve - paralysis of muscles on ipsilateral side
Central lesion (UML) - paralysis of muscles on contralateral inferior face
What is the pathway of the vestibulocochlear nerve?
Originates from pontine medullary junction -> exits posterior cranial fossa through internal acoustic meatus -> divides into cochlear and vestibular components
What is the function of the vestibulocochlear nerve?
- cochlear is sensory to spiral organ for hearing
- vestibular is sensory to semi-circular ducts for sense of equilibration
Which nuclei in the medulla send or receive fibres from the glossopharyngeal nerve?
- nucleus ambiguous (motor)
- inferior salivatory nucelus (motor)
- sensory of trigeminal nerve (sensory)
- solitary tract (sensory)
Which nuceli supplied via CN IX are shared with the vagus?
Nucelus ambiguous
Sensory of trigeminal
Solitary tract
What is the pathways of the glossopharyngeal nerve?
Exits the posterior cranial fossa through jugular foramen -> follows stylopharyngeus passing between superior and middle pharyngeal constrictors
What is the function of the glossopharyngeal nerve?
PS - parotid gland via otic ganglion
Somatic sensory and special sensory - posterior 1/3 of tongue and oropharynx
Carotid sinus nerve branch - carotid sinus (baroreceptor) and carotid body (chemoreceptor)
When would the glossopharyngeal be injured?
rare
Accompanied by X, XI injuries and signs as all pass through jugular foramen
Tumour creates multiple nerve palsies (JUGULAR FORAMEN SYNDROME)
What is the pathway of the vagus?
Arises from rootlets of lateral medulla -> exits the posterior cranial fossa through jugular foramen -> descends in carotid sheath through neck to root of neck -> lies between IJV and common carotid
What is the function of the vagus?
Somatic sensory to laryngopharynx and larynx
Visceral sensory from thoracic and abdominal organs
Somatic motor to palate, pharynx, larynx
Visceral motor (PS) to thoracic and abdominal organs
What does the vagus give rise to in the neck?
Pharyngeal branch (pharyngeal plexus) and superior laryngeal nerve
What do the pharyngeal branches supply?
Branches of the vagus
Supply muscles of pharynx and palate
Injuries to branches = dysphagia
What is the pathway of the spinal accessory nerve?
Arises from column of anterior horn motor neurons C1-C5/6 of spinal cord -> ascend into cranial cavity via foramen magnum -> exit through jugular foramen -> descends in carotid sheath -> pierces to innervate SCM -> emerges from posterior border of SCM and crosses to trapezius
Why is accessory nerve susceptible to injury?
During surgical procedures as travels superficially through posterior triangle to trapezius
What is the pathway of the hypoglossal nerve?
Exits cranium via hypoglossal canal -> spirals behind vagus to emerge between ICA and IJV -> lies on carotid sheath deep to muscles which attach to styloid process
What does injury to hypoglossal nerve result in?
Paralyses ipsilateral half of the tongue
Tongue may shrink and wrinkle over time
Why are the posterior communicating arteries so important?
Establish the circle of willis by linking anterior and posterior circulation
What carries out cerebral drainage?
Superficial and deep veins into dural sinuses which drain into the IJV
What is the confluence of the sinuses?
Junction of the straight, superior, sagittal and transverse sinuses
What are fissures?
Deep grooves
What are gyri?
Elevated folds/Ridges
What are sulci?
Shallow grooves between folds
What is each lobe divided into?
3 gyri and 2 sulci
What is the function of the cerebral cortex?
Enables us to be aware of ourselves and our sensations, communicate, remember, understand, initiate voluntary movements
What is the cortex composed of?
Gray matter (cell bodies) only
What is each hemisphere concerned with?
Sensory and motor functions of contralateral side of the body
What is lateralisation?
Hemispheres are symmetrical in structure but not entirely equal in function
What is the homunculus?
Mapping - amount of cortex devoted dependent on motor control of specific body region or region sensitivity
