Anatomy Flashcards
What are the 2 major divisions to the bones of the skull?
Cranial bones and facial bones.
What is the face suspended from and what does it include?
From the front of the cranium. Includes the orbits, jaw and facial bones.
What are the divisions of the cranium?
Vault and floor (or base)
What are the properties of the bones constituting the cranium?
Made up of internal and external tables of compact bone with spongy bone in between.
What are the 4 major suture joints of the cranium?
Coronal, sagittal, lambdoid and the pterion.
Where is the coronal suture?
In the coronal plane between the frontal bone anteriorly and the parietal bones posteriorly.
Where is the sagittal suture?
In the sagittal plane between the two parietal bones and posterior to the frontal bone and anterior to the occipital bone.
Where is the lambdoid suture?
Between the parietal bones anteriorly and the occipital bone posteriorly.
What is the pterion considered a landmark for?
The middle meningeal artery, which grooves its internal surface.
Why is the suture of the pterion different to others?
It is not linear, rather H-shaped, comprising of sutures between the frontal, parietal, greater wing of sphenoid and squamous part of temporal bone.
What are the 2 plates of the frontal bone?
Vertical and horizontal plates.
What does the vertical plate of the frontal bone comprise?
The forehead
What comprises the roofs of the orbits?
The horizontal plate of the frontal bone.
What is the line of demarcation between the vertical and horizontal plates of the frontal bone?
The supraorbital margins.
What common shape do the bones of the cranium have?
Flat, rectangular and moulded to the shape of the underlying brain.
What are the cranial bones?
Frontal, parietal, occipital, temporal, ethmoid and sphenoid bones.
Which of the cranial bones lack projections or protuberances?
Frontal bone and parietal bone.
What is the protuberance off the occipital bone?
The external occipital protuberance
Which part of the temporal bone is moulded to the shape of the brain?
The squamous part of the temporal bone.
What are the 4 processes off the temporal bone?
Zygomatic, mastoid, styloid and petrious processes.
Where does the zygomatic process project? What does it articulate with?
Projects anteriorly, articulating with the zygoma.
What does the mastoid process allow for?
Attachment of muscles such as sternocleidomastoid.
What does the styloid process allow for the attachment of?
Oral and pharyngeal muscles.
Which is the most medial of the 4 cranial processes?
Styloid
What is the petrious process?
The wedge-shaped projection of temporal bone into the cranial floor.
What are the different parts to the sphenoid?
Body and lesser and greater wings.
What divides the sphenoid into lesser and greater wings?
The superior orbital fissure.
What is the sella turcica?
The depression in the body of the sphenoid for the pituitary gland.
Where is the lesser wing located in relation to the greater wing of sphenoid?
Anterosuperior
Where is the ethmoid bone located?
In the midline of the frontal bone.
What is the cribriform plate?
The part of the ethmoid bone either side of crista galli with foraminae for projections of olfactory nerves.
What are the 3 fossae in the base of the skull?
Anterior, middle and posterior cranial fossae.
Where do all cranial nerves emerge from and have their distributions?
Emerge from inferior aspect of the brain. All have their distributions outside of the cranium.
What are the foraminae in the base of the skull for?
Cranial nerves to exit
What does the anterior cranial fossa support?
The frontal lobe
What comprises the anterior cranial fossa?
Frontal bone, ethmoid bone and lesser wings of sphenoid.
What does the middle cranial fossa support?
The temporal lobe
What comprises the middle cranial fossa?
Body and greater wings of sphenoid and petrous part of the temporal bone.
What forms the step between the middle and posterior cranial fossae?
Petrous part of temporal bone.
What does the posterior cranial fossa support?
The cerebellum
What comprises the posterior cranial fossa?
Occipital bone
Which foramen is found in the anterior cranial fossa? Which nerves project through there?
Cribriform plate
Olfactory nerve
Which foramina are found in the middle cranial fossa? Which nerves project through them?
- Hypophysial fossa (pituitary gland)
- Optic canal (optic nerve, ophthalmic artery)
- Superior orbital fissure (nerves to extraocular muscles and branches of trigeminal nerve)
- Foramen rotundum (maxillary nerve)
- Foramen ovale (mandibular nerve)
- Foramen spinosum (middle meningeal artery)
Which foramina are found in the posterior cranial fossa? Which nerves project through them?
Internal acoustic meatus (facial and vestibulocochlear nerves)
Jugular foramen (IX, X, XI, internal jugular vein)
Hypoglossal canal (hypoglossal nerve)
Foramen magnum
What comprises the ‘arc’ of fissures/foramina?
Superior orbital fissure
Foramen rotundum
Foramen ovale
Foramen spinosum
Which foramen is a ‘hole’ in the ‘step’ of the petrous part of the temporal bone?
Internal auditory meatus
Which foramen is a hole between the temporal and occipital bones?
Jugular foramen
Which of the foramina is actually closed off by a membrane?
Foramen lacerum
Where is the optic canal located on the cranial side?
Between the body of the sphenoid and lesser wing of sphenoid.
What are the 3 meningeal layers?
- Dura mater
- Arachnoid mater
- Pia mater
What are the properties of the dura mater?
- Outer layer
- Rough
- Fibrous
- Attached to the skull
- External and Internal layers
Where will blood collect in the meninges if there is a rupture to the middle meningeal artery?
In the potential space between the dura mater and the skull.
Which layer of the meninges is delicate, thin and attached to the brain?
Pia mater
Where in the meninges will blood collect if there is a rupture to a vein?
In the subdural space between the dura mater and the arachnoid mater.
What creates the external layer of the dura mater?
The periosteum of the skull.
What creates the dural projections/septa?
The inner layer of the dura mater leaving the external layer to project into the cranial cavity.
What creates the venous sinuses?
The internal layer of the dura mater leaving the external layer to project into the cranial cavity, leaving behind a sinus at the points of separation.
Why are infections of the scalp and bone able to spread into the brain?
Because the emissary veins from the scalp and the diploic veins from the skull bones drain into the venous septa.
What is the term given to the infection that manages to reach the meninges?
Meningitis
What does meningitis become if it spreads into the brain from the meninges?
Encephalitis
What do the dural septa lodge into?
The subdivisions of the brain.
How do the dural septa help protect the brain?
They prevent the brain from rotating within the cavity.
What are the 4 major dural septa?
Falx cerebri
Tentorium cerebelli
Falx cerebelli
Diaphragm sellae
Where is the falx cerebri found?
In the midline between the two cerebral hemispheres in the sagittal plan, attached in line with the sagittal suture, the crista galli anteriorly and the internal aspect of the occipital protuberance posteriorly.
Where is tentorium cerebelli found?
Attached to the margins of the posterior cranial fossa, forming an almost horizontal roof over it.
What does tentorium cerebelli separate?
The cerebral hemispheres from the cerebellum below.
Where is the falx cerebelli found?
Below tentorium cerebelli, attached posteriorly to the occipital bone.
Separates the two cerebelli.
Where is diaphragma sellae found?
Roofing the turkish saddle (body of sphenoid).
What lines the venous sinuses?
Endothelium
What are the 4 major venous sinuses?
- Superior sagittal sinus
- Inferior sagittal sinus
- Straight sinus
- Cavernous sinus
Where do the venous sinuses receive venous blood from?
All veins draining the brain
The diploic veins
The emissary veins.
How is the straight sinus formed?
When the inferior sagittal sinus meets the great cerebral vein.
What is the confluence of sinuses?
Where the superior sagittal sinus, straight sinus and occipital sinus meet at the posterior aspect of the skull.
What happens to blood arriving at the confluence of sinuses?
Blood drains into the left and right transverse sinuses. The superior sagittal sinus drains into one and the straight sinus into the other, however the two never meet.
What forms the cavernous sinuses?
The dura either side of the body of the sphenoid
What is the course of the transverse sinuses?
They run laterally in a groove along the interior surface of the occipital bone until they reach the petrous part of the temporal bone, where they become the sigmoid sinuses.
What is the course of venous blood after the transverse sinus?
Enters into the sigmoid sinus at the petrous part of the temporal bone and then follows a tortuous course inferiorly towards the base of the skull and exits the cranium as the internal jugular vein.
Which arteries supply the meninges and bone of the skull?
Meningeal arteries
Where do the meningeal arteries sit?
In the extradural space.
Which artery is the largest meningeal artery and a branch off the maxillary artery?
Middle meningeal artery.
Where does the middle meningeal artery enter the cranium?
Through foramen spinosum
Which space would a rupture of the middle meningeal artery haemorrhage into?
Extradural space
In which space do the superior cerebral veins sit?
Subdural space.
What is the most classic cause of subdural haemorrhage?
A tear where the superior cerebral veins enter into the superior sagittal sinus.
Where does the scalp extend across?
From the external occipital protuberance posteriorly, over the forehead anteriorly to the superior orbital margins. From the level of the zygomatic arches laterally.
What are the 5 layers of the scalp?
- Skin
- Connective tissue (dense)
- Aponeurosis
- Loose connective tissue
- Periosteum/pericranium
How is the skin able to slide over the scalp?
Because the loose connective tissue layer allows the skin, connective tissue and aponeurosis to slide over the pericraniumm
What creates the aponeurosis of the scalp?
The occipitofrontalis muscle extending its aponeurosis between the occipitalis belly posteriorly and the frontalis belly anteriorly.
In which layer of the scalp does the neurovascular plane lie?
Connective tissue layer (Layer 2)
What are the 3 reasons a scalp laceration will bleed profusely?
- Rich anastomoses between internal and external carotid arteries
- A large gape will form because occipitofrontalis will pull the laceration open
- The connective tissue layer has fibrous septa holding the vessels open, restricting vasoconstriction
Why can an infection of the scalp lead to meningitis and potentially encephalitis?
Because the veins of the scalp communicate with the venous sinuses internally via emissary veins.
Which layer of the scalp is not present in the face?
Connective tissue layer 4.
What is present instead of an aponeurosis in the face?
Muscles of facial expression.
Where do the muscles of facial expression originate and insert?
Originate from bone or fascia and insert into the skin of the face.
How are the muscles of the face organised?
To surround the facial orifices, acting either as sphincters (orbicularis) or dilators (depressor or dilator)
Which pharyngeal arch are all facial muscles derived from?
2nd pharyngeal arch
How many pharyngeal arches are there?
6
Which pharyngeal arch never develops?
5th pharyngeal arch
What is each pharyngeal arch supplied by?
A cranial nerve
Which nerve supplies the muscles of the 2nd pharyngeal arch?
Facial nerve (CNVII)
Which cranial nerve supplies sensory innervation to the front of the head?
Trigeminal nerve (CNV)
What are the 3 branches of the trigeminal nerve?
- Ophthalmic
- Maxillary
- Mandibular
Where is the posterior border of trigeminal innervation to the face?
At the ears
Which nerve supplies sensory innervation to the posterior aspect of the head and neck?
Cervical spinal nerves C2 and C3
What does cervical spinal nerve C1 lack?
Sensory afferents
What is trigeminal neuralgia?
Brief episodes of facial pain in one of the divisions of the trigeminal nerve.
Where is the trigeminal ganglion located?
In the middle cranial fossa, covering the trigeminal impression near the apex of the petrous part of the temporal bone.
Which two arteries provide all blood supply to the face and scalp?
Internal and external carotid arteries.
What part of the face does the internal carotid artery supply?
Centre of the forehead.
What are the two branches off the internal carotid artery that supply the face?
Supratrochlear and supraorbital arteries.
Which of the two branches off the internal carotid artery suppplying the face is more medial?
Supratrochlear
Which artery is the main supply to the face?
Facial artery (branch of external carotid artery)
What is the course of the facial artery?
The facial artery winds over the inferior border of the mandible (after coming off the external carotid), where it follows a tortuous course to the medial angle of the eye, giving off branches on its way.
Where does the superficial temporal artery arise from?
The external carotid artery at the zygomatic arch.
Which artery supplies the posterior aspect of the scalp?
The occipital artery coming off the external carotid.
Which 3 arteries supplying the face and scalp arise from the external carotid artery?
- Facial artery
- Superficial temporal artery
- Occipital artery
What is the course of the facial vein?
Runs posteriorly to the facial artery, but is more straight and superficial than the facial artery.
What is the main vein draining the face?
Facial vein
What is the danger triangle of the face?
A triangle running from the corners of the mouth to the bridge of the nose.
What is dangerous about the danger triangle of the face?
Any infection in this triad risks meningitis because this area drains to the cavernous sinuses.
Where does lymph from the face and scalp drain?
Into a ring of lymph nodes at the bottom of the mandible.
Where does lymph from the ring of lymph nodes at the bottom of the mandible drain to?
Deep cervical lymph nodes of the neck.
What is the parotid?
A serous salivary gland.
Where is the parotid?
- Inferior to the zygomatic process
- Anterior to the mastoid process and the ear
- Superior to the angle of the mandible
- Posterior to masseter
- Superficial to the styloid process
What encases the parotid?
Very dense envelope of parotid fascia.
What are the structures within the parotid (superficial to deep)?
- CNVII
- Retromandibular vein
- External carotid artery
- Parotid lymph nodes (actually scattered throughout, not necessarily deeper)
What is the course of the parotid duct?
Emerges from the anterior border of the gland onto masseter, turns inwards after the anterior edge of masseter and pierces buccinator, entering the oral cavity near the 2nd upper molar.
What is the course of the facial nerve?
- Goes through internal auditory meatus (in the temporal bone)
- Exits at stylomastoid foramen
- Gives off posterior auricular branches supplying occipitalis, posterior belly of digastric and stylohyoid
- Enters posteromedial surface of the parotid
- Forms a plexiform arrangement within pes anserinus
What are the 5 terminal branches of the facial nerve?
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
How is the retromandibular vein formed?
By the superficial temporal veins and the maxillary veins within the parotid.
Which terminal branches of the external carotid artery sit inside the parotid?
Maxillary artery and superficial temporal artery
Which clinically important artery is a branch off the maxillary artery?
Middle meningeal artery
Which artery is the main supplier to the scalp?
Superficial temporal artery
What will injury to the facial nerve result in?
Partial/complete paralysis on the side of the injury, identifiable as droop in the face and flattening of the nasolateral folds as well as a loss of movement around the muscles of the orbit.
What is the most common cause of injury to the facial nerve resulting in droop in the face, flattening of the nasolateral folds and loss of movement of muscles around the orbit?
Bell’s Palsy
