Anatomy of the Pituitary gland Flashcards
What is located infreriorly and posteriorly to the cerebrum
Cerebellum
The brain stem can be subdivided into what 3 parts?
Midbrain
pons
medulla (oblongata)
what is the diencephalon composed of
The thalamus and hypothalamus
what does the diencephalon form
The central core of the cerebrum with connections to the right and left cerebral hemispheres and the midbrain
What connects the hypothalamus to the pituitary gland
the infundibulum
What does an infundibulum mean? regardless of location in the body
A funnel
what is the pituitary gland divided into
Anterior and posterior pituitary gland
what are the names of the 3 fossae of the skull?
anterior, middle and posterior
What are the bounderies of the anterior fossae of the skull
Frontal bone and the lesser wing of the sphenoid bone
What are the boundaries of the middle fossae of the skull
Lesser wings of the sphenoid and by the peatrus parts fo the temporal bone
What are the boundaries of the posterior fossae of the skull
Peatrus parts of the temporal bone and the occipital bone
Where is the pituitary fossa located
In the middle part of the middle fossa (sphenoid bone)
what does the pituitary fossa lie within
The sella turcica
what structure lies immediately inferior to the pituitary gland
optic chiasm
What forms the optic chiasm
Right and left optic nerves (CNs II)
What passes posteriorly from the chiasm
The optic tracts
Where do the neurones from the optic tract synapse
The thalamus
Neurones pass from the thalamus to where
To the visual cortext in the occipital lobe via the optic radiation
What can the field of view be divided into
The nasal and temporal side of visual field
If the light passes from the nassal side, where will it be perceived
In the temporal retina
Describe the route of neurones and action potentials if light passes from the nasal side
light is received by the temrporal retina,
APs are then sent via neurones from the retina long the optic nerve to then pass along the right optic tract to synapse in the thalamus.
A second neurone will then send signals to the visual cortex in the occipital bone
Describe the route of neurones and action potentials if light passes from the temporal side
Light rays will be received by the nasal retina and action potentials are sent along to the optic chiasma but will then cross over ehere to pass down the controlateral side in the optic tract to synapse in the thalamus. A second neurone will then send signals to the visual cortex in the occipital bone
What happens if there is a pituitary gland tumour
The gland enlarges resulting in compression of the optic chiasma meaning there will be a disruption of visual pathway and the loss of temporal vision
Why is there a loss of temporal vision with a pituitary tumour
The tumour disrupts the transmission of action potentials from the nasal retina bilaterally
Define bitemporal hemianopia
The loss of temporal field vision in both eyes
What are the two types of surgical approach to accessing the pituitary gland
Transcranial approach (sub frontal - under the frontal lobe) Transsphenoidal approach (via nasal cavities and sphenoid sinus)
What forms the roof of the nasal cavity
The cribriform plate of the ethmoid bone
What forms the inferior part of the nasal septum
The vomer bone
What forms the superior part of the nasal septum
The perpendicular plate of the ethmoid bone
The superior and middle nasal concha are part of what?
Ethmoid bone
What are paranasal sinuses
Air-filled spaces within the bones surrounding the nasal cavities
Where are the 4 paranasal sinuses
Frontal bone (frontal sinuses Maxillae (maxillary sinuses) Ethmoid bone (ethmoidal air cells) Sphenoid bone (sphenoid sinuses)
What are the paranasal sinuses lined by
Mucous secreting respiratory muscosa
What are the functions of the paranasal sinuses
To make mucous and drain it into the nasal cavities through ostia _bony drainage holes)
Reduces the weight of the skull
Add resonance to the voice (maxillary sinuses)
Increase buoyancy in aquatic mammals e.g. dolphins
What does the transsphenoidal transnasal approach require
Surgical fracture of the nasal septum and the floor and roof of the sphenoid sinus(es)
What is another name given to the maxillary sinuses
Antra of the maxilla
How many sinuses are located in the ethmoid bone
3 groups - superior, middle and inferior
Where are the sphenoid sinuses located
Within the body of the sphenoid bone
What type of Le fort fracture can be induced by the surgeon and why
Type 1 - if the surgeon requires better access into the nasal cavity
Describe a Type 1 Le Fort fracture
Horizontally along the maxilla
Describe a Type 2 Le Fort Fracture
Dissociation from the entire maxilla from the rest of the face
Describe a Type 3 Le Fort Fracture
Separation of the facial skeleton form the neurocranium
What artery crosses the anterior surface of the pons
The basilar artery
What is the posterior extension of the optic nerve
The optic chiasma
What is the tantrum cerebelli
A tough sheet of dura mater “tenting” over the cerebellum within the posterior cranial fossa but with a central gap to permit the brainstem to pass through
What is the function of the dura mater
A protective lining for the brain
What artery lies very close to the pituitary gland
Internal carotid artery
What is the diaphragm sell
A tough sheet of dura mater forming a roof (diaphragm) over the pituitary fossa
What lies inferior to the diaphragm sella
The pituitary gland
The entire cranial cavity is lines internally with dura mater. True or False
True
What are the dural venous sinuses
Areas within the cranial cavity where the 2 layers of dura have separated responsible for draining venous blood from the cranial cavity into the internal jugular veins
What is the pituitary gland surrounded by
The cavernous and inter cavernous sinuses
What arteries pass through the cavernous sinuses
The internal carotid arteries
What cranial nerves also run through the cavernous sinus
2,3,4,5i, 5ii, 6
The ophthalmic artery is a branch of what artery
The internal carotid artery
Where does the ophthalmic artery enter the orbit
Via the optic canal
Describe the route of the right internal carotid artery
Passes medially into the cavernous sinus and forms a loop to go and supply the brain
What are the 8 structures at risk in pituitary gland surgery
Optic chiasm Oculomotor nerve (1) Trochlear nerve (4) Trigeminal nerve (5) Abducent Nerve (6) Cavernous sinus Internal carotid artery Dura mater
What is the functional deficit of a damaged internal carotid artery
Catastrophic haemmorrhage
What is the functional deficit of a damaged dura mater
CSF leak
What is the functional deficit of a damaged cavernous sinus
Venous haemorrhage
What can cause problems with specific eye movements
Damage to the trochlear nerve, the oculomotor nerve or the abducent nerve
What can cause a dilated pupil
A damaged oculomotornerve
What can cause sensory symptoms on the face or difficulty chewing
Damage to the trigeminal nerve