Anatomy of the Pituitary Gland Flashcards
what are the major endocrine glands in each part of the body?
cranial cavity = hypothalamus and pituitary
neck = 4 parathyroid and thyroid gland
abdomen (retroperitoneum) = 2 adrenal glands and pancreas
pelvis (female) = 2 ovaries
perineum (male) = 2 testes
what is the diencephalon?
thalamus + hypothalamus
forms the central core of the cerebrum with connections to the right and left cerebral hemispheres and midbrain
what are the components of the brainstem?
midbrain
pons
medulla oblongata
spinal cord
how are the hypothalamus and pituitary related?
hypothalamus sits above the pituitary
hypothalamus is connected to pituitary via the pituitary stalk/infundibulum
what are the parts of the pituitary?
anatomically and functionally divided into the anterior and posterior pituitary
how does the pituitary develop?
folding of stomodeal roof forms rathkes pouch
folding of diencephalic tissue forms infundibulum
what are the 2 functional parts of the pituitary?
rathkes pouch forms anterior pituitary - glandular function as formed from ectoderm
infundibulum formed from neuroderm so neural tissue
what are the parts of the anterior lobe of the pituitary?
pars distalis
pars tuberalis
pars intermedia
what is the anterior lobe also known as and what does it do?
adenophysis synthesis and release of most pituitary hormones - GH - THS - ACTH - FSH - LH - PRL
what is the posterior lobe also known as and what does it do?
neurophysis
extension of the brain
releases ADH and OT (synthesised in the hypothalamus)
what are the parts of the posterior lobe?
pars nervosa
pars intermedia
where is the pituitary gland located?
midline structure in the pituitary fossa of the sphenoid bone
immediately inferior to the optic chiasm
where is the pituitary fossa located?
within the sella turcica
which nerves lie around the pituitary gland?
cranial nerve3, 4, 5i, 5ii and 6
what is the optic chiasm?
formed from the right and left optic nerve as they cross over (CN 2s)
what is the visual pathway?
optic nerves from nasal retinas cross over in the nasal chiasm
the right and left optic nerves pass posteriorly from the chiasm and synapse in the thalamus
the next axons in the chain pass via the optic radiation to the visual cortex in the occipital lobe
what is the significance of the optic nerves crossing over?
signals from the right nasal nasal retina are processed in the left side of the brain and vice versa
how can a pituitary tumour affect vision?
can compress the optic chiasm which disrupts the transmission of action potentials from the nasal retina bilaterally meaning the patient loses vision in the temporal field bilaterally
what is bitemporal hemianopia?
bilateral loss of temporal vision
what are the 2 possible surgical approaches to access the pituitary fossa?
transcranial = subfrontal - under the frontal lobe transsphenoidal = via nasal cavities and sphenoid sinus
where does the pituitary sit in relation to the sphenoid sinus?
above
which bone forms most of the nasal cavity?
ethmoid
- perpendicular plate forms nasal septum
what are the concha and what bone forms them?
superior, middle and inferior
cause turbulent air flow and heat and moisten air
formed from ethmoid bone
what are paranasal sinuses?
air filled spaces within the bones surrounding the nasal cavities
what are the paranasal sinuses and what bones form them?
frontal sinuses (frontal bone) maxillary sinus (maxilla) ethmoidal air cells (ethmoid bone) sphenoid sinuses (sphenoid bone)
what is the function of paranasal sinuses?
lined by mucous secreting respiratory mucosa
make mucous and drain it into the nasal cavities through ostia
reduce weight of skull
add resonance to the voice
where is each sinus located?
ethmoid = 3 groups between nasal cavity and orbit maxillary = 1 within each maxilla sphenoid = within body of sphenoid bone frontal = often connect in the midline
what is required for transspehnoidal transnasal approach of surgery?
surgical fracture of the nasal septum and the floor (septum) and roof of the sphenoid sinuses
what surgical approach can be used for access to the nasal cavities in complicated cases?
le fort 1 down fracture
what are the most important cranial nerves in relation to the pituitary and structures at risk?
CN 1-6
what vessels are present within the brain?
internal carotids
vertebral arteries which join to form basillar artery
what vessels form the circle of willis in the brain?
left and right internal carotids
left and right anterior cerebral arteries
left and right posterior cerebral arteries
anterior communicating artery
posterior communicating artery
what is the dura mater?
tough sheet of membrane covering the brain
adherent to the internal aspects of all the bones of the cranial vault
what is the diaphragm sellae?
tough sheet of dura mater forming a roof (diaphragm) over the pituitary fossa
what is the tentorium cerebelli?
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 nerves pass through the cranial fossa?
CN 2-6
what are dural venous sinuses and what do they do?
folding of the dura mater forming venous channels which drain most of the venous blood from the cranial cavity (including the brain) into the internal jugular veins at the jugular foraminae in the floor of the posterior cranial fossa
what are the dural venous sinuses and what happens at each?
anterior intercavernous sinus (connects right and left cavernous sinuses anterior to pituitary)
left and right cavernous sinuses (internal carotids pass through, either side of the pituitary)
where is the pituitary in relation to the diaphragm sellae?
inferior
path of internal carotid artery in brain?
enters carotid canal in the temporal bone
turbulent path up through cavernous sinus and around pituitary
