Anatomy of the Pituitary Gland

Question 1

what are the major endocrine glands in each part of the body?

Answer 1

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

Question 2

what is the diencephalon?

Answer 2

thalamus + hypothalamus

forms the central core of the cerebrum with connections to the right and left cerebral hemispheres and midbrain

Question 3

what are the components of the brainstem?

Answer 3

midbrain
pons
medulla oblongata
spinal cord

Question 4

how are the hypothalamus and pituitary related?

Answer 4

hypothalamus sits above the pituitary

hypothalamus is connected to pituitary via the pituitary stalk/infundibulum

Question 5

what are the parts of the pituitary?

Answer 5

anatomically and functionally divided into the anterior and posterior pituitary

Question 6

how does the pituitary develop?

Answer 6

folding of stomodeal roof forms rathkes pouch

folding of diencephalic tissue forms infundibulum

Question 7

what are the 2 functional parts of the pituitary?

Answer 7

rathkes pouch forms anterior pituitary - glandular function as formed from ectoderm
infundibulum formed from neuroderm so neural tissue

Question 8

what are the parts of the anterior lobe of the pituitary?

Answer 8

pars distalis
pars tuberalis
pars intermedia

Question 9

what is the anterior lobe also known as and what does it do?

Answer 9

adenophysis
synthesis and release of most pituitary hormones
- GH
- THS
- ACTH
- FSH
- LH
- PRL

Question 10

what is the posterior lobe also known as and what does it do?

Answer 10

neurophysis
extension of the brain
releases ADH and OT (synthesised in the hypothalamus)

Question 11

what are the parts of the posterior lobe?

Answer 11

pars nervosa

pars intermedia

Question 12

where is the pituitary gland located?

Answer 12

midline structure in the pituitary fossa of the sphenoid bone
immediately inferior to the optic chiasm

Question 13

where is the pituitary fossa located?

Answer 13

within the sella turcica

Question 14

which nerves lie around the pituitary gland?

Answer 14

cranial nerve3, 4, 5i, 5ii and 6

Question 15

what is the optic chiasm?

Answer 15

formed from the right and left optic nerve as they cross over (CN 2s)

Question 16

what is the visual pathway?

Answer 16

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

Question 17

what is the significance of the optic nerves crossing over?

Answer 17

signals from the right nasal nasal retina are processed in the left side of the brain and vice versa

Question 18

how can a pituitary tumour affect vision?

Answer 18

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

Question 19

what is bitemporal hemianopia?

Answer 19

bilateral loss of temporal vision

Question 20

what are the 2 possible surgical approaches to access the pituitary fossa?

Answer 20

transcranial = subfrontal - under the frontal lobe
transsphenoidal = via nasal cavities and sphenoid sinus

Question 21

where does the pituitary sit in relation to the sphenoid sinus?

Answer 21

above

Question 22

which bone forms most of the nasal cavity?

Answer 22

ethmoid

- perpendicular plate forms nasal septum

Question 23

what are the concha and what bone forms them?

Answer 23

superior, middle and inferior
cause turbulent air flow and heat and moisten air
formed from ethmoid bone

Question 24

what are paranasal sinuses?

Answer 24

air filled spaces within the bones surrounding the nasal cavities

Question 25

what are the paranasal sinuses and what bones form them?

Answer 25

``` frontal sinuses (frontal bone) maxillary sinus (maxilla) ethmoidal air cells (ethmoid bone) sphenoid sinuses (sphenoid bone) ```

Question 26

what is the function of paranasal sinuses?

Answer 26

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

Question 27

where is each sinus located?

Answer 27

``` 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 ```

Question 28

what is required for transspehnoidal transnasal approach of surgery?

Answer 28

surgical fracture of the nasal septum and the floor (septum) and roof of the sphenoid sinuses

Question 29

what surgical approach can be used for access to the nasal cavities in complicated cases?

Answer 29

le fort 1 down fracture

Question 30

what are the most important cranial nerves in relation to the pituitary and structures at risk?

Answer 30

CN 1-6

Question 31

what vessels are present within the brain?

Answer 31

internal carotids | vertebral arteries which join to form basillar artery

Question 32

what vessels form the circle of willis in the brain?

Answer 32

left and right internal carotids left and right anterior cerebral arteries left and right posterior cerebral arteries anterior communicating artery posterior communicating artery

Question 33

what is the dura mater?

Answer 33

tough sheet of membrane covering the brain | adherent to the internal aspects of all the bones of the cranial vault

Question 34

what is the diaphragm sellae?

Answer 34

tough sheet of dura mater forming a roof (diaphragm) over the pituitary fossa

Question 35

what is the tentorium cerebelli?

Answer 35

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

Question 36

what nerves pass through the cranial fossa?

Answer 36

CN 2-6

Question 37

what are dural venous sinuses and what do they do?

Answer 37

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

Question 38

what are the dural venous sinuses and what happens at each?

Answer 38

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)

Question 39

where is the pituitary in relation to the diaphragm sellae?

Answer 39

inferior

Question 40

path of internal carotid artery in brain?

Answer 40

enters carotid canal in the temporal bone | turbulent path up through cavernous sinus and around pituitary