E1 - pituitary

Question 1

where are what endocrine glands?

Answer 1

7 main ones:

• in cranial cavity = hypothalamus & pituitary
• in neck = thyroid & parathyroid
• in abdomen = pancreas and 2x adrenal glands
• in pelvis either 2x ovaries or 2x testes depending on gender

Question 2

what are sulci and gyri?

Answer 2

sulci = grooves (dips) in brain
gyri = ridges (higher bumps)

Question 3

what are the 4 lobes that make up cerebrum?

Answer 3

frontal, temporal, parietal, occipital = on each hemisphere

Question 4

what is diencephalon?

Answer 4

central core of cerebrum, it has connections to right & left hemispheres and midbrain (of brainstem)

= it’s made up of thalamus & hypothalamus

Question 5

what are 3 parts of brain stem?

Answer 5

1. midbrain
2. pons
3. medulla (continues as spinal cord)

Question 6

what is pituitary gland structure?

Answer 6

it’s functionally & anatomically divided into anterior (bigger) & posterior (smaller) lobes and then connected to hypothalamus by infundibulum or pituitary stalk

anterior = bigger, pars distalis is main bulge bit and pars tuberalis (stalk bit)

posterior = smaller, made of pars nervosa

Question 7

what is location of pituitary?

Answer 7

pituitary fossa of sella turcica of sphenoid bone
*pituitary fossa also called hypophyseal fossa

Question 8

what are important structures near pituitary gland?

Answer 8

• internal carotid artery
• cavernous sinus (venous system)
• sphenoid sinus
• CN II, III, IV, V1&2, VI

Question 9

explain using basics of visual pathway about early presentation of pituitary expansion?

Answer 9

if expansion of the pituitary gland (e.g. pan coast tumour (apical tumour of lung). it will impinge optic chiasm and info from nasal retina interrupted so this means early clinical sign is inability to see anything from temporal view in both eyes = called bilateral hemianopia

*in optic chiasm nasal retina fibres cross sides. nasal retina fibres carry info from temporal field of view

Question 10

what are the 2 surgical approaches to removing pituitary gland?

Answer 10

1. transcranial (subfrontal) = in through frontal lobe and pass inferior to frontal lobe of brain
2. transsphenoidal = access via nasal cavity and sphenoid sinus →most common

Question 11

what is osteology of nasal cavity?

Answer 11

inferiorly = maxilla
superiorly = nasal bones
roof = cribriform plate of ethmoid bone

nasal septum = formed inferiorly by vomer and superiorly by perpendicular plate of ethmoid bone

there are also superior, middle and inferior nasal conchae (bony ridges) - superior & middle made from ethmoid bone and inferior is justa bone on it’s own

Question 12

what is structure of cribriform plate of ethmoid bone?

Answer 12

= forms roof of nasal cavity

• it has foramina for olfactory nerve nerve axons to pass through (sense of smell)
• also has bone scrolls making superior & middle conchae

Question 13

what are the 4 pairs of paranasal sinuses? their purpose?

Answer 13

1. frontal sinuses
2. maxillary sinuses
3. ethmoidal air cells
4. sphenoid sinuses

= they’re lined with mucosal cells so secrete mucous into nasal cavities via ostia (mouthlike opening) and also thought to reduce weight of skull & add resonance to voice

Question 14

describe briefly the transsphenoidal transnasal approach to pituitary gland removal?

Answer 14

access through nasal cavity, along nasal septum along to posterior aspect then fracture through posterior aspect of septum to access sphenoid bone (through it’s floor) then fracture through posterior wall (roof) of sphenoid sinus to gain access to pituitary

Question 15

what additional fracture can be done to get better access for pituitary gland removal?

Answer 15

Le fort fracture (3 types) = fracture of midface in areas of structural weakness to partially or completely separate from skull

• Le fort 1 = hard plate from maxilla for increased access

Question 16

what is dura mater?

Answer 16

= tough, thick fibrous membrane layer that’s actually part of meninges (3 layer in spinal cord)

Question 17

where is dura mater?

Answer 17

lines each cranial fossa and split into 2 layers:
1. inner meningeal layer (cover brain & spinal cord)
2. periosteal layer (outer layer that adheres to internal surface of skull)

Question 18

what part of dura mater covers pituitary gland?

Answer 18

diaphragm sellae (like tent barrier over top of it so can only see stalk piercing through)

Question 19

what key anatomical structures can be damaged because of pituitary removal?

Answer 19

1. optic nerve = key early clinical sign
2. usually CN III first, VI, IV

Question 20

what are the dural venous sinuses?

Answer 20

= they are areas where the 2 layers of dura (which are generally tightly fused) separate and they drain venous blood from cranial cavity into jugular veins at jugular foramen in floor of posterior cranial fossa

*they act like veins but not actually veins!

• there are cavernous sinuses at each side and they’re connected anteriorly at anterior intercavernous sinus (pituitary gland is surrounded by them)

Question 21

what nerves pass through dural venous sinus?

Answer 21

CN VI passes through sinus itself whilst oculomotor(III) & trochlear (IV) actually pass in walls of sinus

• internal carotid artery passes through sinus itself (amongst veins for heat exchange)