Anatomy of the pituitary gland Flashcards
In what region of the brain are the thalamus and hypothalamus found?
Diencephalon
What is the diencephalon?
This forms the core of the cerebrum with connections to both the right and left cerebral hemispheres and midbrain
What connects the pituitary gland to the hypothalamus?
Infundibulum (Pituitary stalk)
Describe the location of the pituitary gland on the cranial vault floor
It is found in the sella turcica, within the pituitary fossa of the sphenoid bone
What are the 2 main lobes of the pituitary gland?
Anterior pituitary
Posterior pituitary
What is the other name given to the anterior pituitary lobe?
Adenohypophysis
What is the other name given to the posterior pituitary lobe?
Neurohypophysis
What are the 3 regions of the anterior pituitary?
- Pars distalis
- Pars tuberalis
- Pars intermedia
What is the function of the anterior pituitary gland?
This is responsible for synthesis and release of most pituitary hormones, including growth hormone, TSH, ACTH, FSH, LH and PRL
What is the main region of the posterior pituitary lobe?
Pars nervosa
What is the function of the posterior pituitary lobe?
This is an extension of the brain and releases ADH and oxytocin, which are synthesised in the hypothalamus
What are the 2 regions of the retina?
Temporal retina
Nasal retina
What are the 2 regions of the visual field?
Left and right
Where will light from the left visual field hit?
Left nasal retina
Right temporal retina
Where will light from the right visual field hit?
Right nasal retina
Left temporal retina
What is the name of cross over between the optic nerves?
Optic chiasm
Where will signals from the left nasal and right temporal retina travel?
To the right side of the brain
Where will signals from the right nasal and left temporal retina travel?
To the left side of the brain
Describe the route of the nerves from the eye to the brain
2 x Optic nerves =>
1 x Optic chiasm =>
2 x Optic tracts =>
4 x Geniculocalcarine tracts (Optic radiations)
Visual cortex of the occipital lobe
How can pituitary gland tumours affect the visual pathway?
They can cause bitemoral hemianopia, in which only one half of the visual field can be seen
Where on the optic pathway do pituitary gland tumours affect in bitemporal hemianopia?
In the case of bitemporal hemianopia, the lesion will occur not in the optic nerve, as light is still being seen, but in the optic chiasm, where the crossing over of the visual field is seen
What are the two forms of access to the pituitary gland for surgery?
- Trans-cranial access
- Trans-sphenoidal access
How is trans-cranial access to the pituitary gland gained?
Trans-cranial access is gained sub-frontally, in which access is made just under the frontal lobe of the brain, above the orbital fossa
How is trans-cranial access to the pituitary gland gained?
Trans-sphenoidal access is gained up through the nose and through the sphenoidal sinus
What are some structures at risk during pituitary gland surgery?
Optic chiasm
Occulomotor nerve
Trochlear nerve
Trigeminal nerve
Abducens nerve
Cavernous sinus
Internal carotid artery
Dura mater
What will occur if the optic chiasma is damaged during pituitary gland surgery?
Bitemporal hemianopia
What will occur if the oculomotor nerve is damaged during pituitary gland surgery?
Several eye movement deficits
Dilated pupils
What will occur if the Trochlear nerve is damaged during pituitary gland surgery?
Difficulty looking inferiorly and laterally
What will occur if the trigeminal nerve is damaged during pituitary gland surgery?
Parasthesia of the face
Difficulty masticating
What will occur if the abducens nerve is damaged during pituitary gland surgery?
Difficulty abducting the eye
What will occur if the cavernous sinus is damaged during pituitary gland surgery?
Venous haemorrhage
What will occur if the internal carotid artery is damaged during pituitary gland surgery?
Catastrophic haemorrhage
What will occur if the dura mater is damaged during pituitary gland surgery?
Cerebrospinal fluid leak
What are the paranasal sinuses?
air-filled spaces within the bones surrounding nasal cavities
What are some examples of paranasal sinuses?
- Frontal sinuses - Frontal bone
- Maxillary sinuses - Maxillae
- Ethmoidal air cells - Sphenoid bone
- Sphenoid sinuses - Sphenoid bone
What surrounds the inside of the paranasal sinuses?
Mucus-secreting respiratory mucosa
What are some functions of the paranasal sinuses?
- Secretion of mucus, which drains into nasal cavities through the ostia (Bony drainage holes)
- Reduce weight of skull
- Add resonance to voice
What structure lines the entire floor of the cranial vault?
Dura mater
What is the tentorium cerebelli?
The tentorium cerebelli is a tough sheet of dura mater tenting over the cerebellum in the posterior cranial fossa, but which a centra gap to permit the brainstem to pass through
What is the diaphragma sellae?
The diaphragma sellae is a tough sheet of dura mater forming a roof (Diaphragm) over the pituitary fossa
What are the dural venous sinuses?
These are venous channels within the dura mater that 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 dural venous sinuses surround the pituitary gland?
Left and right cavernous sinuses
Anterior and posterior inter cavernous sinuses
