L1 Anatomy of the Pituitary Gland Flashcards
(35 cards)
Where you find the pituitary gland ?
Sitting on sella turcica ( Hypophyseal fossa)
Anterior .. tubercle sellea
Posterior .. dorsum sellea
What are the measurements of pituitary glands ?
12 mm in transverse
8 mm in antero-posterior diameter
Weight:
- adults is 500 mg
- newborn is 100 mg
- during pregnancy 1000 mg
What are the main parts of pituitary gland ?
- Adenohypophysis ( anterior )
2. Neurohypophysis ( posterior )
What are the main parts of adenoH ?
- Pars anterior (pars distalis) – in front of the cleft
- Pars intermedia – behind the cleft
- Pars tuberalis – in front of the infundibular stem
What are the parts of Neurohypophysis ?
- Pars nervosa – behind the pars intermedia and above it continues with infundibular stem
- Infundibular stem-the portion of the pituitary stalk behind the pars tuberalis is called infundibular stem
- Median eminence –it is the upper portion of the infundibular stem at the floor of the III ventricle
What is the membrane that separates pituitary from hypothalamus ?
Diaphragma sella
What structures you have above and below and lateral to the pituitary?
ABOVE :
- Optic chaism
- Anterior communicating artery
BELOW :
1. Sphenoidal air sinuses ( separated- by thin bony plate )
LATERAL :
- Cavernous sinus
- Internal carotid artery
- abducent nerve ( 6th )
- structures present in the lateral wall of the cavernous sinus :
- (oculomotor III , trochlear IV, ophthalmic & maxillary nerves V)
Why A tumor of the pituitary is generally detected easily ?
as it begins to grow and interfere with hormonal activity.
What will happen if pituitary tumor grows superiorly , laterally, and inferiorly ?
- Superiorly :
- it may compress optic chiasma to cause bitemporal hemianopia (temporal field of vision is lost in both eyes). - Laterally :
- it will grow towards cavernous sinus,(rarely into the orbit) cause exophthalmos (protrusion of the eye) & paralysis of extra ocular muscles - Inferiorly :
- it may break sella turcica, cause enlargement of the hypophyseal fossa. It can involve sphenoidal air sinus leads to nasal discharge .. then it can extend to nasopharynx and nasal cavity
Why tumor which compress the central part of the chiasma lead to bi-temporal hemianopia ?
This because the central portion of the optic chiasma has crossing fibres from temporal field of vision.
What are the arterial supply to the pituitary?
It is mainly supplied by the superior and inferior hypophyseal arteries, which are the branches of the internal carotid artery:
- Superior hypophyseal artery:
- terminates by forming capillary plexus in the median eminence and lower part of the infundibulum. - Inferior hypophyseal artery:
- gives few direct branches to the posterior lobe and some of them terminate in the capillary plexus in the lower part of the infundibulum.
What are the long and short portal vessels ?
long portal vessels :
- Those vessels arising from the capillary plexus in the median eminence draining into the adenohypophysis
Short portal vessels :
- Those vessels arising from the capillary plexus in the lower infundibulum to adenohypophysis
How can hypothalamus control the activities of adenohypophysis ?
- The two plexus are in contact with the nerve terminals from the hypothalamus
- The neuronal secretion will affect the blood flow of the long and short portal
- The blood flow normally carries the stimulating and inhibiting factors
So hypothalamus control the adenohypophysis
What is the venous drainage of pituitary gland ?
drains into cavernous sinus.
Adeno by hypophyseal veins
Neuro directly
Why does The posterior lobe not synthesizing the hormones, but acts as storage and releasing centre ?
- Posterior lobe is connected with hypothalamus through the hypothalamo hypophyseal tract, arising from the supraoptic ( produce vasopressin ) and paraventricular ( produce oxytocin ) nuclei of hypothalamus.
- Axons arising from these nuclei of the hypothalamus ends in the neurohypophysis with a large granule-filled dilation called Herring bodies that will release the hormones to be stored tell their release
What is the origin of both lobes of pituitary?
Adenohypophysis :
- an ectodermal diverticulum from the roof of the primitive mouth called Rathke’s pouch ( from oral ectoderm )
Neurohypophysis :
- downward growth from the diencephalon ( from neural ectoderm )
What is craniopharyngiomas ?
They are tumors produced by Remnant’s of Rathke’s pouch ( primitive mouth ) that may be present in the roof of the nasopharynx
What is the histology of adeno/neurohypophysis ?
- The adenohypophysis is highly cellular
2. The neurohypophysis consists of nerve fibres with few supporting cells.
What are the cellular structure of adenohypophysis?
- Chromophobes 50%
- Chromophils 50%
* 40% is acidophilic by eosin ( somato/ mammo )
* 10% is basophilic by hematoxylin ( cortico / gonado / thyro )
What are the hormones that will be secreted from each type of adenohypophysis cells ?
Acidophils:
1. Somatotrophs (growth hormone/somatotropin)
2. Mammotrophs (prolactin)
Mnemonic to remember – GPA (Growth hormone Prolactin Acidophils)
Basophils: 1. Follicle stimulating hormone (FSH) 2. Luteinizing hormone (LH/ICSH) 3. Corticotrophs (Adrenocorticotropin) 4. Thyrotrophs (TSH) Mnemonic to remember – FLAT Base
What is the structure of Intermediate Lobe (pars intermedia) ?
Small irregular colloid containing cavities lined by cuboidal epithelium that are remnants of Rathke’s pouch. It has Melanotrophs.
What are melanotrophs ?
They are cells found in pars intermedia that secrete melanocyte stimulating hormones (MSH ) that increases the pigmentation of the skin
What are the components of Posterior Lobe (pars nervosa) ?
- Non myelinated nerve fibers
- special types of neuroglial cells called pituicytes
- fenestrated capillaries
- dilations of the Axons of hypothalamohypophyseal tract contain neurosecretary granules (called Herring bodies )
What is Vasopressin/ Antidiuretic hormone (ADH) ?
From supra optic nucleus of hypothalamus.
It increases the water reabsorption in the distal convoluted tubules of the kidney, and produces concentrated urine
