What is pituitary gland?
Also known as hypophysis cerebri, pituitary
is an ovoid neuroglandular organ.
It is suspended from the floor of the third
ventricle by a stalk known as infundibulum.
It is located in a depression called hypophyseal fossa
of sella turcica of body of sphenoid. The fossa is roofed by the diaphragm
sellae which is a fold derived from the meningeal layer of dura mater. The
diaphragm sellae is pierced by the pituitary stalk or infuldibulum.
What are the presenting parts?
The gland consists of:
An anterior lobe or adeno-hypophysis
and
A posterior lobe or neurohypophysis
Gross anatomy of Anterior Lobe or
adeno-hypophysis:
It is highly cellular and occasionally presents intra-glandular
cleft. The part behind the cleft is known as pars intermedia, which
is rudimentary in human beings and embraces the front and sides of the
posterior lobe. The part of the anterior lobe extending upward along the
infudibular stem is known as pars tuberallis. The rest of the gland in
front of the cleft is called pars anterior or pars distalis.
Gross Anatomy of posterior lobe or
neurohypophysis:
It is continuous above with the infundibulum. It
consists of three parts:
Median eminence
of tuber cinerium, infundibular stem and pars nervosa
Relations:
Anteriorly:
anterior intercavernous sinus
Posteriorly:
posterior intercavernous sinus, dorsum sellae, the basilar artery, and the pons
Superiorly:
optic chiasma, anterior communicating artery and the floor of third ventricle
separated by the diaphragma sellae, which has a central aperture that allows
the passage of the infundibulum
Inferiorly:
The body of the sphenoid, with its sphenoid air sinuses
On each side:
The cavernous sinus and its contents
Arterial Supply:
Anterior lobe:
by superior hypophyseal artery (branch of internal
carotid artery)
Breaks up and form capillary plexus in the median
eminence and infundibular stem
Long and short portal vessels arise from these
plexus and supply the anterior lobe
Posterior lobe:
by inferior hypophyseal artery (branch of internal
carotid artery)
Enters the posterior lobe and form capillary plexus
to supply it.
Venous Drainage:
Small veins arise from the surface of the gland and
drain into neighboring dural sinuses
What is the structure or histological
features of Pituitary gland?
Pars anterior:
consists of
– chromophil
cells and chromophobe cells
Chromophil cells are classified into
– Acidophil
cells (secrete somatotrophs, mammotrophs)
– basophil
cells (secrete corticotrophs, thyrotrophs, gonadotrophs)
Chromophobe cells: they contain very few granules in
the cytoplasm
Pars tuberalis:
consists of mainly undifferentiated cells and some acidophil and basophil cells
Pars intermedia:
it is poorly developed in human.
Pars posterior:
– unmyelinated
nerve fibres with supporting cells called pituicytes
– stores
and releases vasopressin (anti-diuretic hormone; ADH) and oxytocin
REFERENCES:
Following resources are used while preparing this post (readers are strongly recommended to go through them for more details):
Gray's Anatomy
K. L. Moore's Clinically Oriented Anatomy
R. Snell's Clinical Anatomy
Wheater's Functional Histology: A Text and Color Atlas
Junqueira's Basic Histology: Text and Atlas