Answer
The pituitary gland comprises two structures, the neurohypophysis and the adenohypohysis ( posterior pituitary and anterior pituitary). These two organs/structure are different in several ways in their embryologic derivation, as well as in their structure and functions.
The pituitary is suspended from the floor of the hypothalamus by a stalk of tissue called the infundibulum. and sits in the sella turcica , a depression in the sphenoid bone; it is normally about the size of a small bean/pea. However it grows significantly larger in females during pregnancy
Work Step by Step
Differences between the posterior pituitary and anterior pituitary
Embryological differences:
1a. The neurohypophysis (posterior pituitary) arises as a
down-growth of the developing brain, the neurohypophyseal
bud of the diencephalon.
1b. The adenohypophysis is mainly glandular tissue of
ectodermal origin; it is an outgrowth of a pharyngeal
pouch (Rathke).
Structural differences:
2.a The anterior pituitary is the larger anterior part of the
pituitary gland (70-80%). It consists of two parts (in adults),
the anterior lobe or pars distalis, and the pars tuberalis
which wraps around the pituitary stalk.
2b. The neurohypophysis can also be divided int two parts ,
the infundibulum, and the pars nervosa --the posterior
lobe. The secretory cells of the neuohypophysis are
modified neurons.
Functions:
3a. The adenohypophysis secretes seven trophic hormones--
ACTH, TSH, LH, FSH, prolactin(PRL), growth hormone
(GH/STH), and MSH.
3b. The hormones of the posterior pituitary are oxytocin and
ADH (vasopressin). They are secreted in the neurons of the
paraventricular nucleus (oxytocin), and the supraoptic nucleus
(ADH) of the hypothalamus. The hormones travel down
axons to the posterior hypophysis where they are stored in
vesicles and released on by nervous stimuli
(triggers) as needed.
