Download The Endocrine System

 Pituitary Gland
 The hypophysis (Gr. hypo, under, + physis, growth),
or pituitary gland
 Weighs about 0.5 g
 It lies in a cavity of the sphenoid bone—the sella
turcica—an important radiological landmark
 During embryogenesis, the hypophysis develops
partly from oral ectoderm and partly from nerve
tissue
 Because of its dual origin, the hypophysis actually consists of two
glands:
 Neurohypophysis
 Adenohypophysis
 They are united anatomically but have different functions.
 Neurohypohysis (Posterior Pituitary)neural part.
Consists of:
 Pars nervosa
 Infundibulum(stalk and median eminence)
 Adenohypophysis(Anterior Pituitary)glandular part:
 It arises from oral ectoderm.
 It is subdivided into three portions:
 Pars Distalis
 Pars Tuberalis
 Pars Intermedia.
Adenohypophysis
 Pars Distalis(anterior lobe) :
 The largest part of
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adenohypophysis
The main components of the
pars distalis are cords of
epithelial cells .
Highly vascular stroma.
The hormones produced by
these cells are stored as
secretory granules.
Fibroblasts produce
reticular fibers that support
the cords of hormonesecreting cells.
 The pars distalis accounts for 75% of the mass of the
hypophysis.
 Common stains allow the recognition of three cell types
in the pars distalis:
 Chromophobes(Gr. chroma, color, + phobos, fear)
 Chromophils (Gr. chroma + philein, to love)
 Two types of chromophils:
 Basophils according to their affinity for basic dyes
 Acidophils according to their affinity for acid dyes
 The subtypes of basophil and acidophil cells are named
for the hormones they produce.
 With the exception of the gonadotropic cell, which
produces two hormones, the other cells produce only a
single hormone.
 Chromophobes(degranulated secretory cells) do not
stain intensely and, when observed with an electron
microscope, show two populations of cells.
Secretory Cells of the Pars Distalis
Cell Type
Stain Affinity
Hormone Produced
Somatotropic cell
Acidophilic
Mammotropic cell
Acidophilic
Prolactin (PRL)
Gonadotropic cell
Basophilic
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Thyrotropic cell
Basophilic
Thyrotropin (TSH)
Corticotropic cell
Basophilic
Corticotropin (ACTH
α-Melanocyte-stimulating hormone?
(α-MSH))
Melanotropes?
Basophilic
α-Melanocyte-stimulating hormone?
(α-MSH)
Growth hormone (GH, somatotropin)
 Pars Tuberalis
 The pars tuberalis is a
funnel-shaped region
surrounding the
infundibulum of the
neurohypophysis .
 Most of the cells secrete
gonadotropins (folliclestimulating hormone
and luteinizing
hormone)
 Are arranged in cords
alongside the blood
vessels.
Pars Intermedia
 Is a rudimentary region in humans
 Made up of cords and follicles of weakly
basophilic cells that contain small secretory
granules.
 It produces Melanocyte-stimulating hormone
(α-MSH).
Neurohypophysis (Posterior pituitary)
It consists of
 Pars nervosa
 Infundibulum (neural stalk ) stem and median
eminence.that connects it to the
hypothalamus.
 The pars nervosa
 Does not contain
secretory cells.
 Contains
nonmyelinated axons
and nerve endings of
neurosecretory
neuron
 The nerve endings
have terminal
dilations called
Herring bodies
Pars Nervosa
 Neurosecretory neurons have cell bodies that lie in the supraoptic &
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paraventricular nuclei in the hypothalamus
The secretory neurons have all the characteristics of typical neurons
The secretory neurons have well-developed Nissl bodies related to the
production of the neurosecretory material
Cells present in Pars Nervosa are:
Pituicytes (glial cell)
fibroblasts
mast cells.
Adrenal Glands
 This gland is found above the kidney.
 The dense connective tissue capsule covers the adrenal gland
& sends thin septae into the gland.
 Septae support the blood vessels and nerves
 The stroma consists mainly of a rich network of reticular
fibers that supports the secretory cells.
 The parenchyma consists of cortex and medulla.
The cortex is subdivided
into 3 concentric zones,
according to the
arrangement of the cells
these zones are called:
i.ZonaGlomerulosa.
ii. Zona Fasiculata.
The cells in this zone are
called spongiocyes.
iii. Zona Reticularis.