2.7.2015
Histology of the Endocrine Glands
Dr. Archana Rani
Associate Professor
Department of Anatomy,
KGMU UP, Lucknow
Introduction
• Endocrine tissue is made up
of cells that produce
secretions which are poured
directly into blood.
• Endocrine cells lie in close
apposition
to
blood
capillaries or sinusoids.
• Secretions of endocrine
cells are called hormones.
• Hormones travel through
blood to target cells and
influence their function.
The Endocrine Glands
(Ductless glands)
• Pituitary (hypophysis)
– Anterior pituitary
– Posterior pituitary
• Adrenal gland (suprarenal)
– Adrenal cortex
– Adrenal medulla
• Thyroid gland
– Follicles
– Parafollicular cells
• Parathyroid gland
The Pituitary Gland
(Hypophysis Cerebri)
a
The Pituitary Gland
(Hypophysis Cerebri)
• “Master endocrine gland”.
• Parts:
 Adenohypophysis
(Anterior Pituitary): consist
of pars distalis, pars
intermedia & pars tuberalis.
 Neurohypophysis
(Posterior Pituitary): consist
of pars nervosa, infundibular
stalk & median eminence.
Adenohypophysis
Pars Distalis:
• Cells are arranged as irregular cords in between thin-walled fenestrated
sinusoids.
• Consists of 2 major group of cells: chromophils & chromophobes.
• Chromophils are of 2 types: basophils & acidophils.
Pars Intermedia:
•
•
•
•
Poorly developed in humans.
Consists mainly of basophils.
Presence of colloid filled vesicles.
Some cells produce melanocyte stimulating hormone (MSH).
Pars Tuberalis:
• Consists of chromophilic (mostly basophilic) & chromophobic cells.
Neurohypophysis
Consists of:
• Numerous non-myelinated nerve fibres
• Supporting cells (pituicytes)
• Sinusoids
Produce 2 hormones:
• Oxytocin
• Vasopressin
Herring bodies: collection of secretory granules at the terminal
portion of axonal processing.
Posterior Pituitary
Hypophysis
(Mallory-Azan & orange G. stain)
Cells and hormones of the anterior pituitary
LM
staining
Cell type
Acidophil Somatotrophs
Hormone
Releasing (+) or
inhibiting (-) horm.
Growth hormone (GH)
= somatotropin
GHRH (+)
Somatostatin (-)
Acidophil Mammotrophs Prolactin (PRL)
= lactotrophs
[Dopamine (-)
estrogen (+)]
Basophil
Thyrotrophs
TRH (+)
Basophil
Gonadotrophs Luteinizing hormone
(LH), follicle
stimulating hormone
(FSH); both =
gonadotropin
Basophil
(human)
Corticotrophs
Thyroid stimulating
hormone (TSH)
= thyrotropin
GnRH (+)
Adrenocorticotropin
CRH (+)
(ACTH) = corticotropin
Hypophysis (H&E stain)
Pars distalis (Azan stain)
Pituitary gland
Anterior pituitary (trichrome stain)
Anterior pituitary (H&E stain)
Basophil
Posterior Pituitary
• Hormones
– Antidiuretic hormone (ADH = arginine vasopressin)
– Oxytocin
• Neurosecretion
– Hormones synthesized as part of larger proteins (neurophysins)
in neuron cell bodies of hypothalamus.
– Transported in axons to pars nervosa (hormone cleaved from
neurophysin).
– Hormone secreted from axon terminals into capillaries.
• Pituicytes
– Specialized glia of pars nervosa.
Pars intermedia,
between anterior and
posterior pituitary
Anterior
Posterior
(Poorly developed and of
doubtful function in
humans)
Intermedia
Rathke's pouch
Pars intermedia (rat pituitary)
THYROID GLAND
Microscopic structure
• The gland is surrounded by a thin
fibrous capsule.
• Septa from the capsule extend into
the gland & divide it into lobules.
• Lobules are made up of spherical
masses called follicles.
• Follicle has a cavity filled with
homogenous material called
colloid.
• Follicular cells are normally
cuboidal in shape.
• Secrete 2 hormones: triiodothyronine (T3) & tetraiodothyronine (T4) or thyroxine.
Microscopic structure (contd…..)
Parafollicular cells (C-cells):
• Embedded within a follicle
or lie between follicles.
• Singly or in groups.
• Cells are polyhedral with
oval eccentric nucleus and
cytoplasm contains
secretory granules.
• Light staining cells.
• Secrete hormone
calcitonin.
Parathyroid Gland
• Small ovoid bodies (4 in no.)
embedded in the connective tissue
capsule on the posterior surface of
thyroid gland.
• Consists of 2 types of cells:
 Chief cells (principal cells): more
numerous,
polygonal,
round
centrally located nucleus & mildly
eosinophilic cytoplasm, secrete
parathyroid hormone (PTH).
 Oxyphil cells: larger in shape, deep
acidophilic cytoplasm.
Parathyroid Gland (H&E stain)
Adrenal Gland
(Suprarenal Gland)
Microscopic structure (low power)
• The gland is
covered
by
connective tissue
capsule.
capsule
cortex
• Capsule sends
septa inside the
gland.
• 2 parts:
Cortex
 Medulla
medulla
Microscopic structure (low power)
Zona glomerulosa
Cortex
Zona fasciculata
Zona reticularis
Medulla
Mineralocorticoid
(aldosterone)
Glucocorticoids
(cortisol)
Androgen
(dehydroepiandrosterone)
& Estrogen
Catecholamines
(epinephrine &
norepinephrine)
Adrenal Cortex
3 layers:
• Zona Glomerulosa: cells are
arranged as rounded clusters
separated by thin connective
tissue. Cells are columnar with
dark staining nuclei and
acidophilic cytoplasm.
• Zona Fasciculata: thick zone,
large pale staining polyhedral
cells arranged into parallel
columns 1-2 cell thick.
• Zona Reticularis: small rounded
deep staining cells arranged in
branching & anastomosing cords.
Adrenal Medulla
• Cells are large, epitheloid &
arranged in groups.
• Cells are closely related to
sinusoidal capillaries.
• Cytoplasm
is
light
basophilic with H&E stain.
• Chromaffin
reaction:
Tissue
fixation
with
potassium
bichromate
shows fine brown granules
in the cells of medulla.
Capsule
Cortex
Medulla
References
1. diFiore’s Atlas of Histology with functional
Correlations, 12th Edition.
2. Textbook of Human Histology. Inderbir Singh,
1st Edition.
3. Textbook of Histology. GP Pal, 3rd Edition.
MCQ
Q1. The supportive cells in pars nervosa are
known as:
a. Chromophils
b. Chromophobes
c. Herring bodies
d. Pituicytes
MCQ
Q2. Parafollicular cells is a specific feature of:
a. Pituitary
b. Thyroid
c. Parathyroid
d. Suprarenal
MCQ
Q3. The epithelial lining of thyroid follicles in
resting phase is:
a.
b.
c.
d.
Squamous
Cuboidal
Columnar
Transitional
MCQ
Q4. Increased amount of lipid droplets are found
in cells of which zone of adrenal gland?
a. Zona glomerulosa
b. Zona fasciculata
c. Zona reticularis
d. All of the above
MCQ
Q5. Chromaffin reaction is depicted by which
endocrine gland?
a. Pituitary
b. Thyroid
c. Parathyroid
d. Suprarenal