Transcript THYROID & PARATHYROID GLAND

ENDOCRINE GLANDS
Dr Iram Tassaduq
ENDOCRINE GLANDS
An “endocrine gland” is
one whose product passes
by way of the blood vascular
system to other cells in the
body, where it elicits a
specific response.
COMPONENTS OF THE
ENDOCRINE SYSTEM
Discrete endocrine glands
The endocrine components of the
glands with both exocrine & endocrine
functions
Scattered cells with endocrine
functions
FEATURES OF ENDOCRINE
GLANDS
Endocrine glands vary greatly in size.
The cells secreting the hormones
(parenchyma) are epithelial, epithelioid,
or neuronal.
The glands are richly vascularized by
highly permeable capillaries.
HYPOPHYSIS
• Located in
SELLA
TURCICA
• 1cm in length
• 1-1.3cm in
width
• Weighs 0.5-0.6
gm
ORGANIZATION
ADENOHYPOPHYSIS
Pars tuberalis
Pars distalisPars intermedia
NEUROHYPOPHYSIS
Pars nervosa
Infundibulum
(infundibular stem
& median eminence
)
ADENOHYPOPHYSIS
PARS DISTALIS
75% of the mass of the hypophysis
Common stains allow recognition of 3
cell types
o Chromophobes
o 2 types of chromophils
• Acidophils
• Basophils
PARS DISTALIS
• At higher
magnifications the
dark staining
chromophils ( A)
and the very light
staining
chromophobes (B)
are easily
distinguished.
ACIDOPHILS
Larger than chromophobes
Cells taking OrangeG stain are
alpha acidophils
Also called somatotrophs
Contain extensive RER
ACIDOPHILS
Carminophils stain intensely with
azocarmine
Also called mamotrophs
Cytoplasmic granules are larger
in size and are scattered
BASOPHILS
Larger than
acidophils
Best stained
with PAS
Subdivided
into beta and
delta cells
BASOPHILS
Beta cells secrete TSH
Larger in size
Granules concentrated at
periphery
Delta cells include
Gonadotrophs and coticotrophs
CHROMOPHOBES
Small rounded polygonal cells
Have little cytoplasm devoid of
granules
Appear in groups
They were called reserve cells in
past
PARS TUBERALIS
Funnel shaped
region
Surrounding the
infundibulum.
Most of the cells
secrete
gonadotropins
and are arranged
in cords along
blood vessels
PARS INTERMEDIA
Surrounds a series of small cavities
Parenchyma surround colloid filled
follicles
Pars intermedia contains basophils
and chromophobes
Basophils secrete MSH
Poorly developed in humans
PARS INTERMEDIA
PARS NERVOSA
Extension of CNS that
stores and releases
secretory products from
hypothalamus
Three types of
neurosecretory vesicles
NEUROHYPOPHYSIS
- PARS NERVOSA
This region of
the pituitary is
non secretory
 Its cells are
neuroglial-like
pituicytes
(C).
NEURO SECRETORY VESICLES
Herring bodies ranging 10-30nm contain
oxytocin or ADH
Vesicles containing acetylcholine approx
30nm in size
Vesicles ranging 50-80nm resembling
vesicles of adrenal medulla containing
adrenergic nerve endings
THYROID GLAND
C.T. sheath
formed by deep
cervical fascia
Extremely labile
gland & varies in
size & structure
Three dimensional view of thyroid follicles
DEVELOPMENT OF THYROID
GLAND
Begins to develop during 4th week of
gestation from a primordium
originating as an endodermal
thickening of floor of primitive
pharynx
STRUCTURAL UNIT OF THYROID
GLAND ----- THYROID FOLLICLE
FOLLICULAR EPITHELIUM
Follicular cells
Para follicular
cells
FOLLICULAR CELLS
PRINCIPAL/ CHIEF CELLS
Responsible for the
production of T3 & T4
Vary in size & shape
Slightly basophilic in
H & E stained slides
Lipid droplets & PAS
positive droplets
COLLOID
Inactive storage form of
thyroid hormone
Constituents
Principal component is
thyroglobulin (large
iodinated glycoprotein)
Enzymes
Glycoproteins
Staining with both acidic
& basic dyes. Strongly
with PAS
FUNCTION OF THYROID GLAND
PARAFOLLICULAR CELLS
C CELLS/ CALCITONIN CELLS
Located in periphery
of follicular epithelium
No exposure to lumen
 In H & E stained
slides appear as pale
staining cells
Secrete calcitonin