Detailed histology of endocrine glands. Microscopic structure of pituitary, thyroid, parathyroid and adrenal glands.

2. Objectives
• Introduction & General Features
• Development
• Types & Examples
• Microscopic structure of
– Pituitary Gland
– Thyroid & Parathyroid glands
– Adrenal Gland
• Applied

3. Endocrine System
• Comprises glands and tissues; consist of cells which
synthesize & secrete their products directly into blood
• These products are known as: Hormones
• Hormone: Greek word means
–To set in motion
• Along with the ANS, the endocrine system
co-ordinate & control the metabolic activities and
internal environment of the body

4. Endocrine Glands
• Ductless glands:
– Secretory pole of an endocrine cell is towards capillary
(or sinusoid)
– Release the hormones first into interstitial fluid
– Than enter the bloodstream through capillaries and
reach target organs
– Acts on cells that bear specific receptors for it &
produces hormone specific responses
– Some hormones act only on one organ / one type of
cell, while other may have widespread effects

5. Distributed in three ways:
• Major Endocrine glands
– Hypophysis Cereberi, Thyroid, Parathyroid, Suprarenal,
Pineal
• Organs contain group of endocrine cells
– Islets of Pancreas, Testes ,Ovary, Placenta, Kidney
• Isolated endocrine cells / APUD / Neuroendocrine
system
– Lining epithelium of GIT, Respiratory tract
Distributions of Endocrine Cells

7. Endocrine Glands
• Hormones: 4 main types based on chemical structure
1. Amino acid derivatives: Adrenalin, Noradrenalin &
Thyroxine
2. Small peptides: Encephalin, Vasopressin & Thyroid
Releasing Hormone
3. Proteins: Insulin, Parathormone & Thyroid Stimulating
Hormone
4. Steroids: Progesterone, Oestrogens, Testosterone &
Cortisol

8. Development of Glands
Developed as cords of
epithelial cells from the
surface of membrane
Invaginates in to underlying
Connective tissue &
Form 2 parts
Proximal
Part
Distal Part

9. Development of Glands
DisappearProximal Part
Distal Part
Endocrine Glands
Form islands of the secretory
cells permeated / surrounded
by the blood capillaries
Pours their secretion in to directly in to blood
through the blood capillaries
Ductless Gland *

10. Cord & Clump Type Follicular Type
Types of Endocrine Glands
Cells arranged in irregular
Cords / clumps permeated
by capillaries
Cells arranged in follicles
surrounded by capillaries
Secretions directly delivered
outward in capillaries
Secretions first delivered
inward inside the follicles

11. Cord & Clump Type Follicular Type
Endocrine Glands
Secretions stored inside
the cells
“Intra-cellular method”
Secretions stored outside
the cells, inside the follicles
“Extra-cellular method”
E.g. Most endocrine glands
Pituitary, Adrenal,
Parathyroid, Pineal
E.g.
Thyroid Gland

12. Major Endocrine Glands
• Pituitary / hypophysis cerebri
• Hypothalamus
• Thyroid & Parathyroids
• Adrenals
• Pineal

13. Pituitary Gland /
Hypophysis Cereberi

14. Pituitary Gland / Hypophysis Cerebri
• Master gland of endocrine system
• But under control of the hypothalamus
• Suspended from floor of 3rd ventricle
3rd ventrical

15. • Size of small pea
• Reddish grey ovoid body
• Measurements:
• Transverse - 12 mm
• Antero-posterior - 8 mm
• Weight- 500 mg
Pituitary Gland / Hypophysis Cerebri

16. Middle cranial fossaSella Turcica (Hypophyseal Fossa) Of Body Of Sphenoid
Sella Turcica
Position

17. Middle cranial fossaSella Turcica (Hypophyseal Fossa) Of Body Of Sphenoid
Position

18. Pituitary Gland
X-ray Skull: Lateral View Sagittal Section Of Head & Neck
Hypophyseal fossa
Pituitary
gland

19. Subdivisions of Pituitary Gland
Subdivided into 2 parts:
Differ from each other:
Embryologically, Morphologically & Functionally
Anterior Pituitary /
Adenohypophysis
Posterior Pituitary /
Neurohypophysis

20. Development
Rathke’s Pouch
Anterior Pitutary
Ectodermal roof of
Stomodeum
Posterior Pitutary
Floor of
Diencephalon

21. Anterior Pituitary / Adeno-hypophysis
Pars Distalis
Pars Anterior
Anterior Lobe
Pars Intermedia
Intermediate Lobe
Intraglandular Cleft
Pars Tuberalis
Tuberal Lobe
Further subdivided into 3 parts
Remnant of Rathke’s Pouch

22. Posterior Pituitary / Neuro-hypophysis
Pars Nervosa
Posterior Lobe
Neural Lobe
Pituitary stalk
Median Eminence
of Tuber Cinerum
Infundibular Stalk
Consists of 3 parts

24. Connections of Pituitary Gland
Hypothalamo-hypophyseal
Tract in Infundibulum
Consists of axons extending from
supraoptic & paraventricular
nuclei of hypothalamus &
terminate into the pars nervosa
Carry & release hormones from
hypothalamus to Pars Nervosa for
capillary uptake

25. Subdivisions of Pituitary Gland
Hypothalamo-hypophyseal
tract

26. Blood Supply Of Pituitary Gland
Superior
Hypophyseal artery
Inferior
Hypophyseal artery
Branches of internal
carotid artery
Supply
Neurohypophysis

27. Superior Hypophyseal artery
Form Primary capillary plexus
Secondary capillary plexus
In pars tuberalis, median
eminence & infundibular stem
In pars distalis
Hypophyseal portal veins
Transport hormones from
Hypothalamus or median
eminence to adenohypophysis
Hypophyseal veins

28. Connections with Hypothalamus
Hypothalamo-hypophyseal portal system:
• Regulatory hormones synthesised by the neurons
present in hypothalamus regulate the secretory activity
of the parenchymal cells present in pars distalis /
Adenohypophysis
Hypothalamo-hypophyseal tract:
• Made up of un-myelinated axons that carries the
hormones synthesised by the neurons present in
hypothalamus and transport it to the neurohypophysis

29. Microscopic Features
Adenohypophysis Neurohypophysis
Glandular tissue Neural tissue
Entire gland is covered by a connective tissue capsule

30. • Capsule adherent to dura
• No CSF around gland

31. Form 75% of the adenohypophysis
Consist of cells which are
arranged in clumps or
irregular cords
Separated by fenestrated
capillaries & sinusoids
Adenohypophysis: Pars Distalis & Tuberalis

32. Clumps or irregular cords
of cells
Separated by fenestrated
capillaries & sinusoids
Adenohypophysis: Pars Distalis & Tuberalis

33. Adenohypophysis:
Chromophobe /
Chromophil cells
Chromo = Stain / color / pigment
Philia = Attraction
Phobe / Phobia = Fear
Based of affinities for H& E
Cells are classified as
Chromophil – Easily stainable
Chromophobe – Less stained
Pars Distalis & Tuberalis

34. Chromophil cells
Large,
Numerous secretory granules
Stain intensely
Chromophobe cells
Smaller,
Few / no secretory granules
Stain faintly
Adenohypophysis: Pars Distalis & Tuberalis

35. Chromophil Cells
Chromophil Cells

36. Chromophil cells
Based on affinities for basic &
acidic dyes further classified in to
Acidophils
Basophils
Stained with acidic dyes: Eosin &
orange G
Stained with basic dyes:
Haematoxylin & PAS
Adenohypophysis:Pars Distalis & Tuberalis

39. Acidophil cells
Stained with acidic dyes: Eosin &
orange G
Round cells with cytoplasmic
granules
Based on hormone products;
divided in to:
Somatotrophs: Growth Hormone
Mammotrophs: Prolactin
Adenohypophysis:Pars Distalis & Tuberalis

40. Basophil cells
Stained with acidic dyes:
Haematoxylin & PAS
Polygonal with cytoplasmic granules
Based on hormone divided in to:
Thyrotrophs: TSH
Gonadotrophs: FSH & LH
Corticotrophs: ACTH
Adenohypophysis:Pars Distalis & Tuberalis

41. Secretory cells present in adenohypophysis(H&E)
• Chromophobes(no / absent granules)
• Chromophils(bright staining granules)
Acidophils (40%) Basophils(10%)
(somato- & mammotrophs) (cortico-; gonado- & thyro-)

48. Adenohypophysis:
• Poorly developed in the human
• Most conspicuous feature:
• Colloid filled vesicles
• Lined by cuboidal cells
• Remnants of Rathke’s pouch
• Basophilic cells arranged in
irregular clumps and cords
• Produce melanocyte-
stimulating hormone (MSH)
• Other secretory cells, &
chromophobes are also present
Pars Intermedia

49. Adenohypophysis: Pars Intermedia

54. Neurohypophysis:
• Stores the hormones
synthesized in hypothalamus
• Contains the hypothalamo-
hypophyseal tract:
• Unmyelinated axons of
neurosecretory cells
• Cell bodies located in
supraoptic & paraventricular
nuclei of hypothalamus
• Also contains supporting cells
called Pituicytes

55. Neurohypophysis:
Unmyelinated axons
Capillaries
Nuclei of Pituicytes

56. Hypothalamo–hypophyseal
Tract

57. Herring bodies:
Distended axon terminals containing mitochondria;
microtubules; sER & secretory vesicles in which hormones
are present

59. Supraoptic &
paraventricular
nuclie
Hypothalamo–
hypophyseal Tract
Herring Body

64. Gigantism
• Overproduction of GH
in adults before
epiphyseal closure

65. Acromegaly
• Overproduction of GH
in adults after
cessation of bone
growth

66. Diabetes Insipidus
• Deficient secretion of ADH
• Excretion of a very large
volume of dilute urine of
low specific gravity
(below 1.010)
• Polyuria and polydipsia

67. Thyroid Gland

68. Introduction
• Thyroid = Shield like
• Endocrine Gland-
Ductless
• Special Fetures?
– Manufacture, store &
release hormone when
required
– Depends on external
environment
– Richest blood flow

69. Parts of Glands
Right lobe Left lobe
Isthmus
Pyramidal lobe

71. Microscopic Features
• Stroma: Covered by capsule. Septa extends from capsule
divide the gland in to lobules & convey blood vessels,
nerves and lymphatics into gland
• Parenchyma: Contain hollow, spheroidal structures called
Thyroid follicles and Para-follicular cells

72. Microscopic Features
Follicles
Para-follicular Cells

73. Thyroid Follicles
• Basic structural &
functional unit of
thyroid gland
• Spherical in shape
• Diameter variable
• 50 – 500μm
• More than 20 million in
one gland

74. Thyroid Follicles
Lined by single layer of cells
rest on basement membrane
Follicular Cells
Lumen filled by gelatinous
homogeneous material
Colloid
Acidophilic – appear pink in H&E
Contains large glycoprotein Thyroglobulin
Precursor of thyroid hormones

75. Thyroid Follicles
• Follicular epithelium:- usually cuboidal
• But both epithelium & amount of
colloid varies depends upon
activity of gland
• In Highly Active Gland:
• Amount of colloid decreases
• Follicular cells become tall
• In Resting Gland:
• Amount of colloid increase
• Follicular cells become flat

76. • Resting gland:
– Lumen of follicle full of colloid
– Lined by simple squamous epithelium
• Highly active gland:
– Lumen of follicle contains less colloid
– Lined by simple columnar epithelium
• Moderately active gland: Most common
– Lumen of follicle contains moderate amount of colloid
– Lined by simple cuboidal epithelium
Thyroid Follicles

77. Colloid• Formed by the follicular cell
• Contains the large glycoprotein
thyroglobulin
• Inactive storage form /
Precursor of thyroid hormone
• Tyrosine residues +
glycoproteins + several
enzymes
• Thyroid is unique among
endocrine glands as
• It stores its secretory product
(in colloid)
• Stores extra-cellularly in the
lumen of the follicle

78. Thyroid Stroma
Spaces between the follicles
are filled by a stroma
Made up of delicate CT
containing numerous
capillaries and lymphatics
& sympathetic nerves
Capillaries lie in close contact
with the walls of follicles
For transfer of released hormone to the blood

79. Thyroid Stroma
Parafollicular / C cells
Between follicular cells &
basement membrane
May also lie as isolated
clusters between the follicles
Derived from the neural crest
Larger than follicular cells & pale staining
Secrete Calcitonin – Inhibit osteoclast

84. Follicular Cells / Thyrocytes
• Synthesize T3/T4
• Spherical nucleus with one or two
nucleoli
• Lateral domain show junctional
complexes
• Apical domain bears microvilli
• Cells show Basal Basophilia
– Numerous rER
• Apical part shows golgi complexes
& colloid resorption droplets

88. Steps in Synthesis of Thyroid Hormones
• Formation of thyroglobulin
• Resorption, diffusion & oxidation of iodide ions
• Iodination of thyroglobulin(formation of MIT; DIT)
• Formation of T3 & T4
• Resorption of colloid
• Release of T3 & T4

90. Applied Aspects

92. Myxoedema In Adult
Cretinism In Children

93. Nodular Goitre

94. PARATHYROID GLAND

96. Parathyroid Gland
• Small , yellowish-brown
lentiform bodies
(size of split pea)
• Situated along posterior border
of lobes of thyroid gland
• 2 – 6 in Number,
Mostly 4
• Arranged as 2 superior and
2 inferior pairs

97. Parathyroid Gland
Contain two types of cells
Chief Cells / Principal Cells
Oxyphil Cells

98. Parathyroid Gland
Chief Cells / Principal Cells
• Most numerous
• Polygonal in shape with
central spherical nucleus
• Cytoplasm: numerous
secretory granules
• Arranged in clumps or
irregular cords
• Large capillaries between
cords and clumps
Secrete Parathyroid Hormone
PTH or Parathormone

99. Parathyroid Gland
Oxyphil Cells
• Larger in size
• Fewer in number than
• Arranged in clumps
• Function is not clear

103. Applied anatomy of Parathyroid Gland
Hyperparathyroidism

104. Applied anatomy of Parathyroid Gland
• Hypoparathyroidism
– Tetany
– Hypocalcaemia
– Neuromuscular
Excitability
– Convulsion
– Carpopedal Spasm

105. Adrenal / Suprarenal Gland

107. Adrenal Gland
• Located at the upper pole of
each kidney
• Embedded in pararenal fat and
fascia
• Flattened & half-moon shape
• About
• 4-6cm long,
• 1-2cm wide, and
• 4-6mm thick in adults

108. Adrenal Gland
Has two components
Superficial Cortex
Deep Medulla
Covered by capsule from which septa
extend into the gland substance
Volume of the cortex is about
ten times more than medulla

109. • Adrenal cortex: constitutes major portion of gland
& secretes steroidal hormones
• Adrenal medulla: constitutes central part of gland &
secretes catecholamines

110. Adrenal Cortex
• Cells arranged in cords with
intervening sinusoids
• Cells of adrenal cortex have
features of steroid secreting
cells containing:
–Lipid droplets
–sER
–Mitochondria with long
tubular cristae

111. Adrenal Cortex
Consists of three zones:
Zona Glomerulosa
Zona Fasciculata
Zona Reticularis
Capsule
Medulla

113. Zona Glomerulosa
• Immediately inside the capsule &
constitutes 10-15%(1/5th) of cortex
• Consists of closely packed,
rounded / inverted U shaped /
arch-shaped cords of columnar or
pyramidal cells
– Separated by thin connective
tissue and capillaries
– Have basophilic cytoplasm &
deeply staining spherical nuclei
• Secrete Mineralocorticoids such
as Aldosterone

114. Zona Glomerulosa

115. Zona Glomerulosa

116. Zona Fasciculata
• Constitutes 65-80%(3/5th) of cortex
• Consists of large polyhedral cells,
arranged in in one (or two) cell
thick straight cords
– Cords are parallel to each other
– Separated by thin connective
tissue & fenestrated sinusoidal
capillaries
• Secrete Glucorticoids such as
Cortisol

117. Zona Fasciculata
• Cells are large in size & polygonal
in shape
– Single central spherical nucleus
• Cytoplasm: has numerous lipid
droplets
– During histological preparation,
the lipid is lost
– So cells appears vacuolated
– Hence, these cells are also
called
–Spongiocytes

118. Zona Fasciculata

119. Zona Fasciculata

120. Zona Reticularis
• Constitutes 10%(1/5th) of cortex
• Consists of polygonal cells,
arranged in cords that branch &
anastomose to form reticulum
– Separated by thin connective
tissue & wide capillaries
• Cells: Smaller but darkly stained
– Due to fewer lipid droplets &
more lipofuscin pigment
• Secrete steroid sex hormone,
Adrenal Androgen

121. Zona Reticularis

122. Adrenal Medulla
• Distinct from cortex both
functionally & embryologically
• Develops from neural crest
cells
• Consists of two types of cells:
–Chromaffin cells
(pheochromocytes)
–Ganglion cells

123. Chromaffin cells:
• Most numerous cells in medulla
• Ovoid-shaped secretory cells,
arranged in clumps or cords
surrounding the capillaries
• Cytoplasm: secretory granules
containing catecholamines (A&NA)
– Stain with chromium salts –
chromaffin reaction
– Hence cells are called
chromaffin cells

124. Chromaffin cells:
• Innervated by
preganglionic sympathetic
fibres and
• Correspond functionally
with postganglionic
sympathetic neurons
• Terminal ganglia of
sympathetic system

126. Ganglion cells:
• In addition to chromaffin cells,
the medulla also contains few
sympathetic ganglion cells,
• Present singly or in small
groups
• Larger than chromaffin cells

127. Adrenal Medulla

128. Adrenal Medulla

135. potassium dichromate
Staining for
chromaffin cells