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Histology of endocrine glands

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

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Histology of endocrine glands

  1. 1. Objectives • Introduction & General Features • Development • Types & Examples • Microscopic structure of – Pituitary Gland – Thyroid & Parathyroid glands – Adrenal Gland • Applied
  2. 2. 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
  3. 3. 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
  4. 4. 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
  5. 5. 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
  6. 6. 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
  7. 7. 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 *
  8. 8. 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
  9. 9. 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
  10. 10. Major Endocrine Glands • Pituitary / hypophysis cerebri • Hypothalamus • Thyroid & Parathyroids • Adrenals • Pineal
  11. 11. Pituitary Gland / Hypophysis Cereberi
  12. 12. Pituitary Gland / Hypophysis Cerebri • Master gland of endocrine system • But under control of the hypothalamus • Suspended from floor of 3rd ventricle 3rd ventrical
  13. 13. • Size of small pea • Reddish grey ovoid body • Measurements: • Transverse - 12 mm • Antero-posterior - 8 mm • Weight- 500 mg Pituitary Gland / Hypophysis Cerebri
  14. 14. Middle cranial fossaSella Turcica (Hypophyseal Fossa) Of Body Of Sphenoid Sella Turcica Position
  15. 15. Middle cranial fossaSella Turcica (Hypophyseal Fossa) Of Body Of Sphenoid Position
  16. 16. Pituitary Gland X-ray Skull: Lateral View Sagittal Section Of Head & Neck Hypophyseal fossa Pituitary gland
  17. 17. Subdivisions of Pituitary Gland Subdivided into 2 parts: Differ from each other: Embryologically, Morphologically & Functionally Anterior Pituitary / Adenohypophysis Posterior Pituitary / Neurohypophysis
  18. 18. Development Rathke’s Pouch Anterior Pitutary Ectodermal roof of Stomodeum Posterior Pitutary Floor of Diencephalon
  19. 19. 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
  20. 20. Posterior Pituitary / Neuro-hypophysis Pars Nervosa Posterior Lobe Neural Lobe Pituitary stalk Median Eminence of Tuber Cinerum Infundibular Stalk Consists of 3 parts
  21. 21. 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
  22. 22. Subdivisions of Pituitary Gland Hypothalamo-hypophyseal tract
  23. 23. Blood Supply Of Pituitary Gland Superior Hypophyseal artery Inferior Hypophyseal artery Branches of internal carotid artery Supply Neurohypophysis
  24. 24. 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
  25. 25. 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
  26. 26. Microscopic Features Adenohypophysis Neurohypophysis Glandular tissue Neural tissue Entire gland is covered by a connective tissue capsule
  27. 27. • Capsule adherent to dura • No CSF around gland
  28. 28. 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
  29. 29. Clumps or irregular cords of cells Separated by fenestrated capillaries & sinusoids Adenohypophysis: Pars Distalis & Tuberalis
  30. 30. 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
  31. 31. Chromophil cells Large, Numerous secretory granules Stain intensely Chromophobe cells Smaller, Few / no secretory granules Stain faintly Adenohypophysis: Pars Distalis & Tuberalis
  32. 32. Chromophil Cells Chromophil Cells
  33. 33. 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
  34. 34. 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
  35. 35. 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
  36. 36. Secretory cells present in adenohypophysis(H&E) • Chromophobes(no / absent granules) • Chromophils(bright staining granules) Acidophils (40%) Basophils(10%) (somato- & mammotrophs) (cortico-; gonado- & thyro-)
  37. 37. 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
  38. 38. Adenohypophysis: Pars Intermedia
  39. 39. 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
  40. 40. Neurohypophysis: Unmyelinated axons Capillaries Nuclei of Pituicytes
  41. 41. Hypothalamo–hypophyseal Tract
  42. 42. Herring bodies: Distended axon terminals containing mitochondria; microtubules; sER & secretory vesicles in which hormones are present
  43. 43. Supraoptic & paraventricular nuclie Hypothalamo– hypophyseal Tract Herring Body
  44. 44. Gigantism • Overproduction of GH in adults before epiphyseal closure
  45. 45. Acromegaly • Overproduction of GH in adults after cessation of bone growth
  46. 46. 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
  47. 47. Thyroid Gland
  48. 48. Introduction • Thyroid = Shield like • Endocrine Gland- Ductless • Special Fetures? – Manufacture, store & release hormone when required – Depends on external environment – Richest blood flow
  49. 49. Parts of Glands Right lobe Left lobe Isthmus Pyramidal lobe
  50. 50. 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
  51. 51. Microscopic Features Follicles Para-follicular Cells
  52. 52. Thyroid Follicles • Basic structural & functional unit of thyroid gland • Spherical in shape • Diameter variable • 50 – 500μm • More than 20 million in one gland
  53. 53. 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
  54. 54. 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
  55. 55. • 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
  56. 56. 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
  57. 57. 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
  58. 58. 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
  59. 59. 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
  60. 60. 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
  61. 61. Applied Aspects
  62. 62. Myxoedema In Adult Cretinism In Children
  63. 63. Nodular Goitre
  65. 65. 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
  66. 66. Parathyroid Gland Contain two types of cells Chief Cells / Principal Cells Oxyphil Cells
  67. 67. 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
  68. 68. Parathyroid Gland Oxyphil Cells • Larger in size • Fewer in number than • Arranged in clumps • Function is not clear
  69. 69. Applied anatomy of Parathyroid Gland Hyperparathyroidism
  70. 70. Applied anatomy of Parathyroid Gland • Hypoparathyroidism – Tetany – Hypocalcaemia – Neuromuscular Excitability – Convulsion – Carpopedal Spasm
  71. 71. Adrenal / Suprarenal Gland
  72. 72. 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
  73. 73. 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
  74. 74. • Adrenal cortex: constitutes major portion of gland & secretes steroidal hormones • Adrenal medulla: constitutes central part of gland & secretes catecholamines
  75. 75. 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
  76. 76. Adrenal Cortex Consists of three zones: Zona Glomerulosa Zona Fasciculata Zona Reticularis Capsule Medulla
  77. 77. 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
  78. 78. Zona Glomerulosa
  79. 79. Zona Glomerulosa
  80. 80. 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
  81. 81. 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
  82. 82. Zona Fasciculata
  83. 83. Zona Fasciculata
  84. 84. 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
  85. 85. Zona Reticularis
  86. 86. Adrenal Medulla • Distinct from cortex both functionally & embryologically • Develops from neural crest cells • Consists of two types of cells: –Chromaffin cells (pheochromocytes) –Ganglion cells
  87. 87. 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
  88. 88. Chromaffin cells: • Innervated by preganglionic sympathetic fibres and • Correspond functionally with postganglionic sympathetic neurons • Terminal ganglia of sympathetic system
  89. 89. 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
  90. 90. Adrenal Medulla
  91. 91. Adrenal Medulla
  92. 92. potassium dichromate Staining for chromaffin cells