1. Histology of endocrine glands
Dr Abubakr H Mossa
MBBS, 8&11 /3/12

2. Outline Endocrine tissues/glands in the body
Basic structure of endocrine glands
Pituitary gland
Adenohypophysis
Neurohypophysis
Thyroid gland
Parathyroid glands
Adrenal glands
Cortex
Medulla
Islets of Langerhans (pancreas)

4. Endocrine tissues/glands in the body
Endocrine gland produces/secretes hormones to control or alter the function of other cells/tissue/organs
Endocrine function can be carried out by:
Glands like: pituitary, thyroid, parathyroid, adrenal and pineal glands
Clusters of cells in larger organs: ovarian follicles cells, islets of pancreas, Leydig cells of testes…
Scattered Single cells: enteroendocrine cells (GIT)..

5. Basic structure of endocrine glands
Endocrine glands have:
Parenchyma (cells): polyhedral, arranged in cords or plates, contain secretory vesicles
Blood vessels and capillaries: plenty, to convey the hormones and meet the high metabolic demand, in close relation to the cells
Little CT

6. Pituitary gland
Found in the ……….. of sphenoid bone at the base of brain (hypothalamus)
Master gland
Has two parts with different embryological origins
Adenohypophysis (anterior pituitary)
Neurohypophysis (posterior pituitary)

7. Pituitary gland: parts

8. Pituitary gland: cells
Adenohypophysis
Chromophils
Acidophils
Somatotrophs
(GH)
Mammotrophs
(prolactin)
Basophils
Thyrotrophes
(TSH)
Gonadotrophs
(FSH, LH)
Corticotrophs
(ACTH)
Chromophobes
Neurohypophysis
Axon terminals with Herring’s bodies
(ADH, oxytocin)
Pituicytes

9. Pituitary stalk

10. Adenohypophysis In pars distalis:
Cells which take the stain are called chromophils:
These are divided into acidophils (red) (A) & basophils (blue) (B)
Cells which do not stain are called chromophobes (C)

11. Adenohypophysis Pars intermedia: Pars tuberalis:
Contains mainly basophils
Function in humans not clearly known
Produces melanocytes stimulating hormones
Pars tuberalis:
Wraps partially the infundibulum
Highly vascular
No specific hormones secreted here in humans

12. Acromegaly?
Gigantism ?

13. Neurohypophysis
No production of hormones takes place here, only release of hormones form the nerve endings
The cell bodies of these neurons are in the hypothalamus (supraoptic & paraventricular nuclei)
The nerve endings contain secretory vesicles which are known as Hering’s (or neurosecretory) bodies (NB)
Contain ADH & oxytocin
The other type of cells in posterior pituitary is called pituicytes (P)which are glial cells sheathing the unmyelinated axons

14. Control of pituitary gland: vascular & neural connection to hypothalamus

15. Thyroid gland In the anterior aspect of the neck Has Isthmus & 2 lobes
Covered by pretracheal fascia
Divided into lobules by the CT septa
Each lobule contains follicles, parafollicular cells & capillaries
Follicles; sac like structure
Each follicle is surrounded by a basal lamina and reticular fibers
The follicle is lined by a simple cuboidal epithelium
The follicular cells secrete thyroxine T4 & T3
The height of the cells depends on the activity of the cells
Low or squamous: inactive or resting
High or columnar: active or secretory
The cavity of the follicle is full of colloid (acidophilic gel-like substance) for the storage of hormone-bound thyroglobulin
Parafollicular cells :lie between follicles, pale cells with round nucleus, secrete calcitonin

18. Parathyroid glands 4 in number, 2 superior & 2 inferior
Lie posterior to the thyroid gland
Have two types of cells:
Chief (principal cells):
most numerous,
acidophilic cytoplasm with round nucleus,
secretes parathyroid hormone (PTH) which increase blood calcium
Oxyphil cells:
less in number and
have deeply acidophilic cytoplasmic granules

20. Adrenal gland Lies on the top of the kidney Highly vascularized
Has two regions: cortex (larger) & medulla

22. Adrenal cortex; Has three layers (zones) which are not well demarcated
Zona glomerulosa: (mineralocorticoids; aldosterone)
Thin layer
Cells are arranged in circles or arches
Dark nucleus & acidophilic cytoplasm with few lipid droplets
Sinusoids present between cells
Zona Fasciculata: (glucocorticoids: cortisol)
Widest zone
Cells arranged in columns or cords
Large cells with pale staining nuclei and acidophilic cytoplasm containing plenty of lipid droplets
Zona reticularis: (androgens, estrogen)
Thin zone near the medulla
Cells are deeply staining with network like arrangement

24. Adrenal medulla
Cells here are large & arranged in groups or short cords with sinusoids in between
The cytoplasm of medullary cells is clear or light basophilic in H & E stain
These cells are called also chromaffin cells as they stain with dicromate salt in a reaction called chromaffin reaction (catecholamine containing cells take this stain). So these cells secrete adrenalin and nor adrenalin.
They are derived from the neural crest cells and respond directly to sympathetic nerve endings. So they are considered as postganglionic cells.
Other cells in medulla are the few but large parasympathetic ganglionic cells.

25. Medullary cells
Adrenal medulla

26. Vascular anatomy of adrenal glands

27. Islets of Langerhans This is the endocrine part of pancreas
Oval or round cluster of endocrine cells with plenty of capillaries in between
Has many types of cells
1 million islet and most are in the tail region

29. Cell types in islets of Langerhans

30. Thanks