Histology of endocrine glands

Dr Abubakr H MossaMBBS, 8&11 /3/12

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)

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)..

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

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)

Pituitary gland: parts

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

Pituitary stalk

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)

Adenohypophysis

• Pars intermedia:– 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

Gigantism ?Acromegaly?

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

Control of pituitary gland:vascular & neural connection to hypothalamus

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

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

Adrenal gland

• Lies on the top of the kidney • Highly vascularized• Has two regions: cortex (larger) & medulla

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

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.

Adrenal medulla

Medullary cells

Vascular anatomy of adrenal glands

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

Cell types in islets of Langerhans

Thanks