Endocrine Histology
Dr. Dennis Ivan Bravo
Overview
Two systems control all physiologic
processes
nervous system exerts point-to-
point control through nerves
Endocrine system controls by
secretion of hormones to the
bloodstream
Nervous Endocrine
Endocrine system
Hypothalamus Pancreas
Pituitary gland Adrenal gland
Thyroid gland Testicle
Parathyroid gland Ovary
Pineal
Pituitary Gland
• Located at base of brain, surrounded by Circle of
Willis
• Infundibulum - connection to hypothalamus
• In sella turcica of sphenoid bone
• Two parts with separate embryonic origins:
• Anterior Pituitary
• Posterior Pituitary
Anterior pituitary
• Anterior Pituitary (adenohypophysis)
• AKA pars distalis
• Production of 7 hormones
• 4 are tropic hormones, stimulating other endocrine glands
• Pars intermedia and pars tuberalis secrete MSH
Posterior pituitary
• Posterior Pituitary (= neurohypophysis)
• AKA pars nervosa
• Storage reservoir for ADH and Oxytocin
Scanner view
LPO view
Pars Intermedia
Vesicles with colloid
capillary
Pars Distalis
Basophils
acidophils
LPO view
Pars Distalis
acidophils
Basophils
chromophobes
HPO view
Basophil
Eosinophil
Chromophobe
Pars distalis
• Acidophils tend to be located in center. Secrete
protein hormones lgrowth hormone and prolactin.
• Basophils are at edges. Secrete glycoprotein
hormones ACTH, TSH, FSH, and LH.
• Chromophobes have clear nuclei and scant
cytoplasm. They may be cells that are non-
secretory or exhibit minimal hormone storage.
Pars Nervosa
LPO view
Pars Nervosa
HPO view
Herring bodies
Nuclei of pituicyte
HPO view
HPO view
Thyroid Gland
! Anterior surface of
trachea just inferior of
thyroid cartilage (or
Adam’s apple)
! Two lobes connected by
isthmus
Thyroid
• Thyroid follicular cells (simple
cuboidal epithelium) produce
and store thyroglobulin in
thyroid follicles
• C Cells: parafollicular cells
produce calcitonin
• Interspersed between thyroid
follicles
• Lower blood Calcium
LPO view
HPO view
Parathyroid
• 4 tiny glands embedded in the posterior aspect of
the thyroid (superior and inferior)
• Parathyroid hormone (PTH; sometimes also called
parathormone)
• Function:
• Raises blood Ca2+
• Antagonist to Calcitonin
Scanner view
LPO view
Chief cells
Oxyphil cells
Pancreas
• Gland with double duties: Endocrine and exocrine functions
• Exocrine anatomy
• CT capsule surrounds pancreas
• Septa divide it into sections
• Compound acinar gland
• Secretions:
• 1500 – 3000ml pancreatic fluid (alkaline)
• Contain water, ions, proteases, lipases, amylas
• e, nucleases, ribonuclease
LPO view
Exocrine pancreas
The structure of pancreatic acini. Acinar cells are
pyramidal, with granules at their apex and rough
endoplasmic reticulum at their base. The duct partly
penetrates the acini.
Endocrine Gland
Islet of Langerhans
α cells (glucagon) ~ 20%
β cells (insulin) ~ 70%
Δ cells (somatostatin) ~ 5%
Acini Islet of Langerhans
HPO view
HPO view
HPO view
Glucagon Insulin
HPO view
Islet cells form
cords separated by
blood capillaries,
here seen as white
spaces.
Islet is surrounded by
reticular fibers
separating it from
acinar cells.
H&E stain. Medium
magnification.
HPO view
An islet of
Langerhans
showing alpha
cells and beta
cells.
Gomori stain. Medium
magnification.
Adrenal
• Divided into
• Cortex
• Medulla
Adrenal
• Adrenal cortex
• Zona Glomerulosa—
Aldosterone
• Zona fasciculata—
Glucocorticoids
• Zona reticularis—
Androgens
Adrenal
• Adrenal Medulla: modified
sympathetic ganglion
produces epinephrine and
norepinephrine
• Adrenalin® = adrenaline =
epinephrine
• Neuroendocrine gland
Scanner view
Cortex
Medulla
Cortex
LPO view
Zona Glomerulosa
Zona Fasciculata
Zona Reticularis
HPO view
Zona
Glomerulosa
(clumps, cords,
and follicle like
structures
Zona Fasciculata
(cords of
spongiocytes)
HPO view
Zona fasciculata
Zona reticularis
HPO view
Testes
• Secrete testosterone into the
bloodstream
• From interstitial cells
• Stimulates sperm production
(along with FSH)
• Secondary sex characteristics
• Inhibin (balances FSH)
• From sustentacular (Sertoli) cells
HPO view
Ovary
• Estrogen—by ovarian follicles
in response to FSH
• Progesterone—by the corpus
luteum in response to LH
• Inhibin—decreases estrogen
production
Scanner view
Granulosa cells produce HPO view
estrogen
Theca interna cells
produce estrogen
precursors,
androgens
Pineal gland
• Part of epithalamus
• Secretes melatonin
• Derivative of serotonin
• Regulates circadian
Rhythms (sleep cycle)
• Inhibits hypothalamic
releasing factors
LPO view
HPO view
The end
