Unit 2 – Endocrine Module

Histology of the hypophysis and adrenal glands

Safaa El Bialy (MD, PhD)

Objectives

• Describe the histology of the hypophysis• Compare the embryological origin of the adrenal

cortex and medulla. Name two common locations of aberrant tissue

• Describe the histology of the adrenal cortex and medulla

• The hypothalamus is the link between the endocrine system and the nervous system

• The hypothalamus controls secretions of the hypophysis• The hypophysis controls secretions of several endocrine

glands (adrenal cortex, thyroid, gonads)• Control of secretions is by feedback mechanism

Hypothalamic-hypophyseal-adrenal/thyroid/gonadal axis

Hypophysis (pituitary gland)

• Located at the base of the brain, in the sella turcica– approximately 1 cm in diameter

• Secretes 2 types of hormones:– hormones acting directly on non-endocrine tissues

• growth hormone (GH)• prolactin• antidiuretic hormone• oxytocin• melanocyte-stimulating hormone (MSH)

– hormones modulating secretory activity of other endocrine glands• TSH (thyroid)• ACTH (suprarenal cortex)• FSH, LH (gonadotropins) (gonads)

site of the hypophysissella turcica

hypophysis

Hypophysis

• Divided into 2 parts:– posterior hypophysis

(neurohypophysis or pars nervosa)• derives from a downward

extension of hypothalamic nervous tissue

• secretes antidiuretic hormone (vasopressin) and oxytocin

– anterior hypophysis (adenohypophysis)• derives from an epithelial

evagination (ectoderm) of the roof of the oral cavity (Rathke’s pouch)

• secretes TSH, ACTH, FSH, LH, GH and prolactin

adenohypophysis neurohypophysis

Embyological development of the hypophysis

Embyological development of the hypophysis

http://php.med.unsw.edu.au/embryology/images/4/47/Pituitary_development_animation.gif

optic chiasm

pars tuberalis

pars distalis

adenohypophysis(TSH, ACTH, FSH, LH, GH, prolactin)

pars intermedia (secretes MSH)

pars nervosa (ADH, oxytocin)

pituitary stalk

hypothalamic nuclei

Hypophysis and hypothalamus

superior hypophyseal artery

inferior hypophyseal artery

capillary plexus

capillary plexus

hypophyseal portal vein

Hypophysis

pars intermedia

and

pars distalis

of the adenohypophysis

pars nervosa (neurohypophysis)

capsule

pars distalis

cysts (remnants of Rathke’s pouch)

pars nervosa

pars intermedia

Hypophysis

Adenohypophysis

• Cords of secretory cells separated by capillaries or sinusoids

• Cells:– chromophobes (50%) faint color– chromophils (50%)

• acidophils (40%)– secrete GH and prolactin

• basophils (10%)– secrete ACTH, TSH, FSH, LH

capillary

connective tissue

basophil

acidophil

chromophobe

Adenohypophysis

Types ofchromophils

Cell names Hormones secreted by chromophils

Targets Functions

Acidophils

Somatotrophs

Lactotrophs Prolactin(PRL)

Growth hormone (GH)

All cells of the body Growth

Mammary glands

Milk production and mammary development

Basophils

Corticotrophs

Thyrotrophs

Gonadotrophs

CRH (+)

TRH (+)&

GHIH (-)

GNRH (+)

Adreno-corticotropic

hormone (ACTH)

Fasciculate and reticulate zones of the

adrenal cortex

Synthesis and secretion of glucocorticoids and

sex hormones

Thyroid-stimulating

hormone (TSH)

Follicle-stimulating

hormone (FSH) Luteinizing

hormone (LH)

Thyroid gland

Testicles and ovaries

Synthesis and secretion of T3 and T4

Stimulation of

spermatogenesis; follicle

maturation and ovulation; synthesis and secretion

of sex hormones

GHRH (+)&

GHIH (-)

TRH (+)PRH (+)

PIH (-)

Hypothalamic hormonescontrollingchromophils

Pars intermedia

• Clump of basophilic cells of the adeno-hypophysis lying between the pars distalis and the pars nervosa

• Cells (melanotrophs) producing melanocyte-stimulating hormone (MSH)

• Rudimentary structure • Contains small cavities = Rathke cysts

– filled with mucin and covered in a cuboidal epithelium

Neurohypophysis• Contains non-myelinated axons of neurosecretory

neurons of the hypothalamus– presence of granules (Herring bodies) containing:

– antidiuretic hormone (ADH) – oxytocin

• Fenestrated capillaries– surround terminal parts of axons for transporting hormones in

the bloodstream • Pituicytes

– glial cells– surround and support non-myelinated axons

Neurohypophysis

• Rich in non-myelinated axons of neurosecretory cells• Support cells = pituicytes

Herring body

capillary

pituicytes

Neurohypophysis

Pathology of the hypophysis

• Hypophyseal adenoma :• Benign tumor• Continuous production of hormones• ACTH → Cushing disease • GH → Gigantism or acromegaly • If the volume increases → compression of optic nerves and

chiasm resulting in impaired vision and even blindness• Panhypopituitarism :• Destruction of the pituitary and decrease hormone secretions

Adrenal glands• The adrenal glands are the endocrine

glands resting on the upper pole of the kidneys

• Comprised of: – adrenal cortex

• same embryological origin as the gonads (mesoderm)

• secretes steroid hormones – adrenal medulla

• same embryological origin as the sympathetic nervous system (neural crest)

• secretes catecholamines (adrenaline and noradrenaline)

adrenal cortex medulla

kidneykidney

adrenal glandadrenal gland

Accessory adrenal glands

• Usually without accompanying medullary tissue

• Common sites: retroperitoneal space along urogenital ridge, beyond renal capsule in upper pole, hilum of ovary or testes and along course of spermatic cord

• May be fused with liver or kidney and surrounded by a common capsule

• May undergo same disease processes as ordinary adrenal glandular tissue

Adrenal gland

cortex

medulla

capsulezona glomerulosa

zona fasciculata

zona reticularis

Adrenal cortex• 3 layers

– Glomerulate (zona glomerulosa)• outer layer• Cells arranged in groups and are smaller that the cells of the two other zones• cells have abundant smooth ER, mitochondria and a few lipid droplets

(cholesterol)• secrete mineralocorticoids (e.g. aldosterone)

– Fasciculate (zona fasciculata)• middle zone, thickest• Cells arranged in cords• cells have abundant smooth ER, mitochondria and lipid droplets (pale-staining

cells)• secrete glucocorticoids (e.g. cortisol) and a small quantity of androgens

– Reticulate (zona reticularis)• inner layer• Anastomosing cords of cells• cells have a few lipid droplets, strong staining• secrete a small quantity of androgens and glucocorticoids

Adrenal cortex

zona glomerulosa

zona fasciculata

zona reticularis

NB: Lack of colour corresponds to the quantity of lipid droplets, and therefore to steroid synthesis from cholesterol

Suprarenal cortex

• It is in the fascicular area that cord appearance of the gland is the most visible. In 1 , cell cords alternate with blood vessels, 2. cords usually are two cells wide . We see in 3 endothelial nuclei ,. 4 , many capillaries compressed between cords

Zona fasciculata

Suprarenal cortex

• Glomerular zone

• Zona fasciculata

• Zona reticularis

Adrenal medulla

• Structure– tight groups of secretory cells (chromaffin cells)

• modified neurons similar to post-ganglionic sympathetic neurons

• large nucleus, abundant basophilic cytoplasm with granules containing catecholamines (adrenaline and noradrenaline)

– numerous large capillaries– venous canals drain blood from the sinusoids of the

cortex to empty into the central vein of the adrenal medulla

– there are also ganglion cells (sympathetic nerves) innervating the tissue and controlling the secretion of catecholamines

Adrenal medulla

• In 1 , very clear , lipid-rich fascicular area ; 2 , the most pigmented reticular area , It is easily differentiated from the medulla , noted 3 , more purplish hue . Into the medulla , the cells are always grouped into small anastomosed cords separated by 4 by blood capillaries.

chromaffin cells

capillary

ganglion cells

Adrenal medulla

Adrenal gland

angiotensin II

ACTH

ACTH

signals from sympathetic nervous system

aldosterone

cortisol & androgens

cortisol & androgens

epinephrine & norepinephrine