unit 2 – endocrine module histology of the hypophysis and adrenal glands safaa el bialy (md, phd)
TRANSCRIPT
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