Endocrine Glands

Prof Menna Abdel-Dayem Endocrineِ System

1. Glands, e.g. pituitary, suprarenal, , parathyroid glands and pineal body. 2. Masses of cells, e.g. endocrine part of pancreas, testis, , thymus. Endocrineِ glands

3. Cells scattered all over the body, e.g. APUD cells. Present in the base of the skull in “sella turcica”.

Connected to the by infundibular stalk.

Development

1- Adenohypophysis: develops from oral ectoderm as upward growth from roof of oral cavity forming Rathke’s pouch. 2- Neurohypophysis: develops from neuroectoderm as downward growth from floor of diencephalon. Both components unite to form pituitary gland.

Pituitary Gland

Adenohypophysis Pars Distalis

Covered with a thin C.T. capsule and supported by reticular C.T. Formed of cells arranged in groups or branching cords separated by fenestrated capillaries

Chromophobes (52%)

Small cells with pale cytoplasm which has mild affinity for stains. Types:

1- Granular and may secrete .

2- Non-granular: a) stem (undifferentiated) cells b) exhausted chromophils. Chromophils (48%)

Have affinity for stains.

Classified into: acidophils and basophils.

Acidophils (37%): Medium sized cells between chromophobes and basophils. Two types: (a) somatotrophs and (b) mammotrophs. Cell type (a) Somatotrophs (b) Mammotrophs Secrete growth hormone (GH): Secrete prolactin (lactogenic hormone) → milk • ↑secretion→ gigantism (before closure of secretion. epiphyses) & acromegaly (after closure of epiphyses). • ↓secretion→ dwarfism.

Gigantism:

Gigantism is an abnormally large growth due to excess growth hormone during childhood, before growth plates close.

The child is large for their age

Delayed puberty

Double vision or difficulty with peripheral vision

Headaches

Increased sweating

Large hands and feet

Thickening of facial features

Weakness

Prolactinoma

Headache and visual disturbance

In females, prolactinoma can cause:

•Irregular menstrual periods (oligomenorrhea) or no menstrual periods (amenorrhea)

•Milky discharge from the breasts (galactorrhea) when not pregnant or breast-feeding

•Acne and excessive body and facial hair growth (hirsutism)

In males, prolactinoma can cause:

•Decreased body and facial hair

•Uncommonly, enlarged breasts (gynecomastia)

Cell type (a) Somatotrophs (b) Mammotrophs Shape Spherical cells with central rounded nuclei and Oval cells with oval nuclei and acidophilic acidophilic granules. granules.

Reaction Give +ve reaction with orange G, so called Give +ve reaction with carmine, so called orangeophils. carminophils.

Somatotroph Mammotroph Cell type (a) Somatotrophs (b) Mammotrophs EM Cells have well developed Golgi, rER, Cells have well developed Golgi, rER, mitochondria & secretory granules. mitochondria & secretory granules, which enlarge during pregnancy & .

Pregnancy cells: due to high estrogen level, mammotrophs increase in number and size and secrete prolactin which stimulates development of mammary gland during pregnancy and milk secretion after birth. Cell type (a) Somatotrophs (b) Mammotrophs Hormone Secrete growth hormone (GH): Secrete prolactin (lactogenic hormone) → milk • ↑secretion→ gigantism (before closure of secretion. epiphyses) & acromegaly (after closure of epiphyses). • ↓secretion→ dwarfism.

Shape Spherical cells with central rounded nuclei and Oval cells with oval nuclei and acidophilic acidophilic granules. granules.

Reaction Give +ve reaction with orange G, so called Give +ve reaction with carmine, so called orangeophils. carminophils.

EM Cells have well developed Golgi, rER, Cells have well developed Golgi, rER, mitochondria & secretory granules. mitochondria & secretory granules, which enlarge during pregnancy & lactation. Chromophils (48%)

Have affinity for stains. Classified into: acidophils and basophils.

Basophils (11%): The largest cells. Cytoplasm has basophilic granules. Three types: (a) thyrotrophs (b) corticotrophs (c) gonadotrophs (c) Gonadotrophs Cell type (a) Thyrotrophs (b) Corticotrophs FSH secreting LH secreting cells cells Hormone Thyroid Adrenocorticotrophi FSH: LH: & its Actionstimulating c hormone (ACTH): In females → In females → hormone (TSH) Stimulates growth of ovarian ovulation & (thyrotropin): to follicles. formation of Stimulates secrete cortisol. In males → . thyroid gland to MSH: stimulates stimulates In males: it is secrete thyroid melanocytes of skin to spermatogenesis called ICSH hormones (T3 & form melanin. (interstitial cell T4). Endorphin →pain stimulating killer. hormone) → Lipotropic factor → stimulates lipid metabolism. interstitial cells of testis → testosterone. (c) Gonadotrophs Cell type (a) Thyrotrophs (b) Corticotrophs FSH secreting cells LH secreting cells

Shape Rounded cells with Oval cells with eccentric Rounded cells with rounded nuclei. central rounded nucleus. nucleus. EM All cells have mitochondria, well developed Golgi apparatus, rER& secretory granules. Castration cells: On bilateral removal of the testis, gonadotrophs increase in number & size & accumulate basophilic material pushing the nucleus which becomes flat & peripheral → signet-ring appearance. Shape of cells

Chromophobes: rounded with central nucleus

Acidophils: a)Somatotrophs: rounded with rounded nucleus b)Mammotrophs: oval with oval nucleus

Basophils: a)Thyrotrophs: rounded with rounded nucleus b)Gonadotrophs: rounded with rounded nucleus c)Corticotrophs: oval with eccentric nucleus

Upward extension of pars distalis that surrounds the infundibulum. Basophilic cells arranged in cords or follicles of unknown function but some secrete gonadotrophins.

Pars Intermedia

Formed of cords or follicles of basophilic cells with granular cytoplasm. Rudimentary in man. Pituitary Gland

Neurohypophysis I. Infundibulum

● Collection of nerve fibers (axons of neurosecretory cells of hypothalamus). ● Connect the hypothalamus with pars nervosa. II. Pars Nervosa

Secrete no hormones Contains: 1. 2. Nerve fibers 3. Herring bodies 4. Fenestrated blood capillaries Herring bodies (acidophilic bodies): – Accumulated neurosecretion in axon terminals of nerve fibers. – They contain: & . Function of pars nervosa: Site of storage of ADH & oxytocin secreted by supraoptic and paraventricular nuclei of hypothalamus. They reach the pars nervosa via hypothalamo-hypophyseal tract & stored in the axon terminals as Herring bodies till needed then released into the capillaries. Neurons present mainly in the Neurosecretory paraventricular & supraoptic nuclei of hypothalamus. Cells of Function: secrete the following hormones: 1. Oxytocin: Hypothalamus – Stimulates uterine contractions (in labor). – Stimulates contraction of myoepithelial cells of mammary gland → milk ejection during lactation. 2. Vasopressin (ADH): – H2O absorption in DCT & collecting tubules of kidney. – Vasoconstriction. 3. Other nuclei release some other Neurosecretory hormones such as: a. Somatotrophin releasing hormone: Cells of stimulates secretion of GH. b. Somatotrophin inhibiting hormone: Hypothalamus inhibits secretion of GH (somatostatin). c. Prolactin inhibiting hormone: inhibits secretion of prolactin (dopamine). d. Thyrotropin releasing hormone: stimulates secretion of TSH. e. Corticotropin releasing hormone: stimulates secretion of ACTH. f. Gonadotropin releasing hormone: stimulates secretion of gonadotropins (FSH & LH). Blood Supply of the Pituitary Gland