Endocrine System 内 分 泌 系 统 泸州医学院组胚教研室 Teacher: Wang Qiao Zhi

Main contents ： General Introduction Thyroid gland( 甲状腺 ) Parathyroid gland ( 甲状旁腺 ) Adrenal gland （肾上腺） Hypophysis （垂体）

General Introduction  1. Composition of Endocrine system endocrine organs Thyroid gland Parathyroid gland Adrenal gland Hypophysis Pineal body endocrine structures islets of Langerhans corpus luteum isolated endocrine cells digestive tract interstitial cells in the testis hilus cells in the ovary

 capsule: CT  parenchyma: endocrine cells are arranged in nests/clusters, or cords, or follicles. secrete hormones 2. General structure  interstitium: CT, rich in capillaries It is the most important method that we identify any endocrine glands in L.M.  There is no duct. （ ductless glands ）

Exocrine  Secretory products are delivered to lumen via ducts Endocrine  Glands release hormones into blood or the extracellular matrix 3. Contrast to exocrine glands paracrine secretion: H into the extracellular matrix. flow from cell to cell by diffusion. Distance secretion ： H into the caps, transported by the blood circulation to distant target cells

Hormones: Chemical messenger secreted into blood and carried to “target cells” where it alters activity. 4. Hormones Peptide Protein Amino acid analogs and derivatives Classes of Hormones ： According to biochemical structure: nitrogenous -hormone Steroid hormone cholesterol derivatives target cell: any cell that has a corresponding receptor for specific hormone

Hormone + Receptor

* nitrogenous-hormone secreting cell:  RER  Golgi  secretory granules

* steroid-hormone secreting cell:  SER  mitochondria: with lamellar or tubular cristae  lipid droplet: raw materials

Functions of Endocrine system :  Secrete hormones that coordinate and direct activities of target cells/organs  Regulates mood, growth,development,metabolism, sexual function, reproduction, blood pressure,etc  Most systems are under combined control of endocrine and nervous systems ES and NS = 2 main control systems of body

Thyroid gland ---largest endocrine gland, 15-40g ---two-lobes, connect to each other by isthmus

1) General structure: ---capsule of LCT: insert into parenchyma to separate them into lobules ---parenchyma: follicles

甲状腺滤泡 thyroid follicle （ 甲状腺滤泡 ） simple cuboidal epithelium 滤泡上皮细胞 ( follicular epithelial cell ) 滤泡旁细胞（ parafollicular cell ） lumen ： Colloid -iodinated thyroglobulin 碘化的甲状腺球蛋白 ---spherical Sac, mm HE: eosinophilic, homogeneous structure

① Follicular epithelial cell ---structure: LM:  cuboidal: flattened(inactive) or columnar ( more active)  spherical centrally-located Nucleus  basophilic cytoplasm 胶质

EM:  microvilli  Golgi, secretory granules in the supranuclear area  RER, lysosome Function: synthesize and release thyroid hormones thyroxine(T4) triiodothyronine(T3)

Luminal surface is Many microvilli Basal surface rests on a thin basement membrane FENESTRATED CAPILLARIES run in close proximity to the basement membrane hormones synthesis of processes: i. synthesis of thyroglobulin ii. Uptake of circulating iodide iii. Iodination of thyroglobulin ⅳ. Release of thyroid hormones glycosylation

 increase the basal metabolism rate  promote the cell growth  raise body temperature  increase heart rate  play a role in fetal and neonatal development of CNS Function of thyroid hormones:

Common symptoms : shaking, increased nervousness, irritability Rapid heart beat or palpitations Feeling hot Weight loss Fatigue, feeling exhausted More frequent bowel movements Enlarged gland eye symptoms, bulging of the eyes Hyperthroidism (Overactive Thyroid)

Hypothyroidism (Underactive thyroid)  Fatigue or lack of energy  Weight gain  Feeling cold  Dry skin and hair  Heavy menstrual periods  Constipation  Slowed thinking Myxedema face

呆小症 / 克汀病 Cretinism Poor growth (height) Neurological impairment Delayed bone maturation Thickened skin Infertility Dementia face

3) parafollicular cell ---single between follicular epithelial cell ---in small groups in the interstitial spaces outside the thyroid follicles ---structure:

LM: /ovoid, polygonal /larger /pale-stained /argyrophilic granulesgranules EM: /nitrogenous-hormone secreting cell feature /granules: contain calcitonin Function: promoting activity of osteoblast and suppressing the absorption of calcium in digestive tract and kidndy.

Parathyroids ( 甲状旁腺 )  Located on posterior surface of thyroid  chief (principal) cells and oxyphil cells  Parathyroid hormone (PTH)  Stimulates Ca 2+ release from bone  Promotes intestinal absorption and renal tubular reabsorption of calcium

Parathyroids( 甲状旁腺 ) Chief cells

Adrenal gland ---paired, situated on the upper poles of kidney.

Adrenal gland --- capsule: CT ---cortex: outer portion, derived from mesoderm ---medulla: inner portion, derived from neuroectoderm cortex

1) adrenal cortex: ---constitutes 80-90% of total volume ---three zones: glomerulosa, fasciculata, reticularis

reticularis glomerulosa fasciculata 15% of cortex volume 78% 7% Cortex cells secret steroid-hormone.

LM: /small, low columnar or pyramidal cell /arranged into rounded or arched configuration /chromatin-dense nucleus,acidophilic cytoplasm ① zona glomerulosa: Beneath the capsule EM: /steroid-hormone secreting cell feature Function: mineralocorticoid- aldosterone (reabsorb Na+ and release K+) 球状带

LM: /large, polygonal or columnar cell / arranged into cords, perpendicularly to the surface / containing numerous lipid droplets, appear vacuolated ② zona fasciculate: 78% 束状带

EM: /steroid-secreting cell feature /more lipid droplets Function: secret glucocorticoid- cortisol or corticosterone /promote protein and fat transfer into glucose /impair inflammatory /reduce immune reaction

LM: / polygonal, small cell /arranged into cord to form network /acidophilic cytoplasm ③ zona reticularis: 球状带 EM: /steroid-secreting cell feature /less lipid droplet and more lipofuscin pigment Function: secret androgen(testosterone) and small amount of oestrogen 7%

LM: /polyhedral, large nests or short cords /weakly basophilic cytoplasm 2) Adrenal medulla ① medullary cell: brownish granules- when fixed by bichromate-containing fixative This brownish colour is produced by a reaction between the chromium, hence the term chromaffin cells.

EM &Function /electron-dense granules:  adrenaline cell: 80% i. increase the heart rate ii. dilate BV  noradrenaline cell: 20% i. increase blood pressure ii. increase the flow speed of blood

② ganglial cell: polypolar neurons- large ③ central vein: central vein

upper body obesity round or moon-shaped face increased fat around neck thinning arms and legs fragile and thin skin acne stretch marks on abdomen, thighs bone and muscle weakness severe fatigue high blood sugar irritability and anxiety excessive hair growth in females Cushing's Syndrome Reason: hypersecretion of glucocorticoid by the adrenal cortex

Pituitary gland (hypophysis) connects to the hypothalums through a stalk called the infundibulum. ovoid, flattened organ, 0.5g in weight, in pituitary fossa of sphenoid bone

adenohypophysis neurohypophysis anterior lobe The pars nervosa and pars intermedia constitute posterior lobe. Pituitary gland

embryologic origin Rathke's pouch oral cavity Adenohypophysis derived from an outpocketing of the oral ectoderm, called Rathke's pouch neurohypophysis derived from the downgrowth of the neuroectoderm of the floor of the third ventricle,called the infundibulum.

hypophysis:showing the three parts: pars distalis( ), pars intermedia( ) and pars nervosa( ※ ). （ pig ， H.E ， ×40 ）

1) The pars distalis The cells are arranged in clusters or cords that are separated by fenestrated sinusoidal capillaries.

1) The pars distalis （ 1 ） chromophobe cell( 嫌色细胞 ) ： （ 2 ） chromophil cell ( 嗜色细胞 ) ： 嗜酸性细胞 a. acidophils ( 嗜酸性细胞 ) 嗜碱性细胞 b. basophils ( 嗜碱性细胞 ) according to their staining affinity EM: chromophil are nitrogenous- hormone secreting cell

① acidophil: 40% LM:  round, ovoid  Strong eosinophilic i. somatotroph: growth hormone(GH): promote the growth and metabolism of bone ii. mammotroph: prolactin(PRL): promote the growth and secreting of mammory gland after pregnancy. EM:According to size and appearance of granules

② basophil: LM:  less, large cell  ovoid or polyhedral  basophilic cytoplasm 10%

 i. thyrotroph: -thyroid stimulating hormones(TSH) stimulates the growth of the thyroid follicular epithelial cells and the synthesis and release of thyroid hormones.  ii. corticotroph: - adrenocorticotropic hormone(ACTH) stimulates the cells of the zone fasciculata and reticularis of the adrenal cortex to synthesize and secrete glucocorticoids.

 iii. Gonadotroph  -luteinizing hormone(LH):  -follicle stimulating hormone(FSH): Female: development of ovarian follicle Male: spermatogenesis in testis Female: ovulation and formation of corpus luteum, secretion of progesterone Male: interstitial cell-stimulating hormone(ICSH), regulate the secretion of androgen by Leydig cell in testis

③ chromophobe cell ---structure: LM: /more, small, pale stain /no clear boundary 50% Function: i. degranulated cell ii. under-development cell EM: few or no granules

2) The pars intermedia ---structure: /chromophobe cell &basophil /follicle: simple cuboidal epi. + colloid *basophil: melanocyte stimulating hormone(MSH) which causes dispersion of melanin granules in the melanophores and causes a darkening of the animal's skin

※ hypophyseal portal system: Superior hypophyseal arteries(arisig from the cerebral arterial circle ) primary capillary plexus (infundibular stalk) hypophyseal portal veins secondary capillary plexus (the pars distalis) small vein Function: importance structure to connect hypothalamus and adenohypophysis

※ Relationship between hypothalamus and adenohypophysis arcuate nucleus of hypothalamus: secrete releasing hormone(RH) release inhibition hormone(RIH) hypophyseal portal system their axons end in infundibular stalk and release hormones into primary plexus H into the anterior pituitary and regulate cells hormone secretion Hypothalamus control of hormone secretion from the adenohypophysis

a.unmyelinated nerve fibers : axons of hypothalamus cells b. pituicyte: c. fenestrated capillaries 3) Neurohypophysis special glial cell irregular with processes cytoplasm contain pigment granules function: support and nourish NF pituicyte

※ Relationship between hypothalamus and Neuro hypophysis Neurohypophysis is a place which store and release Hypothalamus hormones.

To grasp the general structures of the endocrine organs. Light microscopic structure and secreting hormone of thyroid, parathyroid gland, adrenal gland and pituitary. Composition of hypophysial portal system and its functional significance; Relationship of hypothalamus and adenohypophysis or neurohypophysis. Summary:

2. Anterior Pituitary Hormones HORMONETARGETFUNCTION Thyroid (TSH) Stimulating Thyroid glandTH synthesis & release Growth (GH)Many tissuesgrowth Adrenocortico - Tropin (ACTH) Adrenal cortex Cortisol release (androgens) Prolactin (Prl)BreastMilk production Follicle (FSH)GonadsEgg/sperm prod. Luteinizing (LH) GonadsSex hormones

sliver stain ， parafollicular cell

supraoptic nucleus paraventricular nucleus Neuroendocrine cell in supraoptic nucleus and paraventricular nucleus of the hypothalamus. The neurosecretory granules are transported axonally down to the pars nervosa. Granules often accumulate in the dilated portions of the axon’s terminals, which be Herring bodies

paraventricular-- antidiuretic hormone (ADH) increasing reabsorption of water in renal tubule and causing the constriction of arterioles to increase blood pressure. *Herring bodies: LM: acidophilic, irregular structure Supraoptic– Oxytocin ① promotes the contraction of the smooth muscle of the uterus during childbirth. ② Stimulates the release of milk from the breasts of lactating women through contraction of the myoepithelial cells.