Depart. Of Histology & Embryology

Why can you grow up?

General description ComponentsComponents Endocrine glands Endocrine tissues Endocrine cells FunctionFunction Endocrine system produce Hormones target organs Act on target cells Chemical messengers secreted by endocrine glands that transfer information and instructions from one set of cells to other cells. What is hormone ？

Endocrine glands Thyroid gland Adrenal glands Pituitary gland

General description ComponentsComponents Endocrine glands Endocrine tissues Endocrine cells FunctionFunction Endocrine system produce Hormones target organs Act on target cells What is hormone ？ Chemical messengers secreted by endocrine glands that transfer information and instructions from one set of cells to other cells.

Hormones secretion Special secreting forms  Autocrine  Paracrine

common features ⑴ Ductless ⑵ Endocrine cells arrange into nests, cords, clusters or follicles ⑶ Rich in capillaries

Two types of endocrine cells Nitrogenous-hormone secreting cell Steroid-hormone secreting cell

Thyroid gland General structureGeneral structure ---capsule : L.C.T --- capsule : L.C.T forming septa forming septa --- parenchyma: lobules lobules follicles follicles interstitium: CT interstitium: CT

Constitution: Follicle: Colloid is surrounded by a single layer epithelium. 1. Epithelium: Simple squamous (hypoactive), cuboidal or columnar (hyperactive), depending upon the functional status. Thyroid gland follicles 2. Colloid: Homogeneous secretion of epithelium. Acidophilic and PAS (+). Contains iodinated thyroglobulin.

Thyroid gland follicles Follicular epithelial cells EM: Follicular epithelial cells EM: microvilli microvilli RER, Golgi apparatus RER, Golgi apparatus secretory granules secretory granules lysosome, mitochondrion lysosome, mitochondrion endocytotic vesicles endocytotic vesiclesFunction: synthesize and release thyroid hormones thyroxine (T4) thyroxine (T4) triiodothyronine (T3) triiodothyronine (T3) According to the structures of follicular epithelial cells, can you illustrate their functions?

What is the secretory process? i. Synthesis of thyroglobulin ii. Iodination of thyroglobulin iii. Release of thyroid hormones

Formation of T3 & T4: a. AA→ RER→ thyroglobulin → (Gogi, glycosylated → (G, secreting granules) → colloid. b. Iodide → (iodide pump) → iodide oxidation in cytoplasm → colloid → bound to tyrosine residues of thyroglobulin → iodated thyroglobulin.

c. iodated thyroglobulin → (TSH, microvilli) → endocytic vesicles →LYS → T3 & T4. Function of T3, T4: a. elevate the basal metabolic rate. b. influence the body growth and nervous system development during fetal life. Modulation of T3, T4 secretion: hypothalamus-pituitary-thyroid axis

Pathological state hypothyroidism exophthalmic goiter In adults, thyroid hormone overproductionunderproduction myxoedema hyperthyroidism A consequence of an increase in body’s metabolism: Clinical features: ★ feeling hot ★ increased sweating ★ weight loss, with poximal muscle weakness muscle weakness ★ rapaid heart rate ★ anxiety and restless hyperactivity ★ diarrhoea Thyroid hormone deficiency slows body processes: Clinical features: Clinical features: ★ dry, puffy skin ★ dry, puffy skin ★ inability to keep warm ★ inability to keep warm ★ weight gain ★ weight gain ★ a slow heart rate ★ a slow heart rate ★ loss of energy and appetite ★ loss of energy and appetite ★ constipation ★ constipation

Pathological state Hypothyroidism present at birth: Mental retardation Mental retardation Short stature Short stature Coarse facial features Coarse facial features Protruding tongue Protruding tongue Umbilical hernia Umbilical hernia

Parafollicular cell ---single between follicular cells ---in small groups in interstitial tissue Also called calcitonin cell / C cell LM: ovoid, polygonal ovoid, polygonal larger larger pale-stained: eosinophilic pale-stained: eosinophilic argyrophilic granules argyrophilic granulesFunction: synthesize and release calcitonin, make blood calcium

Parathyroid gland Structure capsuleStructure capsule parenchyma parenchyma FunctionFunction synthesize parathyroid synthesize parathyroid hormone (PTH) hormone (PTH) make blood calcium make blood calcium glandular cells chief cells oxyphil cells stroma

---capsule: CT ---cortex: yellow, derived from mesoderm ---medulla: reddish- brown, derived from neural ectoderm Adrenal gland

Adrenal gland cortex Zona glomerulosa Zona fasciculata Zona reticularis Zona glomerulosa Zona fasciculata Zona reticularis

Zona glomerulosa 15% of cortex volume ---Structure:LM cells: small, low columnar cells: small, low columnar or polygonal or polygonal be arranged into nests or clusters nuclei: deep stained, round nuclei: deep stained, round cytoplasm: light basophilic cytoplasm: light basophilic---Function: secrete mineralocorticoid ( eg. aldosterone) regulate electrolyte homeostasis and water balance

Zona fasciculata About 78% of cortex volume ---Structure:LM cells : large ， clear margin be arranged in straight cords cytoplasm: light staining appear vacuolated(formy)-empty ---Function: secrete glucocorticosteroid (e.g cortisol 、 corticosterone) and androgen (less) regulate carbohydrate, protein and lipid metabolism influence immune response

Zona reticularis 7% of cortex volume ---Structure : LM cells: polyhedral and small; be arranged in irregular be arranged in irregular anastomosing cords cytoplasm: acidophilic ---Function: secret androgen(testosterone) and small amount of oestrogen

Adrenal medulla ---Structure: medullary cell ( chromaffin cell ) : LM: cells: polyhedral, be arranged in nests or short cords nests or short cords cytoplasm: weakly basophilic, brownish granules- when fixed by bichromate-containing fixative. central vein ganglial cells: multipolar neurons large, 2~3 in groups

Adrenal medulla EM electron-dense granules adrenaline cell: 80% noradrenaline cell: 20% Adr. cell Noradr. cell---Function: secrete adrenaline and noradrenaline secrete adrenaline and noradrenaline secrete some polypeptides(galanin, neuropeptide Y, enkephalin) secrete some polypeptides(galanin, neuropeptide Y, enkephalin) i. heart rate ii. dilate blood vessel i. blood pressure i. blood pressure ii. the flow speed of blood ii. the flow speed of blood

Pathological state Excessive adrenal secretion of glucocorticoid hormones Cushing’s syndrome

Pituitary gland pars nervosa infundibular stalk median eminence pars distalis pars intermedia pars tuberalis adenohypophysis neurohypophysis capsule: CT anterior lobe posterior lobe

Pituitary gland

Pars distalis Pars intermedia Pars nervosa Infundibular

Pas distalis Glandular cells are arranged in nests Rich in capillaries around the cells Classification: Chromophobes Chromophils Acidophils Basophils A --- Acidophil round or oval, eosinophilic stainning B --- Basophil less, large cell, ovoid or polygonal basophilic granules C --- Chromophobe more, small, pale, no clear boundary

Tropic hormones of pas distalis cell type secreting hormone acidophil basophil somatotrope somatotropic hormone(STH) or growth hormone(GH) mammotrope lactogenic hormone(LTH) or prolactin(PRL) thyrotrope gonadotrope adrenocorticotropic hormone(ACTH) Lipotropin or lipotrophic hormone(LPH) corticotrope follicle stimulating hormone(FSH) luteinizing hormone(LH) interstitial cell-stimulating hormone(ICSH)---male thyroid stimulating hormone(TSH)

Titan Jack Sprat Pathological state

Gigantism Dwarfism Pathological state growth hormone in kids too much deficient

Acromegaly Pathological state Too much growth hormone occurs in adults Protruding jaw Broaden lower face Enlarged hands

Pas intermedia Structure: chromophobe cells basophils be arranged into cords/follicles. Function: Secrete melanocyte-stimulating hormone (MSH) Pas tuberalis Secrete gonadotropin.

Neurohypophysis Pars nervosa Components Pituicytes ( glial cells)Pituicytes ( glial cells) Capillaries (fenestrated)Capillaries (fenestrated) Unmyelinated nerve fibersUnmyelinated nerve fibers Function: Store and release oxytocin and antidiuretic hormone (ADH)

Neurohypophysis Herring bodies: Neurosecretory granules accumulate in the dilated portions of the axons near their terminals. Neurosecretory granules accumulate in the dilated portions of the axons near their terminals. LM: acidophilic, irregular structure LM: acidophilic, irregular structure

Blood supply (Hypophyseal portal system) Superior hypophyseal artery (Primary plexus)capillaries Hypophyseal portal vein （ Secondary plexus ） capillaries Hypophyseal vein

Relationship between hypothalamus and adenohypophysis Arcuate nucleus of hypothalamus (neuroendocrine cell): secrete releasing hormones (RH) -GRH, PRH, TRH, GnRH, CRH, MSRH secrete release inhibiting hormones (RIH) -SOM, PIH, MSIH their axons end in infundibular stalk and release hormones into primary capillaries network of hypophyseal portal circulation positive and negative feedback