Depart. Of Histology & EmbryologyDepart. Of Histology & EmbryologyDepart. Of Histology & EmbryologyDepart. Of Histology & Embryology

Why can you grow

up?

General description• ComponentsComponents

Endocrine glands Endocrine glands Endocrine tissues Endocrine tissues Endocrine cellsEndocrine cells

• FunctionFunction

Endocrine systemEndocrine systemproduce HormonesHormones

target organstarget organs

Act on

target cellstarget 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 glands Endocrine tissues Endocrine tissues Endocrine cellsEndocrine cells

• FunctionFunction

Endocrine systemEndocrine systemproduce HormonesHormones

target organstarget organs

Act on

target cellstarget 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 formsSpecial secreting forms

AutocrineAutocrine

ParacrineParacrine

common features

⑴ ⑴ DuctDuctlessless

⑵ ⑵ Endocrine cells arrange into nests, cords, clusters or folliclesEndocrine cells arrange into nests, cords, clusters or follicles

⑶ ⑶ RichRich in capillaries 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 septaforming septa

--- parenchyma: --- parenchyma:

lobuleslobules

follicles follicles

interstitium: CTinterstitium: CT

Constitution: 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 Follicular epithelial cells EM:EM:

• microvillimicrovilli

• RER, Golgi apparatus RER, Golgi apparatus

secretory granulessecretory granules

• lysosome, mitochondrionlysosome, mitochondrion

endocytotic vesiclesendocytotic vesicles

Function:Function: synthesize and release thyroid hormonessynthesize and release thyroid hormones

thyroxine (T4)thyroxine (T4)

triiodothyronine (T3)triiodothyronine (T3)

According to the structures of follicular epithelial cells, According to the structures of follicular epithelial cells, can you illustrate their functions?can you illustrate their functions?

What is the secretory process?

i.   i.   SynthesisSynthesis of thyroglobulin of thyroglobulin

ii.  ii.  Iodination Iodination of thyroglobulinof thyroglobulin

iii. iii. ReleaseRelease of thyroid hormones 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: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:Modulation of T3, T4 secretion:

hypothalamus-pituitary-thyroid axis

Pathological state

hypothyroidismhypothyroidism

exophthalmic goiter

In adults, thyroid hormone overproduction underproduction

myxoedema

hyperthyroidism

hyperthyroidism

A consequence of an increase in A consequence of an increase in

body’s metabolism:body’s metabolism:

Clinical features:Clinical features:

★ ★ feeling hotfeeling hot

★ ★ increased sweatingincreased sweating

★ ★ weight loss, with poximal weight loss, with poximal

muscle weaknessmuscle weakness

★ ★ rapaid heart raterapaid heart rate

★ ★ anxiety and restlessanxiety and restless hyperactivityhyperactivity

★ ★ diarrhoeadiarrhoea

Thyroid hormone deficiency slows Thyroid hormone deficiency slows

body processes:body processes:

Clinical features:Clinical features:

★ ★ dry, puffy skindry, puffy skin

★ ★ inability to keep warminability to keep warm ★ ★ weight gainweight gain

★ ★ a slow heart ratea slow heart rate

★ ★ loss of energy and appetiteloss of energy and appetite ★ ★ constipationconstipation

Pathological state

Hypothyroidism present at birth:Hypothyroidism present at birth: Mental retardation Mental retardation Short statureShort stature Coarse facial featuresCoarse facial features Protruding tongueProtruding tongue Umbilical herniaUmbilical hernia

Parafollicular cell------single between follicular cellssingle between follicular cells---in small groups in interstitial tissue---in small groups in interstitial tissueAlso calledAlso called calcitonin cell / C cell calcitonin cell / C cell

LM:LM:

• ovoid, polygonalovoid, polygonal

• largerlarger

• pale-stained: eosinophilicpale-stained: eosinophilic

• argyrophilic granulesargyrophilic granules

Function:Function:

synthesize and release synthesize and release calcitonin, calcitonin, make blood calcium make blood calcium

Parathyroid gland

• Structure Structure capsulecapsule parenchyma parenchyma

• FunctionFunction

synthesize parathyroid synthesize parathyroid

hormone (PTH)hormone (PTH)

make blood calcium make blood calcium

glandular cellsglandular cells chief cellschief cells

oxyphil cellsoxyphil cellsstromastroma

------capsule:capsule: CT CT

------cortex:cortex: yellow, yellow,

derived from derived from mesodermmesoderm

------medulla:medulla: reddish- reddish-

brown, derived from brown, derived from

neural ectodermneural ectoderm

Adrenal gland

Adrenal gland cortex

Zona glomerulosaZona glomerulosa

Zona fasciculataZona fasciculata

Zona reticularisZona reticularis

Zona glomerulosa

Zona fasciculata

Zona reticularis

Zona glomerulosa15% of cortex volume15% of cortex volume

---Structure: ---Structure:

LMLM

cellscells: small, low columnar: small, low columnar

or polygonal or polygonal

be arranged into nests or clustersbe arranged into nests or clusters

nucleinuclei: deep stained, round: deep stained, round

cytoplasmcytoplasm: light basophilic: light basophilic

---Function: ---Function:

secrete secrete mineralomineralocorticoid corticoid ( eg. aldo( eg. aldosteronesterone))

regulate electrolyte homeostasis and water balanceregulate electrolyte homeostasis and water balance

Zona fasciculataAbout 78% of cortex volumeAbout 78% of cortex volume

---Structure:---Structure:

LMLM

cells cells : large: large ，， clear margin clear margin

be arranged in straight cordsbe arranged in straight cords

cytoplasmcytoplasm: light staining: light staining

appear vacuolated(formy)-emptyappear vacuolated(formy)-empty

---Function:---Function:

secrete secrete glucoglucocorticosteroidcorticosteroid

(e.g cortisol(e.g cortisol 、、 corticosterone) and corticosterone) and androgenandrogen (less) (less)

regulate carbohydrate, protein and lipid metabolismregulate carbohydrate, protein and lipid metabolism

influence immune responseinfluence immune response

Zona reticularis

7% of cortex volume7% of cortex volume

---Structure---Structure::

LMLM

cellscells: polyhedral and small; : polyhedral and small;

be arranged in irregular be arranged in irregular

anastomosing cords anastomosing cords

cytoplasmcytoplasm: acidophilic: acidophilic

---Function:---Function:

secret secret androgenandrogen(testosterone) and(testosterone) and

small amount of small amount of oestrogenoestrogen

Adrenal medulla

---Structure:---Structure:

medullary cell ( chromaffin cell ) : medullary cell ( chromaffin cell ) :

LM:LM:

cellscells: polyhedral, be arranged in : polyhedral, be arranged in

nests or short cordsnests or short cords

cytoplasmcytoplasm: weakly basophilic,: weakly basophilic,

brownish granules- when fixed bybrownish granules- when fixed by

bichromate-containing fixative.bichromate-containing fixative.central veincentral vein

ganglial cellsganglial cells: multipolar neurons: multipolar neurons

large, 2large, 2~~3 in groups3 in groups

Adrenal medullaEMEM

electron-dense granules electron-dense granules

adrenaline celladrenaline cell: 80%: 80%

nornoradrenaline celladrenaline cell: 20%: 20%

Adr. cell

Noradr. cell

---Function: ---Function:

secrete adrenaline and secrete adrenaline and nornoradrenalineadrenaline

secrete some polypeptides(galanin, neuropeptide Y, enkephalin)secrete some polypeptides(galanin, neuropeptide Y, enkephalin)

i.  heart ratei.  heart rateii. dilate blood vesselii. dilate blood vessel

i.  blood pressurei.  blood pressure ii. the flow speed of bloodii. the flow speed of blood

Pathological state

Excessive adrenal secretion of Excessive adrenal secretion of glucoglucocorticoid hormonescorticoid hormones

Cushing’s syndromeCushing’s syndrome

Pituitary gland

pars nervosapars nervosa

infundibular stalkinfundibular stalk

median eminencemedian eminence

pars distalis pars distalis

pars intermedia pars intermedia

pars tuberalispars tuberalis

adenohypophysis

neurohypophysis

capsule: CTcapsule: CTanterior lobe

posterior lobe

Pituitary gland

Pituitary gland

Pars distalisPars intermedia

Pars nervosa

Infundibular

Pas distalis

Glandular cells are arranged in nests Glandular cells are arranged in nests

Rich in capillaries around the cellsRich in capillaries around the cells

Classification:

ChromoChromophobephobess

ChromoChromophilphilss Acidophils

Basophils

A --- AcidophilA --- Acidophilround or oval , eosinophilic stainninground or oval , eosinophilic stainningB --- BasophilB --- Basophilless, large cell, ovoid or polygonalless, large cell, ovoid or polygonalbasophilic granulesbasophilic granulesC --- ChromophobeC --- Chromophobemore, small, pale, no clear boundarymore, small, pale, no clear boundary

Tropic hormones of pas distalis

cell type secreting hormone cell type secreting hormone

acidophil acidophil

basophil 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 stategrowth hormone in kidsgrowth hormone in kids

too muchtoo muchdeficientdeficient

Acromegaly

Pathological stateToo much growth hormone occurs in adultsToo much growth hormone occurs in adults

Protruding jawProtruding jawBroaden lower faceBroaden lower faceEnlarged handsEnlarged hands

Pas intermediaStructure:Structure:

chromophobe cellschromophobe cells

basophilsbasophils

be arranged into cords/follicles.be arranged into cords/follicles.

Function:Function:

Secrete melanocyte-stimulatingSecrete melanocyte-stimulating

hormone (MSH)hormone (MSH)

Pas tuberalis

Secrete gonadotropin.

Neurohypophysis

Pars nervosaPars nervosa

ComponentsComponents

• Pituicytes ( glial cells)Pituicytes ( glial cells)

• Capillaries (fenestrated)Capillaries (fenestrated)

• UnUnmyelinated nerve fibersmyelinated nerve fibers

Function:Function:

Store and release Store and release oxytocinoxytocin and and antidiuretic hormone (ADH)antidiuretic hormone (ADH)

Neurohypophysis

Herring bodies:Herring bodies:

Neurosecretory granules accumulate in the dilated portions of Neurosecretory granules accumulate in the dilated portions of

the axons near their terminals.the axons near their terminals.

LM:LM: acidophilic, irregular structure 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