endocrine system dental

8/3/2019 Endocrine System Dental

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Endocrine system glands


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Endocrine System

Ductless Glands

Secret Hormones That Bind To Specific

Receptors on Plasmalemma (Cytoplasmic)Hormones Pass Via Blood To DistantTarget Cells.

Interact with CNS Autonomic That SecretNeurotransmitters.

Always Have Rich Blood Supply


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Endocrine Vs CNS

Endocrines

Hormones

Via Blood

Slow Response

Relatively continuous

AN. System

Neurotransmitters

Local Synapse NMJ

Rapid Response

AS Needed.


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Targetcells

Endocrinecells

NeuronNerve impulse

Neurotransmitter

Hormone inbloodstream

Endocrine System vs Autonomic Nervous

System


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Endocrine Organs Hypothalamus- neuroendocrine gland

Anterior pituitary gland- endocrine gland

Posterior pituitary gland- neuroendocrine gland

Thyroid gland- endocrine gland

Parathyroid glands- endocrine gland

Adrenal gland (cortex and medulla)- endocrine/neuroendocrine gland

Pancreatic islets- endocrine/exocrine gland

Gonads- Ovaries in females; Testes in males- endocrine/exocrine glands


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Hormones

Chemicals

Proteins/Polypeptides: Insulin, FSH.

Amino Acid Derivative: Thyroxine.

Steroids: Progesterone, Testosterone.

Binding of Hormone-Receptor Results inActivation of Signal Transduction Cascade.


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Hormones

Hormone-Receptor Complex Initiate

Phosphorylation Chain.

Second Messengers are Released As cAMP,

cGMP.

Feed Back Mechanism (Positive/Negative)

between Target Cells & Glands


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An intracellular

signaling cascade

Fig. 15-7, p. 487


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Three classes of cell-surface receptors (cont'd)

Fig. 15-12, p. 491


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Three classes of cell-surface receptors

Fig. 15-12 a&b, p. 491


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Types of Endocrine Glands

Three types of glands:1. Pure endocrine glandsthyroid, parathyroid,

adrenal cortex, thymus and pineal.

2. Endocrine/exocrine glandspancreas, ovaries and

testes

3. Neuroendocrine glandsadrenal medulla and

hypothalamus (supraoptic nuclei and

paraventricular nuclei) to posterior pituitary.


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Pituitary Gland (Hypophysis)

Measures 1.00-1.5 * 0.5 cm.

Weighs about 5 gm

Lies Below Hypothalamus & Attached to InferiorSurface of Brain by Infundibulum.

Located in Sella Turica of Sphenoid Bone &

Lined By Dura Matter CalledDiaphragma Sellae

Develop From Oral Ectoderm (Adenohypophysis

& Neural Ectoderm (Neurohypophysis)


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Pituitary Relations

Anteriorly: Sphenoid Sinus (Site Access of

Surgical Operations.

Posterior: Basilar Artery &Pons.

Superior: Diaphramma Sellae which

separates it from Optic Chiasma.

Inferior: Body of Sphenoid & Sinus.

Lateral: Cavernous Sinus & its Contents


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Function Pituitary Gland

Its Hormones RegulateGrowth, Metabolism &Reproduction.

Regulated By Signals ORHormones ofHypothalamus

Hypothalamus Monitorshormones level.

Hypothalamus is TheCNS Center of

Homeostasis.


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The Hypothalamus & Pituitary


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Parts of Pituitary Gland or Hypophysis

Location: Sits in the sella turcica of the sphenoid bone Attached to the hypothalamus by the infundibulum

Consists of two lobes:

1. Adenohypophysis

Releases 7 different hormones

Consists of 3 divisions: pars tuberalis, pars intermedia and pars

distalis (anterior lobe).

2. NeurohypophysisReleases 2 different hormones

Consists of 3 divisions: median eminence, infundibular stalk and

pars nervosa (posterior lobe)


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Pituitary gland

Adenohypophysis

Pars tuberalis

Pars intermedia

Pars distalis

Neurohypophysis

Median eminence

Infindibular stalkPars nervosa


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Pituitary Gland

2-Lobes:

a. Anterior

(Adenohypophysis)

b. Posterior

(Neurohypophysis)

Anterior

Posterior

Middle

Pituicyte

Nuclei


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Anterior Pituitary Hormones

There are seven anterior pituitary hormones:Thyroid stimulating hormone (TSH)*

Growth hormone (GH)

Adrenocorticotropic hormone (ACTH)*Melanocyte stimulating hormone (MSH)

Follicle stimulating hormone (FSH)*

Luteinizing hormone (LH) = ICSH in males*Prolactin (PRL)

* indicate trophic hormones


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Hypothalamic releasing hormones Release of anterior pituitary hormones is directed by specific

releasing hormones (factors) from the hypothalamic nuclei. All of these are polypeptide molecules.

TRHthyrotropin releasing hormone (TSH and PRL)

GHRHgrowth hormone releasing hormone (GH)

Somatostatininhibits release of growth hormone

CRHcorticotrophin releasing hormone (ACTH)

MRH- melanocyte releasing hormone (MSH)

MIF- inhibits release of MSH

GnRHgonadotropin releasing hormone (FSH/LH)

PRHprolactin releasing hormone (PRL)

PIHprolactin inhibiting hormone (dopamine)


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Anterior/Posterior Pituitary CirculationBlood flow to pituitary gland is via a portal circulation the

hypophyseal portal. Arterial flow is via superior and inferior

hypophyseal artery into capillary beds in series


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Posterior Pituitary HormonesADH an Oxytocin are secreted by neurosecretory cells in the

paraventricular and supraoptic nuclei of the hypothalamus and aretransported to posterior pituitary via hypothalamohypophyseal

tract.


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Neurohypophyseal Hormones Antidiuretic hormone (ADH)produced by supraoptic

nuclei in the hypothalamus.

Consists of 9 amino acids

Reduces the excretion of water by kidney collectingducts; increases cuddling and grooming behavior.

Oxytocinproduced by the paraventricular nuclei in the

hypothalamusConsists of 9 amino acids, but differs from ADH.

Induces smooth muscle contraction; increases cuddlingand grooming behavior.


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Pituitary Histology

Made of Cords of Cells.

Surrounded by

Fenestrated Sinusoids

Two Types of Cells Basedon Affinity to Dyes

Chromophils VsChromophobes.

Chromophils are majorType of Pars Distalis


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Anterior Pituitary

The anterior pituitary

is composed of the

stained-richchromophils and the

clear chromophobes.

Of the chromophils,

acidophils are red andbasophils are blue.

Ant.Post


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Types of Ant.Pituitary Cell

(Distalis) Acidiphils:

Sommatotrophs

Mammotrophs

Basophils:

Corticotrophs.

Thyrotrophs. Gonadotrophs


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Chromophobes

Have Scanty

Cytoplasm Hence No

Stain. Small Cells.

Maybe Degranulated

Chromophils


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Pars Intermedia/Zona Intermedia

Pars Intermedia/ZonaIntermedia

Lies Between Pars

Distalis & Pars Nervosa. Contain Cysts Remnant

of Rathks Pouch

Made of Cuboidal-Cell

Lined Cysts.


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Pars Intermedia/Zona Intermedia

Cells Stain Basophilic& Arranged In Cords.

SynthesizeMelanocyte-Stimulating Hormone.

Stimulate Melanin

Production. May Stimulate

Prolactin Secretion


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Hypthalamo-Hypophyseal

Tract

Unmylinated Axons of

Cells From Supraoptic &

Paraventricular Nuclei of

Hypothalamus EnterPosterior Pituitary &

Terminate Near

Capillaries

These Tracts Constitutethe Bulk of Post. Pituitary.


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Supraoptic & Paraventricular

Cells of Supraoptic &

Paraventricular SecretAnti-diuretic (ADH)

& Oxytocin

Hormones


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Pars Nervosa (Post. Pituitary)

This is Not A True Endocrine Gland But Continuation ofHypothalamohypophy-seal Tract.

Store Secretions of Their Cell-Bodies

Pituicytes are Glia-Like Cells That Support Those Axons. Pituicytes Occupy 25% of Pars Nervousa

Form Sheats Around Axons

Axons Contain Membrane-Bound Granules of ADH &

Oxytocin In Separate Axons. Chrome-Hematoxyline staining Show Blue Black

Distension in Axons Called Herring Bodies.

Are Non-Secretory Granules


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Pars Nervosa (Post. Pituitary)

Herring bodies (arrow) are

the dilated hypothalamic

nerve terminals from the

hypothalamus from whichthe posterior pituitary

actually releases ADH &

Oxytocin. ADH and

Oxytocin are releasedfrom different Herring

bodies reflecting their

separate cells of origin.


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Growth Hormone

Effects of Growth Horme:

Generalized Increase in Cellular Metabolic

Rate.

Induce Somatomedins leading To

Stimulation of Epiphyseal Growth Plate

Length Hence Bone Growth


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Clinical Applications

Pituitary Adenomas are common tumors. Extension of those tumors cause Pressure Effects on

neighboring structure as Optic Chiasma (visual fielddefects would be bitemporal hemianopia).

Tumors can grow up into the 3rd ventricle causinghydrocephalus.

Rapid lateral expansion, perhaps due to hemorrhagemay compress the 3rd, 4th & 6th cranial nerves.

Headache may be present from stretch of the meninges.Surgery to remove pituitary tumors is usuallyperformed through the sphenoidal sinus.

Diabetes Insipidus: ADH supression causing Polyurea

& Dehydration.

Th id Gl d


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Thyroid Gland

Two Lateral lobes connected by an Isthmus.

Each lobe is about 5 cm. long; its greatest width is

about 3 cm

Upper Limit at level offifth or sixth tracheal ring

Lower Limit at level ofjunction of the middle

with the lower third of the thyroid cartilage

It Weighs about 30 grams. It is slightly heavier in

the female, in whom it becomes enlarged during

menstruation and pregnancy.

Isthmus: second and third rings of the trachea


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Thyroid Gland

The only Gland That

Stores inactive

Secreted Hrmones. Secrets Tri-

iodothyronine-T3 &

Thryoxine-T4 &

Calcitonin


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Thyroid Histology

Functional Unit Called

Follicle

Contain HomogenousColloid.

Septi From Inner

Fibro-elastic Capsule

Divides it into Lobules


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Thyroid Follicles

Colloid material is

Thyrogobulin.

Follicles surroundedby Simple Cuboidal

Epithelium.

Active Follicles

Smaller & CuboidalCells Taller

Th id l d


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Thyroid gland


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Follicular Cells

Thyroglobulin synthesized in Follicular cells

Packed & Released into Lumen Via Apical

Plasma Membrane. Basal PM of Follicular cells has Sodium/Iodide

Pumps to import Plasma Iodide inside where its

levels is 20-40 Folds that of Plasma.

Basal PM of Follicular cells also has Receptors forTSH.


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Parafollicular Cells

Within Interfollicular

Spaces

Present As Individual or

in Clumps

Clear Cells.

Secret Calcitonin.

Regulate Serum Calcium

Levels.

Inhibits Rates of

Decalcification of Bones


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Parafollicular Cells

The C-cells secrete calcitoninwhich helps lower calciumlevels by inhibiting osteoclasticactivity of bone resorption .

These C-cells are actuallynamed for being "clear" (as inlighter staining). Notice thatthey are in the interstitium anddo not normally touch the

follicles


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Clinical Application

Levels of thyroxin affect Metabolic Rate.

If increased it increase CHO and Fatty

Acids Metabolism. Decrease Body Weight.

Increase Heart Rate, Respiration, Muscular

Activity leading to Fatigue & Tremors. Impotence in Males & Menstrual

Disturbances in Females.


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Parathyroid gland

Located On The Posterior Lateral Margins of the thyroidgland are 4 to 8 small nodules.

Structure is small ovoid nodules ~ 2-5 mm x 3-8 mm.

Produces Parathyroid Hormone (PTH) which helps

regulate blood Ca++ levels.

Target organs of PTH are Bone, Kidneys And Intestines.

Histologically it contains numerous small chief cells and

rare large oxyphilic cells.Chief cells secrete PTH.

Oxyphilic cells are probably inactive or immature chief cells.

P th id l d


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Parathyroid glands


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Parathyroid

Embedded Within

Thyroid Capsule.

Septi Divides it into

Lobules.

Has 2-Types of Cells:

Chief (Principal) Cells

&

Oxyphil Cells.


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Parathyroid

Oxyphil Cells:

Less in Number.

Larger in Size. Occur in Clumps.

Dense EosinophilicNuclei.

Number Increase withAge. No HormoneSecretion


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Parathyroid

Cell Arranged asstring-likearrangement of the

parathyroid cells onthe right. The large,clear cells to the leftare oxyphil cells They

are found only inhumans and increasewith age.


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Pancreas

Elongated StructureLies in the Epigastric& Left Hypochondriac

Regions. Retroperitoneal on

Posterior AbdominalWall & CrossesTranspyloric Plane.

Has: Head, Body &Tail


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Pancreas

Both Exocrine (EnzymesHydrolyze Fats, Proteins& CHO)

& Endocrine GlandIslets of LangerhansProduce Insulin &Glucagon HormonesBoth Regulate CHO

Metabolism.


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Pancreas

Pancreas stained

with H&E, serves

both endocrine and

exocrine functions.

The round islets of

Langerhans are the

endocrine portionand serve to identify

pancreatic tissue.


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Pancreas

Islets are distinguished from thesurrounding exocrine tissue by:

a continuous CT capsule and an

extensive microvascular in the

center of the islet. Center is rich in B or beta

(insulin) cells

Periphery where most of the A

or alpha (glucagon) cells arelocated. Within the islet, the

glucagon-secreting alpha cells

stain red while the insulin-

secreting beta cellsstain blue.


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Adrernal Glands

2-Retroperitoneal Glands.Rt one Lies on Upper Poleof Rt-Kidneys, Left oneAlong upper medial border

of Left Kidney. Renal Fascia Surrounds

Them.

Perirenal Fat Separatesthem From Kidney.

Rt. Gland Pyramidal inShape

Lt. Gland is Crescent inShape.


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Adrenals

Adrenal Cortex

Same Origin AsGonads SecretsSteroid Hormones;Mineralocorticoids,Glucuocorticoids &Sex Hormones.

Regulated By PituitaryTrophic HormoneACTH

Adrenal Medulla

Same Origin asSymathetic NervousSystem (SNS)

SecretsCatecholamine;Adrenalin &Noradrenaline

Regulated By SNS


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Adrenals

A Capsulated Organ

Main 2-Layers:

Outer Dense Cortex

&

Inner Pale Medulla


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Layers of AdrenalCortex:

1. Zona Glomerulosa:Cells Arranged inIrregular ClumpsSeparated by Trabeculae

Zona Fasciculata:Widest Layer, CellsArranged in Cords.

Zona Reticularis:Thinner Inner Most,Cells in IrregularBranching Cords

ZG

ZF

ZR


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Adrenal

Zona Glomerulosa: Cells;Round Strongly Stained Nuclei.

Very Little Cytoplasm.

Secrets Mainly Adosterone

Zona Fasciculata: One Cell Thick Cords.

Large Cells & Abundant Poorly

Stained Cytoplasm

Secrets Glucocorticoids MainlyCortisol


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Adrenals

Zona Reticularis

Branching Irregular

Cords of Cells. Cells Smaller & Stain

Strongly.

Secrets Very Little

Androgen &

Glucocorticoids


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Adrenal Medulla

Composed ofClosely Packed Basophilic

Secretory Cells.

Supported By Collagenous CT ContainingNumerous Fenestrated Sinusoids.

Many Venous Channels Draining into

Central Medullary Vein

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