Endocrine 1

EndocrineEndocrine

Jim PierceJim PierceBi 145bBi 145bLecture 10, 2009-10Lecture 10, 2009-10

Endocrine SystemEndocrine System

The endocrine system is concerned with “internal secretions”

“endo-” “-crine”

What makes up the endocrine system?(Actually… quite a difficult question)


Distance of Hormone ActionAutocrineParacrineEndocrine

We typically leave out “local” hormonesThe grey area occurs because no hormone is purely local.


The classic members:Hypothalamus and Pituitary GlandPineal GlandEndocrine PancreasThyroidParathyroidsAdrenalsGonads


The “classic members” are useful for learningThey are importantThey provide order to learningThey introduce key concepts (hormonal axis)

Remember that it is an artificial “system”Organ Hormones (GI, Cardiac, Pulmonary)Cytokines (Immune Hormones)Orphan Endocrine Cells

Endocrine Key ConceptsEndocrine Key Concepts

Key Concept One:

For each hormone, what is the target celland its receptor?

Single or Multiple Target CellsSingle or Multiple Receptors


Key Concept Two:

What is the site of hormone release and its pathway to target tissue?

Focal: Hypothalamus PituitaryGlobal: Thyroid Hormone Body


Key Concept Three:

What effects do secretion, excretion, and degradation have on hormone levels?

Steady State Disequilibrium


Key Concept Four:

What computational structures exist to control and regulate hormonal levels?

AXISOther Control Structures


Axis:

A linear control structureconsisting of a seriesof cells each secretingone hormone tostimulate thesubsequent cell.


Examples of Axes:

Hypothalamic – Pituitary – AdrenalHypothalamic – Pituitary – ThyroidHypothalamic – Fat axisRenin – Angiotensin – Aldosterone


Key Concept Five:

What other hormones act on similar targets with similar effects?

RedundancyMultiplicity


Key Concept Six:

How do these different hormones affectbody metabolism?

Free Body Diagram


It’s important to keep these ideas in mind when thinking about the endocrine system

Endocrine PancreasEndocrine Pancreas

The majority of the pancreasis a secretory exocrine gland

A minority of the pancreas isan secretory endocrine gland

These collections of endocrine cellsare called the Islets of Langerhans


Endocrine PancreasEndocrine PancreasIslets contain:

Alpha Cells - Glucagon (15-20%)Beta Cells - Insulin (65-80%)Delta Cells - Somatostatin (3-10%)PP Cells - Pancreatic Polypeptide (< 1%)

Epsilon Cells – Ghrelin? (<0.5%)

Alpha Cells - GlucagonAlpha Cells - Glucagon

Beta Cells - InsulinBeta Cells - Insulin

Delta Cells - SomatostatinDelta Cells - Somatostatin


HypothalamusHypothalamus

Anatomy and Microanatomy

Lives in theDiencephalon

Inferomedialto Thalamus




Hypothalamic Nuclei


Thyrotropin-releasing hormone (TRH) Gonadotropin-releasing hormone (GnRH)Growth hormone-releasing hormone (GHRH)Corticotropin-releasing hormone (CRH)Somatostatin Dopamine

Pitutary GlandPitutary Gland


Lives in theSkull Basein its own compartment

Sella Turcica

Pituitary GlandPituitary Gland

Sella Turcica (Turkish Saddle)Located in Sphenoid Bone


Gross View

Posterior Anterior


The “gland” consists of two grossly identifiable parts

Anterior PituitaryPosterior Pituitary


Microscopically,there are manymore parts

The functionaldivision betweenanterior andposterior stays true.

Posterior Anterior


Posterior PituitaryHas Neurons

Cell Bodies are inhypothalamus

Synapses withBlood Vessels


Anterior PituitaryHas “Endocrine” Cells

Looks and Actslike a Gland

Not Innervated


The pituitary “hangs” offthe hypothalamus

Blood Supply is in three steps

Arterial supply arrivesat the hypothalamusvia the Circle of Willis


Next, the venous drainage from the Hypothalamus goesto the Pituitary

This is called the“Portal System”

Just like in the gut and liver


After passing through thePortal System and carryinghypothalamic hormones to the pituitary

The venous blood, carryingpituitary hormones, returnsto the systemic veins


Just like the portal systemof the gut gives the liverfirst crack at “gut absorbed” stuff

This portal system gives thepituitary first crack at secretedhypothalamic hormones


Hypothalamus and Pituitary GlandHypothalamus and Pituitary Gland

Together, they compare and contrast theclassic endocrine and neuroendocrine systems

Neuroendocrine System: Nerves release Neurotransmitters into blood

Endocrine System:Hormones from one part of the body go to another

Posterior PituitaryPosterior Pituitary

Cell Bodies in HypothalamusSupraoptic and Paraventricular Nuclei

Axons in thePars tuberalis

“Synapse” in thePars nervosa

Posterior PituitaryPosterior Pituitary

Histologically, it’s not that interesting(Looks like nerves)

Anterior PituitaryAnterior Pituitary

Cell Bodies look like “Glands”


Depending on the stain

Some cells like stain:Chromophils

AcidophilsBasophilsNeutrophils

Some cells don’t:Chromophobes


Why stain differently?

Each Cell producesone and only onehormone.

Different hormone peptides have differentchemical properties

Pituitary DevelopmentPituitary Development

The two regions of pituitary have separate originsAnterior = EndodermPosterior = Neuroectoderm



Anterior lobe (adenohypophysis) GH Growth hormonePRL Prolactin ACTH Adrenocorticotropic hormoneTSH Thyroid-stimulating hormone FSH Follicle-stimulating hormone LH Luteinizing hormone


Posterior lobe (neurohypophysis) Oxytocin Antidiuretic hormone (ADH)

Pineal GlandPineal Gland

Pineal gland

Early Chordateshistologically resembles eye

Hypothesized toregulate day-nightcycles


Located betweensuperior colliculi

In Humans8 mm in size


Located insideMeninges

Very Vascular


Secretes Melatonin

Thyroid GlandThyroid Gland

Lives inthe Neck

Derivedfrom theBranchialArches


Consists of LobesRight and LeftIsthmusPyramidal


Foramen Cecum inside the mouthdevelops into a small diverticulum

This is draggedtowards the chestduring body folding


Foramen Cecum lies medial to 1st and 2nd arches


Branchial ArchesBranchial Arches

Foramen Cecumbecomes Thyroid

Third and Fourth Archesbecome Parathyroids

Third Archbecomes Thymus


Pyramidal Lobeis the “remnant”

Right and LeftLobes are the“main gland”


Heavily Vascular(Like most glands)

Arterial Supplyand Venous Drainage fromBranchial Arches


The gland consistsof Thyroid Follicles

Cuboidal EpitheliumCentral ColloidSupportive StromaParafollicular Cells


Thyroid HormoneThyroxine (T4)Triiodothyronine (T3)

C-CellsCalcitonin

ParathyroidsParathyroids

Aptly named glands that live around thyroid:

Branchial ArchesBranchial Arches

Foramen Cecumbecomes Thyroid

Third and Fourth Archesbecome Parathyroids

Third Archbecomes Thymus

Parathyroid GlandParathyroid Gland

ParathyroidParathyroid

SecretesParathyroidhormone (PTH)

Adrenal GlandsAdrenal Glands

These are pairedsuprarenal glands

Embryologically:Cortex forms first

Gonadal RidgeMedulla forms second

Neural Crest Origin


Histologically,

It’s quite easyto see thedifferencebetweenCORTEX andMEDULLA


Adrenal CortexAdrenal Cortex

This should remind you of the kidney

Adrenal MedullaAdrenal Medulla


Adrenal cortexGlucocorticoids - cortisol Mineralocorticoids - aldosterone Androgens (including testosterone)

Adrenal medulla EpinephrineNorepinephrine

GonadsGonads

We’ll save these for Reproduction Endocrinology

Orphan Endocrine CellsOrphan Endocrine Cells

APUD Cells

Amine Precursor Uptake and DecarboxylationA P U D

Generate tissue and organ levels of“Traditional Neurotransmitters”

Orphan Endocrine GlandsOrphan Endocrine Glands

Heart Atrial-natriuretic peptide (ANP)

Stomach and intestines Gastrin Somatostatin Secretin Cholecystokinin (CCK) Neuropeptide Y

Liver Insulin-like growth factor Angiotensinogen Thrombopoietin

Orphan Endocrine GlandsOrphan Endocrine Glands

Kidney Renin Erythropoietin (EPO) Calcitriol

Skin Calciferol (vitamin D3)

Adipose tissue Leptin

Questions?Questions?

Endocrine 1

Health & Medicine

endocrine key concepts

collections of endocrine

endocrine pancreas islets

secretory endocrine

key concepts hormonal

endocrine jim pierce

series of cells

multiple target cells