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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)
Endocrine SystemEndocrine System
Distance of Hormone ActionAutocrineParacrineEndocrine
We typically leave out “local” hormonesThe grey area occurs because no hormone is purely local.
Endocrine SystemEndocrine System
The classic members:Hypothalamus and Pituitary GlandPineal GlandEndocrine PancreasThyroidParathyroidsAdrenalsGonads
Endocrine SystemEndocrine System
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
Endocrine Key ConceptsEndocrine Key Concepts
Key Concept Two:
What is the site of hormone release and its pathway to target tissue?
Focal: Hypothalamus PituitaryGlobal: Thyroid Hormone Body
Endocrine Key ConceptsEndocrine Key Concepts
Key Concept Three:
What effects do secretion, excretion, and degradation have on hormone levels?
Steady State Disequilibrium
Endocrine Key ConceptsEndocrine Key Concepts
Key Concept Four:
What computational structures exist to control and regulate hormonal levels?
AXISOther Control Structures
Endocrine Key ConceptsEndocrine Key Concepts
Axis:
A linear control structureconsisting of a seriesof cells each secretingone hormone tostimulate thesubsequent cell.
Endocrine Key ConceptsEndocrine Key Concepts
Examples of Axes:
Hypothalamic – Pituitary – AdrenalHypothalamic – Pituitary – ThyroidHypothalamic – Fat axisRenin – Angiotensin – Aldosterone
Endocrine Key ConceptsEndocrine Key Concepts
Key Concept Five:
What other hormones act on similar targets with similar effects?
RedundancyMultiplicity
Endocrine Key ConceptsEndocrine Key Concepts
Key Concept Six:
How do these different hormones affectbody metabolism?
Free Body Diagram
Endocrine Key ConceptsEndocrine Key Concepts
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 Pancreas
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
Endocrine PancreasEndocrine Pancreas
HypothalamusHypothalamus
Anatomy and Microanatomy
Lives in theDiencephalon
Inferomedialto Thalamus
HypothalamusHypothalamus
Anatomy and Microanatomy
HypothalamusHypothalamus
Hypothalamic Nuclei
HypothalamusHypothalamus
Thyrotropin-releasing hormone (TRH) Gonadotropin-releasing hormone (GnRH)Growth hormone-releasing hormone (GHRH)Corticotropin-releasing hormone (CRH)Somatostatin Dopamine
Pitutary GlandPitutary Gland
Anatomy and Microanatomy
Lives in theSkull Basein its own compartment
Sella Turcica
Pituitary GlandPituitary Gland
Sella Turcica (Turkish Saddle)Located in Sphenoid Bone
Pituitary GlandPituitary Gland
Gross View
Posterior Anterior
Pituitary GlandPituitary Gland
The “gland” consists of two grossly identifiable parts
Anterior PituitaryPosterior Pituitary
Pituitary GlandPituitary Gland
Microscopically,there are manymore parts
The functionaldivision betweenanterior andposterior stays true.
Posterior Anterior
Pituitary GlandPituitary Gland
Posterior PituitaryHas Neurons
Cell Bodies are inhypothalamus
Synapses withBlood Vessels
Pituitary GlandPituitary Gland
Anterior PituitaryHas “Endocrine” Cells
Looks and Actslike a Gland
Not Innervated
Pituitary GlandPituitary Gland
The pituitary “hangs” offthe hypothalamus
Blood Supply is in three steps
Arterial supply arrivesat the hypothalamusvia the Circle of Willis
Pituitary GlandPituitary Gland
Next, the venous drainage from the Hypothalamus goesto the Pituitary
This is called the“Portal System”
Just like in the gut and liver
Pituitary GlandPituitary Gland
After passing through thePortal System and carryinghypothalamic hormones to the pituitary
The venous blood, carryingpituitary hormones, returnsto the systemic veins
Pituitary GlandPituitary Gland
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
Pituitary GlandPituitary Gland
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”
Anterior PituitaryAnterior Pituitary
Depending on the stain
Some cells like stain:Chromophils
AcidophilsBasophilsNeutrophils
Some cells don’t:Chromophobes
Anterior PituitaryAnterior Pituitary
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
Pituitary GlandPituitary Gland
Pituitary GlandPituitary Gland
Anterior lobe (adenohypophysis) GH Growth hormonePRL Prolactin ACTH Adrenocorticotropic hormoneTSH Thyroid-stimulating hormone FSH Follicle-stimulating hormone LH Luteinizing hormone
Pituitary GlandPituitary Gland
Posterior lobe (neurohypophysis) Oxytocin Antidiuretic hormone (ADH)
Pineal GlandPineal Gland
Pineal gland
Early Chordateshistologically resembles eye
Hypothesized toregulate day-nightcycles
Pineal GlandPineal Gland
Located betweensuperior colliculi
In Humans8 mm in size
Pineal GlandPineal Gland
Located insideMeninges
Very Vascular
Pineal GlandPineal Gland
Secretes Melatonin
Thyroid GlandThyroid Gland
Lives inthe Neck
Derivedfrom theBranchialArches
Thyroid GlandThyroid Gland
Consists of LobesRight and LeftIsthmusPyramidal
Thyroid GlandThyroid Gland
Foramen Cecum inside the mouthdevelops into a small diverticulum
This is draggedtowards the chestduring body folding
Thyroid GlandThyroid Gland
Foramen Cecum lies medial to 1st and 2nd arches
Thyroid GlandThyroid Gland
Branchial ArchesBranchial Arches
Foramen Cecumbecomes Thyroid
Third and Fourth Archesbecome Parathyroids
Third Archbecomes Thymus
Thyroid GlandThyroid Gland
Pyramidal Lobeis the “remnant”
Right and LeftLobes are the“main gland”
Thyroid GlandThyroid Gland
Heavily Vascular(Like most glands)
Arterial Supplyand Venous Drainage fromBranchial Arches
Thyroid GlandThyroid Gland
The gland consistsof Thyroid Follicles
Cuboidal EpitheliumCentral ColloidSupportive StromaParafollicular Cells
Thyroid GlandThyroid Gland
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
Adrenal GlandsAdrenal Glands
Histologically,
It’s quite easyto see thedifferencebetweenCORTEX andMEDULLA
Adrenal GlandsAdrenal Glands
Adrenal CortexAdrenal Cortex
This should remind you of the kidney
Adrenal MedullaAdrenal Medulla
Adrenal GlandsAdrenal Glands
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?