Endocrine

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Endocrine

• Jim Pierce
• Bi 145b
• Lecture 11, 2008-9

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Endocrine System

• The endocrine system is concerned with internal
  secretions
• endo- -crine
• What makes up the endocrine system?
• (Actually quite a difficult question)

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Endocrine System

• Distance of Hormone Action
• Autocrine
• Paracrine
• Endocrine
• We typically leave out local hormones
• The grey area occurs because no hormone is
  purely local.

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Endocrine System

• The classic members
• Hypothalamus and Pituitary Gland
• Pineal Gland
• Endocrine Pancreas
• Thyroid
• Parathyroids
• Adrenals
• Gonads

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Endocrine System

• The classic members are useful for learning
• They are important
• They provide order to learning
• They introduce key concepts (hormonal axis)
• Remember that it is an artificial system
• Organ Hormones (GI, Cardiac, Pulmonary)
• Cytokines (Immune Hormones)
• Orphan Endocrine Cells

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Endocrine Key Concepts

• Key Concept One
• For each hormone, what is the target celland its
  receptor?
• Single or Multiple Target Cells
• Single or Multiple Receptors

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Endocrine Key Concepts

• Key Concept Two
• What is the site of hormone release and its
  pathway to target tissue?
• Focal Hypothalamus ? Pituitary
• Global Thyroid Hormone ? Body

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Endocrine Key Concepts

• Key Concept Three
• What effects do secretion, excretion, and
  degradation have on hormone levels?
• Steady State Disequilibrium

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Endocrine Key Concepts

• Key Concept Four
• What computational structures exist to control
  and regulate hormonal levels?
• AXIS
• Other Control Structures

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Endocrine Key Concepts

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

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Endocrine Key Concepts

• Examples of Axes
• Hypothalamic Pituitary Adrenal
• Hypothalamic Pituitary Thyroid
• Hypothalamic Fat axis
• Renin Angiotensin Aldosterone

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Endocrine Key Concepts

• Key Concept Five
• What other hormones act on similar targets with
  similar effects?
• Redundancy
• Multiplicity

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Endocrine Key Concepts

• Key Concept Six
• How do these different hormones affectbody
  metabolism?
• Free Body Diagram

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Endocrine Key Concepts

• Its important to keep these ideas in mind when
  thinking about the endocrine system

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Endocrine 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

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Endocrine Pancreas
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Endocrine Pancreas

• Islets contain
• Alpha Cells - Glucagon (15-20)
• Beta Cells - Insulin (65-80)
• Delta Cells - Somatostatin (3-10)
• PP Cells - Pancreatic Polypeptide (lt 1)
• Epsilon Cells Ghrelin? (lt0.5)

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Alpha Cells - Glucagon
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Beta Cells - Insulin
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Delta Cells - Somatostatin
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Endocrine Pancreas
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Hypothalamus

• Anatomy and Microanatomy
• Lives in theDiencephalon
• Inferomedialto Thalamus

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Hypothalamus

• Anatomy and Microanatomy

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Hypothalamus

• Hypothalamic Nuclei

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Hypothalamus

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

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Pitutary Gland

• Anatomy and Microanatomy
• Lives in theSkull Basein its own compartment
• Sella Turcica

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Pituitary Gland

• Sella Turcica (Turkish Saddle)
• Located in Sphenoid Bone

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Pituitary Gland

• Gross View

Posterior
Anterior
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Pituitary Gland

• The gland consists of two grossly
  identifiable parts
• Anterior Pituitary
• Posterior Pituitary

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Pituitary Gland

• Microscopically,there are manymore parts
• The functionaldivision betweenanterior
  andposterior stays true.

Posterior
Anterior
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Pituitary Gland

• Posterior Pituitary
• Has Neurons
• Cell Bodies are inhypothalamus
• Synapses withBlood Vessels

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Pituitary Gland

• Anterior Pituitary
• Has Endocrine Cells
• Looks and Actslike a Gland
• Not Innervated

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Pituitary Gland

• The pituitary hangs offthe hypothalamus
• Blood Supply is in three steps
• Arterial supply arrivesat the hypothalamusvia
  the Circle of Willis

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Pituitary Gland

• Next, the venous drainage from the Hypothalamus
  goesto the Pituitary
• This is called thePortal System
• Just like in the gut and liver

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Pituitary Gland

• After passing through thePortal System and
  carryinghypothalamic hormones to the pituitary
• The venous blood, carryingpituitary hormones,
  returnsto the systemic veins

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Pituitary 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

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Pituitary Gland
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Hypothalamus and Pituitary Gland

• Together, they compare and contrast theclassic
  endocrine and neuroendocrine systems
• Neuroendocrine System Nerves release
  Neurotransmitters into blood
• Endocrine SystemHormones from one part of the
  body go to another

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Posterior Pituitary

• Cell Bodies in Hypothalamus
• Supraoptic and Paraventricular Nuclei
• Axons in thePars tuberalis
• Synapse in thePars nervosa

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Posterior Pituitary

• Histologically, its not that interesting
• (Looks like nerves)

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Anterior Pituitary

• Cell Bodies look like Glands

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Anterior Pituitary

• Depending on the stain
• Some cells like stainChromophils
• Acidophils
• Basophils
• Neutrophils
• Some cells dontChromophobes

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Anterior Pituitary

• Why stain differently?
• Each Cell producesone and only onehormone.
• Different hormone peptides have
  differentchemical properties

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Pituitary Development

• The two regions of pituitary have separate
  origins
• Anterior Endoderm
• Posterior Neuroectoderm

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Pituitary Gland
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Pituitary Gland

• Anterior lobe (adenohypophysis)
• GH Growth hormone
• PRL Prolactin
• ACTH Adrenocorticotropic hormone
• TSH Thyroid-stimulating hormone
• FSH Follicle-stimulating hormone
• LH Luteinizing hormone

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Pituitary Gland

• Posterior lobe (neurohypophysis)
• Oxytocin
• Antidiuretic hormone (ADH)

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Pineal Gland

• Pineal gland
• Early Chordateshistologically resembles eye
• Hypothesized toregulate day-nightcycles

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Pineal Gland

• Located betweensuperior colliculi
• In Humans8 mm in size

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Pineal Gland

• Located insideMeninges
• Very Vascular

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Pineal Gland

• Secretes Melatonin

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Thyroid Gland

• Lives inthe Neck
• Derivedfrom theBranchialArches

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Thyroid Gland

• Consists of Lobes
• Right and Left
• Isthmus
• Pyramidal

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Thyroid Gland

• Foramen Cecum inside the mouthdevelops into a
  small diverticulum
• This is draggedtowards the chestduring body
  folding

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Thyroid Gland

• Foramen Cecum lies medial to 1st and 2nd arches

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Thyroid Gland
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Branchial Arches

• Foramen Cecumbecomes Thyroid
• Third and Fourth Archesbecome Parathyroids
• Third Archbecomes Thymus

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Thyroid Gland

• Pyramidal Lobeis the remnant
• Right and LeftLobes are themain gland

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Thyroid Gland

• Heavily Vascular(Like most glands)
• Arterial Supplyand Venous Drainage
  fromBranchial Arches

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Thyroid Gland

• The gland consistsof Thyroid Follicles
• Cuboidal Epithelium
• Central Colloid
• Supportive Stroma
• Parafollicular Cells

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Thyroid Gland

• Thyroid Hormone
• Thyroxine (T4)
• Triiodothyronine (T3)
• C-Cells
• Calcitonin

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Parathyroids

• Aptly named glands that live around thyroid

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Branchial Arches

• Foramen Cecumbecomes Thyroid
• Third and Fourth Archesbecome Parathyroids
• Third Archbecomes Thymus

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Parathyroid Gland
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Parathyroid

• SecretesParathyroidhormone (PTH)

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Adrenal Glands

• These are pairedsuprarenal glands
• Embryologically
• Cortex forms first
• Gonadal Ridge
• Medulla forms second
• Neural Crest Origin

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Adrenal Glands

• Histologically,
• Its quite easyto see thedifferencebetweenCORT
  EX andMEDULLA

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Adrenal Glands
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Adrenal Cortex
This should remind you of the kidney
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Adrenal Medulla
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Adrenal Glands

• Adrenal cortex
• Glucocorticoids - cortisol
• Mineralocorticoids - aldosterone
• Androgens (including testosterone)
• Adrenal medulla
• Epinephrine
• Norepinephrine

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Gonads

• Well save these for Reproduction Endocrinology

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Orphan Endocrine Cells

• APUD Cells
• Amine Precursor Uptake and DecarboxylationA
  P U D
• Generate tissue and organ levels ofTraditional
  Neurotransmitters

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Orphan Endocrine Glands

• Heart
• Atrial-natriuretic peptide (ANP)
• Stomach and intestines
• Gastrin
• Somatostatin
• Secretin
• Cholecystokinin (CCK)
• Neuropeptide Y
• Liver
• Insulin-like growth factor
• Angiotensinogen
• Thrombopoietin

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Orphan Endocrine Glands

• Kidney
• Renin
• Erythropoietin (EPO)
• Calcitriol
• Skin
• Calciferol (vitamin D3)
• Adipose tissue
• Leptin

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Questions?