Histology - Endocrine System Video
Transcript of Histology - Endocrine System Video
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Endocrine System
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What we’ll talk about…
• Hypothalamus and Pituitary Gland
• Adrenal Gland
• Thyroid Gland
• Parathyroid Gland
• Endocrine Pancreas
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Cerebralcortex
Hypothalamus
Anterior Pituitary
Adrenalgland Thyroid
Target tissues
Releasing Hormones
ACTH TSH
Cortisol T3/T4
Low Blood Pressure
Aldosterone
Pancreas
Glucose
Insulin
Parathyroid
Low Ca2+
PTH
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Pituitary Gland
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The pituitary contains distinct anterior and posterior regions and interfaces with the hypothalamus.
Hypothalamus
Anterior Pituitary Posterior Pituitary
Pituitary Stalk Hypothalamic Axons
Cluster of hormome-secreting cells
Axon termini release hormones
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The anterior pituitary contains different cells that produce different unique hormones.
• Adrenocorticotrophic Hormone (ACTH) - Corticotrophs
• Thyroid-Stimulating Hormone (TSH) - Thyrotrophs
• Growth Hormone (GH) - Somatotrophs
• Prolactin - Mammotrophs
• Leutenizing Hormone (LH) - Gonadotrophs
• Follicle-Stimulating Hormone (FSH) - Gonadotrophs
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Hypothalamic neurons release oxytocin or vasopressin in the posterior pituitary.
• Oxytocin - induce uterine contraction and ejection of milk from mammary glands
• Vasopressin - increase water absorption in collecting ducts
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The anterior pituitary is highly cellular while the posterior pituitary connects to the hypothalamus.
Anterior Pituitary
Posterior Pituitary
Hypothalamus
Pituitary Stalk
Optic Chiasm
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H&E stain reveals a mix of acidophils, basophils, and chromophobes in the anterior pituitary.
Acidophil
Basophil
Chromophobe
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Reticulin fibers organize cells into clusters in the anterior pituitary.
Reticulin Fibers
Capillary
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Releasing hormones trigger secretion of specific hormones by cells in the anterior pituitary.
• Corticotropin Releasing Hormone (CRH) -> ACTH
• Thryotropin Releasing Hormone (TRH) -> TSH
• Growth Hormone Releasing Hormone (GHRH) -> GH
• Gonadotropin Releasing Hormone -> FSH and LH
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The hypothalamus produces releasing hormones which move through the portal vein to the anterior pituitary.
Hypothalamus
Anterior Pituitary
Portal Vein
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Cells in the anterior pituitary store hormones in granules and
Fenestrated Endothelium
SomatotrophSecretory Granule
Interstitium
Capillary Lumen
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The posterior pituitary contains the axons of neurons whose cell bodies reside in the hypothalamus.
Hypothalamus
Anterior Pituitary Posterior Pituitary
Pituitary Stalk Hypothalamic Axons
Cluster of hormome-secreting cells
Axon termini release hormones
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Pituicytes are support cells in the posterior pituitary.
Herring Body
Pituicyte
Blood Vessel
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Hormones released in the posterior pituitary diffuse across a fenestrated endothelium.
Capillary Lumen
Fenestrated Endothelium
Axon Terminus
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Adrenal Glands
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The adrenal gland is composed of glomerulosa, fasciculata, retirularis and medulla.
GlomerulosaFasciculataReticularis
CortexMedulla
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Cells in the glomerulosa secrete mineralocorticoids and are clustered by trabeculae.
Glomerulosa Capsule
Fasciculata
Trabecula
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Cells in the fasciculata secrete glucocorticoids and stain more lightly than glomerulosa.
Fasciculata
Glomerulosa
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Cortisol generates negative feedback by inhibiting secretion of CRH and ACTH.
CRH
ACTH
AdrenalGlands
Cortisol
Corticotroph
Hypothalamus
Pituitary Cell
Target Cell
Hormone
Throphic Hormone Nega
tive
Feed
back
Cortisol Pathway
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Cortisol and aldosterone are structurally similar and produced by the same biochemical pathway.
O
CH3
HOCH3
C O
CH2OH
O
CH3
HOC
C O
CH2OH
O
H
O
CH3
HOCH3
C O
CH2OH
OH
O
CH3
OCH3
C O
CH2OH
OH
Aldosterone
Corticosterone Cortisol Cortisone
Glomerulosa Cells
17 α-Hydroxylase 11 β-Hydroxysteroid dehydrogenase (HSD)
Cholesterol
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The reticular is the inner most layer of the adrenal cortex and produces androgens.
Reticularis
Fasciculata
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Cells in the medulla secrete epinephrine and norepinephrine in response to external stress.
Medulla
Reticularis
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Blood can follow two different pathways through the adrenal gland.
Central Vein
Fasciculata
Glomerulosa
Reticularis
Medulla
Capsule
Plexus
Long Cortical Artery
Short Cortical Artery
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Thyroid
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The thyroid secretes and stores inactive hormone in large pools called colloid.
C-cell
Colloid
Principle Cell
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Na+ I-
I-I0
CH2
OH
CH2
OH
CH2
OH
CH2
OH
CH2
OH
CH2
OH
CH2
OH
CH2
OHCH2
O
OH
CH2
O
OH
CH2
O
OH
CH2
O
OH
Thyroglobulin secretion
Iodination
EndocyticVesicle
Lysosome
Conjugation
Cl-
T3 T4
TPO
T4T3
Colloid
Principle Cell
Interstitium
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T3 and T4 exert negative feedback on the release of TRH and TSH.
CRH TRH
TSHACTH
AdrenalGlands
Cortisol T4/T3
Corticotroph
Hypothalamus
Pituitary Cell
Target Gland
Hormone
Throphic Hormone Nega
tive
Feed
back
Cortisol Pathway T4/T3 Pathway
Thyroid
Nega
tive
Feed
back
Thyrotroph
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Parathyroid
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Parathryoid contains chief cells that release parathyroid hormone when serum calcium is low.
Chief Cells
Oxyphil Cell
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Endocrine Pancreas
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Cells in the endocrine pancreas secrete glucagon (α), insulin (β) or somatostatin (δ).
Exocrine Pancreas
Islet of Langerhans
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Take home messages…
• Hypothalamus regulates secretions from anterior pituitary.
• Hormones from anterior pituitary regulate cells in other organs.
• The adrenal gland generates mineralcorticoids, glucocorticoids, androgens and epinephrine from different regions.
• The thyroid gland produces T3 and T4 hormones.
• The hypothalamic-pituitary-adrenal axis produces cortisol in response to stress.