2021 The Endocrine System

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20-21 The Endocrine System

• I. Overview
• II. Pituitary
• III. Adrenals
• IV. Pancreas
• V. Thyroid
• VI. Parathyroids
• General structure fenestrated capillaries

http//www.ama-assn.org/ama/pub/category/7157.html
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I. Pituitary

• A. Development
• 1. neurohypophysis (post. Lobe) (20.1)
• a. develops as outgrowth of diencephalon
• b. forms
• 1) pars nervosa (posterior lobe note
  error in 20.1)
• 2) infundibulum

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I. Pituitary

• A. Development
• 2. adenohypophysis ( ant. Lobe) (20.1)
• a. develops from Rathkes pouch
• 1) oral ectoderm
• b. forms
• 1) pars distalis (anterior lobe)
• 2) (pars tuberalis pars intermedia)

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I. Pituitary

• B. Hypothalamo-hypophyseal portal system (20.2)
• 1. primary capillary plexus
• a. base of infundibulum / hypothalamus
• 2. veins to anterior lobe
• 3. secondary capillary plexus
• 4. transports neurohormones
• a. releasing hormones
• b. inhibiting hormones

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I. Pituitary

• C. Pars distalis 20.6
• 1. Chromophobes chromophils
• 2. basophils
• a. gonadotrophic cells
• 1) FSH
• 2) LH
• b. thyrotropic cells
• 1) TSH
• c. corticotrophic cells
• 1) ACTH

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I. Pituitary

• C. Pars distalis
• 3. acidophils
• a. somatotropic cells
• 1) GH
• b. mammotropic cells
• 1) PRL

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I. Pituitary

• D. Neurohypophysis (20.3)
• 1. pituicytes
• 2. neurosecretory cells
• 3. 100,000 unmyelinated axons from
  hypothalamus

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I. Pituitary

• D. Neurohypophysis 20-9

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I. Pituitary

• D. Neurohypophysis 20.7
• 4. vasopressin / ADH
• a. contraction of smooth muscle in arteries
• b. increase reabsorption of H2O in
  collecting tubules
• 5. oxytocin
• a. contraction in pregnant uterus

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III. Adrenals

• A. Overview (21.2)
• 1. adrenal cortex
• a. steroids
• 2. adrenal medulla
• a. E NE
• 3. stroma
• a. capsule
• b. trabeculae
• c. reticular fibers
• 4. extensive capillary plexuses

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III. Adrenals

• B. Adrenal cortex (21.2)
• 1. zona glomerulosa (21.3)
• a. 15 of adrenal cortex

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III. Adrenals

• B. Adrenal cortex
• 1. zona glomerulosa
• b. clusters of cells (21.3)
• c. mineralocorticoids (aldosterone)
• 1) increase DCT absorption of Na

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III. Adrenals

• B. Adrenal cortex
• 2. zona fasciculata (21.3)
• a. 65 of adrenal cortex
• b. cells in cords (21.3)

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III. Adrenals

• B. Adrenal cortex
• 2. zona fasciculata
• c. many lipid droplets in cytoplasm (21.3)
• d. glucocorticoids (cortisol
  corticosterone)
• 1) influence CHO metabolism
• 2) suppress immune response

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III. Adrenals

• B. Adrenal cortex
• 3. zona reticularis (21.3)
• a. 7 of adrenal cortex

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III. Adrenals

• B. Adrenal cortex
• 3. zona reticularis
• b. irregular cords in network (21.5)
• c. lipofuscin granules
• d. androgens
• e. little effect vs. testicular hormones

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III. Adrenals

• C. Adrenal medulla (21.3)
• 1. cells in cords
• 2. secrete E NE
• 3. innervated by preganglionic sympathetic
  (myelinated) axons

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III. Adrenals

• Adrenal medulla
• Look for
• Preganglioni sympathetic fibers
• Blood vessels

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IV. Pancreas (Islets of Langerhans)
http//diabetes.niddk.nih.gov/dm/pubs/dictionary/P
-T.htm
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IV. Pancreas (Islets of Langerhans)

• A. Cluster of cells in cords (21.9)
• 1. network of fenestrated capillaries

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IV. Pancreas (Islets of Langerhans)

• A. Cluster of cells in cords
• 2. A cells glucagon, incr. blood sugar
  (21.11)
• immunohistochemistry for glucagon cells

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IV. Pancreas (Islets of Langerhans)

• A. Cluster of cells in cords
• 3. B cells insulin, decr. blood sugar (21.12)
• 4. D cells somatostatin inhibits A B cells
• 5. E cells unknown function
• immunohistochemistry for insulin

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V. Thyroid

• A. Gross Anatomy (21.15)
• 1. anterior to larynx
• 2. two lobes connected by isthmus
• 3. well vascularized

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V. Thyroid

• B. Follicles (21.16,21.17)
• 1. squamous to columnar epithelium
• a. squamous inactive
• b. columnar active
• 2. colloid
• a. thyroxine / T4
• b. triiodothyronine / T3
• 3. stimulates rate of metabolism
• 4. Influenced by TSH

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V. Thyroid

• C. Parafollicular cells (21.18)
• 1. calcitonin
• a. decr. blood Ca

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VI. Parathyroid glands

• A. Gross anatomy (21.22)
• 1. four small glands
• 2. located on posterior of thyroid gland

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VI. Parathyroid glands

• Microscopic anatomy 21.16

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VI. Parathyroid glands

• B. Parenchyma
• 1. oxyphil cells (21.24)
• a. larger, polygonal cells
• b. unknown function

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VI. Parathyroid glands

• 2. chief cells 21.23
• a. pale, acidophilic cytoplasm b.
  secretes parathyroid hormone c. incr. blood
  Ca levels