Chapter 25 Endocrine System

1
Chapter 25 Endocrine System
2
Introduction

• Ductless glands
• Secrete hormones
• Control other organs / cells (target tissue)

3
Components

• Pituitary gland
• Thyroid gland
• Parathyroid gland
• Adrenal gland
• Pancreas
• Others
• Gonads
• Hypothalamus
• Enteroendocrine glands
• Thymus

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4
Pituitary

• Located in sella turcica
• Infundibulum
• Stalk connects to hypothalamus
• Adenohypophysis
• Anterior pituitary
• Gland tissue
• Neurohypophysis
• Posterior pituitary
• Neural pituitary

25.3abc
5
Development of Pituitary

• From 6-8 weeks
• the neurohypophyseal bud grows inferiorly from
  the hypothalamus
• the hypophyseal pouch grows superiorly from the
  roof of the mouth (Rathkes pouch)
• neurohypophyseal bud becomes the posterior lobe
  (neurohypophysis)
• hypophyseal pouch becomes the anterior pituitary
  (adenohypophysis)

5-6 wks
25.14a-d
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Adenohypophysis (ant. pit.)

• 7 hormones
• GH growth hormone
• Stimulates body growth, e.g., epiphyseal plate
• PRL prolactin
• Stimulates mammary glands to produce milk
• TSH thyroid stimulating hormone
• ? TH, ? metabolic rate
• ACTH adrenocorticotropic hormone
• Stimulate adrenal cortex to secrete steroids

7
Adenohypophysis

• MSH melanocyte stimulating hormone
• FSH follicle stimulating hormone
• Stimulates development of sperm and ova
• LH luteinizing hormone
• Stimulates development of sperm and ova

8
Hypothalamus

• Controls adenohypophysis
• Releasing hormones
• Inhibiting hormones

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Hypophyseal portal system

• Hormones secreted in hypothalamus
• Enter capillaries
• Carried by hypophyseal portal veins
• Second capillary bed in adenohypophysis
• Hormones affect adenohypophyseal cells

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Neurohypophysis

• Nerve cell bodies in hypothalamus
• Axons to neurohypophysis via infundibulum

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ADH (antidiuretic hormone), vasopressin

• Targets DCT and collecting tubules
• ? H2O reabsorption
• ? blood volume
• ? BP
• ? concentration of urine, ? volume

23.4b
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Oxytocin

• Stimulates smooth muscle of uterus during
  childbirth

24.26cd
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Thyroid gland

• Located around trachea
• Just inferior to larynx

25.7
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Thyroid follicle

• Functional unit
• Sphere of cells
• Secrete TH precursor
• TH stimulates basal metabolic rate
• Influenced by TSH

25.7bc
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Hyperthyroidism exophthalmos

• Protrusion of one or both eyeballs that results
  from orbital inflammation, edema, tumors, or
  injuries cavernous sinus thrombosis or
  enlargement of the eyeball (as in congenital
  glaucoma and unilateral high myopia).
• In hyperthyroidism, edema and lymphoid
  infiltration of the orbital tissues may cause
  unilateral or bilateral exophthalmos.
• http//www.merck.com/mrkshared/mmanual/section8/ch
  apter92/92c.jsp

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Graves disease / hyperthyroidism

• Graves' disease patient with exophthalmos and
  vitiligo.
• Vitiligo is a skin condition resulting from loss
  of pigment which produces white patches. It may
  be an autoimmune process
• http//www.aad.org/pamphlets/Vitiligo.html

http//www.thyroidmanager.org/Chapter11/11-text.ht
m
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Parafollicular cells

• Located between follicles
• Secrete calcitonin
• ? blood Ca levels
• Inhibits osteoclasts
• ? Ca secretion in kidney
• Mainly in childhood

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Parathyroid glands

• Location 2 pairs of tiny glands on posterior
  surface of thyroid gland
• PTH
• ? blood Ca
• Stimulates osteoclasts
• ? excretion of Ca by kidney
• Activates vitamin D

25.9a
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Adrenal gland

• Located on superior surface of kidney
• Adrenal medulla
• Secretes norepinephrine epinephrine
• Targets sympathetic effector organs
• Adrenal cortex
• Secretes corticosteroids
• sER

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Adrenal cortex

• Aldosterone
• ? reabsorption of H2O and Na in kidney
• Cortisol
• Helps body deal with stress
• ? blood glucose levels
• Anti-inflammatory, suppresses immune response

21
Pancreas

• Exocrine pancreas
• Digestive enzymes
• Endocrine pancreas
• Islets of Langerhans
• ? cells
• Secrete glucagon
• ? blood sugar levels
• ? cells
• Secrete insulin
• ? blood sugar levels

25.12