Endocrine System

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Endocrine System

• How the body communicates with itself
• Nervous system impulses travel down nerves
• Endocrine system hormones released into the
  blood and travel to target organs.

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Endocrine System

• Glands can be one of three types
• Exocrine release secretions that are carried
  within a duct or tube sweat glands, salivary
  glands, sebaceous glands
• Endocrine release secretions directly into the
  blood thyroid gland, adrenal gland, anterior
  pituitary gland
• Heterocrine contain both exocrine and endocrine
  components pancreas, testis

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Endocrine System

• Endocrine system may consists of organs
  containing very specific concentrations of
  secretory cells (thyroid gland, pituitary gland,
  adrenal gland)
• Organs that have dispersed areas of special
  secretory cells (pancreas), testis, ovary)
• Dispersed cells within various organs (stomach,
  intestine, kidney)

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Two kinds of secreting cells
Nitrogen-secreting cell
Steroid secreting cell
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Primary Endocrine Glands Addressed in this Unit

• Hypophysis (Pituitary Gland)
• Thyroid Gland
• Parathyroid Gland
• Adrenal Gland
• Pancreas
• Testis and ovary will be covered in Reproductive
  System

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Thyroid and Parathyroid Glands

• Found at 2nd through 4th cartilages of the
  trachea
• Small gland with four parathyroid glands attached
  to the posterior surface.
• Follicles are the structural unit of the gland.
• Follicle consists of a wall of simple cuboidal
  epithelium cells inclosing a space containing a
  jelly-like substance called colloid. If the
  colloid distends the follicles, the epithelial
  cells can become flattened almost like simple
  squamous. Colloid combines with iodine to form
  thyroid hormones regulate body metabolism.

isthmus
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Thyroid Gland Abnormalities

• Hyperthyroid condition often result of tumor.
  Can produce disease called Graves syndrome
• Hypothyroid condition cretinism in children and
  myxedema in adults

Goggle-eyed
myxedema
Democratic Republic of the Congo Girl 15 with
Cretinism
Democratic Republic of the Congo Girl 15 with
Cretinism
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Thyroid and Parathyroid Glands

• Between the follicles are located small groups of
  parafollicular cells which secrete hormone
  thyrocalcitonin or often called just calcitonin.
• Calcitonin functions to reduce calcium levels in
  the blood by actively reducing breakdown of bone
  and inhibiting re-absorption of calcium in
  digestive system.

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Adrenal Gland

• Adrenal gland is located above each kidney
• Divided on bases of outer region (cortex) and
  inner region (medulla)
• The cortex is divided into three regions
  (glomerulosa, fasciculatus, and reticularis)

• Ectodermendoderm

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Adrenal Gland

• Adrenal Cortex consists of three regions
• Outer region known as the zona glomerulosa.
  Theses cells are arranged in rounded clumps and
  secrete hormones known as mineralcorticoids.
• The most common mineralcorticoid is aldosterone
  which helps to control electrolyte and water
  balance.
• The next region is known as the zona fasciculata.
  It consists of columns of cells. It secretes
  hormone known as glucocorticoids including
  cortisone and hydrocortisone.
• These hormones help to regulate glucose
  metabolism and important in inflamation reactions
  and stress management.

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• The inner region of the cortex is the zona
  reticularis. Cells of this region form and
  network of interlinking cells.
• Secrete sex hormones mainly androgens or male sex
  hormones. Usually in small proportions if too
  many can cause bearded lady.
• Adrenal Medulla
• Consist of irregularly arranged groups of
  granular cells and connective tissue
• Produces two products epinephrine and
  norepinephrine.
• Part of the bodies response to an emergency or
  the fight or flight response

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Pituitary or Hypophysis

• Small gland about size of large pea located under
  brain.
• Often referred to as the master gland.
• Secretes hormones that regulate other endocrine
  glands
• Consists of two major lobes, anterior and
  posterior separated by intermediate lobe.
• The larger anterior lobe referred to as the
  adenohypophysis. This is a highly glandular
  tissue that produces and secretes numerous
  hormones.
• The second smaller posterior lobe is referred to
  as the neurohypophysis. This is neural tissue
  that secretes two hormones produced by
  hypothalmus.

posterior lobe
Anterior lobe
D pars distalis, I pars intermedia N pars
nervosa, S stem or stalk T pars tuberalis
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Pituitary gland or Hypophysis
Adenohypophysis
Neurohypophysis
Pars distalis or anterior lobe
Pars nervosa or posterior lobe
Intermedia between black lines
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Adenohypothesis

• Larger anterior lobe
• Subdivided into the glandular pars distalis which
  is most of the lobe and is active in secretion
• Also contains the pars tuberalis that forms
  covering for stalk
• The pars intermedia separates the anterior lobe
  from the posterior lobe

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Adenohypophysis

• Cell types in the adenohypophysis are identified
  as to their staining characteristics
• Chromophilic cells include the acidophils which
  stain with eosin stain and are thus reddish and
  the basophils which stain with hematoxylin and
  are thus dark blue/purple colored in
  hematoxylin/eosin staining.
• Chromophobes do not stain with either stain
• There are different types of Acidophils that can
  be separated with very special stains. These can
  not be separated with H E stains. They
  include
• Somatrophs secrete Growth Hormone
• Mammotrophs secrete prolactin
• There are different types of Basophils that can
  be separated with very special stains. These can
  not be separated with H E stains. They
  include
• Thyrotrophs secrete Thyroid Stimulating
  Hormone
• Gonadotrophs secrete Luteinizing (LH) hormone
  and Follicle Stimulating Hormone (FSH).
• ACTH-secrete adenocorticotrophic hormone
  regulates adrenal cortex
• Chromophobes

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Growth Hormone function
Young female dwarf standing next to a boy of
normal stature. gigantism
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Posterior lobe or Neurohypophysis

• Consists mostly of nervous tissue, pituitary
  cell, herring body
• Does not produce any hormones but does secrete
  two hormones produced by the hypothalamus
• Secretes oxytocin regulates uterine muscle
  contraction and mammory glands stimulating milk
  flow
• Secretes ADH Antidiuretic hormone which
  increases water retention by the kidney