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Functions of the 
juxtaglomerular 
apparatus and 
hormonal control in 
the urinary system
Objectives… 
→ Characterization of the Juxtaglomerular 
apparatus; 
→ Hypothalamus-Pituitary System; 
→ Neurohypophysis ro...
An introduction to the 
juxtaglomerular apparatus … 
• The initial, straight part of the distal tubule makes 
contact with...
An introduction to the 
juxtaglomerular apparatus … 
http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2020/2020...
Constitution of the 
Juxtaglomerular Apparatus 
Juxtaglomerular 
Apparatus 
Juxtaglomerular 
Cells 
Secretion of the 
reni...
Constitution of the Juxtaglomerular 
Apparatus 
• JGA forms at the point of contact between a nephron's distal tubule (D) ...
Constitution of the Juxtaglomerular 
Apparatus 
• Smooth muscle cells of the afferent arteriole's (AA) tunica media are co...
Constitution of the Juxtaglomerular 
Apparatus 
• A plastic section through an afferent 
arteriole of a JGA shows the JG c...
Hypothalamus-Pituitary System 
• The pituitary gland is composed of an anterior part and a posterior part, 
directly attac...
Hypothalamus-Pituitary System 
The hypothalamo-hypophyseal portal system and hormone release 
in the pituitary.
Posterior Pituitary 
Oxytocin ADH 
- Uterine 
contractions; 
- Lactation. 
- Stimulates 
water 
retention; 
- Raises blood...
Posterior Pituitary 
Pars Nervosa 
• Modified neural tissues containing 
unmyelinated axons supported and 
ensheathed by g...
Adrenal Glands 
http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_mckinley/http://drmichaelroth.wordpress.com/tag/adren...
Aldosterone and the 
Renin-Angiotensin System 
http://antranik.org/the-renin-angiotensin-aldosterone-reflex/
Aldosterone and the 
Renin-Angiotensin System 
Decreased arterial 
pressure 
Increased 
stimulation of the 
JGA 
JG cells ...
Water Regulation by the ADH 
• Sometimes the body has too little water and needs to 
conserve it and too much water and ne...
Water Regulation by the ADH 
• ADH travels in the blood stream to the peritubular capillaries 
and binds to receptors on t...
Water Regulation by the ADH 
↓ Plasma Volume 
↓ Venous, atrial and arterial 
pressures 
Posterior Pituitary 
↑ Vasopressin...
Water Regulation by the ADH 
• Over 99% of the filtrate produced each day can be 
reabsorbed. 
• The amount of water reabs...
Relationship between 
the two systems 
http://www.quia.com/jg/1367589list.html
Relationship between 
the two systems 
• ADH and the RAAS are partners in homeostasis; 
• ADH alone would lower blood Na+ ...
Relationship between the two systems 
• Both increase water reabsorption. 
• The release of ADH is a response to an increa...
Potassium Regulation 
↓Plasma Volume 
↑Plasma angiotensin II 
↑Plasma Potassium 
Adrenal Cortex 
↑ Aldosterone secretion 
...
Thank you for 
your attention 
Follow Us: 
http://biomedeeks.blogspot.pt/
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Juxtaglomerular Apparatus

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Functions of the juxtaglomerular apparatus and hormonal control in the urinary system

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Juxtaglomerular Apparatus

  1. 1. Functions of the juxtaglomerular apparatus and hormonal control in the urinary system
  2. 2. Objectives… → Characterization of the Juxtaglomerular apparatus; → Hypothalamus-Pituitary System; → Neurohypophysis role in the regulation and renal functions; → Adrenal glands and their production of aldosterone; → Aldosterone and the Renin-Angiotensin System; →Water and Potassium regulation.
  3. 3. An introduction to the juxtaglomerular apparatus … • The initial, straight part of the distal tubule makes contact with the vascular pole of the renal corpuscle of its parent nephron and forms part of a specialized structure, the juxtaglomerular apparatus (JGA) LOCATION OF JUXTAGLOMERULAR APPARATUS http://withfriendship.com/user/neeraj/juxtaglomerular_apparatus.php
  4. 4. An introduction to the juxtaglomerular apparatus … http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2020/2020%20Exam%20Reviews/Exam%204/CH25%20Nephron%20III%20-%20Blood%20Supply%20&JGA.htm
  5. 5. Constitution of the Juxtaglomerular Apparatus Juxtaglomerular Apparatus Juxtaglomerular Cells Secretion of the renin hormone Macula Densa Sensitive to the concentration of NaCl
  6. 6. Constitution of the Juxtaglomerular Apparatus • JGA forms at the point of contact between a nephron's distal tubule (D) and the vascular pole of its glomerulus (G). • At that point cells of the distal tubule become columnar as a thickened region called the macula densa (MD).
  7. 7. Constitution of the Juxtaglomerular Apparatus • Smooth muscle cells of the afferent arteriole's (AA) tunica media are converted from a contractile to a secretory morphology as juxtaglomerular granule cells (JG). • Also present are lacis cells (L), which are extraglomerular mesangial cells adjacent to the macula densa, the afferent arteriole, and the efferent arteriole (EA).
  8. 8. Constitution of the Juxtaglomerular Apparatus • A plastic section through an afferent arteriole of a JGA shows the JG cells (arrowheads) with secretory granules containing renin. • Activities of the macula densa and renin released by JG cells produce an incompletely understood autoregulatory tubuloglomerular feedback loop: - To control arterial blood pressure, - To maintain a relatively constant rate of glomerular filtration despite changes in blood pressure.
  9. 9. Hypothalamus-Pituitary System • The pituitary gland is composed of an anterior part and a posterior part, directly attached to the hypothalamus region of the brain by a stalk called the infundibulum. • The gland occupies a fossa of the sphenoid bone called the sella turcica .
  10. 10. Hypothalamus-Pituitary System The hypothalamo-hypophyseal portal system and hormone release in the pituitary.
  11. 11. Posterior Pituitary Oxytocin ADH - Uterine contractions; - Lactation. - Stimulates water retention; - Raises blood pressure by contracting arterioles; - Induces male aggression.
  12. 12. Posterior Pituitary Pars Nervosa • Modified neural tissues containing unmyelinated axons supported and ensheathed by glia cells - pituicytes (P); • The axons run from the supraoptic and paraventricular hypothalamic nuclei and have swellings called neurosecretory (Herring) bodies (NB) - from which oxytocin and vasopressin are released upon neural stimulation. • The released hormones are picked up by capillaries (C) for distribution throughout the body.
  13. 13. Adrenal Glands http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_mckinley/http://drmichaelroth.wordpress.com/tag/adrenals/ endocrine%20system.htm
  14. 14. Aldosterone and the Renin-Angiotensin System http://antranik.org/the-renin-angiotensin-aldosterone-reflex/
  15. 15. Aldosterone and the Renin-Angiotensin System Decreased arterial pressure Increased stimulation of the JGA JG cells secrete renin into the blood Renin cleaves the plasma protein angiotensinogen Inactive decapeptide angiotensin I is formed Angiotensin converting enzyme (ACE) on lung capillaries clips this to angiotensin II Angiotensin II raises systemic blood pressure Angiotensin II stimulates the adrenals to secrete aldosterone Aldosterone promotes Na+ and water reabsorption in the distal tubules Increase blood pressure
  16. 16. Water Regulation by the ADH • Sometimes the body has too little water and needs to conserve it and too much water and needs to get rid of it. • Most of the control of water takes place in the distal and collecting tubules under control of ADH released by the posterior pituitary under control of the hypothalamus in the mid-brain area.
  17. 17. Water Regulation by the ADH • ADH travels in the blood stream to the peritubular capillaries and binds to receptors on the distal and collecting tubules which causes water channels to open in the tubule walls. • This allows water to diffuse through the tubule walls into the interstitial fluid where it is collected by the peritubular capillaries.
  18. 18. Water Regulation by the ADH ↓ Plasma Volume ↓ Venous, atrial and arterial pressures Posterior Pituitary ↑ Vasopressin Secretion ↑ Plasma Vasopressin Collecting Ducts ↑ Tubular Permeability to H2O ↑ H2O Reabsorption ↓ H2O excretion Excess H2O ingested ↓ Body-fluid osmolarity (↑ H2O concentration) ↓ Firing by the hypothalamic osmoreceptors Posterior Pituitary ↓ Vasopressin Secretion ↓ Plasma Vasopressin Collecting Ducts ↓ Tubular Permeability to H2O ↓ H2O Reabsorption ↑ H2O excretion
  19. 19. Water Regulation by the ADH • Over 99% of the filtrate produced each day can be reabsorbed. • The amount of water reabsorbed from the filtrate back into the blood depends on the water situation in the body. • When the body is dehydrated, most of the filtrate is reabsorbed.
  20. 20. Relationship between the two systems http://www.quia.com/jg/1367589list.html
  21. 21. Relationship between the two systems • ADH and the RAAS are partners in homeostasis; • ADH alone would lower blood Na+ concentration by stimulating water reabsorption in the kidney, but the RAAS helps maintain balance by stimulating Na+ reabsorption. http://www.quia.com/jg/1367589list.html
  22. 22. Relationship between the two systems • Both increase water reabsorption. • The release of ADH is a response to an increase in the osmolarity of the blood. • But, an excessive loss of both salt and body will reduce blood volume without increasing osmolarity. This will induce a change the RAAS that responds to the fall in blood volume and pressure by increasing water and Na+ reabsorption. http://www.samsca.com/pathophysiology-heart-failure.aspx
  23. 23. Potassium Regulation ↓Plasma Volume ↑Plasma angiotensin II ↑Plasma Potassium Adrenal Cortex ↑ Aldosterone secretion ↑ Plasma aldosterone Cortical collecting ducts ↑ Sodium Reabsorption ↑ Potassium secretion ↓ Sodium excretion ↑ Potassium excretion
  24. 24. Thank you for your attention Follow Us: http://biomedeeks.blogspot.pt/

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