JUXTA-GLOMERULAR APARRATUS ycfyhdrgg .pptx

JUXTA-GLOMERULAR APARRATUS ycfyhdrgg .pptx

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  LECTURER-PHYSIOLOGY FACULTY OF AHS K.K.SREEVATSAN BAH201 DR.MGRUNIVERSITY AND RESEARCH INSTITUTE JUXTA-GLOMERULAR APPARATUS
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  JUXTA-GLOMERULAR APARRATUS
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  INTRODUCTION  Juxta-glomerular apparatusis a specialized organ situated near the glomerulus of each nephron (juxta = near).  Juxta-glomerular apparatus is formed by three different structures: 1. Macula densa 2. Extraglomerular mesangial cells 3. Juxtaglomerular cells.
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  CELLS OF JGA MACULA DENSA: Macula densa is the end portion of thick ascending segment before it opens into distal convoluted tubule. It is situated between afferent and efferent arterioles of the same nephron. It is very close to afferent arteriole. Macula densa is formed by tightly packed cuboidal epithelial cells.  MESENGIAL CELLS: Extraglomerular mesangial cells are situated in the triangular region bound by afferent arteriole, efferent arteriole and macula densa. These cells are also called agranular cells, lacis cells or Goormaghtigh cells.
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  CELLS OF JGA GLOMERULAR MESENGIAL CELLS: Besides extraglomerular mesangial cells there is another type of mesangial cells situated in between glomerular capillaries called glomerular mesangial or intraglomerular mesangial cells. Glomerular mesangial cells support the glomerular capillary loops by surrounding the capillaries in the form of a cellular network. These cells play an important role in regulating the glomerular filtration by their contractile property
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  CELLS OF JGA JUXTA-GLOMERULAR CELLS: Juxtaglomerular cells are specialized smooth muscle cells situated in the wall of afferent arteriole just before it enters the Bowman capsule. These smooth muscle cells are mostly present in tunica media and tunica adventitia of the wall of the afferent arteriole. Juxtaglomerular cells are also called granular cells because of the presence of secretary granules in their cytoplasm.
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  FUNCTIONS OF JGA It activates Renin-Angiotensin mechanism. Renin is an enzyme which converts Angiotensinogen to Angiotensin-I.  Then Angiotensin-I converted to Angiotensin-II by Angiotensin Converting Enzyme (ACE) Enzyme secreted by lungs.  Angiotensin-II activates Aldosterone and It further converted into Angiotensin-III & IV. Aldosterone is an hormone which regulates the sodium and other electrolytes like Pottasium, Bicarbonate, etc.,  It regulates the blood pressure by Vaso constriction. It is performed by Angiotensin-II.
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  FUNCTIONS OF JGA Itincreases water intake by stimulating the thirst center. It increases the secretion of orticotropin-releasing hormone (CRH) from hypothalamus.CRH in turn increases secretion of adrenocorticotropic hormone (ACTH) from pituitary. It increases secretion of antidiuretic hormone (ADH) from hypothalamus.  Angiotensin II acts as a growth factor in heart and it is thought to cause muscular hypertrophy and cardiac enlargement.
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  FUNCTIONS OF JGA Extraglomerular mesangial cells of juxtaglomerular apparatus secrete prostaglandin.  Prostaglandin is also secreted by interstitial cells of medulla called type I medullary interstitial cells. Extraglomerular mesangial cells of juxtaglomerular apparatus secrete cytokines like interleukin-2 and tumor necrosis factor. Macula densa secretes thromboxane A2 .
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  FUNCTIONS OF JGA Angiotensin-III increases the blood pressure and stimulates aldosterone secretion from adrenal cortex. It has 100% adrenocortical stimulating activity and 40% vasopressor activity of angiotensin-II.  Angiotensin-IV also has adrenocortical stimulating and vaso pressor activities.  Macula densa of juxtaglomerular apparatus plays an important role in the feedback mechanism called tubuloglomerular feedback mechanism, which regulates the renal blood flow and glomerular filtration rate
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