Introduction:
The juxtaglomerular apparatus is found in the nephron of the kidney. It comprises the glomerulus, distal tubules, afferent and efferent arteriole. The juxtaglomerular apparatus is located where the afferent arteriole and the distal convoluted tubule meet. It consists of specialized cells which produce renin, also known as juxtaglomerular or granular cells. These cells help control blood pressure and maintain sodium and potassium levels. It gets activated by the juxtaglomerular cells when the blood pressure falls to a low level. It is a part of the renin-angiotensin-aldosterone system. The primary function of the juxtaglomerular apparatus is to look into the blood pressure levels, maintain normal glomerular filtration rate, and facilitate well-ordered sodium reabsorption because it is located in the nephron. It has been highly sensitive to changes in renal perfusion pressure. It is innervated adrenergically and has beta-1 receptors.
What Is Juxtaglomerular Apparatus?
The juxtaglomerular apparatus is a complex structure consisting of glomeruli, distal tubules, and afferent and efferent arterioles. It is present in the nephron, also known as the functional and structural unit of the kidney. Afferent arteriole and distal convoluted tubule meet at the juxtaglomerular apparatus. The juxtaglomerular apparatus is also known as the juxtaglomerular complex.
Elaborate Facts About Kidneys:
The kidneys are a part of the renal system of the body. These are two in number and are shaped like a bean. Kidneys have many important functions, like eliminating toxins and waste products from the blood.
The Function:
Blood reaches the kidney through the renal artery. Tiny blood vessels help in the filtration of the blood. Then the filtered blood returns to the bloodstream via the renal vein.
The Kidneys Also Have the Following Functions:
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They control the pH balance in the blood.
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Produces glucose if the blood lacks it.
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Produces renin which regulates blood pressure.
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Produces the hormones calcitriol and erythropoietin.
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The nephron is the primary functional unit of the kidney.
What Is a Nephron?
Nephron is the functional unit of the kidneys. There are about one million nephrons in each kidney. The nephron has been divided into three parts, the renal corpuscle, renal tubule, and the collecting duct. Glomerulus and bowman’s capsule make the renal corpuscle. The proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule make the renal tubule. Each is a long, elongated structure that is extremely fine in size. Cortical nephrons and juxtamedullary nephrons are the two types of nephrons. The cortical nephrons are situated in the cortex and fall short of reaching the medulla of the kidney. The majority of nephrons are the cortical nephrons found in the kidneys. Juxtamedullary nephrons constitute renal corpuscles at the junction of the cortex and medulla. These nephrons penetrate deep into the medulla.
What Is Renin?
Renin is produced from specialized cells of the kidney known as glomerular or juxtaglomerular cells found in the juxtaglomerular apparatus. It is considered both a hormone and an enzyme as it is secreted by the kidney and affects the vasoconstriction of the arteries. The principal function of renin is to regulate blood pressure. It is a part of the renin-angiotensin-aldosterone system, which works along with angiotensin and aldosterone to regulate sodium and potassium levels.
The Blood Pressure Is Regularized in the Following Way:
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Renin helps to convert angiotensinogen into angiotensin.
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Angiotensin I gets converted into angiotensin II.
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Angiotensin is responsible for narrowing down the blood vessels.
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When angiotensin II narrows down the blood vessels, aldosterone is released.
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Aldosterone helps the kidneys retain the water level and salts; when the level of water increases, the blood pressure increases.
Renin Is Released in the Following Way:
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It is released to maintain blood pressure. When the blood pressure lowers to a certain level and the sodium level decreases, renin is released by the juxtaglomerular cells.
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The baroreceptors detect that the blood pressure level has lowered. The baroreceptors are located in the blood vessels.
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The kidneys detect low levels of sodium.
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Then the beta-1 adrenergic receptors, responsible for regulating the heart rate, sense a change in the sympathetic nervous system and are signaled for further procedure.
What Is The Anatomy of Juxtaglomerular Apparatus?
The juxtaglomerular apparatus consists of extraglomerular mesangium, macula densa, the afferent arteriole's endpoint, and the efferent arteriole's start point. The juxtaglomerular apparatus is made from vascular component, which consists of afferent and efferent arteriole and the extraglomerular mesangium, and the tubular part comprising macula densa. It is located in the glomerular hilum.
Extraglomerular Mesangium:
The extraglomerular mesangium is the specialized part of the apparatus that connects the glomerulus's hilum. It secrets the renin by sensing the low level of tubular fluid and the intravascular volume. It is also known as the polar cushion (polkissen) or the lacis. They are present in the afferent part of the arterioles.
Macula Densa:
These are the chief cells in the kidney that play the role of sensory and regulatory functions in maintaining body fluid, homeostasis, and blood pressure. They are located in the distal nephron at the beginning of the glomerulus.
An Afferent Arteriole:
It is the connection between the renal artery and the glomerular capillary network of the kidney’s nephron. The filtering process begins here. It also takes part in controlling blood pressure.
An Efferent Arteriole:
An efferent arteriole is responsible for sending blood away from the capillaries. The extraglomerular mesangium cells are found in the proximity of the macula densa cells. The macula densa cells and extraglomerular mesangium are distinguished by an interstitial cleft of varying widths.
What Are the Juxtaglomerular Granular Cells?
The cells are located majorly in the afferent arteriole and minorly in the efferent arterioles. They are called both epithelial and myoepithelial because they show traits of smooth muscle cells and secretory epithelial cells. The basic structure of juxtaglomerular granular cells shows myofilaments in the cytoplasm and endoplasmic reticulum that are highly developed and also a golgi complex. Numerous electron-dense, membrane-bound granules with different sizes and shapes can be found in the juxtaglomerular cells. The renin granules, lipofuscin granules, and extraglomerular mesangial cells are found in them.
Conclusion:
The juxtaglomerular complex or juxtaglomerular apparatus is a vital part of the kidneys. It plays important functions in regulating blood pressure and eliminating toxins from the blood. It is situated in the nephron which is the structural and functional unit of the kidney. These release renin which helps in regulating blood pressure, and monitoring sodium and potassium levels.
