The kidneys are organs that filter out the waste product and functions as the disposal system for the body. As much as 1/3 of the blood that leaves the heart passes through the kidneys to be filtered before flowing into the rest of the body. Although a person can live with just one functioning kidney, or kidneys are very vital organs; The loss of both kidneys would cause a rapid buildup of waste and death with a few days.
The Location of the Kidneys
The kidneys are a combination of organs found extending the posterior muscular wall of the abdominal cavity. The left kidney is positioned slightly superior to the right kidney due to the large dimension of the liver on the right side of the body. Different from other organs in the abdomen, the kidney sits behind the peritoneum, which lines the abdominal cavity and thus is considered to be retroperitoneal organs. The ribs and muscles of the back protect the kidneys from being damaged externally. Adipose tissue also known as perirenal fat surrounds the kidney and act as protective padding.
Structure of the kidneys
The kidneys are shaped like beans with the convex side of each organ positioned laterally and the concave side medial. The cavity on the concave controlling of the kidney, also known as the renal hilus, provides a space for the renal artery, renal vein, and ureter to enter the kidney.
A thin layer of coarse connective tissue creates the renal capsule enclosing each kidney. The renal capsule produces a rigid outer shell to maintain the shape of the soft inner tissues.
Deep to the renal capsule is the dense, soft, vascular, renal cortex. Seven cone-shaped renal pyramids from renal medulla deep to the renal cortex. The renal pyramids are arranged with their bases standing outward via the renal cortex, and their apexes lead inward toward the center of the kidney.
Each apex attaches to a minor calyx, a tiny hollow tubing that stores urine. The minor calyces join to form 3 larger primary calyces, which additionally join to create the deep renal pelvis in the middle of the kidney. The renal pelvis exits the kidney at the renal hilum, where the urine empties into the ureter.
The renal arteries branch immediately from the abdominal aorta and enter the kidneys within the renal hilus.
Inside our kidneys, the renal arteries separate into the shorter afferent arterioles of the kidneys.
Each afferent arteriole brings blood into the renal cortex, where it separates into a bundle of capillaries recognized as a glomerulus.
From the glomerulus, the blood recollects into little efferent arterioles that descend into the renal medulla.
The efferent arterioles branch into the peritubular capillaries that encompass the renal tubules.
Next, the peritubular capillaries join to form veins that join again to form the large renal vein.
Finally, the renal vein leaves the kidney and combines with the inferior vena cava, which takes blood back to the heart.
The Nephron Each kidney contains nearly 1 million individual nephrons, the kidney’s microscopic functional units that filter blood to produce urine. The nephron consist of 2 main parts: the renal corpuscle and the renal tubule.
The renal corpuscle is created by the capillaries of the glomerulus and the glomerular capsule ( it is known as Bowman’s capsule) It is responsible for filtering the blood. The glomerulus is a bunched network of capillaries that increase the surface area of blood in contact the blood vessels walls. Encompassing the glomerulus is the glomerular capsule, a cup-shaped double layer of simple squamous epithelium with a goal space between the layers. Speical epithelial cells are known as podocytes from the layer of the glomerular capsule enclosing the capillaries of the glomerulus. Podocytes function with the endothelium of the capillaries to produce a thin filter to separate urine from blood passing through the glomerulus. The outer layer of the glomerular capsule contains the urine separated from the blood inside the capsule. Opposite the glomerulus, at the far end of the glomerular capsule, is the mouth of the renal tubule.
A group of tubes described as the renal tubule store urine and collect non-water solutes from the urine. The renal tubule transports urine from the glomerular capsule to into renal pelvis.
1.The curvy first section fo the renal tubule is referred to as the proximal convoluted tubule. The tubule cells that extend the proximal convoluted tubule reabsorb much of the water and nutrients initially filtered into the urine. 2. Next, the urine passes through the loop of Hele, a long straight tubule that transports urine into the renal medulla before creating a hairpin turn and then flowing back to the renal cortex.
3. The distal convoluted tubule extends the loop of the Henle
4.Eventually, urine from the distal convoluted tubules of various nephrons starts the storage duct, which takes the concentrated urine into the renal medulla and toward the renal pelvis.
5.From the renal pelvis, urine forms many collecting ducts combine and flows out of the kidneys and into the ureters.
Excretion of Wastes
The primary function of the kidney is to excrete waste products that result from muscle contraction and protein metabolism. The liver metabolizes dietary proteins to create energy for the body and produces toxic ammonia, which is a waste product. The liver will convert most fo the ammonia into uric acid and urea, becoming less toxic to the body. The body’s muscle uses creatine as an energy source and will process, and produce waste product creatinine.Uric acid, Ammonia, urea, and creatinine all will accumulate inside the body over time and need to be removed from circulation to maintain the body’s homeostasis
The Glomerulus, located in the kidney, will filter all four waste products out the bloodstream, which allows the body to excrete the waste from the body through urine. Around 50% of the urea found in the blood is reabsorbed by the tubule cells of the nephron and returned into the blood supply. Urea, within in the blood assist to concentrate additional, more toxic waste products in the urine by controlling the osmotic balance among urine and blood in the renal medulla.
Filtration, Reabsorption, and Secretion
The kidneys filter blood as it moves through the capillaries that create the glomerulus. Blood pressure forces most of the blood plasma through the lining of the capillaries and into the glomerular capsule. Blood cells remain within the capillary along with plasma residual since blood cells are too large to pass through the capillary lining The filtered plasma, called tubular fluid, begins to flow out of the glomerular capsule into the proximal convoluted tubule.
Also, peptide blood that remains inside the capillaries of the glomerulus moves into the efferent arterioles and on the peritubular capillaries encompassing the proximal convoluted tubule. Epithelial cells lining the tubule actively record valuable molecules of amino acids, glucose, and ions from the filtrate and place them back into the blood. Remaining waste products such as ammonia and creatinine are absorbed by these cells and the chemicals muscles into the filtrate. Osmotic pressure pushes water to form the dilute, while acolytes are exchanged, hypotonic filtrate back into the concentrated hypertonic blood.
The tubular fluid next goes into the loop of Henle, where the water and ions are reabsorbed from the proximal convoluted tubule. The descending limb of the loop of Henle is porous to water and transfers the filtrate deep into the medulla of the kidney. Compared to the filtrate, the tissues in the medulla, surrounding the tissues, a have a high concentration of s and very little water. The systemic pressure between the hypotonic filtrate and hypertonic medullary cells pushes water from the filtrate and into the cells. The cells of the medulla recover this water to the blood flowing through nearby capillaries.
Filtrate will then pass through – the ascending limb of the loop of the handle as it exits the medulla. The tissues encompassing the ascending limb are not permeable to water but are permeable to ions. The filtrate is very condensed after it passes through the descending limb, so ions easily diffuse out of the filtrate and within the cells lining the ascending limb. These ions to the blood flowing through nearby capillaries.
Tubular fluid leaving the loop of Henle will then pass through the distal convoluted tubule and the collecting duct of the nephron. These tables continue to absorb small amounts of water and ions that are still left in the filtrate. The tissues circling the collecting duct actively absorb excess ions as waste into the filtrate.
When filtrate reaches the end of the collecting duct, nearly all of the valuable nutrients water and ions have been returned to blood supply while waste products and small amounts of water are left behind to form urine. The urine leaves the collecting duct and mixes with urine from other collecting ducts in the renal pelvis.
The kidneys can control the volume of water in the body by changing the reabsorption of water by the tubules of the nephron. Standard conditions, the tubule cells of the phone is returned to the blood. ADH excites the formation of water flow proteins in the collecting ducts of the nephrons that allow water to pass through urine into the tubes cells and on to the blood. Aldosterone functions by increasing the reabsorption of CI- and NA+ ions, which causes more water into entering the blood via osmosis.
In certain circumstances where there is excessive water present in the blood, the heart will secrete the hormone atrial natriuretic peptide (ANP) to increase the excretion of NA+ and CI – ions. Increased concentration of Nat+ and CI- in urine draw water into the urine via osmosis, growing the volume of urine produced.
The kidneys regulate the pH level in the blood by controlling the excretion of hydrogen ions (H+) and bicarbonate ions (HCO3-). Hydrogen ions store when proteins are metabolized in the liver and when carbon dioxide in the blood response with water to form carbonic acid (H2CO3). Carbonic acid is a weak acid that partially separates in water to form hydrogen ions and bicarbonate ions. Both ions are removed out of the blood in the glomerulus of the Kidney, but though moving hydrogen ions as a waste product in urine. The table cells may also actively secret additional hydrogen ions into the urine when the blood becomes extremely acidic.
The reabsorbed bicarbonate ions penetrate the bloodstream where they can counterbalance hydrogen ions by creating new molecules of carbonic acid. Carbonic acid passing into the capillaries of the lungs separates into carbon dioxide and water, enabling us to exhale the carbon dioxide.
The kidneys control the homeostasis of essential electrolytes by collecting their extraction in urine.
Sodium ( Na+): Sodium is a necessary electrolyte for muscle function, neuron function, blood pressure regulation, and blood volume management. Over 99% of sodium ions passing through the kidneys are reabsorbed into the blood from the tubular filtrate. Most of thru reabsorption of sodium takes place in the proximal convoluted tubule and ascending loop of Henle.
Potassium (K+) Similar to sodium potassium is a vital electrolyte for neuron function, muscle function, and blood volume regulation. Unlike sodium, but, only about 60 to 80% of potassium ions moving through the kidneys are reabsorbed. Most of the reabsorption of potassium transpires in the proximal convoluted tubule and ascending loop of Henle.
Chloride( CI-): chloride is the most critical anion (negatively charged ion) in the body. Chloride is vital to the regulation of factors such as pH and cellular fluid stability and helps to build the electrical potential of neurons and muscle cells. The proximal convoluted tubule and ascending loop of Hele absorb about 90% of the chloride ions drained by the kidneys.
Not only is Calcium (Ca2+) one of the essential minerals in the body that compose the bones and teeth, it is also a vital electrolyte. Operating as an electrolyte, calcium is vital for the contraction of muscle tissue, the discharge of neurotransmitters by neurons, and the incitement of cardiac muscle tissue in the heart. The proximal convoluted tubule and the ascending loop of Henle will absorb most of the calcium in tubular filtrate into the blood again. Parathyroid hormone enhances the reabsorption of calcium in tubular filtrate into the blood. Parathyroid hormone increases the reabsorption of calcium in the kidneys when blood calcium levels become too low.
Magnesium (Mg2+): Magnesium ion is a crucial electrolyte for the most pop function of enzymes that work with phosphate compounds such as ATP, DNA, and RNA. The proximal convoluted tubule and loop of Henle reabsorb most of the magnesium that passes through the kidney.
Blood Pressure Homeostasis
The kidneys assist in regulating blood pressure in the body by regulating the secretion of sodium ions and water and by developing the enzyme renin. Because blood is mostly made of water, an increased volume of water in the body results in an expansion in the volume of blood in the blood vessels. Elevated blood volume means that the heart must pump harder than it typically does to push blood into vessels that are jammed with excess blood. Therefore increased blood volume leads to higher blood pressure. On the contrary, when the body is dehydrated, the volume of blood and blood pressure declines.
The kidneys can control blood pressure by either real boring water to maintain blood pressure or by providing more water than usual to be excreted into urine and thus reduce blood volume and pressure. Sodium ins the body help controls the osmotic pressure by drawing water toward areas of high sodium density. To lower blood pressure, the kidneys can eliminate extra sodium ions that draw water out of the body with them. Conversely, the kidneys may reabsorb additional sound ions to help retain water in the boy.
Finally, the kindly produce the enzyme renin to prevent the body’s blood pressure from shifting too low. The kidneys depend on a particular amount of blood pressure to force blood plasma through the capillaries in the glomerulus. If blood pressure becomes too low, cells low. Cell results in the release of the hormone aldosterone by the adrenal glands Aldosterone stimulate the cells of kidney to increase their reaction of sodium and water to maintain blood volume and pressure,