The urinary system consists of two kidneys, two ureters, the urinary bladder, and a urethra.
This system forms and eliminates urine, which contains metabolic waste products.
The kidneys,: the organs of excretion, also regulate the composition, volume, and acid–base balance (pH) of body fluids.
kidneys are located behind the peritoneum in the lumbar region. On the top of each kidney rests an adrenal gland. Each kidney is encased in a capsule of fibrous connective tissue overlaid with fat. An outermost layer of connective tissue supports the kidney and anchors it to the body wall. The kidney has an outer region, the renal cortex, and an inner region, the renal medulla. The medulla is divided into triangular sectionss, each called a pyramid. The pyramids have a lined appearance because they are made up of the loops and collecting tubules of the nephrons, the functional units of the kidney. Each collecting tubule empties into a urine-collecting area called a calyx (from the Latin word meaning “cup”). Several of these smaller minor calyces merge to form a major calyx. The major calyces then unite to form the renal pelvis, the upper funnel-shaped portion of the ureter. The Nephrons The tiny working units of the kidneys are the nephrons. Each of these microscopic structures is basically a single tubule coiled and folded into various shapes. At the beginning of the tubule is the cupshaped Bowman capsule, which is part of the blood-filtering device of the nephron.
The tubule then folds into the proximal convoluted tubule, straightens out to form the loop of Henle, coils again into the distal convoluted tubule, and then finally straightens out to form a collecting tubule. Urine Formation As blood flows through the glomerulus, blood pressure forces materials to follow through the glomerular wall and through the wall of the glomerular capsule into the nephron. The fluid that enters the nephron, the glomerular filtrate, consists mainly of water, electrolytes, soluble wastes, nutrients, and toxins. The main waste material is urea, the nitrogenous (nitrogen-containing) byproduct of protein metabolism. The filtrate should not contain any cells or proteins such as albumin. The waste material and the toxins must be eliminated, but most of the water, electrolytes, and nutrients must be returned to the blood or we would rapidly starve and dehydrate. This return process, termed tubular reabsorption, occurs through the peritubular capillaries that surround the nephron. As the filtrate flows through the nephron, other processes further regulate its composition and pH. The concentration of the filtrate is also adjusted under the effects of the pituitary hormone antidiuretic hormone (ADH). Finally, the filtrate, now called urine, flows into the collecting tubules to be eliminated. Urine Removal Urine is drained from the renal pelvis and carried by the ureter to the urinary bladder. Urine is stored in the bladder until fullness stimulates a reflex contraction of the bladder muscle and expulsion of urine through the urethra. The female urethra is short (4 cm; 1.5 in) and carries only urine. The male urethra is longer (20 cm; 8 in) and carries both urine and semen. The voiding (release) of urine, technically called micturition or urination, is regulated by two sphincters (circular muscles) that surround the urethra. The upper sphincter, just below the bladder, functions involuntarily, the lower sphincter is under conscious control. Drinking water for 2-3 liter a day is very important .for more imformation about kidneys go back to our previous chapter. Or click here to read it in hausa.and don't forget to leave your comment, below.
kidneys are located behind the peritoneum in the lumbar region. On the top of each kidney rests an adrenal gland. Each kidney is encased in a capsule of fibrous connective tissue overlaid with fat. An outermost layer of connective tissue supports the kidney and anchors it to the body wall. The kidney has an outer region, the renal cortex, and an inner region, the renal medulla. The medulla is divided into triangular sectionss, each called a pyramid. The pyramids have a lined appearance because they are made up of the loops and collecting tubules of the nephrons, the functional units of the kidney. Each collecting tubule empties into a urine-collecting area called a calyx (from the Latin word meaning “cup”). Several of these smaller minor calyces merge to form a major calyx. The major calyces then unite to form the renal pelvis, the upper funnel-shaped portion of the ureter. The Nephrons The tiny working units of the kidneys are the nephrons. Each of these microscopic structures is basically a single tubule coiled and folded into various shapes. At the beginning of the tubule is the cupshaped Bowman capsule, which is part of the blood-filtering device of the nephron.
The tubule then folds into the proximal convoluted tubule, straightens out to form the loop of Henle, coils again into the distal convoluted tubule, and then finally straightens out to form a collecting tubule. Urine Formation As blood flows through the glomerulus, blood pressure forces materials to follow through the glomerular wall and through the wall of the glomerular capsule into the nephron. The fluid that enters the nephron, the glomerular filtrate, consists mainly of water, electrolytes, soluble wastes, nutrients, and toxins. The main waste material is urea, the nitrogenous (nitrogen-containing) byproduct of protein metabolism. The filtrate should not contain any cells or proteins such as albumin. The waste material and the toxins must be eliminated, but most of the water, electrolytes, and nutrients must be returned to the blood or we would rapidly starve and dehydrate. This return process, termed tubular reabsorption, occurs through the peritubular capillaries that surround the nephron. As the filtrate flows through the nephron, other processes further regulate its composition and pH. The concentration of the filtrate is also adjusted under the effects of the pituitary hormone antidiuretic hormone (ADH). Finally, the filtrate, now called urine, flows into the collecting tubules to be eliminated. Urine Removal Urine is drained from the renal pelvis and carried by the ureter to the urinary bladder. Urine is stored in the bladder until fullness stimulates a reflex contraction of the bladder muscle and expulsion of urine through the urethra. The female urethra is short (4 cm; 1.5 in) and carries only urine. The male urethra is longer (20 cm; 8 in) and carries both urine and semen. The voiding (release) of urine, technically called micturition or urination, is regulated by two sphincters (circular muscles) that surround the urethra. The upper sphincter, just below the bladder, functions involuntarily, the lower sphincter is under conscious control. Drinking water for 2-3 liter a day is very important .for more imformation about kidneys go back to our previous chapter. Or click here to read it in hausa.and don't forget to leave your comment, below.
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