The organs of the body which are concerned with the formation of urine and it’s elimination from the body are referred as the urinary organs in the human urinary system. Urine is formed in the kidneys, there are two numbers of kidney in human body, the left and the right kidneys. Other parts of the urinary organs are the left and right Ureters , the urinary bladder, in which urine is stored and the urethra which carries urine from urinary bladder to the opening.
Each kidney has a convex lateral margin and a concavity on the medial side which is called hilum. So each kidney has a characteristic bean like shape. At the hilum the terminal branches of renal artery enter into the kidney, and the veins emerge from it. The upper expanded end of the ureter also has the attachment to the hilum. Due tithe pressure of the liver on the right side the right kidney lies slightly lower than the left kidney. The hilum of each kidney lies nearly in the transpyloric plane. The upper end is about 2.5 cm from the median plane, while the lower end is about 7.5 cm from it. It’s medial and lateral boundaries are formed by vertical lines 2.5 cm and 9 cm from the median plane.
Each kidney rests on diaphragm, and the diaphragm separates the upper part of the kidney from the pleura and from the twelfth rib. The left kidney as it is higher than the right, is also separated from the diaphragm from the eleventh rib. The relation of the anterior surface of the right kidney is that the medial part is overlapped by the right colic flexure. Above the right colic flexure the surface is in contact with the visceral surface of the liver. On the other hand the upper lateral part of the left kidney is in contact with the renal impression on the spleen. The pancreas runs across the middle of the anterior surface. The left colic flexure comes in contact with the lower lateral part of the anterior surface. Just above the area for the pancreas the anterior surface of the left kidney comes in contact with the stomach.
The renal vein, the renal artery and the renal pelvis enter or leave the kidney at the hilum. The vain is most anterior, the artery is in the middle and the pelvis is most posterior. Hilum leads in to a space called the renal sinus. The renal sinus is occupied by the upper expanded part of the ureter called by renal pelvis. The pelvis divides in to two parts with I the renal sinus called major calices. Each major calyx decides into a number of minor calices. The end of each minor calyx is shaped like a cup and a projection of kidney tissue called the papilla fits into it.
The papillae are the apical parts of triangular areas of renal tissue called the renal pyramids . In the human urinary system the number of pyramids in a kidney is variable though the average number is eight. As the apex or the papilla of one pyramid fits into one minor calyx the number of pyramids is equal to that of the calices. The tissues of the kidney lying between the bases of the pyramids and the surface of the kidney is the cortex. The extensions of the cortex which reside in the intervals between the adjacent pyramids are called the renal columns. The kidney tissue is closely covered by a thin layer of fibrous tissue is called the renal capsule. Beyond the capsule the kidney is surrounded by a layer of perinephric fat which is sualso surrounded by a layer of fibrous tissue that form renal fascia.
The both of the ureter is a long tube which connects the lower end of the renal pelvis with the urinary bladder. It is about 25 cm in length and the upper half of this length lies on the posterior abdominal wall and the lower half in the true pelvis. The abdominal portion of each ureter runs downwards. At the brim of the pelvis the ureter crosses the upper end of the external iliac artery and comes to lie on the lateral wall of the pelvis. And finally it leaves the pelvic wall and turns medially and ahead to reach the posterolateral part of the urinary bladder.
The urinary bladder is a muscular sac in the pelvis, just above and behind of the pubic bone. The urine, which is formed in the kidney, comes down by the ureter and reaches to the bladder. In human urinary system the urinary bladder stores urine, allowing urination to be infrequent voluntary. A layer of muscle tissue which lined the bladder that stretches to accommodate the urine. Normally the capacity of the bladder is 400 to 600 ml. The bladder muscles contract and two sphincters open to flow the urine during urination. Urine exits the bladder into the urethra. The urethra in men is about 20 cm long where in women it is about 4 cm in length. The urethra carries the urine out of the body.