In humans, the urinary system consists of
A pair of kidneys,
One pair of ureters,
An urinary bladder
An urethra.
Urinary System Parts _kidney
Kidneys are reddish brown, bean shaped structures situated between the levels of last thoracic and third lumbar vertebra close to the dorsal inner wall ofthe abdominal cavity. Each kidney of an adult human measures 10-12 cm inlength, 5-7 cm in width, 2-3 cm in thickness with an average weight of 120-170 g. Towards the centre of the innerconcave surface of the kidney is a notch called hilum through which ureter, blood vessels and nerves enter. Inner to the hilumis a broad funnel shaped space called the renal pelvis with projections called calyces.The outer layer of kidney is a tough capsule. Inside the kidney, there are two zones, an outer cortex and an inner medulla. The medulla is divided into a few conical masses called medullary pyramids projecting into the calyces.The cortex extends in between themedullary pyramids as renal columns called Columns of Bertini .Renal artery carry impure blood for purification towards kidney and renal vein carry pure blood away from kidney.
Other Parts of Urinary System
Ureter:From the hilum of each kidney emerges a slender,whitish tube,the ureter.It is about 28cm in length.Ureter carry urine from kidney to urinary bladder
Urinary bladder:It is a median pear shaped sac situated in the pelvic region of the abdominal cavity within the front body wall.It is thick muscular,distensible lined by transitional epithelium.bladder can hold about 700-800ml of urine temporarily.
Urethra:The urethra starts from the lower part of urinary bladder and leads to the exterior.It helps in micturition.
Left suprarenal gland: cap covering the upper part of the left kidney.
Common iliac vein: vein carrying unoxygenated blood from the limbs and lower organs to the heart.
Celiac trunk: branching of the aorta feeding the abdominal viscera.
Left kidney: left blood-purifying organ.
Left renal vein: vein connecting the left kidney and the inferior vena cava.
Abdominal aorta: part of the aorta feeding the organs of the abdomen.
Erethra: small tube through which a human being expels liquid waste.
Iliac vein and artery: blood vessels in the flank region.
Ureter: tube carrying urine from the kidney to the bladder.
Renal pelvis: part of the kidney situated at the junction of the calyces and leading to the ureter.
Malpighi's pyramid: glomerules of the kidney.
Calyx: excretory cavity in the pelvis of a kidney.
Medulla: matter forming the central part of a kidney.
Cortex: matter of the cortex of the suprarenal gland.
Section of the right kidney: graphic representation of the interior of the right blood-purifying organ.
Section of the right suprarenal gland: graphic representation of the interior of the suprarenal gland.
Urinary System_structure of Nephrone
Each kidney has nearly one million complex tubular structures called nephrons, which are the functional units.Each nephron has two parts – the glomerulus and the renal tubule.Glomerulus is a tuft of capillaries formed by the afferent arteriole – a fine branch of renal artery. Blood from the glomerulus is carried away by an efferent arteriole.The renal tubule begins with a double walled cup-like structure called Bowman’scapsule, which encloses the glomerulus.Glomerulus along with Bowman’s capsule, is called the malpighian body or renal corpuscle . The tubule continues further to form a highly coiled network – proximal convoluted tubule(PCT). A hairpin shaped Henle’s loop is the next part of the tubule which has a descending and an ascending limb. The ascending limb continues as another highly coiled tubular region called distal convoluted tubule (DCT). The DCTs of many nephrons open into a straight tube called collecting duct, many of which converge and open into the renal pelvis through medullary pyramids in the calyces.The Malpighian corpuscle, PCT and DCT of the nephron are situated in the cortical region of the kidney whereas the loop of Henle dips into the medulla. In majority of nephrons, the loop of Henle is too short and extends only very little into the medulla. Such nephrons are called cortical nephrons. In some of the nephrons, the loop of Henle is very long and runs deep into the medulla.These nephrons are called juxta medullary nephrons. The efferent arteriole emerging from the glomerulus forms a fine capillary network around the renal tubule called the peritubular capillaries. A minute vessel of this network runs parallel to the Henle’sloop forming a ‘U’ shaped vasa recta. Vasa recta is absent or highly reduced in cortical nephrons
