Two kidneys, situated retroperitoneal in the abdominal cavity, Accessory organs (ureters, urinary bladder, urethra), The urethra (a tube that is responsible for eliminating urine from the bladder during micturition)

They are located on the posterior abdominal wall, They lie retroperitoneally (behind the peritoneum)

There are two kidneys, situated retroperitoneally, They lie laterally to the spinal column, Superiorly, they are in contact with the adrenal glands, They are supported by fatty and connective tissue

Inferior to the diaphragm, in the abdominal cavity, The upper extremity is higher (close to the diaphragm), in the left kidney

The upper extremity of the left kidney is higher than the upper extremity of the right kidney, Their medial surface has a concave area called renal hilum

Two distinct areas, cortical and medullary, A deep area, the renal medulla, represented by the renal pyramids, An external area, called cortex, containing renal glomeruli, parts of the nephron tubules and blood vessels

It contains the renal glomeruli and Bowman’s capsule, the afferent and the efferent arteriole and parts of the nephron tubules, It does not contain the loop of Henle, It is situated at the periphery of the kidney and sends projections to the renal medulla

It contains several triangular masses, the renal pyramids, It contains renal pyramids delimited by renal columns, It contains certain parts from the nephron structure (the loop of Henle) and the peritubular capillaries

The glomerulus, a capillary network resulting from the branching of the afferent arteriole, The glomerulus, capillary network which join together forming the efferent arteriole, The proximal convoluted tubule and the distal convoluted tubule

The afferent arteriole takes blood from the renal artery to the glomerulus, The afferent, microscopic, arterioles form the glomerular capillary network, The efferent arterioles form the peritubular capillary network, The peritubular capillaries drain into small veins which join together to form eventually the renal vein

The proximal convoluted tubule is situated in the renal cortex, The loop of Henle continues the proximal convoluted tubule and is U-shaped, The distal convoluted tubule continues the ascending branch of the loop of Henle

Filtration (the passage of small-molecule dissolved substances from the glomerular capillaries to the glomerular capsule), Reabsorption (the passage of water, salts and other substances from the tubule lumen into the peritubular capillaries), Tubular secretion (the passage of certain substances from the blood of peritubular capillaries into the distal convoluted tubule)

Is represented by the passage of fluid from blood plasma into the glomerular capsule through submicroscopic apertures, It pushes water and small plasma molecules out of the glomerular capillaries and into Bowman’s capsule

Its wall contains millions of microvilli which considerably enlarge the contact surface with the contents of the lumen, Glomerular filtrate arrives here and then leaves the glomerular capsule, Hosts the reabsorption process of certain ions

In the proximal convoluted tubule, By active transport (with ATP uptake)

Glomerular filtrate from the proximal convoluted tubule enters the descending branch of the loop (after the selective reabsorption in the proximal tubule), Na+ and Cl- pass into the medullary interstitium in the ascending branch, where the fluid in the tubule flows

No water reabsorption takes place in it (or only very small amounts), It enables sodium and chloride ion reabsorption, It ascends from the medulla back to the cortex

The selective reabsorption of ions by active transport, The reabsorption of water under the influence of ADH, Secretion of certain medicines and certain hormones

Takes place in the nephron tubules (especially in the distal convoluted tubule) and in the collecting ducts, Is an active process which transports chemical compounds from the bloodstream into the tubular fluid, Transports certain chemical compounds from the peritubular capillaries into the tubular fluid

The glomerulus and the glomerular capsule are responsible with filtering blood plasma, Glucose and amino acid reabsorption takes place in the proximal tubules, The secretion of certain medicines takes place in the distal tubules, Sodium is reabsorbed by active transport in the ascending branch of the loop of Henle

It is secreted by the cortex of the adrenal glands and mainly influences the nephron’s distal convoluted tubule, It stimulates sodium ion reabsorption from the distal convoluted tubule, It stimulates the secretion of blood potassium in the distal convoluted tubule fluid

Pigments, the most important being urobilinogen, produced by bilirubin in the bowel, Hormones and various medicines, Urea, synthesized in the liver by amino acid metabolism and the use of their amino (-NH2) groups

Potassium and sodium are monovalent cations, Calcium (Ca2+) and magnesium (Mg2+) belong to cations and are bivalent, Sulphate ion and chloride ion are anions

Its inferior part opens in the urinary bladder, Its superior part continues the renal pelvis, It is a long tube which carry urine to the urinary bladder