Kidneys Anatomy and Structure

Kidneys are paired organs situated retroperitoneally in the upper part of the abdominal cavity, attached to the posterior abdominal wall, generally corresponding to the T12-L3 vertebral level.

Kidneys are roughly 10 cm (length) x 5 cm (width) x 2.5 cm (thickness).

The indented area on the medial surface of the kidney where the renal artery, renal vein, and renal pelvis enter and exit.

A large internal space or cavity within the kidney, containing the renal pelvis and structures associated with urine collection.

A funnel-shaped structure in the kidney that collects urine from the calyces. It is the proximal dilation of the ureter.

The outer layer of the kidney.

The inner layer of the kidney, containing renal pyramids.

Approximately 10% of the circulating blood flows through the kidneys.

Located in the cortex of the kidney.

Located in the medulla of the kidney.

Located in the cortex of the kidney.

Visceral layer (podocytes) and parietal layer (simple squamous epithelium).

Simple cuboidal cells with microvilli for increased absorption and secretion.

Descending and ascending limbs, including thin and thick segments in juxtamedullary nephrons.

Structure regulating blood pressure in the kidneys, formed by macula densa and afferent arteriole.

Cells in distal convoluted tubules responding to hormones ADH and aldosterone.

Process of reclaiming useful substances from the filtrate.

Where distal convoluted tubules empty into, directing urine formation.

The process where blood is filtered in the glomerulus, separating water and small solutes from blood cells and large proteins.

The rate at which filtrate is produced in all nephrons per minute, approximately 125 ml/min for males and 105 ml/min for females.

The pressure difference that drives filtration in the glomerulus, calculated as the glomerular blood hydrostatic pressure minus the capsular hydrostatic pressure and blood colloid osmotic pressure.

The ability of the kidneys to adjust blood flow and GFR in response to blood pressure changes.

Increased blood pressure stretches the afferent arterioles, causing vasoconstriction which reduces blood flow and maintains GFR.

Sympathetic stimulation restricts blood flow to the kidneys by vasoconstriction, preserving blood volume and diverting blood to other organs.

Angiotensin II reduces GFR by constricting the efferent arteriole, thereby decreasing blood flow through the glomerulus.

ANP, released from the heart when blood volume increases, increases GFR by promoting vasodilation of afferent arterioles and reducing the reabsorption of sodium and water.

The process of moving essential substances from the filtrate back into the bloodstream.

The process of transporting wastes and excess substances from the blood into the filtrate for excretion.

Blood vessels that directly branch from the abdominal aorta and supply blood to the kidneys. They enter the kidney through the hilum.

Found within the kidney, these arteries branch from the renal arteries and carry blood towards the cortex between renal pyramids.

These arteries curve between the cortex and medulla within the kidney, supplying blood to these regions.

Smallest branches of the arcuate arteries, found within the cortex of the kidney, supplying blood to the nephrons.

A specialized arteriole that branches from the interlobular arteriole and carries blood to the glomerulus for filtration.

Specialized capillaries within the glomerulus where blood filtration takes place, forming the filtrate.

Arteriole that carries blood away from the glomerulus after filtration, leading to peritubular capillaries for reabsorption.

Capillaries surrounding the tubules of the nephron, responsible for reabsorbing essential nutrients and water back into the blood.

The PCT is where most of the reabsorption of water, electrolytes, nutrients, and other substances occurs, returning them to the bloodstream. Important examples include 65% water reabsorption via osmosis, 65% Na and K ions, 100% glucose and amino acids, and 50% urea.

Veins within the kidney's cortex, collecting blood from the peritubular capillaries.

Muscular tubes that transport urine from the renal pelvis to the urinary bladder.

The loop of Henle further reabsorbs water and solutes, playing a crucial role in concentrating urine. The descending limb reabsorbs mostly water, while the ascending limb reabsorbs Na, K, and Cl. Notably, water reabsorption is minimal in the ascending limb.

The DCT fine-tunes urine composition by reabsorbing remaining water, sodium, chloride, and variable amounts of calcium. Parathyroid hormone stimulates calcium reabsorption.

Located in the late DCT and collecting duct, principal cells reabsorb water, sodium, and variable amounts of urea. They are also responsible for potassium secretion.

These cells contribute to acid-base balance by reabsorbing bicarbonate and secreting hydrogen ions, playing a crucial role in maintaining pH.