urinary system

What are the main functions of the kidneys?

Removal of toxins, regulation of blood volume & pH, gluconeogenesis, and endocrine functions including renin and erythropoietin.

Where are the kidneys located?

The kidneys are located retroperitoneally in the superior lumbar region.

What happens when perirenal fat is depleted?

It removes a protective cushion, increasing the risk of kidney injury or displacement.

What is the renal hilum?

The medial indentation where ureters, blood vessels, lymphatics, and nerves enter/exit the kidney.

What is the role of the renal cortex?

It is the granular superficial region where filtration begins.

What is the role of the renal medulla?

It contains renal pyramids involved in concentrating urine.

What is the sequence of blood flow through the renal artery to the afferent arteriole?

Aorta → Renal artery → Segmental artery → Interlobar artery → Arcuate artery → Cortical radiate artery → Afferent arteriole.

What is the difference between afferent and efferent arterioles?

Afferent arterioles bring blood into the glomerulus, while efferent arterioles take blood away from the glomerulus.

How does constriction of afferent and efferent arterioles affect filtration?

Afferent constriction decreases GFR; efferent constriction increases glomerular pressure boosting filtration.

What are glomerular capillaries specialized for?

They are specialized for filtration due to high pressure.

What are the functions of peritubular capillaries?

They are ideal for absorption and secretion, surrounding the renal tubule.

What is the vasa recta?

Long, straight capillaries that assist in forming concentrated urine and maintaining the osmotic gradient in the medulla.

Which parts of the nephron are located in the cortex?

Renal corpuscle, proximal convoluted tubule, and distal convoluted tubule.

Which parts of the nephron are located in the medulla?

Loop of Henle and collecting ducts.

What are the three major steps in urine formation?

1. Glomerular Filtration, 2. Tubular Reabsorption, 3. Tubular Secretion.

What does the juxtaglomerular apparatus (JGA) do?

It regulates filtrate formation and blood pressure.

What are the components of JGA?

Macula densa, granular cells, and extraglomerular mesangial cells.

What is the filtration membrane?

The barrier between the blood in the glomerulus and the filtrate in the capsule.

What are the three layers of the filtration membrane?

1. Fenestrated endothelium, 2. Basement membrane, 3. Foot processes of podocytes.

How is Net Filtration Pressure calculated?

NFP = HPg – (OPg + HPc), where HPg = glomerular hydrostatic pressure.

What is GFR?

The amount of filtrate made per minute by both kidneys, normally 120–125 mL/min.

What factors affect GFR?

Surface area, permeability of the filtration membrane, and net filtration pressure.

What is transcellular reabsorption?

Movement of substances through the tubule cell from filtrate back to blood.

What is paracellular reabsorption?

Movement of substances between tubule cells, limited to water and some ions.

Which nephron parts primarily handle secretion?

Mainly the distal convoluted tubule (DCT) and collecting duct.

Which nephron parts are mostly involved in reabsorption?

Proximal convoluted tubule (PCT), Loop of Henle, DCT, and collecting duct.