Biology: Homeostasis and Excretion

The kidneys regulate the volume and composition of blood, ensuring a stable internal environment.

Kidneys maintain the balance of electrolytes, like sodium, potassium, and calcium, essential for various bodily functions.

The kidneys eliminate waste products from metabolism, including urea and creatinine, preventing their buildup in the body.

The kidneys are responsible for producing hormones like erythropoietin, which stimulates red blood cell production, and renin, which regulates blood pressure.

The kidneys conserve essential nutrients, reabsorbing them back into the bloodstream to prevent their loss.

Microscopic units in the kidney responsible for filtering blood and producing urine.

The two types of nephrons are cortical nephrons, which are shorter and more numerous, and juxtamedullary nephrons, which are longer and help regulate water balance.

A double-walled, cup-shaped structure that surrounds the glomerulus, where filtration of blood begins.

The coiled portion of the nephron tubule closest to Bowman's capsule, where most reabsorption of nutrients and water occurs.

The descending loop of Henle is responsible for water reabsorption, while the ascending loop of Henle reabsorbs salts.

The collecting duct receives urine from multiple nephrons and carries it to the renal pelvis.

The renal artery carries oxygenated blood to the kidney, while the renal vein carries deoxygenated blood away from the kidney.

The hilus is the indented region of the kidney where the renal artery, renal vein, and ureter enter and exit.

A funnel-shaped structure inside the kidney that collects urine from the nephrons.

The tube that carries urine from the kidney to the bladder.

A muscular sac that stores urine before it is expelled from the body.

The tube that carries urine from the bladder to the outside of the body.

A network of capillaries within the nephron where blood filtration occurs.

The afferent arteriole is a blood vessel that carries blood to the glomerulus in the kidney. It is responsible for delivering oxygenated blood and nutrients to the nephrons, the functional units of the kidney.

The efferent arteriole is a blood vessel that carries blood away from the glomerulus in the kidney. It takes the filtered blood and transports it to the peritubular capillaries, where further reabsorption and secretion of substances occur.

The high blood pressure in the glomerulus is due to the pumping action of the heart and the narrow diameter of the efferent arteriole compared to the afferent arteriole. This pressure gradient drives filtration, forcing water and small solutes into Bowman's capsule.

The process by which the kidneys return useful substances from the glomerular filtrate back into the bloodstream.

The rate at which glomerular filtrate is formed in the kidneys, approximately 125 ml per minute.

The amount of glomerular filtrate lost as urine per minute, approximately 1 ml.

The movement of substances from the glomerular filtrate back into the bloodstream through the process of diffusion, osmosis, and active transport.

A section of the nephron where the final adjustments to electrolyte and water balance take place before urine is formed.

The proximal convoluted tubule (PCT) has a highly folded structure with many convolutions, increasing the surface area for reabsorption of useful substances from the filtrate.

The PCT is highly convoluted to maximize the time the filtrate spends within the tubule, allowing for greater opportunity for reabsorption of valuable substances.

The single layer of cells in the PCT wall ensures a short diffusion distance for reabsorption of useful substances from the filtrate back into the bloodstream.

The numerous mitochondria present in the PCT cells power the active transport processes involved in reabsorption of valuable substances against their concentration gradients.

The PCT is responsible for reabsorbing most of the water and nutrients from the filtrate, returning them back into the bloodstream to prevent loss.

The structural features of the PCT, such as its convolutions, single layer of cells, and abundant mitochondria, work together to facilitate efficient reabsorption of valuable substances from the filtrate.