Kidney Functions and Nephrons

Flashcards for reviewing kidney functions, nephron structures, and urine creation.

Kidney Functions

Removes nitrogenous waste, regulates water volume, total solute concentration, extracellular fluids, long-term acid/base balance, eliminates toxins, drugs, and produces EPO and renin.

Kidney Blood Supply

Blood enters through renal arteries from the aorta and exits through renal veins to the inferior vena cava.

Renal Sinus

Enters and exits the renal hilum and includes ureters, blood vessels, and lymphatics.

Cortical Nephron

85% of nephrons, located almost entirely in the cortex; associated with peritubular capillaries.

Juxtamedullary Nephrons

Nephrons with loops that extend into the medulla; associated with vasa recta and responsible for concentrated urine.

Glomerulus

Fenestrated capillaries with high blood pressure that make filtrate.

Peritubular Capillaries

Low-pressure capillaries that reabsorb substances.

Vasa Recta

Capillaries that play a role in the salt gradient within juxtamedullary nephrons.

Juxtaglomerular Complex (JGC)

Contains the macula densa, granular cells, and extraglomerular mesangial cells.

Macula Densa

Tall, packed cells in the ascending limb that act as chemoreceptors sensing sodium chloride content of the filtrate.

Granular Cells

Mechanoreceptors in the afferent arteriole that sense blood pressure and secrete renin.

Extraglomerular Mesangial Cells

May pass signals between the macula densa and granular cells.

Urine Composition

95% water and 5% solutes.

Nitrogenous Wastes in Urine

Urea, uric acid, and creatinine.

Chronic Renal Disease

Kidney disease with GFR <60 mL/min for 3 months.

Renal Failure

Kidney disease with GFR <15 mL/min.

Cramps in Renal Disease

Caused by uremia and metabolic abnormalities, leading to fatigue.

Treatment for Renal Failure

Treated by kidney transplant and dialysis.

PCT (Proximal Convoluted Tubule)

Many microvilli for absorption and some secretion; active transport.

DCT (Distal Convoluted Tubule)

Few microvilli, much secretion, and less absorption.

Principal Cells

Reabsorb sodium and water, secrete potassium; regulated by aldosterone and ADH.

Filtrate

Plasma-derived fluid, cell-free.

Proteinuria

Protein in urine due to glomerulus holes being too big.

Kidney Supportive Tissue

Three layers: fibrous capsule, perirenal fat capsule, and renal fascia.

Fibrous Capsule

Closest layer, helps prevent the spread of infection.

Perirenal Fat Capsule

Fatty cushion to protect the kidney.

Renal Fascia

Anchors the kidney.

Hematuria

Blood in the urine.

Pyelitis

Infection in the renal pelves or calyces.

Pyelonephritis

Infection/inflammation of the kidney.

Afferent Arteriole

Highly pressurized vessel leading into the glomerulus.

Efferent Arteriole

Less pressurized vessel leading away from the glomerulus.

Glomerular Filtration Rate (GFR)

The rate at which filtrate is produced in the glomeruli; a key indicator of kidney function. Normal GFR is 120-125 mL/min

Tubular Reabsorption

The process by which water and solutes are reclaimed from the filtrate and returned to the blood. Occurs primarily in the PCT.

Tubular Secretion

The process by which substances are moved from the blood into the filtrate in the tubules. Important for eliminating drugs and toxins.

Countercurrent Mechanism

The interaction between filtrate flow in the ascending and descending limbs of the nephron loop, which establishes and maintains an osmotic gradient in the medulla.

Collecting Duct

Receives filtrate from many nephrons and plays a role in determining the final concentration of urine; target site for ADH.

Aldosterone

Hormone that increases sodium reabsorption (and potassium secretion) in the DCT and collecting duct.

ADH (Antidiuretic Hormone)

Hormone that increases water reabsorption in the collecting duct by inserting aquaporins into the membrane.

ANP (Atrial Natriuretic Peptide)

Hormone that reduces sodium reabsorption, leading to increased sodium and water excretion.

Renin-Angiotensin-Aldosterone System (RAAS)

A hormonal system that regulates blood pressure and fluid balance; involves renin secretion by granular cells.

Ureters

Tubes that carry urine from the kidneys to the bladder.

Urinary Bladder

A temporary storage reservoir for urine.

Urethra

Tube that carries urine from the bladder to the outside of the body.