Renal Function - Chapter 26

These flashcards cover key vocabulary and concepts related to renal function, including anatomy, nephron structure, kidney functions, and fluid regulation.

Nephron

The basic structural and functional unit of the kidney, each kidney contains more than one million.

Glomerulus

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

Bowman's Capsule

A cup-like sac that surrounds the glomerulus and collects glomerular filtrate.

Cortex

The outer portion of the kidney where glomeruli and nephron tubules are located.

Medulla

The middle portion of the kidney that contains renal pyramids.

Renal Pelvis

The funnel-shaped structure that collects urine from the renal pyramids and leads to the ureter.

Ureter

A duct that carries urine from the kidney to the urinary bladder.

Efferent Arteriole

The blood vessel that carries blood away from the glomerulus.

Afferent Arteriole

The blood vessel that carries blood to the glomerulus.

Filtration Fraction

The percentage of plasma that is filtered through the glomerulus, about 20%.

Net Filtration Pressure (NFP)

The total pressure that promotes filtration, calculated as GBHP - (CHP + BCOP).

Glomerular Filtration Rate (GFR)

The rate at which the kidney filters blood, typically > 187,000ml/day.

Tubular Reabsorption

The process by which substances are reabsorbed from the renal tubules back into the blood.

Tubular Secretion

The process that moves substances from the blood into the renal tubules.

Urethra

The tube through which urine exits the urinary bladder.

Nitrogenous Waste

Waste products from protein metabolism, including ammonia, urea, and uric acid.

Hormonal Function of Kidneys

The kidneys are involved in processes such as vitamin D metabolism and erythropoietin production.

Urine Formation

The process by which the kidneys produce urine to eliminate toxic wastes.

Reabsorption in Proximal Convoluted Tubule (PCT)

Reabsorbs about two-thirds of filtered water and electrolytes, and all glucose, amino acids, and vitamins using sodium-dependent transporters and the Na⁺/K⁺ pump; It is the major site of reabsorption in the nephron.

Renal Vein

The vessel that carries filtered blood away from the kidney back to the circulation.

Renal Artery

The blood vessel that supplies blood to the kidneys.

Filtration Membrane

A 3-layer barrier (fenestrated endothelium, basement membrane, podocyte slit diaphragm) that prevents cells + large proteins from filtering into Bowman’s capsule.

Glomerular Blood Hydrostatic Pressure (GBHP)

The blood pressure inside glomerular capillaries that promotes filtration.

Capsular Hydrostatic Pressure (CHP)

Pressure exerted by fluid in Bowman’s capsule that opposes filtration.

Blood Colloid Osmotic Pressure (BCOP)

Osmotic pull of plasma proteins in glomerular capillaries that opposes filtration.

Tubuloglomerular Feedback

A mechanism where the macula densa senses NaCl levels in the distal tubule and adjusts GFR by signaling the juxtaglomerular apparatus to constrict or dilate arterioles.

Mesangial Cell Contraction

Cells within the glomerulus that contract to reduce filtration surface area, decreasing GFR.

Loop of Henle - Countercurrent Mechanism

The loop creates a high medullary osmolarity that allows the kidneys to produce concentrated urine; Descending limb = water reabsorption; Ascending limb = active Na+/K+/2Cl- pumping.

Distal Convoluted Tubule (DCT) Function

“Fine-tunes” sodium, water, and electrolyte balance under the influence of aldosterone, ADH, ANP, and Angiotensin II (AII).

Collecting Duct Function

Final site for water and solute regulation; Permeability to water increases in the presence of ADH.

Antidiuretic Hormone (ADH)

Increases collecting duct water permeability — concentrated urine and decreased plasma osmolality.

Aldosterone

Hormone that increases Na+ reabsorption and K+ secretion in the distal nephron — increases blood volume (but NOT osmolality).

Atrial Natriuretic Peptide (ANP)

Hormone that inhibits Na+ and water reabsorption and lowers blood volume + pressure.

Renin-Angiotensin-Aldosterone System (RAAS)

System that increases blood pressure and GFR by vasoconstriction and stimulating aldosterone release.

Bicarbonate Reabsorption (Carbonic Anhydrase System)

HCO3- is reabsorbed after conversion to CO2 by carbonic anhydrase; Kidneys regulate acid-base balance by secreting H+ and regenerating bicarbonate.

Urine Buffers (HPO4²- and NH3)

Bind H+ in the urine, allowing kidneys to excrete larger acid loads.

Urea Recycling

Urea ia filtered, partly reabsorbed, and helps maintain the high medullary osmotic gradient for water reabsorption.

Creatinine Clearance

A measurement used to estimate GFR, since creatinine is freely filtered and minimally secreted.

Endocrine Functions of the Kidney

Include secretion of erythropoietin, activation of vitamin D, and production of renin.

Age-Related Renal Changes

Infants cannot concentrate urine well; Elderly have decreased nephron number, GFR, and ability to conserve salt and water.