Excretory System and Urine Production Vocabulary

Vocabulary practice flashcards covering organ functions in excretion, deamination reactions, nitrogenous wastes, detailed renal anatomy, nephron structure, and urine production processes.

Excretion

The biological process of removing metabolic waste products from the body before they accumulate and reach toxic concentrations.

Deamination

The chemical process occurring in the liver where the enzyme deaminase removes the amino group ($\text{NH}_2$) from an amino acid molecule.

Deaminase

The liver enzyme that catalyzes the removal of an amino group ($\text{NH}_2$) from an excess amino acid during deamination.

Ammonia

A highly cell-toxic nitrogenous compound ($\text{NH}_3$) produced during deamination that is rapidly converted by the liver into urea.

Urea

A nitrogenous waste product with moderate toxicity produced in the liver from ammonia and carbon dioxide at approximately $21\,\text{g/day}$, excreted by the kidneys in urine and sweat glands in sweat.

Uric Acid

A weakly toxic nitrogenous waste product excreted at about $480\,\text{mg/day}$, formed from the metabolic breakdown of purines from cell destruction and dietary sources.

Creatinine

A highly toxic nitrogenous waste product produced at about $1.8\,\text{g/day}$ in muscle tissue from the breakdown of creatine phosphate.

Lungs (Excretory Role)

Excretory organs responsible for removing carbon dioxide, a toxic metabolic by-product generated during cellular respiration.

Liver (Excretory Role)

An organ that processes chemicals into safer forms, detoxifies alcohol and drugs, deactivates hormones, and converts hemoglobin into bile pigments for excretion.

Sweat Glands

Excretory structures in the skin that produce approximately $500\,\text{mL}$ of sweat per day to eliminate water, sodium chloride, lactic acid, urea, and trace drugs.

Bile Pigments

Excretory substances produced by the liver from the breakdown of hemoglobin in dead red blood cells and eliminated via the alimentary canal.

Nephron

The microscopic functional unit of the kidney responsible for forming urine, with approximately $1.2\text{ million}$ present in each human kidney.

Renal Corpuscle

The initial blood-filtering structure of a nephron located in the cortex, consisting of the glomerulus wrapped by Bowman's capsule.

Glomerulus

A knot of tangled capillaries within the renal corpuscle supplied by the afferent arteriole and drained by the efferent arteriole.

Bowman's Capsule

A double-walled sac surrounding the glomerulus that captures fluid plasma pushed out of the blood during glomerular filtration.

Afferent Arteriole

The wider blood vessel that supplies high-pressure blood into the glomerulus of a nephron.

Efferent Arteriole

The narrow blood vessel through which blood leaves the glomerulus before forming the peritubular capillary network.

Peritubular Capillaries

A complex meshwork of capillaries wrapping around the renal tubules that facilitates selective reabsorption and tubular secretion.

Glomerular Filtration

The process driven by high blood pressure in the glomerulus that forces $20\%$ of blood plasma (water and small dissolved molecules) into Bowman's capsule.

Filtrate

The liquid captured in Bowman's capsule produced at approximately $125\,\text{mL/min}$ ($180\,\text{L/day}$), containing water, urea, glucose, amino acids, vitamins, and salts, but lacking blood cells and large proteins.

Selective Reabsorption

The movement of useful substances and water from the tubular filtrate back into the bloodstream via peritubular capillaries, returning roughly $99\%$ of filtrate to the body.

Tubular Secretion

The active transport of un-filtered substances (such as hydrogen ions, ammonium, creatinine, potassium ions, and penicillin) from peritubular capillaries into the renal tubules.

Proximal Convoluted Tubule (PCT)

The renal tubule section lined with microvilli (brush border) where $100\%$ of glucose, $100\%$ of amino acids, and major portions of water and salts are reabsorbed.

Loop of Henle

A U-shaped tubule segment extending into the renal medulla responsible for reabsorbing water and salts ($\text{Na}^+/\text{Cl}^-$).

Distal Convoluted Tubule (DCT)

The tubule section where active reabsorption of sodium ions and variable water reabsorption occur, along with active secretion of hydrogen and potassium ions to maintain blood pH ($7.4\text{--}7.5$).

Collecting Duct

The final tubule segment receiving fluid from multiple nephrons that actively reabsorbs water based on bodily needs before discharging urine into the calyces.

Renal Cortex

The outer region of the kidney containing the renal corpuscles, proximal convoluted tubules, and distal convoluted tubules.

Renal Medulla

The inner region of the kidney composed of renal pyramids, loops of Henle, and collecting ducts.

Renal Pyramids

Triangular tissue segments in the renal medulla separated by cortical extensions known as renal columns.

Renal Pelvis

A central funnel-shaped kidney cavity that collects urine from the calyces and directs it into the ureter.

Ureter

A muscular tube that carries urine from the renal pelvis to the urinary bladder via peristaltic waves over a length of $25\text{--}30\,\text{cm}$.

Urinary Bladder

A hollow muscular organ that temporarily stores urine prior to excretion.

Urethra

The terminal tube that carries urine from the urinary bladder to the exterior of the body.

Urine

An amber fluid composed of $95\%$ water, $2\%$ urea, $0.6\%$ chloride, and other dissolved solutes, voided at an average 24-hour volume of $1\text{, }200\,\text{cm}^3$ ($1.2\,\text{L}$).