Chapter 23: The Urinary System

Flashcards covering the vocabulary of the urinary system.

Urinary System

The system consists of two kidneys, two ureters, the urinary bladder, and the urethra.

Kidney Functions

Filter the blood plasma and eliminate wastes, regulate blood volume, pressure, and osmolarity. Also regulate electrolyte and acid-base balance.

Erythropoietin

Stimulates the production of RBCs.

Kidney's Role in Calcium

Helps regulate calcium homeostasis and bone metabolism by participating in the synthesis of calcitriol.

Waste

A substance that is useless or present in excess of the body’s needs.

Metabolic Waste

A waste substance produced by body processes.

Nitrogenous Wastes

Waste consisting of urea, uric acid, and creatinine.

Urea

A by-product of protein catabolism.

Blood Urea Nitrogen (BUN)

Measure of the level of nitrogenous waste in the blood.

Azotemia

Elevated BUN

Uremia

Condition with symptoms stemming from nitrogenous waste toxicity: diarrhea, vomiting, dyspnea, and cardiac arrhythmia.

Excretion

The process of separating wastes from body fluids and eliminating them.

Respiratory System (Excretion)

Excretes carbon dioxide, small amounts of other gases, and water.

Integumentary system (Excretion)

Excretes water, inorganic salts, lactic acid, and urea in the sweat.

Digestive System (Excretion)

Actively excretes water, salts, carbon dioxide, lipids, bile pigments, cholesterol, etc.

Urinary System (Excretion)

Excretes a broad variety of metabolic wastes, toxins, drugs, hormones, salts, hydrogen ions, and water.

Renal Parenchyma

Glandular tissue that forms the urine--appears C-shaped in frontal section.

Renal Cortex

Outer zone of the renal parenchyma, about 1 cm thick.

Renal Medulla

Inner zone of the renal parenchyma facing the sinus.

Renal Columns

Extensions of the cortex that project toward the sinus and divide the medulla into 6 to 10 renal pyramids.

Lobe of the Kidney

One pyramid and the overlying cortex.

Minor Calyx

Cup that nestles the papilla of each renal pyramid and collects the papilla’s urine.

Major Calyces

Converge to form the funnel-like renal pelvis.

Ureter

Tubular continuation of the renal pelvis that drains the urine to the urinary bladder.

Afferent Arteriole

Supplies one functional unit of the kidney, a nephron.

Glomerulus

Ball of capillaries enclosed in the glomerular capsule of the nephron.

Efferent Arteriole

Arteriole that blood leaves the glomerulus by.

Peritubular Capillaries

Network of capillaries around the renal tubule of the nephron.

Vasa Recta

Network of vessels that supply the renal medulla, arising from nephrons in the deep cortex close to the medulla.

Nephron

Functional unit of the kidney composed of a renal corpuscle and a renal tubule.

Renal Corpuscle

Filters blood plasma.

Renal Tubule

Converts the filtrate into urine.

Renal Corpuscle

Consists of the glomerulus and a two-layered glomerular capsule that encloses it.

Visceral Layer (Glomerular Capsule)

Elaborate cells called podocytes wrapped around the capillaries of the glomerulus.

Vascular Pole

Where the afferent arteriole enters the capsule, bringing blood to the glomerulus and the efferent arteriole leaves the capsule, carrying blood away.

Urinary Pole

Where the parietal wall turns away from the corpuscle and gives rise to the renal tubule.

Proximal Convoluted Tubule (PCT)

Arises from the glomerular capsule and is the longest and most coiled of the four regions of the renal tubule. It has a simple cuboidal epithelium with prominent microvilli (a brush border).

Nephron Loop

Long U-shaped portion found mostly in the medulla of the renal tubule.

Distal Convoluted Tubule (DCT)

Begins shortly after the ascending limb reenters the cortex.

Collecting Duct

Receives fluid from the DCTs of several nephrons as it passes back into the medulla.

Cortical Nephrons

Nephrons just beneath the renal capsule, close to the kidney surface.

Juxtamedullary Nephrons

Nephrons close to the medulla.

Kidney Function

Converts blood plasma to urine in four stages: glomerular filtration, tubular reabsorption, tubular secretion, and water conservation.

Glomerular Filtrate

Fluid in the capsular space, similar to blood plasma except that it has almost no protein.

Tubular Fluid

Fluid from the proximal convoluted tubule through the distal convoluted tubule, with substances removed and added by the tubule cells.

Tubular Reabsorption

Process of reclaiming water and solutes from the tubular fluid and returning them to the blood.

Transport Maximum (Tm)

Maximum rate of reabsorption, reached when the transporters are saturated.

Tubular Secretion

Process in which the renal tubule extracts chemicals from the blood and secretes them into the tubular fluid.

Aldosterone

Hormone secreted by the adrenal cortex when blood Na+ concentration falls or K+ concentration rises; stimulates reabsorption of Na+ and secretion of K+.

Natriuretic Peptides

Hormones secreted by the heart in response to high blood pressure; result in a reduction in blood volume and pressure.

Antidiuretic Hormone (ADH)

Hormone secreted by the posterior lobe of the pituitary gland that makes the collecting duct more permeable to water.

Parathyroid Hormone (PTH)

Hormone secreted by the parathyroid glands in response to calcium deficiency (hypocalcemia); acts to restore calcium homeostasis.

Water Diuresis

The cortical portion of the CD reabsorbs NaCl but is impermeable to water. Salt is removed, water stays in the CD, and urine osmolarity may be as low as 50 mOsm/L.

Countercurrent Multiplier

Continually recaptures salt and returns it to the deep medullary tissue, thus maintaining the salinity gradient.

Vasa Recta

A blood supply in the kidneys that also forms a countercurrent exchange system to prevent the urea and salt from being carried away.

Urinalysis

Examination of the physical and chemical properties of urine.

Urochrome

Pigment produced by the breakdown of hemoglobin that gives urine its yellow color.

Specific Gravity

Ration of density (g/mL) of a substance to the density of distilled water.

Diuresis / Polyuria

Output in excess of 2 L/day.

Oliguria

Output of <500 mL/day.

Anuria

Output of 0 to 100 mL/day.

Diabetes

Any metabolic disorder resulting in chronic polyuria.

Diuretic

Chemical that increases urine volume.

Renal Clearance

The volume of blood plasma from which a particular waste is completely removed in 1 minute.

Ureter

Retroperitoneal, muscular tube that extends to the urinary bladder.

Urinary Bladder

Muscular sac on the floor of the pelvic cavity, inferior to the peritoneum and posterior to the pubic symphysis.

Detrusor

Muscularis layer of the bladder consists of three layers of smooth muscle.

Trigone

Smooth-surfaced triangular area marked by the openings of the two ureters and the urethra, a common site of bladder infection.

Urethra

Conveys urine out of the body.

Micturition

The act of urinating.

Internal Urethral Sphincter

Smooth muscle sphincter around the urethra; this is what compresses the urethra and retains urine in the bladder.

External Urethral Sphincter

Skeletal muscle sphincter; provides voluntary control over the voiding of urine.

Nephron Function

Each nephron of the kidney is responsible for the filtration, reabsorption, and secretion processes that ultimately form urine.

Glomerular Filtration Rate (GFR)

The rate at which filtrate is formed in the kidneys; a key indicator of renal function. (\approx 120-125 \frac{mL}{min})

Renin-Angiotensin-Aldosterone System (RAAS)

A hormone system that regulates blood pressure and fluid balance; the kidneys play a crucial role by secreting renin.

Acid-Base Balance

The kidneys help regulate blood pH by excreting hydrogen ions and reabsorbing bicarbonate.

Detrusor Muscle Contraction

Urination is primarily controlled by the parasympathetic nervous system, which causes contraction of the detrusor muscle.

Filtration Membrane

Fenestrated endothelium of the capillary, basement membrane, and podocytes with filtration slits.

Renal Autoregulation

The ability of the nephrons to adjust their own blood flow and GFR without external (nervous or hormonal) control

Reabsorbed Substances

Substances such as glucose and amino acids are reabsorbed back into the blood.

Secretion

The process where substances are selectively moved from the blood into the nephron tubule.

Glomerular Hydrostatic Pressure

The primary force driving filtration, determined by blood pressure in the glomerulus.

Blood Colloid Osmotic Pressure

Force that opposes filtration, exerted by proteins in the blood.

Capsular Hydrostatic Pressure

The pressure exerted by the filtrate in the Bowman's capsule, opposing filtration.

Myogenic Mechanism

Maintains GFR by constricting or dilating the afferent arteriole in response to changes in blood pressure.

Tubuloglomerular Feedback

GFR regulation where macula densa cells in the DCT respond to NaCl levels in the filtrate.

Renin

Enzyme secreted by the kidneys in response to decreased blood pressure or blood volume; initiates the RAAS.

Angiotensin II

Vasoconstrictor that increases blood pressure and stimulates aldosterone release.

Aldosterone

Hormone that promotes sodium and water reabsorption in the kidneys, increasing blood volume and pressure.

Atrial Natriuretic Peptide (ANP)

Released by the heart in response to high blood volume, inhibits sodium reabsorption, leading to decreased blood volume and pressure.

Antidiuretic Hormone (ADH)

Hormone that increases water reabsorption in the kidneys, reducing urine volume.

Urine pH

Normal pH range of urine.

Glycosuria

Presence of glucose in the urine, often indicative of diabetes mellitus.

Proteinuria

Presence of proteins in the urine, may indicate kidney damage or disease.

Hematuria

Presence of blood in the urine, can be caused by various disorders.

Cystitis

Inflammation of the urinary bladder, often caused by bacterial infection.

Nephrolithiasis

Stones in the kidney or urinary tract, can cause severe pain and urinary obstruction.

Chronic Kidney Disease (CKD)

Progressive loss of kidney function, can lead to end-stage renal disease.

Kidney Failure

Complete or near-complete failure of the kidneys to function, requiring dialysis or kidney transplant.

Urinary Tract Infection (UTI)

Infection of the urinary system, usually involving the bladder, urethra, or kidneys.