Urinary System Lecture Notes

Vocabulary-style flashcards covering the functional organization, anatomy, and physiological processes of the urinary system based on MBBS 1st Year lecture notes.

Urinary System Components

The system consists of $2$ kidneys, $2$ ureters (one for each kidney), a urinary bladder, and a urethra.

Uremia

A condition resulting from kidney failure where urea, creatinine, and other toxins build up in the blood.

Acidosis

A state caused by kidney failure where the blood pH falls below the narrow range of $7.35\text{–}7.45$ because the kidneys can no longer regulate acid-base balance.

Erythropoietin

A hormone synthesized by the kidneys that stimulates the production of red blood cells in the bone marrow.

Metabolic Acidosis/Alkalosis Prevention

The kidneys maintain blood pH by excreting hydrogen ions ($H^+$) to counteract acidosis and reabsorbing bicarbonate ($HCO_3^-$) to counteract alkalosis.

Renin-Angiotensin-Aldosterone System (RAAS)

A hormonal cascade triggered by the release of renin from the kidneys that leads to vasoconstriction, sodium retention, and increased blood pressure.

Calcitriol

The most biologically active form of vitamin D ($1, 25\text{-dihydroxycholecalciferol}$) activated by the kidneys to promote intestinal calcium absorption.

Gluconeogenesis

The metabolic process by which the kidneys synthesize glucose during periods of prolonged starvation.

Renal Pyramids

Between $6$ and $18$ conical-shaped structures located in the inner medulla layer of the kidney.

Nephron

The functional unit of the kidney responsible for urine formation, with approximately $1.25$ million present in each kidney.

Renal Corpuscle

The component of the nephron where filtration occurs, consisting of the glomerulus (capillary network) and Bowman's capsule.

Cortical Nephrons

Nephrons located primarily in the renal cortex that comprise about $85\%$ of all nephrons and have short Loops of Henle.

Juxtamedullary Nephrons

Nephrons ($15\%$ of the total) situated near the medulla with long Loops of Henle critical for establishing the osmotic gradient to concentrate urine.

Renal Blood Flow

The kidneys receive approximately $20\%$ of the total resting cardiac output, which is about $1.1\,L/min$ in an average person.

Glomerular Filtration Rate (GFR)

The amount of filtrate produced by the kidneys per unit time, averaging $125\,ml/min$ or $180\,L/day$.

Peritubular Capillaries

Tiny blood vessels that travel alongside renal tubules, facilitating the reabsorption of water/solutes and the secretion of waste products.

Vasa Recta

Specialized peritubular capillaries associated with the Loop of Henle in juxtamedullary nephrons that help produce concentrated urine.

Proximal Convoluted Tubule (PCT)

The segment of the renal tubule that reabsorbs $60\text{–}70\%$ of the filtrate, including all filtered glucose and amino acids.

Loop of Henle (LH)

A nephron segment consisting of a descending limb that reabsorbs $20\%$ of water and an ascending limb that reabsorbs solutes like $Na^+$ and $Cl^-$.

Antidiuretic Hormone (ADH)

A hormone that regulates facultative water reabsorption in the collecting ducts based on the body's hydration needs.

Ureters

Narrow muscular tubes about $25\text{–}30\,cm$ long that transport urine from the renal pelvis to the bladder via peristalsis.

Detrusor Muscle

The smooth muscle layer of the bladder wall that contracts during the process of urination (micturition).

Trigone

A triangular area at the base of the bladder that is highly sensitive to stretch and signals the urge to urinate.

Female Urethra

A tube approximately $3\text{–}4\,cm$ long that carries urine to the exterior and is more prone to urinary tract infections due to its shorter length.

Male Urethra

A tube approximately $18\text{–}22\,cm$ long that passes through the prostate and penis, serving to transport both urine and semen.