Urinary System: Medical Terminology and Anatomy Study Guide

Urinary System Overview

Introduction to the Urinary System

The urinary system is responsible for filtering metabolic waste from the bloodstream and eliminating it from the body through excretion. It plays a crucial role in maintaining homeostasis by regulating fluid and electrolyte balance, as well as removing toxins.

• Key Organs: Kidneys, ureters, urinary bladder, and urethra.

• Main Function: Filtration of blood, urine production, storage, and excretion.

• Location: The kidneys are located in the lumbar region above the waist, on either side of the vertebral column.

External and Internal Anatomy of the Kidney

External Anatomy

The kidney has a characteristic bean shape with a concave area called the renal hilum on its medial surface. The renal artery enters, and the renal vein and ureter exit through the hilum.

• Renal Artery: Supplies blood to the kidney.

• Renal Vein: Drains filtered blood from the kidney.

• Ureter: Transports urine from the kidney to the bladder.

Internal Anatomy

The kidney is divided into three main regions:

• Renal Cortex: The outermost region, containing the majority of nephrons.

• Renal Medulla: The inner region, organized into triangular structures called renal pyramids. The tip of each pyramid is the renal papilla, which points toward the renal pelvis.

• Renal Pelvis: A funnel-shaped cavity that collects urine from the calyces and channels it into the ureter.

• Calyx: Cup-shaped tubes that collect urine from the pyramids and empty into the renal pelvis.

Nephron Structure and Function

Nephron: The Functional Unit

Each kidney contains about one million nephrons, which are responsible for filtering blood and forming urine. The nephron consists of two main parts: the renal corpuscle and the renal tubule.

• Renal Corpuscle: Includes the glomerulus (a cluster of capillaries) and the Bowman's (glomerular) capsule (a double-walled structure that encases the glomerulus).

• Afferent arteriole: Brings blood to the glomerulus.

• Efferent arteriole: Carries blood away from the glomerulus.

• Renal Tubule: Reabsorbs needed substances (water, electrolytes) and removes waste. It is divided into:

  • Proximal convoluted tubule

  • Nephron loop (Loop of Henle): Descending and ascending limbs

  • Distal convoluted tubule

  • Collecting tubule

Urinary Bladder Anatomy and Physiology

Structure and Function

The urinary bladder is an elastic, muscular sac located in the anterior portion of the pelvic cavity. It stores urine until excretion. The bladder wall is composed of three layers of smooth muscle and is lined with a mucous membrane containing rugae, which allow expansion.

• Internal sphincter: Made of smooth muscle, relaxes involuntarily during urination.

• External sphincter: Made of skeletal muscle, under voluntary control.

• In males: The prostate gland is located inferior to the bladder.

Urethra Anatomy

Male and Female Urethra

The urethra is a tubular structure that carries urine from the bladder to the outside of the body. The external opening is called the urinary meatus.

• Female urethra: Shorter and located anterior to the vagina; carries only urine.

• Male urethra: Longer, passes through the prostate and penis; carries both urine and semen.

Medical Terminology: Word Building

Combining Forms and Suffixes

Medical terms for the urinary system are constructed using combining forms and suffixes. Understanding these helps in deciphering complex terminology.

Combining Form/Suffix	Definition	Memory Tool
vesic/o	bladder	vessel
pyel/o	renal pelvis	Kidney Pilot Elf
azot/o	nitrogenous waste	No No risotto!
contin/o	to hold in	Contain it!
noct/o	night	nocturnal
olig/o	few in number	oligarchy
spadias/o	tear, slit	spade (split card)
idi/o	distinctive, unknown	ID
-tripsy	crushing	Trip to Italy (grape stomping)

Urinary System: Vocabulary and Pathology

Common Terms and Disorders

Understanding the vocabulary related to urinary system pathology and pharmacology is essential for recognizing clinical conditions and treatments.

Medical Term	Definition	Memory Tool
Enuresis	Involuntary urination (bedwetting)	In Your PJs
Calculus	Small stone formed from mineral salts	Calculating Abacus
Stricture	Abnormal narrowing of a urinary passageway	Strictly narrowed structure
Wilms Tumor	Malignant kidney tumor in children	Welling up Kid-ney
Thiazide	Diuretic for high BP and edema	Edemic THIgh
Potassium-Sparing	Diuretic that spares potassium	K stays
Renin	Enzyme controlling BP via vasoconstriction	Raises Readings

Urinary Diagnostic and Laboratory Terms

Key Diagnostic Tests

Several laboratory and imaging tests are used to assess kidney function and diagnose urinary system disorders.

Medical Term	Definition	Memory Tool
Albumin/Creatinine Ratio (ACR)	Screening test for albumin and creatinine in urine; high ratio indicates kidney disease	Albumin Creates Risks
Estimated Glomerular Filtration Rate (eGFR)	Measures how effectively kidneys filter blood	Filtration Rate
Retrograde Pyelography (RP)	X-ray with contrast dye injected against urine flow to visualize kidneys, ureters, bladder	Renally Precise Imaging

Summary Table: Main Structures and Functions

Structure	Function
Kidney	Filters blood, forms urine
Ureter	Transports urine to bladder
Urinary Bladder	Stores urine
Urethra	Excretes urine from body

Key Equations

• Estimated Glomerular Filtration Rate (eGFR):

$\text{eGFR} = \frac{140 - \text{age}}{\text{serum creatinine}} \times \text{weight} \times 0.85 \text{ (if female)}$

Additional info: The above formula is a simplified version; actual eGFR calculations may use more complex variables and constants depending on the method (e.g., MDRD or CKD-EPI equations).