urinary_system

Unit 17: Urinary System

Overview

• Kidneys' Functions: Dispose of waste in urine including:

  • Nitrogenous wastes

  • Toxins

  • Drugs

  • Excess ions

• Regulatory Functions:

  • Production of renin (maintains blood pressure)

  • Production of erythropoietin (stimulates red blood cell production)

  • Conversion of vitamin D to its active form

Organs of the Urinary System

• Kidneys

• Ureters

• Urinary Bladder

• Urethra

Kidneys

Structure and Location

• Position: Retroperitoneal; T12 to L3 vertebrae

• Dimensions: Approximately 12 cm long and 6 cm wide

• Right Kidney: Slightly lower than the left due to the liver

Protective Layers

• Fibrous Capsule: Encloses each kidney

• Perirenal Fat Capsule: Cushions against impacts

• Renal Fascia: Anchors kidneys to surrounding structures

Kidney Regions

1. Renal Cortex: Outer region

2. Renal Medulla: Deeper region

   • Renal Pyramids: Triangular tissue

   • Renal Columns: Extensions of cortex separating pyramids

3. Renal Pelvis: Funnel-shaped

   • Calyces: Collect and direct urine to renal pelvis

Blood Supply

• About 25% of total blood supply through kidneys each minute

• Arterial Flow: Renal artery → segmental arteries → interlobar arteries → arcuate arteries → cortical radiate arteries

• Venous Flow: Cortical radiate veins → arcuate veins → interlobar veins → renal vein (no segmental veins)

Nephrons

Structure

• Functional units of kidneys; over a million per kidney

• Main Parts:

  1. Renal Corpuscle

     • Glomerulus: Knot of capillaries

     • Glomerular Capsule: Surrounding structure

  2. Renal Tubule: Extends to collecting duct

     • Parts: Proximal convoluted tubule (PCT), Nephron loop (loop of Henle), Distal convoluted tubule (DCT)

Types of Nephrons

• Cortical Nephrons: Located in cortex

• Juxtamedullary Nephrons: Extend into medulla

Urine Formation

Processes

1. Glomerular Filtration: Nonselective passive process

2. Tubular Reabsorption: Reabsorbs useful substances like water, glucose, ions

3. Tubular Secretion: Moves substances from blood to renal tubules; important for drug and ion elimination

Characteristics of Urine

• Color: Clear to pale yellow due to urochrome

• Normal pH: Slightly acidic (~6)

• Volume: 1.0 to 1.8 liters per day

Components of Urine

• Normal Solutes: Sodium, potassium, urea, creatinine

• Absent Substances: Glucose, proteins, blood cells

Urinary System Structures

Ureters

• Connect kidneys to urinary bladder; 25-30 cm long; use peristalsis

Urinary Bladder

• Stores urine (up to 500 mL); composed of three smooth muscle layers (detrusor muscle)

• Features trigone with three openings

Urethra

• Conducts urine from bladder to outside; longer in males

• Two sphincters control urine release:

  1. Internal Urethral Sphincter: Involuntary

  2. External Urethral Sphincter: Voluntary

Micturition

• Process of bladder emptying; controlled by sphincters

Fluid and Electrolyte Balance

Kidney Functions

1. Excreting nitrogen wastes

2. Maintaining water and electrolyte balance

3. Regulating blood pH

Regulation of Water Balance

• Water intake = output for proper hydration

• Influenced by thirst mechanism and kidneys (ADH role)

Electrolyte Regulation

• Hormonal control via aldosterone, which promotes sodium reabsorption and water follows

Acid-Base Balance

• Blood pH: 7.35 - 7.45

• Kidneys have significant role, involving bicarbonate and hydrogen ion adjustments

Development

• Kidneys develop early in life; urinary issues include UTIs, especially with E. coli

• Aging effects: urgency, frequency, nocturia, and incontinence issues

Aging-Related Problems

• Renal function decline leading to increased urinary symptoms (urgency, incontinence).

The color of urine can indicate various diseases and health conditions. Here is a guide to urine colors and their possible medical significance:

Normal Urine Color

1. Pale Yellow to Amber

   • Normal and Healthy: Due to urochrome, a pigment from the breakdown of hemoglobin.

   • Darker Shades: May indicate dehydration.

Abnormal Urine Colors and Their Possible Causes

1. Clear or Colorless

• Possible Cause: Overhydration, diabetes insipidus

• Reason: Drinking too much water or an inability to retain fluids.

2. Dark Yellow or Orange

• Possible Causes: Dehydration, liver disease, bile duct obstruction, medications (e.g., rifampin, phenazopyridine)

• Reason: High concentration of urochrome or excess bilirubin in urine.

3. Brown or Tea-Colored

• Possible Causes: Liver disease (hepatitis, cirrhosis), severe dehydration, hemolysis (red blood cell destruction), rhabdomyolysis

• Reason: Bilirubin, myoglobin, or excess urobilinogen in urine.

4. Red or Pink

• Possible Causes: Blood in urine (hematuria), kidney disease, urinary tract infection (UTI), kidney stones, bladder cancer, eating beets or blackberries

• Reason: Presence of red blood cells or certain pigments from food.

5. Blue or Green

• Possible Causes: Bacterial infection (Pseudomonas), medications (e.g., amitriptyline, propofol, methylene blue), genetic conditions (Hartnup disease)

• Reason: Bacterial pigments or drug-induced discoloration.

6. Purple (Rare)

• Possible Cause: Purple Urine Bag Syndrome (in catheterized patients with UTIs)

• Reason: Breakdown of tryptophan by bacteria.

7. Milky or Cloudy

• Possible Causes: Urinary tract infection (UTI), kidney stones, excess white blood cells or protein in urine

• Reason: Presence of pus (pyuria), bacteria, or fat deposits.

When to Seek Medical Attention?

• Persistent abnormal color without a clear cause (e.g., food, medication).

• Dark brown urine (sign of liver or muscle breakdown issues).

• Red or pink urine without eating red-colored foods.

• Cloudy or milky urine with pain or fever (possible infection).

Would you like more details on a specific urine color or related disease?The smell of urine can provide important clues about various diseases and medical conditions. Here are some common urine odors and the potential diseases or conditions associated with them:

1. Sweet or Fruity Odor

• Possible Cause: Diabetes mellitus (due to excess glucose and ketones in urine)

• Reason: Uncontrolled diabetes leads to ketoacidosis, which produces a fruity smell in urine.

2. Ammonia-Like Smell

• Possible Causes: Dehydration or urinary tract infection (UTI)

• Reason: Concentrated urine due to dehydration or bacterial activity in a UTI.

3. Strong or Foul-Smelling Urine

• Possible Causes: Urinary tract infection (UTI) or kidney infection

• Reason: Bacteria produce foul-smelling compounds in infected urine.

4. Rotten or Fishy Smell

• Possible Cause: Trimethylaminuria (Fish Odor Syndrome) or bacterial vaginosis

• Reason: The body cannot break down trimethylamine, leading to a fishy urine odor.

5. Musty or Moldy Odor

• Possible Causes: Liver disease or metabolic disorders like phenylketonuria (PKU)

• Reason: PKU leads to an inability to metabolize phenylalanine, while liver disease causes an accumulation of toxins.

6. Sulfur-Like or Rotten Egg Smell

• Possible Causes: Consumption of sulfur-rich foods (like asparagus or garlic), or infections

• Reason: Bacterial infections or metabolic disorders affecting sulfur metabolism.

7. Maple Syrup Odor

• Possible Cause: Maple Syrup Urine Disease (MSUD)

• Reason: A rare genetic disorder where the body cannot break down certain amino acids.

8. Chemical or Bleach-Like Smell

• Possible Causes: Dehydration, medications, or metabolic disorders

• Reason: Certain drugs or metabolic conditions alter urine composition.

9. Alcohol or Yeasty Smell

• Possible Cause: Yeast infection or metabolic disorders

• Reason: Overgrowth of yeast can lead to unusual urine odor.

If someone notices a persistent unusual urine smell, it is important to consult a healthcare provider for further evaluation. Would you like more details on any specific condition?