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
Renal Cortex: Outer region
Renal Medulla: Deeper region
Renal Pyramids: Triangular tissue
Renal Columns: Extensions of cortex separating pyramids
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:
Renal Corpuscle
Glomerulus: Knot of capillaries
Glomerular Capsule: Surrounding structure
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
Glomerular Filtration: Nonselective passive process
Tubular Reabsorption: Reabsorbs useful substances like water, glucose, ions
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:
Internal Urethral Sphincter: Involuntary
External Urethral Sphincter: Voluntary
Micturition
Process of bladder emptying; controlled by sphincters
Fluid and Electrolyte Balance
Kidney Functions
Excreting nitrogen wastes
Maintaining water and electrolyte balance
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
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?