Urinary Tract: Anatomy, Physiology, and Diseases
Urinary Tract Features
The urinary tract performs the following functions:
- Eliminates waste substances from cellular metabolism.
- Regulates body fluid composition.
- Serves as an endocrine gland.
Anatomy
Kidneys
Located on both sides of the spine (dorsolumbar area). They are surrounded by fat, which protects them from shock and keeps them in place. Kidneys filter blood and retain substances for reuse.
Parts:
- Cortex: The outer part where the nephrons are found. The nephron is in charge of filtering the blood.
- Medulla and Malpighian Pyramids: Contain collecting ducts that gather substances filtered by the nephron, forming urine.
- Renal Pelvis: Where the collecting ducts converge, and where concentrated urine exits the kidney.
Urinary Tract
Responsible for carrying urine from the kidneys to the outside.
- Ureters: Originate in the renal pelvis and reach the bladder. They use peristaltic movements controlled by the autonomic nervous system to move urine.
- Urinary Bladder: A bag-shaped organ where urine accumulates. When a significant amount accumulates, the bladder’s size increases until the pressure causes the expulsion of urine (urination). This operation is controlled by the parasympathetic nervous system.
- Urethra: Carries urine from the bladder to the outside.
Physiology
Blood containing waste substances arrives via the renal artery and is filtered in the glomeruli of the nephrons. This process results in:
- Clean blood, which is returned via the renal vein.
- Waste substances, which pass through Bowman’s capsule into the collecting tubules, then to the renal pelvis, ureters, bladder, and urethra, and finally are expelled.
Composition of Urine
Urine is composed of water, sodium, potassium, urea, uric acid, calcium, phosphates, and drugs. Erythrocytes, leukocytes, and plasma proteins are never expelled in normal urine.
Normal Urine Characteristics
- Volume in 24 hours: 1.5L
- Appearance: Clear
- Color: Amber or straw-colored
- Density: 1020 g/mL – 1050 g/mL
- Acidity: pH = 6
Catheters
Catheters are used to introduce urea into the bladder. They are normally made of silicone.
Characteristics:
- Size: External diameter: 12-24 French
- Shape: Straight, with a curved or beveled tip
- Rigidity: Flexible, semi-rigid, rigid, or hard
- Number of Lumens: Number of channels (1 lumen for urine output; 2 and 3 lumens: for urine output and air entry).
Nurses perform catheterizations. Nursing staff prepares the patient, brings the necessary materials, cooperates with the procedure, collects the equipment, and assesses the catheterization, including hygiene and urine collection bag management.
Diseases
Symptoms associated with urine:
- Hematuria (presence of blood in urine)
- Dysuria (painful urination)
- Anuria (lack of urination)
Diseases may affect different parts of the excretory system:
- Kidneys: (Renal failure, pyelonephritis, nephrotic syndrome)
- Urinary Tract: (Cystitis, lithiasis)
- Metabolism of Water, Sodium, and Potassium: (Intoxication, dehydration, hyperkalemia, hypokalemia)
Water Balance
Water represents 60-70% of body mass in healthy individuals. It is important that a balance exists between the quantity of water consumed and expelled.
Water Gain
- Liquids (1300 mL)
- Food (1000 mL)
- Water from oxidation (300 mL)
- Total: 2600 mL
Water intake is measured using beverage containers and graduated food contribution tables.
Water Loss
- Lungs (400 mL)
- Skin (500 mL)
- Urine (1500 mL)
- Feces (200 mL)
- Total: 2600 mL
Water loss is measured through diuresis (urine), bowel movements, drainage, vomiting, bleeding, and sweating.
Fluid Imbalance:
- Positive: Intake is greater than output. Causes: Excessive water intake, kidney malfunction, heart abnormalities.
- Negative: Insufficient water intake, excessive sweating, diarrhea, vomiting, kidney disorders, burns, bleeding, trauma.