The urinary system, also known as the renal system, includes organs like the kidneys, ureters, bladder, and urethra. It's responsible for filtering waste from the blood, producing urine, and eliminating it from the body while maintaining proper fluid and electrolyte balance.
1. Kidney :
Location : Human kidneys are situated beneath the peritoneum membrane on both sides of the spine in the lumbar region of the abdominal cavities. The superior end of the kidney lies below the twelfth thoracic vertebra (T12), and the inferior end sits above the third lumbar vertebra (L3). The left kidney is slightly higher than the right kidney.
Structure : Kidneys resemble kidney beans in shape, measuring approximately 11 cm in length, 5 cm in width, and about 3 cm in thickness. An adult male kidney typically weighs around 150 grams, while a female kidney weighs approximately 135 grams. The lateral margin of the kidney is rounded, and the medial margin is concave. The concave groove on the kidney is called the hilum, through which the renal vein and renal artery enter and exit the kidney.
2. Ureter :-
The duct that originates from the hilum region of the kidney and extends to the bladder is the ureter. Each ureter is approximately 25-30 cm in length. The funnel-like part formed by the fusion of the major calyces is called the renal pelvis. Each ureter arises from the renal pelvis and extends downward to enter the urinary bladder on both sides of the body.
• Functions : Urine produced in the kidney is transported through the ureters to the urinary bladder.
3. Urinary bladder :-
The urinary bladder is a muscular sac located in the pelvic cavity. Its inner wall consists of transitional epithelium. The muscle layer of the bladder is called the detrusor muscle. At the junction of the bladder and urethra, there is an internal sphincter composed of circular muscles, and an external sphincter composed of skeletal muscles below it. The triangular part inside the bladder at the junction of the urethra is called the trigone.
• Functions : Urine is temporarily stored in the urinary bladder.
4. Urethra :-
The urethra arises from the urinary bladder and opens to the outside of the body through the external urethral orifice. The male urethra extends through the scrotum and carries both urine and semen. The prostate is a walnut-sized gland found in men, situated just below the bladder and surrounds the urethra. Its primary function is to produce seminal fluid, which nourishes and transports sperm during ejaculation.
