Unit 8
The Excretory System
Question: Describe the structure and functions of the ureter. (5 Marks)
Answer:
Ureter
> The ureters are two narrow muscular tubes that carry urine from the kidneys to the urinary bladder.
> Each ureter is about 25–30 cm long and 3 mm in diameter.
> The ureter begins from the renal pelvis of the kidney.
> It passes downward through the abdominal cavity and opens obliquely into the posterior wall of the urinary bladder.
> This oblique opening prevents the backflow of urine (reflux) from the bladder to the kidneys.
Structure of Ureter
The wall of the ureter consists of three layers:
> Outer Fibrous Layer – Made of fibrous connective tissue and continuous with the fibrous capsule of the kidney.
> Middle Muscular Layer – Made of smooth muscle fibers and helps in the movement of urine by peristalsis.
> Inner Mucosal Layer – Lined by transitional epithelium and allows stretching during the passage of urine.
Functions of Ureter
> Carries urine from the kidneys to the urinary bladder.
> Peristaltic movements of smooth muscles push urine downward.
> Prevents backflow of urine from the bladder into the kidneys.
> Helps in continuous flow of urine to the bladder.
Question: What are the functions of the kidneys?
Answer:
Functions of Kidney
Excretion of Waste Products : Kidneys remove waste substances like urea, uric acid, and creatinine from the blood through urine.
Formation of Urine : Kidneys filter blood and form urine to eliminate wastes and excess substances.
Maintenance of Water Balance :Kidneys regulate the amount of water in the body.
Regulation of Electrolytes : They maintain the balance of salts and minerals such as sodium, potassium, and calcium.
Maintenance of Acid-Base Balance : Kidneys help maintain normal pH of the blood.
Control of Blood Pressure : Kidneys help regulate blood pressure by controlling fluid balance and secreting renin.
Production of Hormones : Kidneys produce erythropoietin for red blood cell formation and activate vitamin D for healthy bones.
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