Question

The opening of the urinary bladder is
A. Nephron
B. Ureter
C. Urethra
D. Nephridia

Answer 1

Hint: Urinary bladder opens into the tube-like structure which acts as the common opening for both urine and semen (male reproductive tract), but in females, it acts as an organ to discharge urine to outside.

Complete answer: Humans have one pair of the kidney (bean-shaped) which is located in the last thoracic and third lumbar vertebra and lie in close proximity with the dorsal wall of the abdominal cavity. Each kidney has about one million nephrons (which is the functional unit of excretion) which consist of Bowman’s capsule, PCT (proximal convoluted tubule), DCT (Distal Convoluted Tubule), Vasa recta, and Collecting duct.
-Many Collecting tubules gather together and converge into the medulla part of the kidney which then opens into the pelvis which converges into the ureter which carries the urine and then finally drops it into the urinary bladder.
-And the urine is stored in the urinary bladder and when it is filled with urine, it stretched and the receptors present in them send signals to the central nervous system and in return, it activates the smooth muscle of the bladder to contract, and urethral sphincter to relax causing the discharge of urine. This process is called micturition. Generally, an adult man excretes 1 – 1.5 litre of urine in one day. Nephridia is the tubular structure that helps in excretion in the annelids. It removes the nitrogenous waste to maintain ionic and fluid balance.
So, the correct answer is option (C).

Additional information:
There are different types of excretory organs in different members of the animal kingdom. Invertebrates have a simpler excretory system than vertebrates (they have kidneys).
1. Protonephridia (also called flame cells because of their appearance): They are the excretory structure in Platyhelminthes (Flatworm), Amphioxus(Cephalochordate), rotifers(aschelminthes), and in some annelids. They are mainly concerned with osmoregulation.
2. Nephridia: It is the tubular structure that helps in excretion in the Annelids. It removes the nitrogenous waste to maintain ionic and fluid balance.
3. Malpighian tubules: These are the organ of excretion in most insects (like cockroaches).
4. Antennal gland (also known as green gland): These are for the excretion in crustacean (prawn)

Note: Based on the type of excretory material, there are different types of organisms:
1. Ammonotelic: Those organisms which excrete ammonia are called ammonotelic. For the excretion of ammonia, a large amount of water is needed as it is the most toxic one. So these organisms are mainly aquatic. Example: bony fish, aquatic amphibians, and insects.
2. Ureotelic: Those organisms which eliminate urea from their body are called ureotelic. It is less harmful than ammonia and hence requires less amount of water than ammonia. Example: mammals, terrestrial amphibians, and marine fishes.
3. Uricotelic: These organisms excrete uric acid which is the least toxic one and hence it requires the least amount of water for its elimination.
Example: birds, insects.