Provide definitions/explanations for the following terms:
$(1)$ Malpighian body
$(2)$ Sebaceous gland

Which of the following statements is correct?

The main function of the renal pyramids of the kidney is to:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Nephrons are of two types: Cortical and Juxta-medullary,based on their relative position in the cortex and medulla.
Reason $R$: Juxta-medullary nephrons have a short loop of Henle,whereas cortical nephrons have a longer loop of Henle.
In the light of the above statements,choose the correct answer from the options given below:

In a rabbit,the urinary bladder opens into:

Kidneys of mammals are present on either side of the vertebral column at the level of: