Mention the number of cells in the following stages:

S. No	Embryonic stages	No. of cells
(i)	Zygote	______________
(ii)	Morula	______________
(iii)	Blastocyst	______________

Draw a labelled diagram of a part of the transverse section through seminiferous tubule of human testis showing the various stages of spermatogenesis.

Study the figure given below and answer the questions that follow:
Where are the stem cells located in this embryo?

Placenta acts as an endocrine tissue. Justify.

The doctor could hear the heartbeats in a foetus. How many days of gestation period must have passed?

Write the location and functions of the following in human testes:

1. Sertoli cells.
2. Leydig cells.

Draw a diagram of a human sperm. Label only those parts along with their functions, that assist the sperm to reach and gain entry into the female gamete.

What is the role of foetus in inducing parturition?

Label a, b, c in the following diagram.

Mention the relationship between concentration of luteinising hormone and maintenance of endometrium in the human uterus.