Human Reproduction

(a) The corpus luteum is a temporary endocrine structure involved in ovulation and early pregnancy.

The main secretory product of corpus luteum is progesterone, which is required for the establishment and maintenance of pregnancy.

(b) The correct sequence for transport of sperm cells in male reproductive system is: Seminiferous tubules $\rightarrow$ Rete testis $\rightarrow$ Vasa efferentia $\rightarrow$ Epididymis $\rightarrow$ Vas deferens $\rightarrow$ Ejaculatory duct $\rightarrow$ Urethra $\rightarrow$ Urethral meatus

(c) Meiotic division of secondary oocyte is completed after the entry of sperm in secondary oocyte which lead to the formation of a large ovum and a tiny $2^{\text{nd }}$ polar body.

(b) Blastopore is the small slit-like opening on the dorsal side of the gastrula, also known as the dorsal lip.

(a) The testes are present in the scrotum which maintains the scrotal temperature below $2^{\circ} C$ of the internal body temperature.

(a) The pattern of cleavage is determined by the amount of yolk and its distribution.

In holoblastic cleavage, the segmentation lines pass through the entire egg.

Hence, it divides egg completely.

Egg in this type of cleavage contains moderate to sparse amount of yolk.

For example, frog, human egg.

In meroblastic cleavage, the sedimentation lines do not completely pass through the egg and remain confined to a part of the egg.

Hence, it does not divide the egg completely egg in this type of cleavage contains a large amount of yolk.

For e.g. insects and birds.

(a) Gastrulation ends with the complete obliteration of blastocoel. The stage of three primary germ layers begins.

(c) The ovum is released by the ovary is transported to the ampullary isthmic junction where fertilisation takes place.

The mitotic division starts as the zygote moves through the isthmus of the oviduct called cleavage towards the uterus and forms 2, 4, 8 and 16 daughter cells called blastomeres.

The embryo with 8 to 16 blastomeres is called morula.

(c) Ectoderm produces - Liver, Epidermis, glands, hair, nervous system etc.

Endoderm produces - Pancreas, lining of urinary bladder etc.

Mesoderm produces - Dermis, most muscles, Kidneys, Gonads etc.

(b) Four extra-embryonic membranes are present in mammals which originally arise from trophoblast viz. amnion, chorion, allantois and yolk sac.

The trophoblast is the outermost layer of cells in morula.