Test: Fertilisation and Implantation (November 4) - NEET MCQ

After fertilisation, a single-celled zygote develops into a multicellular structure called blastocyst. This blastocyst then gets embedded in the endometrium of the uterus and the process is known as implantation.

Cleavage is a series of rapid mitotic divisions of the zygote, characterised by absence of growth in daughter cells, which converts a single celled zygote into a multicellular structure called blastocyst. It starts in the Fallopian tube and is holoblastic. Interphase in cleavage division is short and don not involve growth so that the resulting blastomeres become smaller in size as their number increases. During cleavage, at 8-16 celled stage, a solid ball of cells called morula (as it look like mulberry) is formed.

In human adult females, oxytocin is a hormone released by the pituitary gland (neurohypophysis), that causes contraction of the uterine muscles during labour.

let's analyze the terms:

• Cleavage refers to a series of rapid mitotic divisions.
• Morula is a stage in embryonic development, often described as a "little mulberry" due to its appearance.
• Polyspermy refers to the fertilization process involving multiple sperm.
• Implantation refers to the embedding of the embryo into the endometrium of the uterus.

Now let's match these terms:

• Cleavage - (ii) Mitotic divisions
• Morula - (iv) Little mulberry
• Polyspermy - (i) Fertilization
• Implantation - (iii) Endometric

Correct option is A. 

In the epididymis, the sperms mature physiologically, gaining increased motility and fertilising capacity.
The epididymis is a long, coiled tube that holds sperm until it is ejaculated. Sperm develops in the epididymis, a long twisted tube. The epididymis' tail attaches to the vas deferens, which transports sperm to the ejaculatory duct. In the epididymis, sperm gain motility.

Immediately after the fusion of sperm and egg plasma membranes, the egg shows a cortical reaction. In this reaction, the cortical granules present beneath the egg's plasma membrane fuse with the plasma membrane and release enzymes between it and zona pellucida. These enzymes harden the zona pellucida, which now functions to block polyspermy.

The secretions of the female genitaltract remove coating substances deposited on the surface of the sperms particularly those on the acrosome. Thus, the receptor sites on the acrosome are exposed and sperm becomes active to penetrate the egg. This phenomenon of sperm activation in mammals is known as capacitation.

Implantation is embedding of the blastocyst into the endometrium of the uterus. Implantation begins about 7th day after fertilization of ovum and it takes about 3 days for the process to be completed.

During fertilization, the head of the sperm containing nucleus (DNA) enters the egg leading to formation of diploid zygote.