Human Reproduction Test - 23

Secondary oöcyte

LH (Luteinizing hormone) is secreted by pituitary gland.

The embryo with 8 to 16 blastomeres is called a morula. Morula is the solid mass of cells and is mulberry like. Morula is a developmental stage between the zygote and blastocyst.

Hyaluronidase is a hydrolytic enzyme present in the acrosome of sperm. It lyses the glycosaminoglycans in the extracellular matrix holding the cells of the corona radiata together. As the coronal cells become more loosely associated, sperm cells can propel themselves inward, towards the zona pellucida by making a receptive cone or fertilization cone through the cytoplasm of the egg. Hyaluronidase may also be involved in breaking down the zona pellucida.

Fertilizin is a chemical substance secreted from the cortical region of egg cytoplasm to attract the sperm towards the egg. Acrosin is released from the acrosome of a spermatozoa as a consequence of the acrosomal reaction. Capacitation is the final stage in the maturation process of spermatozoa. This takes place inside the genital tract of the female as the sperm penetrates the ovum.

The outermost membranous cover to the ovum at ovulation is corona radiata. It is formed by follicular cells. Inner to corona radiata is zona pelluicda, which is made up of three different glycoproteins secreted by the ovum itselt.

Menstruation occurs in humans, apes and old world monkeys. Menstruation is bleeding from the uterus of adult females at intervals of one lunar month. In human females, the menstruation is repeated at an average interval of about 28/29 days and the cycle of events starting from one menstruation till the next one is called the menstrual cycle.

The following events given in the options occur in a normal menstrual cycle.

(i)  Release of egg called ovulation usually takes place roughly 14 days after the first day of the start of a period for fertilization.

(ii)  Following menstruation endometrium regenerates about 8 days during the proliferative phase.

(iii)  Implantation occurs after 7 days of fertilization.

(iv)  Progesterone level rises after ovulation which occurs after 14 days.

The cross section of the sperm midpiece shows the axial bundle of microtubules or axoneme surrounded by a microtubular sheath in which the mitochondria of the spermatid have become arranged in a helical manner. The microtubular structure provide the ability to the sperm to swim through the reproductive tract of the female. The microtubules are in 9 + 2 arrangement.