Human Reproduction Test - 87

Biflagellate sperms occur in few invertebrates like flatworms and few teleost fishes among vertebrates. Toadfish is a general term used to describe fishes having toad like appearance. They belong to several families of bony fishes. Sperm of Ascaris are amoeboid and non-flagellated. Sperms of man and rat have uni-flagellated tail.

Follicle stimulating hormone is one of the gonadotrophic hormones which is released by the pituitary gland into the bloodstream. Follicle stimulating hormone is one of the hormones essential to pubertal development and the function of women's ovaries. In women, this hormone stimulates the growth of ovarian follicles in the ovary before the release of an egg from one follicle at ovulation. 

In testis, the immature male germ cells (spermatogonia) produce sperms by spermatogenesis, that begins at puberty. The spermatogonia (sing. spermatogonium) present on the inside wall of seminiferous tubules multiply by mitotic division and increase in numbers. Each spermatogonium is diploid and contains 46 chromosomes (in question this number is given as 40). Some of the spermatogonia called primary spermatocytes periodically undergo meiosis. A primary spermatocyte completes the first meiotic division (reduction division) leading to formation of two equal, haploid cells called secondary spermatocytes, which have only 23 chromosomes each (in question this number is given as 20). The secondary spermatocytes undergo the second meiotic division to produce four equal, haploid spermatids (chromosome number 20). The spermatids are transformed into spermatozoa (sperms) by the process called spermiogenesis. After spermiogenesis, sperm heads become embedded in the sertoli cells, and are finally released from the seminiferous tubules by the process called spermiation.

During embryonic development, the establishment of polarity along anterior/posterior, dorsal/ventral or medial/lateral axis is called as organizer phenomenon. It is a region of a developing embryo or a substance produced by such a region that is capable of inducing a specific type of development in undifferentiated tissue. 

Theca externa is the outer layer of the theca folliculi.
Theca interna is the inner, highly vascularized layer of cuboidal steroid-secreting cells, fibroblasts and collagen fibres.
Ovum is the egg cell.
Membrana granulosa consists of several layers of nucleated cells.
Antrum is the cavity in the epithelium, that envelops the oocyte.
Cumulus oophorous is a cluster of cells, that surround the oocyte both in the ovarian follicle and after ovulation. 

Each testis is oval-shaped measuring 4.5 cm long, 2.5 cm wide in adult. It is enclosed in fibrous sac called as tunica albuginea. The sac extends into a test to divide the testes into lobules. Next to tunica albuginea is tunica vaginalis, which is a continuation of membrane of abdomino-pelvic cavity. Each testis contain 800 lightly coiled seminiferous tubules, which produce thousands of sperm each second.

Embryogenesis refers to the process of division and differentiation of the embryonic cells during the early stages of embryo development. In human beings, the zygote or embryo goes through a spatial and temporal changes leading to embryogenesis involving stages such as gastrulation, germ layer formation , histogenesis, neurulation and organogenesis. Following these, the heart is the first organ to be differentiated and developed  which starts to beat and pump blood at around 21 or 22 days.

In the embryo, there are pair of ducts which are present on the lateral sides of the urogenital ridge, called as the Mullerian duct. These terminate at the sinus tubercle. This structure is present in the embryo of both the sexes. In the females they develop to form the parts of reproductive organs, whereas this structure is lost in the males but the vestigial remnant of the duct forms the appendix testis and prostatic utricle. 

Heart development refers to development of the human heart. This begins with the formation of two endocardial tubes, which merge to form the tubular heart, also called as the primitive heart tube, that loops and separates into the four chambers and paired arterial trunks, that form the adult, human heart. The heart is the first functional organ in vertebrate embryos, and in the human, beats spontaneously by week 4 of development. Hence, option A is correct.