Sexual Reproduction in Plants and Animals

The acrosome is the part of the sperm containing proteolytic enzymes to digest the zona pellucida. It is exposed by the process of capacitation. Then, under the influence of substances released by corona radiata cells, it releases its proteolytic enzymes and penetrates the oocyte.

On the superior end of the labia minora is a small mass of erectile tissue known as the clitoris that contains many nerve endings for sensing sexual pleasure.

Each microsporangium is lined with a nutritive tissue layer called the tapetum and initially contains diploid pollen mother cells.

Within the megagametophyte one of the two sperm unites with the egg, forming a zygote, and the second sperm enters the central cell forming the endosperm mother cell, which completes the double fertilisation process.

The non-vascular plant usually grows in the moist and shady places. The moist environment is essential for easy uptake of the water, since they lack the vascular tissues like the xylem and the phloem.

Two large green hemispherical structures which enclose the embryonic axis is called as the cotyledons. The cotyledons may be one or two in number depending on the type of plant. The cotyledons are important because it give nutrients during the early development of the plant before starting the process of photosynthesis.

 Bulbil is a speical multicellular body essentially meant for reproduction. In Agave the floral buds are modified into bulbils. These bulbils get detached, come in contact with the soil and develop into new plants. In Dioscorea the axillary bud develops into a bulbil. This bulbil detaches from the mother plant and grows up into a new independent one.

The secretion of this gland is more serous in dogs and more mucous in bulls. It serves to promote the movement of spermatozoa in all the mammals and to form a vaginal plug.  

Runners are horizontally oriented stems that grow along the soil surface. Their function is vegetative production. For example: number of grasses have stolons. Strawberries are normally propagated asexually by two different methods: runners (stolons) and crown division.

The tunica vaginalis is the serous covering of the testis. It is a pouch of serous membrane, derived from the processus vaginalis of the peritoneum, which in the fetus preceded the descent of the testis from the abdomen into the scrotum.

Offshoots applies to lateral branches on stems of monocots. Date palm, pineapple, banana, and orchids produce offshoots. Bamboo also propagate from offshoots, if left unchecked they will form whole forests of plants.

The developing embryo has two main populations of cells: an inner cell mass and a trophectoderm. The trophectoderm cells lie at the outer surface of the developing embryo and will become the placenta.

Basal cells are the shorter, pyramid-shaped cells which contact the basal lamina but taper off before their apical surfaces reach the lumen.These are thought to be undifferentiated precursors of principal cells. 

The raphe is the visible ridge between the lateral halves of the penis, found on the ventral or underside of the penis, running from the meatus (opening of the urethra) across the scrotum to the perineum (area between scrotum and anus).

A spermatozoon  is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing a Y chromosome will lead to a male (XY) offspring, while one bearing an X chromosome will lead to a female (XX) offspring.

Antonie Philips van Leeuwenhoek  is commonly known as  the Father of Microbiology. Sperm cells were first observed by him.

Sertoli cells are activated by follicle-stimulating hormone and has FSH-receptor on its membranes. It is specifically located in the convoluted seminiferous tubules

The internal pudendal arteries serve as the penile blood supply by entering the penis dorsally and running deep into the tissues of the corpora cavernosa. The internal pudendal artery becomes the penile artery.

As a consequence of stimulation with luteinising hormone the interstitial cells (Leydig) secrete testosterone into the intertubular tissue, where it is absorbed by blood vessels, lymphatics, and the seminiferous tubules.

The ampulla is the second portion of the fallopian tube. It is an intermediate dilated portion, which curves over the ovary. It is the most common site of mouse and human fertilisation.