Sexual Reproduction in Plants and Animals

A structure within the scrotum attached to the backside of the testis

Endosperm is formed when the two sperm nuclei inside a pollen grain reach the interior of an embryo sac or female gametophyte. One sperm nucleus fertilizes the egg, forming a zygote, while the other sperm nucleus usually fuses with the two polar nuclei at the center of the embryo sac, forming a primary endosperm cell its nucleus is often called the triple fusion nucleus resulting in a triploid of endosperm nuclues.

Sperms are thought to retain fertilising capability for upto 1-3 days once they have entered the female genital tract.

The acrosome is a specialised structure that is inside the tip of the sperm cell. It is derived from the Golgi complex during the maturation of the sperm. It is basically a storage vesicle that contains hydrolytic enzymes that digest proteins and complex sugars. The contents of the acrosome are secreted once the sperm makes contact with the egg. These enzymes will break down the zona pellucida, forming a thin path that allows the sperm to approach the egg and fuse with its cytoplasm.

After a female egg is fertilized, it is known as a zygote. Once the egg is fertilized, the zygote begins a two-week period of rapid cell division and will eventually become an embryo.

Leydig cells are found in the testicles next to the seminiferous tubules, where sperm is produced within the testes. Leydig cells are also known as interstitial cells of Leydig. Leydig cells play a vital role in maintaining proper levels of male hormones, including testosterone.

Ejaculation is the expulsion of seminal fluid from the urethra of the penis during orgasm. So, sperms are released by the ejaculation.

The external female genitals are collectively referred to as vulva.

Vasectomy is a method of male sterilization in which a portion of the vas deferens is removed. It is a surgical procedure during which the vas deferens the tubes that carry sperm from the testes  are severed. Vasectomy is a very safe and permanent means of male contraception, though it can be reversed should the need arise.

Fertilization occurs in oviduct. It is a either of a pair of long narrow ducts located in the human female abdominal cavity that transport the male sperm cells to the egg & provide a suitable environment for fertilization, and transport the egg from the ovary, where it is produced, to the central channel (lumen) of the uterus.

At the tip of the filament there is a bag like structure called the anther which contains thousands of pollen grains .The anther when ripe bursts open and releases all the pollen into the air or they settle on top of the stamen.

The pollen tube arises from the tube nucleus inside the pollen grain and grows through the tissue of the style and ovary. It has two male nuclei. Eventually, the pollen tube reaches the ovule, permitting the sperm nuclei to reach the ovule and fertilize the egg cells.

Menopause is the transition period in a woman's life when her ovaries stop producing eggs, her body produces less estrogen and progesterone, and menstruation becomes less frequent, eventually stopping altogether. It occurs between the ages of 45 and 55.

The vas deferens is a narrow tube of the male reproductive system that carries sperm from the epididymis into the body. There are two such tubes, each located on the sides of each testicle. Each tube is about 11.8 inches (30 cm) long and is composed of smooth muscle.

The testicles (also called testes) are part of the male reproductive system. The testicles are two oval organs about the size of large olives. They are located inside the scrotum, the loose sac of skin that hangs behind the penis. The testicles make the male hormones, including testosterone, and produce sperm.

Calyx is one of the main parts of a flower. It is the first whorl. It is made up of sepals and is green in color. Its function is to protect the flower during the bud stage.

Spermatogenesis is the process of producing sperm with half the number of chromosomes (hapliod) as somatic cells.The germ cells progress first from the diploid to haploid state and then change shape to become spermatozoa.The process of spermatogenesis then allows the recombination of male and female haploid gametes at fertilization..Spermatogenesis occurs in medullary sex cords known as seminiferous tubules.

The pollen grains are transferred from the anther to the stigma of the same flower. It occurs in bisexual flowers.

This is another important part of a flower .This is the second whorl. It is made up of 4,5 or 6 or more  petals . They are colorful,sweet smelling with nectar to attract insects and birds for pollination.

LH is produced by the pituitary gland.In women. It helps regulate the menstrual cycle and egg production i.e.ovulation. The level of LH in a woman's body varies with the phase of the menstrual cycle. It increases rapidly just before ovulation occurs, about midway through the cycle (day 14 of a 28-day cycle). This is called an LH surge.

The corpus luteum produces progesterone. Progesterone makes the lining of the uterus thick for implantation and is necessary to sustain a healthy pregnancy. The corpus luteum produces progesterone until the placenta begins to take over progesterone production around ten weeks gestation.

Implantation may be defined as the attachment of the fertilized egg to the uterine wall or in other words attaching the embryo with the uterus .It typically happens seven to ten days after ovulation, but it can happen a few days earlier or later as well.

The first menstrual period is referred to as menarche. Each woman has her own individual cycle, usually lasting between 21 and 40 days. The beginning of each cycle is marked by the period. Usually lasting between 3 and 7 days.

Puberty is the time in life when a person becomes sexually mature. It is a physical change that usually happens between ages 10 and 14 for girls and ages 12 and 16 for boys. It is the time at which a growing boy or girl begins the process of sexual maturation.