- Gametogenesis is the process of formation of gametes (sperms and ova) by meiosis.
- In males, sperm production starts at puberty and continues throughout life in the testes.
- In females, a fixed number of immature oocytes are present at birth; one ovum matures monthly from puberty until menopause (around 45–50 years), when reproductive functions stop.
Definitions [12]
Definition: Menstrual Cycle
The rhythmic series of changes in the sex organs throughout the reproductive life of a female primate (e.g., monkeys, apes, and human beings) from puberty to menopause is called the menstrual cycle (L. mensis = month, lunar month).
Define ovulation.
The release of the ovum from the ovary is called ovulation.
Define: Menarche
It is the stage when a girl menstruates for the first time.
Define gametogenesis.
Gametogenesis is the process of formation of gametes i.e., sperms and ovary from the primary sex organs in all sexually reproducing organisms. Meiosis plays the most significant role in the process of gametogenesis.
Definition: Gametogenesis
Gametogenesis is the process by which male and female primary sex organs produce gametes (sperms and ova).
Definition: Gametogenesis
Gametogenesis is the process by which male and female gametes are formed from germinal cells in the gonads through a series of developmental stages.
Define lifespan.
The period from birth to the natural death of the organism represents its life span.
Define spermiation.
Spermiation is the process of releasing mature spermatozoa. In this, spermatozoa are shed into the lumen of the seminiferous tubule for transport.
After spermiogenesis, sperm heads become embeded in sertoli cells from which they obtain their nutrition and finally get released into the lumen of seminiferous tubules. This process of release of mature sperms from sertoli cells is called spermiation.
Define spermiogenesis.
Spermiogenesis is the process of transforming spermatids into mature, flagellated spermatozoa (sperms).
The process of transformation of a circular spermatid to a spermatozoon is called spermiogenesis.
Define.
Fertilization
The formation of a zygote by the union of male and female gametes is known as fertilization.
Definition: Fertilization in Human
The fusion of the male gamete (sperm) and female gamete (ovum) to form a zygote is called fertilisation.
or
Formation of zygote by union of sperm and ovum is called as fertilization.
Definition: Implantation
The process of the blastocyst embedding itself into the endometrial lining of the uterus about 5–7 days after ovulation is called implantation.
or
The process of fixing of the blastocyst to the wall of the uterus/endometrium is termed implantation.
Key Points
Key Points: Gametogenesis
Key Points: Fertilization in Human
- Fertilisation is the union of sperm and ovum to form a zygote and is internal in humans.
- During copulation, millions of sperms are ejaculated into the vagina, but only one sperm fertilises the ovum in the oviduct.
- The acrosome of the sperm releases enzymes that help it penetrate the egg membrane; chemical changes then prevent entry of other sperms.
- Fusion of sperm nucleus and egg nucleus restores the diploid chromosome number (46) in the zygote.
- From puberty to menopause (45–50 years), only about 400 ova are released; ageing oocytes may lead to chromosomal abnormalities if fertilised.
- Gametes are formed by meiosis: sperms are of two types (22+X or 22+Y), while ova are of one type (22+X); meiosis in ova completes during fertilisation.
