Human Reproduction

The Sexual Life Cycle

Structures Drawings – labels and functions Male reproductive system Female reproduction system

nucleus containing DNA Sex cells – sperm In males, the sex cells are called sperm. tail middle piece head cell membrane nucleus containing DNA Sperm are produced in sex organs called testes.

The Testis These cells secrete the male sex hormone called testosterone When sexual maturity (puberty) occurs, testosterone is responsible for the development of male characteristics Such as The growth of hair on the face, armpits and pubic areas Lowering of voice Development of muscles which give males their shape such as broad shoulders

What happens during puberty? Humans are born with a complete set of sex organs. However, they do not usually become active until between the ages of 10 and 18. In males, the testes start to make sperm, and in females, the ovaries start to release eggs. This stage of development is called puberty. During this important time, many changes take place in the bodies of young men and women.

Ducts responsible for carrying the spermatozoa The tubes responsible for carrying the spermatozoa include: Epididymis Vas deferens ejaculatory ducts urethra

The Testis These cells are rich in glycogen This glycogen serves as nutrients for the spermatids as they develop into sperm cells Between the seminiferous tubules are intestitial cells called cells of Leydig

Functions of the accessory glands Seminal Vesicles Secretes a fluid that nourishes and enables sperm to move. Prostate gland Secretes an alkaline fluid that neutralizes the acidity. Cowper’s glands Two glands by prostate that secrete a fluid that neutralizes acidity.

The male reproductive system

The female reproductive system

An overview This system consists of: A pair of ovaries A fallopian tube or oviduct The uterus or womb The vagina or birth canal The vulva or external opening

The Ovaries When puberty occurs, the female sex hormones are responsible for the development of female characteristics Such as: Increase in size of breasts Development of pubic and armpit hair And menstruation

The Uterus Two fallopian tubes open into the uterus which is pear shaped, hollow organ with muscular walls The ling of the uterus is called endometrium, is richly supplied with blood vessels

The Ovaries The germinal epithelium produces the follicles Oogenesis takes place within the follicles to produce the ova Follicles secrete the female hormones oestrogen and progesterone

The Uterus The neck of the uterus, called the cervix, extends into the vagina The uterus serves for the attachment of the embryo Fertilisation takes place

Processes Gametogenesis Spermatogenesis Oogenesis

Gametogenesis Spermatogenesis refers to the process by which spermatozoa are produced from the germinal epithelium of the testis Oogenesis is the process where ova is produced from germinal epithelium of the ovaries

Spermatogenesis At puberty, the germinal epithelial cells lining the seminiferous tubules start to produce spermatozoa by meiosis Each germinal epithelium is diploid and in humans the diploid number is 46 Since the sperm is produced by meiosis, each one will be haploid with 22 single chromosome and X or Y chromosome

Spermatogenesis The process is as follows: Cells of germinal epithelium become actively dividing cells called spermatogonia Each spermatogonium, which is diploid (2n), enlarges to become a primary spermatocyte (also 2n)

Spermatogenesis Primary spermatocyte undergoes the first meiotic division forming 2 haploid secondary spermatocytes Each secondary spermatocyte undergoes the second meiotic division to produce 2 spermatids Each spermatid matures to form a spermatozoan Each spermatozoan is made up of a head, a middle-piece and a tail