Reproductive Organs, gametes and Fertilisation

Testes and Ovaries

What you should know

• The structure and function of reproductive organs and gametes and their role in fertilisation.

• Gamete production in the testes. The roles of seminiferous tubules, interstitial cells, testosterone, prostate gland and seminal vesicles.

• Gamete production in the ovaries to include maturation of ova and the development of a follicle. Site of fertilisation in the oviduct and zygote formation.

Reproductive Organs and Gametes

Prior Knowledge

•Reproductive organs produce gametes•Male gamete- sperm•Female gamete- egg/ova•Male reproductive organ- testes•Female reproductive organ-ovary

Production of Gametes

•A germ line is the sex cells (eggs and sperm) that are used by sexually reproducing organisms to pass on genes from generation to generation.

•Gametes are produced by germline cells

MALE REPRODUCTIVE SYSTEM

PUBIC BONE

BLADDER

URETER

RECTUM

PENIS

ERECTILE TISSUE

URETHRA

TESTIS SCROTUM

EPIDIDYMIS

VAS DEFERENS/ sperm duct

SEMINAL VESICLE

PROSTATE GLAND

The testes are the site of sperm (spermatozoa) production

The testes are also the site of manufacture of the male sex hormone testosterone

Sperm are formed from germline cells in tiny tubes called Seminiferous Tubules

Seminiferous tubules unite to form coiled tubes that connect to the Sperm Duct – free swimming sperm leave the testes in the sperm duct

TESTES

SEMINIFEROUS TUBULE

INTERSTITIAL CELLS

Interstitial Cells

Between the seminiferous tubules are cells called the Interstitial CellsThese cells produce the hormone TestosteroneTestosterone passes directly into the blood stream Fertilisation depends on the motility of the sperm - motility requires a fluid medium and a source of energy

TESTES• Seminiferous tubules – produce sperm• Interstitial cells– secrete testosterone

Interstitial cells

Seminal Vesicles and Prostate

The seminal vesicles and the prostate gland are known as accessory glands

•Semen consists of 10% sperm and 90% fluid and as sperm pass down the ducts from testis to penis, (accessory) glands add various secretions

•The prostate gland and seminal vesicles secrete fluids that maintain the mobility and viability of the sperm. This fluid is called semen

Seminal Vesicles

Seminal Vesicles –secrete a liquid rich in fructose to provide energy for sperm motilitythe liquid contains hormone-like compounds that stimulate contraction of the female reproductive tractthese contractions help the sperm to reach the oviduct (where fertilisation takes place) quicker than ‘swimming’ alone

Prostate Gland

The prostate gland secretes lubricating liquid containing enzymes

These enzymes maintain the fluid at optimum viscosity for sperm motility

Just before ovulation the cells lining the female cervix secrete a watery mucus

this watery mucus is easily penetrated by sperm

FEMALE REPRODUCTIVE SYSTEM

VAGINACERVIX

UTERUS

ENDOMETRIUM

OVARY

OVIDUCT

Ovaries

Eggs or Ova are formed from germline cells in the female ovariesThe ovaries contain immature eggs at various stages of development

Ovulation is when a mature ovum is released, from the ovary, into the oviduct

Fertilisation takes place in the oviduct if sperm are present - fertilised egg or zygote develops into an embryo

GRAAFIAN FOLLICLE

Follicle

Each ovum (egg) is surrounded by a structure called a follicle which protects the ovum

The follicle secretes the female sex hormone called oestrogen

After ovulation it secretes the sex hormone progesterone, as well as oestrogen

Try these questions . . . .

1. Where in a testis are sperm produced?2. Which hormone is produced by interstitial

cells?3. Which accessory glands secrete a liquid rich in

hormone-like chemicals?4. Describe the contribution to fertilisation made

by these chemicals5. Name the structure that surrounds the egg in

an ovary

Answers . . . .

1. Seminiferous tubules2. Testosterone3. Seminal vesicles4. They stimulate the female reproductive tract

to contract, creating movements that help the sperm reach the oviduct

5. follicle