Reproductive System

This chapter desribes the male and female reproductive systems, the production of sperm and ova, fertilisation, gestation and birth.

Objectives

After completing this section, you should know:

• the role of mitosis and meiosis in the production of gametes (sperm and ova)
• that gametes are haploid cells
• that fertilization forms a diploid zygote
• the major parts of the male reproductive system and their functions
• the route sperm travel along the male reproductive tract to reach the penis
• the structure of a sperm and the difference between sperm and semen
• the difference between infertility and impotence
• the main parts of the female reproductive system and their functions
• the ovarian cycle and the roles of FSH, LH, oestrogen and progesterone
• the oestrous cycle and the signs of heat in rodents, dogs, cats and cattle
• the process of fertilization and where it occurs in the female tract
• what a morula and a blastocyst are
• what the placenta is and its functions

Summary

• mitosis takes place in somatic cell and meiosis always takes place in germ cells.
• Haploid gametes (sperm and ova) are produced by meiosis in the gonads (testes and ovaries).
• Fertilisation involves the fusing of the gametes to form a diploid zygote.
• The male reproductive system consists of a pair of testes that produce sperm (or spermatozoa), ducts that transport the sperm to the penis and glands that add secretions to the sperm to make semen.
• Sperm are produced in the seminiferous tubules, are stored in the epididymis and travel via the vas deferens or sperm duct to the junction of the bladder and the urethra where various accessory glands add secretions. The fluid is now called semen and is ejaculated into the female system down the urethra that runs down the centre of the penis.
• Sperm consist of a head, a midpiece and a tail.
• Infertility is the inability of sperm to fertilize an egg while impotence is the inability to copulate successfully.
• The female reproductive system consists of a pair of ovaries that produce ova and fallopian tubes where fertilisation occurs and which carry the fertilised ovum to the uterus. Growth of the foetus takes place here. The cervix separates the uterus from the vagina, the birth canal and where the sperm are deposited.
• The ovarian cycle refers to the series of changes in the ovary during which the follicle matures, the ovum is shed and the corpus luteum develops.
• The oestrous cycle is the sequence of hormonal changes that occurs through the ovarian cycle. It is initiated by the secretion of follicle stimulating hormone (F.S.H.), by the anterior pituitary gland which stimulates the follicle to develop. The follicle secretes oestrogen which stimulates mammary gland development. luteinising hormone (L.H.) from the anterior pituitary initiates ovulation and stimulates the corpus luteum to develop. The corpus luteum produces progesterone that prepares the lining of the uterus for the fertilised ovum.
• Signs of oestrous or heat differ. A bitch has a blood stained discharge, female cats and rats are restless and show the lordosis response, while cows mount other cows, bellow and have a discharge from the vulva.
• After fertilisation in the fallopian tube the zygote divides over and over by mitosis to become a ball of cells called a morula. Division continues to form a hollow ball of cells called the blastocyst. This is the stage that implants in the uterus.
• The placenta, umbilical cord and foetal membranes (known as the placenta) protect and provide the developing foetus with nutrients and remove waste products.

Learning Activities

Library of Resources

Presentations and Blackboard quizzes can be accessed by students of Otago Polytechnic.