The Male and Female Reproductive Systems Mrs. Mudd 8th Grade Science

Objectives Define sexual reproduction Describe the structures and functions of the male reproductive system Describe the structures and functions of the female reproductive system Sequence the events that occur during the menstrual cycle

What is sexual reproduction? Sexual reproduction involves the production of eggs by the female and sperm by the male. The egg and sperm join together during fertilization. We begin life as a single cell. That single cell was produced by the joining of two other cells.

What is fertilization? The joining of a sperm and an egg. When fertilization occurs, a fertilized egg, or zygote, is produced. Every cell in your body is a descendant from the single cell that formed during fertilization.

Chromosomes Sex cells contain chromosomes Rod-shaped structures Carry information that controls inherited characteristics Every cell in the human body that has a nucleus, except the sex cells, contains 46 chromosomes.

Human chromosomes

Sex Cells Each sex cell contains half the number of Chromosomes. 23 in the sperm cell, and 23 in the egg During fertilization the chromosomes join together resulting in a zygote with 46 chromosomes. The zygote contains all of the information needed to produce a new human being.

Male Reproductive System The male reproductive system is specialized to produce sperm and the hormone testosterone. The structures include the testes, scrotum, and the penis.

Testes The oval shaped testes are the organs of the male reproductive system in which sperm are produced. The testes consist of clusters of tiny coiled tubes. Sperm is formed inside the tubes Testosterone is also produced. Controls the development of physical characteristics of mature men.

Male Characteristics Facial Hair Deepening of the voice Broadening of the shoulders Ability to produce sperm

Sperm Production Testes are located in an external pouch called the scrotum. Keeps the testes several degrees below normal body temperature. Sperm need a cooler environment Production begins in the teenage years. Tiny package of chromosomes that can swim.

Path of the sperm cells Once formed the sperm cells pass through other stuctures. During this time they mix with fluids produced by nearby glands. The mixture of sperm and fluid is call semen. Contains 5 to 10 million sperm per drop. Semen contains nutrients that the moving sperm use for energy.

Continued Path Semen leaves the body through an organ called the penis The tube through which the semen travel is called the urethra. Urine also leaves the body through the urethra. When semen passes through, muscles near the bladder contract. Prevents urine and semen from mixing.

Female Reproductive System The role of the female system is to produce eggs. Nourish a developing baby until birth. The organs of the female reproductive system include the ovaries, fallopian tubes, uterus, and vagina.

The Ovaries The female structures that produces eggs. Located slightly below the waist. One on each side of the body. The name comes from the Latin word meaning “eggs”.

Female Hormones Like the testes, the ovaries also are endocrine glands that produce hormones. Estrogen triggers the development of female characteristics. Progesterone varies during the menstrual cycle. This Hormone also varies during pregnancy. During this time is prevents labor.

Path of the egg Ovaries are located near a fallopian tube. Fallopian tubes are passageways for eggs to travel from the ovary to the uterus. Each month , one of the ovaries releases an egg. The egg enters the fallopian tube. Fertilization usually occurs within the fallopian tube.

Traveling egg continued The egg moves through the tube which leads to the uterus. The uterus is a hollow muscular organ about he size of a pear. If it had been fertilized, it would attach to the wall of the uterus.

continued An egg that has not been fertilized starts to break down in the uterus. It leaves the uterus through an opening called the cervix. The egg then enters the vagina. The vagina is a muscular passageway leading to the outside of the body. The vagina, or birth canal, is the passageway through which a baby leaves the mother’s body.

The Menstrual Cycle The female reproductive system becomes mature during the teenage years. There are about 400,000 undeveloped eggs in the ovaries. Only about 500 of those eggs will actually leave the ovaries and reach the uterus. An egg is released once a month. The monthly changes that occur in the female reproductive system is called the menstrual cycle. During the menstrual cycle, an egg develops in an ovary. At the same time the uterus prepares for the arrival of an embryo. The body prepares itself for pregnancy, which begins after fertilization.

Stages of the Menstrual Cycle Early in the cycle an egg matures in one of the ovaries. At the same time, the lining of the uterus begins to thicken. About halfway through the cycle, the egg is released from the ovary into the fallopian tube. This process is called ovulation. Once the egg is released, it can be fertilized during the next few days if sperm are present.

continued If the egg is not fertilized, it begins to break down. The lining of the uterus also breaks down. The extra blood and tissue of the thickened lining pass out of the body through the vagina. This process is called menstruation. On average this lasts about six days. At the same time menstruation takes place, a new egg begins to mature in the ovary. The cycle continues.

Endocrine Control The menstrual cycle is controlled by hormones in the endocrine system. Hormones trigger a girls’ first menstruation. Sometime between the ages of 10 and 14 years. Women continue to menstruate until the age of 50. At that age, production of sex hormones drop. As a result, the ovaries stop releasing mature eggs.