HUMAN REPRODUCTION, GROWTH, & DEVELOPMENT OCS Biology Mrs. Bonifay

Human Reproduction Humans reproduce sexually. A male parent fertilizes an egg inside the female body. The fertilized egg develops inside the female body.

The Human Male Reproductive System The testes produce sperm cells. The testes are outside the body in a sac called the scrotum. It is about 2 degrees Celsius cooler than the rest of the body. This helps keep the sperm cells alive because they are sensitive to heat.

The Human Male Reproductive System The testes also produce testosterone, the male sex hormone which is important to the development of male sexual traits and the production of sperm. Beginning at puberty, the testes make more than 200 million sperm cells every day. Males are usually able to produce sperm from puberty through the rest of their lives.

The Human Male Reproductive System The penis is the external male organ which delivers the sperm to the female body. Before this happens, blood flows into the tissues of the penis causing it to lengthen and become rigid, or erect. The erect penis is inserted into a tube-like canal in the female’s body called the vagina.

The Human Male Reproductive System Sperm cells leave the male body through a tube in the penis called the urethra. The prostate gland, which produces fluid that mixes with the sperm cells, connects to the urethra. The mixture of fluid and sperm cells is called semen. Urine also leaves the male body through the urethra; HOWEVER, urine and semen do NOT leave at the same time.

The Human Female Reproductive System Females are born with about 400,000 egg cells that are produced and stored in the ovaries. The ovaries also produce estrogen and progesterone which are female sex hormones that regulate female reproductive development.

The Human Female Reproductive System One egg is usually released from one of the two ovaries about every 28 days. This is called ovulation. The egg travels down the fallopian tube, and if sperm are present, a sperm cell may fertilize the egg in the fallopian tube. The fertilized egg will develop into an embryo which then travels to the uterus, attaching to the blood-rich lining of the uterus.

The Human Female Reproductive System If the egg is not fertilized, it will pass out of the female body. When the unfertilized egg, blood, and pieces of the lining of the uterus pass out of the female body through the vagina, this is called menstruation.

The Human Female Reproductive System: PREGNANCY The time a fertilized egg develops into a baby inside the female body is called pregnancy. The embryo forms a placenta. The umbilical cord connects the placenta to the embryo. This where the food and oxygen pass from the mother’s body to the embryo. The embryo’s wastes pass out of the mother’s body along with her own wastes.

The Human Female Reproductive System: PREGNANCY An embryo takes about 9 months to become a fully developed baby.

The Human Female Reproductive System: PREGNANCY After about 3 weeks, the embryo’s heart begins to beat; blood vessels form rapidly; the body has a head and buds for arms and legs. The embryo is smaller than a fingernail. All vertebrates look similar in the early stages of development.

The Human Female Reproductive System: PREGNANCY At about 4 weeks, tiny hands begin to show fingers, and eyes appear as dark spots. After eight weeks, the embryo is called a fetus. It has all the major structures of an adult.

Birth of a Baby Usually, when the fetus reaches full size, the uterus begins to contract (squeeze together). These contractions push the baby out of the uterus through the vagina. The mother pushes the placenta out soon after the birth of the baby.

Parental Care A human baby is born helpless. They are not able to take care of themselves for many years. The care humans give their offspring is one reason for the high survival rate of humans after birth.

Adolescence The teenage years for a human is called adolescence. Rapid growth and physical changes take place during puberty, which occurs at the beginning of adolescence. Name some changes that occur during adolescence.