Male and Female Reproductive Systems Reproduction: process by which living things produce new individuals of the same type. Fertilization: joining of an egg and a sperm. Zygote: a fertilized egg, which is produced when fertilization occurs. Chromosomes: rod-shaped structures in sex cells that carry the info that controls inherited characteristics, such as hair color.

Chromosomes Cells in the human body contain 46 chromosomes, except Sex Cells - they contain only 23 chromosomes. Male sex cell: sperm Female sex cell: egg

Male Reproductive System Testes: organ made of clusters of hundreds of tiny coiled tubes where sperm and the hormone testosterone is produced. Testosterone: controls the development of physical characteristics in men (deep voice, facial hair). Scrotum: external pouch of skin that holds the testes - keeps the testes about 2° - 3°C below normal body temp - 37°C - sperm need the slightly lower temp to develop normally.

Anatomy of the Male Reproductive System

Sperm Sperm production starts in the teenage years. Once made, the sperm travel from the testes, through the tubes and into the urethra. The sperm mixes with fluids from nearby glands producing semen - sperm and fluid. This fluid provides nutrients and an environment in which they can swim. Semen leaves the body through the penis by way of the urethra.

Anatomy of the Female Reproductive System Birth Canal

Ovaries: major role is to make eggs Ovaries: major role is to make eggs. Each month a mature egg is released which enters one of the oviducts. A female is born with all the eggs she will ever have. The average # of undeveloped eggs a female has is approx. 400,000 but she will only release about 500. Ovaries produce the hormones estrogen and progesterone. Estrogen is responsible for breast development, the widening of hips, and maturation of egg cells in the ovaries. Oviducts (or fallopian tubes): passageways for eggs and place where fertilization usually occurs.

Uterus (or womb): hollow muscular organ about the size of a pear Uterus (or womb): hollow muscular organ about the size of a pear. This is where the fertilized egg begins to develop and is “housed” within the amniotic sac until birth. Vagina: muscular passageway leading to the outside of the body. Also known as the birth canal because it is the passageway the baby uses to leave the mother’s body during the birth process.

Menstrual Cycle Monthly cycle of change in the female reproductive system. Two basic purposes: development and release of an egg for fertilization and preparation of the uterus to receive a fertilized egg.

Ovulation: the releasing of the egg into the fallopian tube Menstruation: when the egg is not fertilized, the egg and the lining of the uterus break down, the extra blood and tissue in the thickened lining of the uterus pass out of the body through the vagina

Stages of Development Male sperm: 23 chromosomes Female egg: 23 chromosomes The zygote starts to divide and become bigger, during this time and for the next 8 weeks the developing human is called an embryo. Soon after the embryo enters the uterus, it attaches itself to the wall and grows inward. Zygote: fertilized egg makes 4 day trip through oviduct- 46 chromosomes. 2 cell stage uterus 4 cell stage Umbilical cord: connects the fetus to the placenta 8 cell stage 1 month stage Birth at 9 months

The organ called the placenta provides a connection between the mother and the developing baby. Through blood vessels in the umbilical cord, which contains 2 arteries and 1 vein, food and oxygen from the mother and wastes from the developing baby are exchanged. The amniotic sac, membrane which developed into a fluid-filled sac, serves to cushion & protect the developing baby. After eight weeks of development the baby is the size of a walnut and now called a fetus.

Development of the Fetus 9th week: now called a fetus until birth, size of walnut, looks like a baby, internal organs have developed, head is about 1/2 body’s total size, has dark eye patches, fingers, and toes. By the end of the 3rd month the fetus is about 9 cm long. Between 4th and 6th months: tissues of fetus continue to develop into recognizable shapes. Bones become distinct, heartbeat can be heard with stethoscope, layer of soft hair grows over the skin, arms and legs develop more completely, and the fetus begins to move and kick - a sign of muscle growth. The fetus is now about 20 cm long and the mass of the fetus is about 700 g.

Beginning of the 4th month: fetus has developed internal organs, dark eye patches, fingers, and toes. Final 3 months: brain surface develops grooves and ridges, lungs become developed enough to carry out oxygen/carbon dioxide exchange, eyelids can open, eyelashes/eyebrows grow, fetus doubles in length. Its mass may grow to reach 3 Kg or more.

Birth - after about 9 months of development inside the uterus, the baby is ready to be born. The birth of a baby takes place in 3 stages: labor, delivery, and afterbirth. Labor: 1st stage - strong muscular contractions of the uterus - these cause the cervix to get bigger, letting the baby fit through. Delivery: 2nd stage - baby is pushed completely out of the uterus, through the vagina, and out of the mother’s body. The head usually comes first with the umbilical cord still connected from the baby to the placenta. Shortly after delivery, the umbilical cord is clamped, then cut about 5 cm from the baby’s abdomen. Afterbirth: 3rd stage - about 15 minutes after delivery, contractions push the placenta and other membranes out of the uterus through the vagina.

Work cited Human Biology and Health, Englewood, Cliffs, New Jersey 07632, Prentice-Hall Inc., ©1994-1993, pages 167-181. Science Explorer Human Biology and Health, Upper Saddle River, New Jersey 07458, Prentice-Hall Inc., ©2002-2000, pages 225-241.