Female Reproduction Systems Human Reproduction Female Reproduction Systems

Size of the Egg vs the Sperm Under the microscope, the maturing egg cell is a sphere. An egg is the size of 100 microns, or one-tenth of a millimeter. That is equivalent to the diameter of a single strand of hair. Sperm cells, the other half of the reproductive equation, are much, much smaller. In fact, sperm cells are the smallest cells in the human body.

Female Sexual Characteristics Female puberty usually begins around the age of 10 – 12 (so on average about a 1 – 2 before males begin puberty). During puberty a female will undergo primary and secondary sexual characteristic changes. Primary sexual characteristics are the female reproductive organs. Secondary sexual characteristics include: growth of underarm hair, pubic hair, and widening of the hips for child birth.

Female Sexual Characteristics Unlike a male – who does not start to produce his sperm until puberty – females have all their sex cells at birth. A female can be born with approximately two million eggs, but will have only about 400,000 by puberty. Once sexual maturity is reached during puberty a single egg matures and will be released each month.

Female Primary Sexual Characteristics

Female Primary Sexual Characteristics Vagina: Receives the penis and sperm during sexual intercourse, it is the birth canal during delivery of an offspring. Cervix: Muscular opening between the uterus and the vagina. Keeps the developing baby inside the woman. Uterus: The organ that receives the fertilized egg. Endometrium: The lining of the uterus that is rich in nutrients and provides them to the growing embryo. Fallopian Tube: A long tube that transports the egg from the ovary to the uterus. Ovary/ovaries: Where the egg cells mature.

Egg Production in the Ovary The primary female reproductive organ is the ovary, this is where the egg cells mature and are released from. Females have two ovaries located in the lower portion of the abdominal cavity one on either side of their sex organ. Inside the ovaries are follicles, each follicle contains a single immature egg. The follicles contain cells that nourish and protect the developing egg. Females are able to produce their own hormones – estrogen and progesterone – in the ovaries.

Egg Production in the Ovary

Menstrual Cycle A women’s menstrual cycle is correlated to the eggs being released in her body. A women goes through a menstrual cycle, each cycle is typically 28 days. The length of a women’s cycle can change the older they get. It can also change if one women lives with other females (for example in a dorm). This is known as the McClintock synchronization theory. When a female reaches the age of 40 - 50 she starts going through menopause and this is when she tends to stop producing mature eggs.

Menstrual Cycle Phase Description of Events Hormones Produced Days (Approximately) Flow Phase Endometrium sheds from the female uterus None 1-5 days Follicular Phase Follicles in ovaries are being developed and the egg is getting ready to be released Estrogen is produced 6 – 13 days Ovulation Egg is released from the ovary 14 Luteal Phase Corpus Luteum forms inside the ovary (it is the remains of the pocket that held the egg and the follicle) Estrogen and Progesterone are produced by the corpus luteum 15 - 28

Path of the Egg After an egg is developed and mature it is released from the ovary into the fallopian tube – usually one egg from one ovary and the next cycle it will release an egg from the other ovary. The fallopian tube allows the egg to get from the ovaries to the uterus. The endometrium, the lining of the uterus, is filled with rich nutrients, blood vessels and mucus that provides nourishment for a fertilized egg - the embryo.

Path of the Egg If no sperm is found in the fallopian tube to fertilize the egg, the egg will make its way to the uterus. Once the uterus realizes that the egg is not fertilized, it then sheds the endometrium and starts to prepare for the next cycle. The un-fertilized egg expels out through the vagina during the same time the endometrium sheds. Then, once the 28th day arrives, the cycle starts all over again.

Pregnancy If fertilization does occur, it must happen within 24 hours of ovulation (when the egg is released) or the egg degenerates. If the egg is fertilized in the fallopian tube, the two haploids fuse together to produce a zygote with 23 pairs of chromosomes. After fertilization, the mass of cells created in the zygote become an embryo.

Pregnancy The Embryo reaches the uterus where it will implant into the endometrium. During pregnancy the menstrual cycle stops completely while the mother-to-be awaits for the birth of her baby. Upon the birth of an offspring, females produce a hormone called prolactin. It causes milk to be produced to feed the baby.

Assignment Do the “Try This” on page 115. Follow all the steps from 1 – 4 and answer questions a, b, and c. Textbook Pg 116 – Questions 1, 3, 4, 6, 7, 8, 9, 12, 13, 14, 16.