Human Reproduction Mr. Ramos Introduction to Human Reproduction Reproduction is a process by which organisms make more organisms. Reproduction leads to population growth. Reproduction in humans is called sexual reproduction. Sexual reproduction results in genetic diversity. The Male Reproductive System Main function is to make sperm, or male sex cells (gametes) The Male Reproductive System The second most important function is to deliver the sperm into the female. The penis delivers the sperm. Sperm is made in the testes after puberty and matures in the epididymis. The testes (or testicles) hang in a baglike structure called the scrotum. Having the testes outside the pelvis keeps them at a lower temperature. The testes also produce the hormone testosterone The Male Reproductive System The urethra is a tube where urine and sperm leave the penis in males. Men and women have a urethra. The seminal vesicles, prostate gland, and bulbourethral glands produce the liquid called semen. The Female Reproductive System The main function of the female reproductive system is to make egg cells (ovum) and to carry the developing offspring. The Female Reproductive System The vagina is the birth canal. It is a tube that leads from an opening outside of the body to the uterus. The uterus, or womb, is a thick muscular organ that hold and nourishes the developing offspring. The end of the vagina and beginning of the uterus is called the cervix. The Female Reproductive System The female sex cells (egg cells) are produced in the ovaries. The egg is released in a process called ovulation and moves towards the fallopian tube, waiting to meet the sperm. Fertilization is when an egg cell and a sperm cell unite. Fertilization occurs in the fallopian tubes. A zygote is a combination of a sperm and egg cell. Embryonic and Fetal Development It all begins when a male ejaculates inside a female. The sperm and egg unite to form a zygote, and the zygote eventually becomes a baby. The zygote goes through a series of cell divisions called cleavage: 2, 4, 8, morula, blastula, gastrula, embryo. The period from fertilization to birth is called pregnancy or the gestation period. First Trimester Pregnancy in humans is discussed in three-month periods called trimesters. During the first trimester (first three months) 1. The zygote divides several times to form a blastula. 2. Human embryo implants itself on the uterus about 8 to 9 days after fertilization. 3. After implantation, cells continue to divide to form a gastrula. The gastrula is composed of 3 germ layers: ectoderm, mesoderm, endoderm. 4. Cell differentiation begins. • • • 5. Ectoderm forms into skin, nerves, and sense organs. Mesoderm forms into bones, muscles, and connective tissue. Endoderm forms the digestive system and lungs. The embryo is now called a fetus. Second Trimester The second trimester are months 4, 5, and 6. The mother starts to feel the fetus moving. By the end of the second trimester, the fetus has fully developed eyes, and the lungs are starting to develop. Third Trimester The fetus continues to grow. The brain develops and the fetus has regular breathing motions by the 7th month, though the lungs are still developing.