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.