Testosterone is a hormone that stimulates changes in a boy’s body as he develops into an adult during puberty.
Scrotum: Pouch of skin containing the testes. Hangs outside body. Keeps testes cooled because sperm cells need less than 37°C.
Sperm duct: Connects tubules to urethra.
Urethra is a duct that brings urine out of the body from the bladder.
Prostate gland: Secretes fluid that mixes with sperm to form semen, which nourishes the sperm and helps them move.Sugars are used as an energy source for respiration.
Seminal vesicles: Glands that produce a nutrient-rich, sugary fluid that provides energy for the sperm to swim. This fluid is a major component of semen.
Penis: An organ that transfers semen into the female reproductive system during sexual intercourse.
The flagellum(tail) is a long, whip-like structure that extends the back of the sperm cell.
Provides movement for sperm cell.
By lashing back and forth, the flagellum propels through the cervix and uterus toward the oviduct, where fertilization occurs.
Sperm cells have a high concentration of mitochondria packed into the section between the head and the tail.
Mitochondria are the site of aerobic respiration.
Provides energy for the flagellum to beat. Without this energy source, the sperm would not be able to sustain the long journey to the egg.
The acrosome is a specialized vesicle (a small sac) located at the very front of the sperm’s head.
It contains digestive enzymes.
When the sperm contacts an egg, these enzymes are released to digest a pathway through the jelly coat of the egg cell. This allows the sperm nucleus to enter the egg and fuse with the nucleus.
Ovaries: Female sex organs that produce the female gametes (ova or eggs).
Oviducts: Narrow tubes that connect the ovaries to the uterus and contains cilia to push the egg along the oviduct. Also uses peristalsis. Site of fertilization.
Fertilization is the fusion of nuclei from a male gamete (sperm) and a female gamete (egg cell).
Uterus: Organ in the center of the pelvic cavity. Site of implantation of the embryo. Supports fetus by providing a thick, blood-rich lining (endometrium) and muscular walls that contract during birth.
Cervix: Ring of muscle at the lower end of the uterus. Holds developing fetus in place during pregnancy. Dilates during labor to allow baby to pass into the vagina.
Vagina: Muscular tube leading from cervix to outside of body. Site where sperm is deposited during sexual intercourse. Acts as birth canal during childbirth.
The egg cell contains a large volume of cytoplasm which acts as an energy store.
Rich in nutrients. Contains the yolk.
Provides necessary energy and raw materials for the early development of the embryo. After fertilization, the zygote must divide many times as it travels down the oviduct toward the uterus; the energy store sustains it until it can implant in the uterus lining and begin receiving nutrients from the mother.
The egg is surrounded by a specialized outer layer known as the jelly coat. This layer has two critical roles during fertilization:
First, selection. It contains receptor sites that ensures only sperm from the same species can bind to and penetrate the egg.
Second, the fertilization membrane. Immediately after the first sperm nucleus enters the egg, the jelly coat undergoes a chemical change that makes it harden or become impenetrable.
The function of the jelly coat prevents more than one sperm cell penetrating the egg. If multiple sperm fertilized one egg, there would be too many sets of chromosomes and would not survive.
Umbilical cord: Tube-like structure connecting fetus to placenta. Contains blood vessels that contains blood vessels that transport substances between placenta and fetus.
The umbilical vein carries oxygenated blood and nutrients (e.g. glucose/amino acids, oxygen, mineral ions/vitamins, and water)to baby.
The umbilical artery carries deoxygenated blood and waste products (e.g. $CO_{2}$, urea, water)away from baby.
Placenta: Disc-shaped organ embedded in the wall of uterus, connected to fetus by umbilical cord. Exchanges materials, removes waste, barrier from pathogens, and produces hormone (progesterone, maintain lining of uterus during pregnancy).
Some pathogens and toxins can pass across the placenta and affect the fetus.
Amniotic sac: Tough, thin, transparent membrane that encloses the fetus and amniotic fluid. Contains amniotic fluid and prevents infections from reaching the fetus from the vagina.
Amniotic fluid: Liquid that fills the amniotic sac, surrounds the developing fetus. Acts as a shock absorber, preventing the fetus from physical impact or injury. Maintains constant temperature. Allows fetus to move freely for bone and muscle development.
