Human Reproductive System Quiz

Fertilization and Fetal Development

• Gametogenesis is the development of ova in women and sperm in men.
• Oogenesis is the formation of female gametes (ova) in the ovary. It begins during prenatal life, and by the 30th week of gestation, the female fetus has all the ova she will ever have.
• Spermatogenesis is the formation of sperm (male gametes) in the testes. It starts during puberty and takes about 70 days to complete.
  • The male gamete determines the sex of the new baby.
  • The ovum carries only an X chromosome.
  • Each mature sperm contains 23 chromosomes: 22 autosomes and either an X or a Y chromosome.
  • If an X-bearing spermatozoon fertilizes the ovum, the baby is a girl.
  • If a Y-bearing spermatozoon fertilizes the ovum, the baby is a boy.

Conception

• Natural conception is the interaction of many factors during ovulation and ejaculation, including correct timing and healthy, mature, motile sperm entering the vagina.
• Fertilization is the union of sperm and ovum. Stages after fertilization include:
  • Zygote
  • Morula
  • Blastocyst
• The inner cell mass develops into the fetus.
• The outer cell mass forms the placenta and membranes.

Preparation for Conception in the Female

• Ovulation occurs approximately 14 days before the next menstrual period.
• The ovum is transported through the fallopian tube via muscular action and cilia movement.
• Fertilization typically occurs in the ampulla (part of the fallopian tube).

Preparation for Conception in the Male

• Ejaculation during sexual intercourse releases 35 to 200 million sperms into the upper vagina and over the cervix.
• Sperms are suspended in seminal fluid, which nourishes and protects them from the vagina's acidic environment.

Transport of Sperm in the Female Reproductive Tract

• Sperm's whip-like movement propels them through the cervix, uterus, and fallopian tubes.
• Uterine contractions induced by prostaglandins in the seminal fluid aid sperm movement towards the ovum.

Preparation of Sperm for Fertilization

• Sperm undergo changes called capacitation, in which the glycoprotein coat and seminal proteins are removed from the acrosome, allowing them to better penetrate the protective layers surrounding the ovum.
  • Hyaluronidase and acrosin are released to digest a pathway.
• The sperms' tails beat harder to propel them toward the center of the ovum.

Fertilization

• One spermatozoon enters the ovum, and the genetic material merges.
• The zona pellucida prevents other sperm from entering.
• Cell membranes fuse and break down, allowing the sperm head's contents into the ovum's cytoplasm.

Preembryonic Period

• This period spans the first two weeks after conception.
• The fertilized ovum (zygote) enters the uterus around the fourth day after conception.
• Stages: 2-cell, 4-cell, Morula, Blastocyst
  • Trophoblast forms the protective layer.
  • Inner cell mass is the future embryo.

Embryonic Period

• This period of development extends from the start of the third to the eighth week after conception.
• Basic structures of all major body organs are completed during this period.
• Cells differentiate from undifferentiated cells.
• Key organ systems are in place and beginning to function.

Germ Layers

• Ectoderm forms the brain, spinal cord, peripheral nervous system, sensory organs (eye, ear, nose), epidermis, and hair.
• Mesoderm forms the cartilage, bone, connective tissue, muscles, heart, blood vessels, blood cells, reproductive organs, and lymphatic system.
• Endoderm forms the lining of the gastrointestinal and respiratory tracts, glands (thyroid, parathyroid, thymus, liver, pancreas), urinary bladder, lining of the ear, and other tissues.

Fetal Period

• This period begins at 9 weeks after conception and ends with birth.
• Major organ systems are now present in their basic form.
• Further development of structure and function of all organ systems continues throughout this period.

Auxiliary Structures

• Placenta: A thick, disc-shaped organ with maternal and fetal components. Involved in metabolic, transfer, and endocrine functions.
• Fetal membranes: The amnion and chorion form the protective layer; fluid is comprised of fetal urine and maternal blood. Amniotic fluid functions include protection, development, and movement.
• Umbilical cord: Connects the fetus to the placenta; two arteries carry deoxygenated blood and waste away from the fetus while one vein transfers oxygenated blood. Coiled structure and Wharton's jelly prevent occlusion.