Human Reproduction: System, Fertilization, Pregnancy, and Delivery
Item 7: Human Reproductive System
Sexual Reproduction
Humans reproduce sexually. Women produce gametes called eggs, and men produce male gametes called sperm. These two cells combine to form a zygote.
Fertilization is internal; the sperm and egg bind within the female reproductive system. Humans are viviparous.
- Gamete Production: In specialized reproductive organs.
- Fertilization: The union of two gametes within the female reproductive tract, forming a single-celled zygote.
- Zygote Development: Within the female reproductive tract, the zygote becomes an embryo, then a fetus.
- Labor or Delivery: A fully formed baby is born.
- Child Development: Maturation of sexual organs and transformation into an adult capable of producing gametes and reproducing.
3. Female Reproductive System and Gametes
- Ovary: Almond-shaped and sized, attached to the uterus by a ligament.
- Fallopian Tube: Connects each ovary to the uterus.
- Clitoris: Organ with many nerve endings, providing great sensitivity.
- Uterus: A hollow organ lined with endometrium, where the fertilized egg implants.
- Vagina: Muscular canal from the uterus to the exterior.
- Labia Majora: Folds of skin between the thighs, covering external genitalia.
- Labia Minora: Thin, sensitive skin folds covered by the labia majora.
4. Male Reproductive System and Gametes
- Testicles: Glands in the scrotum that produce sperm.
- Prostate Gland: Walnut-sized gland surrounding the urethra, producing fluid to protect sperm from acidity.
- Vas Deferens & Urethra: Channels where sperm travels, converging into the urethra.
- Seminal Vesicles: Glands producing seminal fluid for sperm motility.
- Urethra: Tube for semen and urine passage, with muscular walls contracting during ejaculation.
- Epididymis: Long, coiled tube over each testicle where sperm mature.
- Penis: External organ with the glans covered by foreskin.
- Scrotum: Skin and membrane pouch housing the testicles outside the abdomen.
5. Female Reproductive Cycles
Female sex hormones are estrogen and progesterone. Estrogen, produced in the ovaries, is responsible for sexual characteristics and the menstrual cycle. Estrogen induces Graafian follicle formation and egg maturation. Estrogen levels peak around day 14 of a 28-day cycle, triggering ovulation.
6. Fertilization and Early Pregnancy
An egg can be fertilized only within 24 hours after ovulation. Fertilization occurs during sexual intercourse when the penis is introduced into the vagina, and sperm are ejaculated.
Early Pregnancy
- Placenta: Organ developing in the endometrium, connecting mother and embryo.
- Umbilical Cord: Connects the embryo to the placenta, containing two arteries and one vein for nutrient and waste exchange.
- Amniotic Sac: Fluid-filled sac surrounding and protecting the embryo.
7. Pregnancy Development
Gestation or pregnancy begins with fertilization and ends with delivery. The zygote becomes an embryo, then a fetus. The process lasts approximately 280 days (40 weeks or ten lunar months).
8. Delivery
Pregnancy ends with delivery, the birth of the baby. Delivery consists of three stages:
- Dilation: The cervix dilates, vaginal muscles relax, and uterine muscles contract rhythmically. The amniotic sac may rupture (“water breaks”).
- Expulsion: The fetus is pushed out by uterine contractions and maternal effort.
- Birth: Five to fifteen minutes after expulsion, the placenta and endometrial remains are delivered.
Childbirth Complications
- Poor Fetal Position: If the fetus’s head is not engaged in the pelvis, the expulsion phase is prolonged.
- Insufficient Cervical Dilation: Oxytocin may be administered to stimulate dilation.
- Umbilical Cord Compression: If the cord is compressed, blood flow between mother and fetus is compromised.
9. Sterility and Assisted Reproduction Techniques
Infertility is the inability to conceive.
- Male Infertility: Insufficient sperm production, abnormal sperm maturation, or blocked sperm passage.
- Female Infertility: Blocked fallopian tubes, lack of ovulation, or implantation difficulties.