Human Reproductive System: Core Concepts
Human Reproduction: Core Concepts
The zygote is the first cell of a new living organism. The genetic material of this cell results from the combination of genetic material from the sperm and the egg.
The placenta links the mother’s circulatory system to the embryo’s, extending within the umbilical cord. It is a selective barrier that prevents the two bloods from mixing together, but which allows nutrients to be transferred from the mother’s blood to the embryo’s blood, and waste substances to be transferred from the embryo’s blood to the mother’s blood.
Human Reproduction Defined
Human reproduction is the process by which humans create new human beings.
Modes of Reproduction and Development
Sexual Reproduction
Involves the fusion of two gametes: a female gamete (ovum) and a male gamete (sperm). They fuse to form the zygote, the first cell of the organism. The genetic material of an organism is a mixture of its parents’ genetic material.
Internal Fertilization
The fusion of gametes, called fertilization, occurs inside the female reproductive system.
Viviparous Development
The embryonic development of the new living organism is accomplished inside the mother’s reproductive system, which is fed through a structure called the placenta.
Stages of Sexual Development
Childhood
Characterized by the development of primary sex characteristics.
Adolescence
Marked by sexual maturation and significant physical and mental changes.
Adulthood
Reproductive maturity is typically reached.
Gametes and Their Production
Gametes, or sex cells, are the cells specialized in reproduction. They fuse to form the zygote, the first cell of the new living organism.
Gamete production is regulated by sex hormones and occurs in specialized sex organs called gonads.
Eggs (Ova)
Produced in the female gonads, the ovaries.
Sperm
Produced in the male gonads, the testes. These cells have a flagellum for movement.
Key Reproductive System Components
Gonads
Produce gametes and some sex hormones.
Genital Tracts
Transport the gametes.
Sex Organs
During sexual intercourse, these organs bring the egg and sperm together inside the female reproductive system.
Essential Reproductive Terminology
- Placenta: A disk-shaped organ that connects the developing being to the mother.
- Gonads: Organs that produce gametes and some sex hormones.
- Sex Organs: During sexual intercourse, these organs bring the egg and sperm together inside the female reproductive system.
- Zygote: The first cell of a new living organism, formed by the fusion of gametes.
- Sperm: Male gametes produced in the testes. These cells have a flagellum for movement.
- Semen: The male reproductive fluid, containing spermatozoa in suspension.
- Blastocyst: A ball of cells formed when the zygote divides through successive mitosis.
- Amniotic Sac: Commonly called the “bag of waters” or “membranes,” it is the sac in which the fetus develops in amniotes.
- Ejaculation: The discharge of semen (normally containing sperm) from the male reproductive tract.
- Endometrium: The mucous membrane lining the uterus, which thickens during the menstrual cycle in preparation for possible implantation of an embryo.
- Scrotum: A pouch of skin containing the testicles.
- Umbilical Cord: A structure that connects the circulatory system of the fetus with the placenta. It contains one vein that transports nutrient-rich blood from the placenta to the fetus, and two arteries that carry waste products in the blood from the fetus to the placenta.
- Menopause: The point when a woman stops having periods and is no longer able to get pregnant naturally.