Basic Anatomy: Parts and Structure of the Reproductive System

The human reproductive system exhibits dramatic differences between males and females, reflecting the different roles each sex plays in reproduction. These differences extend beyond the obvious external anatomy to include internal structures, hormone production, and even basic physiology.

The female reproductive system is designed around the cyclical production and release of eggs, with structures that can support pregnancy and childbirth. The ovaries, two almond-shaped organs located in the pelvic cavity, serve as both the egg production centers and primary female hormone factories. Each ovary contains approximately 1-2 million immature eggs at birth, though this number steadily decreases throughout life, with only about 400,000 remaining at puberty and virtually none at menopause.

Each ovary consists of an outer cortex containing follicles (structures housing developing eggs) and an inner medulla containing blood vessels and nerves. Follicles exist in various stages of development, from primordial follicles containing immature eggs to mature Graafian follicles ready to release eggs during ovulation. The corpus luteum, formed from the follicle after egg release, produces hormones crucial for maintaining early pregnancy.

The fallopian tubes, also called oviducts, extend from near each ovary toward the uterus, creating a pathway for eggs to travel after ovulation. These tubes are about 10 centimeters long and lined with ciliated cells that create currents to help move eggs toward the uterus. The fimbria—finger-like projections at the end of each tube—sweep over the ovary surface to capture released eggs. Fertilization typically occurs within the fallopian tubes.

The uterus is a hollow, muscular organ about the size and shape of an inverted pear, designed to house and nourish a developing fetus. The uterine wall consists of three layers: the perimetrium (outer covering), myometrium (thick muscular layer), and endometrium (inner lining that thickens and sheds during menstrual cycles). The cervix, the lower portion of the uterus, extends into the vagina and serves as a gateway between the uterus and external environment.

The vagina is a muscular tube extending from the cervix to the external environment, serving multiple functions including menstrual flow passage, birth canal during delivery, and receptacle during sexual intercourse. The vaginal walls are highly elastic and contain numerous folds (rugae) that allow significant expansion when needed.

External female genitalia, collectively called the vulva, include the mons pubis, labia majora and minora, clitoris, and vaginal opening. The clitoris, containing thousands of nerve endings, is the primary organ of female sexual pleasure. The labia protect internal structures while the vaginal opening is partially covered by the hymen in many young females.

The male reproductive system is designed around continuous sperm production and delivery, with structures optimized for depositing sperm in the female reproductive tract. The testes, housed in the scrotum outside the body cavity, serve dual functions as sperm production centers and male hormone factories. This external location maintains testicular temperature about 2-3 degrees below body temperature, essential for normal sperm development.

Each testis contains hundreds of tightly coiled seminiferous tubules where sperm production (spermatogenesis) occurs. Between these tubules lie Leydig cells that produce testosterone, the primary male hormone. The process of creating mature sperm from stem cells takes approximately 74 days, with millions of sperm produced daily throughout adult life.

The epididymis, a coiled tube about 6 meters long when stretched, sits atop each testis and serves as a sperm maturation and storage center. Sperm spend 2-3 weeks in the epididymis, gaining the ability to swim and fertilize eggs. The vas deferens, muscular tubes about 45 centimeters long, transport mature sperm from the epididymis toward the urethra during ejaculation.

Accessory glands contribute fluids that combine with sperm to form semen. The seminal vesicles produce fructose-rich fluid that provides energy for sperm, while the prostate gland contributes alkaline fluid that helps neutralize acidic conditions in the female reproductive tract. The bulbourethral glands produce a small amount of pre-ejaculatory fluid that may contain some sperm.

The penis serves as the male organ for sexual intercourse and urination, containing three columns of erectile tissue that fill with blood during sexual arousal. The urethra runs through the penis, carrying both urine and semen (though not simultaneously) to the external environment.