Genitalia are the reproductive and sexual organs of the body. The term covers both the external parts you can see and the internal organs involved in reproduction, sexual pleasure, and urination. Everyone is born with genitalia, though the specific anatomy varies. Most people develop structures that are typically male or typically female, while some are born with variations that don’t fit neatly into either category.
How Genitalia Form Before Birth
For the first several weeks of development in the womb, all embryos have identical genital tissue. No visible difference exists until around the sixth week of pregnancy, and the external genitalia remain undifferentiated until roughly the ninth week. At that point, hormonal signals determine which path development takes. In embryos with a Y chromosome, the body produces androgens (particularly testosterone and a more potent form called DHT) along with another hormone that redirects internal structures toward male development. In the absence of these hormones, development follows the female pathway.
Because all genitalia start from the same tissue, male and female structures share direct counterparts. The glans of the penis and the glans of the clitoris develop from the same tissue. Penile foreskin and the clitoral hood are counterparts. The skin of the penile shaft corresponds to the inner labia, and scrotal skin corresponds to the outer labia. These parallel structures explain many similarities in sensitivity and function between male and female genitalia.
Female Genitalia
Female genitalia include both external and internal structures. The external parts are collectively called the vulva, which protects the internal organs from infection and provides the entry point for sperm.
The vulva includes the labia majora (outer lips), which enclose and protect the other structures. Inside those sit the labia minora (inner lips), which vary widely in size and shape from person to person and surround the openings to the vagina and urethra. Where the inner labia meet at the top sits the clitoris, a small, highly sensitive structure covered by a fold of skin. The clitoris is densely packed with nerve fibers. Research comparing nerve density found that although the clitoris receives roughly one-third the total number of nerve fibers that the penis does, its much smaller surface area gives it about six times the nerve density, making it extremely responsive to touch.
The vaginal opening allows menstrual blood to leave the body and babies to pass through during birth. A thin piece of tissue called the hymen partially surrounds or covers part of this opening. Nearby, the urethral opening is a separate, smaller hole used for urination.
Internally, the vagina is a muscular canal lined with mucous membranes that keep it moist. It connects to the uterus, a hollow, pear-shaped organ where a fetus develops during pregnancy. The lower, narrow part of the uterus is called the cervix, which opens into the vagina. On either side of the uterus sit the ovaries, small oval glands that produce eggs and hormones like estrogen and progesterone.
Male Genitalia
Male genitalia are primarily responsible for producing, maintaining, and transporting sperm. The main external structures are the penis and scrotum.
The penis contains three chambers of sponge-like tissue filled with thousands of tiny spaces. During arousal, these spaces fill with blood, making the penis rigid. When erect, the internal tissue compresses the urinary channel so that only semen exits during ejaculation. The tip of the penis (the glans) is covered by multilayered, highly innervated skin, making it the most sensitive region.
Behind the penis hangs the scrotum, a loose pouch of skin that holds the testicles. The scrotum acts as a temperature regulator, contracting or relaxing to keep the testicles slightly below core body temperature, between about 97 and 99 degrees Fahrenheit. This cooler environment is necessary for healthy sperm production. The testicles themselves are the primary reproductive glands, producing both sperm and testosterone.
Internally, several structures support reproduction. The prostate gland, roughly the size of a walnut, sits below the bladder and adds nutrient-rich fluid to semen. Two small, pea-sized glands near the base of the urethra produce a slippery fluid that lubricates the urinary channel and neutralizes any residual acidity from urine before ejaculation.
Changes During Puberty
Genitalia don’t reach their adult form until puberty, which typically begins between ages 8 and 13 in girls and 9 and 14 in boys. Doctors track these changes using a five-stage scale. In males, the first sign of puberty is testicular growth. The testicles gradually increase in size across all five stages, eventually reaching their adult volume. The penis lengthens and thickens, pubic hair appears and coarsens, and the scrotum darkens in color. In females, breast development is typically the first visible sign, followed by pubic hair growth, widening of the hips, and the start of menstruation. The labia and clitoris also grow and change shape during this time.
Natural Variations in Genital Development
Not everyone is born with genitalia that are clearly male or female. Intersex is a broad term for natural variations in sex characteristics, which can involve differences in chromosomes, hormones, or anatomy. Most people with intersex traits are born with genitalia that appear typically male or female and are assigned a sex at birth accordingly. In some cases, differences aren’t noticed until puberty or even adulthood. One of the more commonly identified variations is complete androgen insensitivity syndrome, where a person has XY chromosomes but their body doesn’t respond to androgens, resulting in external anatomy that appears female.
Estimates of how common intersex traits are vary depending on how broadly the term is defined. Some surveys have found that roughly 1 to 2 percent of the population may have some form of intersex variation, though figures differ across studies and definitions.
Routine Health Screenings
Keeping genitalia healthy involves age-appropriate screenings. For people with a cervix, cervical cancer screening with a Pap test starts at age 21 and is repeated every three years through age 29. From ages 30 to 65, screening can shift to every five years if an HPV test is included. For people with testicles, awareness of changes in size, shape, or lumps is important starting in the teen years.
Sexually transmitted infection screening applies regardless of anatomy. Chlamydia and gonorrhea screening is recommended for sexually active people up to age 24, and for older adults with risk factors. A one-time HIV test is recommended for everyone between ages 15 and 65, and a one-time hepatitis C test for adults between 18 and 79.