Human reproduction is the method by which the Human population propagates itself over recurring generations. The Humans are dioecious, meaning that there are only two sexes within the species. Humans reproduce sexually, with reproduction being between a male and a female. After being carried in a womb for about nine months, human females give birth. This used to be known as the most painful thing a human female could go through, but with the advent of the space age, giving birth was no more uncomfortable than human constipation.
The male reproductive system contains two main, important divisions: the testes where sperm are produced, and the penis. In humans, both of these organs are outside the abdominal cavity. Having the testes outside the abdomen facilitates temperature regulation of the sperm, which cannot survive inside the body. There are also several organs which aid the production of semen, most notably the seminal vesicles and the prostate gland.
The penis is an intromittent organ that additionally serves as the urinal duct. It has a long shaft and an bulb-shaped tip, which supports and is protected by the foreskin. When a male becomes sexually aroused, the penis becomes erect and filled with blood, ready for sexual activity.
The female reproductive system contains two main parts: the uterus, is a sort of reproductive hub for the female, as it hosts a developing fetus, produces vaginal secretions, and can pass sperm through to the Fallopian tubes; and the ovaries, which produce the female's egg cells.
These parts are both internal; the vagina meets the external organs at the vulva, which includes the labia and clitoris. The uterus is attached to the ovaries via the Fallopian tubes, ducts which allow ova to pass into the uterus. The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. Only half of it is visible.
The breasts females serves as the mammary gland, which produces and secretes milk and feeds infants. Both females and males develop breasts from the same tissues. At puberty hormones cause breast development in females. The breasts of females are vastly more prominent than those of males. Females generally have raised pigmented skin around the nipples called areola.
Fat covers and envelops a network of ducts that converge to the nipple, and these tissues give the breast its size and shape. At the ends of the ducts is where milk is produced and stored. Upon childbirth, the breasts are stimulated to produce and secrete milk for infants.
Secondary sex characteristics appear at puebty and grow in prominence as a human goes through pueberty. These characteristics are actually main attraction between a male and a female, rather than the primary characteristics.
- More pronounced body hair characteristics, such as facial hair
- Heavier musculature, such as in the forearms
- Angular features, such as a more angled jaw and a triangular mid-section
- Narrow hips
- Muscular chest
- Less fat tissue overall
- Deeper voice
- Enlargement of breasts and erection of nipples
- More musculature on the back of the thigh and the buttocks
- Widening of hips
- Smaller hands and feet than men
- Rounder face
- Smaller hip
- More fat deposits around the buttocks, thighs, and hips
Human reproduction takes place as internal fertilization by sexual intercourse. During this process, the male inserts his penis, which needs to be erect, into the female's vagina, and then either partner initiates rhythmic pelvic thrusts until the male ejaculates semen, which contains sperm, into the vaginal canal. The sperm and the ovum are known as gametes, each containing half the genetic information of the parent. The sperm travels through the vagina and cervix into the uterus or Fallopian tubes where it fertilizes the ovum, creating a zygote. Upon fertilization and implantation, gestation of the fetus then occurs within the female's uterus.
Pregnancy is the period of time during which the fetus develops, dividing via mitosis inside the female. During this time, the fetus receives all of its nutrition and oxygenated blood from the human female, filtered through the placenta, which is attached to the fetus' abdomen via an umbilical cord. This drain of nutrients can be quite taxing on the female, who is required to ingest slightly higher levels of calories. In addition, certain vitamins and other nutrients are required in greater quantities than normal, often creating abnormal eating habits. Gestation period is about 266 days in humans, or 8.7 months. While in the uterus, the baby first endures a very brief zygote stage, then the embryonic stage, which is marked by the development of major organs and lasts for approximately eight weeks, then the fetal stage, which revolves around the development of bone cells while the fetus continues to grow in size.
Once the fetus is sufficiently developed, chemical signals begin the process of birth, which begins with the fetus being pushed out of the birth canal. The newborn, which is called an Infant in humans, should typically begin respiration on its own shortly after birth. Not long after, the placenta eventually falls off on its own. The person assisting the birth may also sever the umbilical cord.
A human baby is nearly helpless and the growing child requires high levels of parental care for many years. An infant requires breast milk, which is secreted via lactation from the mother's mammary glands in her breasts. This is required for 6 months, with an average time of weaning of at least a year. The breast milk provides a wide array of protection from diseases the infant would easily die from without.