ESQUEMA TEMA REPRODUCCIÓN HUMANA

HUMAN REPRODUCTION (RESUMEN)

Human reproduction is sexual, with internal fertilization and viviparous development of the zygote and embryo.

The male reproductive system is formed of:

The penis: a long cylindrical organ, covered in skin. Inside runs the urethra (a part of both the reproductive system and the excretory system).

The testicles: are the size of a nut. They produce sperm.

The scrotum: The sack of skin that covers the testicles.

The vas deferens: A tube that connects testicles to the urethra.

The glands: prostate and seminal vesicles. They produce liquids that mix with the sperm and form semen.

The female reproductive system is formed of:

The ovaries: Two oval organs, the size of a nut. They produce ovules.

The fallopian tubes: Two tubes that connect ovaries and uterus.

Uterus: An organ made of muscle. It shape and size is a pear.

The vagina: A tube that connect the female reproductive system to the exterior.

Vulva: Formed by folds of skin, called labia.

Fertilization is the union of a sperm and a mature ovule, which produces a zygote.

Pregnancy is the period when the zygote becomes the embryo, and the embryo develops inside the mother’s uterus.

Childbirth is when the baby leaves the mother’s body.

Fertilization happens in the fallopian tube. The zygote that forms becomes the embryo. This enters the uterus and becomes joined to the wall. In this way the pregnancy starts.

Pregnancy lasts about nine months and is divided in three phases of three months each one: first trimester, second trimester and third trimester.

When the baby is ready, the muscles of the wall of the uterus produce contractions. The amnion breaks and the baby comes out of the vagina.

The umbilical cord is cut. The remains of the cord leave a scar on the abdomen of the baby: the navel.

Sexual reproduction.

Sexual reproduction involves two different organisms; one produce female reproductive cells and the other, male reproductive cells.

Sexual reproduction has three phases:

-          The formation of reproductive cells.

-          Fertilization is the union of a male and female gamete.

-          The development of the zygote.

Asexual reproduction.

Asexual reproduction

Asexual reproduction involves only one organism. Descendents develop directly from the body of the progenitor. They are identical to the progenitor. 

         In unicellular organisms, the only cell divides into two new cells.

      In some simple invertebrates, the descendent forms slowly on the body of the progenitor, like a bud.

       Many plants can grow new plants from a root or a fragment of the stem. Other plants, like moss or ferns, produce cells called spores. Each spore grows and produces a descendent.