Human reproduction

Puberty

when a person becomes sexually mature and is capable of reproduction

Male gonads and gametes

Testes (gonads) and sperm (gamete)

Testes

produces sperm and acts as an endocrine gland secreting testosterone

Testosterone

male sex hormone, responsible for secondary sex characteristics (body hair, muscle development, deeper voice etc)

vas deferens

the tube where sperm leaves the epididymis

urethra

where the 2 vas deferens meet, releases urine and semen

semen

mixture of fluids and sperm

ejaculation

where men release semen out of their body through the urethra

How does reproduction work on the male end?

Immature sperm are produced in the seminiferous tubules (small, coiled tubes in each testis). Once produced, sperm move to the epididymis, where they are stored. Sperm leave the epididymis through the vas deferens, the two vas deferens meet at the urthea. Glands secrete fluids that mix with sperm to create semen. Semen passes through the urethra by the process of ejaculation, urine is blocked shortltly before and after ejaculation.

Female gonads and gametes

Ovaries (gonads) and eggs (gametes)

Ovaries

produce eggs and secrets female hormones including estrogen

Estrogen

responsible for secondary sex characteristics, breast development, broadened pelvis, etc

Oviduct or Fallopian tube

tube with funnel like opening, carries egg into uterus

uterus

thick walled muscular pear shaped organ

cervix

connects the uterus to the vagina

vagina

tunnel that leads from the outside world to the cervix

Follicle

2 ovaries contain about 200,000 tiny egg sacs called follicles, each follicle contains 1 immature egg cell

How does reproduction work on the female end?

When one follicle ruptures, the egg is released at the surface of the ovary (ovulation). Ciliated cells draw the egg into the oviduct. It passes through the oviduct into the uterus. Once the egg is in the oviduct, it can be fertilized by a sperm cell.

Menstrual cycle

mature egg is developed and released from one of the ovaries approximately every 28 days. The walls of the uterus have been building up preparing to accept the egg. If the egg isn't fertilized, the wall of the uterus breaks down, material from the wall and the unfertilized egg get eliminated from the body. The cycle begins again with the maturing of another egg.

What are the stages of the menstrual cycle?

Follicle stage, ovulation, corpus luteum stage and menstruation

Follicle stage

FSH (follicle stimulating hormone) is secreted by the pituitary gland. FSH causes several follicles to begin to develop. Usually only one matures. As the follicle develops it secrets estrogen. Estrogen cause the uterine lining to become thicker. usually lasts about 10 days

Ovulation

high levels of estrogen in the blood causes the pituitary gland to decrease the secretion of FSH and begin the secretion of LH (luteinizing hormone). When LH levels reach a certain point ovulation occurs. Follicle ruptures. Usually takes place in the middle of the menstrual cycle.

Corpus Luteum Stage

After ovulation LH causes the ruptured follicle to fill with cells forming a yellow body called the corpus luteum. Corpus luteum begins to excrete the hormone progesterone, which continues the growth of the uterine lining. lasts about 14 days.

Menstruation

no fertilization occurs, LH levels drop, corpus luteum breaks down, progesterone levels drop, thick lining of uterus breaks down, extra lining, unfertilized egg and small amounts of blood pass out of the body through vagina, new eggs develops and cycle starts all over again

menopause

when menstrual cycle naturally stops during middle age

Sex

hundreds of millions of sperm are ejaculated into the vagina. They travel through the cervix, across the uterus and into the oviducts. IF an egg is passing through the oviducts, fertilization might occur.

Zygote

when sperm and egg meet and fertilize the egg

implantation

zygote undergoes cleavage developing into a blastula, while at the same time it is moving down the oviducts towards the uterus. 5-10 days after fertilization, zygote enters the uterus. Outer cells of the zygote secrets enzymes that eat away the lining of the uterus. Zygote attaches to that spot. Three germ layers develop. The developing human is called an embryo. After 8 weeks its called a fetus.

Placenta

exchanges oxygen and nutrients to the fetus and waste to the mom, connected by umbilical cord

Labor

when the baby is ready to be born, the uterus begins slow rhythmic contractions and cervix begins to enlarge

fraternal twins

two eggs become fertilized, embedded separately, and develop separately

identical twins

a fertilized egg divides into two embryos at an early stage of development, each embryo then forms separately, genetically identical