Human Reproduction: Stages, Systems, and Cycles

Human Reproduction

Sexual Reproduction

• Egg + sperm = zygote
• Viviparous development inside the mother

Sexual Reproduction includes:

• Gamete production methods
• Fertilization: zygote
• Development of the zygote: embryo
• Childbirth
• Child Development: Adult

Stages of Sexual Maturity

Children: Birth-10 years

• Primary sex characteristics

Puberty: 10-11 years

• Develop secondary sexual characteristics
• First menstruation
• Production of sperm

Adolescence

• The body prepares for reproduction

20-23 years

• Adult: end of development

Female Reproductive System and Gametes

Female internal organs:

• Ovaries: matures the egg
• Fallopian tube: connects ovary and uterus
• Vagina: connects the uterus to the outside
• Clitoris: sensitive due to a high number of nerve endings
• Labia minora: lines the external genitalia
• Labia majora: surrounds the labia minora

Male Reproductive System and Gametes

• Testicles: produce sperm
• Epididymis: maturation of sperm
• Vas deferens: connects the epididymis to the urethra
• Urethra: connected to the exterior, expels sperm during ejaculation

Prostate: secretes prostatic fluid which protects the sperm from the acidity of the vagina.

Seminal vesicle: secretes seminal fluid for sperm motility.

Penis: cylindrical organ with an enlargement (glans) surrounded by foreskin.

Scrotum: surrounds the testicles.

Gametes: sperm

• Formed in the seminiferous tubules and mature in the epididymis

Ejaculation: sperm + seminal fluid + prostatic fluid

• Sperm can live in the vagina for 3-5 days

Female Reproductive Cycle

Estrogen: produced by the ovary

• Development and maintenance of follicle formation
• Induces the development of the Graafian follicle and egg maturation
• Cycle of 28 days, the maximum of estrogen (about day 14) causes ovulation

Progesterone: produced by the corpus luteum after ovulation

• Promotes growth and maturation of the endometrium
• If no egg fertilization occurs, the follicle dies and degenerates
• Endometrial progesterone level decreases, leading to menstruation

Gestation or pregnancy: from conception to delivery (approximately 40 weeks)

First trimester:

• Organ formation
• Fetus development
• Dizziness and nausea

Second trimester:

• Development of organs
• Growth and movement of the fetus

Third trimester:

• Maturation of organs
• Fetal growth