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The Reproductive System

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1 The Reproductive System
Chapter 34 Ms. Luaces Honors Biology

2 34.3 Sexual Development Sex hormones determine the pattern of development Females respond to estrogens, which stimulate breast development, widening of the hips, and egg production Males respond to testosterone, which stimulates growth of facial hair, increased muscular development, and deepening of the voice Most of these changes occur during puberty (ages 9-15) when the hypothalamus signals the pituitary to produce 2 hormones: FSH and LH

3 34.3 Male Reproductive System
Testosterone stimulates puberty, which will result in the ability to reproduce through the production of sperm

4 34.3 Male Reproductive System
Some important structures: Testes: site of sperm production Scrotum: holds the testes Seminiferous tubules: site of sperm development Epididymis: site of sperm maturation & storage Vas deferens: merges with urethra, opening to release sperm Semen: a mixture of sperm and lubricating seminal fluid

5 34.3 Female Reproductive System
FSH stimulates ovaries to produce egg cells and prepares the female’s body to nourish a developing embryo One ovary usually produces and releases 1 mature ovum every 28 days: menstruation

6 34.3 Female Reproductive System
Some important structures: Fallopian tubes: Where the egg is released into and awaits a sperm for fertilization Uterus: Where the growing embryo will develop Cervix: The opening to the uterus Vagina: Entrance into the female reproductive system; egg and uterine lining will be discarded through here

7 34.3 Female Reproductive System
Menstruation is split into 4 phases: Follicular phase: Pituitary secretes FSH & LH, stimulates estrogen release and causes the lining of the uterus to thicken (~12 days) Ovulation: releases an egg into the fallopian tube for fertilization (~1-2 days) Luteal Phase: Corpus luteum continues to release estrogen and progesterone, growing the uterine lining in prep for an embryo (~6 days) Menstruation: unfertilized egg, lining of uterus and blood are discarded (~5-7 days) Menopause: the permanent stop of the menstrual cycle at about age 40


9 Sexually Transmitted Diseases (STD’s)
1 in 4 girls age are infected with an STD, which can include: Bacterial STD’s: Chlamydia, Gonorrhea and Syphilis Viral STD’s: Hepatitis B, Genital Herpes, Genital Warts (HPV) & AIDS How do you prevent an STD? Abstinence is the only 100% effective method. Condoms cannot completely guard from STD’s!!

10 34.4 Fertilization & Development
The fusion of a sperm and egg cell is called fertilization Usually occurs in the fallopian tube Once fertilization occurs, the fertilized egg is called a zygote Two eggs can be fertilized at the same time by different sperm – fraternal twins One egg can be fertilized and split into two separate zygotes – identical twins

11 34.4 Fertilization & Development
About 6-7 days after fertilization, the blastocyst attaches to the wall of the uterus – known as implantation Now it undergoes differentiation (gastrulation) – various types of tissue of the body are formed, including ectoderm, endoderm, and mesoderm. Eventually, neurulation takes places also (making of the nervous system)

12 34.4 Fertilization & Development
The placenta will protect and nourish the embryo, allowing exchange of oxygen and nutrients with the mother Mother and baby blood do not mix

13 34.4 Fertilization & Development
After 8 weeks, the embryo is now called a fetus. Most major organs fully formed During months 4-6, the fetal heart becomes large enough to hear through a stethoscope, the bone develops, and the mother may be able to feel the baby

14 34.4 Fertilization & Development
During months 7-9, the fetus matures, gains weight, and completes the development of lungs and the nervous system Babies born before 8 months are premature and may have breathing problems

15 34.4 Fertilization & Development
Childbirth is signaled by the release of the hormone oxytocin, which stimulates contractions of the uterus and starts labor Once the cervix is open, the baby is able to pass through the birth canal A babies first cough or cry helps to rid the lungs of fluid. The umbilical cord will be clamped and cut

16 34.4 Fertilization & Development
The placenta and amniotic sac will also be dispelled after birth Prolactin hormone will be released and stimulate the production of milk AIDS, Rubella, drugs, alcohol and smoking can harm the babies development

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