The Reproductive
System
Chapter 34
Ms. Luaces
Honors Biology
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
34.3 Male Reproductive System
• Testosterone stimulates puberty, which
will result in the ability to reproduce
through the production of sperm
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
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
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
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
Sexually Transmitted Diseases (STD’s)
• 1 in 4 girls age 14-19 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!!
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
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)
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
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
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
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
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