Transcript 34.2 Reproductive Processes

34.2 Reproductive Processes
KEY CONCEPT
Human reproductive processes depend on cycles of
hormones.
34.2 Reproductive Processes
Eggs mature and are released according to hormonal
cycles.
• Follicle-stimulating hormone
(FSH) and lutenizing hormone
(LH) regulate egg production.
– meiosis produces eggs and
polar bodies
– each egg has 23
chromosomes
– meiosis is completed at
fertilization
potential
egg
Meiosis I
Completed
first polar
body
Meiosis II
Completed
only after
sperm
enters
second polar
body
ovum (egg)
34.2 Reproductive Processes
• FSH, LH, and estrogen stimulate the release of eggs.
– follicle ruptures at ovulation
– egg travels into fallopian tube
– ruptured follicle becomes corpus luteum
fallopian
tube
uterus
5 to 7 days to uterus
follicle
egg cell
egg released
ovary
uterine wall
corpus luteum
34.2 Reproductive Processes
Eggs mature and are released according to hormonal
cycles.
• The menstrual cycle has three phases.
– flow phase: endometrium sheds
– follicular phase: ovulation occurs
– luteal phase: corpus luteum forms
34.2 Reproductive Processes
• The menstrual cycle stops at menopause.
– cycle continues until a woman’s mid-40’s or 50’s
– decline in hormone levels make cycles irregular
– eventually, cycle stops altogether
34.2 Reproductive Processes
Sperm production in the testes is controlled by
hormones.
• Testosterone, FSH, and LH
stimulate sperm production.
potential
sperm
– one sex cell divides into
four sperm
– each sperm has 23
chromosomes
Meiosis I
Meiosis II
4 sperm cells
34.2 Reproductive Processes
• Sperm cells fully mature in the epididymis.
– head contains acrosome
– midpiece contains ATP acrosome
– tail allows mobility
nucleus with 23
chromosomes
head
mitochondria
midpiece
tail
34.2 Reproductive Processes
Fertilization occurs when a sperm cell joins an egg cell.
• Sperm penetrates an egg.
– membrane keeps out other sperm
– nucleus of sperm joins with egg
– zygote formed
34.2 Reproductive Processes
• Multiple zygotes can result from fertilization.
– identical twins from the same egg
– fraternal twins from two separate eggs
• Infertility makes reproduction difficult or impossible.
34.2 Reproductive Processes
Sexually transmitted diseases affect fertility and overall
health.
• Sexually transmitted diseases (STDs) are passed from one
person to another during sexual contact.
– bacterial STDs include chlamydia, syphilis, gonorrhea
– viral STDs include hepatitis B, genital herpes, human
papillomavirus, and HIV
HIV
34.2 Reproductive Processes
• Bacterial STDs can be treated, and in many cases, cured
with antibiotics
• Viral STDs can be treated,
but there is no cure for these
diseases.
• STDs attack reproductive
organs.
– can cause infertility
– untreated, some can be
fatal
• STDs can be avoided by
A parasite causes trichomoniasis, which can
abstinence or by using a
affect fertility.
condom.