1. Ch. 27: Reproduction and Embryonic Development

2. Asexual reproduction Budding Fission
Fragmentation, accompanied by regeneration
Development of an unfertilized egg

3. Sexual reproduction
The fission of two haploid gametes from two parents to form a diploid zygote

4. Sexual and asexual reproduction are both common among animals
Rotifers can reproduce both asexually and sexually
Hermaphroditism
A single individual has both male and female reproductive systems

5. Asexual Reproduction Advantages of asexual reproduction
A single individual reproduces
Many offspring are produced rapidly
Disadvantage of asexual reproduction
Little or no genetic variation

6. Sexual Reproduction Advantages of sexual reproduction
Increases genetic variation
Enhances reproductive success in changing environments
Disadvantage of sexual reproduction
Locating a mate

7. Reproductive anatomy of the human female
main functions of the female reproductive system
1. to produce eggs, the (female sex cells),
2.to receive sperm,
3. to provide an environment in which a fertilized egg can develop.
Oviduct
Ovary
Uterus
Bladder (excretory system
Urethra (excretory system
Vagina
Vaginal opening

8. Reproductive anatomy of the human female
Ovaries
Contain follicles that nurture eggs (ova)
Produce sex hormones
Functional from puberty to menopause
Oviducts (Fallopian Tubes)
Convey eggs to the uterus
Muscular contractions &cilia draw ovum (egg) into oviduct
Fertilization occurs
Ovaries
Oviduct
Follicles
Corpus luteum
Uterus
Endometrium (lining of uterus
Cervix (“neck” of uterus)
Vagina

9. Reproductive anatomy of the human female
Uterus (womb)
Development of fertilized egg
Opens into the vagina
Vagina
Receives penis during intercourse
Forms the birth canal

10. Reproductive anatomy of the human male
main functions
1. the production of sperm—the male sex cells
2. their delivery to the female.
Seminal vesicle (behind bladder)
Bladder (excretory system)
Prostate gland
Vas deferens
Urethra
Scrotum
Epididymis
penis
Testis

11. Reproductive anatomy of the human male
Semen
Sperm, which are expelled through the ducts during ejaculation
Glandular secretions that carry, nourish, and protect the sperm
Testes
Produce sperm
Located outside abdominal cavity within the scrotum (saclike pouch~ 1-3°C below normal body temperature- sperm can only form at this lower temp.)

12. How sperm leave the testes
1. Seminiferous tubules: carries/stores sperm in testes
2.Epididymis: a series of coiled ducts for maturation & temporary storage organ for sperm
3. Vas deferens: tube which carries sperm past lubricating glands
4. ( a.)Seminal vesicles: secrete fluid that protects & nourishes sperm
(b.) Prostrate gland: produces an alkaline fluid that neutralizes urine in the urethra
(c.) Bulbourethral glands: secrete fluid that may help lubricate the urethra
5. Urethra: tube in the penis that transports sperm out of the male’s body, also transports urine from the urinary bladder.
6. Penis: copulatory organ, releases semen
7. Ejaculation: the release of semen

13. Reproductive anatomy of the human male

14. Gametogenesis: The formation of sperm and ova requires meiosis
Spermatogenesis
Produces sperm in the male
Oogenesis
Produces ova in the female

15. Spermatogenesis Increases genetic variation
Primary spermatocytes (diploid) are produced throughout a male’s reproductive years
Diploid cells undergo meiosis to form four haploid sperm

16. Spermatogenesis
sperm
seminiferous tubule
spermatocytes

17. Oogenesis Most of the process occurs within the ovaries
Lifetime supply of primary oocytes is present at birth
One primary oocyte matures each month to form a secondary oocyte
If the secondary oocyte is fertilized, it completes meiosis and becomes a haploid ovum

18. Oogenesis OVULATION Diploid cell PRIMARY OOCYTE Start: within follicle
Degenerating corpus luteum
PRIMARY OOCYTE
CORPUS LUTEUM
Growing follicles
SECONDARY OOCYTE,
Mature follicle
SECONDARY OOCYTE
Ruptured follicle
OVULATION
OVUM

19. Puberty
Puberty: when secondary characteristics develop and the potential for sexual reproduction is reached(sperm production or ovulation)
Changes are controlled by hormones
secondary sex characteristics:
Males: hormone~ testosterone, characteristics~ body hair, muscle development, deep voice
Females: Hormone~ estrogen. Characteristics~ breasts, broadened pelvis, distribution of body fat

20. Reproductive hormones
Testosterone
from testes
sperm production & secondary sexual characteristics
Estrogen
from ovaries
egg production, preparing uterus for fertilized egg & secondary sexual characteristics

21. Hormonal control of the testes
Stimuli from other areas in the brain
Androgens (testosterone most important) stimulate sperm production
They also maintain homeostasis by a negative feedback mechanism that inhibits the secretion of FSH (follicle-stimulating hormone) and LH (luteinizing hormone)
Hypothalamus
Releasing hormone
Anterior pituitary
Negative feedback
FSH LH
Androgen production
Testis
Sperm production

22. The Reproductive Cycle of the Human Female I
A cyclic pattern of hormone secretion and reproductive events.
Humans and many other primates have menstrual cycles.
If pregnancy does not occur the endometrium is shed through the cervix and vagina: menstruation

23. The Reproductive Cycle of the Human Female. II
Menstrual cycle: changes that occur in the uterus.
Day 1: the first day of menstruation.
Menstrual flow phase.
Menstrual bleeding.
Usually lasts for a few days
Proliferative phase.
Regeneration and thickening of the endometrium.
About 1 – 2 weeks in duration.
Secretory phase.
Continued endometrial thickening
about 2 weeks

24. The Reproductive Cycle of the Human Female. III
Ovarian cycle.
Follicular phase.
Several ovarian follicles begin to grow..
Usually only one follicle continues to develop, the others disintegrate.
The follicular phase ends with ovulation.
Follicle and adjacent wall of the ovary rupture
Secondary oocyte is released.
Luteal phase.
Follicular tissue remaining in the ovary develops into the corpus luteum.
Secretes estrogens and progesterone.

25. Egg maturation in ovary
releases progesterone
maintains uterus lining
produces estrogen

26. Hormones synchronize cyclical changes in the ovary and uterus

27. Menstrual cycle Controlled by interaction of 4 hormones FSH & LH
estrogen
progesterone
FSH
ovulation = egg release
egg development
corpus luteum
estrogen
progesterone
lining of uterus
days 7 14 21 28

28. Hormonal coordination of the menstrual and ovarian cycles .
FSH (follicle stimulating hormone) produced by pituitary stimulates development of follicle
LH (luteinizing hormone) stimulates the development of the corpus luteum, stimulates ovulation
Estrogen: secreted by ovaries, stimulates development of uterine lining
Progesterone: secreted by corpus luteum, maintains uterine lining

29. Female reproductive cycle
Feedback
egg matures &
is released (ovulation)
builds up uterus lining
estrogen
ovary
corpus luteum
progesterone
FSH & LH
fertilized egg (zygote)
maintains uterus lining
HCG
yes
pituitary gland
corpus luteum
pregnancy
GnRH no
progesterone
corpus luteum breaks down
progesterone drops
menstruation
maintains uterus lining
hypothalamus

30. Fertilization results in a zygote and triggers embryonic development
Fertilization is the union of a sperm and an egg to form a diploid zygote
(PATH) Millions of sperm ->vagina -> cervix -> uterus -> oviduct (site of fertilization)
sperm + egg -> zygote
23(n) + 23(n) -> 46(2n)

31. Fertilization
Only one of these sperm will penetrate this human egg cell to initiate fertilization
The shape of a human sperm cell is adapted to its function

32. Fertilization

33. Implantation
Implantation: fertilized egg implants in thickened uterine lining