1. General Biology 102 SUNY Orange at S. S. Seward Institute
Reproduction
General Biology 102
SUNY Orange at
S. S. Seward Institute

4. Both asexual and sexual reproduction occur in the animal kingdom
Asexual reproduction is creation of offspring whose genes all come from one parent
Sexual reproduction is creation of offspring by fusion of male gametes (sperm) and female gametes (eggs) to form zygotes

5. Mechanisms of Asexual Reproduction
Many invertebrates reproduce asexually by fission, separation of a parent into two or more individuals of about the same size

7. Budding - two new individuals arise from outgrowths of existing ones
Fragmentation - breaking of the body into pieces, some or all of which develop into adults
must be accompanied by regeneration, regrowth of lost body parts

8. Reproductive Cycles and Patterns
Most animals exhibit reproductive cycles related to changing seasons
Reproductive cycles are controlled by hormones and environmental cues
Animals may reproduce asexually or sexually, or they may alternate these methods

9. Parthenogenesis is a process in which an egg develops without being fertilized
Several genera of fishes, amphibians, and lizards reproduce only by a complex form of parthenogenesis

10. Ovary
size
Ovulation
Ovulation
Estrogen
Progesterone
Hormone
level
Time
Behavior
Female-
like
Male-
like
Female-
like
Male-
like

11. Sexual reproduction is a special problem for organisms that seldom encounter a mate
One solution is hermaphroditism - each individual has male and female reproductive systems
In sequential hermaphroditism, an individual reverses its sex during its lifetime

13. Fertilization depends on mechanisms that help sperm meet eggs of the same species
The mechanisms of fertilization, the union of egg and sperm, play an important part in sexual reproduction
In external fertilization, eggs shed by the female are fertilized by sperm in the external environment

14. Eggs

15. Internal fertilization - sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract
- requires critical timing, often mediated by environmental cues, pheromones, and/or courtship behavior
- requires behavioral interactions and compatible copulatory organs

16. Ensuring the Survival of Offspring
All species produce more offspring than the environment can handle, but the proportion that survives is quite small
Embryos of many terrestrial animals develop in eggs that can withstand harsh environments
Many animals retain the embryo, which develops inside the female
In many animals, parental care helps ensure survival of offspring

18. Gamete Production and Delivery
Must have systems that produce gametes
The least complex systems do not contain distinct gonads
More complex systems contain many sets of accessory tubes and glands that carry, nourish, and protect gametes and developing embryos
Many animals with relatively simple body plans have highly complex reproductive systems

19. Genital
pore
(Digestive tract)
Male organs:
Female organs:
Uterus
Seminal
vesicle
Yolk gland
Yolk duct
Sperm duct
(vas deferens)
Oviduct
Ovary
Vas efferens
Seminal
receptacle
Testis
(Excretory pore)

20. Most insects have separate sexes with complex reproductive systems

21. Accessory
gland
Ovary
Ejaculatory
duct
Testis
Oviduct
Spermatheca
Vas
deferens
Penis
Vagina
Seminal
vesicle
Accessory
gland
Male honeybee (drone)
Female honeybee (queen)

22. Reproductive organs produce and transport gametes: humans

23. Female Reproductive Anatomy
The female external reproductive structures include the clitoris and two sets of labia
The internal organs are a pair of gonads and a system of ducts and chambers that carry gametes and house the embryo and fetus

24. Female Reproductive Anatomy
Labia majora pubic bone
Labia minora ovary
Clitoris oviduct
Uterus cervix
Vagina endometrium
Urinary bladder follicle
Rectum corpus luteum

25. Oviduct
Ovary
Uterus
(Urinary bladder)
(Rectum)
(Pubic bone)
Cervix
Urethra
Vagina
Shaft
Glans
Clitoris
Bartholin’s gland
Prepuce
Labia minora
Vaginal opening
Labia majora

26. Oviduct
Ovaries
Follicles
Corpus luteum
Uterine wall
Uterus
Endometrium
Cervix
Vagina

27. Ovaries The female gonads, the ovaries, lie in the abdominal cavity
Each ovary
Has tough protective capsule
contains many follicles
Follicle consists of one egg surrounded by one or more layers of follicle cells

28. Ovulation expels an egg cell from the follicle
Remaining follicular tissue grows within the ovary, forming a mass called the corpus luteum (body, yellow)
The corpus luteum secretes hormones, depending on whether pregnancy occurs

29. Cilia in the tube convey the egg to the uterus
Oviducts and Uterus
Egg cell is released into the abdominal cavity near the opening of the oviduct, or fallopian tube
Cilia in the tube convey the egg to the uterus

30. opens to the outside at the vulva,
Vagina and Vulva
Vagina - thin-walled chamber that is the repository for sperm during copulation and serves as the birth canal
opens to the outside at the vulva,

31. Within the glands, small sacs of epithelial tissue secrete milk
Mammary Glands
Mammary glands are not part of the reproductive system but are important to mammalian reproduction
Within the glands, small sacs of epithelial tissue secrete milk

32. Male Reproductive Anatomy
Urinary bladder vas deferens
Urethra prostate gland
Epididymis testis
Erectile tissue scrotum
Seminal vesicle glans penis
Blulbourethral gland pubic bone

33. Male Reproductive Anatomy
In most mammals, the male’s external reproductive organs are the scrotum and penis
Internal organs are the gonads, which produce sperm and hormones, and accessory glands

34. (Urinary
bladder)
Seminal vesicle
(Rectum)
(Public bone)
Vas deferens
Erectile
tissue of
penis
Ejaculatory duct
Prostate gland
Urethra
Bulbourethral gland
Vas deferens
Glans penis
Epididymis
Testis
Prepuce
Scrotum

35. Seminal
vesicle
(behind
bladder)
(Urinary
bladder)
Prostate gland
Bulbourethral
gland
Urethra
Erectile tissue
of penis
Scrotum
Vas deferens
Epididymis
Glans penis
Testis

36. The male gonads, or testes, consist of highly coiled tubes surrounded by connective tissue
Sperm form in these seminiferous tubules
Production of normal sperm cannot occur at the body temperatures of most mammals
The testes of many mammals are held outside the abdominal cavity in the scrotum, where the temperature is lower than in the abdominal cavity

37. Ducts
From the seminiferous tubules of a testis, sperm pass into the coiled tubules of the epididymis
During ejaculation, sperm are propelled through the muscular vas deferens and the ejaculatory duct, and then exit the penis through the urethra

38. Glands
Three sets of accessory glands add secretions to the semen, the fluid that is ejaculated
The two seminal vesicles contribute about 60% of the total volume of semen

39. The prostate gland secretes its products directly into the urethra through several small ducts
The bulbourethral gland secretes a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra

40. Penis
The human penis is composed of three cylinders of spongy erectile tissue
During sexual arousal, the erectile tissue fills with blood from the arteries, causing an erection

41. Two reactions predominate in both sexes:
Human Sexual Response
Two reactions predominate in both sexes:
Vasocongestion, the filling of tissue with blood
Myotonia, increased muscle tension
The sexual response cycle has four phases: excitement, plateau, orgasm, and resolution

42. In humans and other mammals, a complex interplay of hormones regulates gametogenesis
The process of gametogenesis is based on meiosis, but differs in females and males
Oogenesis is development of mature ova
Spermatogenesis is production of mature sperm

43. Completion of meiosis I and onset of meiosis II
Ovary
Primary germ cell
in embryo
Differentiation
Oogonium
in ovary
Oogonium
Mitotic
division
Primary
oocyte
within
follicle
Primary
oocyte
Completion of meiosis I
and onset of meiosis II
Growing
follicle
Secondary
oocyte
First polar body
Ovulation
Entry of sperm
triggers
completion
of meiosis II
Mature follicle
Ruptured
follicle
Second polar body
Ovum
Ovulated
secondary oocyte
Corpus luteum
Degen-
erating corpus luteum

44. Epididymis
Seminiferous tubule
Testis
Cross section
of seminiferous
tubule
Spermatogonium
Mitotic division, producing
large numbers of spermatogonia
Sertoli cell
nucleus
Differentiation and onset of meiosis I
Primary spermatocyte
(in prophase of meiosis I)
Meiosis I completed
Secondary spermatocyte
Meiosis II
Lumen of
Seminiferous tubule
Early
spermatids
Spermatids
(at two stages of
differentiation)
Differentiation
Sperm cells
Neck
Head
Midpiece
Tail
Plasma membrane
Acrosome
Nucleus
Mitochondria

45. Oogenesis differs from spermatogenesis – 3 major ways:
During meiotic divisions, cytokinesis is unequal, with almost all of the cytoplasm in one daughter cell, the secondary oocyte
Unlike sperm, eggs are not produced continuously throughout life
Oogenesis has long “resting” periods, whereas sperm are produced in uninterrupted sequence

46. Reproduction
Where do babies really come from?

47. The Reproductive Cycles of Females
In females, the secretion of hormones and the reproductive events they regulate are cyclic

48. Menstrual Versus Estrous Cycles
Two different types of cycles occur in females
Humans and other primates have menstrual cycles; other mammals have estrous cycles
In both cases, ovulation occurs after the endometrium has started to thicken in preparation for implantation

49. In menstrual cycles:
The endometrium is shed from the uterus in a bleeding called menstruation
Sexual receptivity is not limited to a timeframe
In estrous cycles:
The endometrium is reabsorbed by the uterus
Sexual receptivity is limited to a “heat” period

50. The Human Female Reproductive Cycle: A Closer Look
The female reproductive cycle is one integrated cycle involving two organs: the uterus and ovaries
Secretion of GnRH from the hypothalamus and of FSH and LH from the anterior pituitary orchestrates the female reproductive cycle
Five kinds of hormones participate in an elaborate scheme involving positive and negative feedback

51. Hypothalamus Anterior pituitary
Control by hypothalamus
Inhibited by combination of
estrogen and progesterone
Hypothalamus
Stimulated by high levels
of estrogen
GnRH
Anterior pituitary
Inhibited by low levels of
estrogen
FSH LH
Pituitary gonadotropins
in blood LH
FSH
FSH and LH stimulate
follicle to grow
LH surge triggers
ovulation
Ovarian cycle
Corpus
luteum
Degenerating
corpus luteum
Growing follicle
Mature
follicle
Follicular phase
Ovulation
Luteal phase
Estrogen secreted
by growing follicle in
increasing amounts
Progesterone and
estrogen secreted
by corpus luteum
Ovarian hormones
in blood
Peak causes
LH surge
Estrogen
Progesterone
Estrogen level
very low
Progesterone and estro-
gen promote thickening
of endometrium
Uterine (menstrual) cycle
Endometrium
Menstrual flow phase
Proliferative phase
Secretory phase
Days 5 10 14 15 20 25 28

52. The Ovarian Cycle
In the ovarian cycle, hormones stimulate follicle growth, which results in ovulation
Following ovulation, the follicular tissue left behind transforms into the corpus luteum

53. The Uterine (Menstrual) Cycle
Cycle after cycle, the maturation and release of egg cells from the ovary are integrated with changes in the uterus
If an embryo has not implanted in the endometrium by the end of the secretory phase, a new menstrual flow commences

54. Menopause
After about 450 cycles, human females undergo menopause, the cessation of ovulation and menstruation

55. Hormonal Control of the Male Reproductive System
Testosterone and other androgens are directly responsible for the primary and secondary sex characteristics of the male
Androgen secretion and sperm production are controlled by hypothalamic and pituitary hormones

56. Stimuli from other areas in the brain Leydig cells make testosterone
Hypothalamus
GnRH
Anterior
pituitary
Negative
feedback
FSH LH
Leydig cells
make
testosterone
Primary and
secondary sex
characteristics
Sertoli cells
Spermatogenesis
Testis

57. In humans and other placental mammals, an embryo grows into a newborn in the mother’s uterus
Pregnancy, or gestation, is the condition of carrying one or more embryos in the uterus
Duration of pregnancy in other species correlates with body size and maturity of the young at birth

58. Conception, Embryonic Development, and Birth
Conception, fertilization of an egg by a sperm, occurs in the oviduct
After fertilization, the zygote undergoes cleavage and develops into a blastocyst before implantation in the endometrium

59. Cleavage starts
Cleavage continues
Ovary
Fertilization occurs
The blastocyst implants
Uterus
Ovulation
Endometrium
From ovulation to implantation

60. Endo-
metrium
Inner cell mass
Cavity
Trophoblast
Blastocyst
Implantation of blastocyst

61. First Trimester
Human gestation can be divided into three trimesters of about three months each
The first trimester is the time of most radical change for both the mother and the embryo

62. During its first 2 to 4 weeks, the embryo obtains nutrients directly from the endometrium
Meanwhile, the outer layer of the blastocyst mingles with the endometrium and eventually forms the placenta
Blood from the embryo travels to the placenta through arteries of the umbilical cord and returns via the umbilical vein

63. Maternal
arteries
Maternal
veins
Placenta
Maternal portion
of placenta
Umbilical cord
Chorionic villus
containing fetal
capillaries
Fetal portion of
placenta (chorion)
Maternal blood
pools
Uterus
Umbilical arteries
Fetal arteriole
Fetal venule
Umbilical vein
Umbilical cord

64. The first trimester is the main period of organogenesis, development of the body organs

65. 5 weeks.
14 weeks.
20 weeks.

66. Second Trimester
During the 2nd trimester
The fetus grows and is very active
The mother may feel fetal movements
The uterus grows enough for the pregnancy to become obvious

67. Third Trimester
During the 3rd trimester, the fetus grows and fills the space within the embryonic membranes
A complex interplay of local regulators and hormones induces and regulates labor, the process by which childbirth occurs

68. Estrogen
Oxytocin
from
ovaries
from fetus
and mother’s
posterior pituitary
Induces oxytocin
receptors on uterus
Positive feedback
Stimulates uterus
to contract
Stimulates
placenta to make
Prostaglandins
Stimulate more
contractions
of uterus

69. Birth, or parturition, is brought about by a series of strong, rhythmic uterine contractions

70. Placenta
Umbilical
cord
Uterus
Placenta
(detaching)
Uterus
Cervix
Umbilical
cord
Dilation of the cervix
Expulsion: delivery of the infant
Delivery of the placenta

71. The Mother’s Immune Tolerance of the Embryo and Fetus
A woman’s acceptance of her “foreign” offspring is not fully understood
It may be due to suppression of the immune response in her uterus

72. Modern Reproductive Technology
Amniocentesis and chorionic villus sampling are invasive techniques in which amniotic fluid or fetal cells are obtained for genetic analysis
Noninvasive procedures usually use ultrasound imaging to detect fetal condition
Modern technology can help infertile couples by in vitro fertilization

73. Head
Head
Body
Body