Animal Reproduction and Development

1
Animal Reproduction and Development

• Chapter 39

2
Stages of Development

• Gamete formation
• Fertilization
• Cleavage
• Gastrulation
• Organ formation
• Growth, tissue specialization

3
Gastrulation

• Sphere of cells is a blastula
• During gastrulation, some cells move inward
• Produces a three-layer embryo

4
Cell Differentiation

• Certain groups of genes are activated in some
  cells but not in others
• Genes are not lost, just inactivated

5
Morphogenesis

• Orderly changes result in specialized tissues and
  early organs
• Cells migrate
• Whole sheets of cells expand and fold
• Programmed cell death sculpts body parts

Cell migration
6
Male ReproductiveSystem
bladder
seminal vesicle
vas deferens
prostate gland
bulbourethral gland
urethra
epididymis
scrotum
testis
penis
7
Semen Sperm Secretions

• Secretions from epididymis aid sperm maturation
• Seminal vesicle secretes fructose and
  prostaglandins(causes muscles to contract)
• Prostate gland secretions buffer pH in the acidic
  vagina
• Bulbourethral gland secretes mucus

8
Spermatogenesis

• Meiosis produces haploid spermatids
• Spermatids mature to become sperm
• Sperm develop in the seminiferous tubule

9
Other Testicular Cells

• Leydig cells
• Lie between the seminiferous tubules
• Secrete testosterone

10
FSH and LH

• FSH and LH are formed in the Anterior Pituitary
  Gland
• In males it stimulates the production of
  testosterone and spermatogenesis
• In female the hormones are responsible for
  stimulating the maturation of an ova and causes
  ovulation.

11
Male Hormonal Control
Hypothalamus
GnRH
Inhibin
Anterior Pituitary
LH
FSH
Sertoli cells
Leydigcells
Testes
Testosterone
Formation and Development of Sperm
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Female Reproductive Organs
oviduct
ovary
ovary
uterus
uterus
oviduct
vagina
cervix
vagina
13
Menstrual Cycle

• The fertile period for a human female occurs on a
  cyclic basis
• Menstrual cycle lasts about 28 days
• Follicular phase and luteal phase

14
Oocytes Arrested in Meiosis I

• Girl is born with primary oocytes already in
  ovaries
• Each oocyte has entered meiosis I and stopped
• Meiosis resumes, one oocyte at a time, with the
  first menstrual cycle

15
Ovarian cycle
secondary oocyte
first polar body

• Follicle grows and matures
• Ovulation occurs
• Corpus luteum forms

antrum
corpus luteum
primordial follicle
16
Female Hormonal Control
Hypothalamus
GnRH
Rising estrogen stimulates surge in LH
Anterior Pituitary
Progesterone, estrogens
LH
FSH
Ovary
Follicle growth, oocyte maturation
Estrogen
Corpus luteum forms
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Cycle Overview
hypothalamus
GnRH
anterior pituitary
FSH
LH
FSH
LH

• GnRH secretion affects LH and FSH secretion by
  pituitary
• LH and FSH affect follicle maturation
• Estrogen and progesterone from ovary affect uterus

FSH
LH
LH
ovulation
estrogens
estrogens
progesterone
estrogens
menstruation
FOLLICULAR PHASE
LUTEAL PHASE
18
Fertilization

• Sperm penetrates the egg cytoplasm
• Egg nucleus and sperm nucleus fuse to form
  diploid zygote
• (46 chromosomes)

19
Early Divisions

• Cleavage begins within 24 hours of fertilization

Day 1
Day 4 (morula)
Day 2
Day 3
20
Day 5 - Blastocyst Forms

• Cell secretions produce a fluid-filled cavity in
  center of ball of cells

inner cell mass
21
Implantation Begins

• Blastocyst attaches to endometrium begins to
  burrow into maternal tissues

Uterine cavity
blastocoel
inner cell mass
trophoblast
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Human Chorionic Gonadotropin (HCG)

• Hormone secreted by the blastocyst
• Stimulates corpus luteum to keep making
  progesterone and estrogens
• This maintains endometrium, prevents menstruation
• Can be detected by week 3 with a home pregnancy
  test

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Gastrulation - Day 15

• Formation of the three tissue layers
• Ectoderm, mesoderm, endoderm

24
Stages of Human Development - Prenatal

• Zygote - Single cell
• Morula - Solid ball of cells
• Blastocyst - Ball with fluid-filled cavity
• Embryo - 2 weeks to 8 weeks
• Fetus - 9 weeks to birth

25
Birth Control Options

• Prevent fertilization
• Prevent ovulation
• Block implantation

26
Sexually Transmitted Diseases (STDs)

• Worldwide epidemic of STDs
• Women are most affected
• Can cause infertility, pain, and even death

27
Causative Agents of STDs

• Viruses
• AIDS (HIV)
• Genital herpes (Herpes simplex)
• Genital warts (HPV)

• Bacteria
• Gonorrhea (Neisseria gonorrhoeae)
• Syphilis (Trepnema pallidum)
• Chlamydial infections

28
AIDS

• Virus attacks T cells
• Immune system is destroyed
• Opportunistic infections and cancers eventually
  cause death
• Treatment is available, but there is no vaccine
  and no cure

29
AIDS Test

• Should know HIV status of potential partner
• A person can test negative and still have and
  transmit the virus
• Test detects antibodies that appear weeks to
  months after infection

30
Genital Herpes

• Caused by Herpes simplex Type II
• Periodic eruption of small, painful blisters on
  genitals
• Infection requires contact with fluid from these
  sores
• Antiviral drugs can reduce pain but there is no
  cure

31
Human Papillomaviruses

• HPV can cause bumplike warts on the genitals and
  anus
• One strain, 16 HPV, does not cause symptoms
• It can lead to cancers of cervix, vagina, vulva,
  penis, and anus
• There is no cure

32
Gonorrhea

• Caused by the bacterium Neisseria gonorrhoeae
• Females often symptom-free in early stages, males
  discharge pus
• Can cause sterility if untreated
• Can be cured with antibiotics

33
Syphilis

• Caused by the spirochete Treponema pallidum (a
  kind of bacterium)
• Early symptoms are painless chancres later an
  extensive rash
• In some, immune response to infection causes
  damage to brain and spinal cord
• Passage from mother to infant can cause
  stillbirth, infection of newborn

34
Chlamydial Infections

• Most common reported STD in U.S.
• A variety of diseases caused by bacterium
• Leads to inflammation of cervix in female,
  burning urination in both sexes
• In females, can spread to uterus and oviducts to
  cause PID

35
Pelvic Inflammatory Disease (PID)

• Complication of many bacterial STDs
• Bacteria infect uterus, oviducts, ovaries
• Symptoms include bleeding, vaginal discharge,
  pain in lower abdomen
• Increases likelihood of ectopic pregnancy
• Can cause sterility

36
In Vitro Fertilization

• Conception outside the body
• Woman receives hormone injections to stimulate
  ovulation
• Oocyte is removed and combined with sperm in
  petri dish
• After fertilization and a few divisions, ball of
  cells is implanted in uterus