Animal Reproduction

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Animal Reproduction
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Asexual Reproduction

• Produced genetically identical individuals
• Examples hydra, sponges

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Sexual Reproduction

• Fusion of two haploid cells to form a diploid
• Meiosis produces haploid cells
• Mechanism to bring haploid cells together must be
  present
• Mechanism to create genetic diversity

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Fertilization

• Haploid sperm and egg unite to form a diploid
  zygote

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External Fertilization

• Sperm spread over egg cells
• Requires water
• Most aquatic animals
• Examples most fish, corals, starfish
• Inefficient
• Spermatophore sperm packaged into capsule
• Some terrestrial animals
• Examples salamanders, scorpions, octopus

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Internal Fertilization

• Requires copulation
• Most common method for terrestrial animals
• Less sperm and eggs needed

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Human Reproduction
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Male Reproductive Organs
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Male Reproductive Organs

• Testes
• Sperm and testosterone
• Seminal vesicle
• Fructose and prostaglandin
• Prostate
• Basic fluid and sperm motility factors
• Bulbourethral gland
• Mucus

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Testes

• Produce sperm and testosterone
• Spermatogenesis
• Spermatogonium divides by mitosis
• Meiosis I
• Primary spermatocyte (2n) ? secondary
  spermatocyte (1n)
• Meiosis II
• Secondary spermatocyte (1n) ? spermatids (1n)
• Differentiation
• Spermatids (1n) ? sperm (1n)

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Testes
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Spermatogenesis
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Androgens Male Sex Hormones

• Main androgen is testosterone
• Made by the Leydig cells of testes
• Purpose
• Maintain primary and secondary sex
  characteristics
• Promote sexual behavior and sex drive
• Promote spermatogenesis

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Sperm Structure

• Acrosome
• Digests egg protective barrier to allow nucleus
  to enter egg
• Middle Piece
• Mitochondria
• Flagellum
• Microtubules
• Controlled by centrioles

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Female Reproductive Organs
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Female Reproductive Organs

• Ovary
• Produce oocytes
• Meiosis I
• Produces hormones (estrogen and progesterone)
• Oviduct (fallopian tube)
• Transmits oocyte to uterus
• Site of fertilization
• Meiosis II
• Uterus
• Zygote implantation
• Placental development

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Ovary and Oogenesis

• Meiosis I
• Inside ovary
• Primary oocyte (2n) ? Secondary oocyte (1n)
• Meiosis II
• Inside oviduct after fertilization
• Secondary oocyte (1n) ? Ovum (1n)
• Only one egg forms, other products of meiosis
  form polar bodies

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Ovary and Oviduct
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Ovary and Oogenesis
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Female Reproductive Cycle

• Cyclic pattern (average 28 days)
• Menstrual and ovarian cycles
• Controlled by hormones
• Gonadotropin
• LH luteinizing hormone
• FSH follicle-stimulating hormone
• Ovarian hormones
• Estrogen
• Progesterone

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Menstrual Cycle

• Three phases
• Menstrual flow phase (few days)
• Endometrial surface lost
• Proliferative phase (1-2 weeks)
• Endometrium regenerates
• Secretory phase (2 weeks)
• Endometrium thickens
• Glands develop and secreted glycogen

No embryo implantation
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Ovarian Cycle

• Two phases
• Follicular phase
• Primary follicle grows into a mature follicle
  (Graafian follicle)
• Ovulation occurs at the end of this phase
• Luteal phase
• Follicle cells become endocrine tissue and
  secrete hormones

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Menstrual and ovarian cycles

• Menstrual and ovarian cycles run in parallel

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Ovulation, Fertilization and Implantation
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Fertilization

• Acrosome discharges enzymes to digest zona
  pellucida
• Once single sperm enters egg
• Egg releases enzymes that harden zona pellucida
  preventing other sperm from entering
• Sperm nucleus enters egg and fuses with egg
  nucleus

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Placenta