SEXUAL REP

• Sexual Reproduction


  Involves fertilization of an egg (n, haploid) by a sperm (n, haploid) which produces a zygote (2n, diploid)
• Egg


  • Large cell compared to small and motile sperm
• Hermaphroditism


  Having both sex organs, so every individual is a possible mate
• Hydra can switch from asexual to sexual reproduction
• External Fertilization


  Used by aquatic animals such as fishes and amphibians, where both male and female release their gametes in the environment
• Internal Fertilization


  Used by terrestrial organisms, where the sperm should be near the egg inside the female reproductive tract for fertilization to take place
• Similarities in Female and Male Reproductive systems

  • Gonads for gamete production
  • Ducts for gamete delivery and stockpiling
  • Structures for copulation

  
• Ovary


  Where the egg cells are produced; the female gonad
• Egg cells


  • Develop surrounded by follicle cells which nourish them
  • Estrogen are also produced by the follicles
• Females are born with finite number of follicle cells (approx. 1-2 million), of which only 500 are released during a female's reproductive years
• Ovulation


  The monthly release of one egg, starts at puberty and ends at menopause
• Egg cell movement


  1. From the ovary, the egg cell moves towards an oviduct/fallopian tube

  2. The egg cell is swept from the ovary by the cilia at the finger-like projections of the oviduct
• Fertilization


  Can occur in the oviduct if sperm cells are present
• Zygote movement


  The zygote moves from the oviduct towards the uterus where pregnancy normally occurs
• Embryo and Fetus development

  In the uterus, the zygote develops into an embryo and later into a fetus

  
• Endometrium


  • Lining in the uterus that is rich with blood vessels that pass nutrients to and wastes from the embryo to the mother
• Cervix


  Forms the neck of the uterus found at its base
• Vagina


  Thin but composed of strong muscles, receives the sperm during copulation and functions as the canal where the fetus is delivered during birth
• Female external genitalia


  • Vulva
  • Labia minora
  • Labia majora
  • Hymen
  • Clitoris
• Testes


  The male gonad which produces the sperm
• Sperm movement


  1. From each testis, the sperm cells swim to the epididymis where they further develop and are stored

  2. They then move to the vas deferens through muscular contractions

  3. The vas deferens circles the urinary bladder then join with the duct of seminal vesicle to form the ejaculatory duct which empties into the urethra

  
• Penis


  Has structures similar to those in clitoris, such as glans (head), shaft (body), and prepuce (foreskin)
• Semen


  Made up of sperms secreted by three glands: seminal vesicle, prostate, and bulbourethral gland
• Ejaculation


  The release of the semen, occurs during male orgasm
• Spermatogenesis


  1. Sperm production, is prolific, continues, starts during male puberty, and goes on until old age

  2. For every one diploid parent cell, four haploid cells are produced
• Oogenesis


  1. Egg cell production, starts at birth, continues at puberty, and commonly waits for sperm to fertilize it

  2. Only one haploid egg cell is produced from every one diploid parent cell
• Female Reproductive Hormones


  • Gonadotropin-releasing hormone (GnRH) - Hypothalamus
  • Prolactin - Anterior Pituitary
  • Oxytocin - Posterior Pituitary
  • Androgens - Adrenal Gland
  • Human Chorionic Gonadotropin (hCG) - Embryo
• Ovarian cycle


  The cyclical production of an egg cell in the ovary, usually recurs every 28 days and simultaneously happens with the events in the uterus called the menstrual cycle
• Fertilization


  The meeting of the sperm and egg where both gametes contribute haploid sets of chromosomes to form the diploid zygote

  
• Fertilization process


  For fertilization to occur, the sperm has to penetrate the egg's covering and be recognized by receptors on its surface
• Embryonic Development


  1. Cleavage

  2. Blastula

  3. Gastrula (forms the digestive tract, nervous system, and outer layer of skin)

  4. Mesoderm (forms other organs such as muscle, heart, kidney, and inner layer of skin)

  
• Organogenesis


  1. Starts immediately after the germ layers are formed, each group of cell begins developing into embryonic organs shortly after gastrulation

  2. Induction (cells influence the behavior of other cells to develop into specific tissues)

  3. Cell migration (helps form differentiated tissues)

  4. Apoptosis (during hand development, cells in between fingers are killed)
• Monozygotic twins


  Formed when one fertilized egg (ovum) splits and develops into two babies with exactly the same genetic information
• Dizygotic twins


  Formed when two eggs (ova) are fertilized by two sperm and produce two genetically unique children
• Human Embryonic Development


  1. First trimester (organogenesis, most delicate stage)

  2. Second trimester (continued growth and development of organs)

  3. Third trimester (dramatic and rapid fetal growth)

  
• Premature infants are born before 37 weeks, early term is 37-38 weeks, full term is 39-40 weeks, late term is 41 weeks, and post-term is after 42 weeks