1. Gamete Transport and
Fertilization

2. Semen release
• Trace the movement of sperm
• 200 million a day
• Semen released in 3 stages
– Bulbourethral glands
– Seminal vesicles and prostate
– Seminal vesicles
• Sperm is present in first stage

3. Contents of Semen
• Water
• Mucus
• Buffers
• Carnitine – metabolism of fatty acids
• GPC – diesterase in uterus breaks down
• Enzymes for clotting and liquefaction
• Zinc
• PG

4. Sperm Structure
• 40 to 500 million in each ejaculate
• 30% are abnormal
• Controversy over declining sperm counts
• Structure
– Neck
– Midpiece
– Tail
– Acrosome
• Inner and outer membranes

5. Sperm Transport
• 20 to 200 sperm reach the egg
• Vagina
– Semen coagulation – fibrinogenase
– Semen liquefaction
• Many sperm are into the cervix and uterus within
minutes
• Cervix
– Canal is narrow and filled with a thick mucus
– Mucus becomes more liquid before ovulation
– Cervical crypts

6. Sperm Transport
• Uterus
– Climb up uterus with flagella
– Oxytocin released by mechanical stimulation
of the cervix
– Movement of leukocytes
• Oviduct
– Sperm wait in the isthmus
– Infundibulum changes orientation
– Cilia of fimbria

7. Sperm Capacitation
• Gains ability to fertilize
• Modification of glycocproteins on head
• Thermotaxis?
• Sperm last for 6 days?
• Egg viable or 12 to 24 hours

8. Process of fertilization
• Ovum and cumulus oophorus
– Hyaluronidase breaks junctions between cells
• Zona pellucida
– ZP 1, 2 and 3
– Binding of sperm head to ZP3
• Initiates the acrosomal reaction
• ZP2 receptor in inner acrosomal membrane
maintains contact
• Perivitelline space
• Sperm attachment to membrane

9. Cortical reaction
• Prevention of polyspermy
• Ca in cytoplasm increases
• Cortical granules fuse with membrane
• Release contents into perivitelline space
• Completion of 2nd meiotic division
• Fusion of pronuclei
– Sperm mitochondria and tail are destroyed
• Role of ubiquitin

10. • Sex ratios
– 105 to 100
– Male fetuses suffer greater mortality
• Sex preselection
– Microsort method
– Preimplantation genetic diagnosis
• Multiple Embryos
– Fraternal and identical
• Parthenogenesis

11. Chromosomal Aberrations
• Most are aborted within first trimester
• Polar body fertilized – genetic mosaic
– Could result in intersex
• Androgenesis and gynogenesis
– Both are lethal
• Triplody
– Polyspermy
• Aneuploidy
• Chromosomal tranlocations