Embryology
Gametogenesis
The process where sex cells
(gametes) mature
Males: Spermatogenesis –
spermatozoa - testes
Females: Oogenesis – oocytes -
ovaries
Purpose of gametogenesis
o To half the number of chromosomes
Haploid (23 chromosomes)
After conception it will be
restored: Diploid (46 chromosomes)
o Changes to cytoplasm
♀ Oocyte: Retain cytoplasm
• Large quantity of cytoplasm: for nutrition
♂ Sperm: Looses cytoplasm and acquire tail
• Changes promotes movement,
penetration
Sperm structure
o Specialised for function - movement
o Made up of three part
Head (nucleus covered by acrosome)
with neck
Body/Middle piece
Tail
Ovum structure
o Meiosis is incomplete when released
(ovulation)
o Surrounded by zona pellucida and corona
radiata
o Rich in cytoplasm
Nutrients for after fertilization
Fertilization
Occurs within 24 hours after ovulation in ampulla of fallopian tube
Sperm burrows through corona radiata and zona pellucida
Fusion of sperm and ovum
, • Only head and tail enter ovum
• Acrosome stays behind
• Zona pellucida becomes impermeable to other sperm
Restores chromosome number
• 23 to 46 (44 + XX)/ (44 + XY)
Zygote
Initiates cleavage
Cleavage
Repeated division of the zygote via mitosis
Forms blastomeres (daughter cells)
No increase in size of zygote - Blastomeres becomes smaller with each
division
Increase in cell number
Occurs from within the uterine tube until it reaches the uterine cavity
o Various stages
2-cell stage
4-cell stage
Morula (12+ cells)
Blastocyst
Morula
o In fallopian tube day 3/4 after fertilization
o Zona pellucida prevents implantation
o Fluid filled cavity starts to form on one side
o Known as blastocyst once it reaches the uterine cavity
Gametogenesis
The process where sex cells
(gametes) mature
Males: Spermatogenesis –
spermatozoa - testes
Females: Oogenesis – oocytes -
ovaries
Purpose of gametogenesis
o To half the number of chromosomes
Haploid (23 chromosomes)
After conception it will be
restored: Diploid (46 chromosomes)
o Changes to cytoplasm
♀ Oocyte: Retain cytoplasm
• Large quantity of cytoplasm: for nutrition
♂ Sperm: Looses cytoplasm and acquire tail
• Changes promotes movement,
penetration
Sperm structure
o Specialised for function - movement
o Made up of three part
Head (nucleus covered by acrosome)
with neck
Body/Middle piece
Tail
Ovum structure
o Meiosis is incomplete when released
(ovulation)
o Surrounded by zona pellucida and corona
radiata
o Rich in cytoplasm
Nutrients for after fertilization
Fertilization
Occurs within 24 hours after ovulation in ampulla of fallopian tube
Sperm burrows through corona radiata and zona pellucida
Fusion of sperm and ovum
, • Only head and tail enter ovum
• Acrosome stays behind
• Zona pellucida becomes impermeable to other sperm
Restores chromosome number
• 23 to 46 (44 + XX)/ (44 + XY)
Zygote
Initiates cleavage
Cleavage
Repeated division of the zygote via mitosis
Forms blastomeres (daughter cells)
No increase in size of zygote - Blastomeres becomes smaller with each
division
Increase in cell number
Occurs from within the uterine tube until it reaches the uterine cavity
o Various stages
2-cell stage
4-cell stage
Morula (12+ cells)
Blastocyst
Morula
o In fallopian tube day 3/4 after fertilization
o Zona pellucida prevents implantation
o Fluid filled cavity starts to form on one side
o Known as blastocyst once it reaches the uterine cavity
