Gametogenesis

Question 1

Describe the human gametogenesis process.

Answer 1

Primordial germ cells in Epiblast
Invade genital ridges
Gonadal differentiation
Testes sex tubes and seminiferous tubules
Oogenesis -> Oogonia in ovaries
Primordial follicles (2n) arrest in prophase 1
(Diplotene stage)

PUBERTY
Mature Graafian follicle (2n) complete meisosis1
Secondary follicle arrest in metaphase 2
Ovulation
Complete meiosis 2 after fertilization 

Spermatogenesis -> PGC differentiation 
Spermatogonial stem cells (2n)
Primary spermatocytes in prolonged prophase
Secondary spermatocytes (2n)
Meiosis 2
Spermatids (n)
Spermiogenesis 
Spermatozoa (n)

Question 2

Describe the process of fertilization.

Answer 2

The process by which male and female gametes fuse in the ampulla of the uterine tubes to form a zygote

Sperm deposited on the cervix after ejaculation
Uterine contractions move sperm to tubes
Ovulation induces sperm motility
Sperm undergo capacitation in ampulla
A 7 hour process removing glycoprotein coat from acrosome

THREE PHASES OF FERTILIZATION

Phase 1 - penetration of corona radiata
Only can be done by capacitated sperm
Bind to zona pellucida

Phase 2 - penetration of zona pellucida
Bound sperm undergo acrosomal reaction
Releasing acrosin and trypsin
Sperm head touches plasma membrane

Phase 3 - fusion of membranes
First sperm head fuses
Cortical reaction and zona reaction prevent polyspermy
Meiosis 2 completed
Metabolic activation of egg
Male and female pronuclei replicate and fuse to form zygote