Terms in this set (121)

• After ovulation the egg lasts 6‐24 hours
• After ejaculation sperm last 24‐48 hours
• Fertilization takes place in the uterine tube
• Egg cell moves through uterine tube after
ovulation (contractions and ciliated cells)
• Spermatozoa mature as they pass through
epididymis (10‐14 days)
- Motility (movement forward)
- Binding proteins for zona pellucida
• at ovulation cervical secretions are watery and
less acidic (more favourable for moving
sperm)
• cervical crypts are reservoirs for escaping
sperm
• 1% or less of sperm move to uterus
• only 20‐30 out of 150‐200 million reach egg
• A single sperm cell fertilizes the egg
• Sperm head binds zona pellucida
- species‐specific receptors (ex. A mouse sperm
would not bind to the zona pellucida of a human's
egg)
• Acrosome of sperm releases digestive
enzymes which break down zona pellucida
• Sperm passes through zona pellucida
• Sperm binds to egg membrane
• Only one sperm enters egg
• Chemical changes to plasma membrane and
zona pellucida prevent other sperm from
binding
- Egg cell membrane changes properties
(depolarization)
- Cortical granules release enzymes
- Zona pellucida becomes a fertilization membrane
preventing other sperm from fertilizing.
• Plasma membranes fuse
• meiosis II is resumed in the secondary oocyte,
producing a polar body and a pronucleus with a
haploid number of chromosomes
• Sperm cell contents enter egg
• Sperm pronucleus and egg pronucleus fuse and
are surrounded by a nuclear membrane
• Granules release enzymes that convert the zona
into a fertilization membrane
- harden the zona
- prevent other sperm from binding
• At the end of week 1 - reaches uterus as a
blastocyst
• implantation of blastocyst marks beginning of
embryonic development
- trophoblast and inner cell mass (2 distinct tissues)
• "hatches" out of zona pellucida
- zona pellucida prevents blastocyst from
implanting before it reaches uterus)
- until this time 32‐64 cells have been in zona
pellucida, the size of the original fertilized egg
• Inner Cell Mass
- gives rise to embryo which later becomes a fetus
- starts out with 8 cells
- about 4 for body
- about 4 for extraembryonic tissues - the yolk sac
and the amnion
• Trophoblast
- gives rise to tissues for placenta
- secretes enzymes to digest part of endometrium
- secretes human chorionic gonadotropin
• Acts like LH
• marker of clinical pregnancy through blood test
• preserves corpus luteum which releases progesterone
and keeps uterine lining intact
• Uterus is in its secretory phase
- Luteal phase in ovary
- Progesterone is released by corpus luteum
- Endometrium is maintained by progesterone
levels
• Uterine glands complete growth and release a
secretion high in glycogen
• Spiral arteries form in the endometrium
• once in uterus - blastocyst attaches to endometrium
(usually back wall of uterus)
• endometrium attachment through trophoblast
- secretes enzymes that digest tissues
- blastocyst burrows into lining
• blastocyst completely embedded after 12 days
• contact with mother's blood vessels
• Trophoblast secretes human chorionic gonadotropin
- Acts like lutenizing hormone during pregnancy
- Maintains corpus luteum (progesterone secretion) and
uterine lining
;