ANP 1107 - Pregnancy and Development Flashcards
Pregnancy
Events that occur from fertilization until the infant is born
Conceptus
Women’s developing offspring
Gestation Period
Time from last menstrual period to birth
Embryo
Conceptus from fertilization to week 8
Fetus
Conceptus from week 8 to birth
Viability of Oocyte
12 - 24 hours
Viability of Sperm
24 - 48 hours
Fertilization
When sperms chromostomes combine with those of an egg, forming ZYGOTE
Loss of Sperm
- Leak from Vagina
- Destroyed in acidic environment
- Fail to enter cervix
- destroyed by resident phagocytes
Capacitation
- Must occur within 8-10 hours
- Enhances mobility and weakens membranes
- This allows hydrolytic enzymes in the acromosome to be released
- Sperms membrane protein are removed
- Cholesterol is depleted, a membrane no longer tough
Acrosome Reaction: Step 1
Hyaluronidase on sperm digests intracellular fluid cement btw granulosa cells –> fall away from oocyte
Acrosome Reaction: Step 2
sperm binds to the ZP3 glycoprotein of the zona pellucid - sperm receptor. Causes increase Ca+ = acrosomal reaction
Acrosome Reaction: Step 3
Reactrion involves the breakdown of the plasma membrane and acrosomal membrane –> releases acrosomal enzymes which digest holes thru zone pellucida
Acrosome Reaction: Step 4
Acrosomes undergo exocytosis digests more holes in zona pelucida
xAcrosome Reaction: Step 5
path cleared, sperms go to oocytes membrane. At the same time, actin from sperm binds to oocytes binding receptor
Acrosome Reaction: Step 6
Binding leads to
(1) oocyte and sperm fuse
(2) sperm contents enter oocyte
(3) gametes are fused together perfectly
Polyspermy
- Entry of several sperm into an egg
- Occurs in some animals
- Humans (monospermy)
Blocks to Polyspermy
- Sperm enters oocyte, calcium released by oocyte ER
- calcium surge –> cortical reaction
Cortical Reaction
- Granules inside plasma membrane spill out enzymes into extracellular space
- ZIPS destroy sperm receptors
- Prevents sperm from entering
Slow Block to Polyspermy
- Spilled material binds water
- Material swells and hardens, detaches sperm receptors on oocyte
Zygote
- A diploid cell resulting in fusion of two haploid gametes
Clevage
- Early events in embryonic period
- Produces a blastocyte
- Rapid division of the zygote
Small Cells with High Surface-to-Volume Ratio
- Enhances uptake of nutrients and oxygen and the disposal of waste
- Provides large amount of cells to serve as building blocks
36 Hours After Fertilization
- First cleavage division of zygote
- Creates two identical blastocytes
- Divide to produce 4, 8 cells
71 Hours
- Loos collectionof cells that form from a berry-shaped cluster of 16 or more cells - MORULA
4-5 Days After
- Embryo consists of 100 cells
- Begins to float free in uterus
Implantation
Blastocyte burrows into endometrium
Morula
- Loose collection of cells
- Forms a berry shaped cells cluster of 16 or more
Blastocyte
- Fluid filled hollow sphere composed of a single layer of large, flattened cells (trophoblast cells)
- Small cluster of 20-30 rounded cells to one side called inner mass
Hatching
- At day 5, blastocyte hatches out of the ZP
- Allows increased growth, access to unterine nutrient secretions and blastocyte adhesion to the uterine lining
Paturation
- Giving birth to the baby