Fetal Development Flashcards
Amniotic Fluid
- 98% water
- Slightly alkaline
- Contains fetal urine, nutrients, hormones, antibodies, skin cells, & lanugo
The average volume of amniotic fluid at birth
800-1000mL
(Poly)hydramnios
> 2000mL of amniotic fluid
Oligohydramnios
<300mL of amniotic fluid
Functions of amniotic fluid
- Maintains even temperature
- Permits embryo to float and develop symmetrically
- Aids in the development of lungs and GI
- Cushions against blows to the abdomen
Placenta
- Temporary organ
- Forms around week 3 and grows through week 20
Maternal Side of Placenta
- “Raw beefy” appearance
- “Dirty Duncan”
Fetal Sid of Placenta
- Shiny appearance
- “Shiny Schultze”
- Umbilical cord attached in center
Placenta Funtions
- Gas exchange between mother and fetus
- Nourishment and Excretion
- Hormone Production
- Barrier to nicotine, drugs, alcohol, viruses can cross
How does the placenta perform gas exchange
2 arteries carry deoxygenated blood to mother and 1 vein carries oxygenated blood to fetus
How does the placenta aid in nourishment and excretion
Delivers nutrients and clears fetus’s metabolic waste products
Placenta Hormones
- Influences growth and maintains pregnancy
- HCG, Estrogen, Progesterone, HPL, Relaxin
Wharton’s Jelly
Substance surrounding umbilical cord that keeps the vessels separate to keep the cord from kinking
Pre-embryonic Stage
Begins with fertilization through implantation
What does ectoderm form?
Skin & nervous system
What does the endoderm form?
Lining of gut & internal organs
What does the mesoderm form?
Muscles, bones, & heart
Embryonic Stage
Starts around week 4 through end of week 8; size of a pinhead
What forms during embryonic stage?
- Tissue differentiation in all organs
- Week 3: Brain and all 12 cranial nerves present
- Week 4: Heart forms and starts beating
What grows during week 5?
- Lung structure
- Liver
- Pancreas
- Kidneys
- GI & sensory organs
- Arm and leg buds appear
Week 6
- Hematopoiesis begins (Formation of blood cellular components)
- Baby the size of a pea
Week 7 & 8
- Facial features develop
- Renal system begins to function
Week 8
- Begins to resemble human being
- Bone cells replacing cartilage
- Fingers & toes developing
- Size of kidney bean
Fetal Stage
Weeks 9-40
10-12 weeks
- Heartbeat can be heard by doppler
Weeks 11-12
Able to make breathing & random movements
12 Weeks
- Kidneys producing urine
- Digestive system shows activity
- Genitals well differentiated
- Endocrine organs producing hormones
16-20 weeks
- Quickening
- Lanugo
- Brown fat
- Alveoli in lungs forms
- Fetus can respond to sound
Quickening
Mother feels fetal movement
24 weeks
- Grasp & startle reflex evident
- Vernix present
- Nostrils open
- Respiratory movements occur with practice
- Alveoli contains some surfactant
Surfactant
Slippery substance on alveoli that helps keep them open and lowers surface tension to use less energy to breathe
28 Weeks
- Lashes & eyebrows present
- Eyelids can open & close
- Nervous system beings regulatory functions
- Testes descend into scrotum
- Looks like little old man
32 Weeks
- Respiration & thermoregulation possible if fetus developed
- Forming muscles & beginning to store fat
- Skeleton fully developed but not calcified to ease delivery
- 4-4.5lbs
36 weeks
- Diminishing lanugo
- Beginning to have “filled out” appearance (more adipose tissue)
- Soft ear shells and lobes
- Few creases in hands and feet
37-40 weeks
- Skin pink and smooth
- Vernix in skin folds
- Lanugo on shoulders and upper back
- Firm ear shells & lobes
- Many creases to palms and soles of feet
- Well developed labia/scrotum w/ rugae
Dizygotic Twins
- 2 ova fertilized by separate sperm (fraternal)
- May be same or different sexes
- Increases with frequency with increased maternal age & parity, family history (maternal), West African ancestry, and fertility drugs
Monozygotic Twins
- 1 ova, 1 sperm; fertilized egg produces 2 fetuses (paternal, identical)
- Always same sex (same genes)
- Increase with fertility drugs
