Fetal Nourishment and Development Flashcards
What causes the accumulation in size around 20 weeks
The baby starts building up proteins and lipids
Zona Reaction
Sperm head contains enzymes that allow it to penetrate the acrosome wall and make the egg impenetrable to any other sperm
What are the 3 layers of the egg
Corona radiata
Zona pellucida
Oolemma/oocyte
Where does fertilization occur in the vagina?
fertilize in the widest part of the fallopian tube (close to fimbria)
4 stages to early implantation
Stage 1: fertilization to a Zygote
Stage 2: zygote divides 2- — Morula (16-32) uterine cavity
Stage 3: Early blastocyst to late blastocyst (uterus wall)
Stage 4: implantation
Zona pellucida important for dividing cells because
it provides a source of nutrients to cells that are dividing
When does the Zona pellucida degarde
when it enters the uterus (day 4-5)
How is nutrients provided after zona degrades
Supplied from secretion of the uterine glands - glycogen (main)
Blastocyst (describe)
Hollow ball with Inner cell mass
Trophoblast - outer layer
Early week 2
Trophoblast cells secrete enzymes that help it burrow into the endometrium — once fully attached it can begin to receive nutrients
Later week 2
Inner cell mass becomes flattened disc and amniotic cavity develops
2 layers form - Epiblast and hypoblast
Epiblast layer
Next to amniotic cavity
Gives rise to Ectoderm and mesoderm
Hypoblast layer
Next to blastocyst cavity
Gives rise to endoderm
Gets thickkk = cranial region
Purpose of the Lacunar networks
beginning of maternal-fetal circulation - develops within trophoblast - primary chorionic villi
What occurs week three of embryotic development
Gastrulation - formation of the 3 germ layers
Neurulation - formation of the central nervous system
Cardiovascular system begins
What are the three germ layers
Ectoderm, Endoderm, Mesoderm
Ectoderm
Epidermis, hair, nails, teeth enamel, internal ear, retina
CAN, PNS
Endoderm
Lining of respiratory and gastro tract
Epithelium of liver, pancreas, bladder
Mesoderm
SKM, CV System, reproductive and excretory system
Why would the pancreas be unaffected by maternal folate amounts
It does not develop until the 3rd trimester
Later week 3
Folding of the neural tube
Development of paired somites from mesoderm, Coelom, link heart tubes, completion of chorionic villi
Where would malformation resulting in spina bifida occur
the neural crest
Purpose of the chorionic villi
Finger like projections on surface of placenta - play a key role in the exchange of nutrients, oxygen and waste products between mother and fetus
Sequential gene
Week 4-8, major folding transverse and longitudinal - controlled by sequential gene
Week 4 is
Neural tube ends close
Heart now pumps blood
Development of forebrain, limb buds, internal ears, eye lens
Week 5-6 is
Rapid development of brain which requires DHA
Head grows much greater than trunk
Week 7-8 is
Limb development including bones
GI tract formation (produces enzymes)
Accumulation of body fat % at week 29 compared to 38. Why?
29 = 3.5% 38 = 16%
No fat at 29 weeks, but most of the developmental structures are there
What is the difference of focus from week 8 to week 9 from a nutritional perspective?
Week 8 - Quality
Week 9 - Quality and quantity
2 Parts to the placenta
Maternal - Endometrium layer - Lacunae structure
Fetal party - Chorionic villus
When and how does the Placental Villi complete
Week 3
Trophoblast vessels
SA increase
Differentiate between the umbilical vein and arteries
Vein: Allows for nutrient to be transferred to fetus
Arteries: Brings O2 and nutrient depleted blood back to mom.
What are the 3 functions of placenta
-Hormone secretion - HCG, estrogen, progesterone, placental lactogen
-Metabolism
-Transfer of nutrients and other substances
Which hormone is the marker for pregnancy
Human chorionic gonadotropin hCG - Week 10 (depletes after)
What does the placental metabolize
Glycogen, Cholesterol, FA
Why does progesterone stay high when pregnancy is confirmed?
Prepares the uterus for pregnancy - prevents endothelial cells from sloughing off
What are the 4 mechanisms of transfer for placental transfer
Simple diffusion - Water, FAs, Na, Cl
Facilitated diffusion - glucose, iron, vit A, D
Active transport - AA, water soluble vitamins
Endocytosis - albumin, immunoglobulins
Why would FFA be passive to the fetus
The baby needs lots of supply, Concentration gradient
Describe the placental transfer of glucose
Facilitated diffusion, controlled by placental metabolism.
Placenta uses 30-40% of glucose taken up from maternal circulation
Describe the placental transfer of lipids
simple diffusion or facilitated.
N-6 & n-3 are transferred through pregnancy - due to importance
But lipids for fetal adipose tissue are transferred late in gestation
Control and Transfer of AA
Transfer Active transport
Controlled by Placenta SA, Placenta blood flow, placental permeability & conc gradient of protein
