Fetal Well-Being In Labor Flashcards
When does implantation occur?
b/w days 6-10
What is the function of the trophoblast layer?
- invades decidua basalis
- remodels spiral arteries
- form placenta
When does the placenta begin to function?
10-12wks GA
What is the function of the syncytiotrophoblast?
outer trophoblast layer
- sends finger-like projections into endometrium
- develop lacunae that fill with serum from spiral arteries –> nourish trophoblast
- communication b/w lacunae and uterine vessels begin uteroplacental circulation
What is the function of the cytotrophoblast?
inner layer of trophoblasts
- become chorionic villi
- establish venous network that supplies fetus
When does fetal blood circulation begin?
~21 days w/in chorionic villi
Where does gas exchange occur?
intervillous space of placenta
What are the 4 types of diffusion?
1) simple = from high concentration to low concentration (e.g. O2, CO2)
2) facilitated diffusion: requires transporter but no energy (e.g. glucose, cholesterol)
3) active transport = against concentration gradient; needs transporter (e.g. amino acids, vitamins, Fe)
4) pinocytosis: carrier engulfs molecule and moves it across placental barrier (e.g. IgG)
What is required for optimal uteroplacental circulation?
1) adequate maternal blood flow to intervillous space
2) large placental area for gas and nutrient exchange
3) efficient gas/nutrient diffusion
4) unimpaired umbilical vein circulation
5) adequate oxygen transport capacity in fetus
What maternal pre-existing conditions can impede uteroplacental circulation?
- HTN
- CAD
- DM
- renal disease
- smoking
- abruption
- pre-eclampsia
What are the primary functions of the sympathetic nervous in the fetus?
1) increase FHR
2) vasoconstriction
3) increase fetal BP
What controls FHTs?
1) SNS
2) PNS
3) CNS
4) chemoreceptors
5) baroreceptors
When during pregnancy is the sympathetic nervous system dominant?
1st trimester
When during pregnancy does the parasympathetic nervous system mature and dominate?
2nd trimester
What is the overall effect of the PNS on FHR?
gradually slows baseline HR
What mediates the PNS?
vagus nerve
What sets the highest intrinsic HR?
SA node
What causes FHR variability?
vagal stimulation –> varies interval b/w successive beats –> changes FHR
Where are chemoreceptors located?
1) aortic arch
2) CNS
What stimulates chemoreceptor response?
1) O2 content
2) CO2 content - if increased –> chemoreceptors alert medulla oblongata to stimulate vagus nerve –> slows FHR
Where are baroreceptors located?
1) aortic arch
2) carotid arch
What stimulates baroreceptor response?
increased BP –> quick reflex vagus nerve response –> slows FHR
Chemoreceptors affect (short/long)-term control of FHR.
long
What type of control do baroreceptors offer?
short-term control of HR and BP
