Fetus Flashcards
What is fetal Hb normal range?
17-19
Where does blood entering RV from the SVC go?
What is the oxygen content of this blood?
Via ductus arteriosus to the aorta distal to L subclavian
Then to the trunk and lower limbs
Less well oxygenated
Where does oxygenated blood in the umbilical vein go?
Via ductus venosus to IVC then via foramen ovale to L side of heart then to head and neck
What is the oxygen content of blood in the portal vein?
Deoxygenated
When does fetus start swallowing?
10-14w
Reaches 250ml/day at term
When does immature suck-swallow start?
33-36w
When does stomach motility and secretion and pancreatic zymogen granules start?
20w
Peristaltic activity develops gradually, mature by third trimester
When does bile metabolism start?
11w
When does bile secretion start?
22w
When does small intestine transport start of
Amino acids
Glucose
Fatty acids ?
14
18
24
Intestinal villi start at 7w and mature by 20w
Absorptive processes mature by 26w
When does urine production begin?
9-10w
When does reabsorption in LoH begin?
12w
Proportion of fetal vs adult blood flow to kidneys
Increase in early postnatal period
2-3 vs 20%
10% 4days
20% 2w
Main organ of fetal electrolyte balance?
Placenta
Main source of amniotic fluid
before 16 weeks
after 16 weeks
Skin, placenta
Fetal urine, lung
Oligohydramnios not usually evident before 16w
Tonicity of fetal urine and cause
Hypotonic
Fetal kidney poor concentrating ability
Gestation at which number of nephrons reaches adult
34w however functional maturity not complete until postnatally
Main haemopoietic organ in fetus
Liver
Composition of meconium
75% water Intestinal secretions Squamous cells Lanugo hair Bile pigments Pancreatic enzymes Blood
Start of meconium production
10-12w
Moves into colon 16w
Incidence of meconium stained liquor
12% overall
30% post-term
Aspiration 5% - mechanical blockage and chemical pneumonitis
Formation of vernix
17w - sebaceous secretions and desquamated cells
Skin nearly 100% water <20%
Increase in connective tissue, keratinisation, vernix.
Skin still contributes to amniotic fluid
Most active period fetal neuronal proliferation
12-16w (from 8-20) Cortex majority neurons 20w along with spontaneous EEG activity, synchronised 26w, sleep/wake cycles 30w Cerebellum not until 1yr pn Synapse formation from 12w Myelinisation 24w
Peripheral ganglia origin and appearance
Neural crest 4-5w
Ventral motor
Dorsal sensory
Body and limb movement
7w, 9w
Maternal perception FMs
16-24w
Development smell, taste, gearing, vision
23-26w
Touch sensation
Pain repsonse
Afferents synapses from 10
Physiological stress response from 19w
Amniotic fluid volume 12w 16w 34w Term
50ml
150ml (then inc 50ml/wk)
1000ml
500ml
Composition amniotic fluid
>98% water Minerals Na, K, Cl CHO glucose, fructose Proteins alb, glob Lipids cholesterol, lecithin Hormones Enzymes ALP,lysozyme, peroxidase Suspended materials
Effect of fetal age on osmolarity
Decreases with gestation
1st period fetal hematopoiesis
Mesoblastic in yolk sac 12d-14w
2nd period fetal hematopoiesis
Hepatic from 6w
Peak 10-18
3rd period fetal hematopoiesis
Myeloid 8w-adult
Site of fetal EPO production
Initially liver then kidneys
Increases from 20w
Start and site of fetal WBC formation
6w liver, also spleen thymus lymphatic system
Surfactant production and composition
Lipoprotein produced by type II pneumocytes
90% lipids DPPC 2/3
10% protein including surfactant proteins A-D
Function of surfactant
Reduces surface tension - mainly DPPC
Increases compliance
Factors stimulating fetal lung maturation
Glucocorticoids
Thyroid hormones
Prolactin
Catecholamines
Factors delaying fetal lung maturation
Androgens - male infants increased resp distress
Maternal diabetes
