Fetal and neonatal physiology

Question 1

how do you calculate gestational age

Answer 1

fertilization age + 2 weeks

Question 2

growth: hyperplasia and hypertrophy

Answer 2

hyperplasia: increase in cell number
hypertrophy: increase in cell size

Question 3

___ is primary form of placental growth

Answer 3

hypertorphy

Question 4

intrauterine growth restriction

Answer 4

• abnormality of fetal growth and development
• decreased placental reserve caused by insult
• mothers who smoke during pregnancy have small palcentas

Question 5

what does the fetus use as its major energy source?

Answer 5

glucose

Question 6

glucocorticoids do what to fetal liver

Answer 6

promote storage of glucose as glycogen

Question 7

Insulin on fetal growth

Answer 7

causes glucose to be stored as glycogen,
uptake of aa’s
-lipogenesis

Question 8

GH (postnatally)

Answer 8

binds GH receptors on liver causes production of somatomedin or IGF-1
-minimal effect on fetal growth bc fetal liver has few GH receptors

Question 9

IGF-1 and IGF-2

Answer 9

mitogenic peptides, important for fetal growth

amt correlates with birth weight

Question 10

thyroid hormones and fetal growth

Answer 10

most T4 in fetus is maternal (before second trimester)

• fetal TSH and T4 begin to increase in 2nd trimester
• hypothyroidism has adverse effects on fetal growth

Question 11

when does the fetal heart begin to beat at how fast

Answer 11

• 4th week after fertilization

- 65 bpm, goes to 140 bpm just before birth

Question 12

when do nucleated RBCs form in fetus and where

Answer 12

3rd week, yolk sac and mesothelium of placenta

Question 13

when do non-nucleated RBCs form and where

Answer 13

4th-5th weeks, by fetal mesenchymal and endothelial cells of fetal blood vessels

Question 14

what takes over blood cell formation at 6 weeks

Answer 14

liver

Question 15

at 12 weeks the ___ and ___ start forming RBCs

Answer 15

spleen and lymphoid tissue

Question 16

from 3rd month on _____ becomes principal source of RBCs

Answer 16

bone marrow

Question 17

fetal erythrocytes and reticulocytes

Answer 17

fraction of erythrocytes that are reticulocytes is high in young fetus but decreases at term
-fetal erythrocytes live 80 days as compared to adult being 120

Question 18

development of NS

Answer 18

by 3rd and 4th month after pregnacny most reflexes present

-cerebral cortex development continues after birth

Question 19

fetal metabolism and iron

Answer 19

by week 12 gestation iron accumulates rapidly and 1/3 is stored in liver, available to use for Hb for months after birth

Question 20

development of kidneys: when does urine excretion begin

Answer 20

2nd trimester and accounts for 70-80% of amniotic fluid

-renal control stystems don’t fully develop until few months after birth

Question 21

what stimulates breathing at birth

Answer 21

• asphyxiation during birth

- sudden drop in ambient temp and cooling of skin

Question 22

what can cause delayed breathing at birth

Answer 22

use of general anesthesia during delivery
prolonged labor
head trauma of infant during birth: depressed respiratory center

Question 23

causes of hypoxia during delivery

Answer 23

CAPE

compression of umbillical cord, anesthesia (excessive, which depresses oxygen of even her blood), premature separation of placenta, excessive uterine contractions

Question 24

how much negative inspiratory pressure is needed to overcome surface tension and open alveoli for 1st time

Answer 24

over 25mmHg

• air in lungs remains almost exactly zero until negative pressure reaches -40
• once gets to -60 then 40 mL of air comes into lungs

Question 25

how much positive pressure does it take to deflate lungs on first breath

Answer 25

+40

Question 26

is more or less effort required after first breath and when does breathing become completely normal

Answer 26

less, after 40 minutes

Question 27

surfacant fnct and made by what

Answer 27

secreted by type II alveolar epithelial cells - mainly phospholipid (phosphatidylcholine) - syn begin last trimester - harder to close aveoli with surfacant once open

Question 28

Respiratory distress syndrome common in what and due to what

Answer 28

common in premature infants and infants born to diabetic mothers -failure to secrete adequate amounts of surfactant resulting in collapsed alveoli and develop of pulmonary edem

Question 29

4 unique shunts of fetal circulation

Answer 29

placenta ductus venosus foramen ovale ductus arteriosus

Question 30

placenta shunt

Answer 30

shunts blood away from lower trunk and lowers effective blood flow to all abdominal viscera including kidneys

Question 31

blood from the umbilical vein returns ___ blood back to fetus from placenta and enters ___

Answer 31

oxygenated, ductus venosus

Question 32

ductus venosus blood flow

Answer 32

blood from umbilical vein to the IVC, bypassing the liver

Question 33

foramen ovale | -right to left shunt

Answer 33

blood goes from right atria to left atria | -of 69% combined CO that enters RA through IVC, 27% shunts into LA

Question 34

formaen ovale blood that isn't shunted to LA

Answer 34

rest of combined cardiac output that enters RA from IVC joins poor oxygenated blood from SVC and coronary vessels - none of this shunts to LA - instead goes through tricuspid to RV so PO2 here is lower than in LV - blood from right ventricle then enters trunk of pulmonary artery

Question 35

ductus arteriosus

Answer 35

directs blood from pulmonary artery to the aorta - contains SM in vessel wall - pateny of vessel is due to active relaxation of SM from PGE2

Question 36

at birth there is a ____ pulmonary and ___ systemic vascular resistance

Answer 36

decreased pulm: due to lung expansion, vasodilation from prostaglandins increased systemic: loss of blood flow from placenta increases this -increases pressure in aorta, LA, and LV

Question 37

what causes the foramen ovale to close

Answer 37

reversal of pressure gradient pushes valve on left side shut on septum which eventually seals -due to increased venouse return to LA and elevated LA pressure

Question 38

ductus arteriosus closing

Answer 38

now aortic pressure excedes pulmonary a pressure so blood flow reverses from aorta to pulmonary a - high oxygen content from aorta causes vasoconstriction of DA - also falling levels of prostaglandins cause closure

Question 39

patent ductus arteriosus

Answer 39

ductus arteriosus remains open which allows O2 rich blood from aorta to mix with O2 poor blood in pulmonary a -strain on heart and increase BP in lung arteries

Question 40

ductus venosus closing

Answer 40

after birth blood flow through umbilical vein stops but portal blood flow still goes through - muscle wall of ductus venosus contracts strongly and closes - increase in portal venous pressure forces venous blood flow through liver sinuses

Question 41

``` neonate: HR BP RR metab ```

Answer 41

HR: 100-150 bpm (even higher in prematures) BP: 70/50 first day, 90/60 few months, 115/70 adolescence RR: 40 metab: 2X adult

Question 42

special feature of kidney neonate

Answer 42

- high fluid tunrover - rapid acid formation, only concentrates urine/plasma 1.5X compared to 3-4X of adult - problems with acidosis and dehydration

Question 43

neonate phys and body temp

Answer 43

body temp falls easily

Question 44

nutritional needs neonate

Answer 44

- calcium and vitamin D: bone ossification - iron: for RBCs, withou = anemia - vitamin C: not stored in enough quantitiy in fetal tissue - can be provided in breast milk