Neonatal Physiology Flashcards
Describe the ductus venous and what vasculature it drains into?
bypasses the liver and drains into the inferior vena cava
continuation of the umbilical vein
Ductus arteriosus?
connects pulmonary artery with descending thoracic aorta
Relaxation of the smooth muscle layer of the ductus arteriosus is mediated by what?
PGE2
Describe where blood flow comes from to RA in neonatal system?
oxygenated (mixed) blood from IVC
deoxygenated blood from SVC
Where does the RA of the neonatal heart pump blood to?
to the LA (through the foramen ovale) mainly blood from IVC
To the RV- mainly blood from SVC
Where does the LA of neonatal heart receive blood from?
mixed blood (oxygenated and deoxygenated) from the RA (through the foramen ovale)
What chamber of the neonatal heart does the LA pump blood?
mixed blood into the LV
What are the factors/stimuli for initiation of respiration?
chemical (transitory hypoxia of fetus and neonates)
thermal
sensory and physical
mechanical
Describe the factors considered chemical stimuli (transitory hypoxia of fetus and neonates), that aid in the initiation of respiration?
Fetal factors:
Compression of umbilical cord
Changes in Maternal posture
Fall in maternal oxygenation (bearing down )
Neonatal factors:
Cessation of placental gas exchange
Cessation of umbilical cord pulsation
Cutting of the cord
Temporary asphyxia * respiratory center stimulated
How does thermal stimuli initiate respiration in the neonate?
Change in temp from intrauterine (98.6° F) to Extra uterine (70.75° F) , Excite nerve impulse in skin stimulate respiratory center
What are the sensory and physical stimuli that aid in causing the neonate to initiate respiration?
-Tactile stimuli—Touch
-Auditory –sounds- noise
-visual- Light
-respiratory center stimulated
Mechanical Stimuli
Compression of chest in birth canal
Sudden expansion (Recoil of chest wall) -ve pressure
Inspiration (mechanical suctioning)
What is the normal rate of respiration for the neonate?
30-50 breaths /min
Describe the normal breathing of a neonate.
Nature: diaphragmatic with some synchronization with chest movement
initially shallow and irregular
later ,deep & regular
Be able to map out cues (flow diagram) showing establishment of respiration for the baby.
What do the umbilical arteries form postnatally?
medial umbilical ligament
What does the umbilical vein form postnatally?
ligamentum teres (round ligament)
What structure does the ductus venosus form?
fibrous cord - ligamentum venosum
How does the ductus venosus form a fibrous cord?
Contraction of the muscle wall of the DV (within 1-3 hours after birth) and cessation of the blood flow
How does closure of the foramen ovale happen?
Opening of pulmonary circulation and cessation of the umbilical flow→ ↓ pressure in the RA
↑ pressure in the LA
Reverse pressure gradient across the FO
Functional closure of the small valve over the FO
Structural closure requires 3-9 months
Postnatally, is there a thinning of muscle layer of the pulmonary arteries?
yes there is
What is the average hr of the infant post-nasally?
Heart rate —initially 175-180 beats /min——–gradually 120-150 beats /min
Describe neonatal jaundice.
Bilirubin formed in the fetus can cross the placenta into the mother and be excreted through the liver of the mother, but immediately after birth, the only means for ridding the neonate of bilirubin is through the neonate’s own liver, which for the first week or so of life functions poorly and is incapable of conjugating significant quantities of bilirubin with glucuronic acid for excretion into the bile.
Consequently, the plasma bilirubin concentration rises from a normal value of less than 1 mg/dl to an average of 5 mg/dl during the first 3 days of life and then gradually falls back to normal as the liver becomes functional.
When the baby’s initial plasma bibirubin concentration rises from a normal value to higher during the first 3 days of life and gradually falls back, what is this called?
physiologic hyper-bilirubinemia
Know the difference in reactions of the neonate in response to hypothermia and hyperthermia.
What is the immature liver of the neonate typically deficient in?
ü Glucoronyl enzyme - Physiological jaundice
ü Prothrombin and coagulation factors - bleeding tendency
ü Glycogen stores - hypoglycemia
Why are neonates susceptible to dehydration, acidosis and electrolyte imbalance?
inability to concentrate urine
When does the fetus synthesize immunoglobulins? Describe where the immunoglobulins are before then?
Fetus synthesize Immunoglobins—20th week of gestation (IgM, IgG, IgE)
IgG cross placenta
IgM does not cross placenta
IgA secrete in colostrums of mother
Describe the sensory adaptations of the eyes for the infant.
structurally incomplete, ciliary muscles immature - Poor accommodation & fixation (Hypermetropia in first month)
Describe the sensory adaptation of the tear glands for the newborn.
not active till 2-4 weeks of life
Describe the sensory adaptations of hearing for the newborn.
startle reflex, crying
Low frequency voice, cry
can identify mother’s voice by 3rd day of life
Describe the sensory adaptation of smell for the newborn.
reacts to strong smell
Describe the sensory adaptation of taste for the newborn.
can distinguish taste
Describe the sensory adaptation of touch for the newborn.
can perceive touch all over the body, responds to patting, rubbing
