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Physiology & Science: Human Growth > Adaptation At Birth II > Flashcards

Adaptation At Birth II Flashcards

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1
Q

How does gas, nutrient and waste exchange occur within the baby, in terms of the circulation? (Use names of arteries)

A
  • Umbilical arteries come to mother with deoxygenated blood
  • Pick up oxygen from uterine artery (high O2/nutrients)
  • Blood arrives to foetus via umbilical vein
  • Then progresses to the foetal heart
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2
Q

What is the purpose of placental villi?

A

Increase SA for diffusion

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3
Q

What are the 2 forms as to how Oxygen is carried in the blood?

A
  1. Dissolved in plasma + RBC water (2%)
  2. Reversibly bound to haemoglobin (98%)
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4
Q

What is the structure of adult haemoglobin?

A
  • 2 alpha chains
  • 2 beta chains
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5
Q

Foetal haemoglobin has high alpha-globin and some beta-globin, there are also similar chains to these. What is the main beta-globin equivalent in the foetus?

A
  • Gamma - continues to be main one until 6 months old
  • Other beta-equivalent chain is epsilon
  • Other alpha-equivalent chain is zeta
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6
Q

So, what is the structure of foetal haemoglobin?

A
  • 2 alpha chains
  • 2 gamma chains
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7
Q

How is foetal haemoglobin functionally different to adult haemoglobin and why is this?

A
  • HbF binds oxygen with greater affinity than HbA
  • So at a lower level of oxygen the HbF is better saturated than HbA
  • Allows oxygen to be transferred from mother to baby across placenta (like a leach)
  • This is caused by a single amino acid change
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8
Q

What is 2,3-Diphosphoglycerate?

A
  • Side product of glycolysis
  • 2,3-DPG binds to deoxygenated Hb with greater affinity than oxygenated Hb
  • Promotes release of Oxygen
  • Pushes Hb curve to the right (as does acidity + high temp)
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9
Q

How does 2,3-DPG help the foetus?

A
  • 2,3-DPG does not bind to HbF as effectively as it binds to HbA
  • So HbF binds Oxygen with greater affinity than to HbA
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10
Q

50-60% of the blood from the umbilical vein (oxygenated) goes to the IVC. Where does the rest go?

A

Remaining 40-50% goes straight to the liver as it is very metabolically active

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11
Q

What is the pathway of the oxygenated blood (50-60%) that reaches the IVC in the foetus?

A
  • from umbilical vein -> via ductus venosus
  • to the inferior vena cava
  • to the right atrium
  • blood from legs also joins IVC to right atrium
  • junction between IVC + R atrium = Eustachian valve
  • this oxygenated blood goes from R atrium to L atrium
  • via foramen ovale
  • then down to left ventricle -> up to aorta
  • then to coronary arteries -> then arteries supplying head + neck
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12
Q

What does the Eustachian valve do?

A

Helps to direct the flow of oxygen-rich blood through the right atrium into the left atrium and away from the right ventricle.

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13
Q

Where does the deoxygenated blood from the SVC go?

A
  • Down into right ventricle
  • Then up to pulmonary artery
  • But instead of going to lungs, goes into next shunt - ductus arteriosus
  • To join aorta
  • This is bc lungs aren’t doing their job atm
  • Pulmonary circulation resistance is very high so this helps to guide blood into systemic circulation/aorta via the less resistant ductus arteriosus
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14
Q

What do the umbilical arteries supply?

A

Supply the buttocks + lower extremeties via the lateral part of the internal iliac arteries.

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15
Q

What happens upon birth?

A
  • Placental circulation ceases
  • Umbilical vessels constrict - stretch + rise in oxygen tension
  • Shunts close
    • Flow through ductus venosus falls
    • Fall in venous return through IVC
    • Closes over 3-10 days
  • Baby takes big breath, lungs expand
  • Expansion pulls blood vessels open + pulm vessels dilate
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16
Q

How does pulmonary vascular resistance fall?

A
  • Lung expansion
  • Pulmonary stretch receptors
  • Increased oxygen tension
  • Pulmonary vessels dilate
  • 8-10x rise in blood flow
17
Q

How and when does the foramen ovale close?

A
  • Fall in pulmonary vasc resistance -> rise in venous return to left atrium
  • RA and LA pressures equalise
  • Flap of foramen ovale pushed against atrial septum
  • Closes within mins-hours of birth
18
Q

How and when does the ductus arteriosus close?

A
  • Fall in pulmonary vasc resistance leads to bidirectional flow in ductus arteriosus
  • Closes due to oxygen rise
  • in 96 hours
19
Q

Transition from the pre-natal circulation state may not be permanent as pulmonary arterioles are very reactive and can begin to constrict again to certain stimuli. What are these stimuli and what do they lead to?

A
  • Stimuli:
    • Hypoxia
    • Hypercarbia
    • Acidosis
    • Cold

Rise in PVR and right-left shunting: at risk of foetal circulation

20
Q

What is the trigger for the ductus arteriosus to close?

A

High oxygen level

21
Q

Patent ductus arteriosus (PDA) is a condition wherein the ductus arteriosus fails to close after birth. Who is PDA common in?

A
  • Premature babies
  • Babies w/ respiratory distress
  • Down syndrome
  • Rubella
  • Congenital heart disease
22
Q

What does the murmur for patent ductus arteriosus sound like?

A

continuous “machine-like”

23
Q

What will babies present with if they’re developing heart failure as a result of patent ductus arteriosus?

A
  • Fast breathing
  • Increased work of breathing
  • Sweating during feeding
  • Poor feeding
  • Poor growth
  • Rapid pulse
  • Bounding pulse
24
Q

What is the treatment for patent ductus arteriosus?

A
  • Drugs - indomethacin, ibuprofen
  • Surgery
25
Q

What is the most common congenital cardiac malformation in adults?

A

Atrial septal defects

26
Q

What is an atrial septal defect (ASD)?

A
  • Left to right atrial shunt
  • Due to high compliance of right atrium + diff in pressure
  • This causes right side of heart to work harder
  • Pulmonary circulation pressure is increased
27
Q

ASD: A person with no other heart defect or small defect may not have symptoms, or they may occur in older age, what are the symptoms?

A
  • Difficulty breathing (dyspnoea)
  • Freq respiratory infections in children
  • Feeling the heart beat (palpitations) in adults
  • Shortness of breath with activity
28
Q

Some people with ASD may have other congenital heart conditions, such as what?

A

Leaky valve or a hole in another area of the heart

29
Q

What are the 4 types of congenital heart defects that you need to know of?

A
  • Atrial septal defects
  • Patent ductus arteriosus
  • Ventricular septal defects
  • Atrioventricular septal defects
30
Q

Why are neonates at a higher risk of heat loss?

A
  • 2.5-3 times higher surface area to volume ratio
  • Less insulation due to less subc fat
  • Reduced ability to generate heat
31
Q

What is the role of brown fat in thermogenesis?

A
  • Source of heat energy production: uncouples the electron transport. Instead of making ATP, it makes heat energy
    • Non-shivering thermogenesis
    • Highly vascular
    • Sympathetic innervation
    • High mitochondrial content
    • Can double heat production
32
Q

What is the normal body temperature range and what effect does hypothermia have on the baby?

A

Normothermic = 36.5 -> 37.5 oC.

Mild hypothermia = 1.8x higher risk of death
…
Very severe hypothermia = <33.9 oC = 25x higher risk of death

33
Q

Apart from death what are other harmful side effects of cold stress?

A
  • Hypoglycaemia
  • Respiratory distress
  • Hypoxia
  • Metabolic acidosis
  • Coagulation defects
  • Acute renal failure
  • Necrotizing enterocolitis
  • Weight loss
34
Q

What is the thermoneutral zone?

A

The environment which minimises the energy required to maintain core temperature

Thermoneutral range varies with age and dress.

35
Q

What are the 4 mechanisms of heat loss?

A
  • Convection
  • Radiation
  • Conduction
  • Evaporation
36
Q

Describe changes occuring in body fluid compartments over age

A
  • Total body water decreases
  • Muscle mass increases
  • Fat increases (then decreases after 1 year of age)
37
Q

What are the 4 main routes of fluid loss?

A
  • Kidneys
  • Respiratory tract
  • Skin
  • Stool
38
Q

How are the kidneys functionally immature at birth?

A
  • Don’t have all nephrons
  • Reduced GFR
  • Limited concentrating ability

Physiology & Science: Human Growth (9 decks)

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