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Scientific Basis of Midwifery > Foetal Circulation > Flashcards

Foetal Circulation Flashcards

1
Q

How is the cardiac output distributed?

A
  • Heart - 5%
  • Skeleton - 5%
  • Brain - 15%
  • Muscle - 15%
  • Kidneys - 20%
  • Body to Heart - 64%
  • Lungs - 100%
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2
Q

What is required for effective CVS function?

A
  • Cardiogenesis
  • Blood volume and BP
  • Non-severed blood vessels
  • RBC mass and fluidity
  • Myocardial contractions
  • Vascular resistance
  • Tissue metabolism
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3
Q

What is the paediatrician circulating blood volume?

A
  • Neonate = 85ml/kg
  • Infant = 80ml/kg
  • Child = 70ml/kg
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4
Q

Give an overview of cardiogenesis

A

Day 15-16 = cardiogenic mesoderm receives signal
Day 17 = Induction of angiogenesis in yolk sac
Day 18-19 = endocardial tubes
Day 21 = single cardiac tube
Day 22 = heart beats
Day 24 = cardiac looping
Day 26 - week 8 = atrial separation
Day 35 - week 8 = ventricular separation
Weeks 4-7 = great vessels and vascular network
Week 16 = conduction pathway complete

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5
Q

What is angiogenesis?

A

Formation of blood vessels

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6
Q

Describe foetal circulation

A
  • Systemic only (no pulmonary circuit)
  • Depends on placenta for oxygen, nutrients and excretion
  • In utero, pulmonary vascular resistance > systemic VR causes blood from right side of heart to bypass the lung through ductus arteriosus and foramen ovale
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7
Q

Why does foetal Hb have a higher affinity for oxygen?

A

They do not breathe so all of their oxygen is supplied in the blood from the placenta

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8
Q

Give 5 characteristics of foetal circulation

A
  1. Single parallel circulation
  2. Communications between right and left side
  3. Pulmonary circulation is redundant
  4. Well-oxygenated blood delivered to the brain, myocardium and upper body
  5. Less-oxygenated blood delivered to lower parts of body and then back to placental site
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9
Q

What is a foetal shunt and what are the 3 main ones?

A

A structure that allows blood to bypass the lungs

  1. Foramen ovale
  2. Ductus arteriosus
  3. Ductus venosus
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10
Q

Describe the foramen ovale

A
  • Opening between left and right atria
  • Closes when there is an increased volume of blood in left atrium
  • Closes shortly after birth because there is a back-flow of blood when the cord is clamped, so the hole closes due to an increase in blood volume in the left atrium
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11
Q

Describe the ductus arteriosus

A

Right to left shunting of blood from pulmonary artery to the aorta, bypassing the lungs

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12
Q

Describe the first stage of the foetal circulation route

A
  • Oxygenated blood travels from the umbilical vein to the inferior vena cava
  • This vein divides into 2 branches; some blood flows into branch which joins the hepatic portal vein and enters the liver, but most flows in second branch called ductus venosus which drains into the inferior vena cava
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13
Q

Describe the second stage of the foetal circulation route

A
  • Deoxygenated blood returning from lower limbs to the right atrium mixes with oxygenated blood from ductus venosus in inferior vena cava
  • Deoxygenated blood returning from upper body enters right atrium via superior vena cava
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14
Q

Describe the third stage of the foetal circulation route

A
  • Most mixed blood in right atrium enter left atrium through the foramen ovale
  • Minimal blood enters right ventricle which flows through the pulmonary artery
  • Small amount trickles into foetal lungs
  • The rest crosses the ductus arteriosus to join the blood in the ascending aorta; this travels to the upper body
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15
Q

Describe the fourth stage of the foetal circulation route

A
  • Blood in left atrium flows into left ventricle to flow into ascending aorta
  • Joins blood coming through ductus arteriosus and subsequently into descending aorta and to lower limbs
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16
Q

Describe the fifth stage of the foetal circulation route

A
  • Deoxygenated blood returns from the lower limbs of the foetus via the internal iliac arteries
  • Drains into hypogastric arteries and finally into umbilical arteries back to placenta for re-oxygenation
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17
Q

Give some of the main postnatal adaptations

A
  • Changes in blood flow and pressure
  • Closure of foramen ovale and ductus arteriosus
  • Establishment of neonatal circulation
  • Right ventricular output = left ventricular output
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18
Q

What do BB and AB stand for?

A 
BB = before birth
AB = after birth
19
Q

How does the umbilical vein change?

A

BB - brings oxygenated arterial blood to liver and heart

AB - obliterates; becomes round ligament of liver

20
Q

How do the umbilical arteries change?

A

BB - bring deoxygenated arteriovenous blood to placenta

AB - obliterated; become vesicle ligaments on anterior abdominal wall

21
Q

How does the ductus venosus change?

A

BB - shunts arterial blood into inferior vena cava

AB - obliterated; becomes ligamentum venosum

22
Q

How does the ductus arteriosus change?

A

BB - shunts arterial and some venous blood from pulmonary artery to aorta
AB - obliterated; becomes ligamentum arteriosum

23
Q

How does the foramen ovale change?

A

BB - connects right and left atria

AB - obliterated (usually); if it stays open = heart defect

24
Q

How do the lungs change?

A

BB - contain no air and very little blood

AB - filled with air and well supplied with blood

25
Q

How does the aorta change?

A

BB - receives blood from both ventricles

AB - receives blood from left ventricle only

26
Q

How does the inferior vena cava change?

A

BB - brings venous blood from body and arterial blood from placenta
AB - brings venous blood only to right atrium

27
Q

Give 3 other things that change in foetal circulation when baby is born

A
  1. Loss of placenta
  2. Opening of pulmonary arteries
  3. Reduced myocardial mass
28
Q

Name some things that may stimulate the baby to take its first breath

A

Effects of:

  • Lung fluid elimination
  • Hypercapnia (high levels of carbon dioxide)
  • Hypoxia
  • Cold air
  • Noise
  • Tactile stimuli
29
Q

Describe the process of the first breath

A
  • Central neuronal response
  • Deep pulmonary ventilation
  • Surfactant prevents surface tension in lungs
  • First alveolar expansion
  • Lowering of surface tension
  • Alveolar ventilation and perfusion
30
Q

What are the effects of the initial breathing?

A
  • Decrease in PVR (pulmonary ventilation rate)
  • Increase in oxygen concentration
  • Dilates patent blood vessels
  • Opens unused blood vessels
  • Neonate must establish and maintain extra-uterine life
31
Q

What is survival dependent on?

A
  • Successful adaptation
  • Safe, effective care
  • Absence of gross congenital abnormalities
32
Q

Give 4 reasons for increased risk of morbidity

A
  • Traumatic delivery
  • Birth asphyxia
  • Major pathology (disease)
  • Prematurity
33
Q

What changes should occur in the 1st week of life?

A
  • Stabilisation of body temperature
  • Successful bottle/ breast feeding
  • Bladder and bowel action
  • Haematopoiesis (liver and spleen 6 wks to 6 mths, bone marrow 6 mths)
34
Q

What changes should occur by the end of the 1st month of life?

A
  • Immune response
  • Neuroendocrine function
  • Neonatal circulation
35
Q

Describe glucoregulation

A
  • Glycogen stores
  • Gluconeogenesis
  • Ketogenesis (formation of ketones)
  • Calories from feeding
  • Warmth
36
Q

Describe the metabolic adaptations that occur

A
  • Energy crunch
  • Immediate life tasks
  • Increase adrenaline, noradrenaline and glucagon
  • Glycogen stores exhausted in 2-3 hours
37
Q

Describe thermoregulation

A
  • Immature hypothalamus
  • Large SA:Vol ratio
  • Thin body shell
  • Brown fat thermogenesis
  • Initially liable (easily changes) but gradually settles
38
Q

How does the hepatobiliary system change?

A
  • Breakdown of foetal Hb
  • Physiological jaundice resolved by 10 days
  • Vitamin K prophylaxis (treatment to prevent disease)
39
Q

How is jaundice caused?

A

When there is too much bilirubin in the blood

40
Q

How does the respiratory system change?

A
  • Upper airways different
  • Shorter, smaller airways
  • Rib cage different; less ossified
  • Reduced respiratory muscle mass
  • Limited muscle endurance
  • Smaller alveolar SA
41
Q

How does the nervous system change?

A
  • Glucose and oxygen requirement increases
  • Less rigid cranium
  • Delicate brain cells and blood vessels
  • Immature cerebral cortex, vital centres, blood-brain barrier
42
Q

How does the urinary system change?

A
  • Pass urine within 24 hours
  • Renal structure maturation
  • Passage of dilute urine
  • Adult shaped bladder at 6 yrs of age
  • Endocrine maturity at 4 yrs of age
43
Q

How does the immune system change?

A
  • Maternal antibodies in infancy
  • Skin and bowel colonisation in 1st week of life
  • Integration of whole system at 1 year
  • Full antibody complement for bacterial infection at 2 yrs of age

Scientific Basis of Midwifery (22 decks)

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