Y2 fetal physiology

Question 1

O2 + glucose=?

Answer 1

= Energy+ Co2+ H2O

Question 2

The placenta acts like a ?

Answer 2

Lung

Question 3

How does oxygen travel from maternal circulation to fetal?

Answer 3

Due to saturation of O2 in fetal blood being lower following the fetus having higher amount of Hb and their haemoglobin is better at binding O2.. More O2/Hb and more Hb creates a higher “suction” of O2 in the fetus and so the gas exchange in the placenta occurs.

Question 4

What is aerobic metabolism?

Answer 4

It is the process of O2 and glucose in the fetal tissues are consumed to produce energy with CO2 and H2O as waste products. The O2 is used to metabolise the glucose.
When CO2 and H2O are reabsorbed into the bloodstream, they divide into Hydrogen ion H+ and Bicarbonate ion HCO3-. H+ is buffered in Hb, HCO3- seeps in to extracellular fluid. (in the placenta this. H+ and HCO3- returns to CO2 and H2O and is transferred into the maternal blood stream, keeping the amount of H- at a manageable level.)

Question 5

How is Ph measured

Answer 5

in the amount of H+ in the bloodstream

Question 6

How is the fetus able to survive high levels of toxic H+?

Answer 6

Their Hb is able to buffer them and store them, keeping them from entering the cells, alongside placental deloading of these into maternal bloodstream.

Question 7

A high amount of H+ give a Ph that is?

Answer 7

acidic, <7.. logarithmic scale so can escalate to toxic levels very quickly. A negative difference in a low Ph is significantly more sinister than a negative difference in a higher Ph due to the logarithmic scale.

Question 8

CO2 is carried in the blood in the form of ?

Answer 8

H+ and HCO3-, very little is in the form of pure CO2

Question 9

The amount of CO2 in the blood is often measured as

Answer 9

pCO2, partial pressure.. mmHg or KPa as units

Question 10

Fetal blood coming into the placenta has realtively

Answer 10

Low Ph, low pO2, high pCO2

Question 11

Normal gaseous exchange depends on

Answer 11

Normal perfusion of the uterus and the placental bed

Question 12

What could be examples of poor perfusion of the uterus and placenta due to maternal factors?

Answer 12

Commonly High blood pressure, less common hypoxia (during convulsion etc.)

Question 13

What could be examples of poor perfusion of the uterus and placenta due to uterine factors?

Answer 13

Contractions, chronic impairment of uteroplacental arteries (pre-eclampsia),

Question 14

What could be examples of poor perfusion of the uterus and placenta due to placental factors?

Answer 14

Placental abruption (Shortly leads to fetal demise), reduced placental circulation (pre-eclamptic conditions)

Question 15

What could be examples of poor perfusion of the uterus and placenta due to fetal factors?

Answer 15

commonly cord compression, not so common fetal bradycardia, fetal erythraemia >260 bpm, fetal anaemia (Rh- factor, parvovirus)

Question 16

poor perfusion of the uterus and placenta lead to

Answer 16

Accumulation of CO2 and reduced supply of O2

Question 17

What is respiratory acidaemia?

Answer 17

Accumulation of CO2 causing acidaemia.

When CO2 in the form of H+ and HCO3- is not removed by the placenta as quickly as it is produced, causing a low Ph. BAD.

Question 18

Acidosis

Answer 18

Low Ph in blood and tissues

Question 19

Acidaemia

Answer 19

low Ph in blood

Question 20

Which is higher, maternal pO2 or fetal pO2?

Answer 20

maternal pO2

Question 21

Is fetal cardiac output greater or smaller than an adults?

Answer 21

4x greater/kg

Question 22

hypoxaemia

Answer 22

low pO2 in blood

Question 23

hypoxia

Answer 23

low oxygen level in fetal tissues

Question 24

In which four ways does the fetus tackle with acute hypoxaemia?

Answer 24

1. preventative oxygen stores
2. increased oxygen extraction
3. Centralisation of blood flow
4. Anaerobic metabolism

Question 25

What role do the catecholamines have in the fetus?

Answer 25

To induce preventative measures against hypoxia, levels go up during labour.

Question 26

How does the fetus cope with chronic hypoxaemia?

Answer 26

Reduce oxygen consumption through, reduction in growth (IUGR), and more acutely reduction in movement.
O2 usage is optimised through, increased levels of Hb and O2 extraction.
O2 redirected to brain, heart and adrenals, leaving less for skin gut and kidneys (leading to nec, oligohydramnios and asymmetrical growth.

Question 27

Polycythaemia

Answer 27

raised levels of haemoglobin Hb in the blood

Question 28

chronic hypoxaemia can lead to?

Answer 28

IUGR, reduced movements, polycythaemia, nec, oligohydramnios and asymmetrical growth

Question 29

Anaerobic metabolism

Answer 29

process of cells producing energy without O2 with lactic acid as a biproduct. glycogen> glucose= energy and lactic acid (lactate plus H+). Glycogen stores are used up leading to low sugar levels/ hypoglycaemia in the new born.

Question 30

Glycogen

Answer 30

long term store of carbohydrate, stored in myocardium and liver, need to be changed into glucose to be used.

Question 31

metabolic acidaemia

Answer 31

fall in Ph due to accumulation of lactic acid

Question 32

accumulation in CO2 leads to

Answer 32

respiratory acidaemia

Question 33

accumulation in lactic acid leads to

Answer 33

metabolic acidaemia

Question 34

What does the base deficit tell us?

Answer 34

How much of the buffers that are used up, high base deficit means metabolic acidaemia rather than respiratory. as most of this buffer has been used up.

Question 35

Base deficit

Answer 35

The amount of base/alkali that would have to be added to restore blood/ECF Ph to normal. Calculated from Ph and CO2. Measured in mmol/l. In the fetus/new born it is calculated on extracellular fluid rather than blood.

Question 36

How does the fetal blood Ph relate to maternal blood Ph?

Answer 36

fetal blood Ph correlate with maternal and usually sits around 0,1 units lower. It can therefor go up in 1st stage of labour (maternal hyperventilating) and down in 2nd stage (maternal metabolic acidaemia following strenuous muscle activity of the uterus). If the difference is larger, placental gas-exchange might be compromised.

Question 37

aerobic metabolism produces x times more energy as anaerobic metabolism

Answer 37

19 times