Fetal Circulation Ans

Question 1

Describe the basics of respiration

Answer 1

O2 diffuses through the villi wall and binds to fetal haemoglobin
Transfer increased as fetal haemoglobin as higher affinity for O2

Question 2

Describe the features of fetal circulation

Answer 2

Before birth, lungs are filled with fluid and play no role in gaseous exchange
The GI tract and kidneys do not function so blood flow is diverted to meet prenatal requirements

Question 3

Discuss features of fetal circulation relating to blood flow

Answer 3

3 shunts to direct oxygenated blood to most essential areas, ductus venosus, foremen ovals, ductus arteriosus

Question 4

Describe the ductus venosus

Answer 4

Continuation of the umbilical vein
Blood comes into baby from umbilical vein then shunts a portion of it to the inferior vena cava so blood bypass the liver

Question 5

Describe the foramen ovale

Answer 5

Opening in septum between the two atria
Covered with a flap of tissue acting as a one way valve
Allows blood to flow between right and left atria to bypass the lungs

Question 6

Describe the ductus arteriosus

Answer 6

Connects the pulmonary artery to the descending thoracic arch
Diverts blood so very little blood asses the lungs

Question 7

Describe the fetal circulation

Answer 7

Umbilical vein carries oxygenated blood through the ductus venosus into the right atrium through the inferior vena cava. The blood then passes through the foramen ovale

Question 8

Describe the adaptation to extrauterine life in the lungs

Answer 8

Just before and during labour, lung fluid production is reduced
During pushing down, chest is squeezed which brings up fluid from trachea

Question 9

Describe the stimuli which initiate breathing

Answer 9

Thermal- cold environment
Tactile- rubbing
Chemical- serum cortisol, anti diuretic hormone and catecholamines increase

Question 10

Describe how the first breath helps with adaptation to extra uterine life

Answer 10

Lungs inflate and this increases the thoracic pressure causing the fluid in the lungs to be absorbed into the bloodstream
The introduction of air increases arterial tension so pulmonary artery blood flow increases and pulmonary resistance falls

Question 11

Describe how the umbilical cord helps with adaptation to extrauterine life

Answer 11

When umbilical cord is clamped, there is a loss of resistance in placental circulation
Resulting in increase peripheral vascular resistance and an increased systemic blood pressure
Wharton’s jelly constricts when temp falls, thus clamping cord naturally

Question 12

Describe how the foramen ovale closes

Answer 12

Left atrial pressure becomes higher than the right atrial pressure

Question 13

Describe how the ductus ateriosus closes

Answer 13

Blood entering right atrium is now diverted to the right ventricle and into pulmonary circulation through the pulmonary veins so as pulmonary circulation is established this closes the ductus arteriosus

Question 14

Describe the changes to the foramen ovale, ductus arteriosus, ductus venosus and umbilical arteries

Answer 14

Foramen ovale- fossa ovalis
Ductus arteriosus- ligamentum arteriosum
Ductus venosus- ligamentum teres
Umbilical arteries- medial umbilical ligaments