FETAL CIRCULATION:

MR. ABDOU PANNEH(RM,FWACN,DHAF, NT,

RN)

INTRODUCTION• The fetus usually develops it own blood

circulation• At no given time does the fetal and maternal

blood mix except for some pathological reason• The fetus produces its own white and red blood

cells• The fetal respiratory and gastro intestinal tract

system are non functional in-utero.• The placenta is the sole supplier of oxygen and

nutrients through the umbilical vein.

TEMPORAL STRUCTURES• DUCTUS VENOSUS: (from a vein to a vein). This

vessel originates from the umbilical cord to the inferior vena cava. It carries replenished and oxygenated blood from the placenta to the fetal heart.

• FORAMEN OVALE: This is an opening between the two atria of the fetal heart. It allows replenished and oxygenated blood to enter the left atrium thereby bypassing the right ventricle.

TEMPORAL STRUCTURES cont’d• DUCTUS ARTERIOSUS: (from an artery to an artery).

This vessel branches from the pulmonary artery to the descending arch of the aorta. It carries unreplenish and deoxygenated blood from the upper limbs and head, thereby bypassing the pulmonary circuit.

• HYPOGASTRIC ARTERIES: These are two vessels that branches from the internal iliac arteries to enter the umbilical cord where they become known as the umbilical arteries. They return deoxygenated and unreplenish blood to the placenta for oxygenation and replenishment.

BARRIERS (LAYERS) BETWEEN FETUS & MOTHER

• The syncytium• The langahan’s• The mesoderm• The capillary wall

PHYSIOLOGY OF FETAL CIRCULATION• Carbon dioxide and excretory products are given off

into the maternal blood while the nutritional substances and oxygen are picked up into fetal circulation/blood. The replenished and oxygenated blood now returns to the fetus through the umbilical vein in the umbilical cord. The blood is led directly to the liver but before reaching the liver, the ductus venosus shunt it and directs the blood into the inferior vena cava, which is at the same time returning deoxygenated blood from the lower extremities. At this point, there is a mixture of oxygenated and deoxygenated bloods.

CONT’D Between the two atria, the foramen ovale allows

oxygenated blood from the inferior vena cava to pass from the right atrium to the left, instead of down to the right ventricle as in adult. The blood then passes from the left atrium to the left ventricle where it is pumped into the aorta. A major portion goes to supply the head and upper limbs, while the small portion supplies the lower part.

CONT’D• The deoxygenated blood from the upper limbs and head

returns to the right atrium via the superior vena cava and passes down to the right ventricle as in adult.

• From the right ventricle, the blood instead of going to the lungs, it is directed by the ductus arteriosus to empty into the descending arch of the aorta as the lungs are non functional. Although a little amount og blood goes to the lungs to maintain their survival. The descending aorta supplies the lower aspect but a large portion is diverted to the placenta by the hypogastric arteries for oxygenation and replenishment for the cycle to continue.

CONT’D At birth, the cry of the baby enables air to be

inhaled. This fills and expands the lungs. All temporal structures also get closed.

WHAT TECHNIQUES WOULD YOU USE TO STIMULATE A BABY TO CRY????????????????????????

ADAPTATION TO EXTRA-UTERINE LIFE• As breathing commence soon after birth, normal

blood circulation begins resulting in an increase pressure on the left side of the heart unlike in utero. This results in the closure of a flap over the foramen ovale, preventing direct flow of blood from the right atrium to the left.

• With the establishment of pulmonary respiration the oxygen concentration in the bloodstream rises. This cause the ductus arteriosus to constrict and close.

CONT’D• The cessation of the placental circulation results

in the collapse of the umbilical vein, the ductus venosus and the hypogastric arteries.

• These immediate changes are functional and those related to the heart are reversible in certain circumstances. Later they becomes permanent and anatomical.

CONT’D

• The umbilical vein becomes ligamentum teres, the ductus venosus the ligamentum venosum and the ductus arteriosus the ligamentum arteriosum. The foramen ovale becomes the fossa ovalis and the hypogastric arteries are known as the obliterated hypogastric arteries except for the first few centimeters, which remain open as the superior vesical arteries.

QUESTIONS, CONTRIBUTIONS, CLARIFICATIONS & CONSTRUCTIVE CRITICISMS?????