development of baby after birth

Umbilical cord

Contains 2 umbilical arteries and 1 umbilical vein; arteries carry deoxygenated blood from the fetus to the placenta, while the vein carries oxygenated blood from the placenta to the fetus.

Ductus venosus

A fetal shunt that connects the umbilical vein to the inferior vena cava, allowing blood to bypass the liver.

Why does the ductus venosus bypass the liver?

The mother's liver performs many metabolic and detoxification functions for the fetus, so oxygen-rich blood can be sent quickly to the heart and brain instead of passing through the fetal liver.

Foramen ovale

An opening between the right and left atria that allows blood to bypass the lungs.

Why does the foramen ovale bypass the lungs?

The fetal lungs are collapsed and do not exchange gases; oxygen comes from the placenta, so blood does not need to travel through the lungs.

Ductus arteriosus

A fetal shunt connecting the pulmonary artery to the aorta, allowing blood to bypass the lungs.

Why does the ductus arteriosus bypass the lungs?

The lungs are non-functional before birth and have high resistance to blood flow, so most blood is diverted directly into the aorta.

Inferior vena cava

Large vein that carries blood toward the heart.

Fetal circulation

The movement of blood before birth using special shunts that bypass the liver and lungs.

Placenta

Organ where oxygen, nutrients and wastes are exchanged between the mother's blood and the fetus's blood.

Why are fetal shunts needed?

The placenta performs gas exchange and many metabolic functions before birth, so blood can bypass the fetal lungs and much of the liver.

Blood flow through the fetus

Placenta → umbilical vein → ductus venosus → inferior vena cava → right atrium.

Pathway through the foramen ovale

Right atrium → foramen ovale → left atrium → left ventricle → aorta → body.

Pathway through the ductus arteriosus

Right atrium → right ventricle → pulmonary artery → ductus arteriosus → aorta → body.

What happens when the baby takes its first breath?

The lungs expand, oxygen enters the blood, and blood flow to the lungs increases dramatically.

Why does blood flow to the lungs increase after birth?

The lungs expand and pulmonary blood vessels open, decreasing resistance to blood flow.

Closure of the ductus arteriosus

Increased blood flow to the lungs reduces blood flow through the ductus arteriosus, causing it to close and become fibrous tissue.

Closure of the foramen ovale

Increased blood returning from the lungs raises pressure in the left atrium, forcing a flap shut over the opening.

What happens if the foramen ovale does not close?

The baby may have a hole in the heart, resulting in reduced oxygenation and possible blue coloration of the skin.

Closure of the ductus venosus

As the liver becomes fully functional after birth, blood is directed through the liver and the ductus venosus closes.

First breath

Usually initiated by the shock of birth, physical stimulation and rising carbon dioxide levels.

Why does clamping the umbilical cord stimulate breathing?

It stops placental gas exchange, causing CO₂ levels to increase and stimulating the respiratory centre in the brain.

Normal newborn breathing rate

Approximately 45 breaths per minute during the first two weeks of life.

Normal newborn heart rate

Approximately 125 beats per minute, but can reach 180 beats per minute.

Why do newborns require more oxygen?

Increased muscular activity and metabolism are needed to maintain body temperature.

Red blood cells (RBCs)

Increase after birth to improve oxygen transport.

White blood cells (WBCs)

Initially high after birth but decrease after about one week.

Average newborn length

Approximately 50 cm.

Average newborn weight

Approximately 3.4 kg.

Newborn muscle control

Limited muscle control with a weak neck, although some head turning is possible.

Abilities of a newborn

Breathing, sucking, swallowing, excreting waste, seeing, hearing, tasting, smelling and crying.

Grasp reflex

An object placed in a baby's palm causes the baby to automatically grip it.

Rooting reflex

Stroking a baby's cheek causes the head to turn toward the stimulus and the mouth to open.

Suckling reflex

Placing an object in the mouth causes automatic sucking.

Moro reflex (startle reflex)

Response to a loud noise, sudden movement or sensation of falling; arms extend outward then return inward.

Development during infancy

The most rapid period of growth occurs during the first five years of life.

Growth in infancy

Body length increases significantly and body weight approximately triples.

Changes in body proportions

Legs become proportionally longer while the head and face grow more slowly than the rest of the body.

Head proportion in a newborn

The head represents about one quarter of total body length.

Head proportion in an adult

The head represents about one tenth of total body length.

Growth trend during childhood

Growth is rapid during the first six years and then slows.

Growth differences between sexes

Up to age 10, boys are slightly taller on average; from 10 to 15, girls are slightly taller on average.

Adult body proportions

Reached at approximately 15 years of age.

Exam mnemonic: VOA

Venosus = bypasses liver, Ovale = atrial opening, Arteriosus = bypasses lungs.

Exam mnemonic: Why the bypasses?

Liver bypass because the mother's liver performs many functions; lung bypass because oxygen comes from the placenta rather than breathing.