Lecture Eight

• An increase in size of the whole body or parts of the body • Dominates the first 20 years of life

• Increase in cell number (hyperplasia) • Increase in cell size (hypertrophy) • Increase in intercellular substances (acceleration)

-Focuses on the size attained at a given time

-The process of becoming mature or the process towards a mature biological state

• Occurs in all organs and their systems and tissues • e.g. skeletal maturity = fully ossified adult skeleton • Timing and Tempo of maturation varies between individuals

• Biological • The development of stem cells into functional cells and systems • Behavioural • The development of behavioural competence: • Motor/skill acquisition • Socially acceptable behaviours • Intellectual • Emotional

• Chronological Age = How many years old you are • Biological Age = The age of your biological maturation • Prenatal = period of growth and development prior to birth (~9 months)

• Germinal Period = fertilisation to end of germ layer formation (weeks 1 – 2 of development) • Embryonic Period = days 14-56 (weeks 3-8) after fertilisation • Developing human is called an Embryo • Foetal Period = 56 days to birth (last 30 weeks) • Developing human is called a Foetus

• The dermatome is an area of skin supplied by nerves from a single spinal root • Each spinal nerve innervates a particular known area of skin

-A group of muscles that a single nerve innervates

-Mother provides O2 and nutrients to the foetus and removes CO2 and waste products

Allows exchange to occur without mixing of the mothers and foetuses blood

Carries O2 and nutrients from the placenta to the foetus

Transports venous blood from foetus to placenta for re-oxygenation and elimination of wastes

• Foetuses lungs do not function - they are filled with fluid • The foetuses’ heart does pump blood but only 10-15% of the blood pumped by heart goes through the lungs

• Two shunts which shift blood from the right to left side of the heart thus bypassing the lungs: • Ductus Venosa – temporary vessel from umbilical vein to inferior vena cava • Allows oxygenated blood from maternal circulation to pass directly from the umbilical vein to the inferior vena cava – bypassing the live

• One way opening in the septum separating the right and left atria - Allows blood to bypass the right ventricle to go straight to the left atria - Once blood has moved through the right atrium the pressure in the left closes the valve thus preventing back flow

• Small vessel which connects the pulmonary artery to the aorta - Serves as a right to left shunt. Allows the small amount of blood pumped by the right ventricle to the lungs to be diverted to the aorta

-Metabolic link between Mother and Foetus is severed at birth -Large inflation of lungs at birth = Expansion of lungs = reduced resistance to blood flow through lungs = increased blood flow through pulmonary arteries = more blood from right atrium to right ventricle to pulmonary artery = less through the foramen ovale also -more blood returns to left atrium via pulmonary veins = increased pressure in the left atrium = closure of the foramen ovale (fossa ovalis) -Constriction of ductus arteriosus = complete permanent closure = replaced with connective tissue = ligamentum arteriosum -Cutting of the umbilical cords = no more blood flow through and the umbilical veins and arteries degrade = no blood through ductus venosus = ligamentum venosum

-Postnatal = period after birth -Infancy = first year of birth (0-1 year) oPerinatal = the first week oNeonatal = the first month oPostnatal = the remainder of the first year oChildhood = 1 year – adolescence -Early Childhood = preschool years (1 – 4 years) -Middle Childhood = elementary school years (5 years to adolescence) oAdolescence = generally between 10-18 years -Onset and termination of adolescence is highly variable -Males: 10 - 22 years -Females: 8 - 19 years -Adulthood = Age 20 to death oYoung Adult = 20-40 yrs oMiddle age = 40-65 yrs oOlder Adult = 65 yrs to death -Three generations: -65-75 -75-85 -85+

-Infancy = period of rapid growth of most systems -Childhood oEarly childhood = continued rapid growth but at a decelerating rate oMiddle childhood = steady progress

After birth, left side size grows more rapidly compared to the right

Left ventricle pumps blood against a higher pressure or resistance than the right

Size continues to grow until young adulthood • Birth = 40 cm3 • 6 months = doubled • 2 years = x 4