Lecture Eight

Question 1

What is Growth?

Answer 1

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

Question 2

How does growth occur?

Answer 2

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

Question 3

What does growth focus on?

Answer 3

-Focuses on the size attained at a given time

Question 4

What is Maturation?

Answer 4

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

Question 5

Where does it occur and what varies between individuals?

Answer 5

• 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

Question 6

What are the developmental contexts?

Answer 6

• 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

Question 7

What is the definition of Chronological Age, Biological Age & Prenatal?

Answer 7

• 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)

Question 8

Define Germinal, Embryonic, & Foetal Periods

Answer 8

• 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

Question 9

What are the Dermatomes?

Answer 9

• 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

Question 10

What are the Myotomes?

Answer 10

-A group of muscles that a single nerve innervates

Question 11

What does the mother provide and remove to the baby?

Answer 11

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

Question 12

Function of the Placenta?

Answer 12

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

Question 13

Function of the Umbilical Vein?

Answer 13

Carries O2 and nutrients from the placenta to the foetus

Question 14

Function of the Umbilical Arteries?

Answer 14

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

Question 15

What are the foetuses lungs are heart doing while in the womb?

Answer 15

• 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

Question 16

How does blood get from one side of the heart to the other in the foetus? What is the Ductus Venosa and its function?

Answer 16

• 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

Question 17

What is the Foramen Ovale and its function?

Answer 17

1. 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

Question 18

What is the Ductus Arteriosus and its function ?

Answer 18

2. 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

Question 19

What are the circulatory changes after birth?

Answer 19

-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

Question 20

What are the age groups?

Answer 20

-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+

Question 21

What is Infancy & Childhood?

Answer 21

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

Question 22

After birth what happens to the heart?

Answer 22

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

Question 23

Why does the left side of the heart grow more rapidly than the right side?

Answer 23

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

Question 24

Describe the hearts size from birth to 2years

Answer 24

Size continues to grow until young adulthood

• Birth = 40 cm3
• 6 months = doubled
• 2 years = x 4

Question 25

How does Heart Rate change after birth?

Answer 25

-Recall HR = rate at which the heart contracts per minute (bpm) -Foetal HR begins week 4, prenatal oHR is rapid -Labour contractions can cause a foetal HR of 200 bpm -Newborn HR = 140 ± 20 bpm oNewborn crying HR can reach 170 bpm -Over a year HR will decline by ~40 bpm -6 years HR = ~80 bpm -10 years HR = ~70 bpm

Question 26

Why do infants & children have higher HR's compared to adults?

Answer 26

oSmaller amount of blood volume -Still requires blood to reach large surface area oMyocardium is less contractile / heart produces less forceful contractions -Due to heart not fully developed -All these factors contribute to a small SV therefore higher HR is required to maintain cardiac output (CO)

Question 27

Why does HR decline as the child grows?

Answer 27

As the heart grows and as blood volume increases the SV increases therefore HR can decrease to maintain CO

Question 28

How is stroke volume affected

Answer 28

- Heart size - Contractile force - Vascular resistance (vasodilation/vasoconstriction) to blood flow - Venous return - rate at which blood is returned to the right side of the heart - Infants are not bipedal = limited venous muscular pump

Question 29

Why is stroke volume lower in infants/children?

Answer 29

Due to smaller heart size and blood volume - Birth SV = 3-4 ml per contraction - By Adolescence SV is increased to = 60 ml per contraction

Question 30

How does Cardiac Output change at birth?

Answer 30

-Recall CO = blood ejected from the left ventricle in one-minute CO (Q) = SV x HR -CO less in children in both resting and exercise -Newborn = 0.5 L / min -Children (3-12 years) = 3.6-4.8 L / min -Children have higher HR’s than adults but not enough to compensate for the reduced SV therefore still a lower CO compared to adults

Question 31

Why is no breathing required in the womb?

Answer 31

- Prenatal lungs filled with fluid = pulmonary resistance is very high, and no gas exchange occurs - No breathing movements are required because the foetal blood is oxygenated by the mother, so the brain doesn't tell the breathing muscles to move therefore decreasing the O2 demand

Question 32

What occurs at the first breath?

Answer 32

- This fluid is pushed out when thorax is compressed during birth - Decreased O2, increased CO2, light, mild cooling, sound and touch stimulate the respiratory centre in the brain to take the first breath - Alveoli expand and fill with air - Pulmonary vessels allow more blood flow

Question 33

What are the breathing rates from birth to 6years old?

Answer 33

oBirth = 40 / min o1 year = 30 / min o5-6 yrs = 22 / min -Respiratory tree fully developed by 8 years of age

Question 34

What is thermoregulation in infants and children?

Answer 34

-Body surface area (BSA)-to-mass ratio is important for thermoregulation oThis changes as one grows = 33% decline b/w 2 yrs – 16 yrs oAn infant and child has: > BSA to mass ratio = faster rate of heat dissipation which is advantageous particularly if the skin temp is higher than the environment -Not advantageous in cold climates -Low evaporative capacity oLower sweating rate (particularly in males) oSweat glands produce less = lower sweating rate per BSA -Pre pubertal sweat rate is less compared to post puberty in males oHigher sweating threshold -Sweating activated at higher intensities or higher core temperatures Therefore, children rely on more cutaneous blood flow oRely on heat loss via convection -Poorly developed vasoconstriction mechanisms oMinimal subcutaneous fat oShivering mechanism not matures

Question 35

What is Lactase?

Answer 35

Enzyme required for milk digestion is high at birth and gradually declines = milk diet

Question 36

How does digestion change at birth?

Answer 36

- Number of digestive enzymes increases as the infant gets older - Full set of deciduous teeth (n=20; no molar teeth) are present by 30 months - Blunt and limits chewing = reduced mechanical breakdown of food - Capacity of the stomach increases with age - Lower oesophagus sphincter is immature = contributes to reflux

Question 37

How does the Growth Hormone work?

Answer 37

- Growth promoting effects from the hormone directly on target tissues - Stimulates production of insulin like growth factors produced from the liver

Question 38

What are the Insulin Growth Factors?

Answer 38

Insulin like growth factors (growth promoting molecules) oIGF1 – Regulation of linear growth – long bone development, protein synthesis, increases cell proliferation oIGF2 – Particularly important during the foetal period for organ creation and muscle differentiation

Question 39

What does Thyroid Hormone influence?

Answer 39

-GH requires thyroxine to function -Influences growth and maturation oSkeletal growth and maturation oSexual maturation oMuscle development

Question 40

What happens at birth to Thyroid Stimulating Hormone levels?

Answer 40

- Accelerates most biological processes - TSH are at the their highest in infancy and childhood - Levels fall from birth

Question 41

Function of the Adrenal Medulla and Cortex?

Answer 41

- Adrenal Medulla = for normal growth and development | - Adrenal Cortex = regulation of growth and development