Chapter 7 Power point – Prenatal Development

• Stages of Prenatal Development• Neonatal Adaptations

Prenatal Development – What is it?

• Period of time from conception until birth.• About 9 months (40 weeks)• Individual develops from two cells to complex

body systems and structures.

Conception• “When a mummy and daddy love each other very

much........”• Millions of sperm cells enter the females cervix. Propel

themselves up fallopian tubes looking for ovum.• Sperm cells can survive for up to 48 hours after leaving the

males body.• Sperm try to penetrate the membrane of the ovum. After 1

gets in, the ovum stops any other sperm cells from entering.

• Fertilisation occurs when the nucleic material of each cell combine. This is point at which the cell begins to divide rapidly (mitosis) according to the information contained in the new cells DNA.

3 stages of prenatal development

• The 9 months an individual spends in the womb can be divided into 3 main stage, which are distinct from each other in the length of time and the changes that occur.

• Germinal Stage• Embryonic Stage• Foetal Stage

Germinal Stage (4 events)• From conception until 2 weeks• New individuals journey from ovum to uterus.• After conception, a Zygote is formed – two cells combined

from sperm and ovum.• Conception takes place in the end of the ovum. After

fertilisation, the zygote moves down the fallopian tubes towards the uterus.

• As it travels, the cells divides (mitosis)• Cells divide every 24 hours.• After the first division, the individual is known as the

morula.

• So after 24 hours, the morula consists of _________ cells.

• After 4 days, the morula consists of _________ cells.

• At this stage, the group of cells becomes a blastocyst.

• Cells continue to divide but differentiate into cells that will form one of 3 specific structures:

• Embryo – the part that will become the baby.

• Placenta – A fluid filled sac that will provide the with oxygen and nutrients and remove waste.

• Chorion – an outer layer that protects the embryo until it enters the uterus.

• After about 10 days, the blastocyst attaches itself to the lining of the uterus, which is called the endometrium.

• This process is called implantation.• Once it attaches, the developing individual is

known as the embryo. • The embryo can continue to grow as it is

connected to the mothers circulatory system, and can receive nutrients

Embryonic Stage (9 events)

• From implantation (2 weeks) until end of week 8.• After week 2, the placenta forms. Is attached to

the uterus wall on one side and attached to the embryo by the umbilical cord.

• Placenta is very important as it only allows the necessary molecules to pass through to the embryo – oxygen, vitamins, minerals, simples sugars, amino acids. Blood systems stay separate as blood cells are too big to pass through into the placenta.

• During this stage, all of the major structures and features of the body begin to form.

• Head first.• Circulatory and Central Nervous System (brain and spinal

cord) second.• Remaining major systems begin to occur (heart, lungs,

digestive system).• Facial features.• Beginnings of arms and legs.• Sex organs develop by about the end of week 6.• Brain develops two visible hemispheres – left & right.• Fingers, toes, joints present before end of embryonic stage.

‘Critical Stage’• The embryonic stage is sometimes known as the

‘critical stage’• Because all of the structures of the body are

being formed, any interference in this process will have a permanent effect as they are not ale to be formed later.

• Anything that can interfere with this process and adversely affect growth and development is known as a teratogen. They can lead to diseases, abnormalities and termination of the embryo.

• Examples could include......

Teratogens

• Drugs• Alcohol• Malnutrition of mother• Physical trauma of mother• Illness mother is suffering from• SmokingEXAMPLE – Foetal Alcohol Syndrome (FAS). If the embryo is

exposed to alcohol it will often develop facial deformities, defective limbs, heart problems.

Foetal Stage (7 events)

• End of week 8 until birth (week 40)• Once all major structures formed, the

individual is known as a foetus.• No new structures created.• All the body parts that have begun to develop

increase in size, become more complex and develop new functions.

• Major changes can be roughly divided into stages by month

Third Month

• All major organs fully formed.

• Most body systems begin to function• Example. Foetus can swallow fluid, digest it and expel

the waste through urinating.

• Bones harden• Skeletal Muscles develop.• Foetus able to move

Fourth Month

• Fingernails and toenails.• Neural pathways developed to control

movements.• Foetus capable of reflexes.

Fifth Month

• Capable of voluntary movements.• Heart beat strong enough to be detected by

stethoscope.

Sixth Month

• Skin develops waterproof coating.• Fatty tissue formed under skin to provide

energy storage and insulation.• At the end of this month, foetus can open its

eyes.

Seventh Month

• Can survive if born.• Capable of basic breathing movements.• Heart can function.• Becomes very active.

Eighth Month

• Rotates into head first position.• Auditory system developed.• Brain develops more functions.

Ninth Month

• Ready for Birth• Increases immunity by obtaining antibodies

from it’s mother.• Becomes less active as it runs out of space.

NEONATAL ADPATATIONS

• Neo = after• Natal = birth• ‘After birth’

• Changes that an individual undergoes after being born so that it can survive independently outside of the womb.

What Adaptations? (4)

• Physical Movement & Reflexes• Circulation & Breathing• Digestion & Removal of Wastes• Temperature Control

Ability to move & respond

• We all have ‘innate’ abilities. Automatic responses to stimuli that we don’t have to learn.

• Has reflexes that occur without the involvement of the brain.

Examples of Movements Changes

• Rooting – Turning Head when cheek touched.• Sucking • Moro Reflex – Grabbing motion with arms

when laid on back.• Stepping – Walking motion when held

vertically• Grasping – Closing fingers around an object.

Circulation and respiration

• Before birth, blood only flows through the atria. Passage to heart but blood does not flow.

• When first breath is taken, lungs expand, increases pressure in chest – forces blood out of heart towards lungs.

• Pressure shuts foramen ovale. Atria and ventricles now used – heart more powerful.

Examples of changes

• Takes first breath• Passage between atria (Foramen Ovale) closes• Blood flows to lungs and is oxygenated.• Heart becomes more powerful.

Temperature Changes

• In the womb, a foetus has constant temperature. After birth, the baby needs to do this, but has poor temperature control at this time.

• When it is born, a baby is wet and loses heat quickly, so must be wrapped and kept warm

• A baby has few sweat glands, so must be kept cool when it is hot.

Examples of temperature control

• Increased metabolism• More active

Digestions & Waste Removal

• Has depended on nutrients from placenta.• Must now be able to take in it’s own

nutrients, so this system must start to function properly.

• Some wastes already stored in bowels form minimal digestive activity – needs to expel these.

Examples of Digestion changes

• Lungs remove CO2• All parts of digestive system become

functional• Kidneys filter wastes• Baby urinates and defecates soon after birth.

Apgar Scale

• Rating designed to quickly assess the health of a newborn.

• Assesses the vital statistics that a newborn will need to survive on it’s own.

• Split into 5 areas.• What do you think they would be? (What are

the important things that a newborn needs to have/be able to do?

5 Apgar measurements

• Heart rate• Respiratory (breathing) effort.• Muscle tone• Body colour• Reflex Irritability

How are these assessed

• Each criteria given a score -either 0, 1 or 2.• These scores identify any areas that may need

attention.• Total score out of 10• This combined score provides information about the

baby’s overall health.• A score of 7-10 is healthy.• 5 means possibility of some problems• 3 or less is an emergency – newborn may be unable to

survive.