Germination Stages of Prenatal Development

Neonates

GerminationHumans start off as a single cell organism: Gametes: The male/female reproductive cells Zygote: Formed an hour after the sperm enters

the ovum when the two gametes fuse Genes: Blueprints for creating a person

25,000 of them Composed of DNA molecules

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Deoxyribonucleic Acid: (DNA) Located along 46 chromosomes which are organized in 23 pairs. Each parent provides 23 chromosomes. Possible combinations are limitless. Nearly all of the cells of the body will contain

the same 46 chromosomes as the zygote.

Prenatal DevelopmentTypically divided into Trimesters:First: Conception to 3 monthsSecond: 3 to 6 monthsThird: 6 to 9 months

Prenatal DevelopmentConceptionOccurs the moment a sperm cell fertilizes the

ovum (egg cell), forming a single-celled zygote.

Prenatal DevelopmentThree Stages of Prenatal Development:

Germinal (2 weeks)Begins with conception.Takes place in one of the fallopian

tubes.Zygote travels to the uterus and

attachesitself to the uterine wall.

Rapid cell division occursOnce the zygote is successfully

attachedthe germinal stage is over.

Embryonic (6 weeks)Developing embryo forms all the major

body systems, organs, and structures.

Lasts from the beginning of week 3 through week 8.

Begins when the zygote attaches itself to the uterine wall.

Ends when the first bone cells form.1 inch long and weighs 1/7 of an ounce. Embryo already resembles a human being.

Prenatal Development

Fetal (38 weeks)Lasts from week 9 (when first bone

cells form) until birth.Experiences rapid growth and

further development of body structures, organs, and systems.

Prenatal Development

Prenatal Development Teratogen (any agent that causes birth defects):

Drugs (prescription, nonprescription) Alcohol, tobacco Environmental pollutants Infectious diseases Nutritional deficiencies Maternal stress Advanced age of a parent

Severity of damage to the unborn depends on: Dose Time of exposure Genetic susceptibility

Most serious Most serious damage from damage from

teratogens in first teratogens in first 2-8 wks 2-8 wks

Zygote Embryonic period (wks) Fetal Period (wks)

Period of susceptibility to functional defects

Period of susceptibility to structural defects

1 2 3 4 5 6 7 8 9 16 32 38

Teratogens and Timing of Their Effects on Prenatal Development

Central nervous system

Heart

Arms

Eyes

Legs

Ears

Teeth

Palate

External genitalia

Multiple BirthsLess than 3% of all cases result in twinsAny more is far less

Two types of twins: Monozygotic (Maternal twins): Identical Dizygotic (Fraternal): Completely different

individuals

Mothers carrying multiple children run a higher risk of premature delivery and birth complications.

NeonatesLabor: The Process of Birth Begins

Oxytocin: Released by the mother’s pituitary gland. When the concentration of oxytocin is high enough, mother’s

uterus begins periodic contractions.

Braxton-Hicks Contractions: (After 4th month) False labor

Contractions will eventually get strong enough to force the fetus down the birth canal until the baby enters the world.

Neonates:The Stages of LaborMost labors take 16-24 hours for firstborn

children.Duration of labor can vary depending on

mother’s:AgeRaceEthnicityNumber of prior pregnancies

Neonates:The Stages of LaborStage 1: (Longest stage) Labor Uterine contractions every 8-10 minutes

Last 30 secondsToward the end contractions occur every 2

minutesLast 2 minutes

As the contractions increase the cervix (separates uterus from the vagina) becomes widerEventually expanding to allow the baby’s

head to pass throughTransition: Final part of the first stage

Fully opened cervix is usually around 10cm

Stage 2: (Approx. 90 min) Delivery•Episiotomy: Incision made to increase the size of the vagina to help in stretching•Baby’s head emerges from the mother•Stage ends when the baby has completely left the mother•The placenta is still inside the mother at the end of this stage

Neonates:The Stages of Labor

Neonates:The Stages of LaborStage 3: (Quickest stage) AfterbirthExpelling of the umbilical cord and placenta

(afterbirth) Lasts just a few minutesIn most cases once a baby makes it outside they

spontaneously cry, which helps them to clear their lungs of fluid

If they don’t the child may need to be stimulated or startled to make it cry

If it still does not:Immediate life saving attention may be necessary

Neonates:Apgar ScaleRhythm: Repetitive, cyclical pattern of behavior.Important way that behavior can become

integrated in the neuronal system and aide in the learningCircadian Rhythm

State: Degree of awareness that an infant displays to

both internal and external stimulation.Alertness, fussing, crying, and different levels of

sleep. How much stimulation is necessary for a reaction

Neonates:Apgar ScaleApgar Scale Defined: A standard measurement system that looks

for a variety of indications of good health in newborns.

Evaluates 5 basic qualities: Appearance (color) Pulse (heart rate) Grimace (reflex irritability) Activity (muscle tone) Respiration (respiratory effort)

Scoring: From 0-2 on each of the five qualities Score total ranges from 0-10 Prognosis: Score from 10 down to 8 means that the child is fine Score from 7 down to 4 will most probably need help to start

breathing Score less than 4 means that the child needs immediate life-saving

attention

Score 0 1 2

Body ColorBlue, pale Body pink,

extremities blueEntire body pink

HeartbeatAbsent Slow – less than

100 beats per min.Fast – 100 to 140 beats per min.

Reflex Irritability

No response Grimace Coughing, sneezing, crying

Muscle Tone Limp and flaccid

Inactive, weak, some flexion of extremities

Strong, active motion

Respiratory Effort

Breathing for no more than 1 min.

Irregular and slow

Breathing good with normal crying

The Apgar Scale