Chapter 4

Question 1

What are the three major stages of prenatal development

Answer 1

1. Period of the zygote → lasts 10 to 14 days
   Lasts from conception to implantation when the zygote becomes attached to the wall of the uterus
2. Period of the embryo → lasts from beginning of 3rd week through the end of the 8th
   The time when all major organs are formed and the heart begins to beat
3. Period of the fetus → lasts from 9th week of pregnancy till the child is born
   All major organ systems begin to function and the developing organism grows rapidly

Question 2

Explain the period of the zygote, also known as the germinal period

Answer 2

As the fertilized ovum, or zygote, moves down the fallopian tube toward the uterus, it divides by mitosis into 2 cells. These 2 cells and all the resulting cells continue to divide, forming a ball-shaped structure, or blastocyst, that will contain 60 to 80 cells within 4 days of conception. Cell differentiation has already begun. The inner layer of the blastocyst/embryonic disk, becomes the embryo, whereas the outer layer of cells will develop into tissues that protect and nourish the embryo.

Question 3

Explain the implantation process briefly

Answer 3

Within 4 days there’s this blastocyst that’s against the uterus that biologically communicates with the uterine wall to implant itself into that wall. It gets stuck/embedded into that wall. It takes about 48 hours for it to become fully implanted into the uterine wall.
Not all fertilized cells can do this, half of all fertilized cells actually implant and half of those don’t make it because of some abnormalities (with mitosis, etc) → 3/4 zygotes fail to survive the initial phase of prenatal development

Question 4

Explain the support structures of the blastocyst

Answer 4

Once implanted, the blastocyst’s outer layer forms 4 major support structures that protect and nourish the developing organism

1. The amnion = A watertight membrane that surrounds the developing embryo, serving to regulate its temperature, to cushion it against injuries (protection) and makes a weightless environment so fetus can move/grow/ practice breathing & swallowing
2. The chorion
3. The placenta = A collection of cells that are able to feed the fetus (through mother’s blood vessels) without interacting with the mother’s blood vessels since the placenta is semipermeable → (blood barrier (stops bloods from mixing), CO2, O2, nutrients, salts)
4. The umbilical cord = Part of the inner mass that forms the connection between the inner cells and outer cells
   Brings into the embryonic disk O2, nutrients, salts, everything from maternal blood and is able to take out CO2 and any metabolic waste the fetus creates.

Question 5

Explain the period of the embryo, also known as the embryonic period

Answer 5

Once the embryonic disk (inner collection of cells) becomes implanted it divides into three layers

Question 6

Explain development from week 1-2

Answer 6

This is the period of the zygote.

Week 1: One-celled zygote divides and becomes a blastocyst

Week 2: Blastocyst implants into uterine wall; structures that nourish and protect the organism—amnion, chorion, yolk sac, placenta, umbilical cord—begin to form

Question 7

Explain development in week 3

Answer 7

Period of embryo

Week 3: The embryonic disk is rapidly differentiating into 3 cell layers.
The outer layer - ectoderm, which becomes the CNS, skin & hair.
The middle layer - mesoderm, which becomes muscles, bones and circulatory system.
The inner layer - endoderm, which becomes the urinary tract, digestive & respiratory system, and other vital organs (pancreas, liver, etc)
The primitive heart is formed and a portion of the ectoderm folds into neural tube that becomes the brain and spinal cord.

Question 8

Explain development in week 4

Answer 8

Period of embryo
Week 4: Heart has formed and began to beat. The eyes, ears, nose, and mouth are also beginning to form and buds that will become arms & legs appear.
The end of the neural tube swells to form a brain and the tail becomes a spine.
The kidneys, liver and intestines begin to form.

Question 9

Explain development in week 5-6

Answer 9

Period of embryo

Week 5-6:
The heartbeat is detected through ultrasound.
There is electrical activity in the brain.
The embryo moves in response to stimuli.
Develop indifferent gonads

Question 10

Explain development in week 7-8

Answer 10

Period of embryo

Week 7: 
Major organs have started to form.
Hair follicles and nipples form.
Knees and elbows are visible.
Facial features are visible
Blood type is selected.

Week 8:
The embryo is reactive to the environment in the amniotic sac and it swims & moves.
The hands and feet can be seen.
The embryo has all its major organs and features of human being

Question 11

Explain development in week 9-12

Answer 11

Period of fetus.

Week 9-12:
All major organ systems begin to function and rapid.
The face is well formed and the eyes are almost fully developed.
The eyelids close to reopen in the 28th week.
The arms & legs are fully developed (with toes, etc)
Nails, earlobes and tooth buds are forming.
If there is a Y chromosome, there is a release of testosterone to produce testes

Question 12

Explain development in week 13-16

Answer 12

Period of fetus.

Week 13-16:
The brain is fully developed and the fetus is beginning to prepare for post natal environment

The fetus starts to suck, swallow, and make irregular breathing sounds.
The fetus can feel pain and can make active movements.
The fetal skin is almost transparent and has a more detailed appearance.
There is major weight gain → 3 oz to 30 oz

Question 13

Explain development in week 17-20

Answer 13

Period of fetus.

Week 17-20:

The vernix covers the baby’s body for protection from amniotic fluid.
Fine hair appear over body to also protect the baby
Mother feels movements
Nails appear
20 wks: fetus can hear and recognize the mother’s voice → cognitive development: short term memory + long term memory is forming
Sex organs are visible on ultrasound
Brain size develops rapidly (6X in size)

Question 14

Explain development in week 24

Answer 14

Period of fetus.

Week 24:

Footprint and fingerprint form
Breathing practices by inhaling/exhales amniotic fluid into developing lungs → allow baby to survive in postnatal environment
Brain exhibits brainwaves and electrical activity
Age of viability BUT pulmonary alveoli are too immature to inflate and exchange O2 for CO2
Baby can survive if born now but it’s hard since it JUST started to practice breathing

Question 15

Explain development in week 25-28

Answer 15

Period of fetus.

Week 25-28:

Rapid weight gain
Rapid brain development → electrical activity + ns is able to control some body functions
Nervous system is able to control some bodily functions
25th wk: reacts to nearby sounds
25th wk: 60% chance of survival if born → breathing is still hard

28 weeks: fetus legally viable => 90% chance of survival
Eyelids open and close
28 weeks: distinct sleep-wake patterns
Beginnings of temperament: mom can recognize whether this child will be one that will stick to routine, etc => basic beginning to your personality

Question 16

Explain development in week 28-32

Answer 16

Period of fetus.

Week 28-32:

Rapid increase in the amount of body fat

32nd wk: baby weighs about 4 lbs and has good chance of survival outside the uterus.

Rhythmic breathing occurs, but the lungs are not yet mature.

Sleeps 90-95% of the day

Survival rate is above 95% if born now
Ready for postnatal world

Question 17

Explain the embryotic period: 4th week gestation

Answer 17

• The gastrointestinal system begins to develop (i.e. primitive kidneys, liver, and
  intestines forming)
• Heart begins to beat
• End of neural tube swells to form brain
• Eyes, ears, nose and mouth start to form
• Buds become arms and legs
• Tail becomes spine

Question 18

When do the gonads develop

Answer 18

By the 5-6th week humans develop indifferent gonads. It is indifferent because whether you are genetically male or female those gonads have not developed yet. However by the 8-9th week, if you have a Y chromosome then it sends a message to those indifferent gonads to send testosterone. If there is no Y chromosome, the indifferent gonads become ovaries

Question 19

What are the 3 stages of delivery

Answer 19

1. • First stage of labor: 8-14 hours for 1st borns, 3-8 hours for 2nd born
   • Begin when contractions spaced 10-15 mins
   • Ends when cervix is fully dilated
2. • Second stage of labour (delivery): 30 - 90 mins
   • Begins when fetus’ head passes through cervix and
   • Ends when baby has emerged
3. • Third stage of labor (afterbirth): 5-10 mins
   • Placenta expelled

Question 20

What are reflexes

Answer 20

Reflexes are involuntary, automatic responses to stimuli. It is embedded in the DNA.

Question 21

What is anoxia and its effects

Answer 21

Anoxia is a lack of sufficient oxygen to the brain which may result in neurological damage or death. In many cases, this happens because the umbilical cord has become tangled or squeezed during childbirth. 
Mild anoxia (3-4 mins): Effects may be short term, ex: score low on tests of motor and mental development for the first 3 years of life, by 7 the effects can go away
Severe anoxia (4 mins +): The effects may result in permanent brain damage, ex: physical, neurological disabilities because different parts of the brain may have been so starved of blood flow that they just die

Question 22

What are the reasons for which a baby might be born with a low birth weight

Answer 22

• They are born prematurely: are normal weight for the point in life they are at
• They are small for date babies: have experienced slow growth as fetuses → they have a greater risk for death or brain damage since there was some issue in the prenatal environment in which development did not occur properly

Question 23

What are the short term consequences of low birth weight

Answer 23

Any baby below 2500 g is considered to have a low birth weight
Half the babies who weigh less than 1000 g die shortly after birth

Small for date babies:
- Malformed + undernourished → important to increase intake of nutrients

Preterm babies:
- Difficulty breathing since lungs did not form properly ( low levels of surfactin which is something that coats the lungs, without it, lung most likely collapses) lack of practise → important to get their lungs working

• Slow to initiate social interactions because their brain development did not happen properly. The neurons needed that time to connect to form the social connections → Important to get the parents to bond with the child as much as possible to get the brain connections to occur

Question 24

What are the long term consequences of low birth weight

Answer 24

Any baby below 2500 g is considered to have a low birth weight
Half the babies who weigh less than 1000 g die shortly after birth

The long term effects depend on postnatal environment (and severity of growth and length of gestational period)

If the mothers are more involved with the child and create a stimulating home environment they can compensate for the slow growth or the early gestational period. Creating that environment allows for the brain connections to occur.
Those infants who come from an economically disadvantaged home:
- stay small
- emotional problems
- lower iq
- increase likelihood of creating certain learning disabilities

Question 25

What is a typical 24 hour period of a child

Answer 25

Regular sleep (8-9 hours): Baby is still, with eyes closed and unmoving. Breathing is slow and regular.

Irregular sleep (8-9 hours): Baby’s eyes are closed but can be observed to move under the closed eyelids (a phenomenon known as rapid eye movement, or REM). Baby may jerk or grimace in response to stimulation. Breathing may be irregular.

Drowsiness (1/2-3 hours): Baby is falling asleep or waking up. Eyes open and close and have a glazed appearance when open. Breathing is regular but more rapid than in regular sleep.

Alert inactivity (2-3 hours): Baby’s eyes are wide open and bright, exploring some aspect of the environment. Breathing is even, and the body is relatively inactive.

Alert activity (1-3 hours): Baby’s eyes are open and breathing is irregular. May become fussy and display various bursts of diffuse motor activity.

Crying (1-3 hours): Intense crying that may be difficult to stop and is accompanied by high levels of motor activity.

RIDA(i)A(a)C

Riley Irvin danced avariciously at Concordia

Question 26

What are teratogens

Answer 26

Teratogens are external agents, such as viruses, drugs, chemicals, and radiation, that can harm a developing embryo or fetus

Environmental contributors that can harm developing fetus → ex: viruses, drugs, chemicals, radiation

The timing & amount of exposure will have different impacts on different fetuses
Another aspect to keep in mind is the heredity, 2 mothers can have the same alcohol and amount have different reactions (for baby) → multifinality
- 2 mothers can do diff things but end up having babies with the same disability → equifinality

Question 27

What are maternal characteristics

Answer 27

Things the mother does that affects development

Ex: nutrition, emotional well-being, age, etc

Question 28

What is the importance of emotional bonding

Answer 28

• Important to emotionally bond with the child

mothers who had early extended contact with their babies appeared to be more involved with them and held them closer during feeding sessions than did mothers who had followed the traditional hospital routine. One year later, the extended-contact mothers were still the more highly involved group of caregivers
and their 1-year-olds outperformed those in the traditional-routine group on tests of physical and mental development. Apparently, extended early contact in the hospital fostered mothers’ affection for their newborns, which, in turn, may have motivated those mothers to continue to interact in highly stimulating ways with their babies.