Lecture 8 Parental Development Flashcards
(60 cards)
What is the period of the zygote (blastocyst) phase?
0–14 days:
ball‑like structure of 60–80 cells by day 4,
implantation occurs between days 8–14.
What happens to fertilized ova during implantation?
Only half implant firmly; of these, half are genetically abnormal or fail to develop; ~¾ of zygotes fail this phase.
How do identical (monozygotic) twins form?
Splitting of the inner cell mass of the blastocyst, can occur before or after implantation.
How do fraternal (dizygotic) twins form?
When two separate eggs are released and both are fertilized.
What marks the transition to the embryonic period?
Blastocyst implants in uterine wall and becomes an embryo (3–8 weeks).
What are the two developmental patterns during embryo development?
Cephalocaudal (head→tail) and proximodistal (centre→periphery).
What develops by week 3 of embryonic stage?
Head, tail, brain, circulatory system begin; heart starts beating.
What is fetal development by week 4?
Embryo ~2 cm; spinal cord, arms, legs, digestive and nervous systems form; brain differentiates.
What occurs during weeks 5–7 of the embryo?
Week 5: hands & lungs begin;
Week 6: head grows, limbs form;
Week 7: muscles form, cerebral cortex begins.
What is the function of the amnion?
A watertight sac with fluid that cushions, regulates temperature, provides weightless environment.
What is the chorion?
Membrane surrounding amnion; later becomes the placenta lining.
What does the allantois form?
The umbilical cord.
What is the role of the placenta?
Transports oxygen and nutrients from mother; removes waste from embryo; filters some toxins.
What are the umbilical cord’s components?
Three blood vessels: one brings nutrients to embryo, two remove waste.
What forms by the end of the 8th embryonic week?
at about 8 weeks, the embryo develops its first bone cells which mark the end of the differentiation into the major structures.
What is the neural tube?
Fused ectodermal groove that develops into the brain and spinal cord.
When do first bone cells appear in the embryo?
Around 8 weeks—marks end of major structure differentiation.
When does the fetal period begin and what characterizes it?
9th week to birth: growth, fine feature development (fingernails, eyelids, eyebrows).
When can fetal reflexes and heartbeat be detected?
By 12 weeks (~7.5 cm): response to touch (grasp, Babinski, suck reflex); heartbeat audible.
When does spontaneous movement start in fetus?
Around 5–6 weeks; by 12 weeks, most neonatal movements are present.
What sensory stimuli does the fetus receive?
Tactile, taste (amniotic fluid flavours), smell (odor transfer), limited sight, and hearing.
What is the fetal hearing environment like?
Noisy – 70–95 dB (like a lawnmower); fetus responds to maternal voice (heart rate changes).
When does fetal learning begin?
Last 3 months of pregnancy: CNS supports habituation, preference for familiar stimuli.
What is fetal habituation?
Decreased response to repeated stimulation; heart rate studies show novelty response.
