prenatal development

Question 1

what % of organisms that have a spinal cord (chordates) have a bony sheath / skeletal

Answer 1

97%

Question 2

due to humans having spinal cords which group of organisms does it make us a member of

Answer 2

chordates

Question 3

how many species of chordates are there

Answer 3

around 6,000 in the world

and in terms of biodiversity amongst other living things there is a actually only a few of us - scientists have named 2 million different species

Question 4

early scientific views on prenatal development

Answer 4

1590s - invention of microscope

1695 - Nicalaas Hartsoeker and the performation theory of development

19th century - improvements in optics had demonstrated that embryonic development did not involve simple processes of growth but also substantial differentiation.

Question 5

Nicolass Hartsoeker

Answer 5

1695
the preformation theory of development

Question 6

the preformation theory of development

Answer 6

nicolaas Hartsoeker - 1695

looked at sperm under a microscope and saw that in the inside of it looked to be a human shaped element

led to the idea if preformation - the idea that development is entirely a matter of growth and the womb acts as place for this expansion to happen within

Question 7

aristotle - 384-322 b.c.

Answer 7

scala naturae - great chain of being species are fixed and arranged hierarchically

with humans at the top of the scale / ladder of creation

Question 8

an incorrect idea of evolution

Answer 8

that it is a directional process - a straight line from point a to point b

Question 9

what is the recapitulation theory

Answer 9

based on aristotle idea of ladder of creation

suggested that the embryo took the form of adult animals further down on the ladder of creation

Question 10

stages of recapitulation theory

Answer 10

fish phase - suggested due to theorists seeing that human embryos went through a fish like phase

followed by salamander stage of development

etc. tortoise, chick, hog, calf and rabbit before achieving the final goal

Question 11

stages of prenatal development

Answer 11

1. the germinal period - conception to implantation
2. the period of the embryo - implantation to 2 months roughly
3. the period of the fetus - 2 months to birth

Question 12

germinal period

Answer 12

sperm cell fertilizes an egg in the fallopian tube

zygote moves down the fallopian tube and into the uterus

4 days after conception the zygote multiplies to form a mass of cells called a mortula

after this the daughter cells decrease and decrease to leave a spherical mass of identical cells called stem cells (can grow into any type of tissue) in this stage the embryo is a blastocyst

finally the embryo implants on the uterus wall

Question 13

what is a mortula

Answer 13

when the zygote multipies to form a mass of cells

Question 14

what is a blastocyst

Answer 14

is a stage where the embryo is around 150 cells and has stem cells
happens at around 3 to 5 days

Question 15

period of the embryo - stage of implantation

Answer 15

happens around 8 weeks post conception

the blastocyst now differentiates into 3 distinct layers of different tissue types as each of these layers develop the become different major organ systems

last 2 months

Question 16

the 3 types of blastocyst tissue

Answer 16

ectoderm - top layer - nervous system, teeth, finger, nails and outer layer of skin

mesoderm - middle layer - muscles, bones and circulatory system and inner surface of the skin

endoderm - bottom layer - gastrointestinal tracks and major organs e.g. lungs and glands

Question 17

period of the fetus

Answer 17

this period is concerned with growth as most organs are developed
the liver is already developed and the eyes continue to develop as the brain grows

featus will respond to stimulation at this stage

hearing develops at 20 weeks

4 months there is motor development - movements such as sucking their thumb

by the end of this period featus respond with movement or heart rate changes to temperature changes or touch

Question 18

when does hearing develop

Answer 18

20 weeks - can detect low frequency sounds of around 250 to 550 hertz

(very narrow hearing band - adults = 20 to 20,000 hertz)

range of a voice

Question 19

variations from typical development statistic

Answer 19

world health organisation

orgins of congenital aberrations are unknown in 50% of cases

Question 20

genetics part in variation from typical development

Answer 20

Cystic fibrosis
sickle cell anemia
various chromosomal disorders

Question 21

environment part in variation from typical development

Answer 21

toxins - thalidomide, alcohol, radiation, pesticides

nutrition - folic acid

Question 22

how many chromosomes do we inherit from our parents

Answer 22

46 - 23 from each parent

Question 23

the process of cell dividing in half

Answer 23

mitosis

(supports growth)

Question 24

mitosis

Answer 24

prophase - duplicate chromosomes in cell

metaphase - chromosomes align at the metaphase plate

anaphase telophase - sister chromatids separate coursing two cells with the same genetic code to exist

Question 25

Meiosis

Answer 25

happens during the creation of the egg and sperm

so once division has ended you end up with daughter cells that half the original number of chromosomes

Question 26

human karyotypes

Answer 26

the pictation of chromosomes

Question 27

chromosomal variations

Answer 27

aneuplodiy - the condition of having fewer or more chromosomes than the usual number coursing developmental issues and learning difficulties

down syndrome - trisomy 21

edwards syndrome - trisomy 18

patau syndrome - trisomy 13

Question 28

chromosomal variations in the sex chromosome

Answer 28

there are lot of different variations that are compatible with life leading to intersex individuals

a lot more than just xx or xy

Question 29

define teratogens

Answer 29

are substances that cause birth defects
only effect the fetus affect the implantation phase due to a shared blood supply

Question 30

the thalidomide tragedy

Answer 30

drug developed in 1954 - to treat headaches, insomnia and morning sickness

by 1961 - the drug had led to 20,000 children in 46 different countries being effected by birth defects such as severely misshapen limbs

only effected children if prescribed during the 1st trimester as the limbs can only be effected during embryo period

Question 31

fetal alcohol syndrome

Answer 31

course by alcohol effecting the development of the central nervous system

cause unusual facial structure and an under developed brain
children have difficulties with vision and hearing plus face learning difficulties

Question 32

DeCasper and spence - 1986

Answer 32

fetal learning
N=16 gestation age 7.5 months

read stories 2x a day

tested at 2.5 days after birth
half hear same stories after fast sucking of the dummy and half hear it after slow sucking

result - babies showed preference for familiar stories as they

Question 33

hepper 1991

Answer 33

neighbors - soap show
sampled mothers who religiously watch the show and those who didn’t

look for difference in their babies when playing the stimulus (show intro) after they were born

found clear difference in the movements of the learning group