Fetal development

Question 1

what is the difference between clinical weeks and gestational age?

Answer 1

gestational age is calculated from the first day of the last menstrual cycle
(week 1 fatal development=wk3 GA)

Question 2

what is the embryonic period?

Answer 2

weeks 1-8

Question 3

when is the fetal period?

Answer 3

weeks 9-37

Question 4

what is a morula?

Answer 4

solid ball of cells resulting in the division of a fertilised ovum (3-4days)

Question 5

what is a blastocyst?

Answer 5

the inner cell mass that forms the embryo (4-5days)

Question 6

what is the trophoblast?

Answer 6

the ouster layer of the blastocyst

Question 7

what is the blastocoele?

Answer 7

fluid around the inner cell mass, surrounded by the trophoblast

Question 8

where would you find the embryonic source of stem cells?

Answer 8

in the blastocyst

Question 9

what group of cells eventually becomes the placenta?

Answer 9

the trophoblast

Question 10

what is week 1 (fertilisation) in gestational age?

Answer 10

week 3 of gestational age

Question 11

where does fertilisation occur?

Answer 11

about 1/3 of the was down the fallopian tube

Question 12

what is a zygote?

Answer 12

the fusion of the gametes

Question 13

what is cleavage?

Answer 13

rapid cell division

Question 14

go through the post fertilisation action

Answer 14

36h- blastomere (2 Identical cells)
72h-morula (16+ cells)
day 3/4 - 100+ cells that float freely round the uterus

Question 15

what happens in week 2?

Answer 15

implantation

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Question 16

what is an ectopic pregnancy?

Answer 16

when the embryo implants and starts to develop in the fallopian tube

Question 17

what happens in week 2?

Answer 17

implantation

• the trophoblast cells bind to the endometrium in the uterine wall
• blastocyst differentiation

Question 18

What do you get in trophoblast differentiation?

Answer 18

• Cytrotrophblast - line the embryo
• sycyntiotrophoblast -secrete the proteolytic enzymes (continue eroding uterine wall), also secretes hCG preventing the endometrium sloughing off, causes progesterone+oestrogen release from CL, until 10 wks when placenta takes over

Question 19

what do you get after embryo differentiation?

Answer 19

bilaminar embryo

Question 20

what does hCG do during pregnancy?

Answer 20

• promotes the progesterone production
• angiogenesis of uterine lining (formation of new blood vessels)
• cyntroblast differentiation
• immunosuppression, blockage of phagocytosis invading trophoblast cells (prevents rejection of fetus)
• growth uterus lining with fetes growth
• quietending of uterine muscle contractions
• promotion of growth and differentiation of fetal organs

Question 21

what happens in week 3 of pregnancy?

Answer 21

gastrulation - formation of the brain, spinal chord and heart

Question 22

when does the first heart beat occur?

Answer 22

20-23 days after fertilisation

Question 23

what are the 3 germ layers present from embryonic disk during gastrulation (week 3)?

Answer 23

• Ectoderm
• mesoderm
• endoderm

Question 24

what is the ectoderm?

Answer 24

skin, nervous system and eyes

Question 25

what is the endoderm?

Answer 25

organs with mucus membranes: lungs, GI tracts and bladders

Question 26

what is the endoderm?

Answer 26

organs with mucus membranes: lungs, GI tracts and bladders

Question 27

what happens in week 4 of pregnancy?

Answer 27

neuralation- the neural tube closes (day 22 anterior end closes)

Question 28

what happens during neuralation? (week 4)

Answer 28

- neural tube closes (day 22, anterior end closes) - begining of organogenesis- tissues and systems begin to differentiate - Beginning of facial development - C shaped embryo - limb muds appear

Question 29

what happens in week 5 of pregnancy?

Answer 29

head and face development

Question 30

what happens in week 6 of pregnancy?

Answer 30

- all brain regions present - first brain waves (40 days after fertilisation) - finger development on upper limbs - eyes become visible - outter ears start to form

Question 31

what happens in week 7?

Answer 31

toes form, and the bending of arms and elbows

Question 32

what happens in week 8?

Answer 32

- Beginning of neck development - eyelids close on the eye - fingerprints - hearing begins - all body systems present in rudimentary form

Question 33

when does the embryonic period end?

Answer 33

week 8

Question 34

when do fingernails develop?

Answer 34

week 9

Question 35

what happens in week 9?

Answer 35

fingernails develop and the head make up about half of the foetus

Question 36

What significant things happen in week 12?

Answer 36

- the face resembles a human profile - the foetus can feel pain - fetus can suck its thumb - the placenta is fully developed

Question 37

What is the vernix caseosa? | and when does it appear?

Answer 37

it is fatty secretions that cover the body in the 5th month (17-20weeks)

Question 38

what occurs in the 5th month?

Answer 38

- vernix cases develops - languo (silk like hairs) - limbs reach final proportions - quicken occurs (first movements) - recognises the mother voice

Question 39

What happens in the 8th and 9th months?

Answer 39

- fetus uses 4 senses (vision, hearing, taste and touch) - there is fat accumulation under the skin - average -3.4kg and 7.6lb

Question 40

When does the cardiovascular system develop in the embryo/foetus?

Answer 40

week 6- heart development complete | week 14- heart rate can be heard (increased strength of muscle)

Question 41

when does the respiratory system develop in the embryo/foetus?

Answer 41

week 6- lungs begin to form week 14- hiccups week 33- surfactant production now sufficient

Question 42

when does the digestive system develop in the embryo/foetus?

Answer 42

week 5- bowel lengthens and leaves foetal abdomen | week 9- bowel back in abdominal cavity