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BIOL 1191 > Ch. 29 - Development > Flashcards

Ch. 29 - Development Flashcards

1
Q

When is embryological development?

A

first 8 weeks after fertilization

- all principal adult organs are present

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2
Q

When is fetal development?

A

from 9 weeks until birth

- placenta is functioning by end of third month

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3
Q

What is fertilization?

A

haploid sperm + secondary oocyte merge; results in zygote with a single diploid nucleus

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4
Q

What is sperm capacitation?

A

series of functional changes sperm must go through to fertilize the egg

  • rapid beating of flagella
  • removal of cholesterol, prot, glycoproteins from plasma membrane near acrosome
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5
Q

What are the 2 layers sperm must penetrate to fertilize an oocyte?

A
  1. corona radiata
  2. zona pellucida
    - SP3 = sperm receptor in zona pellucida
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6
Q

What does sperm entry trigger in the oocyte?

A

to complete meiosis II; oocyte divides into a larger ovum and a polar body that degenerates

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7
Q

What is the difference between fraternal and identical twins?

A

F - dizygotic; independent release of 2 oocytes fertilized by 2 separate sperm

I - monozygotic; developed from a single fertilized ovum

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8
Q

What are cleavage and blastomeres?

A

C - rapid mitotic cell divisons of zygote

B - progressively smaller cells produced by cleavage

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9
Q

When does the cell mass (morula) become a blastocyst?

A

when morula enters uterine cavity by day 5

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10
Q

What does the blastocyst give rise to?

A
  1. embryoblast (inner cell mass); will develop into embryo

2. trophoblast (outer cell mass); will develop into chorion

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11
Q

What is implantation?

A

attachment of blastocyst to endometrium approx 6 days after fertilization
- trophoblast secretes hCG to maintain corpus luteum

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12
Q

What does human chorionic gonadotropin do?

A

hCG allows for sustained secretion of estrogen and progesterone, preventing menstruation

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13
Q

SUMMARY: what are the 5 events in the first week of development?

A
  1. fertilization (12-24h after ovulation)
  2. cleavage (30h after fertilization)
  3. morula (3-4 days after fertilization)
  4. blastocyst (4.5-5 days after fertilization)
  5. implantation (6 days after fertilization)
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14
Q

What are the 2 layers the trophoblast divides into?

A
  1. syncytiotrophoblast (outermost)

2. cytotrophoblast (inner layer)

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15
Q

What does the embryoblast differentiate into?

A
  1. hypoblast (primitive endoderm)

2. epiblast (primitive ectoderm)

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16
Q

What is the amnion?

A

membrane that develops from the epiblast

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17
Q

What is the function of amniotic fluid?

A

absorbs shock, regulates body temp, prevents adhesions with surrounding structures

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18
Q

What is the function of the yolk sac?

A
  • supply nutrients to embryo for next 1-2 weeks
  • conains primordial germ cells that become spermatogonia/oogonia
  • source of blood cells
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19
Q

What is the chorion and what forms it?

A

embryonic contribution to placenta; extraembryonic mesoderm and trophoblast

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20
Q

What is the function of the chorion?

A
  • secretes hCG

- suppresses maternal immune response against fetus

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21
Q

What is induction?

A

one tissue stimulates the development of an adjacent unspecialized tissue into a specialized one

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22
Q

During week 3, what does the bilaminar embryonic disc become?

A

trilaminar embryonic disc: ectoderm, mesoderm, endoderm

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23
Q

What will the endoderm become?

A

lining of GI, resp, outer urinary & reproductive tracts

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24
Q

What will the mesoderm become?

A

muscle, bone, CT, CVS, inner urinary & reproductive system

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25
Q

What will the ectoderm become?

A

skin epidermis, nervous system

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26
Q

What is the notochordal process?

A

when mesoderm cells migrate towards head and form notochord (solid cylinder)

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27
Q

How does induction occur during days 22-24?

A

notochord secretes substances that cause nearby unspecialized mesoderm cells to become vertebral bodies (become nucleus pulposus)

28
Q

Describe neurulation

A
  • notochord induces thickening of ectoderm to form neural plate
  • plate folds inward and forms neural groove
  • raised edges of neural plate are called neural folds
  • folds fuse into neural tube
  • develop in brain and SC
29
Q

What is spina bifida?

A

abnormality in neural tube closure; meninges and SC can protrude from vert column

30
Q

What is anencephaly?

A

failure of cranial bones to surround brain tissue, leading to degeneration

31
Q

What are the components of the placenta?

A
  1. fetal portion: chorionic villi of chorion

2. maternal portion: decidua basalis (endometrium)

32
Q

What are functions of placenta?

A
  • allows nutrient/waste exchange between mother and fetus
  • produces hormones needed to sustain pregnancy
  • act as barrier to most microorganisms
33
Q

Describe blood supply between placenta to embryo

A
  • 2 umbilical arteries (carry de-O2 fetal blood to placenta)

- 1 umbilical vein (carry O2 blood to fetus)

34
Q

How does the fetus’ proportions change shape from week 9 to birth?

A

head changes proportion; now smaller than rest of body

35
Q

What are 3 main causes for abnormal development?

A
  1. genetic
  2. environmental (teratogens)
  3. unknown
36
Q

What are some examples of teratogens?

A

alcohol, viruses, smoking, radiation

37
Q

When does abnormal development usually occur?

A

usually week 3-8; different effects depending on time of exposure

38
Q

What is a fetal ultrasonography?

A

screening tool (not diagnostic!)

  • emits high-freq sound waves which are converted to an image called a sonogram
  • usually taken ~week 10 and ~week 18
39
Q

What can a fetal ultrasonography show?

A

can confirm pregnancy, determine fetal age, viability, growth, position, multiple, and maternal abnormalities

40
Q

What can maternal blood screening detect? (quad screen)

A

test for abnormal levels of:

  • alpha-fetoprotein produced by fetus
  • human chorionic gonadotropin by placenta
  • estriol by fetus/placenta
  • inhibin A by placenta
41
Q

What can abnormal levels (from quad screen) indicate?

A

neural tube defect, trisomy 18/21, or other chrom disorders

42
Q

When are quad screens performed?

A

week 16-18

43
Q

What is amniocentesis?

A

needle inserted through abdominal wall and uterus to remove ~10mL of amniotic fluid (containing fetal cells)
- done ~weeks 14-16

44
Q

What can amniocentesis detect?

A

suspected genetic abnormalities

- fetal cells examined for gen disorders (e.g. down syndrome, sickle cell disease, hemophilia)

45
Q

What is chorionic villi sampling?

A

needle through abdominal wall or through cervix to remove ~30mg of chorionic villi (contains same genome as fetal cells)

  • done ~8 weeks
  • higher chance of spontaneous abortion
46
Q

What can chorionic villi sampling detect?

A

chromosomal analysis identifies same gen disorders as amniocentesis

47
Q

What is the function of hCG in pregnancy?

A
  • stimulates continued production of estrogens and progesterone by corpus luteum
  • for continued attachment of embryo/fetus to endometrium
48
Q

What is the function of estrogen/progesterone in pregnancy?

A

maintain lining of uterus and prep mammary glands

49
Q

What secretes hCG? Estrogen/progesterone?

A

chorion; corpus luteum (then secreted by placenta after 3rd-4th month)

50
Q

What is the function of relaxin in pregnancy?

A
  • increases flexibility of pubic symphysis and ligaments around pelvis
  • helps dilate uterine cervix during labour
51
Q

What is the function of human chorionic somatomammotropin (hCS)

A
  • helps prep mammary glands for lactation

- decreases glucose use in mother so more glucose is avail for fetus (increase FA use)

52
Q

What is the function of corticotropin-releasing hormone (CRH) in pregnancy?

A
  • establishes timing of birth (high levels = preemie delivery)
  • increases secretion of cortisol which is important for lung dev and surfactant production
53
Q

Describe the maternal CV changes to meet needs of fetus

A
  • rise in CO by 20%-30% due to placenta

- maternal blood vol increases by 30%-50%

54
Q

Describe the maternal resp changes

A
  • increase in TV by 30%-40%

- total body O2 consumption increases by 10%-20%

55
Q

Describe hormone changes that occur in labour

A
  • decease in progesterone to contract myometrium and relax cervix
  • increase in estrogen
56
Q

How do estrogen levels rise during labour?

A
  • placenta secretes CRH
  • fetal ant pituitary secretes ACTH
  • fetal adrenal glands secrete cortisol and DHEA
  • placenta converts DHEA to estrogens
57
Q

How does estrogen function during labour?

A
  • increase number of OT receptors on uterine muscle fibers
  • muscle fibers form gap junctions bt cells
  • stimulate placenta to release prostaglandins (that dilate cervix)
58
Q

What is false labour?

A

abdominal pain at irregular intervals that do not intensify

59
Q

What is true labour?

A
  • regular, painful, uterine contractions that increase in freq/intensity
  • dilation of cervix
60
Q

What are the 3 stages of true labour?

A

dilation, expulsion, placental

61
Q

What occurs in the dilation stage?

A
  • regular uterine contractions
  • rupture of amniotic sac
  • complete dilation of cervix (10 cm)
62
Q

What occurs in the expulsion stage?

A

baby moves through birth canal

63
Q

What occurs in the placental stage?

A
  • placenta expelled after delivery by uterine contractions

- contractions constrict BV to reduce risk of hemorrhage

64
Q

What are some changes in the CV system after birth? (infant)

A
  • foramen ovale closes

- ductus arteriosus and umbilical arteries/vein close and become ligaments

65
Q

What are some changes in the resp system after birth? (infant)

A
  • surfactant is produced by end of 6th month
  • umbilical cord is cut (no O2 in/CO2 out)
  • increased CO2 levels in blood stimulate resp centre in medulla
  • forceful inhalations and exhalations!

BIOL 1191 (16 decks)

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