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IMS TEST 2 > L13 Introduction to Embryology > Flashcards

L13 Introduction to Embryology Flashcards

1
Q

what is the correct terminology (adult human) for: up, down, front, back

A 
up = superior
down = inferior
front = anterior
back = posterior
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2
Q

what is the correct terminology (foetus) for: up, down, front, back

A 
up = cranial
down = caudal
front = ventral
back = dorsal
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3
Q

what is the correct terminology (foetus) for sectioning: across the middle, down the middle, separating front and back

A

across the middle = transverse section

down the middle = sagittal section

separating front and back = coronal section

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4
Q

what are the two methods of dating a pregnancy?

A
  1. the menstrual age (mostly used by clinicians).

2. fertilisation age (mostly used by embryologists)

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5
Q

What is the menstrual age of dating a pregnancy?

A

it uses the woman’s last menstrual period and is shown as 3 trimesters and lasts 40 weeks (to account for 2 weeks for ovulation.

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6
Q

what is the fertilisation age of dating a pregnancy?

A

the fertilisation age describes 3 uneven period of time during the pregnancy.
0-3 weeks = Early Development (cell proliferation)
3-8 weeks = Embryonic (organogenesis) period
8-38 weeks = foetal period

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7
Q

by what percentage are patients usually diagnosed: prenatally, at birth, after one week, after 2 to 4 weeks, up to one month?

A 
prenatally - 61%
birth - 27%
after 1 week - 3%
after 2 to 4 weeks - 2%
up to 1 month - 6%
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8
Q

what are the causes of human birth defects?

A 
genetics = meiosis or mitosis, 
environmental = teratogens (which means monster-forming in latin)

genetic and environmental multifactorially makes up 25% of malformations

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9
Q

what is a monogenic malformation?

A

defective gene on an autosome which may be inherited

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10
Q

how may chromosomal malformations arise?

A

by numerical or structural problems eg during chromosome separation or misalignment of genetic material

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11
Q

which is the trisomy 21 mutation? what are the phenotypic presentations?

A

Down’s Syndrome - an extra copy of chromosome 21.

phenotypic presentations = growth retardation, intellectual retardation, craniofacial abnormalities, congenital heart defects

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12
Q

give 5 environmental causes (teratogens) and give examples

A

infectious diseases - TORCH

chemicals (thalidimide or alcohol)

deficiencies (folic acid)

maternal diseases (diabetes)

physical (radiation)

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13
Q

what does the infectious diseases acronym TORCH stand for?

A 
Taxoplasmosis
Other (Hep. B, syphilis)
Rubella
Cytomegalovirus
Herpes

these diseases can CROSS THE PLACENTA and possibly cause birth defects

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14
Q

when is the foetus more sensitive to environmental factors?

A

most sensitive at 3-8 weeks during the embryonic stage. malformations during the early development stage are generally detected and stopped (sometimes resulting in miscarriages)

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15
Q

when is the CNS susceptible to teratogens?

A

weeks 3-20 can result in major congenital malformations. weeks 20 to 38 functional defects + minor congenital anomalies could occur

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16
Q

when is the heart most susceptible to teratogens?

A

weeks 3.5-6.5 = major congenital anomalies

weeks 6.5-8 = functional defects + minor congenital anomalies

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17
Q

when are the upper limbs susceptible to teratogens?

A

weeks 4-end of week 5 = major congenital anomalies

weeks 5-8 = functional + minor congenital defects

18
Q

when are the eyes susceptible to teratogens?

A
  1. 5-8.5 weeks = major congenital anomalies

8. 5-38 weeks = functional defects

19
Q

when are the lower limbs susceptible to teratogens?

A
  1. 25-6.25 weeks = major

6. 25 - 8 weeks = functional defects

20
Q

when are the teeth susceptible to teratogens?

A

6.75 weeks - 9 weeks = major

9-38 weeks = functional defects

21
Q

when is the palate susceptible to teratogens?

A

weeks 6.75-9.25 = major

weeks 9.25-16 = functional defects

22
Q

when is the external genitalia susceptible to teratogens?

A
  1. 25-9.75 = major

9. 75-38 = functional defects

23
Q

when is the ear susceptible to teratogens?

A
  1. 25 - 8.5 = major

8. 5 - about 21 weeks = functional defects + minor anomalies

24
Q

what is toxoplasmosis and the congenital malformations associated with it?

A

parasite infection found in cat faeces and undercooked/raw meat. usually asymptomatic but if mother gets infected whilst pregnant then can be passed on to foetus.

malformations:

  • inflammation of retina and eye (micropthalmia)
  • hearing loss
  • enlarged liver/spleen
  • hydrocephaly
  • microcephaly
25
Q

how does rubella result in congenital malformations?

A

infection passes over placenta in first 3 months of pregnancy and presents as skin lesions.

malformations:

  • cloudy cornea
  • intellectual disability
  • microcephaly
  • heart defects
26
Q

how can the cytomegalovirus cause congenital malformations?

A

infection via bodily fluids - can cross placenta. usually asymptomatic but infection during pregnancy results in malformations.

malformations:
- inflammation of retina/micropthalmia
- enlarged liver/spleen
mineral deposits on brain
- microcephaly
- psychomotor retardation
27
Q

what is herpes and how can the virus cause congenital malformations?

A

herpes simplex and herpes zoster. varicella zoster = chickenpox. most dangerous between 13-20 weeks , just before birth or 2 days postpartum.

malformations:

  • segmental skinloss/scarring
  • limb hypoplasia/paresis
  • microcephaly
  • visual defects

(does not travel up woman’s reproductive cycle - is passed on during vaginal birth)

28
Q

what malformations does the zika virus cause?

A

passed on my mosquito and bodily fluids and results in fever, rash, joint pain and red eyes.

malformations:

  • microcephaly
  • severe cognitive disabilities
29
Q

what is thalidomide?

A

developed in germany in 1950s and prescribed for morning sickness. resulted in shortened or absent limbs but is now used to treat leprosy (brazil) and HIV

30
Q

what is Foetal Alcohol Syndrome (FAS)?

A

relationship between alcohol consumption and congenital abnormalities

associated with:

  • prenatal and postnatal growth retardation
  • intellectual disability
  • impaired motor ability and coordination

physically:

  • small eye openings
  • smooth philtrum
  • thin upper lip
31
Q

how does radiation cause malformations?

A

causes cell death or chromosome changes - CNS most sensitive (ep in 3rd trimester).

malformations:

  • microcephaly
  • mental and cognitive disabilities
  • haemopoietic malignancies and leukemia
32
Q

how does maternal diabetes mellitus result in malformations?

A

can cause cellular structural defects and changes in cellular physiology
too much glucose crossing placenta

malformations:

  • macrosomia
  • ventricular septal defects
  • spinda bifida
  • renal agenesis
33
Q

which malformations does folic acid deficiency cause?

A

malformations in CNS but over-the-counter supplements reduce risk by 60%.

malformations:

  • spina bifida
  • anencephaly
  • neural tube defects
34
Q

what is gametogenesis?

A

formation of gametes

35
Q

what happens during fertilisation?

A

fusion of male and female gametes to form zygote. usually happens in ampulla of uterine tube. fimbriae sweep oocyte into uterine tube

  • capacitation of sperm (changes chemical structure of head of sperm)
  • acrosome reaction
  • formation of zygote
  • fusion of pronuclei
36
Q

what happens during the acrosome reaction?

A

capacitated sperm pass through corona radiate

acrosome releases enzymes allowing sperm to penetrate zona pellucida

sperm penetration initiates cortical reaction (causes cortical granules to release contents)

so zona pellucida becomes impenetrable

zygote is formed

37
Q

what happens during cleavage after fertilisation?

A

zygote cells divide.

no change in size of zygote but blastomeres get smaller. cleavage first happens after 24 hours.

38
Q

how many stages and days until a blastocyst is formed?

A 
day 0 - pronuclear stage
day 1 - 2-cell
day 2 - 4-cell
day 3 - 8-cell
day 4 - morula (16-32 cells)
day 5 - blastocyst
39
Q

what is the structure of the morula?

A

16-32 cells
inner cell mass (embryblasts) forms embryo proper
outer cell mass trophoblasts) forms placenta and support structures

40
Q

what is the structure of the blastocyst?

A

formed as a fluid filled cavity by day 5
compact mass - inner cell mass (embryoblasts)
thinner outer layer - outer cell mass (trophoblasts)

41
Q

what happens during days 5 and 6 of fertilisation

A

implantation into uterine wall and hatching

IMS TEST 2 (14 decks)

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