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Respiratory system > Embryology > Flashcards

Embryology Flashcards

1
Q

what is the name of the diploid cell in females that divides by meiosis to form gametes?

A

oogonium

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2
Q

what is the name of the diploid cell in males that divides by meiosis to form gametes?

A

spermatogonium

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3
Q

what happens during fertilisation?

A

the pro-nucleus of a sperm enters penetrates the ovum and fuses with the nucleus of the ovum to form a zygote

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4
Q

what is a zygote?

A

the first cell formed after fertilisation

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5
Q

what is a morula?

A

the ball of cells formed by the dividing of the zygote

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6
Q

why is the fact that only the nucleus of the father fuses with the ovum clinically important?

A

it means that all organelles are inherited from the mother so in genetic abnormalities carried in the mitochondrial DNA will only be passed on by the mother

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7
Q

why does the morula form a blastocyst?

A

getting nutrition to the centre core of the morula becomes difficult as the morula becomes larger. to get around this a blastocyst forms with a blastocystic cavity where nutrients can reach the growing mass of cells.

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8
Q

what is the outer lining of cells called in the blastocyst?

A

the trophoblast

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9
Q

what does the trophoblast differentiate to form?

A

the placenta and the membranes around sacs around the feotus

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10
Q

describe the movement of the zygote from the ovaries to the uterus and the changes that it undergos?

A

it moves from the ovary down the fallopian tube to the uterus, helped along by ciliated squamous cells in the tube. It begins as a zygote then by the time it reaches the end of the fallopian tube it is a morula, when it enters the uterus it is a blastocyst

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11
Q

what may happen if cilia function in the fallopian tubes is abnormal eg. in some STIs?

A

an ectopic pregnancy where the blastocyst implants in the wall of the fallopian tube

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12
Q

where does the blastocyst implant in the uterus?

A

uterine endometrial layer

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13
Q

what does the inner mass of the blastocyst form on implantation?

A

bilaminar disc

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14
Q

at what stage of pregnancy does the blastocyst implant into the endometrium wall?

A

~7 days

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15
Q

what is the chorion?

A

the structure that the trophoblast changes into to facilitate implantation, it does this by possessing chorionic villi

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16
Q

what is the function of the chorion?

A
  1. implantation process
  2. forms part of the placenta
  3. secretes human chorionic gonadotropin which stimulates the release of oestrogen and progesterone from the ovaries.
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17
Q

what is the decidua basalis?

A

the layer of the endometrium deep to the implanted conceptus. It becomes the mother’s side of the placenta

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18
Q

what is the purpose of HCG?

A

maintains the endometrium by stimulating the release of oestrogen and progesteron

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19
Q

what forms the bilaminar disc?

A

a 2-layered flat disc formed from the inner cell mass of the blastocyst

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20
Q

what are the two layers of the bilaminar disc?

A

epiblast

hypoblast

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21
Q

what is the cavity above the bilaminar disc called ?

A

the amniotic cavity

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22
Q

what is the cavity below the bilaminar disc called?

A

the yolk sac

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23
Q

what is the cavity called into which metabolic waste products of the feotus drain into?

A

allantoic cavity

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24
Q

what are the main functions of the placenta?

A
  1. foetal nutrition
  2. transport of waste and gases
  3. immune
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25
Q

what are the types multiple birth/twins?

A
  • dizygotic

- monozygotic

26
Q

explain how dizygotic twins form?

A

2 ova are released at the same, one from each ovary. Both are fertilised to produce twins with different genetic makeup

27
Q

explain how monozygotic twins form?

A

one ovum is fertilised by one sperm then the zygote splits and each develops into a different embryo.

28
Q

what is the sequence of events in the first two weeks of life?

A
  1. fertilisation, zygote
  2. morula reaches uterine cavity
  3. blastocyst with inner cell mass impants in endometrium
  4. decidua basalis forms
  5. placental formation begins
29
Q

what is the formation of germ layers in week 3 called?

A

gastrulation

30
Q

what is the formation of neural tube in week three called?

A

neurulation

31
Q

describe gastrulation?

A
  1. primitive streak forms in epiblast
  2. cells in this streak migrate into space between epiblast and hypoblast
  3. cells from epiblast replace those from hypoblast
  4. this forms three layers, the ectoderm, mesoderm and endoderm.
32
Q

what is the name of the end product of gastrulation?

A

the trilaminar disc

33
Q

are the cells in the trilaminar disc specialised?

A

yes

34
Q

how does the notochord form?

A
  1. a primitive streak forms in the ectoderm
  2. the cells in this streak sink down to form a solid tube between the mesoderm and the endoderm
  3. this is the noochord
35
Q

describe the formation of the neural tube?

A
  1. the notochord induces the ectodermal cells in the midline to form a neural plate by extending down into the mesoderm
  2. the neural plate then sinks down to form a neural tube
36
Q

describe how formation of somites

A
  1. the neurel tube induces the mesoderm to thicken
  2. the mesoderm separates into 3 parts (paraxial, intermediateplate and lateral plate mesderm)
  3. the paraxial mesoderm segments to form somites
37
Q

how many pairs of somites do we have ?

A

43

38
Q

what happens to the lateral plate mesoderm in week three?

A

splits to form a somatic and splanchnic mesoderm

39
Q

what is the space called between the somatic and splanchnic mesoderm?

A

the intraembryonic coelom

40
Q

what does the intermediate plate mesoderm form?

A

kidneys and reproductive system

41
Q

what does the lateral plate mesoderm form?

A

body cavities, peritoneum and pleura

42
Q

what do the somites divide into?

A

dermatomes, myotomes and sclerotomes

43
Q

what do the dermatomes form?

A

dermis of the skin

44
Q

what do the myotomes form ?

A

muscles

45
Q

what do the sclerotomes form?

A

bones

46
Q

what occurs in the embryonic period, in terms of folding?

A

lateral folding occurs to form a tube

47
Q

what occurs in the embryonic period in the neural tube?

A

forebrain, midbrain, hindbrain, and spinal cord development

48
Q

on what day of development does the heart start to beat?

A

day 24

49
Q

in the embryonic stage what does the gut form from?

A

the endoderm

50
Q

what occurs in the embryonic period, in terms limb formation?

A

limb buds form

51
Q

what occurs in the embryonic period, in terms of developing of the neck?

A

pharyngeal arches form

52
Q

describe the process of lateral folding of the embryo?

A

the endoderm, lateral mesoderm and ectoderm fold so that the endoderm forms a tube within the ectoderm and mesoderms

53
Q

apart from laterla folding what other type of folding occurs?

A

head and tail folding

54
Q

what is teratology?

A

study of when thingd go wrong during development

55
Q

what is a teratogen?

A

environmental factors that cause abnormal development

56
Q

give some examples of teratogenesis?

A

congenital rubella syndrome- cataracts caused by contraction of german measles when pregnant
-malformed limbs caused by thalidomide

57
Q

what are some environmental teratogens?

A

drugs
alcohol/tobacco
infectious agents
radiation

58
Q

what does ToRCH stand for (for infectious teratogens)?

A

toxoplasma
rubella
CMV
herpes

59
Q

what are some of the genetic teratogens?

A 
turner's syndrome
down's syndrome
structural changes (deletions of genes, segments of chromosomes)
60
Q

in what stage of pregnancy is the foetus most sensitive to teratogens?

A

weeks 3-8

61
Q

what are the three factors that constitute to the risk of teratogenesis

A
  1. Exposure during critical periods of development
  2. Dosage of drug/chemical/factor
  3. Genetic constitution of embryo ie some more susceptible than others at equivalent doses etc

Respiratory system (38 decks)

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