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respiratory system year 1 > respiratory embryology > Flashcards

respiratory embryology Flashcards

1
Q

what is classed as the pre-embryonic phase

A

0-3wks

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2
Q

what is classed as the embryonic phase

A

4-8wks most organ systems begin to develop

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3
Q

what is the foetal phase

A

9-40wks organ systems continue to develop and mature

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4
Q

when does the development of some systems continue into

A

postnatal childhood adolescence - some systems don’t develop fully until this point

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5
Q

define spermatogenesis

A

formation of the sperm from spermatogonium meiosis in sperm doesnt begin until puberty can be X or Y

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6
Q

define oogenesis

A

formation of the egg from oogonium meiosis I has already occurred in girls before they are born meiosis II continues at puberty to produce 4 cells all are X

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7
Q

how many chromosomes do the spermatogonium and oogonium have

A

46

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8
Q

what is important about the genetics of each sperm and ovum

A

they are all genetically unique even though they come from the same original spermatogonium/oogonium this explains why siblings are similar but not identical as they share a lot of the same genetic material but not all of it

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9
Q

what occurs during fertilisation

A

several sperms surround the ovum only one penetrates pronucleus of the sperm enters (only the genetic material) and fuses with the pronucleus of the ovum to give a diploid cell called the xygote

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10
Q

what occurs during week 1 of the pre-embryonic phase

A

xygote is formed divides to form blastocyst blastocyst moved through uterine tube to reach the uterine cavity

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11
Q

xygote to morula process

A

xygote is the first cell in the body it is diploid and genetically unique mitochondria and cell organelles are inherited from the mother cell divides by mitosis and a solid ball of cells - morula - is formed

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12
Q

why are mitochondria and cell organelles inherited from the mother

A

cytoplasmic organelles from the sperm dont enter the ovum

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13
Q

from which parent are mitochondrial diseases inherited

A

the mother can only be passed on by females but males can inherit them e.g. Leber’s hereditary optic neuropathy; Leigh syndrome

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14
Q

morula to blastocyst process

A

the number of cells and size increases getting nutrition to the central cells becomes more difficult the blastocystic cavity develops and cells accumulate at one end to form an inner cell mass the outer lining of the cells is called the trophoblast

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15
Q

what is the trophoblast responsible for forming

A

placenta amniotic sac etc

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16
Q

what is the uterus mainly made from

A

smooth muscle the lining is called endometrium - controlled by hormones

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17
Q

movement through the uterine tube to reach the uterine cavity

A

the dividing xygote/morula/blastocyst requires healthy ciliated epithelium in the fallopian tube to move and reach the uterine cavity by day 5-6 the blastula has formed and reached the uterine cavity, ready to implant success of fertilisation is greatest when the ovum is located at the distal end of the uterine tube

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18
Q

how long does the first cell division take after fertilisation

A

36 hours successive divisions take less and less time

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19
Q

ectopic pregnancy

A

can occur with abnormal cilia function e.g. damage from infection/inflammation implants in the uterine tube rather than cavity

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20
Q

what occurs during week 2 of the pre-embryonic phase

A

implantation in the uterine endometrial layer placenta begins to develop from the chorion formation of bilaminar disc sacs, membranes and cord develop

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21
Q

process of implantation in the uterine endometrial layer

A

~7 days the blastocyst begins to burrow into the uterine wall the chorion plays an important role in the burrowing

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22
Q

trophoblast to chorion process

A

cells that form the outer cell mass is initially called the trophoblast it divides to form 2 layers and ultimately forms a chorion finger like processes develop (chorionic villi)

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23
Q

what is the role of the chorion

A

involved in the implantation process (chorionic villi) eventually forms part of the placenta secretes human chorionic gonadotropin (HCG)

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24
Q

define decidua basalis

A

part of the endometrium deep to the implanted conceptus

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25
Q

what is the role of HCG

A

helps maintain the endometrium maternal blood and urine levels of hCG increase till around 12wks of gestation

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26
Q

formation of bilaminar disc

A

the cells of the inner cell mass form a 2 layered flat disc called the bilaminar disc 2 cavities begin to form: amniotic sac (above) and yolk sac (below) the epiblast and hypoblast separate the amniotic sac and the yolk sac (epiblast closest to amniotic sac)

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27
Q

development of sacs, membrane and cord process

A

nourish the human conceptus amniotic cavity, chorionic cavity, allantoic cavity (accumulates waste) and yolk sac trachea and resp tree develop from yolk sac

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28
Q

what are the 3 main functions of the placenta

A

foetal nutrition transport of waste and gases immune functions develops from the chorion

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29
Q

describe the foetal surface of the placenta

A

smooth with the foetal blood vessels and end of the umbilical cord

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30
Q

describe the maternal surface of the placenta

A

decidua basalis of endometrium rough maternal blood vessels

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31
Q

when does the placenta mature

A

18-20wks

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32
Q

fraternal/dizygotic twins

A

2 ova released 2 sperms 2 separate zygotes 2 placentae different genetic makeups can run in families

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33
Q

identical/monozygotic twins

A

1 ovum 1 sperm 1 zygote initially which then divides into 2 and each cell develops into a different embryo same genetic makeup share 1 placenta (might not share amniotic and chorionic sac)

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34
Q

what occurs during week 3 of the pre-embryonic phase

A

formation of germ laers (gastrulation) formation of neural tube (neurulation) development of somites early development of CVS

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35
Q

what is the primitive streak

A

formed in the midline of the epiblast by the dipping in of cells (invagination) once the primitive streak forms, the axis of the embryo is formed i.e. head and bottom end, left and right side

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36
Q

gastrulation

A

formation of 3 germ layers which give rise to every tissue in the body epiblast cells migrate into space between epiblast and hypoblast layers cells then displace hypoblast 3 germ layers are formed TRILAMINAR DISC IS FORMED cells have now become specialised epiblast cells divide very rapidly

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37
Q

what are the 3 germ layers

A

ectoderm (top), amniotic cavity above mesoderm (middle) endoderm (bottom), yolk sac below

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38
Q

what forms from the ectoderm

A

skin, nervous system

39
Q

what forms from the mesoderm

A

muscle, bone, heart

40
Q

what forms from the endoderm

A

gut wall, respiratory system

41
Q

where are unspecialised cells found

A

in the yolk sac or amniotic cavity

42
Q

neurulation

A

gives rise to the brain and spinal cord notochord formation - solid tube of cells form

43
Q

process of notochord formation

A

ectoderm, mesoderm, endoderm formation of primitive streak cells sink down through ectoderm and mesoderm to form a solid tube notochord forms between endoderm and mesoderm neural plate forms in ectoderm notochord induces ectodermal cells in the midline to thicken forming the neural plate the neural plate sinks down forming 2 neural crests and a neural groove the crests come together to form the neural tube, lose connection with the ectoderm

44
Q

what is the nucleus pulposis a remnant of

A

the notochord

45
Q

what is the spinal cord formed from

A

the neural tube

46
Q

development of somites

A

neural tube induces the mesoderm to thicken mesoderm splits into 3 parts lateral plate mesoderm splits to form a somatic and splanchnic mesoderm (space between these is called the intraembryonic coelom) paraxial mesoderm splits up to form somites

47
Q

what are the 3 parts that the mesoderm splits into during the development of somites

A

paraxial mesoderm (closest to the neural tube) intermediate plate mesoderm lateral plate mesoderm (furthest from the neural tube)

48
Q

what do the 3 parts of the mesoderm become

A

paraxial –> somites intermediate –> urogenital system (kidneys and repro) lateral plate –> body cavity and coverings)

49
Q

what is week 4-8 of the pre-embryonic phase known as

A

embryonic period/ganogenetic period

50
Q

what occurs during week 4-8 of development

A

lateral folding of tube completes further development of somites

51
Q

lateral folding of the tube

A

begins in week 3 folds round laterally so gut tube is in the centre amniotic sac now surrounds the whole embryo yolk sac is inside

52
Q

what do the pleura form from

A

lateral plate mesoderm

53
Q

what does the tracheobronchial tree form from

A

endoderm

54
Q

what does the gap in the lateral plate mesoderm form

A

pleural cavity

55
Q

head and tail folding of the embryo

A

seen in mid sagittal sections

head fold forms as head becomes heavy

tail forms

all still surrounded by amniotic cavity

56
Q

further development of somites

A

each somite (paraxial mesoderm) divides into 3:

dermatome, myotome, sclerotome

these structures migrate but carry their innervation with them

57
Q

what forms from the dermatome

A

dermis of skin

each spinal nerve supplies one segment - dermatome

nerves can have more than one spinal nerve e.g. brachial plexus

58
Q

what forms from the myotome

A

muscle

59
Q

what forms from the sclerotome

A
60
Q

when does the heart start to beat

A

day 24

61
Q

how many pairs of somites form in the paraxial mesoderm

A

43 and these differentiate further

62
Q

what does the neck form from

A

pharyngeal arches

63
Q

define teratology

A

study of when things go wrong in development

64
Q

define teratogens

A

environmental factors that cause abnormal development

65
Q

congential rubella syndrome

A

caused by contraction of german measles when pregnant

cataracts, heart and brain defects

66
Q

maternal use of thalidomide

A

malformed limbs

crosses the placenta and interferes with angiogenesis

limb buds being formed suffer leading to short, flipper-like limbs with missing of super-numerary digits

67
Q

causes of abnormal development

A

unknown aetiology 60%

environmental 10%

genetic 10%

multifactorial 20%

68
Q

environmental teratogens

A

drugs - prescription or other

alcohol/tobacco

infectious agents (ToRCH - toxoplasma, rubella, cytomegalovirus, herpes)

others e.g. radiation

69
Q

genetic impacts on development

A

too many/few chromosomes: Turner’s syndrome (45X), Downs (trisomy 21)

structural change (gene deletions, segments of chromosomes)

causes: increased maternal age, damage from environmental factors)

70
Q

risk of teratogens

A

week 1-2: high risk of death, low risk from teratogens, no risk of malformations because risk of death is higher

weeks 3-8: period of greatest sensitivity to teratogens, can lead to major defects of organ systems

weeks 9-38: decreasing sensitivity to teratogens, more minor defects occur

71
Q

what are the 3 factors that the risk posed by a teratogen depends on?

A
  1. exposure during critical periods of development
  2. dosage of drug/chemical factor
  3. genetic constitution of embryo (some are more susceptible than others at equivalent doses)
72
Q

diagnosis of malformations

A

prenatal: blood (AFP), US scan (12wk anomoly scan), invasive tests (chorionic villus sampling, amniocentesis)
postnatal: hip stability, testes (descent), fingers and toes, hearing

73
Q

what does the folding of the embryo in week 3 give rise to

A

the primitive gut tube

gut tube forms from endoderm –> midgut and hindgut

trachea and lungs form from foregut

74
Q

when and where do the trachea and lungs form

A

week 4 from the ventral wall of the foregut

trachea is anterior to oesophagus

75
Q

respiratory primordium

A

starts as median outgrowth (diverticulum - the bud) - laryngotracheal groove - from the ventral part of the foregut

diverticulum becomes covered with mesoderm on the outside and enlarges to form trachea and lung buds

oesophagotracheal septum develops between oesophagus and trachea, completely separating them into trachea ventrally and oesophagus dorsally

76
Q

define fistula

A

an abnormal or surgically made passage between a tubular organ and the body surface OR between 2 tubular organs i.e. between 2 epithelialised surfaces

TOF (tracheoesophageal fistula) is a common congenital abnomality

77
Q

define atresia

A

a condition in which an orifice or passage in the body is (usually abnormally) closed or absent

e.g. oesophageal atresia and fistula

78
Q

from which layer do the visceral and parietal pleura develop

A

mesoderm

79
Q

development of pleural cavities and pleura

A

the developing lungs acquire a layer of visceral pleura from the splanchnic mesoderm

the thoracic wall is lined by a layer of parietal pleura derived from the somatic mesoderm

the gap between the parietal and visceral pleurae is called the pleuroperitoneal canals (these become the pleural cavities)

pleuropericardial folds form around the primitive heart, separating pleural cavities from pericardial cavity

the lung buds expand into the pericardioperitoneal canals - at this stage the canals are in communications with the peritoneal and pericardial cavities

80
Q

differentiation of lung buds (5 stages)

A

foetal; embryonic (0-4wks), pseudoglandualar, canalicular, saccular

postnatal: alveolar

81
Q

pseudoglandular stage

A

7-17wks

setup of all pulmonary structures excpt elements needed for gas exchange

82
Q

canalicular stage

A

17-27wks

the terminal bronchioles give rise to tubes that make up the respiratory part of the lung

differentiation of epithelium into type I and II pneumoncytes

83
Q

saccular stage

A

27-40wks

formation of alveolar sacs

alveolar sacs are progressively divided into smaller subunits leading to the formation of alveoli

84
Q

alveolar stage

A

32wks -8yrs

formation of alveoli from terminal sacs

about 95% adult-like alveoli are formed postnatally

alveoli enlarge

number of resp bronchioles (and aveolar ducts and alveoli) increase as lungs enlarge

by 8y/o, number of alveoli reaches adult number (~300mln)

85
Q

respiratory distress syndrome (RDS)

A

AKA hyaline membrane disease (HMD)

surfactant deficiency is a major cause of RDS

RDS affects 2% of neonates and makes up 30% of neonatal disease

86
Q

3 other congenital lung conditions

A

accessory lobes: L lung can have 3 lobes w/ 2 fissues (infrequent), R lung can develop accessory lobe alongside normal 3

lobe of axygos vein

agenesis of lung - lung doesnt develop, trachea pulled over to side of agenesis

87
Q

what 4 embryonic components does the diaphragm develop from (and what do these become in the diaphragm)

A

septum transversum –> central tendon

pleuroperitoneal membranes –> primitive diaphragm (front part)

dorsal mesentery of oesophagus –> median portion and crura of diaphragm

muscular ingrowth from lateral body walls –> peripheral parts of diaphragm

88
Q

where do the 3 tubular structures enter the diaphragm and what are these

A

IVC - T8

oesophagus - T10

aorta - T12

89
Q

where is the septum transversum initially located

A

initially located opposite C3-5 somites at wk3

migrates caudally during development of diaphragm

brings fown with it spinal nerves C3-5

root value of phrenic nerves = C3-5

90
Q

what are the 3 main defects of the diaphragm causing congenital abnormalities

A
  1. failure of the diaphragm to completely close during development
  2. herniation of the abdominal contents into the chest
  3. pulmonary hypoplasia
91
Q

define hernia

A

a bulge or protrusion of an organ through the structure or muscle that usually contains it

92
Q

what are 3 types of diaphragmatic herniae

A

posterolateral

anterior

central

93
Q

2 types of hiatal herniae

A

normally the haitus are present in the diaphragm - these can enlarge and structures can move through into areas where they shouldnt be

sliding hiatus hernia: stomach moves through oesophageal hiatus and becomes constricted

paraesophageal hiatus hernia - also known as rolling hiatus hernia, stomach rolls up nect to the oesophageal hiatus

respiratory system year 1 (25 decks)

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