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Anatomy > Early Development II > Flashcards

Early Development II Flashcards

1
Q

Embryonic folding

A

. Longitudinal and transverse folding of embryonic disc

. Establishes recognizable vertebrate body plan

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2
Q

Longitudinal folding

A

. Rapid differential growth of axial structures causing cranial and caudal end to fold ventrally
. Cephalic rim folds ventrally and caudally for ventral surface of face, neck and chest
. Oropharyngeal membrane relocated to site of mouth
. Cardiogenic region and septum transversum carried into future thoracic region
. Caudal rim folds ventrally and cranially carrying cloacal membrane and connecting stalk onto embryo’s ventral surface
. Connecting stalk contacts neck of yolk sac

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3
Q

Septum transversum

A

. Thickened band of mesoderm that contributes to thoraco-abdominal diaphragm

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4
Q

Transverse folding

A

. Lat. edges of embryo fold ventrally and meet in midline where they fuse at cranial and caudal ends and proceed toward site of future umbilicus
. Midline fusion or endoderm and splanchnic mesoderm creates gut tube
. Lat. folds constrict neck of yolk sac creating Vitelline duct that contacts connecting stalk
. Midline fusion of somatic mesoderm and ectoderm creates definitive intraembryonic coelom/body cavity

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5
Q

Gut tube

A

. Foregut and hindgut: blind pouches
. Hindgut communicates w/ allantois
. Midgut: communicates w yolk sac

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6
Q

Folding causes embryo to be enveloped in ____

A

Amniotic cavity

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7
Q

Rupture of ____ and ___ opens gut tube to amniotic cavity at both ends

A

. Oropharyngeal and cloacal membranes

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8
Q

Late embryonic period

A

. Weeks 5-8
. Most active organogenesis
. By week 9 heart and limbs formed and foundation or other systems established

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9
Q

Fetal period

A

. Weeks 9-38
. Organ system maturation and growth
. Malformations unlikely

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10
Q

Fetal viability starts at ____

A

22 weeks

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11
Q

When does growth in length occur?

A

Months 3-5

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12
Q

T/F fetal crown-rump length is closely assoc. w/ fetal age

A

T

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13
Q

Length of body and limbs inc. relative to ____

A

Head size

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14
Q

Inc. weight occurs most rapidly when?

A

Months 8-9

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15
Q

What occurs in week 2 in regards to placenta?

A

. Syncytiotrophoblast proliferates and develops lacunae to form lacunae network and erodes uterine glands w/in endometrium releasing glycogen-rich secretions and maternal serum into lacunar network
. Vascularization and secretory activity in endometrium inc. (decidual rxn)
. Endometrium referred to as decidua

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16
Q

Decidua

A

. Decidua basalis: btw embryo and muscular uterine wall
. Decidua capsularis: separates embryo from uterine cavity
. Decidua parietalis: lines remainder of uterine cavity

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17
Q

Chorionic villi development

A

. Primary: finger-like folds of trophoblast (both layers) project into lacunae
. Secondary: extraembryonic mesoderm penetrates the villus core
. Tertiary: mesoderm core gives rise to blood cells and vessels that connect w/ developing vessels in embryo proper
. Villi bathed by maternal blood when maternal-placental circulation establishes

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18
Q

When does maternal-placental circulation occur?

A

8-10 week

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19
Q

Smooth chorion (chorion laeve)

A

. During 2nd month

. Villi on abembryonic (away from. Embryo) side of the chorion degenerate forming this

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20
Q

Villous chorion (chorion frondosum)

A

. Portion of the chorion in contact w/ decidua basalis retains its villi
. Inc. in length and complexity throughout pregnancy

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21
Q

Intervillous space

A

. Lacunae enlarge and coalesce to form blood-filled intervillous space
. Lined by syncytiotrophoblast

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22
Q

Hydatidiform mole

A

. Trophoblastic hyperplasia in absence of viable embryo
. Complete mole contains only paternal chromosomes and lacks embryo
. Partial mole has triploid karyotype (from polyspermy) and a nonviable embryo
. Elevated hCG levels, proliferation and edema of chorionic villi, bleeding, and 1st trimester pre-eclampsia

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23
Q

Choriocarcinoma

A

. Malignant trophoblastic cancer

. 5% moles progress to this

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24
Q

Placental circulation

A

. Week 8: maternal blood in intervillous space via 100 spiral arteries
. Drained by endometrial veins
. Placental blood volume (150 ml) replaced 3-4 times per minute
. Capillaries w/in chorionic villi supplied w/ fetal blood by chorionic branches of umbilical arteries and drained by chorionic veins of umbilical veins
. Gas exchange occurs at placental membrane (chorionic villus wall)

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25
Q

Basal plate

A

. Maternal surface of placenta formed by decidua basalis and syncytiotrophoblast lining intervillous space

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26
Q

Chorionic plate

A

Fetal surface of placenta formed by villous chorion and chorionic vessels covered by amnion

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27
Q

Anchoring villi

A

. Specialized villi attach chorionic plate to basal plate

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28
Q

Cotyledons

A

. Occurs in months 4-5
. Protrusions of decidua basalis subdivide intervillous space into 15-25 segments
. Placental septae incomplete allow blood flow here

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29
Q

Placenta at birth

A

. Placenta weighs 500g and covers 30% of internal uterine surface

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30
Q

Placental membrane in early pregnancy

A

. Formed by trophoblast, fetal CT, and blood vessel endothelium
. Restricts broad range of substances from entering fetal circulation

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31
Q

Placental membrane in later pregnancy

A

. 2 layers: syncytiotrophoblast and endothelium to allow more substances to cross into fetal circulation

32
Q

Beneficial substances that freely cross placental membrane

A 
. Gasses
. Electrolytes 
. Glucose
. Nutrients
. Fetal waste products
. Maternal and fetal rbcs 
. Maternal serum proteins 
. Steroid hormones 
. Antibodies
33
Q

Potentially harmful substances hat cross placental membrane

A 
. Viruses
. Environmental toxins 
. Pharmaceuticals 
. Bacteria and parasites
. Maternal antibodies (anti-Rh)
34
Q

Substances that can’t cross placental membrane

A

.most bacteria
. Large lipid molecules
. Protein hormones
. Some pharmaceuticals

35
Q

Erythroblastosis Fetalis

A

. 2nd Rh+ child will have severe hemolytic anemia with mothers that do not have Rh factor w/o preventative measures
. 1st chid will be fine

36
Q

Placental endocrine functions

A

. Placenta produces hormones crucial to maintenance of pregnancy and fetal growth and development
. HCG, human placental lactogen (fetal growth hormone), steroids hormones, and progesterone

37
Q

Placenta previa

A

. Implantation on lower uterine wall causing placenta to expand and cover the internal os (opening) of the cervical canal
. Causes vaginal pleading in late pregnancy
. C-section performed to avoid life-threatening bleeding

38
Q

Placenta accreta/increta/percreta

A

Abnormal implantation into (accreta/increta) or through (percreta) myometrium (muscular uterine wall)
. Can cause placental retention, massive hemorrhage, and/or uterine rupture
.Prior C sections inc. risk for this
. Life threatening

39
Q

Primitive umbilical ring

A

, opening at conclusion of gastrulation on ventral embryo surface

40
Q

Structures passing through primitive ring

A

. Connecting stalk
. Allantois: narrow yolk sac diverticulum w/in connecting stalk that communicates w/ hindgut
. Vitelline duct: connects yolk sac and midgut

41
Q

Primitive umbilical cord formation

A

. Expansion of amniotic sac compresses and binds structures inside primitive umbilical ring
. Bound w/ sheath of amniotic membrane

42
Q

Formation of umbilical vessels

A

. Weeks 2–3
. Vasculogenesis w/in extraembryonic mesoderm of the yolk sac extends into connecting stalk
. Gives rise to umbilical arteries and umbilical vein

43
Q

Umbilical vessels

A

. Connected to vessels w/in embryo to eastablish fetal-placental circulation
. Embedded in Wharton’s jelly
. Umbilical arteries spiral around umbilical vein

44
Q

Umbilical abnormalities

A

. Abnormal coiling assoc. w/ abnormal amniotic fluid volume and other fetal anomalies
. Presence of single umbilical artery is sign of cardiovascular abnormalities

45
Q

Amniotic sac formation

A

. Week 8 amniotic sac has expanded to fill chorionic cavity
. Amnion fuses w/ chorion laeve to form amniochorionic membrane
. Uterine cavity disappears as amniotic sac grows
. Decidua capsularis and decidua parietalis fuse

46
Q

Amniotic fluid

A

. Composed of maternally-derived H2O, electrolytes, biomolecules, and fetal waste products
. Supports fetus, prevents fetal membranes from adhering to it
. Permits movement
. AIDS in temp. Regulation

47
Q

How is amniotic fluid produced?

A

. Direct transfer from maternal circulation and excretion of urine by fetus

48
Q

Fluid resorption in fetus

A

. Occurs via fetal gut

. Fluid swallowed, absorbed into bloodstream across gut wall, and returned via placenta to maternal circulation

49
Q

How much amniotic fluid at term?

A

1 L

50
Q

Oligohydramios

A

. Low. Amniotic fluid volume
. Due to fetal kidney abnormalities
. Inc. pressure on fetus causes additional abnormalities (Potter syndrome)) and hypoplasia

51
Q

Polyhydramnios

A

Excess amniotic fluid caused by maternal diabetes or fetal abnormalities in gut or CNS

52
Q

Amniotic band syndrome

A

. Occurs when bands of amniotic membrane constrict counter parts of fetus causing amputation or deformation of structures

53
Q

Premature membrane rupture

A

. Leads to oligohydramnios and premature labor

54
Q

Dizygotic twins

A

. 2 ova fertilized and implanted separately
. Each twin normally has separate placenta, chorion, and amnion
. Placentas or membranes may fuse
. Placental fusion may result in rbc exchange and genetic mosaicism

55
Q

Monozygotic twins

A

. Single fertilized ovum splits into 2 embryos

. Organization of fetal membranes determined by stage at when splitting occurs

56
Q

2-blastomere through morula separation for twins

A

. Resulting blastocysts implant separately

. Each twin forms a separate placenta, chorion, and amnion

57
Q

Early blastocyst separation for twins

A

. Splitting forms 2 inner cell masses w/in common trophoblast
. Twins have common chorion but separate amnions

58
Q

Bilaminar germ disc separation in twins

A

. Share single placenta, chorion, and amnion

59
Q

Twin-twin transfusion syndrome

A

. Occurs when placental vascular anastomoses preferentially direct blood to 1 twin
. Results in gross size disparity
. Death of both twins occurs in 50-70% of cases

60
Q

Congenital abnormalities

A

. Structural, functional, metabolic, or behavioral disorders present at birth
. Clinically significant anomalies present in 3% of live births
. Leading cause of infant mortality in US and major cause worldwide
. Cause unknown in 50% of cases, 15% genetic factors, 10% environmental factors, 25% combo factors
. Twinning <1% anomalies

61
Q

Malformation

A

. Absence or abnormal configuration of structure due to abnormal processes of development
. Occurs in weeks 3-8 of development

62
Q

Disruption

A

. Morphological change in normal structure by mechanical forces
. Most common in musculoskeletal system

63
Q

Dysplasia

A

Abnormal organization of cells into tissues

64
Q

Syndrome

A

. Group of anomalies occurring together that have common specific etiology
. Often genetic

65
Q

Association

A

. Non random co-occurrence of a group of anomalies whose etiology is unknown

66
Q

Prenatal testing

A

. Performed when risk factors inc. likelihood of genetic or other congenital anomalies

67
Q

Preconception screening

A

. During IVF procedures blastomere can be removed for genetic screening prior touterine insertion

68
Q

Ultrasound screening

A

. Reveals structural abnormalities of the embryo/fetus and placenta beginning at implantation

69
Q

Chorionic villus sampling (CVS)

A

. Biopsy of chorionic tissue can diagnose genetic abnormalities
. Early as 8 weeks
. Carries higher risk of miscarriage than amniocentesis

70
Q

Amniocentesis

A

. Needle aspiration of amniotic fluid provides fetal cells for genetic analysis
. Tests for presence of alpha-fetoprotein assoc. w/ neural defects and Downs

71
Q

Teratology

A

. Study of congenital anomalies

72
Q

Teratogens

A

. Agents that disturb development of an embryo/fetus causing congenital anomalies and/or death

73
Q

Principles of teratology

A

. Susceptibility to teratogens depends on genotype of conceptus and manner in which genotype interacts w/ environment
. Susceptibility varies w/ developmental stage at time of exposure
. Act in specific ways on developing cells and tissues o cause abnormal embryogenesis
. Abnormal development inc. as dose/duration of exposure inc.
. Abnormal development includes death, malformation, growth retardation, and functional disorder

74
Q

Resistant period (weeks 1-2)

A

. Conceptus will die from exposure or survive unharmed (all or nothing)

75
Q

. Sensitive period

A

. Weeks 3-8
. Max susceptibility to teratogens
. Corresponds to embryonic period and period of organogenesis

76
Q

Lowered susceptibility period

A

. Weeks 9-38

. Exposure may cause altered function and minor anomalies but less is likely to cause significant malformations

77
Q

TORCH infections

A

. Toxoplasma, rubella, cytomegalovirus, herpes, HIV, Zika
. Prenatal exposure can cause miscarriage, stillbirth, retinal damage, microcephaly, hydrocephalus, encephalomyelitis, and cerebral calcification

Anatomy (49 decks)

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