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embryology > embryology exam 2 > Flashcards

embryology exam 2 Flashcards

1
Q

describe the development of the mesodermal germ layer and its division into paraxial, intermediate, and lateral plate mesoderm

A

epiblast –> bottle cells and spread laterally to form a layer between ectoderm and endoderm
paraxial: thick column closest and parallel to the notochord
intermediate : narrow column on other side of paraxial than notochord
lateral plate: thin plate lying next to the intermediate

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2
Q

what are the fates of each mesoderm layer

A

paraxial: segmented into somites
intermediate: urogenital system (kidney, gonads)
lateral plate: forms lining of body cavities and mesoderrm of most internal organs as well as limbs

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3
Q

describe the two mechanisms involved in somitogenesis

A

wavefront: increase in FGF-8 stimulates mitosis in mesenchymal cells in posterior primititve streak
increase in retinoic acid in the anterior opposes action of FGF-8, balance of retinoic acid and FGF-8 result in cellular determination towards somitogenesis. Mesp-2 present

segmentation clock: molecules in Notch expressed in oscillating expression on a time line. lunatic fringe: concentrated at future anterior border of somite, c-hairy: future posterior border, cells at anterior will express Eph A (receptor) and posterior cells will express Eph B (ligand) which will allow fissure between adjacent somites

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4
Q

difference between somitomere and somite

A

somitomeres become somites which are more dense blocks of mesoderm that form along the notochord

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5
Q

what is the relationship of ephrin B, Wnt-6, snail, and paraxis to somite formation?

A

dorsal somites release Wnt-6 which activates paraxis which inhibitis snail expression converting the mesenchymal cell to an epithelial cell = somitocoel formation

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6
Q

relate Shh, noggin, Pax1, and Pax9 to the formation of the sclerotome

A

notochorde releases Shh and noggin which activate Pax1 and Pax 9 genes in ventral part of somite which forms sclerotome

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7
Q

list the derivatives from the final subdivisions of the somites

A

dermomyotome: dorsal lateral somite, becomes axial dermis and skeletal muscle
syndetome: cells between myotome and scleretome become tendons
scleretome: ventral medial somite, becomes vertebral column

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8
Q

list the factors involved in the formation of the intermediate mesoderm and list the derivatives

A

BMP + activin (Hox-4 and Hox-11 contribute to cranial and caudal extent)
derivatives: pronephros and mesonephros aka. kidney

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9
Q

differentiate between the intraembryonic coelom and the extraembryonic coelom

A

intraembryonic coelem is made from the lateral plate mesoderm and becomes the pericardial cavity
extraembryonic coelom is the embryonic sac

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10
Q

distinguish between somatic and splanchnic mesoderm

A

divded by the intraembryonic coelem

somatic: below/ventral to the endoderm; bones, ligaments, connective tissue, blood vessels
splanchnic: above/dorsally the endoderm; forms heart, visceral pericardium, blood vessels, smooth muscle of GI and respiratory

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11
Q

describe the formation of the lateral plate mesoderm and distinguish between the somatopleaure and the spanchnopleure

A

somatopleaure: inside the tube mesoderm + endoderm
splanchnopleaure: outside the tube mesoderm + ectoderm

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12
Q

describe the early formation of the heart

A

cells migrate through primitive streak: anterior = outflow track, middle= ventricles, posterior= atria. which all form the cardiac crescent
cardiac tubes form from the crescent and fuse: outer layer= myocardium, inner layer= endocardium.

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13
Q

list the genes important in early heart formation

A

Nkx2-5, MEF2, GATA4

expressed by cells of cardiac crescent

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14
Q

what is the secondary heart field

A

splanchnic mesoderm

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15
Q

which signaling factor is necessary for the formation of endoderm

A

nodal

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16
Q

describe the relationship of the expression of nodal and FDF-4 to the establishment of the anterior-posterior gradient

A

high nodal= anterior

low nodal + FGF-4 = posterior

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17
Q

describe the role of Cdx-2 in the formation of the hindgut and foregut

A

Cdx-2 is expressed in the posterior gut- promotes hindgut development and supresses formation of anterior gut structures

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18
Q

describe the relationship of Shh and BMP-4 in the formation of the anterior and posterior intestinal portals

A

expression of Shh followed by BMP-4 in posterior intestinal portal
expression of Shh in anterior intestinal portal

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19
Q

list each of the three major circulatory arcs in the 4 week human embryo and the components and function of each

A

vitelline arc: carries blood from embryo to yolk sack and back
allantoic arc: umbilical, nurishment, waste disposal, and blood oxygenation
embryonic arc: aorta, veins, atrium, ventricle

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20
Q

list and describe the four extraembryonic tissues and the germ layers fromwhich they are derived

A

amnion: inner cell mass, ephiblast derivative
yolk sac: inner cell mass, hypoblast derivitave
chorion: fetal maternal interface
allantois: inner cell mass, interfaces with placenta via umilical chord

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21
Q

list the two trophoblastic derivatives that comprise the fetal-maternal interface

A

placenta

chorion

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22
Q

explain the function of the amnion

A

buffer against mechanical injury, accomodates growth, allows normal movements, protects fetus from adhesions

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23
Q

describe the following conditions and indicate what circumstances these are often associated: hydramnios, oligohydramnios

A

hydramnios: excessive amniotic fluid >2000mL (normal = 500-1000 mL)related to esophageal atresia or anencephaly- gross defects of the head, inability to swallow
oligohydramnios: too little amniotic fluid <500 mL, associated with bilateral renal agenesis (absent kidneys) could be consequence of preterm rupture of amniotiv membrane

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24
Q

describe the development of the allantoic vessels and the relation of the allantois to the urinary bladder and the median umbilical ligament

A

develop in mesoderm of allantois, used for respiratory organ and urinary waste, forms urinary bladder and umbilical ligament

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25
Q

what tissue in the mature placenta directly interfaces with the maternal uterine connective tissue

A

chorion/chorionic platw

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26
Q

list and describe the layers from the amnion outward to the outer layer of the endometrium

A

amnion-chorionic cavity- chorionic plate- trophoblastic covering (outer cytotrophoblastic shell)

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27
Q

what is the fate of the decidua capsularis

A

overlies the embryo and its chorionic vesicle

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28
Q

describe/trace the maternal fetal blood flow pattern and indicate where the exchange of material occurs

A

maternal blood enters intervillous space from spiral arteries where materials are exchanges in the lacunae, the fetal capillaries in villi pick up the material, the maternal blood then returns to maternal veins in decidua basalis

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29
Q

describe fetal alcohol syndrom

A

excessive alcohol ingestion by mother leading to birth defects

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30
Q

describe the following pathological conditions and relate to the structure of the placenta: hydatidiform mole, placenta previa. what is the genetic basis for the hydatidiform mole?

A

hydatidiform mole: chorionic villi have nodular swellings like bunches of grapes and will not have vascularization, embryo is either absent or non viable; paternally derived: 46, XX

placenta previa: abnormal implantation site in uterine cavity, hemorrhge is common

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31
Q

list functions of placent

A

diffuse oxygen and CO2
diffuse foodstufss
excrete waste

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32
Q

compare the early placenta with the late placenta

A

early placenta: thick, low permeabiity, small surface are, miniscule total diffusion conductance

late placenta: thin, high permeability, large surface area, lare increase in placental diffusion

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33
Q

describe the oxygen pressure gradient (near end of pregnancy) and explain why adequate oxygenation can occur with such a low pressure gradient

A

p02 mother: 50 mmHg
pO2 fetus: 30 mmHg
diffusion pressure= 20 mmHg, which is low but adequate oxygenation can still occur because: fetal hemoglobin has a higher affinity for oxygen, fetal blood has 50% greater hemoglobin concentration than maternal, and Bohr affect

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34
Q

describe the Bohr effect and explain what is meant by the double Bohr effect

A

bohr affect: low PCO2 blood has higher affinity for oxygen. both mothers is high in CO2 and baby’s is low in PC02 so this is a double Bohr affect

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35
Q

describe the timing, method of secretion, targets, and effects of human chorionic gonaotropin

A

timing: measurable 8-9 days aftr ovulation, max at 10th-12th week of pregnancy
method of secretion: secreted by syncytial trophoblasts into maternal fluids
effects: prevents involution of corpus leteum, causes CL to increase secretion of progesterone and estrogens, increase CL growth, exerts interstitial cell-stimulating effects on tests of male fetus (causes testosterone production until birth)

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36
Q

describe each of the four theories of why mother’s immune system does not recognize the fetus as foreign tissue

A
  1. lack of expression of major histocompatibility antigens by placenta components
  2. paralysis of mother’s immune system during pregnancy
    3 . decidual immune barrier
  3. inactivation of mother’s immune system components by molecules formed on fetal placenta surface
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37
Q

infectious agents that result in birth abnormalities

A

rubella, cytomegalic inclusion disease, herpes simplex, vricella-zoster, influenza, mumps

38
Q

effects of thalidomide on birth abnormalities

A

thalidomide: limb defects, ear defects, cardiovascular anomalies

39
Q

causes and symptoms of neotatal respiratory distress syndrome, hydrops, and eclampsia

A

neonatal respiratory distress syndrome: immaturity of the lungs due to premature birth
hydrops: accumulation of edema fluid in fetus during intrauterine growth, until recently most common cause was immune: hemolyric anemia (blood group incompatibility) ; nonimmune: cardiovascular defects such as congenital cardiac defects and arrhythmias as well as turner syndrome

preeclampsia: pregnancy induced hypertension, persistance blood pressure of 140/190, weight gain and edema
eclampsia: extremely serious, extremely high blood pressure, grand mal seizures or coma

40
Q

prematurity and fetal growth restriction is the second most common cause of neonatal mortality. list major risk factors of prematurity

A

preterm premature rupture of placental membranes
intrauterine infections
uterine, cervical, and placental structural abnormalities
multiple gestation

41
Q

describe the timing, method of secretion, targets, and effects of estrogen

A

timing: highest toward end of pregnancy
secreted by syncytiotrophoblast cells in placenta
functions: uterine enlargement, breast enlargement, growth of breast ductal structure, enlargement of maternal external genitalia, relaxation of pelvic ligaments

42
Q

describe the timing, method of secretion, targets, and effects of preogesterone

A

secreted early in small quantities by corpus luteum and large quantities by placenta
functions: causes decidual cells to develop in the endometrium, decreases contractility of pregnant uterus, increases secretions of fallopian tubes and uterus, may work with estrogen to prepare breasts for lactation

43
Q

describe the timing, method of secretion, targets, and effects of human chorionic somatomammotropin

A

secreted by placenta begining in 5th week of pregnancy
functions: causes decreased insulin sensitivity and decreased utilization of glucose by mother, general metabolic hormone

44
Q

teratology

A

“the study of monsters”, study of confenital malformations

45
Q

teratogen

A

agent that produces birth defects

46
Q

malformation

A

primary errors of morphogenesis

47
Q

disruption

A

disturbance in otherwise normal morphogenetic processes

48
Q

deformation

A

disturbances in otherwise normal morphogenetic processes and are typically caused by abnormal biomechanical forces such as uterine constraint

49
Q

dysplasia

A

abnormality of a tissue due to an abnormal intrinsic developmental process

50
Q

sequence

A

series (cascade) of events triggered by one initiating factor

51
Q

syndrome

A

a group of malformations of different structures due to a single primary cause but acting though multiple developmental pathways

52
Q

association

A

a group of anomalies seen in more than one individual that cannot yet be attributed to a definitive cause

53
Q

critical period

A

embryos are more susceptible to agents or factors causing abnormal development, between weeks 3 and 8

54
Q

describe the source of dermal cells in various parts of the skin: dorsal , ventral , lateral, cranial, anterior neck, limb

A

dorsal: mesenchyme from dermatome
ventral and lateral: mesenchyme from lateral plate mesoderm
cranial and anterior neck: mesenchyme mostly from cranial neural crest
limb: lateral plate mesoderm

55
Q

describe the signaling pathways leading to the differentiation of dermal cells

A

ectoderm releases Wnt which stimulates mesenchymal cells to develop tight junctions and become dermal cells

56
Q

compare characteristics of dermal cells and mesenchymal cells

A

dermal cells are loosely aggregated, interconnected by tight junctions, secrete thin watery matrix rich in glycogen and hyaluronic acid

57
Q

describe how recombination experiments between mesoderm and ectoderm, demonstrate instructive induction

A

instructive induction: dermis influences the development of epidermis and the derivitives and a reciprocal influence by the epidermis on the dermis
this was shown by separating them in experiment and neither of them differentiated

58
Q

list commonalities in the development of epidermal derivatives

A

(hair, nails, mammary glands)
involve ectodermal-mesodermal interactions and inductions
begin as epidermal downgrowths into mesenchyme
ectoderm contributes to: hair follicle, hair shaft, sebaceous glands, nails, eponychium, hyponychium, secretory ducts and duct components
mesenchyme contributes to hair papilla, outer hair follicle, and arrector muscles

59
Q

describe the adult hair cycle including the specific stages: anagen, catagen, telogen, and exogen

A

anagen: hair is actively growing (5-6 years)
catagen: (1-2 weeks) hair follicle regresses to only a fraction of its original length
telogen: (5-6 weeks) hair stops growing
exogen: hair is shed

60
Q

explain the importance of hormones in the development of mammary glands

A

estrogen: stimulates duct growth
progesterone: stimulate formation of secretory alveoli
prolactin: milk, protein, and fat synthesis
oxytocin: milk letdown

61
Q

describe the mesenchymal origin of each major part of the skeleton

A

mesodermal sclerotomes: vertebral column, ribs, sternum
lateral plate mesoderm: limb bones, girdles
head mesoderm: calcaria and base of skull
neural crest: facial bones

62
Q

differentiate the Hox gene boundaries for the different regions of the vertebral column

A 
occipital-cervical boundary: Hox 3
cervical-thoracic boundary: Hox6
Attached-floating ribs boundary: Hox9
thoracic-lumbar: Hox10
lumbar-sacral: hox 11
sacral-coccygeal: Hox13
63
Q

describe results of experiments involving Hox gene knockouts (single gene, hox 10 paralog, hox 11 paralog, mutation of hox gene)

A

single Hox gene knockout: minor morphological effects
Hox10 paralog knock out: ribs form on all the lumbar and sacral vertebrae
hox 11 paralog knockout: sacrum doesnt form
mutant in hox gene: minor defect

64
Q

describe the origin of the sternum

A

derived from lateral plate mesoderm, arises as a pair of cartilaginous bands

65
Q

describe the origin of the clavicle

A

arise from neural crest, follows intramembranous pathway, one of the first bones to become ossified

66
Q

describe/compare the subdivisions of the developing skull

A

neurocranium: surrounds the brain
viscerocranium: surrounds oral cavity and pharynx and upper respiratory
occipital sclerotomes: base of occipital bone

67
Q

describe the generalized neurocranium/chondrocranium

A

cartilaginous: part of occipital, sphenoid, thmoid, parts of temporals
membranous: part of occipital, parietal, frontals, part of temporal

68
Q

describe the generalized viscerocranium and the bones that develop from the viscerocranium

A

cartilaginous: pharynggeal arch I- meckels cartilage, malleus, incus; oharyngeal arch II- reichert’s cartilage, stapes, styloid
membraneous: part of temporal, zygomatic, maxillary, nasal, lacrimal, palantine, vomer, pterygoid plates, mandible, tympanic ring

69
Q

define fontanelle

A

intersections between sutures where more than two bones meet, occupied by connective tissue

70
Q

common pathway (bone/cartilage differentiation)

A

N-cadherin promotes mesenchymal cell condensation
TGF-beta stimulates synthesis of fibronectin and N-CAM
agreggated state of mesenchymal cells is stabilized

71
Q

membranous bone pathway

A

Runx-2 and Osx

mesenchymal cells differentiate into osteoblasts

72
Q

permanent cartilage pathway

A

mesenchymal condensation forms chondroblasts
sox-9 causes chondroblasts to secrete collagen II and catilage matrix, sox-9 is continually expressed in permanent cartilage

73
Q

endochondral bone pathway

A

Runx-2, ihh, and BMP-6 induce this cartilage to undergo hypertrophy
hypertrophic cartilage cells secrete bone proteins and vascular endothelial growth factor
invading blood vessels erode the hypertrophic cartilage and bring in osteoblasts to replace cartilage with bone

74
Q

describe each stage in the differentiation of skeletal muscle tissue

A

myogenic cells –> myoblasts –> myotubes –> muscle fibers

75
Q

differentiate between primary and secondary myotyubes

A

primary: formed by fusion of earliest myoblasts, dofferentiation occurs before innervation
secondary: smaller than primary, formed later, presence of axons may be necessary for them to form,

76
Q

describe the role of satellite cells

A

fuse with muscle fiber to provide growth, function as stem cells, replace damaged muscle

77
Q

describe the role/function of each of the following myogenic regulatory factors: Myf-5, Pax-3, Pax-7, FGF, TGF-beta, MyoD, Myogenin, and Myf-6

A

FGF and TGF-beta: maintain myogenic cells in labile state
MyoD: able to convert non-muscle cells to cells capable of expressing muscle proteins
Pax-3, Pax-7 and Myf-5: can separately activcate MyoD causing myogenic cells to become myoblasts
Myf-6: leads to expression of myofiber genes

78
Q

adult structures that develop from each region of the pentapartite brain

A

telencephalon: paleocortex, corpus stiatum, neocortex
diencephalon: epithalamus, thalamus, hypothalamus, infundibulum
mesencephalon: tectum, tegmentum, cerebral peduncles
metencephalon: cerebellum, pons
myelencephalon: medulla

79
Q

describe the stages of the neural tube wall from that of a simple cuboidal epithelium to a stratified epithelium

A

early neural epithelium: simple cuboidal
neural plate: simple columnar epithelium
early neaural tube wall: pseudostratified epithelium

80
Q

describe and explain the importance of the orientation of the metaphase plate during proliferation of cells within the neural tube

A

if the plate is perpendicular to the neural tube, two resulting daughter cells will remain proliferative
if the plate is parallel with the neural tube only the one closest to it will remain proliferative while the other will express notch recepter, be postmitotic, move to the external limiting membrane and become a neuroblast

81
Q

describe the hierarchy of basic cell lineages in the development of the nervous system and note when mitosis ceases in each lineage and differentiation begins

A

neuroepithelium= initial epithelial layer of neural tube
bipotential progenitor cell= cell is restricted to becoming neuronal lineage progenitor or glial lineage progenitor
neuronal lineage cell: develope into neurons, postmitotic
glial lineage cells: have a number of paths leading to type of glial cells

82
Q

describe effects of following expreiments:
grafting a second notochord
removing notochord
slit neural plate on one side of the floor plate

A

grafting an extra notochord near the neural tube induces a secondary floor plate
in the absence of a notochord, a very incomplete floor plate forms and nerve fibers exit from multiple sites around the spinal courd
slitting the neural plate on one side of the floor plate removes the wall of the neural tube from the influence of the notochord, allowing the disorganized exit of nerve fibers from that part of the spinal cord

83
Q

describe the signaling pathways and factors that establish the dorsal-ventral axis of the developing neural tube. what roles do the notochord and non-nervous ectoderm play

A

ventral signaling: notochord releases sonic hedgehog to form the floor plate, floor plate releases sonic hedgehog to form motorneurons

dorsal: ectoderm flanking the neural plate uses BMP to induce snail-2 in future neural crest and later to maintain pax-3 and pax-7 to create a dorsalizing effect which is suppressed by shh from floor plate to supress dorsalizing effect in the basal plate

84
Q

describe the relationship between rhombomeres, cranial nerves, and pharyngeal arches. which pharyngeal archees are associated with which cranial nerves

A

cranial nerves mostly supply structures derived from the pharyngeal arches
first pharyngeal arch: Cranial nerve V- rhombomere 2 and 3 joins 2
second arch: cranial nerve VII- rhombomere 4 and axons from 5 join 4
third pharyngeal arch: CN IX- rhombomere 6 and axons from 7 join 6

85
Q

how is the segmented nature of spinal nerves related to the somitic mesoderm pattern

A

it is segmented like somitic meso derm because motor neurons can penetrate the antior but not posterior mesoderm of somites

86
Q

what is the role of isthmis organizer and what signaling are involved

A

signaling center:
principal signaling molecule = FGF-8 (FGF-8/Wnt-1 induce expression of En-1, En-2, pAX-2, pAX-5 which all decrease away from isthmic organizer)
organizes and polarizes dorsal midbrain and cerebellum

87
Q

how does shh determine the midbrain dorsoventral axis

A

shh restricts Pax-7 expression and similar molecules
pax-7 forms alar plate
pax-6 eye formation and inhibits en-1 and vice versa which creates diencephalic-mesencephalic border

88
Q

what role do prsomeres P1-P3 plat in forebrain patterning

A

p1-p3 define the diencephalon

p2-p3 define dorsal and ventral thalamus

89
Q

describe steps and outgrowth of motorneuron and compare with sensory neuron what are growth cones? how do environmental factors afftect growth? what role do netrins and semaphorins play? what are boundary caps and what role do they play in axon growth

A

motor neurons grow out from the motor neuroblasts in the basal plate of spinal chord
cell bodies of sensory neurons are derived from neural crest cells and form snesory spinal ganglia and axons grow toward spinal cord and periphery
growth cone: expanded region of cytoplasm with filopodia which advance via extension/resorption via actin filaments
environmental factors: chemoattraction, contact attraction, chemorepulsion, contact repulsion
netrins : attractant
semaphorin: repulsive
boundary caps maintain spearation betwen CNS and PNS

90
Q

list cues involved in axon guidance

A

caudal half of somite, fibronectin and laminin, integrins, cadherences

91
Q

describe steps in the formation of synaptic junction

A

axon outgrowth ceases
neuron preps to release neurotransmitter molecules: synaptoc vesicles fill with ACh
muscle fiber prepares for signal transduction: ACH receptors become concentrated in postsynaptic folds, ACH-esterase accumulates in basal lamina

embryology (3 decks)

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