Glossary of Embryology Exam I OUHSC Fall 2006

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ovum changes to multicellular adult organism is called
progressive acquisition of structural and biochemical specialization is called
genes are turned off during differentiation but are not turned off permamently, how was this proven?
dolly cloning, differentiated nucleus into egg making new embryo
example of differentiation with loss of pattern formation is known as what?
teratoma, lack of pattern formation
determining age based on time from last menstrual period is known as what? where would this be used?
gestational age, used clinically
determing age based on time from fertilization is known as what? this staging is used where?
Fertilization age, used in class
Day one is known as what?
cells undergoing differentiation at the proper time and in the proper location is what?
pattern formation
zygote cell nuclei is haploid or diploid?
What events occur during the 1st week of developement
cleavage and implantation
the extracellular layer, known as the zona pellucida is comprised of what?
the cells that are formed by the rapid mitotic divisions during cleavage are known as what?
The morula stage has approximately how many cells?
The morula is completed by what day?
day 3
What is the process by which blastomeres form tight junctionsbetween outer blastomeres?
What is formed 4 days after fertilization
blastocyst formation
what two subdivisions are formed in initial blastocyst?
extraembryonic and embryonic cells
Embryonic cells of the blastocyst are forming what in the first week?
inner cell mass cells
Extraembryonic cells of the blastocyst are forming what in the first week?
trophoblast cells
Compaction is what?
formation of tight junctions between outer blastomeres
The inner cell mass cells are formed from embryonic cells of the early blastocyst and are collectively also known as what?
the loss of the zona pellucida is known as what?
The process of hatching forms what?
floating blastocyst
Up to the point of implantation what has occurred within the fertilized ovum?
fertilization, cleavage, morula formed, compaction, blastocyst formation, hatching (formation of the floating blastocyst)
What cavity is formed after compaction?
Blastocyst cavity
What day is the floating blastocyst formed
6th day
Where is the appropriate site of implanation?
intrauterine (superior part of body of uterus, posterior wall usually) known as the endometrium
The trophoblast splits to form what 2 layers
cytotrophoblast and syncitio trophoblast
Of the two layers formed by the trophoblast which layer gives rise to the other?
cytotrophoblast gives rise to tehe syncitotrophoblast
What important hormone is formed that is the basis for early pregnancy tests, and what produces this?
human chorionic gonadotropin, syncitiotrophoblast
The syncitiotrophoblast has what functional purpose in implantation
haghly invasive into endometrium using hydrolytic enzymes and proteases
What occurs in the inner cell mass cells during the beginning of implantation?
delaminate to form hypoblast layer facing blastocyst cavity
Spontaneous abortion serves what purpose
natural screening of embryos
What are the implantation sites that are possible?
intrauterine, extrauterine (tubal, ovarian, and abdominal)
What are extrauterine implantations known as?
ectopic pregnancy
What is the most commin ectopic pregnancy, what causes this, and what might cuase this?
tubal, result of delayed transport of zygote, cuased by scarring (as seen in conflammatory disease)
embryonic stem cells are derived from what?
inner cell mass cells
Embryonic stem cells are said to be what, and this means what?
totipotent, they can differentiate into all types of adult cells, tissues, and organs
What is the difference between adult stem cells and embryonic stem cells?
ESC are pleuripotent, while adults are restricted potential
What are the events during second week of developement?
implantation is completed, formation of primitive uteroplacental circulation, formation of bilaminar embryo, and formation of extraembryonic membranes and cavities
What are the two basic functions of the uteroplacental circulation
provides means for developing embryo to recieve nutrients and get rid of
waste products, and forms primitve placenta
What is the name for the spaces that form within syncitiotrophoblast?
The lacunae fuse to form what network
lacunar network
What fuses with lacunar network and fills it?
maternal blood
what two layered structure forms early in the 2nd week from hypoblast?
bilaminar disk
What are the two layers of the bilaminar disk
epiblast and hypoblast
What cavities form after the formation of the bilaminar disc?
amniotic cavity (above) and primary yolk sac
What forms from the migration of hypoblasts around the lower cavity?
exocoelomic membrane
Hypoblasts give rise to what two layers that form the extraembryonic coelom
splanchnic extraembryonic mesoderm and somatic extraembryonic mesoderm
splanchnic extraembryonic mesoderm is associated with what?
yolk sac
somatic extraembryonic mesoderm is associated with what?
amniotic membrane, connecting stalk, and chorion
what forms the extraembryonic coelom or chorionic cavity
the splitting of the extraembryonic mesoderm, formed primarly from hypoblast (some may form from epiblast during gastrulation
the chorion foms what structure
fetal portion of placenta
what is the endodermally lined projection from yolk sac into the connecting stalk
the primary yolk sac becomes what after the completion of the
extraembryonic coelom and chorion
secondary yolk sac
What are the two cell types within the embryo
epithelial cells and mesenchymal cells
what cells are polarized with respect to enviorment and sit on top of extracellular matrix
epithelial cells
what cells are not polarized with respect to enviorment and reside within extracellular matrix
mesenchymal cells
What is the major process taking place at the beginning of the 3rd week that willchange the bilaminar embryo into trilaminar
what three germ layers are formed from the epiblast
ectoderm, mesoderm, and endoderm
What goes to form the outer layer, skin, nervous system
what goes to form the middle layer, muscle, heart, and skeleton
what goes to form the inner layer and lining of the GI tract
What does ectoderm form
outer layer, skin, nervous system
what does mesoderm form
middle layer, muscle, heart, and skeleton
what does endoderm form
inner layer and lining of GI tract
What is the primitive streak
thickened midline band of epiblast in caudal part of bilaminar disk
primitive streak is formed by the thickening of what?
epiblast layer
ingression of epiblast through primitve groove forms what
What forms mesoderm in gastrulation
ingression of epiblast through primitve groove
epiblast that ingresses through primitve groove and replaces hypoblast is what
What forms endoderm
epiblasts ingressing through the primitive groove, replacing hypoblasts
What are the five structures that can be seen, looking down onto epiblast in amniotic cavity
oropharyngeal membrane, primitive pit, primitive streak, primitive groove, and cloacal membrane
Gastrulatino begins about what time
beginning of 3rd week, 15th-16th day
what type of cells are migratory mesodermal cells
what type of cells form endoderm and ectoderm
what occurs to form notochord
migration of mesoderm along midline towards oropharyngeal membrane
notochord degenerates except where, and what does this eventually form
except between vertebrae, this forms nucleus pulposus
what is the process that forms the neural tube
what day does the notochord induce overlying ectoderm to form neural plate
day 18
what is unduction
the process by which one tissue alters the fate of an adjacent tissue
what process forms the neural plate
notochord induces overlying ectoderm to form neural plate
what is the primordium of the cns?
neural tube
what are the ways that mesoderm migrates during gastrulation
laterally to reach extraembryonic mesoderm, along midline to form notochord, dorsolaterally and cranially to form cardiogenic region
as the notochord lengthens what regresses
primitive streak
what might occur from a lack of regression of primitive streak
sacrococcygeal teratoma
neural tube is formed and closed by when
end of 4th week
closure of neural tube (neuropore) corresponds with what at the end of 4th week?
establishment of vascular circulation in neural tube
What cells form with the closure of the neural tube from neuroectoderm
neural crest cells
what occurs from incomplete closure of neuropores
neural tube defects
how can Neural tube defects be detected
ultrasound and alpha fetal protein found in amniotic fluid
what can prevent neural tube defects
folic acid
what are some Neural tube defects
spina bifida occulta, meningocele, meningomyelocele, myeloschisis, and enencephally
neural crest cells form where
at location where neural tube is pinching off from the dorsal surface
neural crest cells undergo what transformation before migrating throughout the embryo
epithelial to mesenchymal transformation to form ectomesenchyme
neural tube forms in what sequence
cranial to caudal, begins in cervical region
neural crest cells form what
dorsal root, autonomic and cranial ganglia, schwann cells, pigment cells, and branchial arch mesenchyme
defects in neural crest migration causes what
neurocristopathies, like hirschsrpungs disease (agangliionic megacolon) or DiGeorge syndrome (3rd and 4th branchial arch problems)
where does mesoderm not migrate to and what occurs because of this
oropharyngeal and cloacal membranes, eventually forms mouth and anus
mesoderm is organized into what
1 midline, and 3 paired regions. Notochord (midline), paraxial mesoderm, intermediate mesoderm, and lateral plate mesoderm
From center line to lateral how is the mesoderm arranged
notochard at midline, paraxial, intermediate, and lateral plate
paraxial mesoderm becomes segmented in cranial to caudal sequence to form what
somitomeres go on to form what
in the cephalic region how many somitomeres form and when do they form somites
7 form, they do not form somites
what 3 regions of somites and somitomeres are formed from paraxial mesoderm
cephalic somitomeres, occipital somites, and trunk somites
somites are what
cuboidal blocks of mesoderm composed of EPITHELIAL CELLS
Somites disperse to form what 2 types
sclerotome and dermamyotome
sclerotome forms what? myotome?
scel- axial skeleton , myotome- skeletal muscle
the somites that migrate dorsally and laterally are what type
the somites that migrate ventrally and medially around the notochard and neural tube are what type?
lateral plate mesoderm splits and gives rise to what
embryonic coelom
mesoderm associated with the ectoderm after splitting of lateral plate mesoderm is known as what? forms what
somatic mesoderm, forms future body wall
mesoderm associated with the endodoerm after splitting of lateral plate mesoderm is what? later forms what?
splanchnic mesoderm forms visceral structures
what does intermediate mesoderm go on to form
urogenital system
somatic mesoderm and ectoderm are collectively known as?
splanchnic mesoderm and endoderm are collectively known as what
where do the extraembryonic and embryonic coelom communicate
only at the future peritoneal region
when does embryonic folding occur
during fourth week
what occurs with median folding
cardiogenic region and oropharyngeal membrane fold ventrally and caudally, cloacal membrane folds ventrally and cranially and part of the yolk sac is incorporated into embryo as primitive gut
what occurs with lateral folding
lateral plate mesoderm moves ventrally and medially, participates in forming body wall
purse string closure refers to what in body folding
closure of all the foldings, occurs around umbilical ring
what is controlling the formation of the cranial caudal and dorsal venral body axis
hensens node
what occurs if hensens node is transplanted
formation of second primary body axis
what is thought to cause the formation of the left/right body axis?
different set of factors on left side than right, might be set up by beating of cilia in specific directions on hensens node
what occurs from cilia beating in wrong direction on hensens node
situs inversus
what are the derivatives from neuroectoderm
neural tube and neural crest cells
what forms from neural tube
cns, retina, posterior pituitary
what forms from neural crest cells
sensory neurons of dorsal root adn cranial ganglia, symp and parasymp postganglionic neurons, glials cells of sensory and ans, schwann cells, adrenal medulla gland, head mesenchyme, branchial arch cartilage, ciscerocranium, dentin, melanocytes
what forms from surface ectoderm
epidermis (hair and nails), cutaneous and mammary glands, anterior pituitary, enamel of teeth, inner ear, lens of eye, some sensory neurons of cranial sensory ganglia
what forms from paraxial mesoderm
trunk somites and cephalic somitomeres
what forms from trunk somites
sclerotome and dermamyotome
what forms from sclerotome
vertebral column and ribs
what forms from dermamyotome
all skeletal muscles in trunk and limbs
what forms from cephalic somitomeres
skeletal (neurocranium) and muscles of the eye and branchial arch derivatives
what is formed from intermediate mesoderm
urogenital system including gonads, ducts, and accessory glands
what is formed from lateral plate mesoderm
somatic layer and splanchnic layer
what is formed from somatic layer of lateral plate mesoderm
parietal membrane of pleura, pericardim, peritoneum, and participates with dermamyotome to form body wall
what is formed from splanchnic layer of lateral plate mesoderm
mosth muscle of hollow viscera (digestive system), cardiac musculature, visceral membranes (pleura, pericardium, and peritoneum
what is formed from endoderm
branchial apparatus, respiratory system, and gut tube
what is formed from branchial apparatus
pharynx, thyroid gland, tympanic cavity, pharyngotympanic canal, tonsils, parathyroid glands, and thymus
The appendicular skeleton forms from what?
lateral plate mesoderm (somatic layer)
the developement of cartilage is known as what?
skeletal muscle develops from what?
paraxial mesoderm only
skull is formed from what?
paraxial mesoderm and neural crest cells
Describe the basic process of chondrogenisis
mesenchyme condenses (precartilage condensation), chondroblasts are formed, chondroblasts differentiate into cartilage specific extracellular matrix, perichondrium surrounds cartilage
What are the two mechanisms by which cartilage grows?
interstitial growth, and appositional growth
cartilage growth through the division of chondrocytes is known as what?
interstitial growth (growth from inside)
cartilage growth from formation of chondrocytes from the perichondrium is known as what?
appositional growth (growth from outside)
what is bone formation known as?
What are the two types of osteogenisis?
intramembranous and endochondral
what type of bone formation results directly from mesenchyme?
intramembranous ossification
what type of bone growth occurs from a cartilage model?
endochondral ossification
what types of bones form from endochondral growth
long bones
describe the process by which intramembranous ossification occurs
mesenchyme condenses into a membrane, osteocytes form directly from membrane, growth is appositional only
describe the process by which endochondral ossification occurs
occurs in pre existing cartilaginous models, where cartilage dies and is replaced by bone
describe the steps involved in the formation of long bones
1. formation of cartilage model2. perichondrium becomes periosteum 3. appearance of primary center of ossification
4. growth in length of long bones
5. growth in width of long bones
6. after birth
the cartilage model of long bone is formed by when
7th week
where does the appearance of of primary center of ossification occur?
in diahpysis (chondrocytes hyprtrophy, invaded by vasculature, and osteocytes form
what is involved in the growth in length of the long bones?
cartilage at diaphyseal-epiphyseal junction continues to grow
where does growth in width for long bones occur?
appositional growth occurs at periosteum
after birth, where is secondary center for ossification in long bones
what 3 types of joints can be formed
synovial joint, cartilaginous joint, and fibrous joint
which joint forms capsule and ligaments, synovial membrane, and joint cavity
synovial joint
what joint forms hyaline or fibrous cartilage
cartilaginous joint
what joint forms dense connective tissue
how many vertebrae form and how many of each type
33 total: 7 cervical, 12 thoracic, 5 lumbar, 5 saccral, and 4 coccygeal
what is the difference between somitic mesoderm and somatic mesoderm
somitic is derived from paraxial mesoderm, somatic comes from lateral plate mesoderm
what groups does dermamyotome divide into?
dermatome and myotome
dermatome contributes to what?
contributes to dermis
myotome contributes to what?
formation of ALL skeletal muscles
what are the two types of scleretome
primary scleretome and secondary (definitive) scleretome
what differentiates primary scleretome from secondary
primary is segmental, and seperates into cranial and caudal parts. Caudal part fuses with inferior cranial part and this is secondary.
primary caudal scleretome fuses with what?
fuses with inferior cranial primary scleretome
the fusion of the primary caudal scelartome with the inferior cranial primary scleretome forms what?
secondary scleretome
what forms between the scleretomal segments
intervertebral disks
what migrates around neural tube and how to form vertebrae
scleretome migrates dorsally and medially
what migrates to where to form ribs and sternum
sceretome migrates into somatic mesoderm of body wall
what happens to vertebral arch if neural tube does not close
spina bifida occulta, meningocele, meningomyelocele, myeloschisis
dorsal muscles, through dorsal primary ramus innervation are known as what?
epaxial musculature
ventral muscles, through ventral primary ramus innervations
hypaxial musculature
what can occur from failure of somitic mesoderm (hypaxial) to complete migration into somatic mesoderm
what induces the formation of sclerotome
SHH sonic hedgehog
scleretome produces what that initiates cartilage and bone formation
PAX1 does what and is produced by what?
initiates cartilage and bone formation, produced by scleretome
what induces dermamyotome
What makes epaxial musculature
What makes hypaxial musculature
extensors of neck and vertebral column are innervated by what part of spinal nerves and are known as what?
epaxial muscles innervated by dorsal primary ramus of spinal nerves
prevertebral musculature such as lateral and ventral flexors of vertebral column are innervated by what and are called what
ventral primary ramus, called hypaxial muscles
what is the molecular regulation of sclerotome formation
SHH is produced by neural tube and notochord, this induces ventromedial portion to become sclerotome
what initiates bone formation and cartilage formation
sceleretome expresses PAX1
what is the molecular regulaton for dermamyotome formation
WNT from dorsal neural tube and epidermis induces dorsolateral portion to become dermamyotome
what molecular regulation creates epaxial muscle
medial portion expresses MYF5 and becomes epaxial muscle
what molecular regulation creates hypaxial muscle
lateral portion induced by BMP4, expresses MYOD and becomes hypaxial muscle
segmentation appears to arise from expression of what?
clusters of homeobox genes (HOXA, HOXB, HOXC, and HOXD
HOX genes at the 3' end of the cluster are expressed where? while 5' genes are expressed where?
3- cranially , 5- caudally
in neural epithelium where does cell division take place
ventricular surface
where does differentiation occur in neural epithelium?
subpial surface
what type of cell is neuroectoderm?
pseudostratified epithelium
what are the 3 main derivatives of neuroepithelium?
bipolar neuroblast, glialblast, and ependymal cell
what are the derivatives of glialblast
protoplasmic astrocyte, fibrillar astrocyte, oligodendroglia
bipolar neuroblast forms what
multipolar neuroblast
protoplasmis astrocyte forms what
gray matter
fibrillar astrocyte forms what
white matter
what is the phagocytic glial cell
what do oligodendroglia form
what is programmed cell death known as and what purpose does it serve?
apoptosis, refines number
what is the longitudinal groove that forms in the ventricular surface of the lateral walls
sulcus limitans
cellular proliferation and differentiation primarily occurs where? and what does this prduce in the roof plate and floor plate?
primarily occurs in lateral wall, makes thin roof and floor plates
intermediate zone is also known as what and forms what nervous system matter?
mantle layer or zone, forms gray matter
after mitosis some cells detach from apical surface and migrate away from where to where?
from ventricular zone, to intermediate (mantle) zone
neuronal cell bodies located in intermediate zone send axons where within neural tube, and this forms what zone (and what is this zone known as in adult?
toward external surface of neural tube to reach neurons at other levels of the neural tube. glia follow these axons and form the marginal zone. this is known as white matter later
the alar plate is in what relation to sulcus limitans and is associated with what?
dorsal to sulcus, sensory functions
basal plate is in what relation to sulcus limitans and is associated with what
ventral to sulcus, motor functions
neuroblasts differentiate into what two types of motor neurons
somatic and autonomic (sympathetic and parasympathetic
what prtein induces the formation of the floor plate and where does it come from?
sonic hedge hog, from notochord
mesenchyme surrounding neural tube forms what
what forms dura mater
what forms arachnoid and pia mater]
neural crest cells
neuroectodermal cells at each neural fold migrating away from the
developing neural tube
neural crest cells migrating between neural tube and paraxial mesoderm form what
dorsal root ganglia (sensory ganglia)
DRG cells differentiate into sensory neurons with how many processes
what processes come from DRG
central processes and peripheral processes
central processes go where and form what
away from DRG and toward neural tube, these make up the dorsal root of spinal nerves
peripheral processes go where and form what
away from DRG and neural tube, join ventral roots to form spinal nerves
sensory neurons form what with what?
sensory ganglia with cranial nerves 5, 7, 9, 10, and all segmental spinal nerves
Some DRG cells differentiate into the support cells of DRG known as
satellite cells
some neural crest cells migrate along dorsal and ventral roots, spinal nerves, and ans and differentiate into what
schwann cells
neural crest cells from the thoracolumbar region migrate ventrally to aggregate into what
sympathetic ganglia
what two types of sympathetic ganglia are formed from neural crest cells
chain ganglia and preaortic ganglia
sympathetic chain does what
help innervate the somatic mesoderm for the body wall
what portion of the chaing ganglia connects the segmental ganglion to the segmental nerves at all levels
gray rami communicans
what portion of the chain ganglia connects preganglionic fibers from T1 to L2 segments with sympathetic chain that distributes innervation throughout all vertebral levels
white rami communicans
preaortic sympathetic ganglia cells do what
migrate ventral to aorta to innervate the structures derived from the intermediate and splanchnic mesoderm
preganglionic axons in the greater splanchnic nerve synapse where
celiac ganglion
preganglionic axons in the lesser splanchnic nerve synapse where
superior messenteric ganglion
preganglionic axons in the least splanchnic nerve synapse where
aorticorenal ganglia and the adrenal medulla to innervate the kidneys
preganglionic fibers in the lumbar and sacral splanchnics travel to where
pelvic, intermesenteric, and inferior mesenteric ganglia
neural crest cells of suprarenal glands form what type of cells
chromaffin cells
chromaffin cells reieve direct preganglionic fibers from where and do what when stimulated
lower thoracic segments, and release epi when stimulated
neural crest cells that migrate to target tissue like the GI tract can form what (not sympathetic)
parasympathetic ganglia
what are the cranial nerves associated with parasympathetics
3,7,9, and 10
CN3 goes to what ganglion and sends fibers to what
ciliac ganglion to the cilliary bodies
cn7 goes to what ganglia to do what
pterygopalatine ganglia via greater petrosal nerve to the lacrimal gland and nasal cavity/hard palate // chorda tympani nerve to submandibular ganglino which gets submandibular gland, sublingual gland, and lingual glands (travels with lingual nerve
cn9 goes to what ganglia to do what
lesser petrosal nerve to otic ganglion to the parotid gland
cn 10 goes to what ganglia to do what
cardiopulmonary plexus, foregut, and midgut ganglia
what is failure of neural crest cells to migrate to colon wall
congenital aganglionic megacolon
aganglionic megacolon is what type of disease
hirschsprung disease
what are the two primary rami
dorsal and ventral
dorsal primary rami go to what
epaxial musculature, vertebrae, posterior intervertebral joints, and portion of skin on back

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