Quiz 1 - Colombo - General Embryology Flashcards
What is embryology?
Study of prenatal development
Prenatal development begins with the ______ of pregnancy and continues until ________.
Start
Birth
What two periods make up the first 8 weeks of fertilization?
What period constitutes the rest of pregnancy?
Preimplantation and embryonic (a lot of differentiation happens)
Fetal period
What is a primordium?
Earliest indication of a tissue or an organ during prenatal development
After fertilization, what is the ball of cells called?
Zygote
What’s after zygote?
Blastocyst
*This implants in the uterine wall.
**Fluid-filled - develops into the 3 primary germ layers, endo, meso, ectoderm
What comes after blastocyst?
Embryo
What comes after embryo?
Fetus
Growth factors can act thru what 3 major actions?
Autocrine
Paracrine
Endocrine
_______ factors, and cell _________ molecules act thru signaling complexes with activate various ___________ factors, affecting cellular changes.
Growth
Adhesion
Transcription
What is one growth factor that Colombo pointed out?
BMP - Bone Morphogenic Protein
What is BMP critical for?
Critical growth factor in craniofacial development, among others
What does BMP do at gastrulation?
Switches b/t epidermal vs neural fate
Tell me other things BMP does.
Induction, formation, determination, and migration of neural crest cells
Patterning and formation of facial primordia
Craniofacial skeletogenesis
Negative regulator of myogenesis (Makes bone instead of muscle)
*REGULATOR OF EARLY TOOTH MORPHOGENESIS AND DIFFERENTIATION
What do homeobox genes code for?
Transcription factors that begin to make cells pattern into one tissue/organ type or another
What else are homeobox genes involved in? 4 things
Bodily segmentation during embryonic development
Key regulators of embryogenesis: which end will be which
Homeobox is a 180 bp DNA sequence
Switches on cascades of other genes
What are 4 other genes the control embryonic formation?
HOX - Pattern the body axis and determine where limbs and other body segments will grow in fetus
Msx - Control cellular process of differentiation and proliferation during development
Dix - Development of ectodermal tissue from lateral border of the neural plate
Shh (Sonic hedgehog) - Early induction of facial primordium
Neurectoderm progenitors express what?
Skin ectoderm progenitors express what?
N-CAM (N for nuer..)
L-CAM
_____-_____ contact is hugely important for positioning and differentiation.
Cell-cell
What cell adhesion molecules are calcium-dependent?
Cadherins
What cell adhesion molecules are calcium-independent?
CAM
Morula is how many cells?
16
Dental lamina differentiates in what range?
24 - 40 days
What is the first period in embryological development?
Germinal or preimplantation phase - first ~10 days after conception
Fertilized egg has how many chromosomes?
46
What is hatching?
Getting rid of Zona pellucida
The zygote undergoing mitosis is called what?
Cleavage
*Initial cleavage is called morula, and then blastocyst
**This lasts until 3 germ layers have formed
The trophoblast is what?
Fluid-filled cavity in the blastocyst
What is the inner cell mass?
Clump of cells on one side of blastocyst
Where does the blastocyst implant on the uterus?
Innermost lining on the back wall (Endometrium) - After the first 7-10 days, the blastocyst stops traveling
What becomes the gut and GI?
Primary yolk sac
What is the inner cell mass called?
Embryoblast
THIS FORMS THE EMBRYO PROPER
When is the embryonic period?
Week 2 thru the end of week 8
Spatial and temporal events called __________ occur during the embryonic period
Patterning
What does patterning include?
Formation of:
Pharyngeal arches
Somite development
Face development
Palate
Tongue
What other 4 important things occur during patterning?
Axial specification
Segmentation (What forms in b/t each end)
Tissue and organ specialization and formation begin
*Development of dentition begins
What is induction?
When one group of cells tells another group of cells what to do (called competent)
What is proliferation?
Cell division, increase in number and accumulation of cell products
What is differentiation?
Development of specific structures and/or functions by individual cells/groups of cells
What is morphogenesis?
Cell MIGRATION, interactions and proliferation’s causing development of specific structures
What is maturation?
Attainment of adult size and function from proliferation, differentiation, and morphogenesis
What is gastrulation and when does it occur and why is it important?
Formation of 3 germ layers
Week 3-ish
Different tissues and organs arise from
What is the origin, morphology, and future systemic tissues of the ECTODERM?
Epiblast layer
Columnar
Epidermis, sensory epithelium of the eyes, ears, nose, nervous system, neural crest cells, mammary and cutaneous glands
What is the origin, morphology, and future systemic tissues of the MESODERM?
Migrating cells from the epiblast layer
Variable
Dermis, muscle, bone, lymph, blood cells, marrow, cartilage, repro and excretory organs
What is the origin, morphology, and future systemic tissues of the ENDODERM?
Hypoblast layer
Cuboidal
Respiratory and digestive linings, liver and pancreatic cells
After the blastocyst implants, the embryoblast differentiates into 2 layers. Name them.
Dorsal cells - EPIBLAST layer - forms amniotic cavity - Ecto, meso, and endo from this layer
Ventral cells - HYPOBLAST layer - form the roof of the secondary yolk sac - this layer modifies the endoderm
*This forms the bilaminar disk, and the establishment of the embryo axis, so a head and a tail end now
The epiblast has what types of cells (histo)?
Superior, high columnar cells
The hypoblast has what types of cells (histo)? And the hypoblast is ________ to the epiblast.
Small cuboidal
Inferior
After the formation of the bilaminar disk, __________ _________ forms and starts gastrulation.
Primitive streak
What is the primitive streak?
Little groove formed by epiblast cells - This defines the future bilateral symmetry along a rostral-caudal axis
The ________ _______ forms at the rostral end of the primitive streak, where the ectoderm curves around and integrates with the __________.
Prochordal plate
Endoderm
Ectodermal cells invaginate at the ________ ________ forming the ________ _________. This happens at _________.
Primitive node
Primitive pit
GASTRULATION
The ______ forms during gastrulation.
Notochord
The ________ cells divide, migrate, and invaginate spreading laterally b/t the two layers to form the ___________.
Ectodermal (epiblast)
Mesoderm
The meso last cells actually form the _______ _________ endoderm and mesoderm.
True embryonic
Hypoblast cells are pushed out of the way as invaginating cells from the _________ form the true endoderm.
Epiblast
Thus everywhere except at the _______ _______ and the _______ ________ the notochord and mesoderm totally separate the ectoderm and endoderm.
Prochordal plate
Cecal plate
T/F - Medial epiblast cells lose their cell-cell adhesions in the formation of the mesoderm.
TRUE
*They become motile and invade inwards
**These mesenchymal cells are interspersed in matrix and are devoid of polarity
In formation of the mesoderm, a change in cell attachment proteins occurs. What is the change?
E to N cadherin
*Important in tooth development when epithelial cells and mesenchymal cells have to talk to one another to make enamel and dentin/pulp.
In summary, epithelial cells go to mesenchymal cells, and what are the major changes?
Polarity to no polarity
Cell adhesion to no cell adhesion
Stationary to ability to migrate and invade
High level of E-cadherin to low level of E-cadherin
Low level of N-cadherin to high level of N-cadherin
With three layers formed, we now have a ___________ embryo.
Triploblastic
Describe the triploblastic embryo.
Disc with 3 layers, cephalic end defined by the prochordal plate, and folding can occur, especially at the rostral end
The head fold forms the what?
Oropharyngeal (buccopharyngeal) membrane at the prochordal plate end (no mesoderm b/t ectoderm
*This is where the stomodeum (primitive mouth) will be
Ectodermal cells give use to what?
Nervous system
Epidermis and appendages (hair, nails, sebaceous, and sweat gland)
Epithelium lining the oral cavity, nasal cavities, and sinuses
Part of the intraoral glands
Tooth enamel
Endodermal cells give rise to what?
Epithelial lining of respiratory and GI tract and associated organs
Mesodermal (mesenchymal) cells give rise to what structures?
Muscles and all the structures derived from the CT (Bone, cartilage, blood, and sort of dentin, pulp, cementum, and PDLs)
After gastrulation (week 3), what 3 key events take place?
Differentiation of the nervous system
Formation/migration of the neural crest
Embryo folding: head, lateral, and tail folds
What forms the neuroectoderm?
Specialized group of cells that differentiates from the ectoderm
Where does the neuroectoderm form?
Localized to the neural plate of the embryo, a band of cells extends the length of the embryo
The neuroectoderm plate grows and thickens, which causes it to deepen and invaginate inward, forming the _______ _______.
Neural groove
The neural tube becomes what?
CNS - brain and spinal cord
Neural tube closure - the neural fold fusion begins where and proceeds both rostrally and caudally?
UPPER CERVICAL LEVELS
If the neural tube does not close properly, what occurs?
Spina bifida
What is the fate of the mesoderm?
It segments bilaterally into three keys mesoderm parts.
Name and name the fates of the 3 main mesoderm parts.
Paraxial - Cartilage, segmented muscle
Intermediate - Kidneys, gonads
Lateral plate - Heart, gut
Differentiated mesoderm gives rise to the _______ that are located on the sides of the developing CNS.
Somites
The neural tube expands to form what 3 things?
Forebrain
Midbrain
Hindbrain
The hindbrain segments further into what?
Rhombomeres- these express HOX genes
*Branchial arches develop
T/F - The neural crest cells are the embryological layer 3.5.
TRUE
The neural crest develops from what during the 3rd week?
Neuroectoderm
What does the neural crest do?
Breaks up and migrates away from the crests of the neural folds and disperses in mesenchyme
Neural crest cells can also be called what?
Ectomesenchyme
Why are the neural crest cells so important for us?
This is where dental pulp and dentin come from
Failure of the neural crest cell migration can lead to what?
Abnormal craniofacial development
EX - Treacher Collins Syndrome - mandibulofacial dysostosis
The ________ fold is critical to formation of the oral cavity.
Head
What else occurs with the continuation of embryo folding, along with the head fold?
Future GI tract begins to form
*Folding ultimately determines the final disposition of ectoderm, mesoderm, and endoderm
What remains separate, but ultimately breaks down to form the mouth?
Stomodeum
The _______ gives rise to the primitive pharynx.
Foregut
*This becomes the oropharynx
*Neural crest forms what?
Cranial nerves
Adrenal medulla
Ectomesenchyme bones and skull
Dentin
PDL
Alveolar bone
*Neuroectoderm forms what?
Post pit
Pineal body
Retina
CNS
*Intermediate plate forms what?
Urogenital system
*Lateral plate forms what?
CT (mesenchyme)
Visceral mm
Serous mem of pleura
Pericardium and peritoneum
Blood and lymph
Spleen
Adrenal cortex
*Paraxial forms what?
Trunk mm
Skeleton (except skull)
Dermis
CT (mesenchyme)
*Surface ectoderm forms what?
Epidermis
Hair
Nails
Cutaneous glands
Mammary glands
Ant pit
ENAMEL
Lens
Inner ear
*Endoderm forms what?
Epi of trachea
Bronchi and lungs
Epi of GI tract
Liver and pancreas
Bladder
Epi of pharynx
Thyroid and parathyroid
Auditory tube
Tonsils
The fetal period is from week _______ thru ________.
9
Birth
What happens during the fetal period?
Basic tissues and structures are mainly formed, so now its growth and specialization
*Embryo becomes a fetus
**Proliferation, differentiation, and morphogenesis - actual organs - are made
Mesenchymal can give rise to what?
CT
Ectomesenchymal is derived from ________, but makes _______.
Ectoderm
CT
