Exam 1 Flashcards
Embryology
study of embryo until time of parturition
Parturition
Birth
Development
morphological, biochemical and physiological differentiation of an individual (embryology & gametogensis & after birth)
Differentiation
generation of cellular diversity (fertilized egg specialized into different cell types)
Morphogenesis
creation of form and structure
Growth
increase in size
Germinating
giving life
Ontogeny
growth and development of individual from fertilization to birth
Zygote
the fertilized egg
Embryo
developing organism form cleavage to birth (2 cells)
Fetus
developing embryo (in human after 3 mo.)
What are the two major accomplishments of the developmental process?
- Generates cellular diversity and order with each generation
- Ensures the continuity of life from one generation to the next
What are the 7 stages of embryogenesis?
- Fertilization (zygote formation)
- Cleavage (embryo, morula)
- Blastulation
- Gastrulation
- Organogenesis
- Germ cell formation
- Larval stage
What are the three layers formed in gastrulation?
- Ectoderm
- Mesoderm
- Endoderm
How do we approach the study of embryos (3)?
- Anatomical
- Experimental
- Genetic
What are the four parts of the anatomical study of embryos?
- Comparitive
- Teratology/Medical Embryology (limited since we can’t experiment on human embryos)
- Evolutionary
- Fate Mapping
Historical Perspective: the anatomists. How did they believe the embryo formed?
Epigenesis
Parts of the embryo arise in succession
What did Aristotle believe in?
Oviparity, vivipaarity, oviviparity
Major cleavage patterns
Functions of placenta and umbilical cord
Mensus gave material, semen gave form and animation
Historical perspective: who was William Harvey? What did he believe? He was the first to observe what?
Ex ovo omnia All animals from eggs 1st to observe chick blastoderm Blood islands form before heart Amniotic fluid functions as shock absorber
Epigenesis vs Preformation
Epigenesis: organs of embryo develop de novo
(aristotle / harvey)
Performation: tiny babies live inside of us. all generations that will ever be are within you. All orgas are pre-formed, simply required growth
What are two supporting contemporary theories of preformation?
- Infinite divisibility (things can be infinately small to serve their purpose)
- Limited time (creation to apocalypse)
Predate cell theory (didn’t understand there was a limit to how small things can be)
What are the two schools of preformation?
- Ovist
2. Spermists
What did Spallanzani believe?
Preformation
Experimented with frogs; put pants on them and stopped semen from transferring = no offspring
Established that sperm was needed to trigger the generation of offspring
Who were the Baltic Boys? What did they do?
Rathke, von Baer, Pander
Rathke - proposed how pharyngeal pouches, reproduction/extretory/respiratory system developed
von Baer - mammalian egg and notochored
Pander - primary germ layers induction
What were the 4 von Baer’s Principles?
- General features appear earlier in development than specialized features (general features of all vertebrates (arches, notochord)
- Generalized features give rise to more specialized (general skin gives rise to scales, feathers, hair, etc)
- Embryos do not possess adult features of lower animals (gill slits of mammals don’t look like adult gill fish)
- Higher animals are never like lower animals, only like their early embryos (I was never a monkey)
Medical Embryology has no experimental data, so what do physicians utilize?
Physicians utilize nature’s “experiments”
2-5% of infants have observable anatomical abnormalities
What are the 3 main causes of birth defects?
- Malformations (genetic events)
- Disruptions (exogenous causes)
- Random Chance
Malfomraitons often appear as ______
Syndromes
What is Piebaldism? What gene contains the defect? What is the result?
Syndrome
Defect in KIT
Specific neural crest cells, RBC, germ, peripheral nerve cells fail to proliferate
Loss of pigment cells (white on forehead and stomach), loss of ear cells, loss of gut neurons
Overall: deafness, digestion issues, anemic, sterile, lack of pigment
99% of Dwarfism is a result of what malformation? What does this cause? (Peter Dinklage)
Defect in FGF4, FGFR3
Cartiledge cells lay the formation of bone develope,ent
FGF4 inhibits cartilege cell production > achondroplasia > limited bone growth (weiner dogs too)
What are teratogens?
Exogenous agents causing abnormalities
ex. chemicals, viruses, radiation
Tell me the story of Thalidomide. How many infants were affected? How many pills did it take? When was the susceptibility period for the mother? What did the children develop (symptoms)?
It was given as a mild sedative to alleviate morning sickness, effected 7,000 infants
1 pill was sufficient
Susceptibility during day 35-50 of menstaul cycle (20-36 days post conception)
Children developed phocomelia (long bones deficeint/absent)
Heart defects, absence of external ears. malformed intestines
What was the big developmental biology lesson form Thalidomide?
The symptoms the child faced (absence of ear, absence of arms, etc) was dependent on the days after last menstruation
So, it told us when different parts of the embryo were developing at day 34, 38, 42 and so on
It also told us that exogenous agents in general will effect different pieces of development depending on when it is introduced
What is gestational age?
The gestatial age is how long a woman has been pregnant
Gestatial age = 10 weeks
Embyro age = 8 weeks
Who is Thomas Quasthoff?
A thalidomide baby that is now an opera singer
Homology vs Analogy
Homology: Evolutionarily linked, same face bones from forengial arches
Analogy: not embryologically linked, developed separately, wing of a bird and butterfly
What is Fate Mapping?
Tracing cell lineages through development to figure out what they will ultimately become
What are the two types of cell movements?
- Mesenchyme cells
2. Epithelial cells
How do mesenchyme cells move?
Move independently as a herd
ex. Zebra
How do epithelial cells move?
Move as a unit
ex. people linked arms and moved together
What are the 6 fundamental professes driving morphogenesis?
- Direction and number of cell divisions
- Cell shape changes
- Cell migration
- Cell growth
- Cell death
- Changes cell membrane or secreted products
When was the first fate map created? From what organism?
1906
Conklin
He mapped a chicken egg
What are the different ways you can fate map?
Flourecent, dyes, GFP in genetics
What are the 4 major techniques of Experimental Embryology?
- Defect: destroy portion of embryo (how does it develop lacking these cells?)
- Isolation: remove portion & observe development (how do singular cells develop)
- Recombination: replace original part with part from another region (diff part of same embryo)
- Transplantation: one portion replaced by part from another embryo
What are the three fundamental forces of experimental embryology?
- Forces outside the embryo
- Forces within the embryo/cells
- Forces ordering cells into tissues
What is an example of a force outside of the embryo affecting development?
Temperature
In reptiles
Higher temperatures (above 34) are males
How does climate change affect reptiles that rely on temperature to determine sex?
Increasing temperatures and fewer trees > increased number of male reptiles
What is another example of a force outside of the embryo affecting development?
Development of both females and males in the same Echiuroid worm
Female: if larvae land in sand, larger
Male: if larvae land on female proboscis, lives symbiotically inside female reproductive organs and acts as a gonad
What are sequential hermaphrodites?
Organims that transition from one sex to the other or to a combination of both
Protandry
Male to larger female
Protogyny
Female to larger male
Protogynous hermaphroditism
Female to hermaphrodite
Protandrous hermaphroditism
Male to hermaphrodite
Dimorphism
Females and males look different
Which sex is typically higher energy?
Females - takes more energy to make eggs than sperm
What are simultaneous hermaphrodites?
both reproductive parts at the same time
Differentiation
development of specialized cell types
Commitment
developental fate of cells is restricted
Go from differentiation through the stages of commitment to a fully differentiated cell
True
What are the two stages of commitment
- Specification
2. Determination
Specification
Autonomous differentiation in a neutral environment
Still reversible
Determination
Autonomous differentiation regardless Assumed irreversible (regardless of outside influence)
What are the only cells in your body that are not fully differentiated?
Stem Cells
Stem cells can differentiate OR make more of themselves
What are the three basic mechanisms of specification? What organisms do we see these mechanisms in?
- Autonomous specification (most invertebrates, inherited transcription factors, asymmetrical eggs)
- Conditional specification (all vertebrates & some invertebrates)
- Syncytial Specification (most insects)
What is autonomous specification?
- mosaic development
- determinal specification
- Fate is set from very beginning, predetermined
- Morphogens
Morphogens
Generates morphology (ex. TF)
Who was L. Chabry? What did he do?
1st to demonstrate autonomous specification
Pull it apart and it will still develop into specified pieces
Summary - Autonomous Specification. It is characteristic of what kind of organism? The specification is achieved by what? where? Cells can’t change fate if _____ is lost
- Characteristic of most invertebrates
- Specification by the differential acquisition of cytoplasmic molecules present in egg
- Cells can’t change fate if blastomere lost
(You get half a person if you split the cell)
What are the 2 characteristics of conditional specification?
- Each cell has the potential to become any of the many different cell types
- Interactions with other cells/factors restricts fate
(You get twins if you split the cell)
Who was Wilhelm Roux? What was his big achievement?
Frog Mosaic development
At the two-cell stage, he killed one cell > the dead tissue was still able to influence the living cell > still end up with dead half and live half
What is something unique about the nine-banded armadillo?
They have 4 identical twins every time they reproduce
Who was Hans Dreisch? What was his big achievement?
Urchin development
Echinoderms = only group of invertebrates that are conditional specification
If you split up the 4 cells > get 4 fully formed structures
Also noted, location in the blastomere dictates fate!
What is syncytial specification?
Seen in insects
Multinucleate cell structure
Nucli replication > multiple nuclei > signal gradient > different development
What are the three typesof cell-cell interactions in development?
- Cell Adhesion
- Cell Migration
- Cell Signaling
What is differential cell affinity?
When germ layers are developing you can scramble them up and they will still cluster on the inside and outside the way they should
This is because the endoderm has the strongest cell adhesion (surface tension) and the epiderm has the weakest
What is surface tension?
The strength it takes to seperate two cells
What generates surface tension between cells? (2)
- Cadherins (cell-cell)
2. Integrins (cell-ECM)
What are cadherins?
Calcium dependent adherein molecules
What is one way to cause cells to dissociate?
Remove calcium > targets cadherins > lose cell-cell adhesion
What are catenins?
Linked to actin in the cytoskeleton to give the cell strength
Connect Cadherins to the cytoskeleton
What are two factors that can affect Cadherin strength?
- Number of cadherins
2. Types of cadherins
What is a homotypic binding? Example?
When two of the same molecules bind together
ex. Cadherin-Cadherin binding
What are the 4 types of cadherins?
- E-cadherin
- N-cadherin
- P-cadherin
- VE-cadherin
What is the main location of E-cadherins?
epithelia