Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
53 Cards in this Set
- Front
- Back
What are the 3 primary germ layers of the embryo?
|
-Ectoderm
-Endoderm -Mesoderm |
|
What are the 2 types of embryonic tissues in the early embryo?
|
-Epithelium
-Mesenchyme |
|
What major difference distinguishes embryonic tissue from adult?
|
The ability to transform between epithelium and mesenchyme, given the proper stimulus.
|
|
What ability do adult tissues have?
|
The ability to self-renew via stem cells
|
|
What are the four primary tissue types found in human bodies?
|
1. Epithelium
2. Nervous tisue 3. Connective tissue 4. Muscle |
|
Into what 2 periods is prenatal development subdivided?
|
1. Embryonic period
2. Fetal period |
|
How many weeks is each prenatal development period?
|
Embryonic = weeks 1-8
Fetal = weeks 9-38 |
|
What are 9 things that happen in the embryonic period?
|
1. Fertilization -> zygote formation
2. Blastocyst forms from zygote cleaving 3. Implantation 4. 3-layer flat embryo forms 5. Axes determined 6. Segmentation of embryo 7. Folding of embryo 8. Limbs/head/trunk form 9. Organs/organ systems form |
|
What happens in the Fetal period?
|
-Fetus grows in size
-Organs mature and grow |
|
What is the difference between gestational and fertilization age?
|
Gestastional age is 2 weeks longer than fertilization because starts at LNMP.
|
|
What is the definition of an embryo?
|
An unborn human in the first 8 weeks of development
|
|
What is the Perinatal period?
|
22 weeks -> First month after birth.
|
|
What is the neonatal period?
|
the first month after birth.
|
|
How many stages is the first week broken into? What days correspond?
|
Stage 1 = Day 1
Stage 2 = Day 1.5-3 Stage 3 = Day 4 Stage 4 = Day 5-6 |
|
How does the embryo change during the first week?
|
-Goes from being unicellular to multicellular
-Develops a cavity -Travels through oviduct -Implants in uterine wall |
|
What happens to the zona pellucida durnig the first week?
|
It disappears by the 4-6 day.
|
|
What are the 4 major molecular and cellular events during cleavage?
|
1. Cell divison
2. Genome activation 3. Blastocyst formation 4. Blastocyst development |
|
What characterizes the cell divisions during week 1?
|
-Rapid mitosis, no G1/G2
-No cell growth - ZP restricts it -Asynchronous blastomere division -Cytoplasm:Nucleus ratio goes from 300:1 -> 3-6:1 |
|
What causes the first cell division in an embryo?
|
A program written by maternal oocyte during oogenesis.
|
|
When does the embryo's own genome start to direct mitosis?
|
When it is activated at the 2-4 cell stage
|
|
When do paternal genes start to be expressed?
|
After embryonic genome activation, 2-4 cell stage.
|
|
What significant morphological change occurs as the embryo reaches the morula, 16-cell stage?
|
Compaction
|
|
What causes compaction?
|
The increased surface area of contact between blastomeres.
|
|
At what cell stage (number) does blastocyst formation occur?
|
8-16 cells
|
|
What distinguishes the blastocyst formation?
|
Development of 2 cell lineages:
-Trophoblast -Inner cell mass |
|
What is the inner cell mass?
|
Embryoblast - the real stuff that we care about.
|
|
What exactly is the blastocyst?
|
A fluid filled vesicle lined by trophoblast cells
|
|
What capability is conferred to the embryo once the blastocyst forms?
|
The ability to implant in the uterine wall.
|
|
What type of tissue is the trophoblast layer of cells lining the blastocyst?
|
Epithelial - cells joined by junctions, polarized, and covering the cavity lining.
|
|
What type of tissue will the trophoblast become?
|
Extraembryonic
|
|
What controls trophoblast and extraembryonic tissue development?
|
Genomic imprinting - paternal genes are favored.
|
|
What is another example of genomic imprinting?
|
-X chromosome inactivation
|
|
How do X chromosomes get inactivated in female somatic vs. trophoblast cells?
|
Trophoblast: paternally derived X is selected for inactivation
Somatic cells: inactivation is random |
|
What is the polarity of
-Trophoblast tissue -Inner cell mass |
Trophoblast = polarized
ICM = initially non polarized |
|
What happens to the ICM as it develops?
|
Forms a Bilaminar Disc
|
|
What does the bilaminar disc consist of?
|
-Hypoblast
-Epiblast |
|
What will the hypoblast become?
|
Extraembryonic
|
|
What will the Epiblast become?
|
Embryonic + Extraembryonic
|
|
What develops as a result of the Bilaminar disc formation?
|
Embryo's Axis of Polarity
-Ventral= bottom epiblast layer -Dorsal = upper epiblast layer |
|
What 3rd thing (other than trophoblast and ICM development) occurs to the embryo during trophoblast development?
|
Hatching from the ZP
|
|
What are the functions of the ZP while the embryo develops?
|
1. Keeps blastomeres together
2. Prevents the embryo from being recognized as foreign 3. Prevents premature implantation |
|
What does hatching from the ZP allow?
|
-Small increase in embryo size
-Ability to implant in uterine wall. |
|
What is potency?
|
The full range of developmental capabilities available to a blastomere.
|
|
What is nondisjunction?
|
The failure of chromosomes to separate correctly - results in cells with different genomes.
|
|
What 3 develpmental potentials do cleavage-stage embryos posses?
|
1. The potential to REGULATE.
2. Potential for Cell Diversity 3. Potential for Twinning |
|
What is Regulation?
|
The ability to develop normally when parts have been removed or added.
|
|
What happens to the embryo's potential for regulation?
|
It decreases
|
|
-What term denotes full ability to regulate? What stage has it?
-What denotes decreased ability to regulate? What stage? |
Totipotent - 0-8 cell stage
Pluripotent - 16-cell stage |
|
What condition results from an embryo's cells containing different genomes? What causes this?
|
Chimerism, aka Mosaicism
-Nondisjunction |
|
How many births in USA are:
-Twins -Triplets |
Twins = 1/90 births
Triplets = 1/8000 births |
|
What causes monozygotic twins to form? What fraction of twins result from this process?
|
Blastomere/ICM separation
1/3 |
|
What causes dizygotic twins to form? What fraction?
|
Double ovulation and fertilization; 2/3
|
|
What causes conjoined twins to form?
|
Separation of blastomere/ICM (monozygotic twinning), but failure of the embryo to separate COMPLETELy.
|