Day 13, Lecture 1 (Sept 8): Human Development 1: The first week of development Flashcards
1
Q
Gestational Age
A
- Staging of the human embryo
- Determine age based on time from last normal menstrual period
- Normal time to parturition- 40 weeks
- Staging used clinically
2
Q
Fertilization age
A
- Staging of the Human Embryo
- Determine age based on time from fertilization
- Normal time ot parturition
- 38 weeks
- Staging used in embryology and in this class
3
Q
Staging of the Human Embryo
A
- Gestational age
- Determine age based on time from last normal menstrual period
- Normal time to parturition
- 40 weeks
- Staging used clinically
- Fertilization age
- Determine age based on time from fertilization
- Normal time to parturition
- 38 weeks
- Staging used in embryology in this class
4
Q
A
5
Q
The Embryonic period
A
- Weeks 1-8
- Organogenic period
- Time most vulnerable to teratogens
6
Q
Fetal Period
A
- Weeks 9-32
- Development of organs and organ systems
- Extensive growth
- (luns developed sufficienctly at approximately 24 weeks to allow survivla of fetus with extensive critical care)
7
Q
What makes the earliest an infant can survival premature birth
A
- Development of the lungs
- lungs developed sufficiently at approximately 24 weeks to allow survival of fetus with extensive critical care
8
Q
Postnatal develpment
A
- Development continues after birth
- Respiratory system
- Alveoli form in lungs
- Cardiovascular system
- Closure of fetal shunts and vessels
- Nervous system
- Continued neuronal development
- Respiratory system
9
Q
What are the key processes that must occur for a fertilized egg to give rise to the adult
A
- Proliferation
- Growth
- Differentiation
- Pattern Formation
- Morphogenesis
10
Q
What is differentiation
A
- Process by which cells or tissues become different from one another
- Progressive acquisition of structural and biochemical specializations leading to unique or highly developed cellular functions
11
Q
There are how many different specialized cells in adult human
A
200
12
Q
Totipotent
A
- Can differentiate into all cell types
- examples
- Zygote
- Morula
- examples
13
Q
Pluripotent
A
- Differentiate into many cell types
- examples
- Inner cell mass
- Epiblast
- examples
14
Q
Multipotent
A
Differentiate into restricted group of cells
15
Q
Unipotent
A
Determined as to differentiated cell to form
16
Q
Since all cells contain the same set of genes (genomic equivalence) how can genes direct development when same in all cells?
A
- Differential Gene Activity
- Different genes are turned on and off during development leading to specific genes being expressed in the differential cell
17
Q
Does differential gene acitvity lead to irreversibly turning off of genes?
A
- No
- Think about Dolly and iPS cells
18
Q
Induced Pluripotent Stem Cells (iPS cells)
A
- Reverse differentiated cell to pluripotent state
- Express factors found in pluripotent cells
- Another demonstration of genomic equivalence
- Provide possible pluripotent stem cells to be used clinically
- Genotype same as patient if use adult cell from patient
23
Q
Specification of Little Verse Great Digit
A
24
Q
A
26
Q
Syndactyly is a malformation due to
A
- Altered Morphogenesis
- Lack of apoptosis in interdigital regions
27
Q
A
28
Q
Egg at Fertilization
A
29
Q
Cleavage
A
- Specialized cell division whereby daughter cells divide rapidly reducing size with each division
- Partition of cytoplasm of zygote into small cells (blastomeres) without an increase in cytoplasmic mass
- Reason for cleavage
- Zygote very large (1000 micrometers) compared to normal cell (10 micrometers)
30
Q
Morula
A
- 12-16 cell stage
- formed on 3rd day
31
Q
Compaction of Morula
A
- compaction occurs 4 days post fertilization
- first morphogenesis in the embryo
- Formation of tight junctions between outer blastomeres
- Tight junctions allow for the partitioning of inside and outside
- Dependent on the presence of E-cadherin in outer layers of blastomeres
- Forms two distinct lineages
- outer and inner cells
- Blastomeres no longer totipotential
32
Q
Blastocyste formation
A
- 4 day post fertilization
- Following compaction
- Forms fluid filled cavity- blastocyst cavity
- First sorting of embryonic cells into lineages
- Inner cell mass cells will form embryo
- Pluripotenital
- Trophoblast
- will form protective membranes
- Extraembryonic membrane (chorion)
- Inner cell mass cells will form embryo
33
Q
Hatching of Blastocyst
A
- Weakening of Zona Pellucida
- Blastocyste squeezes out of zona pellucida
- Formation of floating blastocyst (6th day of development)
34
Q
A
35
Q
Implantation
A
- end of the first week of development
- Floating blastocyste makes contact with the endometrial lining of the uterus
- Trophoblast will form two distinct layers of cells
- Cytotrophoblast
- Actively dividing
- gives rise to Syncytiotrophoblast
- Syncytiotrophoblast
- nuclei don’t divide
- highly envasive into endometrium allowing for implantation
- Produces matrix metalloproteinases (MMPs) to promote invasion
- (note: the most invasive carcinoma known is choriocarcinoma similar process of invasion used during metastasis)
- Produces protein and steroid hormones
- ex. hCG, which stops the menstrual cycle
- Produces matrix metalloproteinases (MMPs) to promote invasion
- Cytotrophoblast
36
Q
Reorganization of the inner cell mass
A
- occurs at the end the first week of development
- Delaminates into:
- Hypoblast layer- forms extraembryonic structures
- Epiblast- Forms embryo proper
37
Q
- Review of 1st week of Development
A
39
Q
Abnormal Implantation sites
A
- any place place other than the normal (superior part of the body of the uterus)
- most frequent normal location is in the posterior part of the superior body of the uterus
- Placentia Previa
- implantation in the lower part of the uterus
- placenta is covering the internal os of uterus
- may result in early placential
- fetus must be delivered by cesarean section
- Tubal Implantation
- is the most common ectopic site (about 98%)
- Result of delayed transport along uterine tube
- In approximately 50% of tubal pregnancies if the embryo remains will result in rupture 6-8 weeks post-ferilization. leading to potential death of mother due to internal bleeding
- is the most common ectopic site (about 98%)
- Ovarian and abdominal implantation
- Relatively rare
- Risk of internal bleeding high
41
Q
Multiple pregnancy
A
- Natural cycle:
- Twins
- 1:90
- Triplets
- 1:902
- Quadruplets
- 1:903
- Twins
- 2/3 of twins dizygotic
- 1/3 monozygotic
42
Q
Monozygotic Twinning
A
- Formation of Identical Twins from splitting of Blastomeres
- Twinning occurs during cleavage
- two morulas are formed forming two embryos demonstrates
- blastomeres are totipotential
- Blastomeres can regulate
- Formation of Identical Twins from splitting of inner cell Mass
- Twinning occurs at blastocyst stage
- inner cell mass divides forming two embryos demonstrates
- inner cell mass cells are pluripotential
- inner cell mass cells can regulate
43
Q
In Vitro Fertilization
A
- Can be used as an effective treatment for infertility
- Indications for IVF
- Blocked fallopian tubes or pelvic adhesions
- Male factor infertility
- Failed 2-4 cycles of ovarian stimulation with intrauterine insemination
- Unexplained infertility
- Vasectomy or tubal ligation
- Preimplantation genetic diagnosis
- In Vitro Fertilization Protocol
- Usually have 10-15 blastocysts per cycle
- Implant no more than 3 blastocysts
- Freeze remaining blastocysts for subsequent use
