Early Embryonic Development and Cell types Flashcards
Explain how the umbilical chord is formed/ structure of the umbilical chord
Pinch off part of amnion wither side and yolk sack and allois in between to form the umbilical chord
This will form layer of ectoderm- inside mesoderm, surrounding vitello-intestinal duct (connecting gut/ intestine to yolk sack/ vitelline) on one side, on the other umbilical vein, umbilical artery and allantois
Explain where the intraembryonic coelom is found
- Horse-shoe shaped cavities in the lateral intraembryonic mesoderm fuse forming intraembryonic mesoderm
- Bent structure shaped around gut tube
REM- still communication between intra and extraembryonic coelom until the yolk sack pinches off - Forms 1 pericardial cavity (heart), 2 pleural (lungs) and 2 peritoneal cavities (abdominal)
- By the time we get to 3 cavities connection between outside and inside of the embryo (intraembryonic and extraembryonic coelom) is lost
- Gut in communication with outside so some congenital malformations where the gut forms outside the body in sack connected via umbilical region
- Normally can ve repaired
Explain the 3 structures formed from the intraembryonic coelom and their structure
- At pericardial cavity V-shaped
- At Pericardial cavity 2 dots either side of gut
- At peritoneal cavity 2 open slits
REM if we stretch hands down peritoneal slits we will end up with either hand in a peritoneal cavity!
When does the embryo start differentiation?
- In early stages cleavage occurs producing morula (all 16 genetically identical stem cells surrounded by vitelline space and zona pellucidum)
- Blastocyst is formed where cells will begin to migrate to locations that will later define structure of embryo and organism (we see inner cell mass and trophoblast later forming placenta and embryo/ umbilical chord)
- In process of gastrulation- due to formation of primitive streak cells flow in forming the 3 germ layers- endoderm, mesoderm and ectoderm
Explain some of the derivatives of the 3 germ layers
- Endoderm- epithelia of internal surfaces e.g. respiratory, digestive and urinary system
- Mesoderm- Paraxial mesoderm- SCLEROTOME (muscles of head, trunk, limbs) skeleton, dermis, connective tissue
- Intermediate mesoderm- MYOTOME urogenital system, gonads, ducts, accessory glands
- Lateral mesoderm- DERMOTOME (dermis not epidermis) connective tissue and muscle of viscera, serous membranes, heart blood, spleen, adrenal cortex
- Ectoderm- neural ectoderm (ganglia, adrenal medulla, pigment cells pharyngeal arch cartilage, head mesenchyme and connective tissue, parts of heart) and neural tube (CNS, retina, pineal, posterior pituitary)
- Surface of body- skin hair nails, mammillary glands, anterior pituitary
Explain how embryonic differentiation is controlled within cells
- Transcription factors help regulate switching off/ on of genes so that different cell types are formed (division of labour)
- Regulative development- we have gradients of regulative factors and interaction of the adjacent cells with the “embryonic (morphogenic) fields” gives differentiation flexibility
Explain 2 important characteristics of stem cells
- Unspecialised- can divide repeatedly over long periods
- Under certain conditions they can be induced to differentiate into cells with special functions (e.g. muscle cells)
This can be useful in treatment of diseases e.g. in ischaemia to make new cardiac tissue but although done in lab unsure of process is terminal (cells will stay in form we want them)
Explain 2 different relationships of mitosis and differentiation- give e.g.
- Stem cells undergo mitosis and all of them differentiate
OR - Divergent differentiation- daughter cells of different types are formed e.g. haematopoietic stem cell in bone marrow
Alternatively divergent differentiation can result in differentiated daughter cell and retained stem cell
Explain the 3 types of stem cells
- Totipotent- give rise to all cells cells found in adult and extraembryonic cells e.g. zygote and placental
- Pluripotent- give rise to all 3 germ layers (from inner cell mass) but not extraembryonic tissues
- Multipotent- give rise to restricted no. cell types e.g. adult stem cells or haematopoietic stem cells in bone marrow
Explain some features of adult stem cells and their use
- Restricted in use ad multipotent
- Slow rates of division
- Use- replace tissue that is damaged by disease or injury like neurons (Parkinson, Alzheimer’s, stroke), producing insulin for diabetics, heart muscle (to repair after heart attach)
Explain some features of embryonic stem cells and their use. Also where derived from
- Pluripotent- Can form any cell or tissue type
- Diabetes, Alzheimers/ Parkinsons, anaemias, spinal chord injuries
- From embryos after IVF in process called reproductive cloning- can cause immune rejection (but can be modified to prevent this problem) and ethical issues
Outline process or therapeutic cloning or somatic cell nuclear transfer
SCNT- enucleated egg+ agult nucleus and shock causing differentiation onto blastocyst
Theueaputic= Take cells from early embryonic development and keep in perti dish
Therefore forming organ to transplant
- Cell is derived from the host- compatible genetically and no fertilisation so less controversial
Why are embryonic cell- therapies better than using an adult
- Treatment of burns- stem cells grown on biodegradable meshes can produce a new skin for patients, quicker than graft.
- Drug Trials- New drugs can be tested on cultures of stem cells before being tested on animals and humans.
- Developmental biology- studying how multicellular organisms grow from a single cell e.g. fertilised egg and why things go wrong
- Regenerative medicine- develop into a whole organ to transplant
How are abnormal zygotes screened for by the body and by us?
- Spontaneous abortion reduce the incidence of congenital malformations in embryo
- IVF and PCR- molecular screening of embryos for genetic defects is being conducted (single blastomeres from end-stage embryos can be removed and their DNA amplified for analysis
Difference between therapeutic and reproductive cloning
Via SCNT- enucleated egg+ adult nucleus and shock causing differentiation onto blastocyst
Theueaputic= Take cells from early embryonic development and keep in petri dish
Reproductive= take cells from early embryonic development and put in host to get a clone of org
