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| Question | Answer |
| Potential impact of developmental biology on human health | 1. Understanding growth and differentiation can inform therapy of degenerative diseases. 2. Tissue engineering for transplantation using a patient's own stem or embryonic cells. 3. Decapulation of developmental events can occur in adult disease resulting in illness |
| Development | - In human development, embryos develop in the womb, no new growth but increase in number of cells, resulting in blastocyst, which implants into the uterus of mother. |
| Germ layers | At the end of gastrulation, 3 germ layers are present: - Top layer: ectoderm; epidermus, NS - Middle layer: Mesoderm; trunk skeleton, muscle, dermis, kidney, blood. - Inner layer: endoderm; gut, liver, pancreas, lungs. |
| Susceptibility to developmental defects | - susceptibility corresponds with organ development - most organ development occurs at 3-8 weeks of development; organ systems and limbs develop during this time. - Peak of risk of issue in embryonic development at 5 weeks. |
| Common defects | - Cardiac and blood vessel defects are the most common: 1 in 115 births EG: transposition of the great blood vessel (which can be resolved by arterial switch surgery) Minor defects: - Ankyloglossia: tongue tie - Colombia of the iris - cleft lip/palate - polydactyly- extra fingers/toes |
| Causes of human embroyonic malformations | - Unknown- 54% - Genetic factors- 14% ie chromosomal aberrations such as duplicated/lacking chromosomes, or point mutations. EG downs syndrome - Enviromental factors- 7%; drugs, chemicals, infections, maternal disease. - multifactoral inheritance- 25%, inheritance of multiple genes with one or more enviromental factors |
| Example of defects caused by a single gene | - Cleidocranial dysotosis, where clavicals are thinner or absent, resulting in hyperflexibility and dental abnormality. This is caused by a defect in the RUNX2 gene involved in bone development |
| Example of developmental defects caused by environmental factors | - Thalidomide- morning sickness drug launched before being properly tested. Resulted in children being born without limbs. - Fetal alcohol syndrome- small head, behavioural issues, flat face - Zika virus, transmitted via mosquito bites, results in undergrowth of the NS |
| Brain development in humans | - brain development begins from the hollow neural tube, which form bulges and flextures that shape the brain - the neural tube is derived from the ectodermal germ layer How this happens: 1. between 17 and 23 days of development neurulation occurs; 2. midline of neural plate dips down and borders rise up, meeting in the middle, fusing to form the neural tube - This involves a number of different genes, and if anything goes wrong defects in the neural tube appear (NTDs) |
| Neural tube defects: NTDs: Ectodermal defects | - Which defect occurs depends on which end of the neural tube has been affected. EG: Defect at the top= anacephaly= no brain Defect at the posterior= spina bifta; spinal cord exposed to the enviroment, risk of infection - can be caused by genetic/enviromental factors; folate helps to prevent NTDs. Less severe NTDs: - hyphohidrotic ectodermal dysplasia; affects ectodermal organs- hair, sweat glands, teeth, and in females; mammary glands. Caused by a point mutation in ectodysplasin A gene, can be resolved by injecting Eda protein signalling factors (only been tested in mice). |
| Mesodermal NTDs | - vertebral defects: mesoderm organised into somites, progenitors of vertebrae and axial muscles. *Spondylocostal dysostosis is when this develops in a disorganised way *Achrondroplasia; defect in cartliage cells, results in short stature and undeveloped bones |
| How digit duplications occur | ZHH: morphagen, sonic hedgehog. - different digits formed from the mesoderm are formed by a gradient of ZHH - ZHH is expressed in ZPA (zone of polarising activity) released from here and diffuses across limb bed. High conc= pinky Low conc= thumb - If something goes wron within this gradient, digit duplications can occur. |
| Endodermal NTDs | - endoderm gives rise to the gut, liver, pancreas and lungs. Defects include: - Lung aplasia- absence of lung - Esophegeal atresia/fistula- extra tubes in the respiritoey sistem - Omphalocele- bowel outside the body Other gut issues: - astresia aka 'double bubble' - malrotation; rotation of the gut, strangulation of the gut- leading to ischemia |
| Neural crest | - PNS is neural crest- derived - Neural plate borders that fuse during neural tube formation give rise to migratory cell population; the neural crest. - Neural crest cells are multipotent, and give rise to a number of of cell types. - Form entire PNS inc sensory neurons , autonomic neurons , pigment cells, schwann cells and smooth muscle - Adult neural crest stem cells can be identified in the skin, meaning there is a potential use for therapy. Defects here include congenital aganglionic megacolon= Hirschsprung's disease |
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