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Organogenesis
Sem1
Question | Answer |
---|---|
What is the name given to the process of organ formation? | Organogenesis |
When does organogenesis usually start? | In the first trimester of pregnancy |
When can gender be determined? | Around the 12th week of pregnancy |
When is 'it' referred to as an embryo? | From conception to the 9th week (LMP) |
When is 'it' referred to as a foetus? | From the 9th week (LMP) until the rest of the term |
How do the lungs develop? | Branching morphogenesis |
Which germ layers supply most of the alveoli of the lungs? | Endoderm and mesoderm |
Which germ layer is responsible for neural innervention? | Ectoderm |
Which germ layer gives rise to musculoskeletal support? | Mesoderm |
Which longitudinal channel will later become the digestive tract? | Primitive gut |
Which germ layer does the GI system initially develop from in week 2/3? | Endoderm |
What does the mesoderm contribute regarding GI system development? | Messentry, smooth muscle and blood vessels |
What does the ectoderm contribute regarding GI system development? | Enteric nervous system |
What do the following form? A)Foregut B)Midgut C)Hindgut | A)Oral cavity, oesophagus, trachea and stomach B)Small intestine and pancreas C)Colon |
Where does somite development occur? | Alongside the neural tube, in pairs |
When does somite development occur? | Starts around day 19 post-fertilisation |
How does somite development occur? | Develops in succession from anterior to posterior. A new somite pair develops every 90 minutes, and 44 develop in total |
What does somite development result in? | Produces muscle, and vertebral and rib bones |
When does neural tube closure usually occur? | Days 23-26 post-LMP |
How does the neural tube close? | The neural plate (neural ectoderm) rolls up to form the neural tube, with the neural crest forming at the boundary with the ectoderm |
Why is neural tube closure important? | Closure is important for the development of the brain and spinal cord. Failure to close could lead to conditions such as Exencephaly or Spina Bifida |
What does embryonic folding result in? | The entire surface being covered with ectoderm |
What does the ectoderm later become? | The epidermis of the skin |
What happens to the mesoderm? | The mesoderm splits into two layers; One adhering to the ectoderm, the other to the endoderm. This creates the coelom |
When does nervous system development start to occur? | 19-21 days post-fertilisation |
From which layer does the nervous system develop? | The ectoderm |
What gives rise to the brain? | The neural plate, in the anterior region |
What gives rise to the spinal cord? | The neural tube along the dorsal region |
Which two cavities can the body cavity be divided into? | Thoracic cavity and Peritoneal cavity |
What separates the Thoracic and Peritoneal cavities? | The diaphragm |
What does the Thoracic cavity sub-divide into? | The Pleural and Pericardial cavities |
Through what three ways can birth defects arise? | -Genetic (inherited or de novo mutations) -Environmental (exposure to teratogens) -Infections (maternal disease) |
How does the ear develop? | From placodes (ectodermal thickening visible on surface) |
Why is the development of the ear important? | For sensory organ formation |
How does the inner ear develop? | From the Octic placode: visible from week 4, disappears from surface by week 5 |
When does the embryonic stage of pregnancy occur? | The 6 weeks that follow the first 16 days post-fertilisation |
How does the shape of the embryo change during the embryonic stage of pregnancy? | -The cephalic and caudal ends curve around the yolk sac so that the head and tail are almost touching in a C-shape -At the same time, lateral surfaces of the disc fold around the sides of the yolk sac to form the ventral surface of the embryo |
When does limb development occur? | External surfaces are visible from early week 4 |
How do the limbs develop? | -Buds project outwards -Patterning is important; need to specify proximal, distal, dorsal, ventral -Forelimb is present first |
What shows the precursors of digits? | Condensations of cartilage |
How do the digits separate? | Apoptosis between the digits |
When does development of the heart start to occur? | Days 22/23 post-fertilisation |
Where is development of the heart visible? | On the ventral surface |
When does the heart start to beat? | Around day 45 |
What do the kidneys develop from? | The urogenital ridge |
How do the kidneys develop? | Branching morphogenesis |
What are the 3 stages in kidney development? | Pronephros (day 18) Mesonephros (day 24) Metanephros (day 35) |
What does the eye develop from? | The Optic placode |
When does development of the eye occur? | Visible from the end of the 4th week |