CFD 4 - arches 1 Flashcards
(24 cards)
What are the 4 fundamental aspects of developmental biology?
- proliferation/growth - size
- pattern formation - right place, right time
- morphogenesis - shape
- differentiation - type
What is pattern formation?
the process by which cells in a developing embryo acquire identities that lead to a well ordered spatial pattern of cell activities
What is organ rudiment usually triggered by?
an epithelial signal, an induction - allows morphogenesis and proliferation to take place over a specific amount of time
What is a signalling centre?
the organiser - will organise specific growth factors to ensure that there are the right types of cells growing for the tissue/structure being formed
What are signalling gradients?
within a specific area, you’ll get a switch on of genes which will make that specific tissue
- there’s a gradient of the signal, and only at the right points will it actually form the correct tissue
What is cell migration?
cells migrate into the area, do what they need to do and undergo differentiation once they get to where they need to be - e.g. by undergoing EMT or MET
What are the primary germ layers?
- ectoderm - skin, neural tube etc
- mesoderm - just about everything else
- endoderm - gut
- (neural crest/ecto-mesenchyme - structures of the head and neck)
When does formation of branchial arches usually start?
between days 24/25
What developing structure affects how the branchial arches differentiate into the different tissues?
the developing spinal column
What cartilage forms in arch 1?
Meckel’s cartilage, a very transient structure
What cartilage forms in arch 2?
Reichert’s cartilage, a very transient structure
After what point have the transient Meckel’s and Reichert’s cartilages basically disappeared?
after 20 weeks
- there are the odd remnants of Meckel’s cartilage
What does Meckel’s cartilage differentiate to form?
certain bone structures within the ear and upper face
What does Reichert’s cartilage disappear to form?
the styloid ligament
What is the stromatodeum?
developing oral cavity, formed from the disintegration of a layer of cells, allowing growth factors to seep into this area
When do the pharyngeal arches appear?
in 4th and 5th week of development
What are the pharyngeal arches separated by?
- clefts/grooves - externally
- pouches - internally
What causes the development of the pharyngeal arches?
the neural crest cells migrating into the head and neck region
What does the first pair of pharyngeal arches form?
the primordium of the jaws (lower and upper jaws)
What do the first pair of pharyngeal arches appear as?
- surface elevations lateral to the developing pharynx
- soon the other arches appear and are obliquely disposed around ridges on each side of the future head and neck regions
What do the pharyngeal arches exclusively contribute to?
the formation of the face, nasal cavities, mouth, larynx, pharynx and neck
What happens to the arches during the 5th week?
the second pharyngeal arch enlarged and over grows the 3rd and 4th arches, forming the ectodermal depression called the cervical sinus
What has happened to the arches by the end of week 7 of development?
the 2nd and 4th pharyngeal grooves and cervical sinus disappear, giving a smooth contour
What does a typical pharyngeal arch contain?
- an aortic arch - artery that arises from trunk of primordial heart
- a cartilaginous rod that forms the skeleton of the arch
- muscular components that differentiate into the muscles of the head and neck
- a nerve that supplies the mucosa and muscles derived from the arch
