Embryology - major organ system development Flashcards
what does gastrulation produced
- Ectoderm – skin and nervous system
- Mesoderm – connective tissue
- Endoderm – gut tube prodimently , lungs, liver, pancreas
- All body axes are specified
what does the ectoderm make
skin
- epidermis
Nervous system
- CNS
- Neural Crest (PNS)
what does the mesoderm make
connective tissue
what does the endoderm make
gut tube prodimently , lungs, liver, pancreas
what are the several developmental processes that are ongoing
- proliferation
- apoptosis
- movement
what does proliferation do in development
- we start as a single cell therefore proliferation needs to happen so we end up as a multicellular organism,
- we actually have more proliferation than we actually need, for example in the nerouvs system we make 50% more cells than we need therefore we need apoptosis
what does apoptosis do in development
– this gets rid of the excess and shape of the organ
- makes sure that it is not too big and in the wrong place
- makes sure that the toes, joints separate
what does movement do in development
– cells migrate and move from one area to another,
- for example the neural crest cells which produce the peripheral nervous system start as part of the ectoderm and then they undergo gastrulation to get to the peripheral system to make the schwann cells,
- it will migrate underneath all the layers of the skin, produce teeth, bone,
- they will also migrate intot he gut to form the enteric nervous system,
- they also migrate into the adrenal gland and form part of the adrenal gland that is the sympathetic nervous system
- even whole organs will move such as the kidney
what happens if you take a cuts through the middle of the embryo
- you see the outer layer which is ecotderm
- the middle layer which is the mesoderm
- the bottom layer which is the endoderm
- running through the midline of the mesoderm is a green structure, called the notochord
what does the notochord do
- this is an organising centre
- it produces lots of secreted substances that influence the cells that surround it for example by change there cells
- only present in embryonic development
what happens to the notochord after development
- it is incorporated into the intervertebral discs
what happens in week 4
neurulation
describe the process of neurlation
- The notochord is producing substances that will influence the cells above to change there shape, so rather than being cuboidal the cells directly above become columnar,
- start to produce a thickened area above the notochord called the neural plate – this is the start of the CNS
- At the boundary between neural plate and surface epidermis is where the neural crest is, as you get further away you have lower concentrations so the area of the neural crest as the notochord substance being released is in lower concentration
- Columnar cells begins to change there shape at certain points
- The acting cytoskeleton of the columnar cells become a trapezoid kind of shape which creates a bend this bend is called the neural groove
- If we get a few more bends the columnar cells begin to pinch at the apical surface then we get more bends and eventually if we continue to bed the light blue surfaces fuse and form a tube,
- and the surface underneath forms a circle these are the surface ecotderm and CNS
- The green cells at the boundary of the neural crest become more mesodermal like and migrate to where they need to go, they migrate underneath the surface ectoderm and into organs
- The neural tube then goes up to the top which is the brain and down to the bottom which is the spinal cord, now have a tubular structure that runs from the head down to the sacrum
what is the start of the CNS called
the neural plate
what is the basic idea of what happens in neurlation
Cuboidal to columnar down midline of ectoderm
Signals from notochord
Columnar cells at base and sides cause bending
Neural crest cells detach and migrate to form peripheral nervous system
what are some neural crest cells derivatives
Sensory neurons
PNS glia – schwann cells and satellite cells
Enteric nervous system
Sympathetic ganglia
Adrenal medulla
Melanocytes
Cartilage, teeth, connective tissue and bone of skull
what are week 4 nuerlation congenital defects
Spinda bifida
what also happens in week 4
branchial and pharyngeal arches develop
what does the frontanasal prominence become
- the forehead and nose
what does the optic placed become
the eye
describe the pharyngeal and branchial arches
- they have become modified to form the upper and lower jaw and structures int he neck
- on the outside they are covered with a surface ectoderm and then a mesoderm in the middle and then a endoderm on the inside
what does the endodermal epithelium of the pharyngeal and branchial arches become
- it become the tongue
between the arches there is never a …
complete slit between there should always be endoderm mesoderm ecoderm
describe what there is on the inside and outside of the branchial and pharyngeal archers
On the outside there is a Ecotedermal cleft
On the inside there is a Endoderm pouch
what is in each of the pharyngeal arches
In each of the arches there are a skeletal structure, group of muscles that form that are innervated by a cranial nerve and an artery and there will produce cartilage and or bone,
arch 6 is small so we…
Arch 6 is small so we tend to forget about it only look at arch 1-4
what is the aortic arch, cranial nerve, examples of branchiomeric muscles, and skeletal deviates of arch
- 1
- 2
- 3
- 4
Mandibular
- 1 = maxillary artery = trigeminal nerve = muscles of mastication= malleus, incus, sphenomandibular, mucked cart
hyoid
= 2= hyoidstrapedia artery= facial= muscles of facial expression = stapes, styloid process, stylohyoid ligament
= 3= internal carotid artery= glossophargenal = stylophargenous = parts of hyoid cartilage
=4= right subclavian artery and aorta = vagus= pharyngeal and laryngeal msucualrutre = laryngeal cartilage
what are the pharyngeal arches
1 2 3 4 6
what forms between cleft 1 and 2
external auditory meatus
what forms between
- pouch 1 and 2
- pouch 2 and 3
- pouch 3 and 4
- pouch 4 and 6
- middle ear eustchain tube
- supra-tonsillar fossa
- thymus and parathyroid gland
- thymus parathyroid gland and ultimobranch body – part of the calcium hoemoestatsis system
what clefts usually disappear in development
Clefts 2-4 disappear and close in most individuals