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
what happens if cleft 2-4 do not disappear
Clefts 2-4 disappear and close in most individuals if arch 2 does not grow over and fuse with 4 then cyst forms
how does the face develop
Drag eyes onto the pront of the head
Cell death runs along the midline makes it narrow
Medainl nasal promosience form and fuse to form the bridge of the nose and part of the upper lip
when does the face develop
- week 5 to 7
what happens if the development of the roof of the mouth
- primary palate development - philtre and 4 central incisor teeth
- secondary palate
what makes up the secondary palate
- maxillary palatal shelves
- soft muscular - uvula
how do the maxillary palatal shelves develop
Grow initially inferiorly on either side of tongue
Rotate horizontally when tongue moves into throat - have to wait to about week 7 or 8 for the tongue to drop into the throat
what are week 5/7 pahrgyneal arches and face congenital defects
- cleft lip and cleft palate
wha tis cleft lip
- Common defect
- Failure of maxilla to fuse with the medial nasal prominence
- Cleft between philtrum and rest of upper lip and between central and lateral incisors
what is the cleft between
Cleft between philtrum and rest of upper lip and between central and lateral incisors
wha is cleft palate
- Common defect
- Failure of palatal shelves to fuse (from maxillary prominences)
- can happen due to the Tongue being to large
- Shelves rotate upwards late
- Shelves to small to touch
- Failure of ectoderm to break down to allow fusion
can cleft lip and cleft palate breast feed
- no
- have to have a special bottle
- cannot be fixed for about 3-6 months, make an artificial roof of the mouth that helps suckle the bottle
what does cranial folding do to primitive heart tubes
Cranial folding forces primitive heart tubes into thoracic cavity.
what does lateral folding do to primitive heart tubes
- it means the tubes come closer together and begin to fuse
where does the heart fold and develop originally
above the head
where is the diaphragm forming
above the heart above the head, most cranial
what is the 1st organ to develop
heart
when does the heart begin to pump blood
Starts pumping blood on day 22
when do the heart tubes double in length
Heart tubes doubles in length between day 22 and 24
- Heart loops/bends as ends are fixed
describe the flow through a week 4/5 heart
- Venous tributaries is the inflow
- Comes into the primary atrium
- Then there is a left ventricle
- Then the right ventricle
- Then the outflow
- No chambers at this point it is single tubule system
- When the heart is positioned can we separate the different chambers within the heart
what needs to happen in heart development
- Single tube needs to be divided into 4 chambers
- Atria and ventricles
- Outflow tract also must be partitioned into pulmonary trunk and aorta
- Fetal shunts need to be closed after birth
- Foramen ovale = fossa ovale
- Ductus arterious = ligament arteriosus
what is a common heart defect
- foramen oval not closing properly
- in normal heart function this is not a problem but if you have cardiomyopathy you can force the defect open and this allows the blood to get from the right to the left hand side
- In up to 25% of people a probe can be passed from one atrium to the other.
what symptoms if a Forman oval opening linked to
Linked to having a higher incidence of migraines
Can cause clots which means you have a higher risk of stroke and pulmonary embolisms
what do the kidneys do during embryonic development
- Help produce the amniotic fluid in the 2nd half of embryonic development,
- they increase the amount of amniotic fluid and lung secretions
what are the 3 overlapping kidney systems
- pronephros
- mesonephros
- metanephros
what happens to pronephros
Completely regresses usually in the upper thorax and don’t usually do anything
what happens in mesonephros and what does it develop into
- Upper thoracic to lumbar (L3)
- In males mesonephric duct remains (ductus/vas deferens)
- Embyronic kidney and does produce urine as amniotic fluid
what happens in metanephros
- Ureteric bud (outgrowth of mesonephric duct) grows into the metanephric tissue
- Fomred by both mesoderm and a growth from the endoderm part so that the uteric bud, which is the outflow of the mesodermic duct, induces the mesoderm to become mesonephric tissue and become the kidney
where do the kidneys start off developing
- they start in the pelvis attached to the renal artery to the aorta
how do the kidneys move upwards
- they start in the pelvis with the renal artery attached to the aorta
- they migrate up as a whole organ
each time they move upwards they have to readjust and reform its blood supply - the adrenal glands act as a stop point when they kidneys run into the adrenal glands they stop migrating upwards
what issues can you have with kidney migration
- one can remain in the pelvis or both of them can
- doesn’t really have an big effecting issue or is a problem
name the kidney defects that you can have
- Pelvic kidney
- Horseshoe kidney
- Bifid ureter - two ureters
what week do limbs develop in
week 5 - 8
describe the development of limbs
- need cell death to develop the limb in order to form fingers and toes
- cell death to serrate fingers, joints, and to shape the limbs to get the right size and shape
what are some limb defects
- Syndacyly – this is where the fingers are webded
- Polydactyly – has extra fingers
- Polon syndrome – loss of pec major
- missing muscles are a very common anatomical variation
what is the blood supply of the primitive foregut
- aortic arch and celiac artery
how does the stomach develop in week 5
Rotates 90-degrees around craniocaudal axis so greater curvature lies to left and lesser to right.
what part of the stomach does the left and right vagus innervate
Left vagus innervates anterior wall
Right vagus innervates posterior wall
describe how the midgut develops
It herniates and rotates around the axons, it brigns with it the superior mesenteric artery and the vitelline duct and cecal diversticumum (becomes lagre intestines) Vitellne duct becomes small intesitnes Rotates 180 degrees And then comes back in Cecum rotates 90 End up with 270 degrees of rotation
how many degrees does the midgut end up rotating
270 degrees
when does gut malrotation happen
1in 3500-6000 live births
describe what happens in non rotation of the gut
- Cecum is in upper abdomen just left of mid-line
- Duodenaljejunal segment lies anteriorly and just to the right of midline
- As mesentery not fixed it allows axial rotation of the midgut around the superior mesenteric artery
- Resulting in midgut volvulus with the potential for intestinal obstruction, ischemia, and necrosis
what organs are intraperiotenal
At first all part of the small and large intestines have a mesentery from which they are suspended
what organs are retroperitoneal
Duodenum (pancreas)
Ascending colon
Descending colon
what is omphalocele
Failure of umbilicus to close completely combined with failure of mid-gut to herniate back into abdominal cavity fully
how are omphalocele babys born
they are born in C section as a vaginal birth will do damage to the intestines
how is omphalocele fixed
- Can get a natural protective shield around the loops of the intestines and as the baby grows over about 3-6 months
- The loops of the intestines fold back into the abdomen
- At 6-9 months end up with a loose abdomen but everything is back
Surgically close this off
what are some vitelline duct abnormalities
2-4% of people have a small portion of vitelline duct forming outpocketing of ileum
Does not usually cause any symptoms
what is gastroschesis
Usually to right of umbilical cord
Body wall defect
