Lec1&2 Flashcards
embryonic disk?
inside morula, cells form two cavities and this is separated by embryonic disk
ectoderm vs. endoderm vs. mesoderm?
ectoderm– outside– neural plate (nerve system) and neural tube (brain and spinal cord) – “attracto-derm”
NS, epidermis, eyes, ears, nose, hair, nails, skin, glands, tooth enamel
endoderm– inside–GI tract
mesoderm– middle (happens later)– muscles, dermis, CT derivatives (bone, cartilage, blood, dentin, pulp, cementum, PDL)
embryoblast vs. trophoblast?
embryoblast– when traveling after multiple clevage
trophoblast– when implanted
trimesters?
1st- w1~w14
week 1
2 layered germ layers (endo/ecto)
week 2
gastrulation phase, third germ laye= meso
week 3* (really important)
- neuralation phase, neural crest
- notochord as mark of the time of neural crest cells
- neural crest cells from ectoderm and migrate lateral-ventral direction toward future face
when neural crest is established and what will it become?
- during week 3
* neural crest cells migrates into 5 facial processes during week 4
week 4
- neural crest cells migrates into 5 facial processes/premordia
1 frontal nasal process
2 maxillary process (bilateral)
2 mandibular process (bilateral)
- face, nasal cavities, and mouth are derived from neural crest cells
- dentofacial deformities are direct results of neural crest cell migration disruptions
where are maxillary and mandibular process derived?
first branchial arch (of 6 arches) that is called mandibular arch or phryngeal arch
facial bones, muscles of mastication, mockers cartilage, incus, malleuswhat is second branchial arch called?
why branchial arches are important?
- major formation of head and neck (esp. mandibular arch)
* major malformation of head and neck happens here
why is skin a dural organ?
- epidermis from ectoderm
* dermis form mesoderm
branchial arches and cranial nerves?
1st arch– CN5 trigeminal
2nd arch– CN7 faical
3rd arch– CN9 Glossopharnygeal
4th arch– CN10 vegus
week 5
nose, eyes, ears migrating into position
starting to look like a human
developing occurs fast
week 6
mandible begins ossification
week 7
- eyes are migrating medially
- medial and lateral nasal prominences are merging with maxilla
- ossification of maxilla
- palatal parts forming
- primary palate formed from maxilla
week8~10
maxillary and nasal prominence fuse together, (when failed, oralnasal cleft***)
week 11~14
secondary palate fuse completed (when failed, cleft at hard palate***)
why a lot of cleft patients also have hearing lost?
due to the developmental co-occruance
what is second branchial arch called?
Hyoid arch
muscles of facial expression, Reicherts cartilage, stapes
What are the three processes in craniofacial skeleton (bone and cartilage)?
- chondro-genesis: cartilage
- endochondral bone formation: bone from cartilage
- intramembranous bone formation: bone from undifferentiated mesenchymal cells or membranes– eg. sutures or membranes (eg. early in development, brain is covered by thin membrane– bone starts grow here)
Chondro-gensis?
during 4th week, ecto-mesenchyme derived from neural crest cells (also forms osteoblasts for intramembranous later)
40th day, it converts to condroblast to become cartilage
5 steps
- chondroblast makes matrix
- chondrocytes encased in matrix
- the cytes enlarge, divide, produce more matrix (growth within– “interstitial growth”)
- uncalcified matrix (no blood vessels needed)
- membrane covers (but not essential)
endochondral bone formation?
when– 8th week
which ones– ethmoid, sphenoid, occipital (cranial base and calvarium) + mandibular condyle
5 steps
- hypertrophy of chondrocytes & matrix calcifies
- blood vessels and CT invade– calcium deposit occurs behind cartilage
- osteoblasts– produce osteoid
- osteoid calicification
- membrane convers bone and essential
structure: epiphyseal cartilage (outer) growth plate (done after puberty) bone
intramembranous bone formation?
derived from neural crest cells
6th week– first in mandible
8th week– maxilla, mandible (except for condyle– endochondral), upper cranial vault
5 steps
- osteoblasts (from ecto-mesenchyme) produce osteoid matrix
- cells and blood vessels are encased in osteoid
- “appositional growth”
- osteoid calcifies
- membrane covers bone
Growth?
increase in size and number
autonomic process
thing of “how” and “where” cells get bigger!
how does cell gets bigger?
- auxetic– cellular hypertrophy– cell size increase (eg. body builder)
- multiplicative– cellular hyperplasia- cell number increase
- accretionary– intercellular or ECM (around cells) increase
where do cells get bigger?
interstitital– from inside – eg. cartilage, muscle, soft tissue
appositional– from outside– eg. bone and cartilage
- key point 1: bone can grow only appositionally
- key point 2: interstitial grows always first since its from inside/center
what are 7 bone types of bone related to environment?
- fine– fetal stage, very fast
- nonlamellar
- primary vasular– children, peiosteal, blood vessels
- compact corse– endosteum, 2/3 cortical bone, inward growth of cortex into medulla
- chondroid– like cartilage–
- lamellar– slow, adult
- haversian– adult secondary reconstruction of primary vascular bone
tooth movement mechanism?
same as bone metabolism
1) resorption– direct pressure
2) deposition– tension
what is translatory movement?
drift process= relocating
1) deposition of new bone on one side
2) resorption of old bone on the other side
translation is spatial relocation of a bone and bone is enlarged by surface addition at the same time
maxilla and mandible moves by this way
how does condyle of mandible grow?
- start with cartilage that develops separately from body and ramus
- this cartilage fuse around ramous around 4 months of pregnancy
- endochondral ossification
- no epiphyseal plate (so, potentially you can keep growing but capsule supress it)
how does condyle of mandible grow?
- start with cartilage that develops separately from body and ramus
- this cartilage fuse around ramous around 4 months of pregnancy
- endochondral ossification
- no epiphyseal plate!
how does TMJ develop?
- temporal and condylar cell clusters grow toward each other
- btwn 10th and 12th week, mesenchyme cell differentiates into fibrous tissue
- during 12th week, articular disk and joint cavity formed
- start with a little cartilage island (secondary cartilage)
- It builds a connection to the ramus and rest of the mandible and then ossifies via endochondral ossification to become mostly bone
- little bit of cartilage left on the head of the condyle maintains that capability to keep getting bigger and making more bone endochondrally throughout adulthood.
Meckel’s cartilage?
so eventually that blob called the mandibular process forms a piece of cartilage called Meckel’s cartilage. Meckel’s cartilage DOES NOT become the mandible, it just acts like a little framework around which the bone of the actual mandible begins to form. So the mandible (body and ramus) ossify by intramembranous ossification AROUND meckel’s cartilage and then meckel’s cartilage just goes away
