Lec1&2

Question 1

embryonic disk?

Answer 1

inside morula, cells form two cavities and this is separated by embryonic disk

Question 2

ectoderm vs. endoderm vs. mesoderm?

Answer 2

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)

Question 3

embryoblast vs. trophoblast?

Answer 3

embryoblast– when traveling after multiple clevage

trophoblast– when implanted

Question 4

trimesters?

Answer 4

1st- w1~w14

Question 5

week 1

Answer 5

2 layered germ layers (endo/ecto)

Question 6

week 2

Answer 6

gastrulation phase, third germ laye= meso

Question 7

week 3* (really important)

Answer 7

• 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

Question 8

when neural crest is established and what will it become?

Answer 8

• during week 3

* neural crest cells migrates into 5 facial processes during week 4

Question 9

week 4

Answer 9

• 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

Question 10

where are maxillary and mandibular process derived?

Answer 10

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?

Question 11

why branchial arches are important?

Answer 11

• major formation of head and neck (esp. mandibular arch)

* major malformation of head and neck happens here

Question 12

why is skin a dural organ?

Answer 12

• epidermis from ectoderm

* dermis form mesoderm

Question 13

branchial arches and cranial nerves?

Answer 13

1st arch– CN5 trigeminal
2nd arch– CN7 faical
3rd arch– CN9 Glossopharnygeal
4th arch– CN10 vegus

Question 14

week 5

Answer 14

nose, eyes, ears migrating into position
starting to look like a human

developing occurs fast

Question 15

week 6

Answer 15

mandible begins ossification

Question 16

week 7

Answer 16

1. eyes are migrating medially
2. medial and lateral nasal prominences are merging with maxilla
3. ossification of maxilla
4. palatal parts forming
5. primary palate formed from maxilla

Question 17

week8~10

Answer 17

maxillary and nasal prominence fuse together, (when failed, oralnasal cleft***)

Question 18

week 11~14

Answer 18

secondary palate fuse completed (when failed, cleft at hard palate***)

Question 19

why a lot of cleft patients also have hearing lost?

Answer 19

due to the developmental co-occruance

Question 20

what is second branchial arch called?

Answer 20

Hyoid arch

muscles of facial expression, Reicherts cartilage, stapes

Question 21

What are the three processes in craniofacial skeleton (bone and cartilage)?

Answer 21

1. chondro-genesis: cartilage
2. endochondral bone formation: bone from cartilage
3. 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)

Question 22

Chondro-gensis?

Answer 22

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

1. chondroblast makes matrix
2. chondrocytes encased in matrix
3. the cytes enlarge, divide, produce more matrix (growth within– “interstitial growth”)
4. uncalcified matrix (no blood vessels needed)
5. membrane covers (but not essential)

Question 23

endochondral bone formation?

Answer 23

when– 8th week

which ones– ethmoid, sphenoid, occipital (cranial base and calvarium) + mandibular condyle

5 steps

1. hypertrophy of chondrocytes & matrix calcifies
2. blood vessels and CT invade– calcium deposit occurs behind cartilage
3. osteoblasts– produce osteoid
4. osteoid calicification
5. membrane convers bone and essential

structure:
epiphyseal cartilage (outer)
growth plate (done after puberty)
bone

Question 24

intramembranous bone formation?

Answer 24

derived from neural crest cells
6th week– first in mandible
8th week– maxilla, mandible (except for condyle– endochondral), upper cranial vault

5 steps

1. osteoblasts (from ecto-mesenchyme) produce osteoid matrix
2. cells and blood vessels are encased in osteoid
3. “appositional growth”
4. osteoid calcifies
5. membrane covers bone

Question 25

Growth?

Answer 25

increase in size and number autonomic process thing of "how" and "where" cells get bigger!

Question 26

how does cell gets bigger?

Answer 26

1. auxetic-- cellular hypertrophy-- cell size increase (eg. body builder) 2. multiplicative-- cellular hyperplasia- cell number increase 3. accretionary-- intercellular or ECM (around cells) increase

Question 27

where do cells get bigger?

Answer 27

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

Question 28

what are 7 bone types of bone related to environment?

Answer 28

1. fine-- fetal stage, very fast 2. nonlamellar 3. primary vasular-- children, peiosteal, blood vessels 4. compact corse-- endosteum, 2/3 cortical bone, inward growth of cortex into medulla 5. chondroid-- like cartilage-- 6. lamellar-- slow, adult 7. haversian-- adult secondary reconstruction of primary vascular bone

Question 29

tooth movement mechanism?

Answer 29

same as bone metabolism 1) resorption-- direct pressure 2) deposition-- tension

Question 30

what is translatory movement?

Answer 30

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

Question 31

how does condyle of mandible grow?

Answer 31

* 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)

Question 32

how does condyle of mandible grow?

Answer 32

* 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!

Question 33

how does TMJ develop?

Answer 33

* 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.

Question 34

Meckel's cartilage?

Answer 34

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