Lecture 3-4

Question 1

BONE DEVELOPMENT OCCURS IN TWO PROCESSES

Answer 1

1. ) INTRAMEMBRANOUS OSSIFICATION - FORMS FLAT BONES IN UPPER BODY
2. ) ENDOCHONDRAL - FORMS CORTICAL BONE IN MOST OF THE BODY

Question 2

POST-FERTILIZATION DEVELOPMENT OF FETUS

Answer 2

1. ) FERTILIZED ZYGOTE
2. ) MORULA - PROLIFERATING BALL OF CELLS
3. ) BLASTULA- FLUID FILLED BALL OF CELLS (INNER MASS CELLS = PLURIPOTENT)
4. ) GASTRULA - THREE DIFFERENT GERM LAYERS PRESENT (EACH LAYER = MULTIPOTENT)

Question 3

3 GERM LAYERS

Answer 3

1. ) ECTODERM - “ATTRACTO”DERM FORMS THE NAILS, HAIR, EYES, SKIN, NERVOUS SYSTEM
2. ) MESODERM - FORMS MUSCLE, BLOOD CELLS, BONE, CARTILAGE
3. ) ENDODERM - FORMS LIVER, PANCREASE, LUNGS, INNER LINING OF RESPIRATORY TRACT AND GUT

Question 4

NEURULATION

Answer 4

1. ) NEURAL PLATE W/ NEURAL PLATE BORDER AND ECTODERM ON IT FOLDS INWARD AND FORMS ECTODERM, NEURAL CREST CELLS, AND NEURAL CHORD
2. ) FOLDING OF NEURAL PLATE CAUSES LATERAL PLATE MESODERM AND PARAXIAL MESODERM TO SPLIT IN TWO

Question 5

SOMITES

Answer 5

SERIES OF PAIRED BLOCKS OF MESODERMAL TISSUE THAT FORMS ON THE SIDES OF THE NOTOCHORD - PACKAGES OF ORGANIZED MESODERMAL TISSUES THAT YIELDS DIFFERENT PARTS OF APPENDICULAR/AXIAL SKELETON AND SCLEROTOME (PART OF EACH SOMITE IN A VERTEBRATE EMBRYO GIVING RISE TO BONE OR OTHER SKELETAL TISSUE)

Question 6

NEURAL CREST CELLS

Answer 6

ECTODERMAL ORIGIN (TRANSIENT, MULTIPOTENT, MIGRATORY)

• CAN BE CONSIDERED AS A 4TH GERM LAYER
• FORM CRANIOFACIAL CARTILAGE AND BONE

Question 7

LATERAL PLATE MESODERM

Answer 7

YIELDS LIMBS AND EXTRA EMBRYONIC TISSUE AND SOMATIC MESODERM

Question 8

PARAXIAL PLATE MESODERM

Answer 8

FORMS SOMITES AND HEAD

Question 9

SOMATIC MESODERM

Answer 9

YIELDS BONES, CONNECTIVE TISSUE, LIMBS AND SOME FACIAL CARTILAGE (VISCEROCRANIUM)

Question 10

DIRECTION OF NEURAL CREST CELL DIFFERENTIATION

Answer 10

NEURAL CREST CELLS ARE DIRECTED BY TRANSCRIPTION FACTOR GENES (SOX10, SOX9 AND SOX2)

Question 11

SOX10

Answer 11

CRUCIAL FOR SPECIFICATION, MATURATION AND MAINTENANCE OF SCHWANN CELLS AND MELANOCYTES (I.E. PNS AND NEURAL CREST DEVELOPMENT)

Question 12

SOX9

Answer 12

PROTEIN ACTS DURING CHONDROCYTE DIFFERENTIATION AND HAS AN IMPORTANT ROLE IN NORMAL SKELETAL DEVELOPMENT

Question 13

NEURAL CREST CELLS DIFFERENTIATE INTO…

Answer 13

1. ) CRANIOFACIAL BONES, CARTILAGE AND BRANCHIAL ARTERIES - I.E. VISCEROCRANIUM
2. ) OSTEOBLASTS, OSTEOCLASTS AND CHONDROCYTES
3. ) IF THEY DON’T MIGRATE, THEY BECOME NEURONS, MELANOCYTES AND SCHWANN CELLS

Question 14

MESODERM DIFFERENTIATES INTO…

Answer 14

1. ) LATERAL PLATE MESODERM
2. ) PARAXIAL PLATE MESODERM
3. ) NEURAL CREST CELLS

Question 15

UPPER/LOWER LIMB DEVELOPMENT OCCURS AT HOW MANY WEEKS?

Answer 15

7-8 WEEKS

Question 16

TOOTH DEVELOPMENT OCCURS AT HOW MANY WEEKS?

Answer 16

9-38 WEEKS

Question 17

PALATE DEVELOPMENT OCCURS AT HOW MANY WEEKS?

Answer 17

9 WEEKS

Question 18

REMEMBER THIS SENTENCE

Answer 18

CALVARIAL BONE OSTEOBLASTS OF NEURAL CREST ORIGIN HAVE SUPERIOR POTENTIAL FOR OSTEOGENIC DIFFERENTIATION.
NEURAL CREST DERIVED FRONTAL BONE DISPLAYS SUPERIOR CAPACITY TO UNDERGO OSSEOUS HEALING COMPARED W/ CALVARIAL BONES OF PARAXIAL PLATE MESODERM ORIGIN
**I.E. ORIGIN MATTERS

Question 19

WHAT CRANIAL BONES DEVELOP FROM NEURAL CREST CELLS

Answer 19

SPHENOID, ETHMOID, FRONTAL BONE

Question 20

NEUROCRANIUM OSSIFICATION

Answer 20

INTRAMEMBRANOUS- FRONTAL, PARIETAL, OCCIPITAL, LACRIMAL BONES
ENDOCHONDRAL - (FROM NEURAL CREST CELLS) WINGS OF SPHENOID AND ETHMOID (FROM PARAXIAL PLATE MESODERM) BODY OF SPHENOID, PETROUS PORTION OF TEMPORAL BONE, BASE OF OCCIPITAL BONE

IE. ANYTHING ANTERIOR TO SELLA TURCICA = NEURAL CREST CELLS
ANYTHING POSTERIOR TO SELLA TURCICA = PARAXIAL PLATE MESODERM

Question 21

VISCEROCRANIUM OSSIFICATION

Answer 21

INTRAMEMBRANOUS - PARTS OF MAN./MAX., TEMPORAL BONE, NASAL BONES AND ZYGOMA BONES
ENDOCHONDRAL - MECKEL’S AND REICHERT’S CARTILAGE, THRYOID, CRICOID CARTILAGE