Embryology Flashcards
Intramembranous ossification
Flat bones
Develop directly from mesenchyme in preexisting membranes
What are the 2 sources for bone development?
Mesynchyme (intramembranous ossification)
Cartilage (endochondral ossification)
Endochondral ossification
Most bones
Develop from condensed cartilage
Diaphysis and Epiphyses
Diaphysis
Shaft of bone
Primary center of ossification
Epiphyses
Ends of the bone
Remain cartilaginous several yrs after birth
Secondary centers of ossification
Where does bone lengthening occur?
Epiphyseal cartilage plate at diaphyseal-epiphyseal junction
Osteogenesis imperfecta
Deficiency in Type I collagen
Autosomal dominant
Symptoms: Fragile bones, blue sclera, poor wound healing, hearing loss (50%)
Achondroplasia
Most prevalent form of dwarfism (70%)
Mutation in Fibroblast Growth Factor (FGF-3), Chrom 4P
Autosomal dominant
Endochondral ossification impaired–> Epiphyseal plate small/disorg.
Symptoms: Disproportionately small arms/legs, large head/trunk
Marfan Syndrome
Mutation in Fibrillin gene
Autosomal dominant
Symptoms: abnormal elastin fibers (skeletal, cardiac, ocular). Tall stature, long limbs, hyperextendable joints, long and tapering digits, pectus excavatum, scoliosis.
Gigantism and Acromegaly
Hyperpituitarism
Excessive amt of Growth Hormone (GH)–> IGF-1 levels increased
Gigantism: increased height and excessive body proportions)
Acromegaly: Increased bone growth in hands, jaw, feet
Diagnosis: Oral glucose Tolerance Test–> If GH does NOT decrease–> excess GH
Cretinism
Deficiency in Fetal Thyroid Hormone
Mental retardation, short stature, impaired bone growth, neurologic (muscle tone/coord.)
What is Marfan Syndrome assoc. with?
Ascending aortic dissection
Mitral valve prolapse
Cerebral berry aneurysm
