deck_2833704 Flashcards
What do the mesenchymal cells of paraxial mesoderm-derived somites generate?
chondroblasts and osteoblasts that form the vertebral column via endochondral ossification.
What does the lateral plate mesoderm split into?
1) the parietal (somatic) layer
2) the visceral (splanchnic) layer
what do mesenchymal cells of the parietal layer generate into?
chondroblasts and osteoblasts that form the scapula, clavicle, and bones of the upper limb.
Describe the first step of endochondral ossification of long bones.
endochrondral ossification of long bones begins by formation of thin bony collars around the diaphysis or shaft of the cartilaginous replicas laid down by the perichondrium of the cartilage (which is just connective tissue). This perichondrium then becomes a periosteum.
what occurs after the bony collar periosteum is established?
As soon as the bony collar is established, the internal cartilage matrix begins to calcify and the chondrocytes hypertrophy and die. Osteoblasts, angiogenic capillaries, and macrophages from the periosteum then invade the diaphysis and replace these dead chondrocytes with trabecular bone, forming the primary ossification center in the diaphysis. These periosteal capillaries also force any living chondrocytes to the ends of the bone (growth plates aka epiphyses).
How is lengthening of long bone achieved?
chondrocytes that were forced to the epiphyseal plates (growth plates) at either end of the long bone, organize themselves into longitudinal cellular columns and proliferate away from the diaphysis. The innermost chondrocytes continue to degenerate (hypertophy and accumulate lipids, glycogen, and alkaline phosphatase) until they eventually die and leave behind a calcified cartilage matrix which is then ossified later by osteoblasts.
why is acondroplasia associated with skeletal dysplasia (for example, dwarfism)?
Acondroplasia is the most common form of skeletal dysplasia and it primarily affects long bone. It results in stunted growth of long bones due to a mutated growth factor receptor which usually has an inhibitory affect on growth of long bone. The mutation makes the receptor constitutively active and thus continually inhibits growth of long bone.
what transformation forms compact bone and where is it located?
The transformation of primary osteons into mature osteons forms compact bone which is located on the outer part of the diaphysis.
In neonates, what does residual trabecular bone in the diaphysis form and where can secondary ossification centers be found?
residual trabecular bone in the diaphysis forms the marrow cavity where bone marrow resides and secondary ossification centers can be found in the epiphyses.
What happens to the epiphyses at age 10? …and at skeletal maturity?
At age 10 the epiphyses mature into cores of trabecular bone which are covered by compact bone. The growth plates still remain active until puberty, and at skeletal maturity the epiphyses and diaphysis converge (growth plate disappears, leaving a continuous connection of ephysiseal and diaphyseal bone).
What makes up the glenohumeral joint (shoulder joint)?
the articulation of the head of the humerus with the glenoid cavity of the scapula.
How much of the humeral head is handled by the glenoid cavity?
The glenoid cavity only handles a third of the humeral head.
what is the purpose of the glenoid labrum?
The glenoid labrum is made up of concentric rings of Type I collagen fibers and its purpose is to attach to the rim of the cavity and slightly deepen it.
