Second half of Chapter 7 Flashcards
Compact bone
Histology of compact bone reveals osteons (haversian systems)
Compact bone:Concentric lamellae and
Perforating (Volkmann) canals
Concentric lamellae surround a central (haversian) canal running longitudinally
Perforating (Volkmann) canals—transverse or diagonal passages
Compact bone:Circumferential lamellae and Interstitial lamellae
Circumferential lamellae fill outer region of dense bone
Interstitial lamellae fill irregular regions between osteons
Spongy bone consists of:
Lattice of bone covered with endosteum Slivers of bone called spicules Thin plates of bone called trabeculae Spaces filled with red bone marrow.Few osteons and no central canals All osteocytes close to bone marrow
Provides strength with minimal weight
Trabeculae develop along bone’s lines of stress
Bone marrow
Bone marrow—soft tissue occupying marrow cavities of long bones and small spaces of spongy bone
Red marrow (myeloid tissue)
Red marrow (myeloid tissue)
Contains hemopoietic tissue—produces blood cells
In nearly every bone in a child
In adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur
Yellow marrow
Yellow marrow found in adults
Fatty marrow that does not produce blood
Can transform back to red marrow in the event of chronic anemia
Ossification or osteogenesis
Ossification or osteogenesis—the formation of bone
In the human fetus and infant, bone develops by two methods
Intramembranous ossification
Endochondral ossification
Intramembranous Ossification
Produces flat bones of skull and clavicle in fetus
Thickens long bones throughout life.Note the periosteum and osteoblasts
osteoid is the unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue.
Endochondral Ossification,
During infancy and childhood, the epiphyses fill with spongy bone
Cartilage limited to the articular cartilage covering each joint surface, and to the epiphyseal plate.By late teens to early 20s, all remaining cartilage in the epiphyseal plate is generally consumed
Bone Growth and Remodeling:Ossification
Ossification continues throughout life with the growth and remodeling of bones
Bones grow in two directions
Length
Width
Bone Elongation:Epiphyseal plate
Epiphyseal plate—cartilage transitions to bone
Functions as growth zone where bone elongates
Has typical hyaline cartilage in the middle with transition zones on each side where cartilage is replaced by bone.
Bone Elongation: Metaphysis
Metaphysis is zone of transition facing the marrow cavity
interstitial growth
interstitial growth—growth from within
Bone elongation is a result of cartilage growth within the epiphyseal plate
epiphyseal line
Epiphyses close when cartilage is gone—epiphyseal line of spongy bone marks site of former epiphyseal plate
Achondroplastic dwarfism
Long bones stop growing in childhood
Normal torso, short limbs
Failure of cartilage growth in metaphysis
Spontaneous mutation produces mutant dominant allele