6-2
Bone cells› Osteoblasts› Osteocytes› Osteoclasts› Stem cells or osteochondral progenitor cells
Woven bone: collagen fibers randomly oriented
Lamellar bone: mature bone in sheets Cancellous bone: trabeculae Compact bone: dense
Bones are composed of connective tissue, chemicals, and fats
Solid outer layer - compact bone› Composed of
osteons An inner layer of
spongy bone › a honeycomb of flat,
needle-like projections called trabeculae.
Above: Note the relationship btwn the compact and spongy bone.
Below: Close up of spongy bone.
Volkmann’s canals› Perpendicular to the
haversian canals. › Connect the blood and
nerve supply in the periosteum to those in the haversian canals and the medullary cavity.
Haversian canals › allow the passage of
blood vessels, lymphatic vessels, and nerve fibers.
› Surrounded by layers of bone called a lamella.
osteon
Osteoblasts› Bone building cells› Synthesize and secrete
collogen fibers and other organic components of the bone matrix
› Initiate calcification› Found in the periosteum
and the endosteum Ossification
› Formation of bone by osteoblasts.
› Cells surround themselves by matrix.
osteoblasts
Bone matrix
6-7
Osteocytes. › Mature bone cells.
› Osteoblasts that have become trapped by the secretion of matrix.
› Responsible for maintaining the bone tissue
Lacunae› spaces occupied
by osteocyte cell body Canaliculi
› canals that allow for nutrient filled liquid to fill the lacunae
OsteoclastsCells that ecretes digestive enzymes to digest bone matrix
bone resorptionConcentrated in the endosteum.On the side of the cell that faces the bone surface,
ruffled border. Pumps out hydrogen ions
Create an acid environment that eats away at the matrix.
www.academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/Skeletal/BoneTissue.ppt
Why is there a depression underneath the osteoclast?
What advantage might a ruffled border confer?
What is the name of the third cell type shown here?
What do you think the tan material represents?
Diaphysis - Shaft› Compact bone
Epiphysis - End of the bone› Cancellous bone
Epiphyseal plate - growth plate› Hyaline cartilage; present until
growth stops Epiphyseal line: bone stops
growing in length Medullary cavity: contains
marrow
› In children medullary cavity is red marrow,
› In adults marrow is yellow in limb bones and skull (except for epiphyses of long bones). • Red marrow is found in in
the cavities of the spongy bone of flat bones
Periosteum› Outer is fibrous
› Inner is single layer of bone cells including osteoblasts, osteoclasts and osteochondral progenitor cells
› connected to bone matrix via Sharpey’s fibers
Endosteum. › Similar to inner layer of
periosteum.
› Lines all internal spaces
•Osteocytes•Lamellae•Haversian canals•Osteon•Volkmann’s canals•Lacunae
•Diaphysis•Periosteum•Sharpy’s fibers•Epiphyses •Epiphyseal plate•Epiphyseal line•Yellow marrow•Medullary cavity•Sharpy’s fibers
Consists of organic and inorganic components.› Organic component are secreted by the osteoblasts:
Collagen fibers Elastin
› Inorganic component Calcium phosphate Calcium hydroxide magnesium, fluoride, & sodium.
What if the collagen and elastin were removed from this bone.
What if the Calcium phosphate, Calcium hydroxide and the other minerals were removed from this bone?
Figure 5.2
Prenatal: cartilage model
Fetus: some conversion to bone
Childhood: primary and secondary ossification sites formed
Adolescence: cartilage growth plate elongates
Changes in shape, size, strength:› Dependent on diet, exercise, age
Bone cells regulated by hormones:› Parathyroid hormone (PTH): removes calcium
from bone› Calcitonin: adds calcium to bone
Repair: hematoma and callus formation
Protection: encases most internal organs
Support: allows body positions
Permit movement: muscle attachments for movement
Mineral reservoir: calcium, phosphorus
Classified by degree of movement:› Fibrous joint: immovable (e.g., fontanels)› Cartilagenous joint: slightly movable, cartilage
connection (e.g., backbone)› Synovial joint: freely movable
Figure 5.12a
Joint capsule: synovial membrane + hyaline cartilage
Synovial membrane secretes synovial fluid as lubricant
Hyaline cartilage cushions
Sprains: stretched or torn ligaments
Bursitis and tendinitis: inflammations
Arthritis: inflammation of joints
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