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ANS 205: Physiology of the bone

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relating to bones


mature cells


immature cells

Removal of inorganic salts and minerals causes the bone to be


The organic components of bones are

bone cells and osteoid

Bones cells include

osteocytes, osteoblasts, osteoclasts


mature bone cells


immature bone cells


specialized cells derived from blood that eat away bone


organic part of the matrix that is made of collagen, polysaccharides and GAGS—contributes to resilience and toughness of the bones


glycosaminoglycans, complex modified sugars

Inorganic components of bone

calcium and phosphorus salts (provide hardness and rigidity to the bone)

CaPO4 Calcium Phosphate is ____% of inorganic salt in the bone


Inorganic component can be removed by soaking in dilute


Decalcified bone_____ (maintains/loses) structure


When the osteoid is removed the bone becomes_____ and is prone to _____

brittle, breaking

Describe Osteoblasts

bone-forming cells found in all bone surfaces, they synthesize and secrete collagen fibers and other organic components of bone matrix (GAGS), serve as a framework for the deposition of calcium and phosphate salts

Osteoblasts are the _____ for the bone to be laid down and mineral deposition


Describe Osteocytes

Mature, nondividing osteoblast surrounded by matrix, lying within lacunae. They still make bony matrix but are stuck in lacunae and do not continue to proliferate, continually lay down osteoid or organic substance

Describe Osteoclasts

large multinucleate cells that are responsible for the active erosion of bone minerals. Contain large numbers of mitochondria and lysosomes (eat away at bone). Formed by the fusion of macrophages.

_____ bone consists primarily of laminated tubes called osteonal systems


Each _____ consists of a central canal (blood vessels and nerves) surrounded by circular plates of bone


The lacunae is a cavity containing _______ bone cells


The lamellae are plates or rings around the

central canal

Canaliculi are tiny canals that radiate from the ______ to the ______

central canal to the lacunae

All central canals are connected perpendicularly by the

Volkmann’s canals

Define ossification

formation of true bone by deposition of calcium salts in a bony matrix of osteoid tissue

Define calcification

depositing calcium salts within tissues

What is the primary center of bone formation within the shaft

center of ossification

Endochondral ossification begins

within the cartilage model

Intramembranous ossification begins

as a thin membrane

List the five steps of endochondral ossification

1. Formation of bone collar around hyaline cartilage model, 2. Cavity formed in the hyaline cartilage model, 3. Invasion of internal cavities by periosteal bud and spongy bone, 4. Formation of medullary cavity and ossification continues, secondary ossification centers appear in epiphyses, 5. Ossification of the epiphyses and hyaline cartilage only left in epiphyseal plates and articular cartilage

List four steps of intramembranous ossification

1. Ossification center appears in fibrous connective tissue membrane, 2. Bone matrix secreted within fibrous membrane and calcified, 3. Woven bone and periosteum form, 4. Results in compact bone surrounding a cencellous bone core

Bone __________ is the continuous turnover of bone in mature animals


During remodeling bone can

shrink (atrophy), increase in size (hypertrophy), repair, rearrange

The activity of bone cells is regulated by these two hormones

parathyroid hormone (PTH), calcitonin

The parathyroid hormone ________ serum calcium by _______ net release of calcium salts

increases, increasing

PTH increases the activity of what type of bone cells

osteoclasts (more eating of bone to add calcium in blood)

Calcitonin’s primary effect is to _______ osteoclast activity and ______ serum calcium

reduce, lowering

Calcitonin increases osteoclast activity so it is _______ calcium in the bone


Define fracture

a break in the continuity of bone

Define simple fracture

skin stays intact (unbroken)

Define open fracture

would from the exterior is in contact with the broken bone

Define greenstick fracture

one side of the bone is broken/splintered while the other side is intact but bent

Define complete fracture

bone is broken across into two parts

Define physeal fracture

located at the junction of an epiphysis and diaphysis

Define comminuted fracture

the bone is broken or shattered into smaller pieces

Granulation tissue consists of two things

fibroblasts and capillaries

Osteoblasts (from peri and endosteum) divide rapidly after injury to produce large amounts of


Define callus

a lump of connective tissue formed around the granulation tissue

After apposition and immobilization occur, how does a fracture heal

the blood clot is invaded by connective tissue cells called granulation tissue. The osteoblasts produce osteoid and the callus forms and then in mineralized. After healing the spontaneous deformity correction occurs to return the bone to normal shape/size

The amount of spontaneous correction depends on these 5 factors

age of the animal, blood supply of the bone, degree of correction required, presence/absence of infection, amount of damage to tissues



Bone TB is an infection caused by _________ which attacks the ____ and ends of the ______

mycobacterium tuberculosis, spine, long bone

Osteomyelitis is the inflammation of bone and bone marrow that is caused by ______ that enters via blood vessels/wounds

bacteria (staphylococcus/streptococcus)

Osteodystrophy is an abnormality in bone development due to dysfunctional ___ and ___ regulation

calcium and phosphorus

Rickets occurs in young animals and osteomalacia occurs in old animals as a result of inadequate ____

mineralization of osteoid

Achondroplasia is a hereditary condition in which metaphyses fuse early but grow in diameter resulting in

dwarfism ex. dachshund dogs and dwarf cattle