Skeletal Structures Flashcards
What are the three divisions of the skeleton and which bones are in them?
- Axial skeleton - head, vertebral column, ribs, sternum.
- Appendicular skeleton - bones of the limbs and bones connecting the limbs to the axial skeleton.
- Visceral skeleton - bones that develop in the viscera or soft structures (i.e. os penis in carnivores).
What are the four functions of bone?
- Skeleton gives an identifiable form to the body of an animal and protects organs.
- Function as levers to perform work.
- Reservoir for calcium and phosphate.
- Red marrow within the medullary cavity of bone is a source of red blood cells.
What is the composition of bone?
95% solid
⅓ of bone is an organic component
⅔ of bone is inorganic hydroxyapatite
5% water
What is the basic microscopic structure of bone?
lacunae - small cavities in bone which contain osteocytes
marrow - found in the medullary cavity of long bones
What are osteoprogenitor cells?
stem cells that when stimulated, develop into osteoblast.
What are Osteoblasts?
differentiated bone forming cells responsible for the production of bone matrix (builds bones).
What are osteocytes?
mature bone cells, derived from osteoblasts.
Enclosed by bone matrix that it had previously laid down as an osteoid when it was an osteoblast.
Maintain the bone matrix and are able to synthesize and resorb matrix to a limited extent.
What are osteoclasts?
(opposite of osteoblasts) bone-resorbing cells.
Large, motile, often multi-nucleated. Derived from stem cells in blood-producing tissue of bone marrow and spleen. Found in resorption bays (Howship’s Lacunae).
What are flat bones?
two plates of compact bone, separated by cancellous bone. They have broad surfaces for attachment of large muscle groups and to protect underlying soft parts.
Example: scapula, pelvic girdle, skull
What are irregular bones?
complex and irregularly shaped bones. Neither flat nor long.
Example: vertebrae
What are sesamoid bones?
small bones embedded in a tendon.
Example: patella
What are short bones?
cube shaped bones, function to diffuse concussion, diminish friction, change direction of tendons.
Example: tarsus and carpus
What are long bones?
bones that are longer than they are wide. Found in the limbs and are the supporting columns and levers for the skeleton.
Example: radius & ulna, tibia
What is the diaphysis?
long shaft of a bone
What is the epiphysis?
two enlarged ends of a long bone
What is the metaphysis?
flared portion joining the diaphysis and the epiphysis in a growing bone; contains the physis
What is the physis (growth plate)?
plate of cartilage between the diaphysis and the epiphysis of immature long bones. Represents the point of growth in a longitudinal direction.
What is the periosteum? (part 1/4 of long bone)
Fibrous covering around bone that is not covered by articular cartilage.
Necessary for bone growth, repair, nutrition and attachment for ligaments and tendons.
Outer layer of dense regular CT (collagen).
What is the Articular cartilage/surface? (part 2/4 of long bone)
Smooth layer of hyaline cartilage covering the epiphysis where one bone forms a joint with another bone.
What is the medullary cavity? (part 3/4 of long bone)
Space in the diaphysis containing marrow.
What is the endosteum? (part 4/4 of long bone)
The fibrous and cellular tissue lining the medullary cavity
What is woven bone?
Immature bone that has been laid down but not organized by secondary remodeling
Can be compact or cancellous
What is compact bone?
Bone that looks solid and is hard and dense.
Outer layer of bones.
Consists of osteons.
What is haversian bone?
Mature bone that has been remodeled
Can be compact or cancellous
What is Cancellous/Spongy/Trabecular bone?
Bone that has visible spaces in it
Empty spaces are filled with bone marrow
Located deep to contact bone
What is the structure of Haversian bone?
Volkman canals
- Blood vessels serving the external surfaces and marrow cavity are perpendicular to the long axis of the bone and are contained within them.
Osteon
- Circular unit of structure of compact bone in haversian system
consists of central haversian canal surrounded by concentric layers of bone, and lamellae
What are the 4 zones of the epiphyseal plate?
Zone of Reserve Cartilage (youngest)
- Chondrocytes begin to divide and organize into columns, forming zone of proliferation
Zone of Proliferation
- Cells divide and produce cartilaginous matrix
- Push epiphysis away from diaphysis, elongating the bone
Zone of Hypertrophy
- Each division of chondrocytes brings about larger cells
Zone of Calcified Matrix (oldest)
- Hypertrophied cells begin to calcify the cartilage matrix
- Calcification and increasing distance from nutritional source causes chondrocytes to die
