How does the gross anatomy of long bones differ from short, flat, and irregular bones?
Does not have shaft or epiphyses
Does not have medullary cavity
Describe in detail the organic and inorganic components of bone.
Organic components: 35% by mass
Osteoid:organic part of extracellular matrix, ground substance (proteoglycans and glycoprotiens), collagen fibers (made by osteoblasts)
Inorganic components: (65% by mass) Mineral slats (mostly calcium phosphate) Produce hardness of bone
What are the 4 cell types found in bone, what are their main functions?
Osteogenic cells: mitotically active stem cell, found in membranes (periosteum and endosteum)
Osteoblasts: immature cells; secrete bone matrix
Osteocytes: mature cells; occupy lacunae; maintain bone matrix
Osteoclasts:large multinucleated cells that breakdown bone
Describe in detail the microscopic anatomy of compact bone. Your answer should include the structure and function of the osteon. Your answer should include: Haversian canal, Volkmann's canal, and canaliculi.
Haversian:(central canal) blood vessels and nerve fibers
Volkmann's:(perforating canals) connect blood supply of osteons to medullary cavity
Canaliculi:Hair like canals that connect lacunae, allow osteocytes to communicate via gap junctions
Describe the process of endochondrial ossification. How does this differ from intramembranous ossification?
Endochondral Ossification: bone replaced by hyaline cartilage
Intramembranous Ossification:is when bone develops froma fibrous membrane but only happens in cranial bones and clavicles are also formed this way)
Describe in detail how post-natal growth of long bone works, including the role of “remodeling” in maintaining proper bone shape and proportions.
(Occurs at epiphyseal plate and articular cartilage)
Growth in length: Intersitial (chondrocytes and osteoblasts from withing)
Growth in width:s appositional (osteoblasts beneath periosteum.
Bone remodeling: Maintains bone proportions, involves bone formation and reabsorption
What is the purpose of regular bone remodeling? How often does it occur?
Bones are dynamic organs:5-7% of bone mass is recycled every week
Spongy bone is replaced every 3-4 years
Compact bone is replaced every 10 years
The purpose of regular bone remodeling is to maintain homeostasis
Describe the two mechanisms involved in bone remodeling.
Osteoblats: Deposit new bone matrix
Osteclasts: Breakdown and reabsorb bone matrix
Describe the role of parathyroid hormones in the control of blood calcium levels and bone remodeling.
The role of parathyroid hormones is to stimulate the osteoclasts in response to the amout of calcium levels. The more parathyroid hormones the most osteoclasts know how much to secreate the less hormones the less amount of bone that are being secreated
Describe how mechanical stress affects bone deposition.
Bones structure reflects physical demands:
Loading results in bending and bending results in growth.
Bones are thicker where they are most likely to buckle or break .
Describe the 6 types of fractures discussed in table 6.2
Comminuted: Bone fragments into three or more pieces
Compression:Bone is crushed
Spiral:Ragged break occurs when excessive twisting forces are applied to a bone.
Epiphyseal: Epipysis separates from the diaphysis along the epiphyseal plate
Depressed: Broken bone protion is pressed inward
Greenstick:Bone breaks incompletely, much in the way a green twig breaks. Only one side of the shafts break the other side bends.
Describe how fractures are classified.
Position of bone after fracture, non-displaced vs.displaced
Completenessof break complete vs. incomplete
Penetration of skin open (compound) vs. Closed (simple)
Fractures cam also be described by location,external appearance, and/or nature of the break
Describe osteoporosis: What is it? What causes it (especially in women)? What is the effect of exercise?
Osteoporosis: Occurs when bone reabsorption happens faster than bone deposit.
Sex hormones:(estrogen in females) restrain osteoclasts and promote bone deposit.
Exercise helps promote bone growth and is very effective against bone degeneration