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56 terms

Bone

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compact bone
dense outer layer
spongy bone
internal to compact bone
network (trabeculae)
trabeculae
the irregular latticework of thin bony plates in spongy bone tissue
red or yellow marrow
medullary cavity contains..
marrow
epiphyses
1. expanded ends of long bones
2. exterior is compact bone, and the interior is spongy bone
3. joint surface is covered with articular (hyaline) cartilage
4. Epiphyseal line separates the diaphysis from the epiphysis.
diaphysis
shaft of a long bone
compact bone
surrounds medullary cavity
Periosteum
outer- dense irregular connective tissue
inner- osteoblasts and osteoclasts
nerve fibers/blood/lymphatic vessels
-nutrient foramina
nutrient foramina
minute holes in the bone surface that allows blood vessels to penetrate
sharpey's fibers
Collagen fibers which penetrate the bone. The attachment is so strong that even with severe traction injuries the tendon usually does not "pull out" of the bone but instead either tears or a fragment of bone is pulled out with the inserted collagen fibers (known as an avulsion fraction).
Endosteum
Connective tissue membrane covering internal bone surfaces

-covers trabeculae
-lines canals
-contains osteoblasts/osteoclasts
Structure of short, irregular, flat bones
compact bone on the inside
spongy bone (diploe) on inside
no diaphysis/epiphyses
bone marrow between trabeculae
location of red marrow: infants
found in medullary cavity and all areas of spongy bone
location of red marrow: adults
found in dipole of flat bones and the head of the femur and humerus
haversian system
Central canals surrounded by osteons; contain the blood vessels and nerves that serve the bone
lamellar bone
mature bone present in normal adult stages; collagen fibers are perfectly arranged in a parallel pattern so they can withstand torsional stress
lamellae
Concentric rings made up of groups of hollow tubes of bone matrix
Volkman's canals
Channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversion Canal
Osteocytes
Mature cells, develop from osteoblasts, control day-to-day activities (each occupies a lacuna, a pocket sandwiched between layers of matrix
lacunae
small spaces between the lamellae which contain osteocytes
canaliculi
small hair-like canals extending from the central canal. Allow for diffusion of nutrients, waste products, hormones, etc. to lacunae.
Strength: Compact Bone
located where stressed are limited in direction
Strength: Spongy Bone
located where stresses are weaker or multi-directional
How to trabeculae help with bone stress
they line up alone the line of force to help deal with multi-direction foraces
osteoblasts
bone forming cells - perimeter of bone
osteocytes
maintain bone - inside bone
osteoclasts
large cells that resorb or break down bone matrix, releasing calcium ions into the blood - perimeter of bone
osteoid
Unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen
hydroxyapatites
mineral salts; calcium phosphate & Salts
Without minerals bone...
is flexible
without collagen bone
shatters
how does ossification through age?
embryo - ossificaiton -> bone formation

early adulthood - ossification -> bone growth

adult - ossification -> bone remodeling/repair
Intramembranous ossification
Bone growth within a membrane (mesenchyme)
Forms flat bones of the skull, some facial bones, mandible, and clavicle
endochondral ossification
the most common bone formation process, which involves the replacement of hyaline cartilage (developed by mesenchyme) with bone
Long bone growth
Cartilage proliferation on epiphyseal side of epiphyseal disk
• Ossification (conversion to bone) occurs on diaphyseal side of epiphyseal disk
rate of bone growth...
outpaces that of cartilage growth
bones: sex hormones
estrogen and testosterone tell you when to stop growing.

gives qualities of male and female.
bones: thyroid hormones
remodeling of bone
bones: growth hormones
encourages general growth
appositional growth
growth at the outer surface of a bone during endochondral ossification, resulting in an increase in the bone's THICKNESS, Compact bone thickens and strengthens long bone with layers of circumferential lamellae
Vitamin A
stimulates osteoblasts
Vitamin C
needed for collagen
Vitamin D3
cholecalciferol, In the presence of Sun; epidermal cells produce cholecalciferol (vit D3)...the liver and kidneys convert D3 into Calcitriol (important in bone & nerve conduction; and aids in absorption of calcium and phosphorus)
bone resorption
process of bone demineralization or the breaking down of bone into mineral components

osteoclasts secret
-lysosomal enzymes
-acids
calcium is needed
Needed for:
1. The process of bone formation
2. Coagulation of blood
3. Excitation of cardiac and skeletal muscle
4. Maintenance of muscle tone
5. Conduction of neuromuscular impulses
6. Synthesis and regualtion of the endocrine and exocrine glands
Control of Remodeling
controlled by Hormonal mechanisms that maintain calcium homeostasis in the blood, and Mechanical and gravitational forces
Rising blood Ca triggers
thyroid to release calcitonin stimulates calcium salts to be deposited in bone
calcitonin
reduces blood calcium level
Falling blood Ca triggers
parathyroid gland to release PTH, osteoclasts to degrade bone and release Ca into blood
PTH
Parathyroid hormone; secreted by the parathyroid gland; PTH regulates uptake of calcium (Ca) from the bones into the blood
Wolff's Law
A bone grows or remodels in response to forces or demands placed upon it
Wolff's law
Curved bones are thickest where they are most likely to buckle

Long bones are thickest midway along the shaft (bending stress is greater) + hollow or filled with far

Large bony projections occur where heavy, active muscles attach
Stages of Healing of a bone Fracture
hematoma formation (mass of clotted blood), fibrocartilaginous callus formation (soft tissue forms & phagocytic cells begin cleaning debris), bony callus formation (Osteoclasts remove dead cells & cartilage & osteoblasts secrete new matrix) Bone Remodeling
osteomalacia
abnormal softening of bones caused by deficiencies of phosphorus or calcium or vitamin D
rickets
childhood disease caused by deficiency of vitamin D and sunlight associated with impaired metabolism of calcium and phosphorus
osteoporosis
abnormal loss of bony tissue resulting in fragile porous bones attributable to a lack of calcium
paget's disease
a bone disease of unknown cause characterized by the excessive breakdown of bone tissue, followed by abnormal bone formation