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compact bone

dense outer layer

spongy bone

internal to compact bone
network (trabeculae)


the irregular latticework of thin bony plates in spongy bone tissue
red or yellow marrow

medullary cavity contains..



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.


shaft of a long bone
compact bone
surrounds medullary cavity


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).


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


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


Mature cells, develop from osteoblasts, control day-to-day activities (each occupies a lacuna, a pocket sandwiched between layers of matrix


small spaces between the lamellae which contain osteocytes


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


bone forming cells - perimeter of bone


maintain bone - inside bone


large cells that resorb or break down bone matrix, releasing calcium ions into the blood - perimeter of bone


Unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen


mineral salts; calcium phosphate & Salts

Without minerals bone...

is flexible

without collagen bone


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

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


reduces blood calcium level

Falling blood Ca triggers

parathyroid gland to release PTH, osteoclasts to degrade bone and release Ca into blood


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


abnormal softening of bones caused by deficiencies of phosphorus or calcium or vitamin D


childhood disease caused by deficiency of vitamin D and sunlight associated with impaired metabolism of calcium and phosphorus


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

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