U2 Lecture 2 Flashcards
- list the components of the matrix of bone and describe how each component contributes to the bone's strength - Describe the differences between compact and spongy bone in terms of location, function, and composition - describe the microscopic structure of compact bone (the osteon) and understand the purpose of its organization
Bones are made of what type of tissue?
Connective tissue
What makes up connective tissue?
extracellular matrix and cells
What makes up extracellular matrix?
Ground substance and fibers
What makes up ground substances?
Organic ( ex: non-collagenous proteins) and inorganic components
Where are the organic components of bone extracellular matrix from?
osteoblasts
What is the ground substance of organic components in ECM
- Glycosaminoglycans (GAGs)
- Glycoproteins = polysaccharide + protein (chondroitin sulfate, hyaluronic acid)
- negatively charged (they trap water)
What type of collagen fibers are found in the organic components of ECM
Type 1 Collagen
Define type 1 collagen
- fibrous protein arranged in helical form
- very resistant to pulling forces
- provides flexibility and a framework for deposition of calcium crystals
Hierarchial organization of collagen in bone
osteoblasts -> tropocollagen -> microfibril -> fibril -> fiber -> lamella -> osteon -> compact bone -> bone
What are the types of inorganic components in ECM
Water and hydroxyapatite crystals
What is hydroxyapatite?
Calcium phosphate and calcium hydroxide, other minerals (calcium carbonate) and some ions (Mg2+, F-, and K+)
- salt
Describe the formation of hydroxyapatite crystals in bone ECM
- salts (hydroxyapatite) are deposited within collagen fibers
- As the hydroxyapatite condenses, other inorganic salts and ions precipitate in the matrix to fill in the spaces between fibers
Organizations of minerals in bone ECM
- small mineral plates bound by helical noncollagenous proteins (collagen cross links) form mineralized fibrils
- many mineralized fibrils bound by collagen cross links form osseous tissue fiber (collagen fiber)
Functions of collagen for bone ECM
Provides flexibility and resistance to tension
Functions of minerals for bone ECM
Provides firmness (resistance to compression)
What happens when you soak bones in weak acid (vinegar)?
Removes minerals from bone -> bone becomes rubbery
What happens when you apply denature protein to bone?
removes collagen from bone -> bone becomes brittle/crumbly
Skeletal disorders
- rickets: inorganic component deficient (calcium deficient due to lack of vit. D leads to flexible bones)
- Scurvy: organic component deficient (problem with collagen synthesis due to vit. C deficiency leads to brittle bones)
Spongy bone vs. Compact bone
- same chemical composition
- different 3D organization
Organization of spongy bone
- irregular lattice of thin plates called trabeculae
- trabeculae made of osteocytes, lacuna, lamellae, canaliculi, osteoblasts, and osteoclasts (housed in lacunae)
Locations of spongy bone
- epiphyses of long bone (on each end of the bone which is the part that grows)
- surrounding marrow cavities
- flat, short, irregular bones
Functions of spongy bone
- withstands forces from many directions: trabeculae arranged along lines of stress
- lightens the skeleton (not as strong as compact bone)
- contains red marrow for hemopoiesis
Compression and Tension
compression is opposite of tension
Organization of compact bone
- solid network of bone organized in rings called osteons
- compact bone made of lacuna, central canal, interstitial lamellae, canaliculus, osteocytes, and blood vessels
What is lacuna?
The space in compact bone which the osteocytes are found
What is compact bone’s primary weakness?
Twisting forces
