KIN CH 6 BONE

Skeletal system function 1

Support and attachment for tendons and ligaments

Skeletal system function 2

Protects internal organs

Skeletal system function 3

Assists movement with muscles

Skeletal system function 4

Stores and releases calcium and phosphorus

Mineral homeostasis

Bone storing and releasing calcium and phosphorus

Skeletal system function 5

Blood cell production

Hemopoiesis

Blood cell production in red marrow

Skeletal system function 6

Stores triglycerides in yellow marrow

Diaphysis

Shaft of a long bone

Epiphysis

Proximal or distal end of a long bone

Metaphysis

Region between diaphysis and epiphysis

Articular cartilage

Hyaline cartilage covering epiphysis for joint protection

Periosteum

Connective tissue sheath around the bone

Periosteum layers

Outer dense irregular tissue and inner osteoprogenitor layer

Periosteum function

Fracture repair and tendon ligament attachment

Sharpey's fibers

Attach periosteum to bone

Medullary cavity

Hollow diaphysis space holding yellow marrow in adults

Endosteum

Membrane lining the medullary cavity with bone stem cells

Skeletal system tissues

Bone cartilage dense connective adipose nervous

Major skeletal tissues

Bone and cartilage

Bone as dynamic tissue

Constantly remodeling throughout life

Bone matrix composition

15% water 30% organic protein 55% mineral salts

Collagen in bone

Gives flexibility and tensile strength

Hydroxyapatite

Calcium salt crystals making bone hard

Bone mineral salts

Calcium phosphate calcium carbonate and trace elements

Bone trace elements

Magnesium fluoride sulfate

Calcification

Mineral deposition giving bone its properties

Osteoprogenitor cell

Bone stem cell that divides and differentiates

Osteoprogenitor location

Inner periosteum and endosteum

Osteoblast

Bone building cell

Osteoblast function

Secretes collagen and matrix by deposition

Osteocyte

Mature bone cell for daily metabolism

Osteocyte function

Exchanges nutrients and wastes and maintains tissue

Osteoclast

Large bone resorbing cell

Osteoclast origin

Fusion of many white blood cells

Osteoclast function

Releases enzymes digesting matrix by resorption

Osteoclast and calcium

Releases bone calcium to regulate blood levels

Only dividing bone cell

Osteoprogenitor cell

Osteoblast to osteocyte

Osteoblast trapped in its own matrix

Compact bone

Dense strong bone for protection and support

Compact bone location

Diaphysis and outer layer of all bones

Spongy bone

Lightweight lattice bone supporting tissue

Spongy bone location

Epiphyses and interior of long bones

Osteon

Functional unit of compact bone

Haversian system

Another name for osteon

Concentric lamellae

Rings of calcified matrix around central canal

Osteon orientation

Parallel to long axis along stress lines

Interstitial lamellae

Fragments of old osteons between osteons

Lacuna

Small space housing an osteocyte

Canaliculi

Fluid filled channels linking lacunae

Osteocyte communication

Gap junctions via canaliculi processes

External circumferential lamellae

Rings under the periosteum

Internal circumferential lamellae

Rings around the medullary cavity

Perforating fibers

Connect external circumferential lamellae

Central canal

Osteon channel carrying vessels and nerves

Perforating canal

Volkmann's canal carrying vessels to outer cortex

Volkmann's canal

Perforating canal linking periosteal vessels

Trabeculae

Irregular thin columns forming spongy bone

Trabeculae orientation

Along lines of stress

Trabeculae function

Reduce weight and house red marrow

Spongy bone osteons

Absent

Compact vs spongy bone

Dense with osteons vs lattice of trabeculae

Spongy bone osteocytes

Lacunae nourished by blood in trabeculae

Bone blood supply

Richly vascularized

Periosteal arteries

Enter diaphysis through perforating canals with nerves

Nutrient artery

Enters diaphysis through nutrient foramen

Nutrient foramen

Opening where the nutrient artery enters

Nutrient canal

Passage to the medullary cavity

Nutrient veins

Exit through the same canal

Epiphyseal and metaphyseal vessels

Ends have their own arteries and veins

Ossification

Process of bone formation also called osteogenesis

Ossification situations

Development growth remodeling and fracture repair

Ossification start

About week 6 of embryonic development

Ossification types

Intramembranous and endochondral

Intramembranous ossification

Bone forms directly in mesenchyme with no cartilage

Intramembranous locations

Flat bones skull mandible clavicle

Intramembranous vs endochondral

Direct bone formation vs cartilage model replacement

Intramembranous step 1

Mesenchymal cells cluster and become osteoblasts

Intramembranous step 2

Osteoblasts become osteocytes and matrix calcifies

Intramembranous step 3

Trabeculae fuse into spongy bone around vessels

Intramembranous step 4

Periosteum forms and compact bone covers spongy bone

Endochondral ossification

Hyaline cartilage model replaced by bone

Endochondral locations

Most bones especially long bones

Endochondral growth centers

One primary and two secondary

Endochondral step 1

Mesenchyme forms hyaline cartilage model with perichondrium

Endochondral step 2

Model grows and central cartilage calcifies

Calcified cartilage result

Chondrocytes die leaving spaces

Interstitial growth

Lengthening by chondrocyte division inside cartilage

Appositional growth

Thickening by new matrix on the surface

Endochondral step 3

Nutrient artery triggers primary ossification center

Primary ossification center

Site where bone first replaces cartilage

Endochondral step 4

Osteoclasts hollow out the medullary cavity

Endochondral step 5

Epiphyseal arteries trigger secondary ossification centers

Secondary ossification

Spongy bone stays in epiphysis with no cavity

Endochondral step 6

Epiphyseal cartilage becomes articular cartilage and growth plate

Epiphyseal growth plate

Hyaline cartilage between epiphysis and diaphysis

Growth plate function

Lengthwise bone growth until adulthood

Growth in length event 1

Interstitial cartilage growth on epiphyseal side

Growth in length event 2

Replacement by bone on diaphyseal side

Epiphyseal plate zones

Resting proliferating hypertrophic calcified