BSC 2085 LESSON 8

BONE TISSUE

composed of bones, cartilages, and ligaments joined to form a framework for the body

Skeletal system

study of bone. 

osteology

•is the forerunner of most bones and covers many joint surfaces

cartilage

hold bones together at joints

ligaments

attach muscle to bone

tendons

support

protection

movement

electrolyte and acid-base balance

blood formation

hormone secretion

Roles of the skeleton

•limb bones and vertebrae support body; jaw bones support teeth; some bones support viscera

support of skeleton

•moderates calcium and phosphate levels and buffers blood against large pH changes by altering phosphate and carbonate salt levels

Electrolyte and acid-base balance of skeleton

connective tissue with the matrix hardened by calcium phosphate and other minerals

bone 

the hardening process of bone

calcification/mineralization

Individual bones (each bone is an organ) consist of

bone tissue

bone marrow

cartilage

adipose tissue

nervous tissue

fibrous connective tissue

•The word “BLANK” can refer to the organ or just the osseous tissue

bone

•Ex: parietal bones of skull, sternum, scapula, ribs, coxal “hip” bones

flat bones

•Ex: humerus, radius, ulna, femur, tibia, fibula, metacarpals, metatarsals, phalanges

long bones

bones of wrist and ankle

short bones

vertebrae, coxal, and some skull bones

irregular bones

longer than wide; rigid levers acted upon by muscles; crucial for movement

long bones

thin, curved plates; protect soft organs

flat bones

approximately equal in length and width

short bones

elaborate shapes

irregular bones

•These indicate where blood vessels and nerves run along the side of the bone or enter bone

•Depressions, grooves, tunnels

These indicate where tendons and ligaments attach onto bone or where articulations (joints) occur with other bones

Elevations or projections

•Skeleton is BLANK/BLANK compact and BLANK/BLANK spongy bone by weight

3/4; 1/4

epiphyseal plate is composed of 

cartilage

layer of hyaline cartilage that covers joint surface of the epiphysis; allows joint to move more freely

articular cartilage

BLANK fibrous layer of collagen and BLANK osteogenic layer of bone-forming cells (periosteum)

Outer; inner

•functions to isolate bone, provide route for blood vessels and nerves, and participates in bone growth/repair

periosteum 

thin layer of reticular connective tissue lining marrow cavity and all internal bone surfaces. 

Endosteum

•Is an incomplete cellular layer (not a continuous sheet)

endosteum

•Covers the trabeculae of spongy bone

endosteum

•Lines the central canals of osteons

endosteum

•Contains osteogenic cells, osteoblasts, and osteoclasts

endosteum

•Active in bone growth/repair

endosteum

sandwich like structure of flat bone in cranium

diploë

Four types of bone cells

osteogenic cells

osteoblasts

osteocytes

osteoclasts

mesenchymal stem cells found in the endosteum and inner layer of periosteum

Osteogenic/osteoprogenitor cells

bone-forming cells in endosteum and inner layer of periosteum

osteoblasts

former osteoblasts that have become trapped in the matrix they deposited

osteocytes

bone-dissolving cells found on bone surface

osteoclasts

Perform osteolysis/resorption

Do not develop from osteogenic cells

Very large cells formed from fusion of several stem cells

osteoclasts

the breakdown of bone, as part of bone remodeling

osteolysis/resorption

Important in releasing calcium and phosphate into body fluid, blood.

osteolysis/resorption

develop from the same bone marrow stem cells that give rise to macrophages (different origin from other bone cells

osteoclasts

have multiple (usually 3-4, but can be up to 50) nuclei in each cell

osteoclasts

•tiny cavities where osteocytes reside

lacunae

little channels that connect nearby lacunae

canaliculi

Arise from embryonic mesenchyme; they continuously multiply and give rise to osteoblasts

osteogenic cells

synthesize soft organic matter of bone matrix and promote its mineralization

osteogenesis

Perform osteogenesis

rapidly multiply and increase the number of osteoblasts which reinforce bone

osteoblasts

BLANK stimulates osteogenic cells to rapidly multiply and increase the number of osteoblasts which reinforce bone.  This will use calcium and phosphate from blood, BLANK their ion concentration in blood.

Stress

Reducing

Act as strain sensors

Maintains protein and mineral composition of the matrix

plays a role in the repair of damaged bone

osteocytes

when stressed, produce biochemical signals that regulate bone remodeling (shape and density changes that are adaptive)

osteocytes

•Osteoblasts and osteocytes secrete hormone BLANK

osteocalcin

Part of body’s acute stress response, stimulates pancreatic secretion of insulin, increases insulin sensitivity, promotes energy availability

Osteocalcin

Collagen and carbohydrate–protein complexes, such as glycosaminoglycans, proteoglycans, and glycoproteins

Organic matter

•1/3 of matrix, synthesized by osteoblasts

organic matter

•2/3 of matrix, mineral component

inorganic matter

•85% hydroxyapatite [(Ca₁₀(PO₄)₆(OH)₂], a crystallized calcium phosphate salt

•10% calcium carbonate, CaCO₃

•Many inorganic ions, magnesium, fluoride, sodium

inorganic matter

•Combination forms a composite material that provides BLANK (organic matter) and BLANK (inorganic matter)

flexibility

strength

disease caused by mineral deficiency and resulting in soft, deformed bones – not enough calcium from diet (could be caused by not enough UV light exposure which is needed to produce vitamin D₃ which is needed to absorb calcium from your diet

rickets

•Collagen molecules contain BLANK that break under stress and dissipate shock under load

sacrificial bonds

results from a defect in collagen deposition

brittle bone disease

Osteogenesis imperfecta

layers of matrix surrounding a central (Haversian) canal that runs longitudinally along the length of the bone

Concentric lamellae

A central canal and its lamellae constitute

osteon (Haversian system)

central canals connected to each other by transverse

perforating/Volkmann’s canals

•Collagen corkscrews down each lamella; helical arrangement in one lamella is BLANK of adjacent lamella, enhancing strength

opposite 

•Osteons separated from other osteons by a BLANK, which prevents spread of microfractures to other osteons

thin cement line

found encircling inner outer region of dense bone

Circumferential lamellae

fill irregular regions between osteons

Interstitial lamellae

Lattice of bone slivers (spicules) and plates (trabeculae) covered with endosteum, canaliculi of lacunae opens onto the surface of the trabeculae

spongy bone anatomy

tissue that produces blood cells

hematopoietic tissue

Red bone marrow

myeloid tissue

Contains multiple tissues

•Found in nearly every bone in a child

•In adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur

red bone marrow

Contains adipose tissue

does not normally produce blood but can transform back to red bone marrow in severe/chronic anemia in adults

found in adults

yellow bone marrow

bone building (osteoblasts) and recycling/breakdown (osteoclasts) must be balanced

Homeostasis