MSK Physiology: Bones

support, muscles, organs, formation, mineral

Roles of the Bones

-Form the body

-________ tissue

-Permit movement by providing attachment points for _________

-Protect vital ________

-Site of blood cell ___________

-Role in _______ homeostasis

chondrocytes, cartilage, osteoblasts, long, most

Bone Formation: Endochondral Ossification

-Begins during embryonic development, much more common than intramembranous ossification

-Mesenchymal stem cells (MSC) → ____________ → develops mineralized ________ scaffold → forms __________ → forms ____ bones and ____ other bone elements

pre, cartilage, skull, flat

Bone Formation: Intramembranous Ossification

-Skip the cartilage formation stage and go straight to building bones

-MSC → ___osteoblasts → osteoblasts without ________ framework → forms _____ and ____ bones

matrix, calcification

Bone Formation

-First Step → develop bone _______ (collagen/fiber formation)

-Final Step → ____________ or mineralization

flexible, osteocytes, new, collagen, diffusion, calcium

Elements of Bone: Rigid Yet _________ Connective Tissue

-Cells

• Osteoblasts, ___________, and osteoclasts

• Help with bone growth, bone repair, to change shape, make ___ bone, and resorb old tissue

-Fibers

• __________

• Gives tensile strength and ability to hold itself together

-Ground Substance

• Gelatinous material (proteoglycans/hyaluronic acid)

• Medium for _________ between bone and blood vessels

-Crystalized Materials

• Mostly _________

• Provides rigidity

forming, mesenchymal, calcium, osteoid, outer, PTH, osteocalcin, inorganic

Bone Cells: Osteoblasts

-Responsible for bone __________

-Derived from ____________ stem cells (MSC)

-Form new bone → deposition of _________ and synthesis of ________ (nonmineralized bone matrix)

-Found on the _______ layer of bone and respond to ___ → produce __________ in response to Vitamin D → produce _________ calcium phosphate

-Differentiate into osteocytes imbedded in bone

maintaining, lacuna, mechanical, stress, PTH, form, resorb

Bone Cells: Osteocytes

-Bone ___________

-Located in the _______, which are depressions found in the bone. They develop dendritic processes that extend to either bone surface or bone’s vascular space.

-Can detect ___________ force and respond to changes in ______, also responds to ___

-Signals osteoblasts and osteoclasts to _____ and ______ bone

hematopoietic, Howship, hydrochloric, dissolve, degenerates

Bone Cells: Osteoclasts

-Large, multinucleated cells that resorb bone

-Derived from _____________ stem cells located in ________/resorption lacunae, which are scalloped cavities in the bone.

-Secrete ____________ acid, acid proteases, and matrix metalloproteinases → _________ bone minerals and collagen

-Once resportion is complete → __________ or becomes inactive

osteoblast, osteoclast, loss, cytokines

OPG/RANKL/RANK System

-Helps regulate ________ and _________ activity/function, which is essential for homeostasis

-Balance between RANKL and OPG determines amount of bone ____

-Regulated by different __________ and hormones, which are balanced under normal circumstances

glycoprotein, inhibits, resportion, formation

OPG (Osteoprotegerin)

-____________ (TNF family) from osteoblasts and osteocytes

-_______ osteoclast formation → inhibits bone ___________ → promotes bone _________

-Binds to RANK, which is a receptor on osteoclast precursor cells

cytokine, T, osteoclasts

RANKL

-_________ from osteoblasts and _ cells

-Formation and activation of __________ → increases bone loss

-Binds to RANK

injuries, remodeling, apoptosis, osteoclast, digest, osteoid, calcium

Bone Remodeling: Repair Microscopic ________ and Maintenance of Bone Integrity

Phases

-Activation of __________ cycle

• Osteocyte cell death (_________) → signals _________ activity. Injured or old tissue needs to be resorbed somewhere.

-Resorption of bone

• Osteoclasts attach to bone and release lysosomal enzymes to ______ bone

-Formation of new bone

• Osteoblasts form _______ and alkaline phosphate → sites for _______ and phosphorous deposition

• Takes 4-6 months

osteoid, I, calcium, phosphate

Bone Matrix: Composition

-35% organic → _______

• Mostly type _ collagen

• Small amounts of glycosaminoglycans and other proteins

-65% inorganic → _________ and _____________ minerals

-5-8% water

-Proteoglycans

-Glycoproteins

osteoblasts, fibrils, twist, strength

Bone Matrix: Collagen Fibers

-Make up the bulk of bone matrix

-Synthesized and secreted by ___________ → form ______ → fibrils form staggered pattern creating gaps for mineral deposition → fibrils ______ to form ropelike fibers → gives bone tensile and support _________

-Over 20 types → all with a specific function

ground, compression, collagen, strengthen, transport, deposition

Proteoglycans

-Make up some of _______ substance

-Forms ____________ resistant network between ________ fibrils → helps ___________ bone

-Controls particle __________ (mostly calcium) through bone matrix

-Role in bone calcium ___________ and calcification

calcification, inhibits, resorption, binds, stabilizes, osmotic

Glycoproteins

-Sialoprotein

• Promotes __________, a calcium binding protein

-Osteocalcin

• _______ calcium phosphate precipitation

• Promotes bone __________

-Osteonectin

• _____ calcium in bone

-Laminin

• __________ bone basement membrane

-Albumin

• Transports essential elements to bone cells

• Maintains ______ pressure of bone fluid

formation, osteoblast, proliferation, collagen

Bone Minerals: Mineralization

-Final step in bone ___________

-Phases:

• Formation of hydroxyapatite crystals

  • Buds from chondrocyte, ___________, and odontoblast surface

• ___________ of hydroxyapatite into extracellular matrix and deposition between _________ fibrils

solid, Haversian, osteocytes, lack, red, trabeculae

Types of Bone Tissue

-Compact (Cortical) Bone

• 85% of skeleton

• ______ and extremely strong

• ________ system (basic structural unit) → Haversian canal, lamellae, lacunae, ___________, and canaliculi

-Spongy (Cancellous) Bone

• 15% of skeleton

• ____ Haversian system, less organized

• Filled with ___ bone marrow

• __________: plates or bars

blood, nerve, transports, osteocytes, lamellae, lacunae, canaliculi, connect, transport

Haversian System

-Central Canal (haversian canal)

• Contains ______ vessels and _____ fibers

• ________ nutrients and wastes to and from ___________

-Concentric layers of bone (________), which surround the canal

-Tiny spaces between lamellae (_______), where the osteocytes sit

-Small channels or canals (_________)

• _______ lacunae to each other and to the haversian canal

• _________ nutrients and molecular signals to lacunae

Axial, appendicular

List #1 and #2 in order

long, flat, short, irregular

Characteristics of Bone

-____ → diaphysis, metaphysis, epiphysis, epiphyseal plate (children). Examples of femur and humerus

-____ → examples of ribs and scapula

-______ (cuboidal) → example of bones of the wrist or ankle

-_________ → example of vertebrae, mandible, and facial bones

anchored, vessels, growth, diaphysis, yellow, spongy, red, spongy, red

Characteristics of Bone

-Periosteum

• Connective tissue _________ to bone

• Contains _______ and nerves

• Aids in bone _______ and healing

-Endosteum

• Connective tissue lining surface of both marrow cavities

-__________ (shaft)

• Mostly compact bone

• Medullary cavity containing fatty tissue: _______ marrow

-Metaphysis (neck)

• Mostly _______ bone containing ___ marrow

-Epiphysis

• Mostly _______ bone containing ___ marrow

Epiphysis

#1

Endosteum

#2

Diaphysis

#3

Periosteum

#4

hematoma, procallus, granulation, callus, calcium, lamellar, trabecular, periosteal, remodeled, before

Bone Repair

-________ formation (within hours)

• Clot forms → vessels break/tear, fibrin and platelets form framework

-_________ formation (within days)

• Produces __________ tissue

-_____ formation (within weeks)

• Forms membranous or woven bone → enzymes allow phosphate to join with ________ to harden the callus

-Replacement (within years)

• Callus replaced with ________ bone or ________ bone

-Remodeling (within years)

• __________ and endosteal surfaces of bone __________ to the size and shape of the bone _______ injury