Skeletal System figure 6.2 _____________ cells- unspecialized stem cells

only bone cells to undergo cell division daughter cells become osteoblasts

__________________- bone building cells synthesize & secrete collagen fibers & other organic

components to build matrix Initiate calcification Become osteocytes= mature bone cells

____________- huge cells, fusion of monocytes digest protein and mineral of underlying bone

Resorption- normal develop, growth, maintanance & repair

Skeletal system figure 6.1

Supports soft tissues & attachment for muscle Protects internal organs Provides movement Stores & releases minerals Contains:

___________________ - produce blood cells ____________________- stores fat, few blood cells

Bone defined

________- matrix is abundant w/ inorganic mineral salts (50%), 25% water, 25% collagen Hydroxyappatite- main mineral salt

calcium phosphate and calcium carbonate __________________ - crystallization or

hardening of the matrix Is a connective tissue AKA – osseous tissue

Types of bones figure 7.2

________bones- greater length than width Shaft and extremities, curved for strength Femur, tibia, fibula, humerus, radius, ulna

_______ bones- somewhat cube shaped = length and width Carpals, tarsals

_____ bones- thin, composed of 2 parallel plates of compact bone (spongy inside) Sternum, ribs, scapula

Types of bones figure 7.2

_____________ bones- complex shapes Cannot be grouped into previous categories Varying amt of spongy and compact Vertebrae, some facial bones

________ bones- shape like sesame seed Develop in certain tendons where friction,

tension, & physical stress Palms, soles (usually few mm, except patella)

Haversian System fig 6.3

Haversian system __________ – units of _____________________

Haversian or central canal – longitudinal thru center of osteon contains b.v., lymphatic vessels & nerves

_______ –concentric rings of calcified matrix ___________ – small, hollow space in which

osteocytes lie ________ – small canals connecting lacunae

Haversian system = osteon

Osteocyte – mature cell, maintains daily activity _____________ – membrane lining marrow cavity

consists of osteogenic cells & scattered osteoclasts Perforating or Volkmann’s canal – small

passageway by which b.v. & nerves from periosteum penetrate into compact bone

________ – membrane covering bone, consists of CT, osteoprogenitor cells & osteoblasts essential for growth, repair, & nutrition

Compact bone tissue

Contains few spaces, arranged in osteons ____________________________

Bulk of diaphyses of long bones Provides protection and support Resists stresses produced by weight and

movement Osteons __________________ (such as long

axis of a bone) to resist bend or fracture

Spongy bone figure 6.3

Spongy bone does NOT contain osteons _____________ of thin columns= _________

microscopic spaces between filled w/ RB marrow Within each trabecula: osteocytes lie in

lacunae Canaliculi radiate from lacunae

Spongy bone (2)

Osteocytes receive nourishment directly from blood vessels in the medullary (marrow) cavity

Trabeculae are oriented along stress lines _____________________________

Spongy tends NOT to be located in heavily stressed areas

Long bone parts Figure 6.1

1. Diaphysis- bone shaft; long, cylinderal

2. Epiphyses- distal & proximal ends

3. Metaphyses- region of mature bone where 1 and 2 meet

*in growing bone contains: epiphyseal plate- layer of hyaline cartilage allowing the diaphysis to grow in length, not width

4. ______________- thin layer of hyaline cartilage covers epiphysis,reduce friction, shock absorbtion.

5. _____________- tough sheath of dense irregular CT surrounding bone surface where not covered by articular cartilage, grows in thickness not length; protects; nourishes; repairs; attach ligaments & tendons.

6. Medullary cavity= marrow cavity, space in diaphysis containing YBM

7. ______________- lines medullary cavity, osteogenic cells & osteoclasts

Bone marrow functions

Red bone marrow Produces RBC, WBC, platelets=________________ Consists of blood cells, adipocytes, fibroblasts,

macrophages Developing bones of fetus; pelvis, ribs, sternum,

vertebrae, skull, ends of some long Yellow bone marrow

________________ storage in fat cells Few blood cells With age much red turns to yellow

Types of ossification

Endochondral ossification- bone forms from cartilage

Intramembranous ossification- bone forms directly on or within CT, does not form from cartilage

Intramembranous ossification, 6.5

Intramembranous Ossification

Formation of bone directly on or within fibrous CT form directly from mesenchyme without going thru

cartilage stage fewer steps than endochondral:1. Mesenchymal cells condense & differentiate:

osteogenic cells __________________-center of ossification-Osteoblasts secrete organic matrix of bone until

completely surrounded by it

2. Matrix secretion stops. Osteoblasts become ________________. Calcium & mineral salts deposited, matrix hardens

3. Matrix develops into trabeculae, which fuse & form spongy bone

-BV grow into spaces between trabeculae & mesenchyme along surface

-CT assoc w/ b.v. in trabeculae differentiates into RB marrow

4. On outside, mesenchyme condenses & develops into _______________

-most layers of superficial spongy bone replaced by compact bone

-remains spongy at center

-much of this bone remodeled (destroyed & reformed) transform into adult size & shape

Endochondral ossification

_________________________ by bone most bones are formed this way

1. Development of cartilage:-mesenchymal cells crowd together in the shape of

future bone & differentiate into chondroblasts -Chondroblasts produce a hyaline cartilage matrix,- Perichondrium is around outside cartilage

2. Growth of cartilage: -chondroblasts buried in matrix become chondrocytes

-cartilage grows in _________ by cell division & secretion of matrix = ______ growth – “from within”

-Growth in __________by addition of matrix on periphery by chondroblasts in perichondrium = ___________ growth

-Chondrocytes increase in size, may burst release contents pH

*Change in pH causes calcification, other chondrocytes will die: essential materials cannot diffuse thru new matrix

3. Nutrient artery penetrates perichondrium & calcifying cartilage, stimulating osteogenic cells to differentiate into osteoblasts-Under perichondrium- thin shell of compact bone secreted= periosteal bone collar-periochondrium is developing bone = periosteum

__________ ossification center = region where bone will replace most cartilage _________ from external surface -Osteoblast secrete bone matrix-Trabeculae form-Osteoclast breakdown trabeculae leaving medullary cavity

4. _____________ oss center forms - b.v. enter epiphyses, @ birth. Spongy bone remains at center of epiphyses- no medullary cavities & ossif proceeds _________

5. Hyaline cartilage covering epiphyses becomes ________________

-Prior to adulthood: hyaline cartilage between epiphysis & diaphysis = epiphyseal plate- responsible for lengthwise growth

Endochondral ossification

Lengthening of bone fig 6.7

Epiphyseal plate is a layer of hyaline in the metaphysis of growing bone = 4 zones:

1. _________cartilage -layer nearest epiphysis, small scattered chondocytes

-no function in bone growth, anchor epiphyseal plate to bone of epiphysis

2. ____________ cartilage - slightly larger chondrocytes

-zone arranged like stack of coins, chondrocytes divide, replacing dying ones at diaphyseal side

3. ____________ cartilage - chondrocytes larger & remain arranged in columns

-lengthening of diaphysis = result of cell division and maturation here

4. __________ cartilage- final zone, few cells, thick

-mostly dead chondrocytes: calcified matrix

-Calcified cartilage dissolved by osteoclasts & invaded by osteoblasts & capillaries

-Osteoblasts lay down bone matrix, diaphyseal border of epiphyseal plate firmly cemented to diaphysis

*between the ages of 18-25 the epiphyseal plates close, plate fades, leaving a line

Zones- lengthening

Thickness (appositional) fig 6.8

At surface periosteal cells differentiate into osteoblasts- secrete collagen fibers & other molecules to form matrix Surrounded with matrix they become osteocytes Bone ridges form on sides of periosteal b.v. and

enlarge to leave groove for b.v. Ridges fuse, form tunnel

Periosteum now endosteum in tunnel

Thickness (appositional) fig 6.8

Osteoblasts in endosteum deposit matrix forming new lamellae Proceeds inward toward b.v. filling in tunnel

Osteon is formed Osteoblasts deposited a new lamellae thick

Appositional growth, fig 6.8

Remodeling of bone

Bone is continually renewed Osteoclasts carve out tunnels in old bone Osteoblasts rebuild new In different parts of skeleton full cycle= 2-3 months or

much longer Remodeling purposes:

Renew ________________ Redistribute matrix along lines of mechanical stress

Remodeling is the way injured bone heals.

Remodeling of bone Bone reabsorption= breakdown of matrix by

osteoclasts Attach to endosteum or periosteum Form leak proof seal (ruffled border) Release protein digestion lysosomal enzymes (digest

collagen) and acids (dissolve minerals) into pocket Proteins and minerals: mainly Ca2+ and P are

endocytosed, then exocytosis from other side Vesicle of proteins and minerals absorbed into blood

Osteoblasts move in Bone building must = bone reabsorption

Nutrients for bone

Calcium and phosphorus while growing And lesser amt of fluoride, magnesium, iron &

manganese Vitamin C for collagen synthesis &

differentiation of osteoblastsosteocytes Vitamin K and B12 for protein synthesis Vitamin A stimulates osteoblast activity

Sex hormones and bone At puberty: estrogens and androgens cause an

osteoblast activity & matrix synthesis Cause growth spurt ___________________ widening of pelvis Shut down epiphyseal growth plate in both sexes

Females close earlier because estrogen levels than men Those lacking estrogen or its receptor grow taller before closure

During adulthood: sex hormones- slow reabsorption of old & deposition of new Estrogens promote osteoclast apoptosis BUT, post-menopause, no estrogen, osteoblasts not

stimulated osteoporosis

Growth hormone and bone

_____ = insulin like growth factor: most imp in stimulation bone growth as children Produced by bone tissue and liver Promote cell division at epiphyseal plate & periosteum Enhance protein synthesis need for new bone Production stim. by human growth hormone (hGH)

Oversecretion of hGH in childhood= __________ Undersecretion of hGH = _____________

Parathyroid hormone (PTH)

Most imp hormone in regulation Ca2+ exchange between ____________________

From parathyroid glands Secretion via negative feedback

If Ca2+ in blood , parathyroid receptors detect & cause cAMP, detected PTH

PTH cause osteoclast activity Ca2+ reabsorbed into blood

PTH works on kidneys to loss of Ca2+ to urine Stimulates calcitrol to Ca2+ absorbtion from GI tract

Calcitonin (CT)

Secreted by parafollicular cells of parathyroid when __________________

Inhibits activity of osteoclasts uptake of blood Ca2+ by bone Accelerates Ca2+ deposition in bone Promotes bone formation & blood Ca2+ Harvested from salmon for osteoporosis

Bone fracture types fig 6.9

Open (compound) = broken ends protrude thru skin

Closed (simple) = do not break skin Comminuted “together crumbled” = bone splinters

at site of impact Fragments between 2 larger pieces

Greenstick = partial fracture, one side of bone is broken & other side bends Only in children- not fully ossified

Impacted = one end of fractured bone forcibly driven into interior of another

Pott’s = fracture at distal end of fibula with serious injury at distal tibial articulation

Colle’s = fracture of distal end of radius & distal fragment displaced posteriorly

Bone fracture repair fig 6.10

1. Formation of __________________ –-B.V. crossing the fracture are broken

-Clot forms in 6-8 hrs

-circulation in that areas stopsosteocytes die

swelling and inflammation

-capillaries grow into clot, macrophages & osteoclasts remove dead & damaged tissue

-may take several weeks

2. _________________ _________ forms – -new capillaries organize growing CT=

procallus

-fibroblasts & osteogenic cells invade procallus

produce collagen to connect broken ends

osteogenic cells chondroblasts secrete fibrocartilage

-phagocytes removing debris

-this stage = 3 weeks

3. __________________ formation- in well vascularized areas closer to healthy bone tissue.osteogenic cells osteoblasts produce trabeculaeFibrocartilagespongy bone- this stage = 3-4 months

4. ____________________- dead portions of old fragments reabsorbed by osteoclasts -Compact bone replaces spongy healed area may now be thicker, stronger

Diseases

____________- condition of porous bones Bone reabsorption outpaces bone deposition,

largely due to depletion of calcium in the body (lost in urine, feces, and sweat rather than absorbed from the diet).

Bone mass becomes so depleted that bones often fracture

causes shrinkage of vertebraeheight loss hunched back and bone pain

Rickets and Osteomalacia- bones fail to calcify, organic matrix is produced but calcium salts are not deposited bones soft, rubbery and easily deformed ___________- in children- forming bone; _______________- in adults- new bone

formed during remodeling fails to calcify. Pain, tenderness, possible fracture from

minor trauma.

________________- infection of bone Characterized by high fever, sweating, chills,

pain, and nausea Pus formation, edema, and warmth over

affected bone and overlying muscle Bacteria reach bone thru

Open fracture penetrating wounds orthopedic procedures Other sites of infection

Medical terms/disorders

Kyphosis- “lump” “condition” Exaggeration of the thoracic curve of vertebral column In elderly can be caused by degeneration of

intervertebral discs Other causes= ricket, poor posture, female advanced

osteoporosis, tuberculosis of the spine Lordosis – “bent backwards” AKA swayback

Exaggeration of lumbar curve Causes: wgt of abdomen– pregnancy or obesity,

poor posture, rickets, tuberculosis of the spine

Medical terms/disorders

Scoliosis- “crooked,” lateral bending of vertebral column (usually thoracic) Causes: congenitally malformed vertebrae, chronic

sciatica, paralysis of muscles on one side of vertebral column, poor posture, one leg shorter than other.

Herniated (slipped) disc- ligaments holding intervertebral disc are injured or weakened causing the nucleus pulposus (inner portion) to herniate (protrude). Usually in lumbar region- wgt bearing Slip towards spinal cord or spinal nerves pain

_________skeleton- bones arranged along axis of the skeleton 80 bones Skull, hyoid, auditory ossicles, vertebral column, thorax

______________ skeleton- bones of upper & lower limbs, & girdles connecting the limbs to the axial. 126 bones Pelvic girdle- connect legs to axial skeleton Pectoral girdle- connect arms to axial