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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
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
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
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
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