Chapter 6 Bones And Skeletal Tissue

Front 1

Human skeleton

Back 1

-Initially just cartilage, replaced by bone, except areas of flexibility.

-Skeletal Cartilage- resilient, molded cartilage tissue, primarily made of water. No blood vessels /nerves

Front 2

Perichondrium

Back 2

-Dense Irregular C.T around cartilage, like girdle

-resists outward expansion

- blood vessels nourish cartilage

Front 3

Bone tissue components

(Cartilage)

Back 3

-All bones have the same basic components.

-Cartilage made of chondrocytes, cells encased in small cavities -> lacunae, within extracellular matrix

3 Types: Hyaline, Elastic & Fibrocartilage

Front 4

Hyaline

Back 4

- support/flexibility

- Most abundant type; contains collagen fibers only.

- joints, ribs, larynx, nose tip

Front 5

Elastic

Back 5

-Flexibility

- contains elastic fibers

-External ear, Epiglottis

Front 6

Fibrocartilage

Back 6

-compressible, high tensile strength

-Intermediate between hyaline & elastic

-rows of chondrocytes alternating w/ thick collagen fiber

-Menisci of knee, intervertebral disc

Front 7

Growth of Cartilage

1. Appositional Growth

Back 7

-Growth from outside

-Cartilage forming cells in perichondrium secrete matrix onto external face of existing cartilage

Front 8

2. Interstitial Growth

Back 8

-Growth from inside

-Chondrocytes within lacunae divide and secrete new matrix, expanding from within

Front 9

Calcification of cartilage

Back 9

-Occurs in normal youth bone growth, also old age.

-Hardened cartilage is not the same as bone

Front 10

Functions of Bones

Back 10

-Support & Protection

-Movement

-Mineral & Triglyceride (fat) storage

-Blood Cell & Hormone production

Front 11

Axial & Appendicular

Back 11

Axial- Skull & Torso bones

Appendicular- Limb bones & girdles

Front 12

Long Bones

Back 12

-Longer than wide, shaft & 2 ends

(Limb Bones)

Front 13

Short Bones

Back 13

-Cube shaped bones

(Wrist & Ankle)

Front 14

Sesamoid Bones

Back 14

-Form within tendons, shaped like seeds (vary in size & #)

-Patella (Largest sesamoid bone)

Front 15

Flat Bones

Back 15

-Thin, flattened, usually curved

(sternum, scapula, ribs, most skull bones)

Front 16

Irregular Bones

Back 16

-Complicated shapes (don't fit other classes)

-Vertebrae & Hips

Front 17

Bones are Organs

Back 17

-Mostly osseous tissue, also has nervous tissue, cartilage, fibrous C.T, muscle cells & epithelial cells in blood vessels

3 Levels of Bone Structure: Gross, Microscopic & Chemical

Front 18

Gross Anatomy

-Compact Bone

Back 18

Looks solid, but riddled w/ passageways for nerves, blood vessels & lymphatic vessels

Front 19

-Spongy Bone (Trabecular bone)

Back 19

honeycomb of small, needle-like pieces of bone called Trabeculae

(open spaces filled with red/yellow marrow)

Front 20

Structure of short, irregular and flat bones

Back 20

-Thin spongy bone plates (diploe) covered by compact bone

-Compact bone covered w/ CT membranes

-Bone marrow throughout spongy bone

-Hyaline cartilage covers bone of movable joint

Front 21

Endosteum

Back 21

Endosteum: Covers inside of compact bone

Front 22

Structure of Typical Long Bone

Back 22

Long Bones: shaft (diaphysis), bone ends (epiphyses), and membranes.

Front 23

Diaphysis

Back 23

Tubular shaft forms long axis of bone

Compact bone surrounds Medullary Cavity

(filled with yellow marrow-adults)

Front 24

Epiphyses

Back 24

End of long bones -> compact bone outside, spongy bone inside

-articular cartilage covers joint surface

Front 25

Epiphyseal Line

Back 25

Between Diaphysis and Epiphyses

-Remnant of childhood Epiphyseal Plate where bone growth occurs

Front 26

Membranes

-Periosteum

Back 26

2 Layer Membrane covers external bone (except joints)

-nerve fibers & blood vessels provide shaft w/ nutrients via foramen openings.

-Anchoring points for tendons/ligaments.

Front 27

Fibrous layer

Back 27

Fibrous Layer:

Outer layer of Dense Irregular tissue, consisting of Sharpey's fibers that secure to bone matrix.

Front 28

Osteogenic layer

Back 28

Osteogenic Layer:

Inner layer abutting bone, contains osteogenic stem cells, gives rise to almost all bone cells.

Front 29

Endosteum

Back 29

Endosteum:

-C.T membrane covering internal bone

-Covers trabeculae

-Line canals of compact bone.

-Contains osteogenic cells , can change into other bone cells.

Front 30

Hematopoietic Tissue in Bones

-Red Marrow

-Yellow Marrow

Back 30

In trabecular cavities of spongy bone

-Newborns, medullary cavities & spongy bone contain red marrow

Yellow marrow found in middle of long bones. - made of fat cells, body’s natural energy & blood reserve.

-Adults, red in heads of femur/humerus, flat bone diploe, hips

-Yellow can convert to red, in anemic people

Front 31

Bone Marking

Back 31

-Site of muscle, ligament & tendon attachment

-involved in joint formation/conduits for blood vessels & nerves.

Front 32

Three types of bone making:

1. Projection

Back 32

Outward bulge of bone

-Due to increased stress from muscle pull or modification for joints.

Front 33

2. Depression

Back 33

Groove shaped cut-out that can serve as passageway for vessels & nerves, or joint attachment

Front 34

3. Opening

Back 34

Hole / Canal, serves as passageway for blood vessels/nerves.

Front 35

Bone Cell Types

Back 35

Five majors cell types

1. Osteogenic cells

2. Osteoblasts

3. Osteocytes

4. Bone-lining cells

5. Osteoclasts

Front 36

1. Osteogenic Cells

Back 36

Osteogenic:

- Stem Cell (AKA Osteoprogenitor cell)

-Mitotically active in periosteum & endosteum.

-can differentiate into osteoblast/bone-lining cells

Front 37

2. Osteoblasts

Back 37

Osteoblast:

Secretes Matrix (Osteoid), bone growth cell (can divide)

-Osteoid: collagen & calcium-binding proteins

Front 38

3. Osteocytes

Back 38

Osteocyte:

Mature cell (in lacunae) no longer divide, maintains bone matrix (senses stress/strain)

Front 39

4. Bone-Lining Cell

Back 39

Bone-Lining Cell:

-Flat cells on bone surface, help maintain matrix

External-Periosteal, Internal-Endosteal

Front 40

5. Osteoclast

Back 40

Osteoclast:

Bone breaking-down & reforming cell

Front 41

Compact Bone (lamellar bone)

Back 41

-Osteon

-Canals & canaliculi.

-Interstitial & circumferential lamellae.

Front 42

-Osteon (Harversian System)

Back 42

-Structural unit of bone, weight-bearing pillars

-Osteon cylinder -> rings of bone matrix called Lamellae (like tree rings)

Front 43

-Lamellae

Back 43

Lamellae:

-Contain collagen fibers (bone salts between) that run in different directions in adjacent rings

-Resists stress/twists

Front 44

-Interstitial Lamellae

Back 44

Interstitial Lamellae:

-Lamellae not part of Osteon

-Fills gaps between forming Osteons, remnant of bone remodeling

Front 45

-Circumferential Lamellae

Back 45

Circumferential Lamellae:

-Between Periosteum & Endosteum

-Lamellae layer around surface of diaphysis

(resist twisting)

Front 46

-Cental (Haversian) Canal

Back 46

Central (Haversian) Canal:

-Runs through core of Osteon (holds blood vessels & nerves)

Front 47

-Perforating (Volkmann's) Canals

Back 47

Volkmann's Canals:

-Endosteum-lined canals running horizontally

-Connects blood vessels & nerves of periosteum, medullary cavity, and cental canal

Front 48

Lacunae (Osteocytes)

Back 48

Lacunae:

Small cavities that contain Osteocytes

Front 49

Canaliculi

Back 49

Canaliculi:

Hairlike canals connect lacunae to each other & central canal

Front 50

Spongy Bone

Back 50

Spongy Bone:

-Appears poorly organized, but actually organized along lines of stress to resist stresses

Front 51

Trabeculae

Back 51

Trabeculae:

-Suspension-like cables give bone strength

-No osteons, contain irregularly arranged lamellae & osteocytes interconnected by canaliculi.

-Capillaries in endosteum supply nutrients

Front 52

Organic Bone Components

Back 52

-Bone Tissue Cells & Osteoid.

-Resilience from sacrificial cells -> stretch/break to dissipate energy & prevent fractures (bonds reform)

Front 53

Osteoid

Back 53

Osteoid:

-1/3 of organic bone matrix

-ground substances and collagen fibers = high tensile strength /flexibility

1. Proteoglycans

2. Glycoproteins

Front 54

Inorganic Bone Components:

Hydroxylapatities(Minerals salts)

Back 54

Hydroxylapatites:

- 65% of bone tissue

-calcium phosphate crystals in/around collagen fibers, decompose slowly

(hardness & compression resistance)

Front 55

Ossification (osteogenesis)

Back 55

Ossification (osteogenesis):

-Bone tissue formation (2nd month of fetus)

-Postnatal growth until early adulthood.

-Bone remodeling/repair = lifelong

Front 56

Formation of the Bony Skeleton

Back 56

Week 8 -> fibrous membranes/hyaline cartilage of fetal skeleton replaced with bone tissue

Front 57

Endochondral Ossification

Back 57

Endochondral Ossification:

-Forms all bones below skull (not clavicle)

-Developed by replacing hyaline cartilage

(2nd month of development)

Front 58

Primary Ossification Center

Back 58

Primary Ossification Center:

-Center of hyaline cartilage shaft -> endochondral ossification occurs

-Blood vessels infiltrate perichondrium, converting it to periosteum

-Mesenchymal cells become osteoblasts

Front 59

5 Stage process for Endochondral Ossification

Back 59

1. Bone collar forms around Diaphysis

2. Central cartilage calcifies, develops cavities

3. Periosteal Bud (vessels, nerves, red marrow, osteogenic & osteoblast cells) invades cavities, forms spongy bone.

4.Diaphysis elongates, Medullary cavity forms.

((Secondary Ossification Centers appear in epiphyses))

5.Epiphyses ossify-Hyaline cartilage remains only in epiphyseal plates/articular cartilages

Front 60

Intramembranous Ossification

Back 60

Intramembranous Ossification:

-Fibrous C.T membrane formed by mesenchymal cells

-Forms skull bones ( frontal, parietal, occipital, temporal) & clavicles

Front 61

4 Major Steps for Intramembranous Ossification

Back 61

1.Ossification Center appears in fibrous C.T

2.Bone matrix (Osteoid) secreted in fibrous membrane -> calcifies

3.Woven bone & Periosteum form

4.Lamellar bone replaces woven bone beneath Periosteum. Red marrow appears.

Front 62

Postnatal Bone Growth

Back 62

Postnatal Bone Growth:

-Long bones grow lengthwise by interstitial/longitudinal growth of epiphyseal plate

-Bones increase thickness through appositional growth.

-Bones stop growing during adolescence

-Some facial bones continue to grow

Front 63

Growth in Length of Long Bones

Back 63

-Interstitial growth requires epiphyseal cartilage in the epiphyseal plate

-Epypheseal plate maintains constant thickness

-Rate of cartillage growth on one side balanced by bone replacement on other

Front 64

Epiphyseal Plate Consist of Five Zones

Back 64

1. Resting (quiescent) zone-Inactive Cartilage on epiphyseal side of epiphyseal plate

2. Proliferation (growth) zone- Rapidly dividing cartilage on diaphysis side of epiphyseal plate - New cells move upward, pushing epiphysis away from diaphysis = lengthening

3. Hypertrophic zone- Old chondrocytes closer to diaphysis have lacunae enlarge/ erode, interconnecting spaces form

4. Calcification zone-Cartilage matrix calcifies; chondrocytes die/deteriorate.

5. Ossification (osteogenic) zone- new bone forms

Front 65

End of Adolescence

Back 65

End of Adolescence:

-Chondroblast divide less

-Epiphyseal plate thins, replaced w/ bone, closes -> epiphysis & diaphysis fuse

-Bone lengthening stops (females18, males21)

Front 66

Growth in Width (Thickness)

Back 66

-Bones widen through appositional growth (response to increase stress/weight/activity)

-more build than break, forming thicker bones

Front 67

Hormonal Regulation of Bone Growth:

Back 67

-Stimulates epiphyseal plate activity in infancy/childhood (anterior pituitary gland)

-Thyroid Hormone: Modulates activity/proportions of growth hormones

-Testoterone/Estrogen at Puberty:

-Promote adolescent growth spurts

-Epiphyseal plate closure ends growth

Abnormal skeletal growth: caused by excesses/deficits of any hormone

Front 68

Bone Remodeling

Back 68

-Bone Deposit/Resorption on surface of periosteum & endosteum

-5-7% bone mass recycled each week, Spongy-replaced 3-4 yrs, Compact replaced 10 yrs.

-Remodeling Unit: Osteoblast/Osteoclast packets

Front 69

Bone Deposits

Back 69

-New bone matrix deposited by osteoblasts

-deposit triggered by: mechanical signals, increased calcium/phosphate concentration (hydroxylapatites, matrix proteins), algalune phosphatase enzyme for mineralization

Front 70

Osteoid Seam & Calcification Front

Back 70

Osteoid Seam: Band of unmineralized bone matrix = new matrix

Calcification Front: Transtion zone between osteoid seam & old mineralized bone

Front 71

Bone Resorption

Back 71

Osteoclast function:

-Secrete lysosomal enzymes & protons (H+) that digest & phagocytize matrix

-Osteoclasts activation involves PTH (parathyoid hormone) and immune T cell proteins

-regulated by hormones & mechanical stress response

Front 72

1. Hormonal Control

-Parathyroid Hormone (PTH)

Back 72

PTH:

Low calcium level response by parathyroid gland

-Stimulates osteoclasts to resorb bone, release calcium back to blood, controlled by homeostatic calcium levels.

Front 73

-Calcitonin

Back 73

High calcium blood levels = Calcitonin release by parafollicular cells of thyroid gland

-Causes bones to store calcium

Front 74

Hypocalcemia

Back 74

Low levels of calcium cause hyperexcitablility, spasms

Front 75

Hypercalcemia

Back 75

High levels of calcium cause nonresponsiveness.

Sustained High Blood Calcium Levels:
calcium salts in blood vessels/kidney=kidney stones

Front 76

Serotonin & Leptin

Back 76

Leptin: Adipose tissue hormone, regulates bone density, inhibits osteoblasts

Serotonin: -Neurotransmitter (made in gut after meal = eating regulates calcium stores) regulates mood & sleep, inhibits osteoblasts

Front 77

Wolf's law states

Back 77

Bones grow/remodel in response to demands, (stress bends & stretches bones, thickest where stress greatest)

-Bone can be hollow because compression and tension cancel each other out in center of bone

Front 78

Wolf's law also explains:

Back 78

-Handedness= thicker/stronger bone in that limb

-Curved bones thickest where most likely to buckle

-Trabeculae form trusses along lines of stress.

Large, bony projections= heavy, active muscle attach

Front 79

Cont. of control remodeling

Back 79

Remodeling control:

-Mechanical stress -> remodeling w/ electric signals where deformations occur

- Hormonal Control= If & When

- Mechanical Stress= Where

Front 80

Fractures

Back 80

-Fractures = breaks

-youth = physical trauma, old = bone thinning

Front 81

Three Fractures Classification:

1. Position of bone ends after fracture:

Back 81

-Nondisplaced: Ends retain normal position

-Displaced: Ends are out of normal alignment

Front 82

2. Completeness of break:

Back 82

-Complete: Broken all the way through.

-Incomplete: Not broken all the way through.

Front 83

3. Whether skin is penetrated:

Back 83

-Open (compound): Skin is penetrated.

-Closed (simple): Skin is not penetrated.

Front 84

Fracture Tratment and repair

Back 84

Treatment = reduction, realignment of broken ends

-Closed reduction: physician manipulates to correct position

-Open reduction: surgical pins or wires secure ends.

Front 85

Immobilization

Back 85

Bone immobilized by cast to heal

-Time needed for repair depends on break severity, bone broken, and age of patient.

Front 86

Repair Involves four major stages

Back 86

Fracture Repair:

-Hematoma formation

-Fibrocartilaginous callus formation

-Bony callus formation

-Bone remodeling

Front 87

1.Hematoma Formation:

Back 87

-Torn blood vessels hemorrhage, forming mass of clotted blood called a Hematoma.

-Site is swollen, painful, and inflamed.

Front 88

2.Fibrocartilaginous Callus formation

Front 89

3.Bony callus Formation

Front 90

4. Bone Remodeling

Front 91

Bone Disorders

Back 91

bone deposit/resorption imbalances

-Osteomalacia and rickets

-Osteoporosis

-Paget's disease

Front 92

Osteomalacia

Back 92

-Bones are poorly mineralized

-Osteoid is produced, but calcium salts not adequately deposited.

-Result is soft, weak bones.

-Pain upon bearing weight.

Front 93

Rickets (Osteomalacia of children)

Back 93

-Results in bowed legs and other bone deformities because bones ends are enlarged and abnormally long.

-Cause: Vitamin D deficiency or insufficient dietary calcium.

Front 94

Osteoporosis

Back 94

-Is a group of diseases in which bone resorption exceeds deposits.

-Matrix remains normal, but bone mass declines.

-Spongy bone of spine and neck of femur most susceptible. (Vertebral and hip fractures common)

Front 95

Osteoporosis risk factors

Back 95

-Most often aged, postmenopausal women. (Estrogen plays a role in bone density, so when levels drop at menopause, women run higher risk)

- Men are less prone due to protection by the effects of testosterone.

-Petite body form

-Diet poor in calcium and protein.

-Smoking

-Insuficiente exercise to stress bone,

Front 96

Paget's Disease (pagetic bone)

Back 96

-Excessive and haphazard bone deposits and resorption cause bone to be made fast and poorly.

-Very high ratio of spongy to compact bone and reduced mineralization.

-Usually occurs in spine, pelvis, fémur, and skull

-Rarely occurs before age 40.

-Treatment includes calcitonin and bisphosphonates.

Front 97

Developmental Aspects of Bone

Back 97

-Embryonic skeleton ossifies predictably, so fetal age is easily determined from X rays or sonograms.

-most long bones begin ossifying by 8 weeks, with primary ossification centers developed by week 12

Front 98

Developmental Aspects of Bone

Back 98

-Embryonic skeleton ossifies predictably, so fetal age is easily determined from X rays or sonograms.

-Most long bones begin ossifying by 8 weeks, with primary ossification centers developed by week 12

Front 99

Birth to Young Adulthood

Back 99

-At birth, most long bones ossified, except at epiphyses.

-Epiphyseal plates persist through childhood and adolescence.

-At ~ age 25, all bones are completely ossified, and skeletal growth ceases.

Front 100

Age-Related Changes in Bone

Back 100

-In children and adolescents, bones formation exceeds resorption. (Males tend to have greater mass than females)

-In young adults, both are balanced.

-In adults, bones resorption exceeds formation.

Front 101

Aged- Related Changes in Bone

Back 101

-Bone density changes over lifetime are largely determined by genetics.

*Gene for vitamin D's cellular docking determines mass early in life and osteoporosis risk at old age.

-Bone mass, mineralization, and healing ability decrease with age beginning in fourth decade.

*Except bones of skull.

*Bone loss is greater in whites and females.

Front 102

Fracture Types of Bones :

1. Comminuted

Back 102

-Bone fragments into three or more pieces.

-Particularly common in the aged, whose bones are more brittle.

Front 103

2. Compression

Back 103

-Bone is crushed.

-Common in porous bones (i.e, osteoporotic bones) subjected to extreme trauma, as a fall.

(Crushed vertebrae)

Front 104

3. Spiral

Back 104

-Ragged break occurs when excessive twisting forces are applied to a bone.

-Common sports fracture.

Front 105

4. Epiphyseal

Back 105

-Epiphyseal separates from the diaphysis along the Epiphyseal plate.

-Tends to occur where cartilage cells are dying and calcification of the matrix is occurring.

Front 106

5. Depressed

Back 106

-Broken bone portion is pressed inward.

-Typical of skull fracture.

Front 107

6. Greenstick

Back 107

-Bone breaks incompletely, much in the way a green twig breaks. Only one side of the shaft breaks; the other side bends.

-Common in children, whose bones have relatively more organic matrix and more flexible than those of adults.