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SECTION 6-1: Introduction to the skeletal system . Skeletal system includes: Bones of the skeleton Cartilages, ligaments and other connective tissues that stabilize and connect Functions of skeletal system Support Storage of minerals and lipids Blood cell production Protection Leverage.

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section 6 1 introduction to the skeletal system
SECTION 6-1:Introduction to the skeletal system

Skeletal system includes:

  • Bones of the skeleton
  • Cartilages, ligaments and other connective tissues that stabilize and connect

Functions of skeletal system

  • Support
  • Storage of minerals and lipids
  • Blood cell production
  • Protection
  • Leverage
section 6 2 classification of bones
SECTION 6-2:Classification of Bones
  • Long
  • Flat
  • Short
  • Irregular
  • Sesamoid
  • Sutural

Bone shapes

Bone Structure

  • Compact bone (dense)
  • Spongy bone (cancellous)
a typical long bone includes
A typical long bone includes
  • Diaphysis
  • Epiphyses
  • Metaphysis
  • Articular cartilage
  • Marrow cavity
    • Filled with red or yellow marrow
  • Articularcartlilage
section 6 3 bone histology
SECTION 6-3: Bone Histology

Osseous tissue

  • solid matrix- Crystals of hydroxyapatite

Ca3(PO4)2+ Ca(OH)2

  • Collagen-
  • Vascular-
section 6 3 bone histology1
SECTION 6-3: Bone Histology

4. Wrapped

a. Endosteum

b. Periosteum

i. fibrous layer

ii. Cellular layer(osteogenic)-

iii. Sharpey’s Fibers

cells in bone
Cells in bone:
  • Osteocytes = mature bone cells

-Maintain, repair bone

2. Osteoblasts= synthesize new matrix

- become osteocyte

3. Osteoclasts=dissolve bone matrix

-multicuncleated, differentiate from WBC

4.Osteoprogenitor =cells differentiate into osteoblasts, repair fractures

compact bone and spongy bone
Compact bone and spongy bone
  • Basic unit of compact bone is an osteon
    • Osteocytes arranged around a central canal
    • Perforating canals extend between adjacent osteons
  • Spongy bone contains trabeculae
figure 6 5 the distribution of forces on a long bone
Figure 6.5 The Distribution of Forces on a Long Bone

Bones and stress

  • Compact bone located where stresses are limited in direction
  • Spongy bone located where stresses are weaker or multi-directional

Figure 6.5

section 6 4 bone development and growth
SECTION 6-4: Bone development and growth
  • Ossification = converting other tissue to bone

1. Intramembranous

2. Endochondral

  • Calcification = depositing calcium salts within tissues
1 intramembraneous ossification
1. Intramembraneous Ossification
  • Bones form w/in a thin CT membrane
  • Used to form flat bones (cranium, mandible, clavicle)
intramembranous ossification

forming bone: red

cartilage: blue

Intramembranous ossification
  • Begins with osteoblast differentiation
  • Dermal bones produced
  • Begins at ossification center
steps of intramembraneous ossification in cranium
Steps of Intramembraneous Ossification in cranium
  • Mesenchymal cells form a thin CT membrane covering brain
  • Some mesenchymal cells differentiate into osteoblasts in the center of each membrane.(Occurs 6 weeks after fertilization)
  • Osteoblasts secrete bone @ these locations(called primary centers of ossification)
  • Ossification spreads in all directions
steps of intramembraneous ossification in cranium1
Steps of Intramembraneous Ossification in cranium
  • @ birth ossification is not complete, membrane remains as sutures and fontanels(soft spots)

Fetal skulls at 13-34 weeks gestation; fontanels typically close at 6 months

fontanelles
Fontanelles
  • indentations of fibrous membrane between bones of fetal skull
  • Intramembranous ossification is not complete until 20-22 months
  • anterior
  • posterior
  • sphenoid
  • mastoid
endochondral ossification
Endochondral ossification
  • Cartilage model gradually replaced by bone at metaphysis
    • Increasing bone length
  • Timing of epiphyseal closure differs
  • Appositional growth increases bone diameter
bone growth
Bone Growth

1. Appositional- increases diameter, while medullary cavity hollowed out

-

bone growth1
Bone Growth

2. Interstitial- occurs at epiphyseal plates

a. Chondroblasts produce new cells that are pushed toward epiphysis

b. At the diaphysis end of plate older cartilage is converted into bone

http://www.personal.psu.edu/staff/m/b/mbt102/bisci4online/bone/bone_growth4.swf

section 6 5 dynamic nature of bone
SECTION 6-5: Dynamic Nature of Bone

continually changing

  • Remodeling
  • Exercise
  • Hormone levels
    • Growth hormone and thyroxine increase bone mass
    • Calcitonin and PTH control blood calcium levels
the skeleton is a calcium reserve
The skeleton is a calcium reserve
  • 99% body’s calcium in the skeleton
  • Calcium ion concentration maintained by bones GI tract and kidneys
  • Calcitonin and PTH regulate blood calcium levels
    • Calcitonin decreases blood calcium levels
    • PTH increases blood calcium levels
effects on bone growth
Effects on bone growth
  • Growth hormone- produced by pituitary gland; targets growth plate activity

a. Excess causes giagantism

slide33
b. Low levels cause pituitary dwarfism
  • normally proportioned
  • treatment with growth hormone
effects on bone growth1
Effects on bone growth

2. Testosterone- produced by the testes and adrenal glands in males and by the adrenal glands in females

-Responsible for the growth “spurt’ at puberty

-Overproduction in males causes closure of the epiphyseal line

(Caution for anabolic steroid users)

effects on bone growth2
Effects on bone growth
  • Estrogen- produced by the ovaries in females; -stimulates osteoblasts

-promotes closing of the epiphyseal line

-MENOPAUSE causes bone loss!!!

section 6 7 aging and the skeletal system
SECTION 6-7: Aging and the Skeletal System

Effects of aging include

1. Osteopenia (inadequate ossification) begins between ages 30 and 40,

  • osteoblast activity declines, while osteoclast activity remains level,
  • Women lose 8% of bone mass per decade, while men lost only 3% in the same time period

2. Osteoporosis

osteoporosis
Osteoporosis

When the loss of bone mass compromises normal function a person is diagnosed with osteoporosis

  • When the loss of bone mass compromises normal function a person is diagnosed with osteoporosis.
effects on bone growth3
Effects on bone growth

4. Parathyroid hormone- produced by the parathyroid glands in the neck

-Stimulates the osteoclasts to Ca++ to be released from the bone to enter the blood

-Ca++ necessary for muscles and nerves to function properly

effects on bone growth4
Effects on bone growth

5. Calcitonin- produced by the thyroid gland

- Inhibits osteoclasts so Ca++ remains in the bone , promotes ostepoblasts

effects on bone growth5
Effects on bone growth

6. Vitamin D- some is produced in the skin ; Most is ingested in food

-Necessary for the absorption of Ca++ from the intestine into the blood

  • -Osteomalacia (Rickets in children)
    • causing softened, weakened bones
    • Main symptom is pain when weight is put on the affected bone
bone fractures breaks
Bone Fractures (Breaks)

Bone fractures are classified by:

Simple(closed) vs. compound(open)

types of bone fractures
Types of Bone Fractures
  • Linear
    • the fracture is parallel to the long axis of the bone
  • Transverse
    • the fracture is perpendicular to the long axis of the bone
types of bone fractures1
Types of Bone Fractures
  • Greenstick
    • incomplete fracture where one side of the bone breaks and the other side bends
    • common in children
types of bone fractures2
Types of Bone Fractures
  • Comminuted
    • bone fragments into three or more pieces
    • common in the elderly
types of bone fractures3
Types of Bone Fractures
  • Spiral
    • ragged break when bone is excessively twisted
    • common sports injury
types of bone fractures4
Types of Bone Fractures
  • Depressed
    • broken bone portion pressed inward
    • typical skull fracture
types of bone fractures5
Types of Bone Fractures
  • Compression
    • bone is crushed; common in porous bones
types of bone fractures6
Types of Bone Fractures
  • Epiphyseal
    • epiphysis separates from diaphysis along epiphyseal line; occurs where cartilage cells are dying
fracture repair
Fracture repair
  • Fracture hematoma
  • Internal and External callus
  • Cartilage replaced by bone
  • Osseous callus removed

Bone graft- a transplant of bone to stimulate repair