skeletal system
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Skeletal System. Chapter 5. The Skeletal System. Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments Two subdivisions of the skeleton Axial skeleton Appendicular skeleton. Functions of Bones. Support the body Protect soft organs - PowerPoint PPT PresentationTRANSCRIPT
CHAPTER 5
Skeletal System
The Skeletal System
Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments
Two subdivisions of the skeleton Axial skeleton Appendicular skeleton
Functions of Bones
Support the bodyProtect soft organsActs as a lever for attached skeletal musclesStore minerals and fatsBlood cell formation (hematopoiesis)
Bones of the Human Body
The adult skeleton has 206 bonesTwo basic types of bone tissue
Compact bone Spongy bone
Figure 5.3a
Distalepiphysis
Diaphysis
Proximalepiphysis
Articularcartilage
Spongy boneEpiphyseallinePeriosteumCompact boneMedullarycavity (linedby endosteum)
(a)
Anatomy of a Long Bone
Diaphysis Shaft Composed of compact bone
Epiphysis Ends of the bone Composed mostly of spongy bone
Figure 5.3c
Yellowbone marrow
Compact bone
Perforating(Sharpey’s)fibers
Nutrientarteries
Periosteum
Endosteum
(c)
Anatomy of a Long Bone
Periosteum Fibrous connective tissue membrane, covers
outside of the diaphysisPerforating (Sharpey’s) fibersHyaline cartilage lines joint surfacesArteries
Anatomy of a Long Bone
Epiphyseal plate (Young) Flat plate of hyaline
cartilage Epiphyseal line
(Adults) Remnant of the
epiphyseal plate
Distalepiphysis
Diaphysis
Proximalepiphysis
Articularcartilage
Spongy boneEpiphyseallinePeriosteumCompact boneMedullarycavity (linedby endosteum)
(a)
Anatomy of a Long Bone
Marrow (medullary) cavity Contains yellow marrow (mostly fat) in adults Infants: red marrow for blood cell formation
In adults: red marrow is cavities of spongy bone
Microscopic Anatomy of Compact Bone
Osteon (Haversian system) Central canal and matrix rings Carries blood vessels and nerves
Perforating (Volkmann’s) canal Carries blood vessels and nerves
Figure 5.4a
CompactbonePeriostealblood vesselPeriosteum
Perforatingfibers
Central (Haversian) canalPerforating(Volkmann’s) canalBlood vessel
Spongy bone
Blood vessel continues intomedullary cavity containing marrow
Lamellae
(a)
Osteon(Haversian system)
Microscopic Anatomy of Bone
Lacunae Cavities containing bone cells (osteocytes) Arranged in concentric rings called lamellae
Lamellae Calcified cartilage surrounding lacunae
Formation of the Human Skeleton
In embryos, the skeleton is primarily hyaline cartilage
During development, much of this cartilage is replaced by bone
Cartilage remains in isolated areas Bridge of the nose Parts of ribs Joints
Bone Growth (Ossification)
Epiphyseal plates allow for lengthwise growth of long bones during childhood New cartilage is continuously formed Older cartilage becomes ossified
Cartilage is broken down Enclosed cartilage is digested away, opening up a
medullary cavity Bone replaces cartilage through the action of osteoblasts
Bone Growth (Ossification)
Bones are remodeled and lengthened until growth stops Bones are remodeled in response to two factors
Blood calcium levels Pull of gravity and muscles on the skeleton
Bones grow in width (called appositional growth)
Figure 5.5
In a fetusIn an embryo
Bone collarHyalinecartilagemodel
Bone startingto replacecartilage
In a child
Medullarycavity
New center ofbone growth
Hyalinecartilage
Epiphysealplate cartilage
Growthin bonelength
New boneforming
Invadingbloodvessels
Epiphysealplatecartilage
Articularcartilage
Spongybone
New boneforming
Growthin bonewidth
Figure 5.6
Bone growth
Bone grows inlength because:
Bone remodeling
Growing shaft isremodeled as:
Cartilagegrows here.
Cartilageis replacedby bone here.
Cartilagegrows here.
Cartilageis replaced by bone here.
1
2
3
4
1
2
3 Bone isresorbed here.
Epiphyseal plate
Articular cartilage
Bone isresorbed here.
Bone is addedby appositionalgrowth here.
Bone Remodeling• Osteocytes are mature bone cells
• Osteoclasts digest organic matric in response to PTH
• Increases blood calcium levels
• Osteoblasts form organic matric in response to calcitonin
• Decrease blood calcium levels
• Mechanical and gravitational forces also affect remodeling
17
Bone Remodeling
• Balance between resorption and formation
18
Bone Fractures
Fracture—break in a boneTypes of bone fractures
Closed (simple) fracture—break that does not penetrate the skin
Open (compound) fracture—broken bone penetrates through the skin
Common Types of Fractures
Comminuted—bone breaks into many fragments
Compression—bone is crushedDepressed—broken bone portion is pressed
inwardImpacted—broken bone ends are forced into
each otherSpiral—ragged break occurs when excessive
twisting forces are applied to a boneGreenstick—bone breaks incompletely
Figure 5.7
Internalcallus(fibroustissue andcartilage)
Hematomaforms.
Fibrocartilage callus forms.
Bony callus forms.
Bone remodeling occurs.
1 2 3 4
HematomaBonycallus ofspongybone
Spongybonetrabecula
Newbloodvessels
Externalcallus
Healedfracture
Inflammatory Conditions Associated with Joints
Bursitis—inflammation of a bursa usually caused by a blow or friction
Tendonitis—inflammation of tendon sheathsArthritis—inflammatory or degenerative
diseases of joints Over 100 different types Autoimmune disease
Clinical Forms of Arthritis
Osteoarthritis Most common chronic arthritis, related to normal
aging processesRheumatoid arthritis
An autoimmune disease—the immune system attacks the joints
Gouty arthritis Deposition of uric acid crystals from the blood
Figure 5.33