The Skeletal System

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The Skeletal System
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The Skeletal System

• Parts of the skeletal system
• Bones (skeleton)
• Joints
• Cartilages
• Ligaments (bone to bone)(tendonbone to muscle)
• Divided into two divisions
• Axial skeleton forms long axis of body
• Appendicular skeleton limbs and girdle

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Functions of Bones

• Support of the body
• Protection of soft organs
• Movement due to attached skeletal muscles
• Storage of minerals and fats
• Blood cell formation

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Bones of the Human Body

• The skeleton has 206 bones
• Two basic types of bone tissue
• Compact bone
• Homogeneous
• Spongy bone
• Small needle-like pieces of bone
• Many open spaces

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Classification of Bones

• Long bones
• Typically longer than wide
• Have a shaft with heads at both ends
• Contain mostly compact bone
• Examples Femur, humerus

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Classification of Bones

• Short bones
• Generally cube-shape
• Contain mostly spongy bone
• Examples Carpals, tarsals

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Classification of Bones on the Basis of Shape
Figure 5.1
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Classification of Bones

• Flat bones
• Thin and flattened
• Usually curved
• Thin layers of compact bone around a layer of
  spongy bone
• Examples Skull, ribs, sternum

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Classification of Bones

• Irregular bones
• Irregular shape
• Do not fit into other bone classification
  categories
• Example Vertebrae and hip

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Classification of Bones on the Basis of Shape
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Gross Anatomy of a Long Bone

• Diaphysis
• Shaft
• Composed of compact bone
• Epiphysis
• Ends of the bone
• Composed mostly of spongy bone

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Structures of a Long Bone

• Periosteum
• Outside covering of the diaphysis
• Fibrous connective tissue membrane
• Sharpeys fibers
• Secure periosteum to underlying bone
• Arteries
• Supply bone cells with nutrients

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Structures of a Long Bone

• Articular cartilage
• Covers the external surface of the epiphyses
• Made of hyaline cartilage
• Decreases friction at joint surfaces

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Structures of a Long Bone

• Medullary cavity
• Cavity of the shaft
• Contains yellow marrow (mostly fat) in adults
• Contains red marrow (for blood cell formation) in
  infants

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Bone Markings

• Surface features of bones
• Sites of attachments for muscles, tendons, and
  ligaments
• Passages for nerves and blood vessels
• Categories of bone markings
• Projections and processes grow out from the
  bone surface
• Depressions or cavities indentations

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Bone Markings Table 7.4
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Microscopic Anatomy of Bone

• Osteon (Haversian System)
• A unit of bone
• Central (Haversian) canal
• Opening in the center of an osteon
• Carries blood vessels and nerves
• Perforating (Volkmans) canal
• Canal perpendicular to the central canal
• Carries blood vessels and nerves

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Microscopic Anatomy of Bone
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Microscopic Anatomy of Bone

• Lacunae
• Cavities containing bone cells (osteocytes)
• Arranged in concentric rings
• Lamellae
• Rings around the central canal
• Sites of lacunae

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Microscopic Anatomy of Bone

• Canaliculi
• Tiny canals
• Radiate from the central canal to lacunae
• Form a transport system

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Types of Bone Cells

• Osteocytes
• Mature bone cells
• Osteoblasts
• Bone-forming cells
• Osteoclasts
• Bone-destroying cells
• Break down bone matrix for remodeling and release
  of calcium
• Bone remodeling is a process by both osteoblasts
  and osteoclasts

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Bone Fractures

• A break in a bone
• Types of bone fractures
• Closed (simple) fracture break that does not
  penetrate the skin
• Open (compound) fracture broken bone penetrates
  through the skin
• Bone fractures are treated by reduction and
  immobilization
• Realignment of the bone

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Common Types of Fractures
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Common Types of Fractures
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Repair of Bone Fractures

• Hematoma (blood-filled swelling from ruptured
  blood vessels) is formed
• Break is splinted by fibrocartilage to form a
  callus
• Fibrocartilage callus is replaced by a bony
  callus
• Bony callus is remodeled by osteoclasts to form a
  permanent patch

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Stages in the Healing of a Bone Fracture
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The Axial Skeleton
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The Axial Skeleton

• Forms the longitudinal part of the body
• Divided into three parts
• Skull
• Vertebral column
• Bony thorax

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The Skull

• Two sets of bones
• Cranium encloses and protects the brain, and its
  surface provides attachments for muscles that
  make chewing and head movement possible.
• 8 bones in the cranium
• Frontal (1)
• Parietal (2)
• Occipital (1)
• Temporal (2)
• Sphenoid (1)
• Ethmoid (1)

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The Skull (Continued)

• Facial bones - 14 Facial bones
• Maxillary (2)
• Palatine (2)
• Zygomatic (2)
• Lacrimal (2)
• Nasal (2)
• Vomer (1)
• Inferior nasal conchae (2)
• Mandible

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The Skull (Continued)

• Bones are joined by sutures (Major Sutures)
• Squamous sutures
• Coronal suture
• Lambdoidal suture
• Sagittal suture
• Only the mandible is attached by a freely movable
  joint

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Skull Lateral View
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Skull Anterior View
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Skull, Superior View
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Skull, Inferior View
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The Hyoid Bone

• The only bone that does not articulate with
  another bone
• Serves as a moveable base for the tongue

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The Vertebral Column

• Vertebrae separated by intervertebral discs
• The spine has a normal curvature
• Each vertebrae is given a name according to its
  location

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The Vertebral Column

• Each vertebrae is given a name according to its
  location
• 7 cervical vertebrae are in the neck
• 12 thoracic vertebrae are in the chest region
• 5 lumbar vertebrae are associated with the lower
  back
• 9 vertebrae fuse to form two composite bones
• Sacrum
• Coccyx

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Structure of a Typical Vertebrae
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Cervical Vertebrae
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Cervical Vertebrae
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Thoracic Vertebrae
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Lumbar Vertebrae
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Sacrum and Coccyx
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The Bony Thorax

• Forms a cage to protect major organs
• Consists of three parts
• Sternum manubrium, body xiphoid process
• Ribs
• True ribs (pairs 17)
• False ribs (pairs 812)
• Floating ribs (pairs 1112)
• Thoracic vertebrae
•  

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The Bony Thorax