Post on 21-Jan-2020
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The Skeletal System
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The Skeletal System • Parts of the skeletal system – Bones – Joints – Ligaments – Car8lage
• Divided into two divisions – Axial – longitudinal axis – Appendicular – limbs and girdles
The Axial Skeleton
• Forms the longitudinal part of the body • Axial skeleton parts: – Skull – Ribs – Spine – Vertebral column
The Appendicular Skeleton
• Forms off of the longitudinal part of the body • Appendicular skeleton parts – Arms & legs – Scapula – Clavicle – Pelvis
The Axial and Appendicular Skeleton
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Func8ons of Bones
• Support of the body • Protec8on of soL organs – Skull and vertebrae for brain and spinal cord – Rib cage for thoracic cavity organs
• Movement due to aNached skeletal muscles • Storage of minerals (Ca+ and P) and fats • Blood cell forma8on (hematopoiesis)
Bones of the Human Body • The adult skeleton has 206 bones • Two basic types of bone 8ssue – Compact bone
• Homogeneous
– Spongy bone • Small needle-‐like
pieces of bone • Many open
spaces
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Classifica8on of Bones on the Basis of Shape
Figure 5.1
• Bones are classified as: – Long – Short – Flat – Irregular
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Classifica8on of Bones on the Basis of Shape
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Classifica8on of Bones • Long bones – Typically longer than wide – Have a shaL with heads at both ends
– Contain mostly compact bone • Examples: Femur, humerus
• Short bones – Generally cube-‐shape – Contain mostly spongy bone • Examples: Carpals, tarsals
Classifica8on of Bones • Flat bones – Thin and flaNened, usually curved – Thin layers of compact bone around a layer of spongy bone • Examples: Skull, ribs, sternum
• Irregular bones – Irregular in shape – Do not fit into other bone classifica8on categories • Example: Vertebrae and hip
Gross Anatomy of a Long Bone
• Diaphysis – ShaL – Composed of compact bone
• Epiphysis – Ends of the bone – Composed mostly of spongy bone
Figure 5.2a
Structures of a Long Bone
• Periosteum – Outside covering of the diaphysis
– Fibrous connec8ve 8ssue membrane
• Sharpey’s fibers – Secure periosteum to underlying bone
• Arteries – Supply bone cells with nutrients
Structures of a Long Bone
• Ar8cular car8lage – Covers the external surface of the epiphyses
– Made of hyaline car8lage
– Decreases fric8on at joint surfaces
Figure 5.2a
Structures of a Long Bone
• Medullary cavity – Cavity of the shaL – Contains yellow marrow (mostly fat) in adults
– Contains red marrow (for blood cell forma8on) in infants
Figure 5.2a
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• Epiphyseal plate – Flat plate of hyaline car8lage seen in young, growing bone
• Epiphyseal line – Remnant of the epiphyseal plate
– Seen in adult bones
Anatomy of a Long Bone
Distal epiphysis
Diaphysis
Proximal epiphysis
Ar8cular car8lage
Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum)
(a)
Changes in the Human Skeleton
• In embryos, the skeleton is primarily hyaline car8lage • During development, much of this car8lage is replaced by bone = ossifica8on • Car8lage remains in isolated areas – Bridge of the nose – Parts of ribs – Joints
Long Bone Forma8on and Growth