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Skeletal System
Skeleton • The system is composed of bones and cartilage. • A living tissue, highly specialized, hard form of connective tissue that forms the skeleton. It acts as the main support tissue of the body. It provides: > Protection for vital structures > Support for the body > mechanical basis for movement > Storage for salts, e.g. calcium > Continuous supply of new blood cells
Skeletal….. • Cartilage – a resilient, semi-rigid form of connective tissue, forming part for motion. Has no capillary blood supply of its own. Oxygen and nutrition comes from long ranged diffusion. Articulation comes from synovial joints with articular cartilage providing a gliding motion. • Parts: Axial skeleton – bones of the head (skull), neck (hyoid), and trunk (ribs, sternum, vertebrae, sacrum) Appendicular skeleton – bones of the limbs, pectoral and pelvic girdle.
Bones…. • Living bones have some elasticity ( flexibility) and rigidity ( hardness) •
Types:
compact = body or shaft spongy or cancellous (medullary cavity or marrow) • Classification: Long bones = tubular,e.g. humerus short bones = cuboidal ( ankle, tarsus and wrist, carpus) Flat bones = protective, skull bones Irregular bones = various shapes, i.e., long, short, flat ( face) Sesamoid bone = patella, knee cap ( in areas where tendons cross the ends of long bones. Protects the tendon as it angles to the attatchment)
Bones… • Accessory bones = supernumerary bones. Missing part of the main bones. Wormlike called wormian or sutural bones in the skull. Accessory bones are common in the foot.
• Heterotopic bones = form in soft tissues where they are not
normally present ( scars, riders bones in the thigh = spur, Result from straining the muscles of adducts the thigh).
• Bone markings: condyle = round articular are = lateral femoral condyle Crest = ridge of bones = iliac crest Epicondyle = eminence superior to condyle. Lateral epicondyle of humerus. Facet = smooth flat area covered with cartilage. Bones articulate with another bone (vertebra to ribs). Foramen = passage thru a bone ( obturator foramen)
Bones…. • • • • • • • • •
Facet = hollow depression ( scapula) Groove = elongated depression ( calvaria) Line = linear elevation ( soleal line of tibia) Malleolus = rounded process Notch = indentation at the edge of the bone ( G sciatic) Protuberance = projection ( occipital) Spine = thornlike process ( vertebra) Spinous process = projecting spinelike part Trochanter = large blunt elevation ( G trochanter of femur)
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Tubercle = small raised elevation or eminence,. tubercle of humerus
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Tuberosity = large rounded elevation = ischial tuberosity
Bones ….. • Trauma = being a living tissue undergoes the following changes: hurt when injured bleed when fractured remodel when stresses change with age • Bone development: = derived from the mesenchyme. – Intramembranous ossification = formed directly from mesenchyme. – Endochondral ossification = cartilaginous formation from mesenchyme whose cells condense and differentiate into chondroblasts to cartilage.
Bones … •
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Joints = an articulation and classified into: Synovial = united by an articular capsule, with synovial fluid. Most common type. Fibrous joints = united by fibrous tissue. Sutures of the skull. Cartilaginous joints = united by hyaline cartilage or fibrocartilage. Epiphyseal plates in long bones. Types of synovial joints: plane joints = permits gliding action, limited by tight articular capsule. Hinge joints = permit extension and flexion only. Saddle joint = biaxial (concave, convex)opposing surfaces shaped like a saddle . Carpometacarpal joint. Condyloid joint = biaxial(sagital and coronal), permit flexion, extension, abduction, adduction and circumduction. Ball and socket joint = multiaxial, femur and acetabulum Pivot joint = uniaxial aloow rotation. Atlantoaxial joint.
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