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Skeletal System

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									                                   Chapter 7: Skeletal System

       206 total named bones in the human body that come in various shapes and sizes
            o Long, Short, Irregular, Flat
       Formed of osseous tissue – (bone tissue) one of two hard connective tissues

FUNCTIONS:             1. Support – provides a hard framework
                       2. Protection - skull, ribcage, vertebrae
                       3. Movement/Leverage – along with muscles create movement
                       4. Mineral storage – Mostly Ca+ and PO2+; lipids in yellow marrow
                       5. Hematopoiesis – blood cell formation, mostly RBCs

Axial vs. Appendicular skeleton


STRUCTURE OF BONE: a typical long bone

          Diaphysis: (shaft) longer than it is wide; shat has two distinct ends

                 -    Marrow Cavity: center shaft of diaphasis; contains yellow marrow (fat
                      storage)

          Epiphysis: (proximal and distal expanded ends); contains spongy bone

                 -    Articular cartilage: Hyaline cartilage that covers and cushions bone ends

                 -    Epiphyseal plate: (epiphyseal line) remnants of bone growth


COMPOSITION OF BONE:
   Cells:     Osteocytes                        Osteoblasts                Osteoclasts
            Mature bone cells              Bone building cells      Break down bone (monocyte)
          - maintain composition           - produce matrix         - resorption of minerals

A. COMPACT BONE:
   - looks solid but contains few spaces where living tissue exists

       o Haversian system “osteons” – elongated cylinders parallel to the axis of long bone

       o Central (Haversian) canal – channel down the center of an osteon that contains
         bloodvessels and nerve fibers that serve bone cells

                    Perforating canals run perpendicular to the axis to deliver vessels from outer
                     to inner

B. SPONGY (CANCELLOUS) BONE:
     -    doesn't have Haversian System and has more spaces than compact bone

         o Trabeculae – honeycomb arrangement of bone tissue that lie along lines of stress

                   consists of many spaces filled with marrow:
                       - red marrow found in sternum, hip, ends of long bones

Membranes:

-    Endosteum – interior covering that lies over spongy bone

-    Periosteum – entire external surface except where cartilage exists

    o Inner layer consists of osteoblasts (osteogenic tissue) and outer layer is fibrous
      connective tissue

Organic Framework:

-    65% of the mass is made up of mineral salts

-    Combination of fibers/salts makes bone hard and durable without being brittle

DEVELOPMENT OF BONE: ossification or osteogenesis
      - Process is to convert cartilage cells into bone cells
      - Begins around week 5-6 during embryonic development


INCREASE IN BONE LENGTH:
      Epiphyseal plate: site of growth

            Epiphyseal plate's cartilage cells reproduce to keep the thickness constant
            - cartilage forms tall column of cells, dividing quickly at the top to push the plate
               away from the diaphysis

            -   the rate of cartilage growth on the epiphyseal side is equal to replacement of
                bony tissue on diaphysis side

            Plates become thinner and thinner as adolescence hits 18 to 21 yrs of age


Growth of bones controlled by Human Growth Hormone and Thyroid hormones


Bone Markings
      - Distinguishable markings on bone that are created for attachment, create joints,
          allow for passage through bone
Bones of the Skeleton

Broken down into two groups
        - Axial – 80 bones of the vertebral axis
         -   Appendicular – 126 bones of the appendages & girdles

Skull – separated into 14 facial bones and 8 cranial bones (plus hyoid and 6 ossicles)

         -   sutures: immovable joints between
                  o fontanels:
         -   sinuses: air-filled chambers

Vertebral Column – 30-32 bones that support the trunk and protect

         -   7 cervical,12 thoracic, 5 lumbar, 5 (fused) sacrum, 2 -3 coccyx
         -   Thoracic and lumbar curvature
         -   Vertebrae structure

Thoracic cage – 12 pairs of ribs, sternum

         -   true vs false ribs
         -   Connected to sternum by costal cartilages

Pectoral Girdle and Upper limb
         -   scapula, clavicle, humerus, ulna, radius, carpals, metacarpals, phalanges
             (phalanx)
         -   Gleno-humeral (shoulder joint) – ball in socket


Pelvic Girdle and Lower limb
         -   os coxae, femur, tibia, fibula, tarsals, metatarsals, phalanges (phalanx)


Joints (articulations)

•Point of contact between two bones
•Joints structure determines how it functions
•The closer the fit at the point of contact the stronger the joint.
•Joints are the weakest points of the skeleton
Types of joints
       •Synarthroses – immovable joints
      •Amphiarthroses – slightly immovable joints


      •Diarthroses – freely immovable joints
        -   Synovial joints:
               o Capsule, synovial fluid, ligaments


               o Menisci, fat pads, bursae

STABILITY OF SYNOVIAL JOINTS:

   1. Shape of articular surface
   2. Number and position of ligaments
   3. Muscle tone

ANGULAR MOVEMENTS: Increase or decrease the angle between two adjoining bones
      - Result of the action of muscles around the specific joint

FLEXION:
      *DORSIFLE XION -

      *PLANTA R FLE XION -

EXTENSION:
      *HYPERE XTE NSION -

ABDUCTION:

ADDUCTION:

CIRCUMDUCTION:

ROTATION:

Special Movements:

PRONATION:

SUPINATION: Palms up

ELEVATION:

DEPRESSION:

INVERSION: Sole turns
EVERSION: Sole turns

OPPOSITION: Thumb touches tips of other fingers




Shapes of Synovial Joints:

1. gliding (plane) joints

       - between

2. Hinge joints

3. Pivot joints

4. Ellipsoidal Joints: one articular surface concave and the other convex.

5. Saddle:

6. Spheroid (ball & socket):


FACTORS WHICH AFFECT BONE REMODELING

1. Stress: Bone grows in response to prolonged heavy load

         A. gravitational forces:

         B. functional forces:

             - regular exercise can alter the form of the skeleton


2. Hormones : negative feedback mechanisms
                A. PTH (parathormone)

                   B. Calcitonin

3. The age of the individual:
        - osteopenia to osteoporosis
         3 factors to decrease risk of osteoporosis: (box 7-2)
                   1.
                   2.
                   3.
4. Rates of Mineral absorption (Ca and P)

5. Genetic and Environmental factors:



Examination of the Skeletal System involves:
   1. Observation of any limitation of movement or stiffness
   2. Understanding of the distribution of joint involvement and inflammation
   3. Are there any sounds associated to joint movement
   4. Observation of any abnormal bone deposits
   5. Observation of abnormal posture


Conditions of Clinical Significance for Bone Disorders:

A. Congenital disorders (present at birth)

         -     Marfan’s Syndrome
         -     Cleft palate

B. Infection

         -     Osteomyelitis
         -     Paget’s Disease (osteitis deformans)

C. Nutritional

         -     Ricket’s
         -     Scurvy
D. Trauma

         -     Bone Bruise
         -     Fractures:
               1. simple:

               2. compound:

               -   Comminuted, depressed, impacted, transverse, spiral, Colles’, greenstick,
                   epiphaseal, Pott’s, displaced vs nondispalced


         Healing process:
                    1. bleeding occurs froming a hematoma, formation of a fibrocartilaginous
                       callus, formation of a bony callus within external callus, bone
                       remodeling (from 3 weeks to over a year)


E. Secondary disorders

            -    Gigantism
            -    Pituitary growth failure



Conditions of Clinical Significance for Joint Disorders:

A. Inflammation
       - Bursitis
       - Rheumatism and Arthritis
                - Rheumatic arthritis:


                - Prosthetic joints


B. Degenerative – Osteoarthritis


C. Infection – Rheumatic fever


D. Metabolic – Gout


E. Trauma
       - Dislocations and subluxations


       - Strains and sprains


Arthroscopic Surgery
       – Use of optic fibers within a surgical tube to explore a joint without major surgery.
       – An additional scope may be used to repair damage at the same time

								
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