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Skeleton Skeleton


         Mainly supportive
         A living tissue
         Metabolically active
         Cells exchange nutrients in blood, in equilibrium (imaging basis)
         With calcified intercellular subs. (what makes it different)
         Support – other tissues
         Protection – vital organs
         Assist movements – muscle attachment
         Hematopoiesis – bone marrow blood formation
         Storage – mineral deposits.

Know difference!
Axial – skull, hyoid (floater @ base of tongue), vertebrae, ribs, and sternum.
Appendicular – shoulder and pelvic girdles, arms and legs.

Growth and Formation:
        Skeleton begins with cartilage, formed @ end of 3 mo. Fetus
        Growth in child, all directions esp. vertical thru appx. 15-16 yrs.
        Remodeling, reshaping, some end growth thru appx. 21 yrs. (most not vertical
        Bone = protein matrix and salts as a x-stal (a crystal structure) structure:
       A.) Hydroxyapatite (must spell) – Ca carbonate, Ca phosphate
       B.) Primary ions – (P-1), (Ca+2), also (Mg+2), (K+1), (Cl-1 (chloride)), (OH-1)
        Made up of water, protein matrix(collagen), inorganic substances
        Bone develops from osteoblast (cells sit far apart, bone building cells,
        synthesize and secrete collagen fibers needed to build the matrix, as they
        surround themselves w matrix, they become trapped in their secretions and
        become osteocytes) secrete protein matrix for ossification.
         Salts (minerals) ppt’d; mature bone cell = osteocytes. Deposition bone
        regulated by bone stress(muscle activity and gravity) and injury.
        Osteoclast – (huge cells derived from the fusion of as many as 50 monocytes
        and are concentrated in the endosteum. Release lysosomal enzymes and acids
        that digest proteins and mineral components of matrix. Responsible for the
        reabsorption of bone tissue) for resorption / deossify bone’ type of osteocytes
        Ossification : processes which trigger calcification (know diff b/t 2)
        Intramembranous – forms facial and cranial bones / spongy or cancellous
        (cranium cartilage, membrane to bone, refers to the formation of bone directly
        on or within loose fibrous connective tissue membranes)
        Endocondrial - forms most other bones (femur, radius, tibia end fibula,
        cartilage to bone, refers to the formation with hyaline cartilage) At growth site
        = end plates(epiphyseal plate?), chondrocytes move, down blood supply,
        triggers calcification (At the site where bone is going to form, messenchymal
        cells crowd together in the shape of the future bone, and then develop into
        chondroblast. The chondroblast secrete cartilage matrix (collagen and elastin)
         producing a cartilage model consisting of hyaline cartilage and the blood
         brings in calcium salts. The chondroblast then turn into chondrocytes once they
         become deeply buried in the cartilage matrix. Chondrocytes age, enlarge, burst
         and die, which increases the pH of the tissue. The change in pH is the signal for
         the blood to bring in osteoblast (which produce collagen) and bring in more
         calcium salts. Osteoblasts turn into osteocytes and continue to make collagen.
         Osteoclast breakdown and remove old bone and calcium salts. Osteoblasts
         enter the tissue and start the process all over again for constant reproduction.

Typical long bone:

Physiology Growth:
        Diameter Increase: osteoclast destroy, widen, osteoblast lay down
        hydroxyapatite… dynamic balance
        Length increase: osteoblast in diaphysis invades epiphysis cartilage.
        Hydroxyapatite laid down, as cartilage grows away from diaphysis, pushes
        epiphysis ahead.
Growth: hormone controlled; inc. somatotropin (growth hormone coming from pituitary)
        Parathormone (PTH) – increase osteoclastic activity, increase Ca++ removal,
        increase serum Ca++ levels
        Thyrocalcitonin – (from thyroid) increase osteoblastic activity, decrease Ca++
        removal, decrease serum Ca++ levels
        Growth Hormone = Somatotropin – in child hood an increased supply =
        dwarfism, and in increased supply = gigantism. In adults an increased supply =
        acromegaly (look at face hands and feet)
         Calcium required for bone and vitamin D required for absorption of calcium

Histology X-section (cross section) of bone:
        Periosteum – tough outer covering most bones
        Two types of bone: 1) Compact – dense, strong w/ lamellae (concentric rings or
        layers mineral deposits around Haversian canals. 2) Cancellous – spongy w/
        lamellae far apart (RBM in lamellae)
        Haversian system – narrow systems, channels provide nutrients with in the
        A.) Haversian canals – with blood vessels, (lamellae surrounded)
          B.) Lacunae – small cavities / spaces between lamellae layers, each with an
         osteocytes, active for bone formation. Connected by canaliculi to Haversian for
         fluid exchange
         Medullary cavity: with bone marrow. Red marrow – primary in cancellous
         bone spaces. Makes both red and white blood cells. Yellow marrow – primary
         fat cells in shafts of bone
         Osteoclast: (larger than osteoblast): at bone breakdown region

Pathphysiology / Terminology
1.) Osteomyelitis – inflammatory infectious disease with focal spots of necrosis, most
often its bacterial. (Local or generalized infection of bone and bone marrow. It is usually
caused by bacteria introduced by trauma or surgery, by direct extension from a nearby
infection, or via the bloodstream. Staphylococci are the most common causative agents)
This warrants emergency study. Also tissue local separation
2.) Primary bone calcium = a.         e.g. osteogenic sarcoma
3.) Bone Metastasis: primary common from prostate, breast, lung, kidney and thyroid
4.) Calcium Deficiency:
     a. Tetany – muscle spasms, disorder due to nerve fiber depolarization (calcium and
potassium) (a condition characterized by cramps, convulsions, twitching of the muscles,
and sharp flexion of the wrist and ankle joints. These symptoms are sometimes
accompanied by attacks of strider. Tetany is a manifestation of an abnormality in
calcium metabolism, which can occur in association with vitamin D deficiency,
hyperparathyroidism, alkalosis, or the ingestion of alkaline salts.) Also weakens cardiac
muscle’ interferes with blood coagulation.
    b.) Calcium exchange between bones and fluids primary by diffusion.
5.) Vitamin D Deficiency does NOT allow calcium absorption, bone uptake
    a.) Rickets – in peds, bones fail to ossify (condition caused by deficiency of vitamin
D, seen primarily in infancy and childhood and characterized by abnormal bone
    b.) Osteomalacia: in adults (an abnormal condition of lamellar bone, characterized
by loss of calcification of the matrix and resulting in softening of the bone. Its
accompanied by weakness, fracture, pain, anorexia, and weight loss. The condition is the
result of an inadequate amount of phosphorus and calcium available in the blood for
mineralization of the bones. This deficiency may be caused by a diet lacking these
minerals or vitamin D; by a lack of exposure to sunlight and hence an inability to
synthesize vitamin D ;or by a metabolic disorder causing malabsorption of minerals.
6.) Fractures: breaks in bone or cartilage
           Compound – break thru skin
           Simple – no skin penetration
           Incomplete – not thru the entire bone
           Transverse – at rt. Angles to long axis of the bone
           Oblique – slanting direction, or any variation from the perpendicular of
           Longitudinal – pertaining to measurement in the direction of the long axis
           Spiral – oblique
        Comminuted – crushed broken / splintered pieces
        Depressed –
        Compression – (like in vertebrae)
        Overriding –
        Greenstick – part bent and broken. (in very young peds)
           (Greenstick fracture occurs because the bone is not as brittle as it would be in
            an adult, and thus does not completely fracture, but rather exhibits bowing
            with out complete disruption of the bone’s cortex.
    Healing fractures: stages -
        Hematoma – blood clot at site of injury
        Clot – now new capillaries being developed and osteoblast move in
        Callus – large ass of loosely deposited bone in that area
        Ossification and calcification –

Bone Classifications:
        Projection – process
        Depression – fossa
        Crest –
        Head –
        Fissure –
        Foramen –
        Meatus –
        Canal –

Divisions of the skeleton –
Axial: bones along midline/axis of body
           Skull – facial (14)
           Cranial (8) – 1 frontal, 2 parietal, 1 occipital, 2 temporal, 1 ethmoid, 1 sphenoid.
           Sphenoid – butterfly shape’ skull floor with sella turcicia prt of the orbit and
           lateral skull.
             (The sphenoid is a bone situated at the base of the skull in front of the
      temporals and basilar part of the occipital, it somewhat resembles a butterfly with
      its wings extended. It’s hollowed out in its interior to form two large cavities, the
      sphenoidal air sinuses, which are separated from each other by a septum.)
           Ethmoid – nasal cavity roof’ part of medial orbits with cribiform plate.
             (The ethmoid in the skill that separates the nasal cavity from the brain. As
such, it is located at the roof of the nose, between the two orbits. The cubical bone is
lightweight due to spongy construction. It’s very delicate and easily injured by a sharp
upward blow toe the nose, such as a person might suffer by striking an automobile
dashboard in a collision. The force of a blow can drive bone fragments through the
cribiform plate into the meninges or brain tissue. Such injuries are often evidenced by
leakage of cerebrospinal fluid into the nasal cavity, and may be followed from the nasal
cavity into the brain. Blows to the head can also shear off the olfactory nerves that pass
through the ethmoid bone and cause anosmia, an irreversible loss of the sense of smell
and a great reduction in the sense of taste (most of which depends on smell). This not
only deprives life some of its pleasure, but can be dangerous, as when a person fails to
smell smoke, gas or spoiled food.)
          Sella turcicia – a saddle shaped depression in the sphenoid bone at the base of
          the skull
          Cribiform plate – Cribiform plate of ethmoid bone is received into the
          ethmoidal notch of the frontal bone and roofs in the nasal cavities
          Vertebral column – (26) C-7 {Atlas (1) + Axis (2)} T-12, L-5, S-51, Cx = 4
           1 ( means fused to bone)
             Cervical vertebra (7) The first one is the atlas, and the second one is the
             Thoracic vertebra (12)
             Lumbar vertebra (5)
          Ribs – (24) 12 pair: First pair true-directly attached, second five pairs false with
          last 2 pairs floating.
          Sternum – breast plate = manubrium with S.S.N.(Sopra sternal notch), body
          (gladioulus) xiphoid process
          Hyoid - at the base of the tongue, floating
Appendicular: bones associated with appendages
          Upper extremity: includes pectoral/shoulder girdle = scapula (2), clavicle (2),
          humerus (2), radius (2) ulna (2) = arm
          hands = Carpals – (16), metacarpals (10), phalanges (28)
          Lower extremity – includes pelvic girdle and femur (2), tibia (2), fibula (2)
             Feet = tarsals – (14), metatarsals (10 phalanges (28)
             Pelvic girdle :
                     Innominate bones: os(sa) coxae =
                     Ilium, ischium, pubis = hip bones
             Sacrum and coccyx + hipbones = pelvis
          Vertebral Column:
             Kyphosis – exaggerated posterior curve thoracic (don’t call hunch back)
             Lordosis – exaggerated anterior curve lumbar (it’s a tail)
             Scoliosis – abnormal lateral curve and rotation of the spine
             Herniated disc – rupture outer cover due to trauma with inner core
Articular System:
Joints / Articulations: Classification:
             Three groups:
          Synarthroses – no movement (fibrous)
            o Suture: cranial, synchondroses – ends with ligaments a joint in which
                there is slight movement between bones that are held together by cartilage
                bones that are held together by cartilage, e.g. between the ribs and the
          Amphiarthroses – slightly moveable
            o Symphyses – symphysis pubis (symphyses - slightly movable joints, such
                as the junction of the bones making up the front of the pelvis)
            o Syndesmoses – costal cartilage (Syndesmoses – joint of fibrous connective
                tissue, and immovable joint in which the bones are held firmly by fibrous
              tissue, but are not very close together, e.g. at the lower ends of the tibia
              and fibula
         Diarthroses – freely movable
          o Synovial joint anatomy –
                   Synovial fluid – forms a thing film, and lines. Reduces friction,
                      supply’s nutrients, and removes waste
                   Synovial capsule -
                   Articular cartilage – at the ends of bones
                   Re: cartilage types – 1. fibrous – articular
                                             2. elastic cartilage – ears
                                             3. Hyaline – articular, trachea, bronchi
                   Synovial membrane – tissue which has cells that produce fluid.
                      Pathology may cause an over production of S.F.
                   Articular disc – (vertebral)
                   Ligaments
                   Articular muscles (tendon)
          o Types of synovial joints:
                   Ball and Socket – ex.- femur head, process fits into
                   Hinge (refer to knee or elbow figures)
                   Pivot – ex – C1 and C2 (atlas and axis)
                   Condyloid – ex- wrist
                   Saddle – ex -thumb
                   Gliding – any intervertabral joints
          o Synovial Joints = (refer to text)
          o Bursae – closed sacs with synovial membrane lining (pad like sacs
              situated to reduce friction, cushion movement) in close proximity joints
              and usually associated with spaces between connective tissue.
          o Joint Disorders:
                   Bursitis – inflammation of synovial bursa
                   Arthritis – general term used for inflammation of joints (any joint)
                           Rheumatoid - ? cause with systemic effects (systemic –
                              autoimmune/your own body)
                           Inflammation  fusion bone joints (visible in hands)
                           Gouty – metabolic disorder purine metabolism with
                              excretion not getting rid of uric acid deposits in the joints
                           Degenerative – wear and tear with old age to articular
                              surfaces, joints adhere and increased pain
                           Rheumatic fever – synovial membrane inflammation
                           Primary fibrosis – lower back inflammation of fibrous
                              connective joint tissue
                           Tenosynovitis – tendon sheath inflammation, decreased
                              joint movement

*internal damage to knee joint most common, tear of medial semilunar cartilage, surgical
removal necessary

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