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Anatomy and Physiology

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Individual bones are the organs of the skeletal system. A bone ... Endochondral bones develop first as hyaline cartilage, which later is replaced by bone tissue ... – PowerPoint PPT presentation

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Title: Anatomy and Physiology


1
Anatomy and Physiology
  • Chapter 7
  • Skeletal System
  • Part I

2
The Skeletal System
  • Individual bones are the organs of the skeletal
    system
  • A bone contains very active tissues

3
Functions of the Skeletal System
  • Provide points of attachment for muscles
  • Protect and support softer tissues
  • House blood-producing cells
  • Store inorganic salts
  • Contain passageways for blood vessels and nerves

4
Bone Structure
  • Bone structure reflects its function

5
Parts of a Long Bone
  • Epiphyses at each end are covered with articular
    cartilage and articulate (forms a joint) with
    other bones.
  • The shaft of a bone is called diaphysis.
  • Except for the articular cartilage, a bone is
    covered by periosteum (fibrous tissue), which
    also helps to form and repair bone tissue
  • Bony projections, called processes, provide sites
    for ligaments and tendons to attach.

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  • Compact bone has a continuous matrix with no gaps
    and forms the wall of the diaphysis.
  • Spongy bone forms the epiphysis and has irregular
    interconnecting spaces between bony plates that
    reduce the weight of bone
  • Both compact and spongy bone are strong and
    resist bending

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  • The diaphysis contains a medullary cavity, lined
    with a thin layer of cells called endosteum and
    is filled with marrow
  • Grooves and openings provide passageways for
    blood vessels and nerves.

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Microscopic Structure
  • Compact bone contains osteons cemented together
  • Osteons are cylinder-shaped units that include
    bone cells (osteocytes) that surround a central
    canal.
  • Also called Haversian System
  • Osteonic canals contain blood vessels that
    nourish the cells of osteons (includes central
    canal and transverse perforating canals called
    Volkmans canals)

13
  • Diffusion from the surface of the thin, bony
    plates nourishes the cells of spongy bone.
  • The intercellular material of bone tissue is
    largely collagen and inorganic salts.
  • Collagen gives bone its strength and resilience.
  • Inorganic salts make bone hard and resistant to
    crushing.

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Bone Growth and Development
  • Intramembranous bones
  • Endochondral bones
  • Homeostasis of bone tissue
  • Repair of a bone fracture

Bone growth animation
16
Intramembranous Bones
  • Intramembranous bones develop from sheet-like
    layers of connective tissue
  • Osteoblasts within the membranous layers form
    bone tissue
  • Osteoblasts enlarge and differentiate
  • Deposit bony matrix around themselves
  • Form in all directions

17
  • Mature bone cells are called osteocytes and are
    completely surrounded by extracellular matrix
  • Intramembranous bones include those of the skull

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Endochondral Bones
  • Most bones of the skeleton
  • Endochondral bones develop first as hyaline
    cartilage, which later is replaced by bone tissue

20
  • The primary ossification centers appear in the
    diaphysis, while secondary ossification centers
    appear in the epiphyses
  • An epiphyseal disk remains between the primary
    and secondary ossification centers.

21
  • The epiphyseal disks are responsible for
    lengthening.
  • Layers of young cells are undergoing mitosis,
    producing new cells
  • Long bones continue to lengthen until the
    epiphyseal disks ossify
  • Growth in thickness is due to intramembranous
    ossification beneath the periosteum.

Video clip Bone growth in width
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Homeostasis of Bone Tissue
  • Osteoclasts and osteoblasts continually remodel
    bone
  • Osteoclasts are multinucleated cells that break
    down calcified matrix
  • Secrete acids to dissolve inorganic matrix
  • Lysosomal enzymes digest organic components
  • Osteoblasts deposit new bone tissue in place of
    calcified cartilage.

24
  • The total mass of bone remains nearly constant.
  • Hormones that regulate blood calcium help control
    help these opposing processes of resorption and
    deposition of matrix
  • 3-5 of bone calcium is exchanged each year.

Cancer of the prostate gland can have the
opposite effect if the cancer cells reach the
bone marrow (advanced stages). These cells
stimulate osteoblast activity which promotes
formation of new bone on the surface of the bony
plates.
In bone cancers, abnormally active osteoclasts
destroy bone tissue.
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Repair of a Bone Fracture
Video Body Story Broken Bone
  • Blood escapes from ruptured blood vessels and
    forms a hematoma (clot)
  • Spongy bone forms in regions close to developing
    vessels and fibrocartilage forms in more distant
    regions.
  • A bony callus replaces fibrocartilage
  • Osteoclasts remove excess bony tissue, restoring
    new bone structure much like the original.

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Bone Function
  • Support and protection
  • Body movement
  • Blood cell formation
  • Storage of inorganic salts
  • Passageways for blood vessels and nerves

29
Support and Protection
  • Bones shape and form body structures.
  • Bones support and protect softer, underlying
    tissues
  • Examples the skull protects the eyes, ears and
    brain
  • The rib cage and shoulder girdle protects the
    heart and lungs
  • The pelvic girdle protects the lower abdominal
    and internal reproductive organs

30
Body Movement
  • Bones and muscles function together as levers
  • Ligament a cord or sheet of connective tissue
    binding two or more bones at a joint
  • Tendon a cordlike bundle or bandlike mass of
    white fibrous connective tissue that connects a
    muscle to a bone
  • A lever consists of a rod, a pivot (fulcrum), a
    movable weight (resistance), and a force that
    supplies energy.

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Blood Cell Formation
  • At different ages, hematopoiesis (blood cell
    formation) occurs in the yolk sac, liver, spleen,
    and red bone marrow.
  • Marrow is a soft, netlike mass of connective
    tissue within the medullary cavities of long
    bones, in the irregular spaces of spongy bone,
    and in the larger osteonic canals of compact bone.

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  • Red marrow produces red blood cells
    (erythrocytes), white blood cells (leukocytes),
    and blood platelets (thrombocytes).
  • The red color of red marrow comes from
    hemoglobin, an oxygen-carrying pigment in blood.
  • In adults, primarily found in the spongy bone of
    the skull, ribs, sternum, clavicles, vertebrae,
    and hip bones

35
  • Yellow marrow stores fat.
  • With age, it replaces much of the red marrow that
    occupies the cavities of most bones.
  • Can become red marrow if the body needs blood.

36
Bone Marrow Transplant
  • Used to correct damage from x-rays, certain
    drugs, cancer (leukemia), sickle cell disease,
    and other blood disorders.
  • Donor and recipient cells must have matching
    pattern of surface molecules

37
  • During the procedure a hollow needle and syringe
    remove normal red marrow cells from the spongy
    bone of a matching donor.
  • Donor cells are injected into the blood stream of
    recipient whos own marrow has been destroyed
    with radiation or chemotherapy

38
  • Donor cells lodge in spaces that red marrow
    normally inhabits and replaces the damaged
    tissue.
  • 15 of patients die from infection, transplant
    rejection or graft vs. host disease
  • Alternative new procedures include coaxing blood
    forming cells / stem cells to leave the marrow
    and enter bloodstream where they are harvested or
    obtaining stem cells from umbilical cord of a
    newborn.
  • Both alternatives are safer and less painful for
    donor

39
Storage of Inorganic Salts
  • The intercellular material of bone tissue
    contains large quantities of calcium phosphate.
  • When blood calcium is low, parathyroid hormone
    stimulates osteoclasts to break down bone.
  • Releases calcium salts from the extracellular
    matix into the blood
  • Maintaining sufficient blood calcium levels is
    important in muscle contraction, nervous impulse
    conduction, and blood clotting

40
  • When blood calcium is high, osteoblasts,
    stimulated by calcitonin from the thyroid gland,
    build bone.
  • Store excess calcium in the matrix.
  • Bone stores small amounts of magnesium, sodium,
    potassium, and carbonate ions.
  • Bone can also accumulate certain harmful metallic
    elements such as lead, radium, or strontium

41
Osteoporosis
  • The skeletal system loses bone volume and mineral
    content
  • Affected bones develop spaces and canals that
    enlarge and fill with fibrous and fatty tissues.

42
  • Bones easily fracture because they are no longer
    able to support body weight.
  • Femur or hip fractures, collapse of sections of
    backbone
  • Associated with aging (over 45yrs) and most
    common in light-skinned females past menopause.
  • Factors that increase risk are low intake of
    dietary calcium, lack of physical exercise,
    decrease in blood estrogen concentration, alcohol
    consumption. Smoking, and genetic inheritance

43
  • To reduce risk of Osteoporosis ingest
    1,000-1,500mg of calcium per day, exercise
    regularly, and post-menopausal women may require
    estrogen replacement therapy.

44
  • Screening Test measure bone mineral density
  • Dual Density X-ray Absorptiometry
  • Advised for people over age 65 or people with
    risk factors (family history, certain types of
    cancers or bleeding disorders, thyroid problems,
    multiple sclerosis, alcoholism)

45
  • Treatments several types of drugs can slow
    progression
  • Biophosphonates re-establish a normal balance of
    osteoclast/osteoblast activity
  • Other drugs mimic hormones that help bone tissue
    retain calcium

46
Passageways for Nerves and Blood Vessels
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