Title: Anatomy and Physiology
1Anatomy and Physiology
- Chapter 7
- Skeletal System
- Part I
2The Skeletal System
- Individual bones are the organs of the skeletal
system - A bone contains very active tissues
3Functions 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
4Bone Structure
- Bone structure reflects its function
5Parts 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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8- 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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10- 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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12Microscopic 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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15Bone Growth and Development
- Intramembranous bones
- Endochondral bones
- Homeostasis of bone tissue
- Repair of a bone fracture
Bone growth animation
16Intramembranous 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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19Endochondral 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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23Homeostasis 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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26Repair 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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28Bone Function
- Support and protection
- Body movement
- Blood cell formation
- Storage of inorganic salts
- Passageways for blood vessels and nerves
29Support 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
30Body 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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32Blood 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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34- 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.
36Bone 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
39Storage 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
41Osteoporosis
- 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
46Passageways for Nerves and Blood Vessels