Chapter 7
Skeletal Tissue
Types of Bone
Bones
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Long Bone
Short Bone
Flat Bone
Irregular Bone
Long Bone
• Identified by extended longitudinal axes
and uniquely shaped articular end
• Femur and humorous are examples
Parts of Long Bone
• Diaphysis: Main shaft or portion. Hollow.
Composed of compact bone
• Epiphysis: End of long bone. Gives
stability to joints. Composed of spongy
bone
• Articular cartilage: Hyaline cartilage that
covers epiphysis
Parts of Long Bone
• Periosteum: White fibrous membrane that
covers bone except at joint surfaces
• Medullary (marrow) cavity: Tube like
hollow space in the diaphysis of long
bones. Filled with fat rich connective tissue
called yellow marrow
• Endosteum: Thin epithelial membrane that
line medullary cavity
Short Bone
• Usually described as cube or box shape
• Includes carpals (wrist) and tarsals
(ankles)
Flat Bones
• Generally broad and thin
• Flattened and often curved surface
• Include some skull bones, scapula
(shoulder blade), ribs and sternum (breast
bone)
Irregular Bones
• Clustered in groups
• Have variety of sizes and shape
• Include vertical bone that forms spine and
some facial bones
• Bones that appear singly instead of in
groups are called sesamoid
• Kneecap or patella
Bone Tissue
Composition of Bone
• Osseous tissue, connective tissue
• Extracellular components are hard and
calcified
• Matrix is subdivided into two chemical
components: Inorganic salts (2/3) and
organic matrix (1/3)
Inorganic Salts
• Hardness of bone result from deposits of
chemical crystals of calcium and
phosphate called hydroxyapatite (85% of
inorganic matrix)
• 10% of calcium carbonate and other
minerals. (magnesium, sodium, sulfate
and fluoride)
• Harmful elements also mix with bone
matrix. (radioactive elements such as
radium, stronium-90, uranium and
plutonium)
Organic matrix
• Composite of collagenous and mixture of
protein and polysaccharides called ground
substance
• Ground substance provide support and
adhesion between cellular and fibrous
elements
• Chondroitin Sulfate helps cartilage remain
compressible and elastic
• Glucosamine is an amino sugar important
in cartilage formation, maintenance and
repair
Chondroitin Sulfate and Glucosamine
• dietary supplements that facilitate healing
and reduce pain of osteoarthritis
• Naturally found in body and are important
constitutes of ground substance
• Commercially, Chondroitin Sulfate is
harvested from sharks and cattle tracheas
• Glucosamine harvested from shells of
shrimp, lobster and crab
Bone Marrow
• Specialized type of soft, diffuse connective
tissue called myeloid tissue
• Site for production of blood cells
• Found in medullary cavity of long bones
• Two types Red and Yellow
Red Bone Marrow
• Production of blood cells
• In an infant or child nearly all bones
contain red marrow
• In adult in ribs, bodies of vertebrae, ends
of humerus, pelvis, and femur.
Yellow Bone Marrow
• As aging continues red bone marrow is
replaced by yellow bone marrow
• Marrow cells have become saturated with
fat
• Inactive in blood cell production
• Advancing age become almost rustcolored, less fatty and gelatinous
• During times of decreased blood supply
yellow marrow may convert back to red
A small amount of bone marrow is removed during a bone
marrow aspiration. The procedure is uncomfortable, but can
be tolerated by both children and adults. The marrow can be
studied to determine the cause of anemia, the presence of
leukemia or other malignancy, or the presence of some
"storage diseases" in which abnormal metabolic products are
stored in certain bone marrow cells.
Bone Marrow Transplant
• While you are awake and pain-free (using local
anesthesia), bone marrow is removed from the top of
the hip bone (iliac crest). The bone marrow is filtered,
treated, and transplanted immediately. Other times it's
frozen and stored for later use.
Bone Marrow Transport
• The bone marrow is then transfused through a vein (IV
line). It naturally transports itself back into the intended
bone cavities, where it grows quickly to replace the old
bone marrow.
Regulation of
Blood Calcium
Levels
Blood Calcium Levels
• Skeletal system serves as storehouse for
about 98% of body calcium reserves
• Calcium moves into and out of blood
during continuous remodeling of bone
• Osteoblast deposit bone and remove
calcium from blood
• osteoclast breakdown and reabsorb bone,
releasing calcium back into the blood
Blood Calcium Levels
• Needed for normal blood clotting
• Transmission of nerve impulses
• Maintenance of skeletal and cardiac
muscle contraction
• Involve secretion of two hormones:
parathyroid hormone and calcitonin
Parathyroid Hormone
• Most critical factor in blood calcium
homeostasis
• When blood calcium levels are lower than
set point in parathyroid gland, osteoclasts
are initiated to start break down of bone
matrix
• If levels are high osteoclasts activity is
surpressed
• Also increases renal absorption of calcium
from urine
• Stimulates vitamin D synthesis
Calcitonin
• Produced in response to high calcium
levels
• Stimulates bone deposition by osteoblasts
• Inhibits osteoclast activity
• Nasal spray containing calcitonin
(Miacalcin) can be used to treat post
menopausal osteoporosis
Development of
Bone
Development of Bone
• Before birth bones consist of cartilage and
fibrous structures
• Replaced with calcified bone matrix
• Bone formation is on going process known
as osteogenesis
Intramembranous Ossification
• Formation of bone on, or in, fibrous
connective tissue
• Process used to make flat bones such as
the mandible and flat bones of the skull.
• Clusters of osteoblasts are called centers
of ossification
• They secrete matrix material and
collagenous fibrils
Intramembranous Ossification
• Calcification of bone continues
• Trabeculae appear to form spongy bone
• Uses appositional growth
Endochondral Ossification
• Bones are formed from cartilage models
• Cartilage model develops periosteum that
enlarges and produces a ring or collar
Endochondral Ossification
• Bone is deposited by
osteoblast and
cartilage begins to
calcify
•Primary ossification
center
•Blood vessels enter
Endochondral Ossification
• Secondary
ossifiaction center
• Bone growth
proceeds toward
diaphysis
•Epiphyseal
plate allow
bone to
increase in
length
•Ossification
near
diaphysis
follows
Repair of Bone
Fracture
http://www.youtube.com/watch?v=qVougiCEgH8
Bone repair
Bone Repair of Fracture
1
Fracture takes place,
damaging bone and blood
vessels
2
•Pooling of blood result in blood
clot (fracture hematoma)
•Develops fibrin mesh and
transforms into mass of
granulation tissue
•Contains inflammatory cells,
fibroblast, bone and cartilage
forming cells, and new capillaries
Bone Repair of Fracture
3
•Islands of cartilaginous
tissue (procallus) form
•Helps anchor ends of
fractured bone more firmly
•Osteoblasts form bony
callus collars broken ends
4
•Repaired bone
Mechanism of
Disease
Osteosarcoma
• Most common malignant
bone tumor
• Often fatal
• Males 10-25 yrs
• Common site: tibia
humerus and femur
• 10% metastasize to lung
• Surgery, followed by
chemo
Chondrosarcoma
• Malignant tumor of hyaline
cartilage
• Arises from chondroblasts
• Occurs more frequently in
middle age
• Common sites: Humerus,
femur, scapula, spine, pelvis
and ribs
• Large excission or amputation
• Chemo has not proven
effective
Osteoporosis
http://www.youtube.com/watch?v=vcsPjThU-5Q&feature=fvw
Rickets and Osteomalacia
• caused by insufficient levels of vitamin D
in the body
• rickets is the name used when it occurs in
children whereas osteomalacia is the term
used for adults.
• Symptoms: Bone pain, muscle weakness
and possible joint inflammation and pain
• Treatment: daily supplements of vitamin D
and calcium or single injection vitamin D,
in the form of calciferol (vitamin D2).
Osteomyelitis
• Bacterial bone infection
• Most common is from staph
• bacteria can settle on a small section of
bone, and multiply to cause infection.
• Treatment include antibiotics and or
surgery