BIO210Y5 Chapter Notes - Chapter 7: Bone, Hyaline Cartilage, Appendicular Skeleton

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18 Feb 2016
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Osseous Tissue Notes
4.13 – BONE PROVIDES A STRONG FRAMEWORK FOR THE BODY
Bone, or osseous tissue, contains a small volume of ground substance about two thirds of the bone
matrix consists of a mixture of calcium salts (calcium phosphate and calcium carbonate)
The rest of the matrix is dominated by collagen fibers
In bone, the presence of the minerals surrounding the collagen fibers produces a strong, somewhat
flexible combination that is highly resistant to shattering
A typical long bone is hollow with its walls containing two different types of bone
oThe weight bearing outer layer consists of well organized compact bone
oA finer network of spongy bone lines the internal cavity
In compact bone, the matrix is organized in concentric layers around branches of blood vessels within the
bone
Compact bone also has a superficial layer of bone that was deposited during appositional growth of the
bone (matrix is solid and calcified so interstitial growth cannot occur)
Unlike cartilage, bone is highly vascular large vessels outside the bones are connected to smaller
vessels that supply the areas of compact bone and the soft tissues that fill the interior cavity
Characteristic Cartilage Bone
Cells Chondrocytes in lacunae Osteocytes in lacunae
Ground Substance Chondroitin sulfate (in proteoglycan) and water A small volume of liquid surrounding
insoluble crystals of calcium salts
Fibers Collagen, elastic, and reticular fibers in varying
proportions Collagen fibers predominate
Vascularity None Extensive
Covering Perichondrium (two layers) Periosteum (two layers)
Strength Limited: bends easily, but hard to break Strong: resists distortion until breaking
point
Except in joint cavities, where they are covered by a layer of hyaline cartilage, bone surfaces are
sheathed by a periosteum
oThe fibrous layer attaches a bone to surrounding tissues and to associated tendons and
ligaments
oThe cellular layer functions in appositional bone growth and participates in repairs after an injury
Lacunae in the matrix contain osteocytes lacunae are typically organized around blood vessels that
branch through the bony matrix (layers of matrix separate the lacunae)
Canaliculi are fine passageways that form a branching network for the exchange of materials between
blood vessels and osteocytes – important because diffusion cannot occur through calcified bone
A central canal at the center of an osteon contains the blood vessels that provide oxygen and nutrients to
the osteocytes
5.11 – THE INTEGUMENT RESPONDS TO CIRCULATING HORMONES AND HAS ENDOCRINE FUNCTIONS
THAT ARE STIMULATED BY ULTRAVIOLET RADIATION
Circulating Hormones
Most of the communication between the skin and the rest of the body is chemical communication, as the
specialized cells of the integument respond to levels of circulating hormones
oSteroid hormones called glucocorticoids are released during times of stress loosed the
connections between keratinocytes and reduce the effectiveness of the epidermis as a barrier to
infection
oThyroid hormones maintain normal blood flow to the subpapillary plexus
oSex hormones stimulate epidermal cell divisions, increasing epidermal thickness and
accelerating wound repair, also increase the number of dendritic cells that defend against cancer
cells and pathogens
oGrowth hormone (GH) stimulates fibroblast activity and collagen synthesis, also stimulates basal
cell divisions, thickens the epidermis, and promotes wound repair through intermediary
compounds
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oGrowth factors stimulate cell growth and cell division
Epidermal growth factor (EGF) promotes basal cell division, accelerates keratin
production, stimulates epidermal development and repair, stimulates synthetic activity
Vitamin D3 Production
Limited exposure to sunlight is beneficial because UV radiation plays a vital role in the synthesis of an
important vitamin: cholecalciferol or vitamin D3
Sources of Vitamin D3
Sunlight: when exposed to UV radiation, epidermal
cells in the stratum spinosum and stratum basale
convert a cholesterol-related steroid into
cholecalciferol – this vitamin then diffuses across the
basement membrane and enters capillaries of the
subpapillary plexus
Diet: cholecalciferol can be obtained from the diet, but
few foods contain it other than fish, fish oils, and
shellfish
The liver then converts cholecalciferol into an
intermediary product used by the kidneys to
synthesize the hormone calcitriol
Calcitriol is required for stimulating normal absorption
of calcium and phosphorus in the small intestine; an
inadequate supply of calcitriol leads to impaired bone
growth and maintenance
Rickets is a condition that results in flexible, poorly mineralized bones rickets develops in a growing
child whose skin is not exposed to sunlight, and whose diet does not include a source of cholecalciferol
6.1 – THE SKELETAL SYSTEM IS MADE UP OF THE AXIAL AND APPENDICULAR DIVISIONS
The adult skeleton includes about 206 separate bones and a number of associated cartilagesthis body
system is divided into the axial skeleton and the appendicular skeleton
oThe axial skeleton (80 bones) consists of the bones of the skull, thorax, and vertebral column
oThe appendicular skeleton (126 bones) includes the bones of the limbs and the pectoral and
pelvic girdles that attach the limbs to the axial skeleton
Functions of the skeletal system include…
oSupport: provides structural support for the entire body
oStores minerals and lipids: calcium salts in bone are a valuable mineral reserve that maintains
normal concentrations of calcium and phosphate ions in blood; bones contain adipose tissue,
which stores lipids as energy reserves
oProduce blood cells: red blood cells, white blood cells, and platelets are produced in the red
bone marrow
oProtection: surrounds the delicate tissues and organs
oLeverage: many bones of the skeleton function as levers that can change the magnitude and
direction of the forces skeletal muscles generate
6.2 – BONES ARE CLASSIFIED ACCORDING TO SHAPE AND STRUCTURE AND HAVE VARIED SURFACE
MARKINGS
The major bones in a typical human adult can be divided into 6 categories based on their shape
oFlat bones have thin, roughly parallel surfaces; they protect underlying soft tissues and have an
extensive surface area for the attachment of skeletal muscles (ex. parietal bone)
oSutural bones are small, flat, irregularly shaped bones between the flat bones of the skull
oLong bones are elongated and slender (ex. humerus)
oIrregular bones have complex shapes with short, flat, notched, or ridges surfaces (ex. vertebra)
oSesamoid bones are generally small, flat, and shaped somewhat like a sesame seed; they
develop inside tendons and are most commonly located near joints at the knees, the hands, and
the feet (ex. patella)
oShort bones are small and boxy (ex. carpal bones)
Each bone in the body has characteristic surface markings related to its particular function
Bone Surface Markings
Skull 1. A canal or meatus is a large passageway through a bone.
2. A process is any projection or bump.
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