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Side ASide B
Is made of some variety of cartilage tissue, which consists primarily of water. The high water content of cartilage accounts for its resilience, that is, its ability to spring...
The perichondrium acts like a girdle to resist outward expansion when the cartilage is compressed. Additionally, the perichondrium contains the blood vessels from which nutrients diffuse...
Three types of cartilage tissue in the body:
hyalineelasticfibrocartilageAll three types have the same basic components - cells called chondrocytes, encased in small cavities (lacunae) within an extracellular matrix containing...
Which look like frosted glass when freshly exposed, provide support when flexibility and resilience. They are they most abundant skeletal cartilages.1. articular cartilages, which cover...
Look very much like hyaline cartilages, but they contain more stretchy elastic fibers and so are better able to stand up to repeated bending. They are found in only two skeletal locations,...
Are highly compressible and have great tensile strength. The perfect intermediate between hyaline and elastic cartilages, fibrocartilages consis of roughly parallel rows of chondrocytes...
In appositional growth, cartilage-forming cells in the surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue.
In interstitial growth, the lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within. Typicall, cartilage growth ends during adolescence when the...
the axial skeleton forms the long axis of the body and includes the bones of the skull, vertebral column, and rib cage. Generally speaking these bones are most involved in protecting,...
The appendicular skeleton consists of the bones of the upper and lower limbs and the girdles (shoulder bones and hip bones) that attach the limbs to the axial skeleton. Bones of the...
As their name suggests, are considerably longer than they are wide. A long bone has a shaft plus two ends. All limb bones except the patella (kneecap) and the wrist and ankle bones...
Are roughly cube shaped. The bones of the wrist and ankle are examples.
Are a special type of short bone that form in a tendon. They vary in size and number in different individuals. some sesamoid bones clearly act to alter the direction of pull of a tendon....
Are thin, flattened, and usually a bit curved. The sternum (breastbone), scapulae (shoulder blades), ribs, and most skull bones are flat bones.
Have complicated shapes that fit none of the preceding classes. Examples include the vertebrae and the hip bones.
Functions of BonesSupport
Bones provide a framework that supports the body and cradles its soft organs. For example, bones of lower limbs act as pillars to support the body trunk when we stand, and the rib cage...
Functions of BonesProtection
The fused bones of the skull protect the brain. The vertebrae surround the spinal cord, and the rib cage helps protect the vital organs of the thorax.
Functions of BonesMovement
Skeletal muscles, which attach to bones by tendons, use bones as levers to move the body and its parts. As a result, we can walk, grasp objects, and breathe. The design of joints determines...
Functions of BonesMineral and growth factor storage
Bone is a reservoir for minerals, most importantly calcium and phosphate. The stored minerals are released into the bloodstream as needed for distribution to all parts of the body....
Functions of BonesBlood cell formation
Most blood cell formation, or hematopoiesis, occurs in the marror cavities of certain bones.
Functions of BonesTriglyceride (fat) storage
Fat is stored in bone cavities and represents a source of stored energy for the body.
The external surfaces of bones are rarely smooth and featureless. Instead, they display projections, depressions, and openings that serve as sites of muscle, ligament, and tendon attachment,...
Every bone has a dense outer layer that looks smooth and solid to the naked eye. This external layer is compact bone.
Internal to the compact bone is the spongy bone (cancellous bone), a honeycomb of small needle-like or flat pieces called trabeculae ("little beams"). In living bones the open spaces...
Structure of a Typical long BoneDiaphysis
A tubular diaphysis, or shaft, forms the long axis of the bone. It is constructed of a relatively thick collar of compact bone that surroungs a central medullary cavity, or marrow...
Structure of a Typical long BoneEpiphyses
The epiphyses are the bone ends. In many cases, they are more expanded than the diaphysis. Compact bone forms the exterior of epiphyses, and their interior contains spongy bone. The...
Structure of a Typical long BoneMembranes
A third structural feature of long bones is membranes. The external surface of the entire bone except the joint surfaced is coverd by a glistening white, double0layered membrane called...
Large rounded projection; may be roughened
Narrow ridge of bone usually prominent.
Very large, blunt, irregularly shaped process.
Narrow ridge of bone; less prominent than a crest.
Small rounded projection or process.
Raised area on or above a condyle.
Sharp, slender, often pointed projection.
Any bony prominence.
bony expansion carried on a narrow neck.
Smoth, nearly flat articular surface.
Rounded articular projection.
Armlike bar of bone.
Narrow, slitlike opening.
Round or oval opening through a bone.
Indentation at the edge of a structure.
Cavity within a bone, filled with air and lined with mucous membrane.
shallow, basinlike depression in a bone, often serving as an articular surface.
The periosteum is richly supplied with nerve fibers, lymphatic vessels, and blood vessels, which enter the diaphysis via nutriend foramina.
Perforating (Sharpey's) fibers
the periosteum is secured to the underlying bone by perforating (Sharpey's) fibers, tufts of collagen fibers that extend from its fibrous layer into the bone matrix.
Internal bone surfaces are covered with a delicate connective tissue membrane called the endosteum. The endosteum covers the trabeculae of spongy bone and lines the canals that pass...
in flat bones, the spongy bone is called the diploe and the whole arrangement resembles a stiffened sandwich.
hematopoietic tissue, red marrow, is typically found within the trabecular cavities of spongy bone of long bones and in the diploe of flat bones. For this reason, both these cavities...
Essentially, four major cell types populate bone tissue: osteogenic cells, osteoblasts, osteocytes, and osteoclasts. These, like other connective tissue cells, are surrounded by an...
The structural unit of compact bone is called either the osteon or the Haversian system. Each osteon is an elongated cylinder oriented parallel to the long axis of the bone. Functionally,osteons...
An osteon is a group of hollow tubes of bone matrix, one placed outside the next like the growth rings of a tree trunk. Each matrix tube is a lamella, and for this reason compact bone...
Running through the core of each osteon is the central canal, or Haversian canal, containing small blood vessels and nerve fibers that serve the needs of the osteon's cells.
Canals of a second type called perforating canals, or Volkmann's canals, lie at right angles to the long axis of the bone and connect the bone and nerve supply of the periosteum to...
Spider-shaped osteocytes occupy lacunae at the junctions of the lamellae.One function of osteocytes is to maintain the bone matrix. If they die, the surrounding matrix is resorbed....
Hairlike canals called canaliculi connect the lacunae to each other and to the central canal. The canaliculi tie all the osteocytes in an osteon together, permitting nutrients and wastes...
Not all lamellae in compact bone are part of osteons. Lying between intact osteons are incomplete lamellae called interstitial lamellae. They either fill the gaps between forming osteons...
Located just deep to the periosteum and just superficial to the endosteum, extend around the entire circumference of the diaphysis and effectively resist twisting of the long bone.
Bone has bone organic and inorganic components. Its organic components include the cells (osteogenic cells, osteoblasts, osteocytes, and osteoclasts) and osteoid, the organic part...
Bone's exceptional toughess and tensile strength has been the subject of intense research. It now appears that this resilience comes from the presence of sacrificial bonds in or...
The balance of bone tissue consists of inorganic hydroxyapatites, or mineral salts, largely calcium phosphates present in the form of tiny, tightly packed, needle-like crystals...
Ossification and Osteogenesis
Are synonyms meaning the process of bone formation. in embryos this process leads to the formation of the bony skeleton. Later another form of ossification known as bone growth...
when a bone developes from a fibrous membrane, the process is intramembranous ossification, and the bone is called a membrane bone.
bone development by replacing hyaline carilage is called endochondral ossification, and the resulting bone is called a cartilage, or endochondral, bone.
Results in the formation of cranial bones of the skull (frontal, parietal, occipital, and temporal bones) and the clavicles. Most bones formed by this process are flat bones. At about...
Endochondral ossification (definition)
Except for the clavicles, essentially all bones of the skeleton below the base of the skull form by endochondral ossification. Bedinning in the second month of development, this process...
primary ossification center
The formation of a long bone typically begins in the center of the hyaline cartilage shaft at a region called the primary ossification center. First, the perichondrium covering the...
Endochondral Ossification (Process)
1. A bone collar is laid down around the diaphysis of the hyaline cartilage model. Osteoblasts of the newly converted periosteum secrete osteoid against the hyaline cartilage diaphysis,...
secondary ossification centers
Shortly before or after birth, secondary ossification centers appear in one of both epiphyses, and the epiphyses gain bony tissue (typically the large long bones form secondary centers...
resting or quiescent zone
Logitudinal bone growth mimics many of the events of endochondral ossification. The cartilage is relatively inactive on the side of the epiphyseal plate facing the epiphysis, a region...
proliferation or growth zone
But the epiphyseal plate cartilage abuting the diaphysis organizes into a pattern that allows fastm efficient growth. The cartilage cells here form tall columns, like coins in a stack....
Meanwhile, the older chondrozytes in the stack, which are closer to the diaphysis (hypertrophic zone), hypertrophy, and their lacunae erode and enlarge, leaving large interconnecting...
subsequently, the surrounding cartilage matrix calcifies and these chondrocytes die and deteriorate, producing the calcification zone.
ossification or osteogenic zone
This leaves long slender spicules of calcified cartilage at the epiphysis-diaphysis junction, which looks like stalactites hanging from the roof of a cave. These calcified spicules...
In the adult skeleton, bone deposit and bone resorption (removal) occur both at the surface of the periosteum and the surface of the endosteum. Together, the two processes constitute...
Occurs wherever bone is injured or added bone strength is required. for optimal bone deposit, a healthy diet rich in proteins, vitamin C, vitamin D, vitamin A, and several minerals...
is accomplised by osteoclasts, giant multinucleate cells that arise from the same hematopoietic stem cells that differentiate into macrophages.
Parathyroid hormone (PTH)
The hormonal controls primarily involve parathyroid hormone (PTH), produced by the parathyroid glands.
To a much lesser extent calcitonin, produced by parafollicular cells (C cells) of the thyroid gland, may be involved. PTH is released when blood levels of ionic calcium decline. The...
Response to mechanical stress
The second set of controls regulating bone remodeling, bone's response to mechanical stress (muscle pull) and gravity, serves the needs of the skeleton by keeping the bones strong where...
Wolff's Law (observations)
1. Handedness (being right or left handed) results in the bones of one upper limb being thicker than those of the less-used limb, and vigorous exercise of the most-used limb leads to...
Despite their remarkable strength, bones are susceptible to fractures, or breaks. During youth, most fractures result from exceptional trauma that twists or smashes the bones (spots...
How are fractures treated?
A fracture is treated by reduction, the realignment of the broken bone ends. In closed (external) reduction, the bone ends are coaxed into position by the physician's hands....
Repair in a simple fracture involves four major stages:
1. A hematoma forms. When a bone breaks, blood vessels in the bone and periosteum, and perhaps in surrounding issues, are torn and hemorrhage. As a result, a hemotoma, a mass of clotted...
Includes a number of disorders in which the bones are inadequately minderalized. Osteoid is produced, but calcium salts are not deposited, so bones soften and weaken. The main sumptom...
Is the analogous disease in children. Because young bones are still growing rapidly, rickets is much more severe than adult osteomalacia. Bowed legs and deformities of the pelvis, skull,...
Common Types of FracturesComminuted
Bone fragments into three or more pieces. Particularly common in the aged, whose bones are more brittle.
Common Types of FracturesCompression
Bone is crushed. Common in porous bones (i.e. osteoporotic bones) subjected to extreme trauma, as in a fall.
Common Types of FractureSpiral
Ragged break occurs when excessive twisting forces are applied to a bone. Common sports fracture.
Common Types of FracturesEpiphyseal
Epiphysis seperates from the diaphysis along the epiphyseal plate. Tends to occur where cartilage cells are dying and calcification of the matrix is occuring.
Common Types of FracturesDepressed
Broken bone portion is pressed inward. Typical of skull fracture.
Common Types of FracturesGreenstick
Bone breaks incompletely, much in the way a green twig breaks. Only one side of the shaft breaks; the other side bends. Common in children, whose bones have relatively more organic...
Refers to a group of diseases in which bone resorption outpaces bone deposit. The bones become so fragile that something as simple as a hearty sneeze or stepping off a curb can cause...
Often discovered by accident when X rays are taken for some other reason, Paget's disease is characterized by excessive and haphazard bone deposit and resoption. The newly formed bone,...