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PJM 3106

ANATOMI DAN FISIOLOGI

TAJUK 2 & 3

SISTEM RANGKA


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INTRODUCTION

The human body contains 206 bones

organized into a structural framework calledskeleton. The bones of the skeletal system

are controlled by hundreds of muscles,

which in turn are controlled by impulsesfrom central nervous system


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Anatomically, the skeleton is divided into

two major sections.

1. Axial Skeletal

which is composed of bones of the bodys

central axis (skull, vertebral column, the rib

cage)2. Apppendicular Skeleton

which is composed of bones of the upper and

lower appendages and bones attaching them to

axial skeletal

Articulation (Joints)

The junctions where two or more bones come

together


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FUNCTIONS OF BONES

1. Support

Bones provide a hard framework that support

the body and cradles its soft organs. For

example, bones of lower limbs act as pillars tosupport the body trunk when we stand, and

the rib cage support the thoracic wall

2. ProtectionThe fused bones of the skull provide a snug

enclosure for the brain. The vertebrae

surround the spinal cord, and rib cage helps

protect the vital organs of the thorax


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3. Movement

Skeletal muscles, which are attached to bones

by tendons, use the bones as levers to move

the body and its parts. As a result, we can

walk, and breathe. The arrangement of bones

and the design of joint determine the type of

movement possible

4. Mineral Storage

Bones serves as a reservoir for minerals, the

most important of which are calcium andphosphate. The stored minerals can be

realeased into the bloodstream as ions to

distribution to all parts of the body as needed.


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Indeed, deposits and withdrawal of

minerals to and from the bones go on almost

continuously

5. Blood cell formationThe bulk of blood cell formation, or

hematopoiesis, occur within the marrow

cavities of certain bones .


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CLASSIFICATIONS OF BONES

The bones of the body come in a variety of sizes and

shapes. The four principal types of bones are long,

short, flat and irregular

Long Bones

Bones that are longer than they are wide are called

long bones. They consist of a long shaft with two

bulky ends or extremities. They are primarily

compact bone but may have a large amount of

spongy bone at the ends or extremities. Long bones

include bones of the thigh, leg, arm, and forearm.


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Short Bones

Short bones are roughly cube shaped with

vertical and horizontal dimensions

approximately equal. They consist primarily

of spongy bone, which is covered by a thin

layer of compact bone. Short bones includethe bones of the wrist and ankle.

Flat BonesFlat bones are thin, flattened, and usually

curved. Most of the bones of the cranium are

flat bones.


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Irregular Bones

Bones that are not in any of the above three

categories are classified as irregular bones. Theyare primarily spongy bone that is covered with a

thin layer of compact bone. The vertebrae and

some of the bones in the skull are irregular bones.

All bones have surface markings and characteristics

that make a specific bone unique. There are holes,

depressions, smooth facets, lines, projections and

other markings. These usually representpassageways for vessels and nerves, points of

articulation with other bones or points of

attachment for tendons and ligaments.


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STRUCTURE OF BONES TISSUE

There are two types of bone tissue: compact and

spongy. The names imply that the two types of

differ in density, or how tightly the tissue is

packed together. There are three types of cells

that contribute to bone homeostasis. Osteoblasts

are bone-forming cell, osteoclasts resorb or break

down bone, and osteocytes are mature bone cells.

An equilibrium between osteoblasts and

osteoclasts maintains bone tissue.


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Compact Bones

Compact bone consists of closely packed osteons or haversiansystems. The osteon consists of a central canal called the

osteonic (haversian) canal, which is surrounded by concentric

rings (lamellae) of matrix. Between the rings of matrix, the

bone cells (osteocytes) are located in spaces called lacunae.

Small channels (canaliculi) radiate from the lacunae to theosteonic (haversian) canal to provide passageways through the

hard matrix. In compact bone, the haversian systems are

packed tightly together to form what appears to be a solid

mass. The osteonic canals contain blood vessels that are

parallel to the long axis of the bone. These blood vessels

interconnect, by way of perforating canals, with vessels on

the surface of the bone.


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Spongy Bones

Spongy (cancellous) bone is lighter and less densethan compact bone. Spongy bone consists of plates(trabeculae) and bars of bone adjacent to small,irregular cavities that contain red bone marrow.

The canaliculi connect to the adjacent cavities,instead of a central haversian canal, to receivetheir blood supply. It may appear that thetrabeculae are arranged in a haphazard manner,but they are organized to provide maximumstrength similar to braces that are used to supporta building. The trabeculae of spongy bone followthe lines of stress and can realign if the directionof stress changes.


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Structure of Compact and Sponge Bones


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BONE DEVELOPMENT AND GROWTH

The terms osteogenesis and ossification

are often used synonymously to indicatethe process of bone formation. Parts ofthe skeleton form during the first fewweeks after conception. By the end of

the eighth week after conception, theskeletal pattern is formed in cartilageand connective tissue membranes andossification begins.


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Bone development continues throughout

adulthood. Even after adult stature is

attained, bone development continues for

repair of fractures and for remodeling to

meet changing lifestyles. Osteoblasts,

osteocytes and osteoclasts are the threecell types involved in the development,

growth and remodeling of bones.

Osteoblasts are bone-forming cells,osteocytes are mature bone cells and

osteoclasts break down and reabsorb

bone.


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Type of Ossification

Intramembranous ossification involves the

replacement of sheet-like connective tissue

membranes with bony tissue. Bones formed

in this manner are called intramembranousbones. They include certain flat bones of the

skull and some of the irregular bones. The

future bones are first formed as connective

tissue membranes. Osteoblasts migrate tothe membranes and deposit bony matrix

around themselves. When the osteoblasts

are surrounded by matrix they are called

osteocytes.


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Endochondral ossification involves the replacement ofhyaline cartilage with bony tissue. Most of the bones of

the skeleton are formed in this manner. These bones arecalled endochondral bones. In this process, the futurebones are first formed as hyaline cartilage models. Duringthe third month after conception, the perichondrium thatsurrounds the hyaline cartilage "models" becomes

infiltrated with blood vessels and osteoblasts and changesinto a periosteum. The osteoblasts form a collar ofcompact bone around the diaphysis. At the same time, thecartilage in the center of the diaphysis begins todisintegrate. Osteoblasts penetrate the disintegrating

cartilage and replace it with spongy bone. This forms aprimary ossification center. Ossification continues fromthis center toward the ends of the bones. After spongybone is formed in the diaphysis, osteoclasts break downthe newly formed bone to open up the medullary cavity.


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The cartilage in the epiphyses continues to grow

so the developing bone increases in length. Later,

usually after birth, secondary ossification centersform in the epiphyses. Ossification in the

epiphyses is similar to that in the diaphysis except

that the spongy bone is retained instead of being

broken down to form a medullary cavity. Whensecondary ossification is complete, the hyaline

cartilage is totally replaced by bone except in two

areas. A region of hyaline cartilage remains over

the surface of the epiphysis as the articularcartilage and another area of cartilage remains

between the epiphysis and diaphysis. This is the

epiphyseal plate or growth region.


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Bones Growth

Bones grow in length at the epiphyseal plate by aprocess that is similar to endochondral ossification.The cartilage in the region of the epiphyseal platenext to the epiphysis continues to grow by mitosis.The chondrocytes, in the region next to thediaphysis, age and degenerate. Osteoblasts move in

and ossify the matrix to form bone. This processcontinues throughout childhood and the adolescentyears until the cartilage growth slows and finallystops. When cartilage growth ceases, usually in theearly twenties, the epiphyseal plate completely

ossifies so that only a thin epiphyseal line remainsand the bones can no longer grow in length. Bonegrowth is under the influence of growth hormonefrom the anterior pituitary gland and sex hormonesfrom the ovaries and testes.


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Even though bones stop growing in length in early

adulthood, they can continue to increase in

thickness or diameter throughout life in responseto stress from increased muscle activity or to

weight. The increase in diameter is called

appositional growth. Osteoblasts in the

periosteum form compact bone around theexternal bone surface. At the same time,

osteoclasts in the endosteum break down bone on

the internal bone surface, around the medullary

cavity. These two processes together increase thediameter of the bone and, at the same time,

keep the bone from becoming excessively heavy

and bulky.


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DIVISION OF THE SKELETON

The adult human skeleton usually consists of 206named bones. These bones can be grouped in twodivisions: axial skeleton and appendicularskeleton. The 80 bones of the axial skeleton form

the vertical axis of the body. They include thebones of the head, vertebral column, ribs andbreastbone or sternum. The appendicularskeleton consists of 126 bones and includes the

free appendages and their attachments to theaxial skeleton. The free appendages are theupper and lower extremities, or limbs, and theirattachments which are called girdles.


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Axial Skeleton (80 bones)

Skull (28)

Cranial Bones

Parietal (2)

Temporal (2)

Frontal (1)

Occipital (1)

Ethmoid (1)

Sphenoid (1)


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Facial Bones

- Maxilla (2)

- Inferior nasal concha (2)

- Mandible (1)

- Nasal (2)

- Platine (2)

- Zygomatic (2)

- Lacrimal (2)

- Vomer (1)


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Auditory Ossicles

- Malleus (2)

- Incus (2)

- Stapes (2)


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Vertebral Column

- Cervical vertebrae (7)

- Thoracic vertebrae (12)

- Lumbar vertebrae (5)

- Sacrum (1)

- Coccyx (1)


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Thoracic Cage

- Sternum (1)

- Ribs (24)


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Appendicular Skeleton (126 bones)

Pectoral girdles

- Clavicle (2)

- Scapula (2)


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Upper Extremity

- Humerus (2) - Radius (2)

- Ulna (2) - Carpals (16)- Metacarpals (10) - Phalanges (28)


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Pelvic Girdle

- Coxal, innominate, or hip bones (2)


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Lower Extremity

- Femur (2) - Tibia (2)

- Fibula (2) - Patella (2)- Tarsals (14) - Metatarsals (10)

- Phalanges (28)


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ARTICULATION

An articulation, or joint, is where two

bones come together. In terms of theamount of movement they allow, there

are three types of joints: immovable,

slightly movable and freely movable.


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Our joints have two fundamental functions:

1. Give our skeleton mobility

2. Hold the skeleton together, sometimes playing

the protective role in the process. For example

the rigid joint of the skull, make it secureenclosure for our vital structure

Joint are the weakest parts of the skeleton, buttheir structure resists various forces, such as

crushing or tearing, that threaten to force them

out of alignment


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CLASSIFICATION OF JOINTS

SynarthrosesSynarthroses are immovable joints. The singular form issynarthrosis. In these joints, the bones come in very closecontact and are separated only by a thin layer of fibrousconnective tissue. The sutures in the skull are examples of

immovable joints

AmphiarthrosesSlightly movable joints are called amphiarthroses. Thesingular form is amphiarthrosis. In this type of joint, the

bones are connected by hyaline cartilage or fibrocartilage.The ribs connected to the sternum by costal cartilages areslightly movable joints connected by hyaline cartilage. Thesymphysis pubis is a slightly movable joint in which there isa fibrocartilage pad between the two bones. The jointsbetween the vertebrae and the intervertebral disks are also

of this type.


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Diarthroses

Most joints in the adult body are diarthroses, orfreely movable joints. The singular form isdiarthrosis. In this type of joint, the ends of theopposing bones are covered with hyaline cartilage,the articular cartilage, and they are separated by

a space called the joint cavity. The components ofthe joints are enclosed in a dense fibrous jointcapsule. The outer layer of the capsule consists ofthe ligaments that hold the bones together. Theinner layer is the synovial membrane that secretes

synovial fluid into the joint cavity for lubrication.Because all of these joints have a synovialmembrane, they are sometimes called synovialjoints.


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Types of Synovial Joints

Hinge JointIn Hinge joint, movement occur in one place only.Examples of hinge joint are at the elbow (humerus andulna) and knee (femur and tibia) and fingers (between

phalanges)

Pivot JointA pivot joint is organized to permit rotation. An example

of a pivot joint occurs in the neck where the first twobones of the vertebral column (atlas and axis) cometogether


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Ball and Socket Joint

This joint forms where a ball-like head firs into a cup like

cavity. It allow the most freedom of movement. Occur

where the head of humerus articulates with the glenoid

cavity of the scapula and at the hip where the head of

the femur articulates with acetabulum

Condyloid Joint

Rotation is not possible at this joint, but most other

movement occur here. Condyloid joint exists where theradius meets the carpals at the wrist.


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Saddle Joint

Rotation is also restricted. The union of the carpals

bones with one another and with the metacarpal bonesof the thumb occurs at a saddle joint

Gliding Joint

Permits a gliding movement in a number of different

directions between relatively flat, aricular surfaces. The

places where the articular processes of the vertebrae

come together are examples of gliding joints.


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Movement Allowed by Synovial Joints

1. Flexion 11. Pronation

2. Extension 12. Eversion

3. Hyperextension 13. Inversion

4. Dorsiflexion 14. Protraction5. Plantar flexion 15. Retraction

6. Adduction 16. Elevation

7. Abduction 17. Depression8. Circumduction 18. Gliding

9. Rotation

10. Supination


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