skeletal system ni maam karra baro

8/11/2019 Skeletal System ni maam karra baro

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Introduction As organisms evolved from their ancestors, systemsinvolved in movement and support evolvedsimultaneously with the increase in body size.

4 cell types that contribute to movement:(1) amoeboid cells,

(2) flagellated cells(3) ciliated cells(4) muscle cells


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Functionsprovide rigidity to the bodysurfaces for muscle attachment

protection for vulnerable body organs


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3 kinds of skeleton for support:(1) fluid hydrostatic skeletons(2) rigid exoskeletons

(3) rigid endoskeletons


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The Invertebrates Skeletal System 1. Hydrostatic (Gr. hydro, water statikos, to stand)

skeleton- a core of liquid (water or a body fluid suchas blood) surrounded by a tension-resistant sheath oflongitudinal and or circular muscles.


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DIRECTION OF MOVEMENT


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Rigid skeletons consist of rigid elements to whichmuscles can attach. Since muscles can only contractand not actively lengthen, rigid skeletons provide theanchor points required by opposing sets of muscles,such as flexors and extensors, that allow movement inmore than one direction

2 TYPES:1. Exoskeleton2. Endoskeleton


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2. Rigid Exoskeletons (Gr. exo, outside, skeleton)Primarily: for locomotor functions because they

provide sites for muscle attachment and counterforcefor muscle movements.Secondary functions: support and protect the body


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Example:The epidermis of arthropods secretes a thick, hardcuticle that waterproofs the body . It also protects andsupports soft internal organs. Lastly, the exoskeletonalso prevents internal tissues from drying out.

Exoskeletons, however, limit an animals growth. Someanimals shed the exoskeleton periodically, asarthropods do when they molt.


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However, certain regionsof the arthropod bodyhave thin, f lexible cuticle,

and joints. It is in these

areas that pairs ofantagonistic musclesfunction through a system

of levers to produce

coordinated movement.


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3. Endoskeletons of Invertebrates (Gr. endo, within skeleton ).

Example : 1.sponges - consist of mineral spicules andfibers of spongin that keep the body from collapsing2. echinoderms - consist of small, calcareous

plates called ossicles.

The most familiar endoskeletons, however, are in vertebrates.


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The Vertebrates Skeletal System vertebrate skeletal system = endoskeleton + body tissues.

This endoskeleton consists of two main types of supportive

tissue: cartilage and bone


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Cartilagea specialized type of connective tissue that provides asite for muscle attachment, aids in movement at joints,and provides support

resists compression

consists of cells (chondrocytes) in lacunae, fibers, anda cellular matrix


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The basic form - hyaline cartilage which has a clear,glassy appearance

Blood vessels are virtually absent

the reason thatsports injuries involving cartilage heal slowly.

Two other types of cartilage : elastic and fibrous


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Bonea specialized connective tissue that provides a point ofattachment for musclestransmits the force of muscular contraction from onepart of the body to another during movementsupport the internal organs of many animalsstore reserve calcium and phosphate

manufacture red blood cells and some white bloodcells


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Bones are rigid than cartilage because of calciumphosphate and calcium carbonate

Bone cells (osteocytes) are in minute chambers calledlacunae, which are arranged in concentric ringsaround osteonic canals .These cells communicate with

nearby cells by means of cellular processes passingthrough small channels called canaliculi.


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Bone DevelopmentBone is never formed in vacant space but is always areplacement in areas occupied by connective tissue.Bone development from cartilage - endochondral(within -cartilage) or replacement bone intramembranous bone - which develops directlyfrom sheets of embryonic cells


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Bone accdg to densitySpongy (or cancellous) bone - consists of an open,interlacing framework of bony tissueCompact bone - dense, appearing solid to theunaided eye. Forms after further deposition of bonematrix


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Skeleton of the Fisheshave an axial skeleton (so named because it forms thelongitudinal axis of the body) that includes anotochord, ribs, and cartilaginous or bony vertebrae

muscles used in locomotion attach to the axialskeleton.


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Skeleton of the TetrapodsDuring the evolution of the aquatic animals tobecoming terrestrial animals, the tetrapodendoskeleton became modified for support on land

This is a result of the specializations of theintervertebral disks that articulate with adjoining vertebrae. The intervertebral disks help hold the vertebral column together, and they also absorb shockand provide joint mobility.


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Bone replaced cartilage in the ribs

Connective tissues connected to the axial skeleton helpkeep elevated portions from sagging

Appendages became elongated for support on a hardsurface, and changes in the shoulder enabled the neckto move more freely


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Human EndoskeletonTwo major parts:

1.axial skeleton - the skull, vertebral column,sternum, and ribs

2. appendicular skeleton - the appendages, thepectoral girdle, and the pelvic girdles. These girdlesattach the upper and lower appendages to the axialskeleton


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skeletal system ni maam karra baro

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