(BAGO MUSCULAR)
Skeletal System
The Skeletal System
For protection of vital organsMaintains shapeSupportive frameworkStorage of mineralsHemapoiesis (bone marrow)For biochemical levers (where muscles act
on) locomotion
Cytoskeleton
Microtubule- tubulinIntermediate filamentMicrofilament - actin
Cell wall
• Cellulose is a carbohydrate molecule that made up the skeletal structure of plant cell wall
• Polysaccharide made up of several hundred to thousand d-glucose units joined together
Different types of skeleton found in animals
Hydrostatic skeletonExoskeletonEndoskeleton
Hydrostatic skeleton
fluid held Under pressure in a closed compartment
Control form and movement through the use of muscles
Common in cnidarians, flatworms, nematodes and annelids
Advantageous in aquatic environment Provides cushion for aquatic animals and support for
crawling and burrowing animals
Cnidarians
Hydra elongates by closing its mouth and constricting contractile cells at its gastro vascular cavity
incompressibility of water allows for inc. In length
flatworms
Interstitial fluid is kept under pressure movements result from localized forces
against the hydrostatic pressure
Roundworms
Fluid at the pseudocoelom is under pressure contraction of longitudinal muscles result in
thrashing movement
Annelids
Coelomic fluid acts as the hydrostatic skeleton
Use of both circular and longitudinal muscles in moving
each segment can change its shape use of Peristaltic movement
Hydrostatic skeleton
Not suitable for terrestrial habitat cannot support running or walking
Exoskeleton
A hard encasement deposited on the surface of animals mollusks-calcareous material
Mantle-produces the exoskeleton increased in diameter of shell during growth
arthropods-chitin Cuticle-secreted by epidermis growth spurts causes shedding (molting)
mollusks
arthropods
endoskeleton
Consists of hard supporting material within soft tissues Ex. Bones, Pen, hard plates of echinoderms, spicules
Sponges
• spicules -made up of inorganic material or fibers of protein
echinoderms
Ossicles- hard plates of echinoderms made up of calcium carbonate crystals each segment is held by protein fibers
locomotion
Different modes of locomotion across different phyla
may be due to environmental factors energy expended
against friction and gravity
locomotion
energetic cost of movement varies Mode of locomotion type of environment
e.g. Energy in walking on land is diff. From walking at the bottom of a river
e.g. Running demands more energy than swimming
swimming
Gravity is less of a problem Resistance is greater fusiform body is an adaptation
diverse form of swimming insects-paddle mollusks-jet-propelled fishes-side-to-side whales-up and down
Locomotion on Land
Gravity is more of a problem than resistance energy is expended by pushing the legs up
and keeping it from falling inertias overcome by moving a leg strong muscles and skeleton are more
important
Locomotion on land
Balance is another factor tail-acts as a counterbalance
acts also a tripod in kangaroos the three feet of quadrupeds also act as a tripod during running-momentum keeps the body upright
rather than contact to land
Hopping-as an adaptation
One of the most energy efficient mode of locomotion
energy is stored in every landing higher the hop, the greater the energy
Considerable energy is expended against resistance to the ground snakes-undulate side to side
body pushes against ground to move forward
Flying
Gravity; is a major problem shape of wings is the key to success
shape is airfoil
The endoskeleton
Chordate skeleton is made up of bones, Cartilage or a combination of the two
Fused together or joined in a joint by a ligament
Cartilage- sharks and rays (chondroichthyes)Bone- other vertebrates divided into two
appendicular axial
the human skeleton
The joints
Synarthroses or fibrous- barely movable or immovable
Amphiarthroses or cartilaginous- slightly movable
Diarthroses or synovial- freely movable
The joints
Ball-and-socket Enables to more limb in different plane
Hinge Movement is restricted in one plane
Pivot Allows rotation
What kind of joint?
What kind of joint?
What kind of joint?
The type of bones
Based on development: Membranous- formation of flat bones Cartilaginous- formation of long bones
Based on histological structure: Compact or cortical Spongy or cancellous
Based on morphology: Long bones Short bones Flat bones Sesamoid Irregular
Intramembranous
Mesenchyme cell in the membrane become osteochondral progenitor cell
osteochondral progenitor cell specialized to become osteoblast Osteoblast produce bone matrix and surrounded collagen fiber
and become osteocyte As the result process trabeculae will develop Osteoblast will trap trabeculae to produce bone Trabeculae will join together to produce spongy cell Cells in the spongy cell will specialize to produce red bone
marrow Cells surrounding the developing bone will produce periosteum Osteoblasts from the Periosteum on the bone matrix will
produce compact bone
Endochondral
Body proportion and posture
Physical law : strength is directly proportional to square of diameter
But, strain is directly proportional to weight (increases per height3)
Animals follow these laws
Imagine. . . . .
The physical laws are not complete....
Relative size of legs to body will not always support an animal
Position of the legs relative to the body should be considered
remember how to increase stability in a structure
muscles and tendons tend to hold most of the stress
Bone tissue Compact bone
Composed of series of Haversiancanals
New bone formed by osteocytes
Spongy bone Ends of long bones Less dense than compact Contains red marrow and
yellow marrow Periosteum
Outer layer of bone Rich in nerve endings,
blood and lymphatic vessels
Inner portions forms new bone or modifies existing bone
Number of Bones
Adult human- 206Baby human- 270
The Appendicular and Axial
Axial (80) Support and protect the organs
of the head, neck and trunk
Appendicular (126) Anchors appendages to the
axial skeleton
The bone cells
OsteoblastsOsteocytesOsteoclasts
FYI- if a type of cell has a suffix –blast it is an immature cell;
-cyte is a mature cell
Osteoblasts
Immature bone cellsProduce osteoid- a matric mainly made up of
collagen type IAlso responsible for the mineralization of the
osteoid matrix through hormones and enzymes
Tend to become lesser in number as a person ages
Osteocytes
Mature osteoblastsFound in lacunaeConnected to each other through cytoplasmic
extension of their cell that occupies the canaliculi
Responsible for calcium homeostasis
Osteoclasts
Type of bone cell that is responsible for the resorption and shaping of bone by removing the mineralized matrix
Bone remodeling
Bone resorption and Bone ossification are involve Resorption- the process of absorbing and assimilating
materials in the bone (minerals) Ossification – process of intrusion of minerals in the
matrix of osteocytes
Responsible in reshaping during growth or injury (functional demands and muscle attachment)
Hormones that affects the bone
Parathyroid hormone Increases calcium in the blood
Calcitonin Decreases calcium in the blood
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