(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