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Skeletal, Muscular & Integumentary Systems
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Skeletal System
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FUNCTIONS:
Supports the body
Protects internal organs
Provides for movement – levers act with muscles
Stores mineral reserves
Provides a site for blood formation
Skeletal System Divisions
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Axial – supports the central axis of the body (skull, vertebral column, rib cage
Appendicular – bones of the arms, legs, pelvis & shoulder
Bone Structure
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Bones are living tissue – a solid network of cells & protein fibers that are surrounded by hardened deposits of calcium salts
Outer layer = periosteum (tough connective tissue)
Thick inner layer = compact bone with Haversian canals
Second inner layer = spongy bone
Innermost layer = bone marrow
• Yellow marrow – mostly fat cells• Red marrow – produces rbc, some wbc, platelets, contains stem cells
Bone Development
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An embryo skeleton is almost entirely cartilage
Strong, flexible connective tissue No blood vessels
Cartilage is replaced by bone during the process of ossification
Ossification begins 6-7 months before birthBone growth occurs at the ends of long bones
Bone Connections
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Joint – place where one bone connects to another bone
Bones connect to bones through ligaments
Joint Types:
Immovable joint (fixed joints) – allow no movement between bones that touch each other (skull)
Slightly movable joint – small amount of restricted movement (slight separation from each other) (vertebrae)
Freely movable joint – permit movement - ball-and-socket - hinge - saddle - pivot
Muscular System
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Muscles are specialized tissue that can contract and relax. Muscles work with the skeletal system to allow movement.
Three types of muscles:
Skeletal – attached to bonesto allow voluntary movement
Smooth – usually not under voluntary control
Cardiac – heart muscle
Skeletal Muscle
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Alternating light & dark bands (striation)
Usually voluntary control
Large cells that can have many nuclei
Found all over the body – usually attached to bones
Smooth Muscle
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Spindle –shaped cells
One nucleus
Found in walls of hollow structures (blood vessels, stomach, intestines)
Involuntary control
Cardiac Muscle
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Striated
Has one or two nuclei per cell
Usually involuntary control
Found ONLY in the heart
Skeletal Muscle Anatomy
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Skeletal muscle consists of bundles of muscle fibers
Bundles of muscle fibers are composed of individual muscle fiber cells
Each muscle fiber consists of myofibrils that have light & dark bands (striations)
Each myofibril is made up of thick filaments (myosin protein) & thin filaments (actin protein)
A unit of alternating actin & myosin = sarcomere, separated by a dense “Z band” matter
Muscle Contraction Control
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The axon terminal contains vesicles with the neurotransmitter Acetylcholine (Ach).
An action potential causes the vesicles to release the Ach across the neuromuscular synapse.
This causes the release of Ca+ in the muscle fiber causing actin & myosin to interact.
As long as Ach is released, the muscle will contract. As soon as the Ach is stopped, the muscle relaxes.
Muscles and bones
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Skeletal muscles connect to bones through tendons.
There are usually several tendons connecting many muscles around a joint. Muscles usually act in opposing pairs.
Integumentary System
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Integument = “covering”
SkinHairNailsSome glands (found in skin)
Skin primary functions:Barrier against infection & injuryHelps regulate body temperatureRemoves waste productsProtection against UV radiation
Skin Anatomy
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Epidermis-Two layers: dead outermost layer & inner living layer-Keratin-Melanin-No blood vessels
Dermis-Next inner layer-Collagen-Many blood vessels-Nerve endings-Sensory receptors-Glands: sweat & sebaceous-Smooth muscles-Hair follicles
Hypodermis-Mainly fat storage-Contains larger blood vessels & larger nerve fibers
Hair & Nails
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Formed from keratin (fibrous protein)Forms horns, reptile scales, bird feathers, porcupine quills
Hair is produced at the base by hair follicles
Sebaceous (oil) glands help maintain hair health
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Nails grow from an area of rapidly dividing cells = nail root.
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