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

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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

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(Click)

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.