chapter 20 bones and muscles. the skeletal system the skeletal system consists of two broad...
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Chapter 20Bones and Muscles
The Skeletal SystemThe skeletal system consists of two broad divisions:The axial skeleton The appendicular skeleton
Axial SkeletonThe eighty bones that make up the head and spine:
Bones of the skullHyroid bone of neckVertebrae bones of neck and backboneSternum breastboneRibs
Appendicular SkeletonBones on the appendages (arms and legs)Bones of the hips and shoulders.
Bones of the HeadThe skull is divided into two parts:CraniumFacial bones
Cranial BonesThe cranium is made of eight bones tightly formed:
Frontal bone (forehead)Parietal bone (top of head)Temporal Bone (sides of head)Occipital Bone (back of head)
Facial BonesIncludes 14 Bones: Serve as the framework of the face and jaw
Two maxillary bones serve as attachment for upper teethPalatine bones form the roof of the mouthMandible ONLY MOVABLE bone of skull
Facial BonesThe smallest bones of your body are found in your ears
The Malleus (hammer)The Stapes (stirrup)The Incus (anvil)
Bones of the SpineRegions of the vertebral column:
Cervical vertebrae (top 7)Thoracic vertebrae (next 12)Lumbar vertebrae (next 5)Sacral vertebraea) (next 5, fused in adults - sacrum)b) (last 4, fused in adults coccyx)
Bones of the ChestThoracic Cage:includes ribs and sternum
Classification of BonesBones are classified into four categories:
Long bonesShort bonesFlat bonesIrregular bones
Design of the BoneA long bone (like a femur) has a shaft known as the diaphysis and bulged ends known as epiphysis.
The bone is enclosed in a protective sheath called periosteum (has blood vessels in it).
Engineered for StrengthOuter shell is strong and dense compact boneInside is lightweight, porous tissue spongy bone it looks spongy, but it is hardInside the porous spongy bone is the red marrow (produces blood cells)Inside the center is the medullary cavity has red marrow in young children and yellow marrow in adults.
Maintenance and RestorationBones are self repairing, self maintaining, self modifying.Two types of cells maintain the bones:1. osteoclasts remove old material to make room for new in the Haversian canals2. osteoblasts construct new fibers and crystals
MusclesThere are two major types of muscles:
Voluntary Muscle You have control of these muscles.Involuntary MuscleYou do not have conscience control of these muscles.
Skeletal MuscleYou have voluntary control over skeletal muscleThe primary function of these over 600 muscles is to move the skeleton.These muscles are made up of individual cells known as muscle fibers.Each skeletal muscle is composed of thousands of these muscle fibers.
Skeletal MuscleThese muscle fibers give skeletal muscle a striped, or striated appearance.Because of this, skeletal muscle is also called striated muscle.Most skeletal muscle is attached to bone with tendons.
Skeletal MuscleMuscle on the face is attached directly to the bone.Skeletal muscle is designed to move quickly and powerfully.
Smooth/Visceral MuscleSmooth muscle consist of shorter, wider cells in a looser arrangement.Smooth muscle is specialized for relatively slow, powerful, and prolonged contractions.It adjusts the tension in the walls of blood vessels.It controls the organs of the digestive system.It controls the lens of your eye.
Cardiac MuscleCardiac muscle is found only in the heart.It is designed to contract over and over without tiring.
The Design of Skeletal MuscleFiber bundles and connective tissue:
The skeletal muscle is encased in a tough, translucent sheath called the fascia. It functions to bind the muscle together.
At the end the fascia tapers into strong tendons that hold the muscle to bone.
The Design of Skeletal MuscleThe muscle cells are called muscle fibers.
Structure of Muscle CellsA muscle cell is just like other cells with a cell membrane.However, they have more than one nuclei and more than the usual number of mitochondria.Myofibrils extend the length of the muscle cells.A single muscle cell has dozens or hundreds of myofibrils.
Structure of Muscle CellsEach myofibril is composed of millions of overlapping protein fibers arranged in repeating units called sarcomeres.The sarcomeres give the skeletal muscle their striated appearance.They are composed of thick Myosin filaments and thin actin filaments.
Structure of Muscle CellsWhen the muscle contracts, the myosin and actin work to shorten the cell.Each myofibril is surrounded by an extensive network of pipes and reservoirs called sarcoplasmic reticulum.
Structure of Muscle CellsAddition pipes called transverse tubules connect the sarcoplasmic reticulum to the cell membrane.Both of these trigger the myofibril to contract.
Nerve Impulse ReceptionMuscle contractions are triggered by your nervous system.The point at which the nerve attaches to a muscle cell is called neuromuscular junction.