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Chapter 7
Bones and Muscles
The Skeletal System
The skeletal system
consists of two
broad divisions:
1. The axial skeleton
2. The appendicular
skeleton
Axial Skeleton
The eighty bones that
make up the head
and spine:
Bones of the skull
Hyroid – bone of neck
Vertebrae – bones of
neck and backbone
Sternum – breastbone
Ribs
Appendicular Skeleton
Bones on the
appendages (arms
and legs)
Bones of the hips and
shoulders.
Bones of the Head
The skull is divided into
two parts:
1. Cranium
2. Facial bones
Cranial Bones
The 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 Bones
Includes 14 Bones:
Serve as the framework of
the face and jaw
Two maxillary bones – serve
as attachment for upper
teeth
Palatine bones – form the
roof of the mouth
Mandible – ONLY
MOVABLE bone of skull
Facial Bones
The smallest bones of
your body are found
in your ears…
The Malleus
(hammer)
The Stapes
(stirrup)
The Incus (anvil)
Bones of the Spine
Regions of the vertebral column:
1.
2.
3.
4.
Cervical vertebrae (top 7)
Thoracic vertebrae (next 12)
Lumbar vertebrae (next 5)
Sacral vertebrae
a) (next 5, fused in adults sacrum)
b) (last 4, fused in adults –
coccyx)
Bones of the Chest
Thoracic Cage:
includes ribs and s ternum
Classification of Bones
Bones are classified into four categories:
1.
2.
3.
4.
Long bones
Short bones
Flat bones
Irregular bones
Design of the Bone
A 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 Strength
• Outer shell is strong and dense –
compact bone
• Inside is lightweight, porous tissue –
spongy bone
it looks “spongy”, but it is hard
• Inside 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 Restoration
• Bones 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
canals
2. osteoblasts – construct new fibers and
crystals
Muscles
There are two major types of muscles:
1. Voluntary Muscle
You have control of these muscles.
2. Involuntary Muscle
You do not have conscience control of
these muscles.
Skeletal Muscle
• You have voluntary control over skeletal
muscle
• The 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 Muscle
• These 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 Muscle
• Muscle on the face is attached directly to
the bone.
• Skeletal muscle is designed to move
quickly and powerfully.
Smooth Muscle
• Smooth 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 Muscle
• Cardiac muscle is found only in the heart.
• It is designed to contract over and over
without tiring.
The Design of Skeletal Muscle
Fiber 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 Muscle
• The muscle cells are called muscle fibers.
Structure of Muscle Cells
• A 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 Cells
• Each 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.
• When the muscle contracts, the myosin
and actin work to shorten the cell.
Structure of Muscle Cells
• Each myofibril is surrounded by an
extensive network of pipes and reservoirs
called sarcoplasmic reticulum.
• Addition pipes called transverse tubules
connect the sarcoplasmic reticulum to the
cell membrane.
• Both of these trigger the myofibril to
contract.
Nerve Impulse Reception
• Muscle contractions are triggered by your
nervous system.
• The point at which the nerve attaches to a
muscle cell is called neuromuscular
junction.