Packet 16 Notes (A) THE SKELETON

Packet 16 Notes
Aim: How does the musculoskeletal system aid in movement?
o the skeletal system has many important functions:
 supports the body—like the frame of a house
 protects internal organs—forms a protective shell around the delicate
 provides for movement—muscles pull on bones enabling movement
 stores minerals –mainly calcium
 provides a site for blood formation—blood cells are produced in the
bone marrow
o there are 206 bones in the adult human skeleton
o the skeleton can be divided into two parts
1. axial skeleton—supports the central axis of the body—consists of the skull,
the vertebral column, and the rib cage
2. appendicular skeleton—made up of the appendages—arms, legs, pelvis,
 Bones are a solid network of living cells and proteins fibers that are surrounded
by deposits of calcium salts.
 Bones are made up of bone cells called osteocytes.
 Within bones are cavities that contain a soft tissue called bone marrow—yellow
bone marrow is mostly made up of fat—red bone marrow is where blood cells
are formed.
 The skeleton of an embryo is composed almost entirely of cartilage.
 Cartilage is a connective tissue that supports the body but is more flexible than bone
 Cartilage is replaced by bone during a process called ossification—bone formation
 A place where one bone attaches to another is called a joint.
 Joints permit bones to move without damaging each other.
 Ligaments hold bones together at joints
 Depending on its type of movement, a joint is classified as immovable,
slightly movable or freely moveable.
 Immovable joints—allow no movement—skull
 Slightly moveable—permit a small amounts of restricted
 Freely Moveable—permit movement in one or more directions—
knee, shoulder
 Arthritis—inflammation of the joint
 Osteoporosis—a weakening of the bones due to loss of calcium—healthy nutrition and
exercise can prevent osteoporosis
 Muscle tissue is found everywhere in the body
 There are three different types of muscle tissue each with a specific function in the
Skeletal muscle
 Usually attached to bone
 Responsible for voluntary movement—movements you control
 Have striations—resemble light and dark stripes—called striated tissue
 Have many nuclei
2) Smooth muscle
 Usually not under voluntary control
Has only one nucleus and is non-striated
Found in the walls of hollow organs—stomach, blood vessels, intestines
3) Cardiac Muscle
 Found only in the heart
 Is striated with only one or two nuclei
 Involuntary
 Skeletal muscles generate force and produce movement by contracting or pulling on
body parts
 Most skeletal muscles work in opposing pairs—when one contracts the other relaxes
 Regular exercise is important in maintaining muscular strength and flexibility
 Muscles that are exercised regularly stay firm and increase in size and strength
 Muscles that are not used become weak and can visibly decrease in size
 Aerobic exercise causes your systems to become more efficient
 Regular exercise can also strengthen bones and decrease body fat