Skeletal and Muscular Systems

Objectives

• Explain how bones grow and develop
• Distinguish types of joints and how they move
• Describe the three types of human muscle tissue
• Explain how skeletal muscles move bones

Bones are hard because they store minerals as mineral salts. When levels in the blood are low, bones release them, restoring homeostasis.

Bones

• Living tissue
• Have blood supply
• Constantly making new bone

As a fetus, the skeleton is made of cartilage. It is changed to bone through ossification.

Ossification begins at the center and continues toward bone ends. At birth, several areas of cartilage remain.

A thin layer of cartilage reduces friction at joints.

Joints

• Immovable, ie skull
• Partly movable, ie ribs
• Movable joints, aka synovial joints

Movable Joints

• Bones connected by ligament
• Space between filled with synovial fluid
• Ball-and-socket, eg shoulder
• Hinge, eg knee
• Pivot, eg elbow

Muscles

Muscle Cells

• AKA muscle fiber
• Long, thin
• Can contract
• Three types

Smooth Muscle

• Contractions involuntary
• Helps organs carry out functions
• Eg, lines stomach and intestines

Skeletal Muscle

• Contractions volutary
• Most common muscle type
• Muscle that is attached to bone
• Over 600 in the human body
• Wrapped in connective tissue for support

Skeletal Muscle

• Attached to skeleton by tendons
• Can only contract
• Can increase in size, strength, and efficiency
• Will atrophy if not used

Cardiac Muscle

• Contractions involutary
• Found only in heart walls
• Contains many mitochondria
• Arranged in bundles, so striated