Chapter One

Table of Contents Section 1 Body Organization Section 2 The Skeletal System Section 3 The Muscular System Section 4 The Integumentary System

Objectives Describe how tissues, organs, and organ systems are related. List 11 major organ systems. Identify how organ systems work together to maintain homeostasis.

Cells, Tissues, and Organs The many kinds of cells in your body help your internal environment stay stable. The maintenance of a constant internal state in a changing environment is called homeostasis.

Cells, Tissues, and Organs, continued Cells Form Tissues A group of similar cells working together forms a tissue. Your body has four main kinds of tissue.

Cells, Tissues, and Organs, continued Tissues Form Organs Two or more tissues working together to carry out a specialized function form an organ.

Working Together Organs Form Systems Organs that work together make up an organ system. Organ systems work together to maintain homeostasis. Your body has 11 major organ systems.

Objectives Identify the major organs of the skeletal system. Describe four functions of bones. Describe three types of joints. List three injuries and two diseases that affect bones and joints.

Bones Bones, cartilage, and the connective tissue that holds bonds together make up your skeletal system. Bone Structure Bone tissue without any visible open spaces is called compact bone. Bone tissue that has many open spaces is called spongy bone. Bones contain a soft tissue called marrow. Bone Growth Most bones start out as a flexible tissue called cartilage. Eventually, most cartilage is replaced by bone.

Joints A place where two or more bones meet is called a joint. Joints are held together by ligaments.

Skeletal System Injuries and Diseases Bones may be fractured or broken. Ligaments can be stretched or torn. Arthritis is a disease that causes the joints to swell or stiffen. Osteoporosis is a disease that causes bones to become less dense.

Objectives List three kinds of muscle tissue. Describe how skeletal muscles move bones. Compare aerobic exercise with resistance exercise. Describe two muscular system injuries.

Kinds of Muscle The muscular system is made up of the muscles that let you move. Involuntary muscle found in the digestive tract and the walls of the blood vessels is called smooth muscle. Involuntary muscle found in your heart is called cardiac muscle. Muscle attached to your skeleton for movement is called skeletal muscle. Skeletal muscle can be voluntary or involuntary.

Movement Muscles Attach to Bones Tendons are strands of tough connective tissue that connect your skeletal muscles to your bones. Muscles Work in Pairs Skeletal muscles often work in pairs. A muscles that bends part of your body is called a flexor. A muscle that straightens part of your body is an extensor.

Use It or Lose It Resistance Exercise During resistance exercise, people work against the resistance, or weight, of an object to strengthen their skeletal muscles. Aerobic Exercise Steady, moderately intense activity is called aerobic exercise, and strengthens the heart and increases endurance.

Muscle Injury A strain is an injury in which a muscle or tendon is overstretched or torn. People who exercise too much can hurt their tendons. Inflamed tendons is called tendonitis. Some people try to make their muscles stronger by taking drugs. These drugs are called anabolic steroids and can cause long-term health problems.

Objectives List four functions of skin. Describe the two layers of skin. Describe the structure and function of hair and nails. Describe two kinds of damage that can affect skin.

Functions of Skin Your skin, hair, and nails make up your integumentary system. Skin protects you by keeping water in your body and foreign particles out of your body. Nerve endings in your skin let you feel things around you. Skin helps regulate your body temperature. Skin also helps get rid of waste chemicals.

Layers of Skin Epidermis The epidermis is the outermost layer of skin. Most cells in the epidermis are dead. Dermis The thicker layer of skin that lies beneath the epidermis is the dermis.

Hair and Nails A hair forms at the bottom of a tiny sac called a hair follicle. Hair helps protect skin from ultraviolet light and helps regulate body temperature in most mammals. A nail grows from living cells in the nail root at the base of the nail. Nails protect the tips of your fingers and toes.

Skin Injuries Skin is often damaged, but fortunately can repair itself. However, damage to the genetic material in skin cells can cause skin cancer.