Lesson 1

How is it possible for you to perform motions such as stretching and rolling your shoulders?

The interaction of bones and muscles allows you to perform these motions.

The Skeletal System

Lesson 1

Identify the functions of the skeletal system.

Describe the main divisions and types of bones of the skeletal system.

Recognize how understanding the functions of the skeletal system is important for maintaining personal health.

In this lesson, you’ll learn to:

Lesson Objectives

Lesson 1 Functions of the Skeletal System

What Does Your Skeletal System Do?

Your skeletal system protects your internal tissues and organs from trauma.

The skull, vertebrae, and ribs create protective cavities for the brain, the spinal cord, and the heart and lungs, respectively.

Bones store minerals such as calcium and phosphorus, which are important to the health and strength of the skeleton and to various essential processes in your body.

Bone marrow, a connective tissue within bones, produces new red blood cells and white blood cells.

Lesson 1

The Axial and Appendicular Skeletons

Your skeletal system consists of 206 bones that can be classified in two main groups:

1. Axial skeleton

2. Appendicular skeleton

Structure of the Skeleton

Lesson 1

The Skeletal System

Structure of the Skeleton

Lesson 1

Types of Bones

All bones are covered with an outer layer of hard, densely packed, compact bone, beneath which is spongy bone filled with red bone marrow.

Long bones

Short bones

Flat bones

Irregular bones

Almost every bone in the body can be categorized by shape:

Structure of the Skeleton

Lesson 1

The humerus is the bone in your upper arm.

The diaphysis, or main column of a long bone, is composed of compact bone.

Within the diaphysis is a narrow cavity that contains yellow bone marrow.

The end of a long bone is called the epiphysis.

Long Bones

Humerus

Structure of the Skeleton

Lesson 1

Short Bones

Short bones are almost equal in length and width.

Wrist

Structure of the Skeleton

Lesson 1

Flat Bones

Flat bones are somewhat thinner and much flatter than other bones.

Flat bones, such as those in the skull, protect organs.

Irregular Bones

Irregularly shaped bones have unusual shapes and do not fit into the other categories.

Rib

Structure of the Skeleton

Lesson 1

Cartilage

In some joints, such as the knee, cartilage acts as a cushion, reducing friction and allowing smooth motion.

An embryo’s skeleton consists mostly of cartilage that serves as a template from which bones will form.

Early in embryonic development, the cartilage hardens, which is called ossification.

Structure of the Skeleton

Lesson 1

Joints

Some joints, such as those between the bones of the skull, do not move.

Others, including the joints between vertebrae, have limited movement.

Ligaments help stabilize the movements of bones at a joint.

Movement is produced because muscles are attached to bones by tendons and ligaments.

Structure of the Skeleton

Lesson 1

Classification of Flexible Joints

Ball-and-socket joints allow the widest range of movement in all directions.

Hinge joints allow a joint to bend and straighten, promoting rotation.

Pivot joints allow limited rotation or turning of the head.

Ellipsoidal joints allow bones to slide over one another.

Hip (ball-and-socket joint)

Knee (hinge joint)

Structure of the Skeleton

Lesson 1

Choose the appropriate option.

Q. _______ is a strong, flexible

connective tissue.

Click Next to view the answer.

1. Cartilage 2. A ligament

3. An axial skeleton

4. A tendon

Quick Review

Lesson 1

Click Next to attempt another question.

A. Cartilage is a strong, flexible connective tissue.

Quick Review - Answer

Lesson 1 Quick Review

Provide a short answer to the question given below.

Click Next to view the answer.

Q. What are the functions of the skeletal system?

Lesson 1

A. The functions of the skeletal system are:

To support the upper body and head

To provide a strong, stable, and mobile framework on which muscles can act

To protect the internal tissues and organs from trauma

Click Next to attempt another question.

Quick Review - Answer

Lesson 1

Provide a short answer to the question given below.

Click Next to view the answer.

Q. Name and give examples of each type of joint.

Quick Review

Lesson 1

Click Next to attempt another question.

A. The types of joints are:

Ball-and-socket joints: e.g., hip or shoulder joint

Hinge joint: e.g., elbow, knee, ankle, and finger joints

Pivot joints: e.g., top two vertebrae

Ellipsoidal joints: e.g., wrist

Quick Review - Answer

Lesson 1

Provide a suitable analysis.

The ligament that holds the bones in your forearm together and helps form the pivot joint there has been torn. How might this affect your ability to move your hand and arm? What movements might be affected?

Quick Review

Lesson 1

The Axial and Appendicular Skeletons

Your skeletal system consists of 206 bones that can be classified in two main groups:

1. Axial skeleton

2. Appendicular skeleton

The axial skeleton consists of the 80 bones of the skull, spine, ribs, vertebrae, and sternum, or breastbone.

The axial skeleton consists of the 80 bones of the skull, spine, ribs, vertebrae, and sternum, or breastbone.

Structure of the Skeleton

Lesson 1

The Axial and Appendicular Skeletons

Your skeletal system consists of 206 bones that can be classified in two main groups:

1. Axial skeleton

2. Appendicular skeleton

The appendicular skeleton is composed of the remaining 126 bones of the upper and lower limbs, shoulders, and hips.

The appendicular skeleton is composed of the remaining 126 bones of the upper and lower limbs, shoulders, and hips.

Structure of the Skeleton

Lesson 1

Cartilage

In some joints, such as the knee, cartilage acts as a cushion, reducing friction and allowing smooth motion.

An embryo’s skeleton consists mostly of cartilage that serves as a template from which bones will form.

Early in embryonic development, the cartilage hardens, which is called ossification.

Cartilage is a strong, flexible connective tissue.

Cartilage is a strong, flexible connective tissue.

Structure of the Skeleton

Lesson 1

Cartilage

In some joints, such as the knee, cartilage acts as a cushion, reducing friction and allowing smooth motion.

An embryo’s skeleton consists mostly of cartilage that serves as a template from which bones will form.

Early in embryonic development, the cartilage hardens, which is called ossification.

Ossification is the process by which bone is formed, renewed, and repaired.

Ossification is the process by which bone is formed, renewed, and repaired.

Structure of the Skeleton

Lesson 1

Joints

Some joints, such as those between the bones of the skull, do not move.

Others, including the joints between vertebrae, have limited movement.

Ligaments help stabilize the movements of bones at a joint.

Movement is produced because muscles are attached to bones by tendons and ligaments.

A ligament is a band of fibrous, slightly elastic connective tissue that attaches bone to bone.

A ligament is a band of fibrous, slightly elastic connective tissue that attaches bone to bone.

Structure of the Skeleton

Lesson 1

Joints

Some joints, such as those between the bones of the skull, do not move.

Others, including the joints between vertebrae, have limited movement.

Ligaments help stabilize the movements of bones at a joint.

Movement is produced because muscles are attached to bones by tendons and ligaments.

A tendon is a fibrous cord that attaches muscle to the bone.

A tendon is a fibrous cord that attaches muscle to the bone.

Structure of the Skeleton

Lesson 1

A. Correct! Cartilage is a strong, flexible connective tissue.

Click Next to attempt another question.

Quick Review - Answer

Lesson 1

You have answered the question incorrectly. Go back to try again, or click Next to view the correct answer.

Quick Review - Answer