Skeletal and Muscular System

Skeletal and Muscular System

Middle School

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Learning Objectives

• Identify the main parts and jobs of the skeletal system.

• Describe the structure of bones and the different types of bone cells.

• Explain how the skeletal and muscular systems work together for movement.

• Recognize common injuries and diseases that affect the skeletal system.

Key Vocabulary

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Skeletal System

The body's framework of bones and cartilage that provides support, protection, and allows for movement.

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Bone Marrow

The soft tissue inside bones that is responsible for producing the body's new blood cells.

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Ossification

The process where flexible cartilage gradually hardens into bone by depositing minerals such as calcium.

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Joint

The specific location where two or more bones meet, which allows for bodily movement.

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Tendon

Tough, flexible connective tissue that is responsible for attaching the skeletal muscles to bones.

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Involuntary Muscle

Muscle that functions without conscious thought or control, like the cardiac muscle of the heart.

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The Skeletal System: Your Body's Framework

• Your skeletal system is the body's internal framework, containing 206 bones.

• It provides shape, support, protects organs, and helps you to move.

• Bones provide a rigid structure, while cartilage offers flexible support in joints.

• Ligaments are tough tissues that connect your bones together at the joints.

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Multiple Choice

Besides providing shape and support, what is another key function of the skeletal system mentioned on the slide?

• Producing blood cells and storing minerals

• Digesting food

• Regulating body temperature

• Sending nerve signals

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The Structure of Our Bones

• The hard outer layer is compact bone for protection.

• ​Inside, spongy bone holds marrow that makes blood cells.

• A membrane called the periosteum covers the bone's surface.

• The bone matrix is made of collagen and calcium.

Multiple Choice

What is the primary function of the bone marrow found within the spongy bone?

• To produce new blood cells

• To provide a hard, protective outer layer

• To store fat for energy

• To connect bones to other bones

The Cells That Build Your Bones

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Osteoblasts

• These are the builder cells found within your bones.

• They have the responsibility of creating new bone tissue.

• Osteoblasts also produce a protein called collagen for strength.

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Osteoclasts

• These are specialized cells that break down bone tissue.

• This process releases important minerals like calcium into the blood.

• They assist in reshaping bones and repairing any fractures.

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Osteocytes

• These are mature bone cells found inside the bone.

• They help to regulate and control mineral levels in bones.

• Osteocytes also play a role in directing other bone cells.

Multiple Choice

What is the name of the process by which soft cartilage hardens into bone?

• Ossification

• Homeostasis

• Reshaping

• Deposition

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Divisions of the Skeleton

Axial Skeleton

• These are the bones located along the central axis of your body.

• It includes the skull, the vertebral column or backbone, and the rib cage.

• Its main function is to provide protection for your most vital organs.

Appendicular Skeleton

• These are the bones that are attached to the axial skeleton.

• It includes the bones of the arms, legs, hands, feet, and girdles.

• Its primary purpose is to allow for locomotion and other body movements.

Multiple Choice

Which of these bone groups belongs to the appendicular skeleton and is primarily responsible for locomotion?

• Arms and legs

• Skull

• Rib cage

• Vertebral column

The Muscular System

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Skeletal Muscle

• ​Attached to bones by tendons, enabling body movement.

• ​​You have conscious control over this voluntary muscle type.

• ​It has a striped or striated appearance under a microscope.

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Smooth Muscle

• ​Found in the walls of your internal organs.

• ​​It works automatically without you thinking about it.

• ​Pushes food through your digestive system for you.

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Cardiac Muscle

• ​This unique muscle is found only in the heart.

• ​​It is an involuntary muscle that never gets tired.

• ​It beats continuously throughout your entire life to pump blood.

Multiple Choice

Which type of muscle is found only in the heart and is classified as involuntary?

• Cardiac muscle

• Skeletal muscle

• Smooth muscle

• Tendon muscle

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How Muscles Work

Muscle Pairs

• ​Muscles produce movement by contracting, which makes them shorter and thicker.

• ​​Since they can only pull and not push, muscles must work in pairs.

• ​When one muscle contracts, the other relaxes to allow the bone to move.

Types of Control

• ​Voluntary muscles are those you can control, such as when you smile or walk. eg Neck & Triceps

• ​​Involuntary muscles work automatically, like those for breathing and digesting your food eg. Heart & Cardiac muscles.

• ​Tendons are tissues that attach skeletal muscles to bones, letting you move.

Multiple Choice

Why must skeletal muscles work in pairs?

• Because muscles can only pull on bones by contracting, not push

• Because it makes the muscles stronger

• Because one muscle is voluntary and the other is involuntary

• Because tendons can only attach to two muscles at a time

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Common Misconceptions

Misconception	Correction
Bones are not living tissue.	Bones are living organs that are constantly broken down and rebuilt.
All muscles are controlled consciously.	Only skeletal muscles are voluntary; smooth and cardiac muscles are involuntary.
The number of bones is the same from birth to adulthood.	Humans are born with around 270 bones, which fuse to become 206.
Bones are only for structure and support.	Bones also produce blood cells and store essential minerals like calcium.

Multiple Choice

How does the primary function of the axial skeleton differ from that of the appendicular skeleton?

• The axial skeleton's main role is protection of organs, while the appendicular skeleton's is movement.

• The axial skeleton is for movement, while the appendicular skeleton is for protection.

• The axial skeleton produces blood cells, while the appendicular skeleton stores minerals.

• The axial skeleton is made of cartilage, while the appendicular skeleton is made of bone.

Multiple Choice

Why is the involuntary nature of cardiac and smooth muscle essential for survival?

• It ensures vital functions like heartbeat and digestion occur continuously without conscious effort.

• It allows you to run faster than you could with voluntary muscles.

• It prevents those muscles from ever getting tired.

• It makes those muscles stronger than skeletal muscles.

Multiple Choice

A patient's blood test shows dangerously low calcium levels. How would the body's specialized bone cells likely respond to restore mineral homeostasis?

• Osteoclasts would break down bone tissue to release calcium into the blood.

• Osteoblasts would absorb excess calcium from the blood and store it in the bones.

• Osteocytes would stop regulating mineral levels entirely.

• Osteoblasts would create new bone marrow to produce more calcium.

Multiple Choice

Analyze the relationship between skeletal muscles, bones, and tendons in producing movement. How does their interaction allow you to raise your hand?

• Your brain sends a signal, a skeletal muscle contracts, pulling on a tendon, which in turn pulls the bone of your arm upwards.

• The bone moves first, which then pulls the tendon and causes the skeletal muscle to contract.

• The tendon contracts, pulling the muscle and bone at the same time, which raises your arm.

• A skeletal muscle pushes on a tendon, which pushes the bone of your arm upwards.

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Summary

• The skeletal system provides support, protection, movement, stores minerals, and produces blood cells.

• The skeleton has two main parts: the protective axial and mobile appendicular skeletons.

• The muscular system uses skeletal, smooth, and cardiac muscles to enable movement.

• Muscles work in pairs by contracting and pulling on bones to create movement.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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