The Skeletal System

The Skeletal System

High School

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Learning Objectives

• Describe the five primary functions performed by the skeletal system.

• Identify different bone types and the main parts of a long bone.

• Explain the processes of bone development, growth, and its natural repair.

• Differentiate between the four main types of specialized bone cells.

Key Vocabulary

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Hematopoiesis

The process of blood cell formation, which occurs within the red bone marrow of the bones.

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Ossification

The natural process of bone formation where cartilage is replaced by bone tissue and calcium.

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Periosteum

A tough, protective outer membrane on bones that helps in bone repair and muscle attachment.

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Osteoporosis

A medical condition where bones become weak and brittle due to a significant loss of bone mass.

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Collagen

A key protein that provides a flexible and strong structural framework for the body's connective tissues.

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The Five Functions of the Skeletal System

• Provides a structural framework, supporting the body against the pull of gravity.

• Protects vital organs like the brain with the skull and the heart with ribs.

• Muscles pull on bones, which act as levers, to allow for body movement.

• Produces blood cells and stores important minerals like calcium for the body to use.

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Multiple Choice

Which function of the skeletal system involves bones and joints acting as levers to allow the body to move?

• Support

• Movement

• Protection

• Manufacturing

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Bone Classification and Anatomy

• Bones are a matrix of living cells and fibers with calcium deposits.

• They are classified by shape: long, short, flat, and irregular bones.

• A long bone’s shaft (diaphysis) is compact bone; the ends (epiphysis) are spongy bone.

• The epiphysis contains red marrow for blood cells and cartilage for joint cushioning.

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Multiple Choice

In a long bone, which part is the expanded end, composed mostly of spongy bone where blood cells are made?

• Compact bone

• Periosteum

• Diaphysis

• Epiphysis

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Bone Cells and Development

Bone Cells

• Osteogenic cells are stem cells that develop into osteoblasts, which are responsible for new bone formation.

• Osteocytes are mature bone cells that are essential for maintaining the bone matrix and its health.

• Osteoclasts are involved in resorption, which is the necessary process of breaking down bone tissue.

Bone Development

• Intramembranous bones, like those in the skull, develop directly from sheets of connective tissue.

• Most bones are endochondral bones, which form by replacing an existing cartilage model over time.

• Bone development is affected by nutrition (like Vitamin D), various hormones, and regular physical exercise.

Multiple Choice

Which type of bone cell is responsible for forming new bone tissue?

• Osteoblast

• Osteoclast

• Osteogenic Cell

• Osteocyte

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Bone Density Changes Over a Lifetime

• Maximum bone density is reached by age 25, declining after age 40.

• Osteoporosis is a significant loss of bone mass, weakening the bones.

• This makes bones prone to fractures, especially the less dense spongy bone.

• Elderly, petite white women are at the highest risk for this condition.

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Multiple Choice

According to the provided information, which statement about bone health is correct?

• Osteoporosis affects compact bone more than spongy bone.

• Osteoporosis is a condition that strengthens spongy bone.

• Bone loss typically begins after the age of 40.

• Maximum bone density is reached by age 40.

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Common Misconceptions About Bones

Misconception	Correction
Bones are not living tissue.	Bones are living tissues that constantly grow and change.
Bone growth stops completely after childhood.	Bone density increases until about age 25, and remodeling occurs throughout life.
Bones only store calcium.	Bones also store other important minerals like magnesium, sodium, and potassium.
Cartilage and bone are the same.	They are distinct tissues. Cartilage is more flexible and cushions joints.

Multiple Choice

How do the roles of ligaments and tendons differ within the skeletal and muscular systems?

• Ligaments connect bones to bones; tendons connect muscles to bones.

• Both connect bones to bones.

• Both connect muscles to muscles.

• Ligaments connect muscles to muscles; tendons connect bones to bones.

Multiple Choice

How do osteoblasts and osteoclasts work together to respond to regular physical exercise?

• Both cells work to break down bone to release calcium for energy.

• They do not have a role in the response to exercise.

• Osteoclasts build bone, and osteoblasts break it down, leading to weaker bones.

• Osteoblasts build bone, while osteoclasts break it down, leading to stronger, denser bones over time.

Multiple Choice

A patient has a diet severely deficient in Vitamin D. What is the most likely consequence for their skeletal system, considering the process of ossification?

• The absorption of calcium will be impaired, leading to weaker and softer bones.

• The joints will become more flexible due to increased cartilage.

• The production of red blood cells will increase significantly.

• Their bones will become stronger due to increased calcium storage.

Multiple Choice

Considering the skeletal system's dual functions of mineral storage and blood cell manufacturing, how might a severe, long-term calcium deficiency impact hematopoiesis?

• A lack of calcium directly stops the formation of red and white blood cells.

• The body may prioritize maintaining blood calcium levels by breaking down bone, potentially impacting the health of the bone marrow where hematopoiesis occurs.

• It will cause an overproduction of platelets to compensate for the weak bones.

• It will have no impact, as the two functions are entirely separate.

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Summary

• The skeletal system provides support, protection, enables movement, and makes blood cells.

• Bones are classified by shape as long, short, flat, or irregular.

• Long bones have a diaphysis (shaft) and an epiphysis (end).

• Bone tissue is maintained by osteoblasts, osteoclasts, osteocytes, and osteogenic cells.

• Bone development is influenced by nutrition, hormones, and physical exercise.

• Aging can lead to a decline in bone mass, causing osteoporosis.

Poll

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

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• 4