Learn: Bone Structure and Function: Key Concepts for Biology Students

What is the primary type of tissue that makes up bone?

Connective tissue.

What are the major functions of bones?

Provide form, support and protection, allow movement, store calcium and phosphorus, and produce major cellular components of blood.

How do bones protect the body?

They protect major tissues and organs, such as the ribs protecting internal organs.

How do bones allow movement?

They provide structures that allow movement through forces generated by skeletal muscle contraction.

What minerals are stored in bones?

Calcium and phosphorus.

What is hematopoiesis?

The production of blood cells.

Where does hematopoiesis occur?

In red bone marrow.

What are the five types of bones?

Long, short, flat, irregular, and sesamoid bones.

What are long bones?

Bones with long shafts and often uniquely shaped ends that form complex joints.

What is an example of a long bone?

The femur.

What are short bones?

Cube- or box-shaped bones that function in coordinated groups.

What are examples of short bones?

Carpals and tarsals.

What are flat bones?

Relatively flat bones.

What is an example of a flat bone?

The sternum.

What are irregular bones?

Oddly shaped bones that may appear in groups.

What are examples of irregular bones?

Vertebral bones.

What are sesamoid bones?

Bones that develop in tendons close to joints.

What is an example of a sesamoid bone?

The patella.

What is compact bone?

Dense, solid bone tissue that forms much of the outer portion of bones and is found where large amounts of force are experienced.

What is spongy bone?

Cancellous bone containing open spaces partially filled by a network of fine, needle-like struts called trabeculae.

What are trabeculae?

Needle-like struts that form the three-dimensional network of spongy bone.

Why are bones not made entirely of compact bone?

An entirely compact bone would be excessively heavy.

What are the major parts of a long bone?

Diaphysis, epiphyses, articular cartilage, periosteum, medullary cavity, and endosteum.

What is the diaphysis?

The hollow shaft of a long bone.

What type of bone forms the walls of the diaphysis?

Compact bone.

What are the epiphyses?

The enlarged ends of a long bone.

What is the function of the epiphyses?

They form joints and provide areas for muscle attachment.

What is articular cartilage?

A thin layer of hyaline cartilage that covers and protects the articular surfaces of joints.

What is the periosteum?

A dense, white, fibrous membrane covering the exterior of a bone except at joint surfaces.

What is the medullary cavity?

The hollow space extending through the diaphysis of a long bone that contains bone marrow.

What is the endosteum?

A thin, fibrous membrane lining the medullary cavity and the spaces of spongy bone.

What is found in the medullary cavity?

Bone marrow.

What is found in the periosteum?

Bone-forming osteoblasts, bone-destroying osteoclasts, and blood vessels.

What is yellow marrow?

Bone marrow composed primarily of fat or adipose tissue.

What are the major parts of a flat bone?

An external table of compact bone, a layer of spongy bone, and an internal table of compact bone.

How is spongy bone arranged in a flat bone?

It is sandwiched between an internal and external table of compact bone.

What covers the outer surface of a flat bone?

The periosteum.

What lines the inner spaces of a flat bone?

The endosteum.

What fills the spaces of many flat bones?

Red bone marrow.

Which other bones have features similar to flat bones?

Short, irregular, and sesamoid bones.

What are the three basic components of bone tissue?

Cells, fibers, and extracellular matrix.

What is the mature bone cell called?

An osteocyte.

What is the most abundant protein in the body?

Collagen.

What makes bone different from many other connective tissues?

Its extracellular matrix is calcified.

What are the two major chemical components of bone matrix?

Inorganic salts and organic components.

What percentage of bone matrix is inorganic?

Approximately two-thirds.

What percentage of bone matrix is organic?

Approximately one-third.

What gives bone its hardness?

Inorganic mineral salts, particularly hydroxyapatite crystals.

What is hydroxyapatite?

A rock-like mineral crystal that provides hardness to bone.

What other mineral components are found in bone matrix?

Magnesium, sodium, sulfate, and fluoride.

What makes up the organic component of bone matrix?

Collagen fibers and a mixture of proteins and polysaccharides called ground substance.

What is the function of ground substance?

It provides support and adhesion for cellular and fibrous elements.

What is compact bone primarily organized into?

Cylindrical units called osteons or Haversian systems.

What percentage of the body's total bone mass is compact bone?

Approximately 80 percent.

What is an osteon?

The basic structural unit of compact bone.

What are the four structures of an osteon?

Lamellae, lacunae, canaliculi, and the central canal.

What are lamellae?

Concentric, cylinder-shaped layers of calcified bone matrix.

What are lacunae?

Small spaces filled with fluid where bone cells live.

What are canaliculi?

Very fine canals that radiate in all directions from the lacunae.

What is the central canal?

A canal running lengthwise through an osteon that houses blood vessels, lymphatic vessels, and nerves.

What is the purpose of canaliculi?

They provide connections between lacunae and help supply osteocytes with nutrients.

What is spongy bone made of?

Needle-like branches forming bony trabeculae.

How are trabeculae arranged?

They form a three-dimensional network and are arranged to enhance bone strength.

What are the three major types of bone cells?

Osteocytes, osteoblasts, and osteoclasts.

What are osteocytes?

Mature bone cells.

What are osteoblasts?

Bone-forming cells that secrete important organic components of the bone matrix.

Where are osteoblasts found?

In the inner layer of the periosteum.

What is the main function of osteoblasts?

To form new bone.

What are osteoclasts?

Cells that break down old bone by dissolving bone minerals.

What is the main function of osteoclasts?

Bone resorption or breakdown.

Why are osteoclasts important?

They remove old bone and release minerals such as calcium into the body when needed.

What is bone marrow?

A specialized type of soft connective tissue called myeloid tissue.

What is red bone marrow?

Bone marrow that produces blood cells.

Where is red bone marrow found?

In the medullary cavity of certain long bones and in spaces of spongy bone.

What happens to red bone marrow as we age?

It gradually decreases and is replaced by yellow marrow.

What is yellow bone marrow?

Bone marrow saturated with fat that can no longer produce blood cells.

What happens to bone marrow in infants and children?

All bone marrow is red marrow.

What happens to some yellow marrow during certain disease processes such as anemia?

It can be converted back to red marrow.

What is a bone marrow transplant?

A potentially lifesaving treatment when bone marrow is severely damaged and cannot perform its functions.

Approximately what percentage of the body's calcium reserves are stored in bones?

Nearly 98 percent.

Why is calcium homeostasis important?

Calcium is essential for bone formation and reformation, blood clotting, transmission of nerve impulses, and skeletal and cardiac muscle contraction.

What hormones regulate blood calcium levels?

Parathyroid hormone and calcitonin.

What does parathyroid hormone do to blood calcium levels?

It increases blood calcium levels.

When is parathyroid hormone released?

When blood calcium levels are too low.

How does parathyroid hormone increase blood calcium?

It stimulates osteoclast activity, increasing bone breakdown and releasing calcium into the blood.

Where is parathyroid hormone produced?

By the parathyroid glands.

What is calcitonin?

A hormone produced in response to high blood calcium levels.

What does calcitonin do?

It stimulates bone deposition by osteoblasts and inhibits the bone-dismantling activity of osteoclasts.

When is calcitonin released?

When blood calcium levels are high.

Where is calcitonin produced?

By the thyroid gland.

How does calcitonin affect osteoclasts?

It inhibits their bone-dismantling activity.

How does the skeleton act as a calcium "bank"?

It stores calcium that can be deposited into or removed from bone to help regulate blood calcium levels.

What is bone remodeling?

The ongoing balance between bone formation and bone destruction.

Why is bone remodeling important?

It allows bones to grow, increases marrow capacity, and helps maintain calcium homeostasis.

What are the two types of bone growth?

Interstitial growth and appositional growth.

What is interstitial growth?

Growth that increases the length of a bone.

Where does growth in length occur?

At the epiphyseal plate.

What happens during growth in length?

Cartilage increases at the epiphyseal plate and then becomes ossified, increasing the length of the diaphysis.

What is the epiphyseal plate?

The growth plate and an ossification center involved in increasing bone length.

What is appositional growth?

Growth that increases the diameter of a bone.