Chapter 6: The Skeletal System

What is osteology?

The study of bones.

What structures make up the skeletal system?

Bones, cartilage, and ligaments.

What is the major support tissue of the body?

Bone tissue.

What are the major functions of the skeletal system?

Support, protection, movement, mineral storage, blood cell production, energy storage, hormone production, and detoxification.

How does bone provide support?

It forms a framework for the body and provides sites for muscle attachment.

How does the skeleton aid movement?

Skeletal muscles attach to and move bones.

What minerals are stored in bone?

Calcium and phosphate.

How does bone help maintain electrolyte balance?

By storing and releasing calcium and phosphate.

How does bone help maintain acid-base balance?

By absorbing or releasing alkaline salts such as calcium phosphate.

What is hematopoiesis?

The formation of blood cells.

Where does hematopoiesis occur?

In red bone marrow.

What is yellow bone marrow composed of?

Adipose tissue and scattered leukocytes.

What is the function of yellow bone marrow?

Energy storage.

What is osteocalcin?

A hormone that helps regulate insulin secretion and sugar homeostasis.

How does bone aid in detoxification?

By absorbing heavy metals from the blood.

How many bones are in the adult human skeleton?

206.

What are the two major divisions of the skeleton?

Axial skeleton and appendicular skeleton.

What is the axial skeleton?

Bones along the central axis of the body that provide support and protection.

What is the appendicular skeleton?

Bones of the extremities involved in movement.

What are the five types of bones based on shape?

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

What are long bones?

Bones that are longer than they are wide.

Why are long bones curved?

To increase strength and reduce fracture risk.

What is the diaphysis?

The shaft of a long bone.

What are epiphyses?

The ends of a long bone.

What covers the epiphyses?

Hyaline (articular) cartilage.

What is the function of articular cartilage?

Shock absorption and reducing friction.

What is the metaphysis?

The region where the diaphysis meets the epiphysis.

What is the epiphyseal plate?

A growth plate where cartilage is replaced by bone.

What is the periosteum?

A membrane covering the outer surface of bone.

What are the two layers of the periosteum?

Outer fibrous layer and inner osteogenic layer.

What is the outer fibrous layer of the periosteum composed of?

Dense irregular connective tissue.

What structures are found in the outer fibrous layer?

Blood vessels, nerves, and lymphatic vessels.

What does the inner osteogenic layer contain?

Elastic fibers, blood vessels, and bone cells.

What are the functions of the periosteum?

Bone growth, repair, development, and attachment of tendons and ligaments.

What are Sharpey's fibers?

Collagen fibers that anchor the periosteum to bone.

What are perforating fibers?

Sharpey's fibers that penetrate into bone.

What is the medullary cavity?

The hollow cavity within the diaphysis.

What does the medullary cavity contain?

Yellow bone marrow.

What can yellow marrow become during anemia?

Red bone marrow.

What is the endosteum?

A membrane lining the medullary cavity.

What cells are found in the endosteum?

Osteoprogenitor cells and osteoclasts.

What are short bones?

Cube-shaped bones.

What are examples of short bones?

Carpals and tarsals.

What is diploe?

Thin plates of spongy bone found inside certain bones.

What are flat bones?

Thin bones composed of two compact bone layers surrounding diploe.

What are examples of flat bones?

Skull bones, sternum, and ribs.

What are the functions of flat bones?

Protection and tendon/ligament attachment.

What are irregular bones?

Bones with complex shapes.

What are examples of irregular bones?

Vertebrae and some facial bones.

What are sesamoid bones?

Small bones embedded in tendons.

What is an example of a sesamoid bone?

The patella.

What is bone matrix composed of?

25% water, 25% collagen, and 50% mineral salts.

What mineral salts are found in bone matrix?

Calcium carbonate and calcium phosphate.

What is calcification (mineralization)?

Formation of new bone matrix through mineral deposition.

What is the role of collagen in bone matrix?

Providing strength.

What are osteoprogenitor cells?

Unspecialized stem cells that can become osteoblasts.

Where are osteoprogenitor cells located?

In the periosteum and endosteum near blood vessels.

What are osteoblasts?

Bone-forming cells that secrete new bone matrix.

What process do osteoblasts perform?

Osteogenesis.

What happens when osteoblasts become surrounded by matrix?

They become osteocytes.

What are osteocytes?

Mature bone cells.

What is the function of osteocytes?

Nutrient exchange and maintaining bone homeostasis.

What additional role do osteocytes have?

Monitoring bone stress and overload.

What are bone lining cells?

Cells that help maintain bone matrix health.

What are osteoclasts?

Bone-resorbing cells.

What is bone resorption?

The breakdown of bone matrix.

What process do osteoclasts use to destroy bone?

Osteolysis.

How do osteoclasts destroy bone?

By releasing acids and enzymes.

What structural feature increases osteoclast efficiency?

A ruffled border.

What are the two types of bone tissue?

Compact bone and spongy bone.

Where is compact bone found?

The outer layer of all bones and the diaphysis of long bones.

What is the structural unit of compact bone?

The osteon (Haversian system).

What are Haversian canals?

Central canals containing blood vessels and nerves.

What are lamellae?

Rings of mineralized bone matrix.

What are Volkmann's canals?

Horizontal canals containing blood vessels and nerves.

What are lacunae?

Spaces containing osteocytes.

What are canaliculi?

Tiny channels that transport nutrients and waste.

What is spongy bone composed of?

Trabeculae and spicules.

What are trabeculae?

Thin plates of bone in spongy bone.

What are spicules?

Thin rods supporting trabeculae.

Does spongy bone contain osteons?

No.

What fills the spaces between trabeculae?

Red bone marrow.

Where is spongy bone found?

Short bones, flat bones, irregular bones, and epiphyses of long bones.

What bones commonly contain spongy bone?

Sternum, ribs, skull, and vertebrae.

What are hemopoietic stem cells?

Stem cells that can develop into all blood cells.

How does blood enter the diaphysis of long bones?

Through nutrient arteries and nutrient foramina.

What arteries supply the epiphyses?

Epiphyseal arteries.

What is ossification?

Bone formation.

What are the two patterns of ossification?

Intramembranous and endochondral ossification.

What is intramembranous ossification?

Bone formation directly on fibrous connective tissue.

Is cartilage involved in intramembranous ossification?

No.

What bones form by intramembranous ossification?

Skull bones, mandible, and clavicle.

What are fontanelles?

Soft spots in the skull of infants.

What is endochondral ossification?

Bone formation over hyaline cartilage.

How do most bones form?

Through endochondral ossification.

What is chondrification?

Formation of cartilage before bone development.

What cells produce cartilage during endochondral ossification?

Chondroblasts.

What triggers ossification in cartilage?

Growth of a nutrient artery into the cartilage.

What is the first ossification center called?

Primary ossification center.

What are secondary ossification centers?

Ossification centers that form later near bone ends.