chapter 6 skeletal system

What are the main functions of the skeletal system?

Support, protection, movement, mineral storage, blood cell formation, fat storage, and hormone production.

What tissue type is cartilage made of?

Highly resilient, molded cartilage tissue that consists primarily of water.

What is the perichondrium?

A layer of dense connective tissue surrounding cartilage that helps resist outward expansion and provides nutrients.

What cells make up cartilage?

Chondrocytes.

What are the two types of cartilage growth?

Appositional and interstitial.

What is appositional growth?

Cartilage-forming cells in the perichondrium secrete matrix on the surface of existing cartilage.

What is interstitial growth?

Chondrocytes divide and secrete new matrix from within the cartilage.

What are the three types of cartilage?

Hyaline, elastic, and fibrocartilage.

Where is hyaline cartilage found?

Joints, ribs, larynx, and nose tip.

Where is elastic cartilage found?

External ear and epiglottis.

Where is fibrocartilage found?

Menisci of knee and vertebral discs.

What is hematopoiesis?

Blood cell formation occurring in red marrow cavities.

What is osteocalcin?

A hormone secreted by bones to regulate insulin secretion, glucose levels, and metabolism.

What are the organic components of bone?

Bone cells and collagen fibers.

What is the inorganic component of bone?

Hydroxyapatite.

What is compact bone?

Dense outer layer of bone that appears smooth and solid.

What is spongy bone?

Honeycomb-like bone with trabeculae and open spaces filled with red or yellow marrow.

What are the two membranes associated with bone?

Periosteum and endosteum.

What are the parts of a long bone?

Diaphysis, epiphysis, epiphyseal line.

Where is yellow marrow found in adults?

In the medullary cavity of the diaphysis.

What are bone markings used for?

Muscle, ligament, and tendon attachment; joint formation; and passage of vessels and nerves.

What are the three types of bone markings?

Projection, depression, and opening.

What are the four bone cell types?

Osteogenic cells, osteoblasts, osteocytes, osteoclasts.

What do osteogenic cells do?

They are stem cells that differentiate into osteoblasts or bone-lining cells.

What do osteoblasts do?

Form bone by secreting unmineralized matrix (osteoid).

What do osteocytes do?

Maintain bone matrix and act as stress sensors.

What do osteoclasts do?

Break down bone matrix for resorption.

What is an osteon?

The structural unit of compact bone.

What are lamellae?

Rings of bone matrix in an osteon with alternating collagen fiber directions.

What are lacunae?

Small cavities containing osteocytes.

What are canaliculi?

Hairlike canals that connect lacunae to each other and the central canal.

What is ossification?

The process of bone tissue formation.

What are the two types of ossification?

Endochondral and intramembranous.

What is endochondral ossification?

Bone forms by replacing hyaline cartilage.

What is intramembranous ossification?

Bone develops from fibrous membrane.

Where does the primary ossification center form?

In the diaphysis.

What forms the bone collar during endochondral ossification?

The periosteum.

What invades the cavities to form spongy bone?

Periosteal bud made of blood vessels, nerves, red marrow, osteogenic cells, and osteoclasts.

What remains as hyaline cartilage after ossification?

Epiphyseal plates and articular cartilage.

Where does intramembranous ossification begin?

Within fibrous connective tissue membranes.

What happens to trapped osteoblasts?

They become osteocytes.

What replaces immature spongy bone?

Mature spongy bone and compact bone.

What is required for interstitial growth?

Presence of epiphyseal cartilage.

What are the five zones of the epiphyseal plate?

Resting, proliferation, hypertrophic, calcification, and ossification zones.

What happens in the resting zone?

Cartilage is relatively inactive.

What happens in the proliferation zone?

Rapid cell division pushes epiphysis away from diaphysis.

What happens in the hypertrophic zone?

Older chondrocytes enlarge and their lacunae erode.

What happens in the calcification zone?

Matrix calcifies and chondrocytes die.

What happens in the ossification zone?

Spicules of cartilage are replaced with spongy bone by osteoblasts.