Skeletal System Anatomy: Cartilage, Bone Types, Markings, and Structure

Skeletal Cartilage Blood Supply

Contains no blood vessels or nerves.

Perichondrium

Dense irregular connective tissue surrounding skeletal cartilage that resists outward expansion.

Three Types of Skeletal Cartilage

Hyaline, elastic, and fibrocartilage.

Hyaline Cartilage Properties

Provides support, flexibility, and resilience; the most abundant skeletal cartilage.

Locations of Hyaline Cartilage

Articular (bone ends), costal (ribs to sternum), respiratory (larynx/air passages), and nasal cartilages.

Elastic Cartilage Characteristics

Similar to hyaline cartilage but contains elastic fibers; found in external ear and epiglottis.

Fibrocartilage Characteristics

Highly compressed with great tensile strength and collagen fibers; found in knee menisci and intervertebral discs.

Appositional Growth of Cartilage

Cells in the perichondrium secrete matrix against the external face of existing cartilage.

Interstitial Growth of Cartilage

Lacunae-bound chondrocytes inside cartilage divide and secrete new matrix, expanding it from within.

Cartilage Calcification Triggers

Occurs during normal bone growth and during old age.

Axial Skeleton

Bones of the skull, vertebral column, and rib cage.

Appendicular Skeleton

Bones of the upper and lower limbs, shoulder, and hip.

Long Bones

Bones longer than they are wide (e.g., humerus).

Short Bones

Cube-shaped bones of the wrist and ankle, and bones forming within tendons (e.g., patella).

Flat Bones

Thin, flattened, and curved bones (e.g., sternum and most skull bones).

Irregular Bones

Bones with complicated shapes (e.g., vertebrae and hip bones).

Five Major Functions of Bones

Support, protection, movement, mineral storage, and blood cell formation (hematopoiesis).

Tuberosity

A rounded projection of bone.

Crest

A narrow, prominent ridge of bone.

Trochanter

A large, blunt, irregular bone surface.

Line

A narrow ridge of bone.

Tubercle

A small rounded projection of bone.

Epicondyle

A raised area above a condyle.

Spine (Bone Marking)

A sharp, slender projection of bone.

Process (Bone Marking)

Any bony prominence.

Head (Bone Marking)

A bony expansion carried on a narrow neck.

Facet

A smooth, nearly flat articular surface.

Condyle

A rounded articular projection.

Ramus

An armlike bar of bone.

Meatus

A canal-like passageway in a bone.

Sinus

A cavity within a bone.

Fossa

A shallow, basinlike depression in a bone.

Groove

A furrow in a bone.

Fissure

A narrow, slitlike opening in a bone.

Foramen

A round or oval opening through a bone.

Compact Bone

The dense outer layer of bone.

Spongy Bone

A honeycomb of trabeculae filled with yellow bone marrow.

Diaphysis

Tubular shaft forming the axis of long bones, composed of compact bone surrounding the medullary cavity.

Epiphyses

Expanded ends of long bones with an exterior of compact bone and interior of spongy bone.

Periosteum

Double-layered protective membrane covering the outer surface of bone, secured by Sharpey's fibers.

Endosteum

A delicate membrane covering internal surfaces of bone.

Structure of Short, Irregular, and Flat Bones

Thin plates of periosteum-covered compact bone outside and endosteum-covered spongy bone inside.

Red Marrow Location in Infants

Found in the medullary cavity and all areas of spongy bone.

Red Marrow Location in Adults

Found in the diploë of flat bones, and the head of the femur and humerus.

Osteon (Haversian System)

The structural unit of compact bone.

Lamella

Weight-bearing, column-like matrix tubes composed mainly of collagen in compact bone.

Haversian (Central) Canal

Central channel in an osteon containing blood vessels and nerves.

Volkmann's Canals

Channels at right angles to the central canal connecting periosteum and Haversian supplies.

Lacunae

Small cavities in bone that contain osteocytes.

Canaliculi

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

Osteoblasts

Bone-forming cells.

Osteocytes

Mature bone cells.

Osteoclasts

Large cells that resorb or break down bone matrix.

Osteoid

Unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen.

Osteogenesis and Ossification

The process of bone tissue formation leading to skeletal formation, growth, and repair.

Intramembranous Ossification

Formation of flat skull bones and clavicles from fibrous connective tissue membranes formed by mesenchymal cells.