The Skeleton - ASC101 Lecture Flashcards

Comprehensive vocabulary flashcards covering skeletal anatomy, bone classifications, cellular components, and structural features from ASC101.

Cortical bone

Also known as compact bone, it forms the hard outer exterior (cortex) of bone and accounts for approximately $80\%$ of total skeletal mass.

Trabecular bone

Also known as spongy bone, it is the low density interior layer accounting for approximately $20\%$ of total skeletal mass and contains red marrow.

Osteon

The fundamental, tube-shaped functional unit of compact bone consisting of a central canal surrounded by concentric lamellae and osteocytes inside lacunae.

Central (Haversian) canal

The central core channel of an osteon containing nerves and blood vessels that allow nutrients to flow.

Lamella

Concentric rings of calcified matrix that surround the central canal in an osteon.

Osteocytes

Long-lived bone cells residing in lacunae that maintain bone tissue, representing $90\%$ to $95\%$ of all cells in the skeleton.

Osteoblasts

Mononuclear cells responsible for building bone by secreting collagen and minerals.

Osteoclasts

Polynuclear cells responsible for breaking down bone tissue by secreting acids and enzymes.

Long bones

Elongated, cylindrical bones that support the body's weight and act as levers.

Epiphyses

The rounded ends of a long bone covered in articular cartilage, containing a cortical bone exterior and a trabecular bone interior.

Metaphyses

Transition zones between the epiphysis and diaphysis of a long bone containing the growth plate responsible for growth in length.

Diaphysis

The central tubular shaft of a long bone covered in periosteum that accommodates growth in width and houses the medullary cavity with yellow marrow.

Periosteum

A fibrous outer membrane covering the metaphyses and diaphysis of long bones that acts as an anchor, delivers blood supply, and mediates pain sensation.

Short bones

Roughly cube-shaped bones lacking a diaphysis that provide stability, support, and shock absorption, such as carpals and tarsals.

Bovine Carpal Joint

The wrist joint composed of proximal short bones—radial (R), intermediate (I), ulnar (U)—and distal short bones—fourth carpal (4) and fused second & third carpals (2+3).

Bovine Hock Joint

The ankle joint (tarsus) composed of the Talus (T), Calcaneus (C), Centroquartal (CQ), First Tarsal (T1), and Fused Second & Third Tarsals (T2+3).

Flat bones

Strong, plate-like bones with a sandwich-like structure (cortical -> trabecular -> cortical) that protect vital organs and offer wide surface areas for muscle attachment.

Sesamoid bones

Small, rounded bones embedded within tendons or muscles that feature a thin cortex with a dense trabecular core to increase mechanical advantage.

Irregular bones

Bones with complex, unique shapes featuring protruding bumps, ridges, and hooks that serve as precise leverage points (e.g., vertebrae, mandible, sacrum).

Axial skeleton

The division of the skeleton positioned along the central axis of the body, consisting of the skull, spinal column, ribs, and sternum.

Atlas (C1)

The first cervical vertebra, structured as a simple ring with no solid vertebral body, which forms a cup-and-socket connection with the occipital condyles to enable head nodding ('yes').

Axis (C2)

The second cervical vertebra featuring a specialized peg-like protuberance (dens) and large superior facets that permit head rotation ('no').

Thoracic vertebrae (T)

Spinal segments that connect directly to the ribs and feature prominent, long spinous processes on their dorsal side.

Lumbar vertebrae (L)

Spinal segments characterized by wide, flat lateral projections known as transverse processes.

Appendicular skeleton

The portion of the skeleton made up of the pectoral and pelvic girdles together with the forelimbs and hindlimbs.

Proximal

A directional term within the appendicular skeleton indicating a location closer to the central axial skeleton.

Distal

A directional term within the appendicular skeleton indicating a location farther away from the central axial skeleton.

Fetlock Joint

The joint located between the cannon bone (metacarpal/metatarsal) and the long pastern bone.

Pastern Joint

The joint located between the long pastern bone and the short pastern bone.

Coffin Joint

The joint located between the short pastern bone and the coffin bone.