Unit 2
Lab6

Lab 6: The Integrated Musculoskeletal System

A. Overview

B. Long Bone Gross Anatomy

Each articulation functions anatomically because of two things:

  1. Bones whose interlocking shapes allow for the formation of a fulcrum, a part of a lever. There are often stabilizing structures such as ligaments and cartilage.
  2. Muscles that span the articulation. One point of bone attachment (via tendons) is called the origin and it is usually the more proximal attachment, while the other attachment point (usually distal to the articulation) is the insertion. When in anatomical position, the bone that has the insertion is normally the one that actually moves. This figure illustrates the biceps brachii, muscles that allow the elbow to flex. This would be the movement you would perform when doing arm curls. The origins of the biceps brachii are on the scapula (shoulder blade) and the insertion is on the radius, specifically the radial tuberosity.

Structure Descriptions:

  • Diaphysis: The shaft or main body of a long bone
  • Epiphysis: The end portions of long bones
  • Articular cartilage: Smooth cartilage covering the epiphysis where the bone forms joints
  • Epiphyseal plate/line: Growth region between epiphysis and diaphysis (becomes a line in adults)
  • Medullary cavity: Central cavity containing bone marrow
  • Compact bone: Dense outer layer of bone providing strength and protection
  • Spongy (cancellous) bone: Lighter, porous inner bone with honeycomb structure
  • Trabeculae: Bony plates forming the framework of spongy bone

C. Bone Surface Anatomy

Projections for Muscle/Ligament Attachment:

  • Tuberosity: Rough, rounded projection (Example: Radial tuberosity)
  • Crest: Ridge-like projection (Example: Iliac crest)
  • Trochanter: Large, blunt projection (Example: Greater trochanter of femur)
  • Tubercle: Small, rounded projection (Example: Greater tubercle of humerus)
  • Epicondyle: Projection above a condyle (Example: Medial epicondyle of humerus)
  • Spine: Sharp, pointed projection (Example: Spine of scapula)
  • Process: Any prominent projection (Example: Mastoid process)

Projections for Joint Formation:

  • Head: Rounded articular projection (Example: Head of femur)
  • Facet: Smooth, flat articular surface (Example: Vertebral facets)
  • Condyle: Rounded articular projection (Example: Femoral condyles)

Depressions for Muscle Attachment:

  • Fossa: Deep, broad depression (Example: Mandibular fossa)
  • Sulcus: Groove-like depression (Example: Bicipital sulcus)

Passages for Nerves and Vessels:

  • Meatus: Canal-like passage (Example: External acoustic meatus)
  • Foramen: Hole through bone (Example: Foramen magnum)

D. Bone Microscopic Structure

Key Features:

  • Osteon: Basic structural unit of compact bone
  • Osteocyte: Mature bone cell within lacuna
  • Central (Haversian) canal: Central canal containing blood vessels and nerves
  • Perforating canals: Canals connecting osteons
  • Concentric lamellae: Circular layers of bone matrix around central canal
  • Circumferential lamellae: Outer layers of compact bone
  • Interstitial lamellae: Fragments of old osteons
  • Lacuna: Small cavity containing osteocyte
  • Canaliculi: Tiny channels connecting lacunae
  • Endosteum: Inner bone membrane
  • Periosteum: Outer bone membrane
  • Perforating (Sharpey’s) fibers: Collagen fibers anchoring periosteum to bone

E. Skeletal Muscle Histology

Structure Descriptions:

  • Muscle fiber: Individual muscle cell
  • Endomysium: Connective tissue surrounding individual muscle fibers
  • Epimysium: Outer connective tissue covering entire muscle
  • Muscle fascicle: Bundle of muscle fibers
  • Perimysium: Connective tissue surrounding fascicles
  • Tendon: Dense connective tissue attaching muscle to bone
  • Aponeurosis: Broad, flat tendon
  • Neuromuscular junction: Connection between nerve and muscle fiber

H. Synovial Joint Structural Classes

Joint Class Movement Type Representative Joints Observations
Gliding (plane) Non-axial Intercarpal, intertarsal Limited sliding movement
Hinge Monaxial Elbow, knee, interphalangeal Movement in one plane like a door hinge
Pivot Monaxial Atlantoaxial, proximal radioulnar Rotation around single axis
Condyloid Biaxial Metacarpophalangeal, radiocarpal Egg-shaped surface allowing two planes of movement
Saddle Biaxial Carpometacarpal of thumb Reciprocal concave-convex surfaces
Ball-and-socket Multiaxial Hip, shoulder Greatest range of movement
Lab7