Muscle Tissue Classification Quiz

Classification of Muscle Tissue

• Muscle tissue classifications are based on function, position (morphology), and microscopic appearance
• Function
  • Voluntary controlled by the central nervous system
  • Involuntary controlled by the autonomic nervous system
• Position
  • Skeletal attached to bones
  • Cardiac found in the heart
  • Visceral found in internal organs
• Microscopic appearance
  • Striated has a striped appearance
  • Smooth appears smooth
  • Skeletal and cardiac muscle are both striated

Muscle Attachments, Shapes, and Functions

• Origin refers to the end of the muscle that remains stationary during movement
• Insertion refers to the end of the muscle that moves toward the origin during contraction
• Belly is the thickest part of the muscle
• Intermediate tendon divides a muscle into two bellies
• Tendinous inscriptions separate muscle fibers into compartments

Muscle Types

• Tendons are ribbon-like or rounded, short and stout, white fibrous tissues
• Aponeurosis is a flat, expanded tendon, sheet-like white fibrous tissue

Muscle Shapes

• Spindle-shaped or fusiform muscles are elongated with a central belly
• Sheet-like or planus muscles are broad and flat
• Biceps muscles have two heads
• Triceps muscles have three heads
• Quadriceps muscles have four heads
• Digastric muscles have two bellies
• Orbicularis or sphincter muscles are ring-shaped

Muscle Joint Involvement

• Uniarticular muscles cross only one joint and act on that joint
• Biarticular muscles cross two joints and act on both joints
• Polyarticular muscles cross more than two joints

Muscle Actions

• Extensor muscles increase the angle between bones
• Flexor muscles decrease the angle between bones
• Abductor muscles move a limb away from the midline
• Adductor muscles move a limb towards the midline
• Supinator muscles rotate the limb so the palm faces upwards
• Pronator muscles rotate the limb so the palm faces downwards
• Elevator muscles raise a body part
• Depressor muscles lower a body part
• Rotator muscles rotate a limb
• Sphincter muscles constrict an opening
• Dilator muscles widen an opening

Muscle Fiber Orientation

• Parallel muscles have fibers that run the length of the muscle
• Fusiform muscles have fibers that converge at the tendons
• Pennate muscles have short fibers attached obliquely to a central tendon
  • Unipennate muscles resemble a half-feather
  • Bipennate muscles resemble a complete feather
  • Multipennate muscles have multiple feather-like arrangements

Accessory Structures of Skeletal Muscle

• Fascia is a connective tissue that surrounds and supports muscles
  • Superficial fascia is a fatty layer directly under the skin
  • Deep fascia is a dense, strong layer located beneath the superficial fascia, covering muscles
• Synovial bursa are fluid-filled sacs located between structures that rub together
• Synovial sheath (vaginal sheath) are elongated bursae that wrap around tendons

Joints

• Types of joints
  • Fibrous joined by fibrous connective tissue
  • Cartilaginous joined by cartilage
  • Synovial (diarthrosis) most movable, characterized by a joint cavity

Cartilaginous Joints (Amphiarthrosis)

• Bones are united by fibrocartilage, hyaline cartilage, or a combination of both
• Have no joint cavity
• Allow limited or no movement
• Fibrocartilaginous joints (symphysis)
  • United by fibrocartilage
  • Allow limited movement
  • Examples: pelvic symphysis, intervertebral discs
• Hyaline cartilage joints (synchondrosis)
  • United by hyaline cartilage
  • No movement
  • Examples: epiphyseal plates in immature bone

Synovial Joints (Diarthrosis)

• Possess a joint cavity filled with synovial fluid
• Allow free movement
• Types of synovial joints
  • Simple joint formed by two articular surfaces
  • Composite joint formed by multiple articular surfaces

Structures of Synovial Joints

• Constant structures: essential for joint function
  • Articular surfaces are the surfaces of bones that come into contact
  • Articular cartilage is a smooth, hyaline cartilage that covers the articular surfaces
  • Articular capsule a fibrous capsule that encloses the joint
  • Joint cavity the space between the articulating bones
• Accessory structures: enhance joint function
  • Ligaments strong bands of fibrous tissue that bind bones together
  • Intra-articular plates of fibrocartilage plates of fibrocartilage located within the joint cavity
  • Marginal cartilage a ring of fibrocartilage that encircles the articular cavity

Synovial Fluid

• Secreted by the synovial membrane
• Acts as a lubricant and provides nutrients to cartilage

Classification of Synovial Joints

• Number of bones: simple or composite
• Axis of movement: uniaxial, biaxial, multiaxial
• Shape of articular surfaces: spheroidal, ellipsoidal, saddle, spiral, plane/gliding

According to Number of Bones

• Simple joint formed by two articulating bones
• Composite joint formed by more than two articulating bones

According to Axis of Movement

• Uniaxial joint: movement around a single axis
  • Hinge joint: allows flexion and extension
  • Pivot joint: allows rotation
• Biaxial joint: movement around two axes
  • Ellipsoidal joint: allows flexion/extension and abduction/adduction
• Multiaxial joint: movement around multiple axes
  • allows all types of movement

According to Shape/Form of Articular Surfaces

• Spheroidal (ball-and-socket) joint: allows free movement
  • Examples: shoulder joint, hip joint
• Ellipsoidal joint: allows flexion/extension, abduction/adduction, and a limited degree of rotation
  • Examples: atlanto-occipital joint
• Saddle joint: allows flexion/extension and abduction/adduction
  • Examples: carpometacarpal joint of the thumb, pastern joint
• Spiral (condylar) joint: allows flexion/extension
  • Examples: stifle joint, temporomandibular joint (TMG)
• Plane (gliding) joint: allows sliding movement
  • Examples: carpus, tarsus