Muscle Types and Structure

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Questions and Answers

What type of muscle fiber arrangement is best described as resembling a feather?

  • Pennate (correct)
  • Unipennate
  • Fusiform
  • Bipennate

Which of the following muscles is an example of a strap-like muscle?

  • Rectus abdominus
  • Deltoid
  • Temporalis
  • Sartorius (correct)

What is the role of the length of muscle fibers in muscle action?

  • It affects the range of contraction and movement. (correct)
  • It is unrelated to muscle efficiency.
  • It determines the muscle's color.
  • It is only important for cardiac muscles.

What kind of muscle attachment involves an intermediate tendon with fleshy bellies on each side?

<p>Muscle to tendon (D)</p> Signup and view all the answers

Which of the following fibers are attached all around the tendon and classified as circumferential?

<p>Circumpennate fibers (B)</p> Signup and view all the answers

Which type of muscle fiber is characterized by rapid contraction and rapid fatigue?

<p>Pale fibers (D)</p> Signup and view all the answers

What is the main characteristic of cardiac muscle fibers?

<p>Striated and branching (B)</p> Signup and view all the answers

What type of muscle attachment involves a band of fibrous tissue through which two muscles fuse together?

<p>Fibrous raphe attachment (D)</p> Signup and view all the answers

Which statement correctly describes skeletal muscles?

<p>Striated, not branched, and voluntary (A)</p> Signup and view all the answers

Where are high myoglobin content red fibers predominantly found?

<p>In antigravity muscles (B)</p> Signup and view all the answers

Which type of muscle is primarily involved in moving the skin?

<p>Skeletal muscle (C)</p> Signup and view all the answers

What is a characteristic function of smooth muscles?

<p>Supplied by autonomic fibers (C)</p> Signup and view all the answers

What is true regarding muscle contractions and their attachments?

<p>The origin is always fixed during contraction (B)</p> Signup and view all the answers

Flashcards

Parallel Muscle Fibers

Muscle fibers are arranged parallel to the direction of force applied. This configuration maximizes shortening distance, allowing for large, sweeping movements.

Pennate Muscle Fibers

Muscle fibers are arranged at an angle to the direction of force applied. This configuration allows for greater force production, but less shortening distance.

Unipennate Muscle

A type of pennate muscle where fibers attach to one side of the tendon. This provides a strong pulling force in one direction.

Bipennate Muscle

A type of pennate muscle where fibers attach to both sides of the tendon. This allows for even stronger force production compared to unipennate.

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Muscle Action

The range of motion a muscle can produce when it contracts. It is affected by the length of the muscle fibers, the number of fibers, and the direction of the fibers.

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Pale Fibers

Muscle fibers that contract rapidly but fatigue quickly. Found in prime mover muscles, which initiate movement.

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Red Fibers

Muscle fibers that contract slowly but sustain contraction for a long time. Found in antigravity muscles, which maintain posture.

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Muscle Origin

The point of attachment of a muscle that remains fixed during contraction.

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Muscle Insertion

The point of attachment of a muscle that moves towards the origin during contraction.

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Direct Muscle Attachment

The type of muscle attachment where fleshy muscle fibers attach directly to bone.

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Tendinous Muscle Attachment

The type of muscle attachment where a tendon connects the muscle to bone.

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Muscle Attachment to Fascia

A specialized type of muscle attachment, where a muscle is attached to a sheet of fibrous tissue.

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Muscle Attachment to Skin

A type of muscle attachment found in facial muscles, where the muscle inserts directly into the skin.

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Study Notes

Muscle Types and Structure

  • Muscles comprise about half of body weight
  • Muscles have contractile ability
  • Classified into three types: smooth, cardiac, and skeletal

Smooth Muscles

  • Shape: Plane and spindle-shaped
  • Nerve supply: Involuntary autonomic fibers
  • Location: Walls of blood vessels and visceral organs

Cardiac Muscles

  • Shape: Striated and branched
  • Location: Heart
  • Nerve supply: Involuntary autonomic fibers

Skeletal Muscles

  • Shape: Striated, non-branching
  • Nerve supply: Voluntary, supplied by at least one somatic nerve
  • Attachment: Bony attachments, origin, and insertion
  • Blood supply: Receive blood supply from surrounding blood vessels

Types of Striated Muscles

  • Pale fibers: Rapid contraction and fatigue
  • Location: Prime mover muscles initiating movement
  • Red fibers: Sustained slow contraction, less prone to fatigue
  • Location: Anti-gravity muscles, maintain posture
  • Examples: Gastrocnemius (pale), Soleus (red)

Muscle Attachments

  • Muscles attach at both ends, with one end fixed (origin), the other approximating (insertion)
  • Origin tends to be proximal, insertion distal
  • Attachments can be to bone, fibrous raphe, deep fascia, aponeurosis, skin, cartilage, and intermediate tendons

Types of Muscle Attachments

  • Attachment to bone: Direct or via tendon
  • Attachment to fibrous raphe: Fused muscles (e.g., mylohyoid)
  • Attachment to deep fascia: E.g., tensor fascia lata
  • Attachment to aponeurosis: Flat tendon (e.g., external oblique)
  • Attachment to skin: Facial muscles
  • Attachment to intermediate tendon: Muscles with multiple bellies (e.g., digastric)
  • Attachment to cartilage: Muscles in the larynx (e.g., cricothyroid)

Skeletal Muscle Forms

  • Parallel fibers: Fibers run parallel to the line of pull

    • Strap-like: Sartorius
    • Quadrate: Quadratus femoris
    • Fusiform: Palmaris longus
    • Tendinous intersections: Rectus abdominis
  • Oblique fibers: Fibers run obliquely to the line of pull

    • Unipennate: One side of tendon, flexor pollicis longus
    • Bipennate: Two sides of tendon, rectus femoris
    • Multipennate: Multiple bipennate, deltoid
    • Circumpennate: Fibers around tendon, tibialis anterior
  • Non-pennate oblique fibers: Triangular (temporalis), Spiral (latissimus dorsi), Cruciate (masseter), Circular (orbicularis oculi).

Muscle Action

  • Factors impacting muscle action:
    • Fiber length
    • Number of fibers
    • Fiber direction

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