Myology Overview and Muscle Types

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Questions and Answers

What is the structural unit of muscle?

Muscle Fiber (correct)

Fascicle

Epimysium

Tendon

Which connective tissue layer ensheathes the entire muscle?

Endomysium

Perimysium

Fascia

Epimysium (correct)

What is an intermediate tendon?

A segment of the muscle that lacks both origin and insertion (correct)

A structure that connects muscle to cartilage

A tendon that connects muscle to skin

A tendon that has no attachment to bone

Which of the following structures protects muscle cells and provides passage for vessels and nerves?

Epimysium Signup and view all the answers

Which of the following best describes the 'belly' of a muscle?

The main bulk of muscle between the origin and insertion Signup and view all the answers

Which layer of connective tissue surrounds each muscle fiber?

Endomysium Signup and view all the answers

What is the process by which muscle fibers are innervated?

Motor unit activation Signup and view all the answers

Which of the following muscle attachments is characterized by direct attachment to the skin or superficial fascia?

Skin and superficial fascia Signup and view all the answers

What is the primary function of skeletal muscles?

Voluntary somatic movement of the body Signup and view all the answers

Which characteristic describes irritability in muscle tissue?

Responsiveness to chemical, electrical, or mechanical stimuli Signup and view all the answers

What type of muscle is characterized by being uni-nucleate and non-striated?

Smooth muscle Signup and view all the answers

Which component distinguishes cardiac muscle from the other types?

Striations and intercalated disks Signup and view all the answers

How much of the body's weight do skeletal muscles constitute?

40-45% Signup and view all the answers

What type of control do skeletal muscles operate under?

Voluntary control Signup and view all the answers

What characteristic is NOT associated with smooth muscles?

Striated appearance Signup and view all the answers

Which of the following describes the extensibility of muscle tissue?

The ability to be passively stretched Signup and view all the answers

Which type of muscle fiber arrangement involves fibers that run parallel to the line of pull?

Fusiform fibers Signup and view all the answers

What is the function of synergist muscles?

To facilitate motion by assisting agonist muscles Signup and view all the answers

What characterizes unipennate muscle fibers?

They attach to one side of a tendon Signup and view all the answers

What are the primary components of a motor unit?

One neuron and multiple muscle fibers Signup and view all the answers

Which accessory structure of skeletal muscle serves to reduce friction on tendons?

Sesamoid bones Signup and view all the answers

How do antagonist muscles function in relation to agonist muscles?

They have the opposite action to agonists Signup and view all the answers

Which muscle fiber arrangement is characterized by muscle fibers attached to multiple fibrous bands?

Multipennate Signup and view all the answers

What is typically found in the belly of skeletal muscle regarding blood supply?

It is more vascular than tendon Signup and view all the answers

Study Notes

Myology

Myology is the science that deals with muscles.
Skeletal muscles are the active component of the locomotor system.
Smooth muscles move the visceral organs.
Cardiac muscle contracts the heart.

Muscle Characteristics

Irritability/Excitability: muscles respond to chemical, electrical, or mechanical stimuli.
Contractility: muscles can shorten.
Extensibility: muscles can stretch.
Elasticity: muscles return to their original length.

Smooth Muscle

Structure: spindle-shaped, single-nucleus, non-striated.
Location: walls of visceral organs.
Control: involuntary, controlled by autonomic nervous system or endocrine system (myoepithelial cells).
Function: involuntary contractions to move materials through organs.

Cardiac Muscle

Structure: cylindrical, mostly single-nucleus, striated, branching, forming a network (syncytium). Connected via intercalated disks.
Location: heart wall.
Control: involuntary, with an intrinsic conduction system.

Skeletal Muscle

Structure: elongated, multinucleated, striated. Divided into bundles/fascicles. Each fascicle is comprised of numerous muscle fibers.
Percentage of body weight: 40-45%.
Location: throughout the body, forming the active part of the locomotor system.
Control: voluntary.

Skeletal Muscle Function

Voluntary body movements.
Maintaining posture.
Stabilizing joints.
Generating heat.
Guarding body openings and orifices.

Skeletal Muscle Architecture

Each muscle is a group of bundles called fascicles.
Each fascicle is a group of muscle fibers (cells).
Muscle fiber is the structural unit of muscle.

Skeletal Muscle Architecture Components

Epimysium: connective tissue sheath surrounding the entire muscle.
Perimysium: connective tissue sheath surrounding fascicles.
Endomysium: connective tissue sheath surrounding individual muscle fibers.
Tendon and Aponeurosis: connect muscle to bone.

Microscopic Muscle Structure

Myofibril: contractile thread within muscle fiber.
Sarcomere: functional unit of myofibril, bounded by Z-lines.
Myofilaments: filaments within sarcomere (actin & myosin).

Gross Anatomy of Skeletal Muscle

Origin: usually the proximal, less movable attachment of the muscle.
Insertion: usually the distal, more movable attachment of the muscle.
Belly: the main part of the muscle between the origin and insertion.

Skeletal Muscle Attachments

Bone
Cartilage
Deep fascia
Skin and superficial fascia
Intermediate tendon
No attachment (e.g., orbicularis oris)

Skeletal Muscle Fiber Arrangements

Parallel fibers (e.g., strap muscles, quadratus muscles).
Fusiform fibers (bundles running nearly parallel).
Oblique fibers (pennate): unipennate (one side), bipennate (both sides), multipennate (multiple attachments).
Circular fibers (e.g., orbicularis oris).
Convergent fibers (e.g., pectoralis major).

Functional Types of Muscles

Prime mover (agonist): muscle primarily responsible for producing a movement.
Antagonist: muscles that oppose the action of the agonist.
Synergist: muscles that assist the prime mover.
Fixator/stabilizer: muscles that stabilize a joint to allow movement of another part of the body.

Blood and Nerve Supply

Vessels and nerves pass through connective tissue sheaths.
Muscle belly is highly vascular.
One neuron can innervate multiple muscle fibers. (Motor units)
Each motor unit contracts together.

Neuromuscular Junction

Motor neurons connect to muscle fibers at the neuromuscular junction.
Neurotransmitters (e.g., acetylcholine) are released to initiate muscle contraction.

Accessory Structures of Skeletal Muscle

Sesamoid bones: embedded within tendons (e.g., patella).
Fascia: connective tissue sheath covering the body and individual muscles.
Synovial sacs: fluid-filled sacs between structures, decreasing friction.
Tendon synovial sheath: double-layered sheath surrounding tendons reducing friction.

Retinaculum

Transverse band of deep fascia surrounding joints (carpal, tarsal).
Holds tendons and ligaments in place.

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Description

Explore the fascinating science of myology, the study of muscles. This quiz covers the characteristics, structures, and functions of skeletal, smooth, and cardiac muscles. Test your knowledge on muscle types and their roles in the locomotor system and visceral organs.