Lecture 5 materials - Myology Flashcards
What are the functions of muscles?
Movement of the body, movement of substances inside the body, glycogen sotrage
Is it true or false that only muscles are the only tissue with the ability to contract
True
Name the 3 types of muscle tissue
Smooth, cardiac, striated
Describe smooth muscle
Visceral, unstriated, involuntary muscle
Specialized for slow and steady contractions
Muscle cells are spindle-shaped, mono-nucleated and innervated by the General Visceral Efferent nerve
Name locations of smooth muscle
Hair follicles, walls of hollow organs, blood vessel walls, glands, capsule of the spleen in dogs, muscles of iris (eye)
Describe cardiac muscle
Forms the bulk of the heart
Muscle cells are branched with centrally located nuclei and intercalated discs.
Muscle cells are striated and innervated by General Visceral Efferent nerve
Describe skeletal muscle
Accounts for 40% of body weight
Attached to bone
Striated, somatic, voluntary muscle
Muscle cells are multinucleated, arranged in to bundles with nuclei seen peripherally
Innervated by somatic motor neuron
What is the connective tissue located on all skeletal muscle?
Epimysium
Epimysium is continuous with the fascia and tendons
What is a fascicle?
A bundle of muscle fibers
What is the perimysium?
Connective tissue that surrounds each fascicle
What is connective tissue that surrounds each muscle fiber (cell)?
Endomysium
What is the muscle fiber made of?
Myofibrils
What is a myofibril composed of?
Sarcomeres (Action, myosin) separated by Z discs
What connects muscle to bone?
Tendons, aponeuroses
What type of attachment is muscle directly to periosteum?
Fleshy
What is an example of a fleshy attachment?
Serratus ventralis muscle attaches directly to the serrated face of the scapula
What are tendons composed of?
Collagen fibers
Describe the arrangement of a tendon
Much like muscle fibers
A group of fibers creates a primary bundle (subfascicle)
A group of subfascicles forms a secondary bundle (fascicle)
A group of secondary bundles forms a tertiary bundle
What connective tissue surrounds individual tendon fibers?
Endotendon envelopes the subfascicle
What is epitenon?
The connective tissue that surrounds the entire tendon
What is paratenon
Paratenon surrounds the epitenon
Describe a tendon
Similar in strength to bone
Damaged by excessive friction or pressure (changing direction over bony prominence)
Name the protective mechanisms for tendons
Sesamoid bones occur at bony prominences to ease tendon pressure and friction
Synovial fluid eases friction
What is a synovial bursae?
A flat sac of synovial fluid that facilitates the movement of a tendon over bone
What are the 2 types of bursae?
Congenital bursae - present at birth; calcanean bursa
Induced bursa - not present at birth; developed due to outside pressure
Describe sesamoid bones
Imbedded in certain tendons or joint capsules
Usually present at birth, sometimes develop due to friction
What is the function of sesamoid bones?
Protect tendons that pass over bony prominences
Increase surface area for tendon attachment over joints
Patella
Describe the tendon sheath
Elongated bursa that the tendon sinks in to
What is the internal layer of the tendon sheath called?
Visceral layer, its attached to the tendon
Synovial sheath
What is the parietal layer?
External layer that is connected to the periosteum
What connects the visceral and parietal layers?
mesotendon
Mesotendons provide vascular and sensory nerve supply
What does aponeurosis mean literally?
Apo- ‘from’
Neuron ‘tendon’
Connective tissue spreading from tendon
What is fascia?
Connective tissue that encloses muscle or organ
Describe superficial fascia
Associated with the dermis of the skin
Contains cutaneous muscles (cutaneous trunci muscle)
Describe deep fascia
Covers and separates muscles by forming a sleeve.
Consists of mesh-like sheet composed of mostly collagen fibers that are oriented in the same direction as the tension and stress forces
Clinical relevance of deep fascia?
Deep fascia serves as attachment site for muscles
Deep fascia holds sutures well compared to muscles
Allows for fairly bloodless separation of muscles
Inflammation or swelling of a muscle, or fluid accumulation will compress other structures in the compartment
Direct drainage of fluids will spread infection
What is the regional thickening of deep fascia?
Retinacula
Give examples of retinaculum
Flexor retinaculum, extensor retinaculum, (proximal, distal, palmer) annular ligaments
What does retinaculum literally mean?
‘that which binds’
‘band’
Describe a spindle shaped muscle
Passive head at muscle origin, active muscle belly in the middle, passive tail at insertion
Where does contraction occur within the muscle?
In the muscle belly
Name examples of spindle shaped muscles
Biceps (two-heads)
Triceps (4 heads)
Quadriceps (4 heads)
Describe pennate muscles
Muscle fibers lie oblique (slanting) to the line of muscle force
Describe a unipennate muscle
Al muscle fibers lie on the same side of the tendon
Extensor digitorum muscle
Describe a bipennate muscle
Muscle fibers lie on both sides of the tendon
Rectus femoris
Describe a multipennate muscle
The tendon branches within the muscle
Name all muscle forms
Pennate (deltoid), spindle shaped (biceps), sphincter, wide with tendinous tissue (abs), circular (eye), wide with aponeuroses
What is a motor unit?
One motor neuron and all muscle fibers are a motor unit
Every muscle fiber is innervated by a lower motor neuron, and a single neuron can innervate many muscle fibers.
Alpha lower motor neuron that causes skeletal muscles to contract
Can muscle fibers contract independently from each other?
No, all or no muscle fibers contract
What determines the force of a muscle contraction?
The size of the motor unit.
A small motor unit is a single neuron innervating a few muscle fibers
A large motor unit is a single neuron innervating several hundred muscle fibers
Motor units are activated from small to large
What is the purpose of the muscle spindles?
Provide feedback on muscle length
What is the purpose of the golgi tendon organs
Provide feedback on muscle tension
What is the patellar reflex?
Tapping on the patellar ligament stretches the musculotendinous junction which stimulates the muscle spindle and results in a contraction of muscle
What is hypertrophy?
Enlargement of muscle fibers (increase in contractile proteins)
Results in increased muscle mass
What is atrophy?
decrease is size or shrinking of muscle fibers (loss of contractile proteins)
Caused by disuse or neurogenic atrophy (denervation)
What is the relationship between muscles, tendons and joints?
If a muscle or tendon crosses a joint, when the muscle contracts, the joint will move
Flexion, extension, adduction, abduction, rotation, circumduction
What is flexion?
Angle of flexor surface “folding”
What is extension?
Straightening of the flexor surface
What is a muscle agonist?
Any muscle capable of producing a designated action on a joint
(Abs during a crunch, any muscle that flexes the shoulder joint)
What is a muscle antagonist?
Any muscle that has the opposite action as a flexor on a joint (brachialis vs triceps)
What is a fixator?
Any muscle that stabilizes joints while agonists are acting (rhomboideus)
What is a synergist?
Any muscle that stabilizes intermediate or proximal joints and enables the force of the prime mover to be exerted on a more distal joint (bices brachii)
Can a muscle be both an agonist and antagonist?
Yes.
Triceps is agonist for elbow extension but antagonist for elbow flexion
Biceps brachii and brachialis is agonist for elbow flexion but antagonist for elbow extension
