human anatomy lecture nine muscles. muscle functions body movement posture respiration and heart...
TRANSCRIPT
HUMAN ANATOMY
LECTURE NINE
MUSCLES
MUSCLE FUNCTIONS
• Body movement • Posture• Respiration and heart beat• Production of body heat - maintains body temperature• Communication - speaking, writing, gesturing, facial
and body language• Constriction of organs and vessels - helps food move
through digestive tract and blood flow• Protects and supports soft tissues• Storage of nutrients
PROPERTIES OF MUSCLE
• Contractility - ability of a muscle to shorten with force• Excitability - capacity of muscle to respond to a
stimulus• Extensibility - muscle can be stretched beyond its
normal resting length• Elasticity - ability of muscle to recoil to original resting
length after being stretched
TYPES OF MUSCLE• Skeletal Muscle
- voluntary muscle- responsible for movement, respiration, posture, facial
expressions• Smooth Muscle
- involuntary- around organs, blood vessels, glands, skin- controlled by endocrine and autonomic nervous system
• Cardiac Muscle- autorhythmic- only found in heart- controlled by endocrine and autonomic nervous system
SKELETAL MUSCLE
• Composed of muscle cells (fibres), connective tissue, blood vessels, nerves
• Fibres are long, cylindrical, multinucleated
• Smaller in diameter in small muscles and larger in larger muscles
• Striated appearance due to light and dark banding
SKELETAL MUSCLE STRUCTURE• Epimysium (fascia) - sheath surrounding
entire muscle
- holds muscle together and separates
them into groups
- allows freedom of movement
- carries nerves, blood vessels, lymphatic
vessels
- continuous with connective tissue of
tendons and periosteum
• Muscle Fasciculi - muscle bundles
- composed of several muscle fibres
- surrounded by connective tissue layer
called perimysium
• Endomysium - connective tissue surrounding individual muscle fibres
NERVE AND BLOOD SUPPLY
• Muscle cells are stimulated to contract by motor neuron axons at a neuromuscular junction (synapse)
• Axons are branched so that every muscle fibre is innervated
• Blood vessels and nerves enter the muscle together and follow the same branching pathway through the perimysium
• Within the endomysium arterioles branch into capillary beds surrounding each muscle fibre
SKELETAL MUSCLE CELLS (FIBRES)• Sarcoplasm - cytoplasm containing
numerous myofibrils
• Myofibril - thread-like structure extending length of muscle fibre
- made up of proteins (actin and
myosin myofilaments)
• Sarcomeres - repeating arrangment of actin and myosin
- smallest section of muscle capable
of contracting
• Sarcolemma - cell membrane surrounding a muscle fibre (cell)
• Sarcoplasmic reticulum - similar to smooth ER
- forms tubular network around each
myofibril
TRANSVERSE TUBULES
• Transverse tubules - narrow tubes continuous with sarcolemma extending into sarcoplasm at right angles to muscle fibre
- distributes signal (action potential) to contract through to interior of cell ensuring all cells contract simultaneously
• Terminal cisternae - thickening on either side of t-tubule
• Triad - terminal cisternae + t-tubule
ACTIN (THIN) FILAMENTS• Two strands (F-actin) of pearl-like
proteins (G-actin) form a double helix extending the length of the muscle fibre
• Thin strand of nebulin holds the F-actin together
• G-actin contains the active site that binds the myosin during muscle contraction
• Tropomyosin winds through the F-actin and covers the active sites
• Troponin protein found at the ends of the tropomyosin forming the tropomyosin/troponin complex - binds Ca+2 and changes position during muscle contraction
MYOSIN (THICK) FILAMENTS
• Each ‘club’ consists of two heavy myosin molecules wound together to form a rod portion lying parallel with heads that extend laterally
• Myosin ‘heads’
- bind to active sites on the active sites on the actin molecules to form crossbridges
- attach to the ‘rod’ portion by a hinge that bends and straightens during contraction
SARCOMERES
Repeating units of actin and myosin along the myofibril - smallest portion of muscle capable of contracting
• Z Line - network of protein fibres serving as attachment for actin
• I Band - actin filaments only (thin/light)
• A Band - length of myosin (thick/dark)
• H Zone - myosin only (lighter)
• M Line - myosin filaments are attached in center of H Zone
Alternating A and I Bands give muscle striated appearance
SMOOTH & CARDIAC MUSCLESmooth Muscle• Not striated, made up of
separate distinct cells with an obvious nucleus – less actin and myosin
• Contract more slowly with no oxygen dept
• Two types:(i) Multinuceate - cells operate independently (ie: iris of eye, blood vessels, erectile muscles of hair(ii) Visceral - cells operate together (ie: surrounding digestive tract, reproductive and excretory organs)
Cardiac Muscle
• Long, branching cells
• Cells are striated but less organized than skeletal muscle
• All cells work together as a single unit - autorhythmic contraction
• Cells do not develop oxygen dept or fatigue
• Connected by intercalated discs
GROSS MUSCLE ANATOMY
Most muscles extend from bone to bone and cross at least one joint• Tendons - attach muscle to bone
• Aponeuroses - broad, sheetlike tendon
Muscle terminology:• Origin/head - end of muscle attached to most stationary bone
• Insertion - end of muscle attached to bone with most movement
• Belly - largest area between origin and insertion
• Synergists - muscles that work together to cause a movement
- prime mover - plays major role in movement
- fixator - hold one bone in place while other bone is moved
• Agonist - muscle that causes an action when it contracts
• Antagonist - muscle working in opposition to agonist
MUSCLE ATTACHMENT
MUSCLE TYPES
MUSCLE SHAPES
MUSCLE NOMENCLATURE
Muscles are named according to:
• Location - pectoralis, gluteus, brachial
• Size - maximus, minimus, longus, brevis
• Shape - deltoid, quadratus, teres
• Orientation - rectus
• Origin and Insertion - sternocleidomastoid, brachioradialis
• Number of Heads - biceps, triceps
• Function - adductor, masseter
MUSCLE MOVEMENT• Muscles, their tendons and bones act together as lever systems to move
parts of the body
• Muscle contractions are a pull or force by relative positions of the:
lever - bone
fulcrum - joint
weight or resistance - force of gravity due to weight of body parts or
weight of object being moved
CLASSES OF LEVERS
Class I
• Fulcrum between force and weight
• See saw
• Head movement at the atlantooccipital joint
Class II
• Weight is between fulcrum and pull
• Wheelbarrow
• Standing on toes, metatarsophalangeal joint
Class III
• Pull located between fulcrum and weight
• Using a shovel
• Biceps brachii with elbow as fulcrum
BODY MOVEMENTS
Flexion vs ExtensionFlexion - moves body part in anterior or ventral direction
Extension - moves body part in posterior or dorsal direction
Plantar Flexion vs DorsiflexionPlantar Flexion - movement of foot toward plantar surface
ie: standing on toes
Dorsiflexion - movement of foot toward shin
ie: walking on heel
Abduction vs AdductionAbduction - movement away from midline
Adduction - movement toward midline
Medial vs Lateral RotationMedial Rotation - anterior surface of limb rotates toward
body
Lateral Rotation - anterior surface of limb rotates away from body
Pronation vs SupinationPronation - rotation of forearm so palm is down
Supination - rotation of forearm so palm is up
Elevation vs DepressionElevation - movement in superior direction
Depression - movement in inferior direction
Protraction vs RetractionProtraction - gliding part horizontally forward
Retraction - gliding part horizontally backward
CircumductionMovement in a cone/circular shape
Inversion vs EversionInversion - turning foot so plantar surface faces medially
Eversion - turning foot so plantar surface faces laterally
MUSCLE ANATOMYANTERIOR VIEW
MUSCLE ANATOMYPOSTERIOR VIEW
HEAD MUSCLES
Divided into groups by function:
Facial ExpressionOrigin and insertion in the superficial
fascia
When muscles contract the skin moves
• Orbicularis oris - around mouth
• Obicularis oculi - opens and closes
eyelids
Mastication (chewing)
Involves elevation/depression of mandible and excursion to grind the teeth together
Act with muscles of hyoid in movement of mandible
Muscles of cheek and tongue aid mastication by pushing food under the teeth
• Temporalis - lifts mandible
• Masseseter - largest jaw muscle
Muscles of the Hyoid
Tongue MovementsImportant in speech - changes shape
Swallowing
- moves food around in mouth
- holds food in place during
grinding
- pushes food up to palate and back
toward pharynx
Intrinsic - entirely within the tongue, allow tongue to change shape
Extrinsic - insert in tongue, allow shape change and movement
• Glossals – tongue muscles (genioglossus, hyoglossus, palatoglossus, styloglossus)
Eye Muscles
6 eye muscles originate on surface of the orbit and control movement of eyeball
• Extra-ocular eye muscles
NECK MUSCLESFlexion - muscles deep within neck
anterior margins of vertebral bodies
Extension - posterior neck muscles attached to occipital bone
Rotation and abduction - lateral and posterior muscle groups
• Sternocleidomastoid - from sternum to mastoid of skull, on either side of neck
• Trapezius - back of skull and upper vertebrae across to scapular spine
Posterior Deep Neck Muscles
Muscles of the Vertebral Column
Muscles that extend, laterally flex, and rotate the vertebral column - used to produce erect posture
Divided into deep and superficial groups
Deep - vertebrae to vertebrae
Superficial - vertebrae to ribs
THORACIC MUSCLES
Involved in breathing
• External Intercostals - elevate ribs during inspiration
• Internal Intercostals - contract and depress ribs during exhalation
• Diaphragm - flattens during contraction
- separates thoracic and abdominal
cavities
ABDOMINAL MUSCLES
Flex and rotate vertebral column, decrease volume of abdominal and thoracic cavities
Aid in forced expiration, vomiting, defecation, urination, childbirth
Crossing pattern of muscles adds strength to abdominal wall to support organs
• Rectus abdominus - inserts at xiphoid process down to pubic symphysis
• Internal and external abdominal obliques – flex and rotate abdomen
PERINEAL MUSCLESPelvic Diaphragm - funnel shaped,
supports the pelvic viscera- pierced by anal canal, urethra,
vaginaPerineum - diamond shaped area
inferior to pelvic diaphragm- divided into urogenital triangle and anal triangle regions
• Bulbospongiosus - base of penis or sides of vagina
• Levator ani - tenses pelvic floor, elevates and retracts anus
• Sphincter ani externus - around anus• Sphincter urethrae - around urethral
opening
ARM MUSCLES
Scapular MovementsMuscles that attach the upper limb to
the body and move or stabilize the scapula and clavicle
Originate on axial skeleton
• Trapezius - covers back, portion of neck and base of skull
• Rhomboid - attached to thoracic vertebrae and scapula posterior
• Levator scapulae - attached to cervial vertebrae and scapula
• Supraspinatus - scapula to humerus• Pectoralis minor - scapula to
thoracic ribs
Arm MovementsMuscles attach to arm and thorax
• Pectoralis major - humerus to superior thoracic vertebrae
• Latismus dorsi - humerus to lower thoracic vertebrae
Flexion and extension of shoulder
• Deltoid - across front of shoulder
- works with pectoralis
- abducts medially and rotates laterally
Rotator CuffPrimary muscles holding humerus in
glenoid cavity
Form cuff over proximal humerus
Involved in movement of the shoulder
• Supraspinatus - across scapula
Forearm MovementMovement at elbow:
Extension
• Triceps brachii - scapula to forearm
Flexion
• Biceps brachii - scapula to forearm
Wrist, Hand and Finger Movements
Muscles on anterior surface of forearm - flexion, abduction, adduction of the wrist
Muscles on posterior surface of forearm - extension and abduction
Flexors and Extensors of the Hand
LEG MUSCLES
Thigh Movement• Gluteus maximus - attached to
ilium, sacrum, coccyx
• Gluteus medius - iliac crest to greater trochanter of femur
• Adductor group - attach ischium
to femur
• Tensor fasciae latae - iliac crest to tibia
- thick band of connective tissue
- rotates hip and supports knee
Leg Movement• Quadriceps femoris - anterior surface of thigh
- extension at knee
- inserted by patellar tendon
• Sartorius - originates on edge of pelvis, crosses medially to insert on tibia and fibula
- flexes knee and hip, rotates thigh
• Hamstrings - posterior thigh muscle
Muscles that move leg
Lower Leg MovementDivided into 3 sections: anterior,
posterior, lateral
Anterior - extensors of foot and toes
• Tibialis anterior - front of shin
Posterior - flexors of foot
• Gastrocnemius - condyles of femur to calcaneal(Achilles) tendon to calcaneus, superficial position
• Soleus – fibula and tibia through calcaneal tendon to calcaneus, deep position
Movement of the FootAnalogous to muscles of hand but
also serve in support and locomotion
20 foot muscles flex, extend, abduct and adduct toes