ANATOMY & PHYSIOLOGY Midterms PDF

ANATOMY & PHYSIOLOGY LEC / PROF. BERNARD S. BARRANCO, RN, MAN ______________________________________________________________________________________________________________ MIDTERMS OUTLINE...

ANATOMY & PHYSIOLOGY LEC / PROF. BERNARD S. BARRANCO, RN, MAN ______________________________________________________________________________________________________________ MIDTERMS OUTLINE K. Muscles for Ankle and Foot Movement IV. Muscle Origin, Insertion, Action Reference I. The Skeletal System (cont.) V. The Nervous System A. Appendicular Skeleton A. Functions of the Nervous System B. Bones of the Shoulder Girdle B. Organization of the Nervous System C. Bones of the Upper Limb C. Functional Classification of Nervous D. Bones of the Pelvic Girdle System E. The Pelvis D. Structures and Functions F. Bones of the Lower Limbs E. Parts of a Neuron G. Joints F. Types of Neuron H. Functional Classification of Joints G. Nerve Properties Related to Function I. Inflammatory Conditions Associated H. Resting Membrane Potential with Joints I. Generating Action Potentials II. The Muscular System J. Neuromuscular Junction A. Functions of the Muscular System K. Reflexes B. Three Types of Muscular Tissue VI. The Central Nervous System C. Skeletal Muscle Fibers A. Brain D. Organization of Muscle Tissue B. Regions of the Brain E. Skeletal Muscle Arrangement C. Cerebrum F. Structure and Organizational Levels of D. Corpus Callosum Skeletal Muscle E. Cerebral Cortex G. Sarcomere Arrangement F. Diencephalon H. Sarcomere Structure G. Brain Stem I. Thick Filament Structure H. Cerebellum J. Thin Filament Structure I. Protector of the Nervous System K. Physiology of Skeletal Muscle VII. The Peripheral Nervous System Contraction: Neurotransmitter Release A. Cranial Nerves L. Sliding Filament Theory B. Spinal Nerves M. Phyisology of Skeletal Muscle C. Autonomic Nervous System Contraction: Power Stroke VIII. References N. Phyisology of Skeletal Muscle IX. Trans Authorship Contraction: Depolarization O. Lever Systems P. Muscle Attachments I. THE SKELETAL SYSTEM (cont.) Q. Basic Body Movement R. Interaction of Skeletal Muscles on the A. APPENDICULAR SKELETON Body Consists of 126 BONES S. Names of Skeletal Muscles Limbs (appendages) T. Arrangement of Fascicles Pectoral (shoulder) girdle U. Muscles of the Face Pelvic girdle - weight bearing, connected on the lower V. Muscles of the Head extremities W. Muscles of Mastication X. Eye Muscles B. BONES OF THE SHOULDER GIRDLE Y. Muscles of the Neck Composed of two bones Z. Muscles of the Trunk ○ Clavicle - “collarbone” III. The Muscular System (Upper and Lower Limb) ○ Scapula - “shoulder blade” A. Prime Movers of the Arm These bones allow the upper limb to have exceptionally free B. Muscles that Move the Forearm movement due to the following factors: C. Muscles of the Scapula ○ Each shoulder girdle attaches to the axial skeleton at only D. Muscles of the Rotator Cuff one point, the sternoclavicular joint. E. Muscles that Move the Lower Limb ○ The loose attachment of the scapula allows it to slide F. Muscles of the Hip Joint back and forth against the thorax as muscles act. G. Muscles for Knee Movement ○ The glenoid cavity is shallow, and the shoulder joint is H. Hamstring Group poorly reinforced by ligaments. I. Sartorius The collarbone is the most commonly broken bone among J. Quadriceps children. BSN1-A | 1  ○ It usually occurs by falling on an outstretched arm. Acromioclavicular Joint - where the acromion connects with the clavicle laterally. Glenoid Cavity ➔ shallow socket that receives the head of the humerus. Suprascapular Notch ➔ where nerves pass through. Superior Angle and Subscapular Fossa - where muscles of the chest are inserted into. 2 PROCESSES OF THE SCAPULA Acromion Process ➔ enlarged lateral end of the spine Coracoid Process - “beaklike” ➔ points laterally over the top of the shoulder ➔ anchors some muscles of the arms C. BONES OF THE UPPER LIMB The Arm The arm is formed by a single bone CLAVICLE Humerus A slender bone that connect parts of the anterior thorax ➔ Head of humerus allows for rotation The clavicle acts as a brace to hold the arm away from the 2 Tubercles of the Humerus top of the thorax and prevent shoulder dislocation. Greater tubercle of the humerus ○ Medial (sternal) end - connected on the manubrium Lesser tubercle of the humerus (head of the sternum) ○ Clavicular notch - where the medial end of the Anatomical Neck - a slight constriction immediately clavicle sits on inferior to the head. ○ Lateral (acromial) end - directly connected to the Surgical neck (the line) - common site of fracture or acromion; connected by the acromioclavicular joint. breakage of the humerus Deltoid Tuberosity ➔ Just below the surgical neck ➔ Where deltoid muscles are attached ➔ Deltoid muscle is the largest arm muscle ◆ Site of intramuscular injection. Capitulum & Trochlea - parts that are being connected to the forearm. Coronoid fossa - has a depression wherein the part of the ulna is connected. Radial groove ➔ runs obliquely down the posterior aspect of the shaft. ➔ where radial nerve passes on. SCAPULA Sometimes called the “wing” because they flare when we move our arms posteriorly. Each scapula has a flattened body with three borders: superior, medial, lateral It also has three angles: superior, inferior, lateral Shoulder joint is poorly reinforced by LIGAMENTS. Acromion ➔ where the lateral end of the clavicle is connected to. ➔ enlarged lateral end of the spine of the scapula BSN1-A | 2  The Hand The Forearm Carpals (8) - wrist Has two bones: ○ Scaphoid bone - one of the biggest bones in the Ulna carpal. ➔ the longer of the two forearm bones ○ Lunate ➔ located on the medial or little finger side of the ○ Triquetral forearm. ○ Pisiform - smallest bone in the carpal. ○ The Olecranon process consists of the bone of the ○ Trapezium proximal ulna from the base of the coronoid process ○ Trapezoid proximally. ○ Capitate ○ Hamate Metacarpals (5) - palm Phalanges (14) - fingers ○ Distal - the thumb doesn’t have a distal phalange. ○ Middle ○ Proximal D. BONES OF THE PELVIC GIRDLE Radius ➔ located on the lateral or thumb side when the palm of the hand is facing forward ➔ The head of the radius forms a joint with the capitulum of the humerus. ○ Styloid Process ➔ Articulated on the wrist ○ Radial Tuberosity ➔ Articulated near the proximal radioulnar joint. ➔ Where tendons of the bicep muscles attaches, Composed of two coxal bones (hip bones) Radioulnar joint - where both proximally and distally the ○ Composed of three pairs of fused bones radius and ulna articulate. Ilium Interosseous Membrane - Connects the two bones. Ischium Pubis *Arms are among the most commonly broken bones, The total weight of the upper body rests on the pelvis accounting for almost half of all adults’ broken bones. Protects several organs ○ Reproductive organs ○ Urinary bladder ○ Part of the large intestine NOTE: pelvic girdle and pelvis have slightly different meanings. Pelvic girdle comprises the coxal bones and the sacrum. Pelvis comprises the coxal bones, sacrum and coccyx. Ilium Connect posteriorly with the sacrum. Large flaring bone that forms most of the hip bone “Alae” – wing like portion of ilium Sacroiliac joint - the one that joints the ilium and part of the sacrum. BSN1-A | 3 Ischium (Sit down bone) F. BONES OF THE LOWER LIMB Ischial tuberosity – receives body weight when in a sitting position Ischial spine – superior to the tuberosity. Narrows the outlet of the pelvis Pubis The most anterior and inferior part. Forms in the fusion of Rami of the pubis Obturator foramen – opening that allows blood vessels and nerves to pass into the anterior part of the thigh. Pubic symphysis – pubic bones of each hip articulate anterior to form a cartilaginous joint. *During birth, the baby passes through the pelvic brim. E. THE PELVIS The Thigh The thigh has one bone: Femur - thigh bone ➔ longest, heaviest, and strongest long bone of the human body. ➔ Its proximal end has a ball-like head, a neck, and a greater trochanter and lesser trochanter, separated anteriorly by the intertrochanteric line and posteriorly by the intertrochanteric crest. ○ Lateral and Medial Condyle ➔ distal on the femur ACETABULUM - Deep socket formed by the fusion of Ilium, ➔ articulate with the tibia ischium and pubis. ➔ separated by the intercondylar fossa. ○ Accommodates the head of the femur. ○ Patella - knee cap ➔ Triangular bone located within a tendon that passes False Pelvis over the knee. ➔ superior to the true pelvis ➔ Protects the anterior articular surface of the knee ➔ the area medial to the flaring portions of the ilia. joint. True Pelvis ➔ Patellar surface - anteriorly on the distal femur; ➔ surrounded by bone forms a joint with the patella. ➔ lies inferior to the flaring parts of the ilia and the pelvic brim. Outlet ➔ the inferior opening of the pelvis measured between the ischial spines. Inlet ➔ superior opening between the right and left sides of the pelvic brim. Gender Differences of the Pelvis The Leg The leg has two bones Tibia - shin bone; larger ○ Tibial Tuberosity ➔ a roughened area on the anterior tibial surface. Female inlet is larger and more circular ○ Medial Malleolus Female pelvis is shallower ➔ forms the inner bulge of the ankle. Bone are lighter and thinner ○ Anterior Border Female ilia flare more laterally ➔ unprotected by muscles which makes it easily felt Female sacrum is shorter and less curved beneath the skin. Female ischial spine are shorter and farther apart (bigger Fibula - long and thin outlet) ○ Lateral Malleolus Female pubic arch is more rounded. ➔ on the distal end BSN1-A | 4  ➔ forms the outer part of the ankle. Cartilaginous Joints (AMPHIARTHROSIS) The Foot Bones connected by cartilage The foot Examples: ○ Tarsal (7) - ankle ○ Pubic Symphysis Body weight is carried mostly by the Calcaneus and ○ Intervertebral Joints Talus. Calcaneus - heel bone; largest tarsal Talus - second largest tarsal; lies superior to the calcaneus. ○ Metatarsals (5) - sole/instep ○ Phalanges (14) - toes G. JOINTS Articulations of bones Functions of joints include: ○ Holds bones together ○ Provide flexibility Ways joints are classified: ○ By their function ○ By their structure Synovial Joints H. FUNCTIONAL CLASSIFICATION OF JOINTS Articulating bones are separated by a joint cavity Synarthroses - immovable joints Synovial fluid is found in the joint cavity Amphiarthroses - slightly moveable joints Reinforced by ligaments Diarthroses - freely moveable joints All joints in the limbs are synovial joints. Fibrous joints - generally immovable Bursae - small fluid-filled sacs that reduce friction Cartilaginous Joints - Immovable or slightly moveable between moving parts in your body's joints. Synovial Joints - Freely moveable Synovial Joints have 4 distinct features: ○ Articular Cartilage - covers the ends of the bones forming the joints. ○ Articular Capsule - The joint surfaces are enclosed by a sleeve of fibrous connective tissue lined with a smooth synovial membrane. ○ Joint Cavity - The articular capsule encloses a cavity called the joint cavity which contains a lubricating synovial fluid. ○ Reinforcing Ligaments - The fibrous layer of the capsule is usually reinforced with ligaments 6 types of Synovial Joints Fibrous Joints (SYNARTHROSIS) Hinge Joint Bones united by fibrous tissue - largely immovable. ○ Movement is like two boards joined together by a Examples include sutures of the skull. hinge. ○ Movement in one direction; Elbow, knees, fingers. Ball and Socket Joint ○ When ball-shaped end of one bone fits into the cup-shaped socket of another ○ Bones can move in many directions Shoulder, hip Pivot Joint ○ Allows for rotation around the length of a bone. BSN1-A | 5  ○ Allows only for rotation Unlike nerves, however, muscles are also: Head (side to side “no” action ○ Contractible (they can shorten in length) Forearm joints (palms) supination/pronation ○ Extensible (they can extend or stretch) ○ Elastic (they can return to their original shape) Saddle Joint ○ When the surfaces of both articulation bones are B. Three Types of Muscular Tissue saddle-shaped Skeletal Muscle ○ Concave/Convex ➔ Fibers are HUGE, cigar shaped, multinucleate ○ Thumbs ○ Wide range of motion Smooth Muscle ➔ Spindle-shaped Gliding Joint ➔ Surrounded by scant endomysium ○ Interaction of flat surfaces of articulating bones ➔ Contraction is SLOW and SUSTAINED. ○ Limited but complex movement Wrist, ankle Cardiac Muscle ➔ Cushioned by small amount of soft connective tissues Condyloid Joint (endomysium) ○ Oval-shaped articular surface of one bone fits into the ➔ Arranged in SPIRAL or figure 8-shaped bundles oval-shaped depression of another ➔ Contact at a fairly steady rate (Pacemaker) Mandible, knuckles I. INFLAMMATORY CONDITIONS ASSOCIATED Location Function Appearance Control WITH JOINTS Bursitis SKELETAL Skeleton Movement, Striated, V ○ inflammation caused by a bursa usually caused by a blow heat, multi-nucleat or friction. posture ed Tendonitis (eccentric), ○ inflammation of tendon sheaths. fibers Arthritis parallel ○ Inflammatory or degenerative diseases of joints. ➔ Over 100 different types CARDIAC Heart Pump Striated, one I ➔ The most widespread crippling disease in the United blood central States continously nucleus Clinical Forms of Arthritis VISCERAL G.I. tract, Peristalsis, No I Osteoarthritis uterus, blood striations, ○ Most common chronic arthritis eye, pressure, one central ○ Probably related to normal aging processes blood pupil size, nucleus Rheumatoid arthritis vessels erects hairs ○ An autoimmune disease – the immune system attacks the joints ○ Symptoms begin with bilateral inflammation of certain joints C. Skeletal Muscle Fibers ○ Often leads to deformities Skeletal muscle is the only organ of the muscular system Gouty Arthritis ➔ Largest - 30 cm (1 foot in length) ○ ➔ Forms contour of body Skeletal muscle is composed of skeletal muscle tissue and II. THE MUSCULAR SYSTEM also contains nervous tissue, blood vessels and connective tissue MUSCLE Half of the body’s weight is muscle tissue Latin word “mus” - “Little mouse” ○ Skeletal muscle = 40% in males, 32% in females ○ Cardiac muscle = 10% A. Functions of the Muscular System Allow for movement, facial expressions, breathing, 1. Producing Movement - contraction of skeletal muscle swallowing, writing, talking and singing, posture, heat ➔ Respond to change in external; environment production ➔ Express emotion (smile and frown) 2. Maintaining Posture and Body Position Connective Tissue Coverings ➔ Muscle adjust after the other - maintain posture Fascia 3. Stabilizing Joints ➔ surrounds an individual skeletal muscle, separating it ➔ Skeletal muscle pulls on bone from other muscles. ➔ Muscle tendon reinforces and stabilizes joints ➔ Tendon - fascia extending beyond the ends of the 4. Generate heat muscle. ➔ Body heat - product of muscle activity (ATP) ➔ Aponeurosis - Fascia connecting to a muscle. ➔ Heat maintain normal body temperature Like nervous tissue, muscles are excitable or “irritable” ○ they have the ability to respond to a stimulus. BSN1-A | 6  D. Organization of Muscle Tissue F. Structure and Organizational Levels of Skeletal Muscle MUSCLE (organ) ENDOMYSIUM Connective tissue sheath that encloses a muscle fiber (cell). PERIMYSIUM Coarse fibrous membrane that wrap several sheath muscle fibers. A muscle consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels, FASCICLE and nerve fibers. bundle of fibers Covered externally by the epimysium. EPIMYSIUM Fascicle (a portion of the muscle) (Epi –upon,over, beside ; mys-muscle) Tough “overcoat” of connective tissue that binds fascicle APONEUROSIS Epimysia blends into a strong, cord-like tendon which attach muscle indirectly to bones, cartilages or connective tissue coverings. A Fascicle is a discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath. TENDONS Surrounded by the perimysium. Tough collagenic fibers - anchors to bone Muscle Fiber (cell) E. Skeletal Muscle Arrangement A single muscle cell is a muscle fiber ○ Fibers are made up of myofibrils. ○ Myofibrils are made up of thick and thin filaments. Sarcolemma - muscle cell membrane Sarcoplasm - muscle cell cytoplasm Myofibrils are striated ○ Striations due to arrangement of thick and thin filaments A muscle fiber is an elongated multinucleate cell; it has a Seen as alternating areas of light and dark bands banded (striated) appearance. Sarcomere - The length of each myofibril that is divided Surrounded by endomysium. into repeating units. ○ A sarcomere is the functional unit of skeletal muscle BSN1-A | 7 Myofibril or Fibril (complex organelles composed of MYOSIN bundles of myofilaments). ➔ protein molecule ➔ ATPase enzymes - general power of contraction H. Sarcomere Structure Sacromere exists from Z-line to Z-line A-band is dark middle band ○ Overlapping think and thin filaments Myofibrils are rodlike contractile elements that occupy I-Band - ends of A-Band, thin filaments only most of the muscle cell volume. Z-line is in the middle if the I-Band Composed of sarcomeres arranged end to end, they Myosin filaments are held to the z-line by titin proteins appear banded, and bands of adjacent myofibrils are aligned. I. Thick Filament Structure Sarcomere (a segment of a myofibril) A sarcomere is the contractile unit, composed of myofilaments made up of contractile proteins. Myofilament or Filament (extended macromolecular structure) Composed of many myosin molecules ○ Each myosin molecule has a tail region and 2 globular heads (crossbridges) Contractile myofilaments are two types-thick and thin. ➔ When they link is causes the CONTRACTION Thick filaments contain bundled myosin molecules; thin J. Thin Filament Structure filaments contain actin molecules (plus other proteins). The sliding of the thin filaments past the thick filaments produces muscle shortening. Elastic filaments maintain the organization of the A band and provide elastic recoil when muscle contraction ends. G. Sarcomere Arrangement Composed of actin protein ○ 2 strands of globular actin molecules twisted into a helix ○ Actin filaments have binding sites for myosin cross bridges ○ Tropomyosin protein spirals around actin helix Troponin protein (3 subunits) is attached to actin and holds tropomyosin in place ○ Call this the troponin-tropomyosin complex Alternating light (I) and dark (A) bands give the muscle cell as a whole its STRIPED appearance. The banding pattern reveals the working structure of the myofibrils. Thick filaments - myosin filaments Thin Filaments - contractile protein “actin” BSN1-A | 8  K. Physiology of Skeletal Muscle SKELETAL MUSCLE CONTRACTION Contraction: Neurotransmitter Release When a nerve impulse reaches a neuromuscular junction, acetylcholine (ACH) is released. Upon binding to sarcolemma receptors, ACh causes a change in sarcolemma permeability leading to a change in membrane potential. STEPS: 1. Action potential arrives at axon terminal of motor neuron 2. Voltage-gated Ca2+ channels open. Ca2+ enters the axon terminal moving down its electrochemical gradient, 3. Ca2+ entry causes ACh to neurotransmitters to be released by exocytosis. 4. ACh diffuses across the synaptic cleft and binds to its receptors on the sarcolemma. 5. ACh binding opens ion channels in the receptors that allow simultaneous passage of Na+ into the muscle fiber and K+ out of the muscle fiber. More Na+ ions enter than L+ ions exit, which produces a local Motor impulse is initiated in the brain change in the end plate potential. Travels through the brain and spinal cord to a motor nerve 6. ACh effects are terminated by its breakdown in the ending synaptic cleft by acetylcholinersterase and diffusion Motor nerve endings (axons) depolarize away from the junction. Calcium enters the axonal endings Calcium causes the release of acetylcholine into the L. Sliding Filament Theory neuromuscular junction (synaptic cleft) A sarcomere is the functional unit of skeletal muscle When a skeletal muscle contracts, sarcomeres shorten MOTOR NEURON The sliding filament model of contraction states that during Nerve cell that innervates skeletal muscle tissue contraction the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater DENDRITE degree ➔ Receives information AXON ➔ Transmits information ➔ Has vesicles containing neurotransmitters that will stimulate or inhibit muscle contraction. NEUROMUSCULAR JUNCTION ➔ site where branch of motor neuron (motor nerve ending) comes in contact with sarcolemma of skeletal muscle fiber. NEUROMUSCULAR JUNCTION Motor end-plate ➔ Sarcolemma of muscle fiber directly beneath motor THE SLIDING-FILAMENT MECHANISM nerve ending ➔ Contains an abundance of mitochondria and nuclei) Acetylcholine (Ach) is the neurotransmitter released by motor neurons ➔ Chemical substance released from vesicles in the motor nerve ending (axonal ending When stimulated by a nerve impulse, Acetylcholine is released, travels across the synaptic cleft and binds receptors on the motor end plate Stimulates contraction The “sliding” of actin on myosin (thick filaments on thin filaments) can be broken down into a 4 step process BSN1-A | 9  MUSCLE RELAXATION MECHANISM Acetylcholinesterase present in the NMJ destroys ACh (preventing continual stimulation) Calcium ions are transported from the sarcoplasm back into the SR. Linkages between myosin and actin are broken Requires ATP binding THEN: The muscle fiber relaxes With exposure of the myosin binding sites on actin (the thin ENERGY FOR CONTRACTION filaments)—in the presence of Ca2+ and ATP—the thick and Muscle cells require huge amounts of ATP energy to thin filaments “slide” on one another and the sarcomere is power contraction shortened The cells have only a very small store of ATP. Three pathways supply ATP to power muscle contraction M. Physiology of Skeletal Muscle Contraction:Power Stroke Calcium binds troponin (which is attached to tropomyosin Moves tropomyosin from the myosin binding sites on actin Myosin crossbridges (heads) bind to actin ○ ATP hydrolysis supplies energy Actin is pulled inward towards the center of the sarcomere = POWER STROKE Sarcomeres shorten as muscle contracts ENERGY FOR CONTRACTION ATP initially supplied from cellular respiration. If ATP is abundant, it is converted to creatine phosphate and stored in skeletal muscles. When ATP is low, creatine phosphate supplies phosphate to ADP making ATP. CP & ATP stores only good for about a 10 second maximal contraction. ATP must then come from cellular respiration or glycolysis. N. Physiology of Skeletal Muscle Contraction: Depolorization After ACh binds to the ACh receptors, its effects are quickly terminated by acetylcholinesterase , an enzyme located in the synaptic cleft. Acetylcholinesterase breaks down ACh to its building blocks, acetic acid and choline This removal of ACh prevents continued (and most likely undesirable) muscle fiber contraction in the absence of additional nervous system stimulation BSN1-A | 10  Exercise and Skeletal Muscles Intense, strenuous exercise Muscles exceed capacity of respiratory and cardiovascular systems to deliver oxygen for contraction. ATP supplied anaerobically through glycolysis Pyruvate is converted to lactic acid Lactic acid builds up in muscles Causes muscles to fatigue OXYGEN DEBT Oxygen & Muscle Contraction Myoglobin of muscle (similar to hemoglobin) binds to and stores oxygen Supplies O2 needed to make ATP for contraction Exercise and Skeletal Muscles Prolonged, moderate exercise ATP supplied through cellular respiration Amount of oxygen needed by liver cells to use the Once glycogen stores are depleted in muscle, glucose and accumulated lactic acid to produce glucose fatty acid deliveries from blood are used as fuel source ○ Oxygen not available ○ Glycolysis continues Exercise and Contraction ○ Pyruvic acid converted to lactic acid In intense strenuous activity, oxygen can be depleted. ○ Liver converts lactic acid to glucose Why? Also the amount of oxygen needed to replace O2 levels in ○ Contraction of skeletal muscles decreases blood skeletal muscle to pre-exercise levels. delivery to muscles Nutrient and O2 levels in contracting muscles decrease HEAT PRODUCTION Cellular respiration is only about 40% efficient. About 60% of the energy found in a glucose is lost as heat during cellular respiration. Muscle contraction generates heat because muscles use large amounts of nutrients to make ATP, generating large amounts of heat. Heat is used to maintain body temperature. BSN1-A | 11  O. Lever Systems: Bone-Muscle Relationships The operation of most skeletal muscles involves leverage—using a lever to move some object. ○ LEVER ➔ a rigid bar that moves on a fixed point called the FULCRUM. Effort ○ The applied force; ○ is used to move a resistance or load. JOINTS – acts as Fulcrums BONES - acts as Levers Lever Systems: Second Class FULCRUM-LOAD-EFFORT Example: Wheelbarrow Each BONE is a LEVER ○ a rigid, moving structure Each JOINT a FULCRUM ○ a fixed point Muscles provide applied force (AF) required to overcome resistance (R) FUNCTIONS To change: In the body, a second class leverage is exerted when Direction of an AF. you stand on tip-toe. Distance & speed of movement produced by an AF. ○ Effort = exerted by calf muscles pulling upward on Effective strength of an AF. the heel. ○ Fulcrum - joints of the ball of the foot. THREE CLASSES OF LEVER SYSTEM ○ Load = weight of the body ➔ depend on the relationship between applied force, fulcrum, and resistance. first class, second class, third class Lever Systems: First Class LOAD-FULCRUM-EFFORT Example: Scissors Lever Systems: Third Class LOAD-EFFORT-FULCRUM Example: tweezers or forceps. In the body, a first class system raises your head off your chest. The posterior neck muscles = effort the atlanto-occipital joint = fulcrum the facial skeleton = weight to be lifted/load. In the body, flexing the forearm by the biceps brachii muscles exemplifies third-class leverage. ○ Effort = exerted on the proximal of the forearm ○ Fulcrum = elbow joint ○ Load = hand and the distal end of the forearm BSN1-A | 12  P. Muscle Attachments Point of Attachment ORIGIN ➔ Point of attachment does not move (immovable) ➔ Origin bone is the more stationary of the two bones at a joint when contraction occurs INSERTION ➔ Moves during contraction ➔ Insertion bone towards the origin bone *REMEMBER!* The terms origin and insertion provide useful points of reference. Many muscles have multiple points of origin and insertion. Understanding the functional relationship of these attachment points during muscle contraction INVERSION AND EVERSION helps in deducing muscle actions” Special movement of the foot ○ Inversion - turn the sole medially ○ Eversion - turn the sole laterally Q. Basic Body Movement DORSIFLEXION AND PLANTAR FLEXION UP and DOWN movement of the foot ○ Dorsiflexion – Lifting foot so that superior surface approaches the shin (walking on heels) Hands – extension of hands at the wrist ○ Plantar Flexion - depressing the foot (pointing the toes) Hands – flexion of the hands. SUPINATION Turning backward Forearm rotates laterally so that palm face anteriorly. PRONATION Turning forward FLEXION Forearm rotates medially so that palm face posteriorly. Decrease the angle of the joint and bring two bones together. SUPINATION “Hinge joint” - bending The saddle joint between the metacarpal 1 and the carpal allows opposition of the thumb. EXTENSION Movement to increase the angle or distance between two bones R. Interaction of Skeletal Muscle in the body ABDUCTION Muscle groups produce an opposite movement on the Moving a limb away (from midline) ;fingers and toes opposite side of the joint spread apart Produces smooth, smooth, and coordinated movement. ADDUCTION PRIME MOVERS: Moving of a limb toward the midline. ○ Responsible for the causing a particular movement ROTATION ANTAGONIST: ○ Muscle that oppose or reverse the movement Movement of a bone around its longitudinal axis Example: ○ STRETCHED AND RELAXED- When prime mover is ball and socket joint, movement of atlas around the dens active. CIRCUMDUCTION SYNERGIST: Combination of flexion, extension, abduction adduction ○ Help prime mover by producing the same movement Example: ball and socket joint (shoulder); Proximal end is or by reducing movement stationary and its distal end moving is circle. ○ Example: Finger flexor muscle of both wrist and the finger joint FIXATOR: ○ Specializes synergist BSN1-A | 13  ○ Stabilize the origin of a prime mover so all the tension 2. CONVERGENT can be used to move to move the insertion bone Fascicles converge toward a single insertion tendo ○ Example: Pectoralis major S. Names of Skeletal Muscle 3. PARALLEL DIRECTION OF THE MUSCLE FIBER Length of the fascicles run parallel to the long axis of the ➔ Reference to imaginary line (Midline or Long axis) muscle RECTUS – straight, muscle fiber runs parallel to the ○ Example: Sartorius muscle imaginary line ○ Example: rectus femoris (straight muscle of the thigh 4. PENNATE /femur) Short fascicle attached obliquely to the central TENDON. OBLIQUE – muscle runs obliquely (slant) ○ Example: Extensor digitorum (leg muscle) ○ Fascicle insert into only one side of the tendon and RELATIVE SIZE OF THE MUSCLE muscle MAXIMUS – Largest (Gluteus maximus) MINIMUS – Smallest 5. BIPENNATE LONGUS - Long Fascicle insert into OPPOSITE site or from several different sides. NUMBER OF ORIGIN BIceps – TWO origins 6. FUSIFORM ○ Example; Biceps muscle of arm has two heads Spindle-shaped muscle with an EXPANDED belly TRIceps – THREE Origin (midsection) QUADriceps – FOUR Origin ○ Example: Biceps brachii LOCATION OF THE MUSCLES ORIGIN AND INSERTION U. Muscles of the Face Example: STERNOCLEIDOMASTOID MUSCLE 1. Frontalis ○ Origin: STERNUM and CLAVICLE(Cleido) 2. Corrugator ○ Insertion: Mastoid process 3. Procerus 4. Depressor supercilli SHAPE OF THE MUSCLE 5. Orbicularis oculi (superior lateral) Deltoid - Triangular 6. Orbicularis oculi (lateral) ○ Example: Deltoid muscle 7. Nasalis 8. Levator labii superioris alaeque nasi ACTION OF THE MUSCLE 9. Levator labii superioris ACTION – Flexor, Extensor and Adductor. 10. Zygomaticus minor ○ Example: Adductor muscle of the thigh – 11. Zygomaticus major ADDUCTION 12. Orbicularis oris ○ Extensor muscle of the wrist - EXTENSOR 13. Buccinator 14. Risorius T. Arrangement of Fascicles 15. Masseter 16. Depressor anguli oris 17. Depressor labii inferioris 18. Platysma 19. Mentalis 1. CIRCULAR Arrange in concerntric rings Usually found surrounding external body opening which closes by contraction. ○ Example: Orbicularis muscle surrounding the eyes and mouth. BSN1-A | 14  Orbicularis oculi (Superficial muscle of expression) Thin, flat sphincter muscle of eyelid; surrounds the rim of the orbit. ORIGIN Frontal bone, maxilla medial palpebral ligament lacrimal bone INSERTION Lateral palpebral raphe V. Muscles of the Head superior and inferior tarsi medial Occipitofrontalis (Epicranius) ACTION Blinks and closes eyelids Bipartite muscle consisting of the frontal and occipital bellies connected by the epicranial aponeurosis. NERVE Facial Nerve Muscle of the Scalp SUPPLY Covers forehead and dome of the skull; no bony attachment. Orbicularis oris ANTERIOR SCALP: FRONTALIS (FRONTAL BELLY) Encircles the mouth, muscle of facial expression. Kissing and whistling muscle ORIGIN INSERTION ACTION NERVE SUPPLY ORIGIN Mandible and maxilla Epicranial Skin of Raises the Facial nerve aponeurosis eyebrow and eyebrow, INSERTION Sphincter-like muscle at the angle of the root of nose wrinkles mouth forehead horizontally ACTION superficial = closes, protrudes lips; deep = presses lip against teeth POSTERIOR (SCALP) BELLY: OCCIPITALIS NERVE Facial Nerve ➔ Overlies posterior occiput; by pulling on the epicranial SUPPLY aponeurosis, fixes origin of frontal belly. W. Muscle of Mastication ORIGIN INSERTION ACTION NERVE Temporalis SUPPLY Fan-shaped muscle that covers parts of the temporal, frontal, and parietal bones Occipital bone Galea Pulls scalp Facial nerve and temporal aponeuronica posteriorly bone ORIGIN Temporal fossa Temporal fascia INSERTION Coronoid process anterior ramus of mandible ACTION Closes Jaw Elevates and retracts the mandible against maxilla with great force NERVE Trigeminal Nerve SUPPLY BSN1-A | 15 Masseter Levator labii Superioris Powerful muscle that covers lateral aspect of the Thin muscle between orbicularis oris and inferior eye mandibular ramus. margin Superficial muscle of mastication ORIGIN Zygomatic bone and infraorbital margin of maxilla ORIGIN Temporal bone INSERTION Skin and muscle of upper lip INSERTION Ramus of mandible ACTION Opens lips; raises and furrows upper lip ACTION Raises the mandible against the maxilla with great force NERVE Facial Nerve SUPPLY NERVE Trigeminal nerve SUPPLY (Cranial Nerve V) Depressor labii inferioris Small muscle running from mandible to lower lip Buccinator ORIGIN Body of the mandible lateral to its midline Thin, horizontal cheek muscle; principal muscle of the cheek; deep to masseter INSERTION Skin and muscle of the lower lip ORIGIN molar region of maxilla and mandible ACTION raws lower lip inferiorly (pout) NERVE Facial Nerve INSERTION Orbicularis Oris SUPPLY ACTION Compresses cheek (as in whistling and Depressor anguii oris sucking,draws corner of mouth laterally Small muscle running from mandible to lower lip ORIGIN Body of mandible below incisors NERVE Facial Nerve INSERTION Skin and muscle at angle of mouth below SUPPLY insertion of zygomaticus Zygomaticus ACTION Draws corners of mouth down and laterally Muscle pair extending diagonally from cheekbone to (a”tragedy mask” grimace); zygomaticus corner of mouth antagonist) ORIGIN Zygomatic Bone NERVE Facial Nerve SUPPLY INSERTION Skin and muscle at the corner of the mouth ACTION Raises lateral corners of mouth upward X. Eye Muscles (smiling muscle) ‘ Superior rectus Upgaze, upward; with some contribution – inferior oblique NERVE Facial Nerve Rotate medially SUPPLY Lateral rectus Outward, toward the ear Risorius Slender muscle inferior and lateral to zygomaticus Superior oblique Rotate medially ORIGIN Lateral Fascia associated with masseter muscle Inferior rectus Down gaze, downward; with some contribution – superior INSERTION Skin at angle of mouth oblique Rotate laterally ACTION Draws corner of lip laterally; tenses lips; synergist of zygomaticus Medial rectus Inward, toward the nose NERVE Facial Nerve SUPPLY Inferior oblique Rotate laterally BSN1-A | 16  Y. Muscles of the Neck SPLENIUS CAPITIS Muscles that moves the head and shoulder girdle ➔ Intrinsic muscle of the spine PLATYSMA ➔ Classified with posterior triangle of the neck ➔ Vertebral column and head movements ➔ Unpaired, thin, sheetlike superficial neck muscle; not strictly a head muscle, but plays a role in facial expression ➔ A single sheet-like muscle that covers the anterolateral ORIGIN Lower half of ligamentum nuchae and neck spinous process of 7th cervical vertebra – 3rd or 4th thoracic vertebra ORIGIN fascia of chest (over pectoral muscles and INSERTION Mastoid process of temporal bone and deltoid) occipital bone ACTION ○ Supports head erection INSERTION Lower margin of mandible, and skin and ○ Draws head directly backwards muscle at corner of mouth ○ Draws head to one side ○ Slight rotation, turning face to same side ACTION Tenses skin of neck (as during shaving); helps depress mandible; pulls lower lip back NERVE Cervical spinal nerve and down, producing downward sag of SUPPLY mouth; “Sad Clown Face” NERVE Facial Nerve Z. Muscles of the Trunk SUPPLY ➔ Muscles that moves the: Vertebral column (Posterior anti-gravity muscle) Anterior Thorax (ribs, head and arms) STERNOCLEIDOMASTOID Abdominal wall – moves the vertebral column ➔ Neck muscle classified with lateral cervical muscles ANTERIOR MUSCLES ➔ Arises from two heads, responsible for movements of the vertebral column and head. Pectoralis Major Anterior shoulder joint muscles forming the shoulder girdle Fan-shaped ORIGIN Sternum and clavicle Three heads: ○ Clavicular ○ Sternocostal INSERTION Lateral surface of the mastoid process; ○ Abdominal nuchal line of occipital bone Pectoralis Major ACTION Draws head towards shoulder of same side, rotates head to opposite side, flexes cervical ORIGIN Sternum, clavicle and first to sixth ribs part, assist in elevating the thorax INSERTION Proximal humerus NERVE Accessory nerve (cranial nerve XI) and SUPPLY branches of cervical spinal nerves C2 and C3 ACTION Adducts and flexes the humerus (ventral rami) Intercostal Muscles SCALENES Located more laterally than anteriorly on neck; deep to External intercostals platysma and sternocleidomastoid. Muscles of thorax from tubercles of the ribs behind to the cartilages of the ribs in front. Fibers are directly obliquely downwards and laterally on ORIGIN Transverse processes of cervical vertebrae the back of the thorax, and downward, forward and medial ward to the front INSERTION anterolaterally on first two rib ORIGIN lower border of ribs 1-11 ACTION Elevate first two ribs (aid in inspiration); flex and rotate neck INSERTION Upper border of ribs below 2- 12 NERVE Cervical spinal nerve SUPPLY ACTION Elevates the ribs, aiding in normal inspiration (Inhalation) BSN1-A | 17 Internal intercostals Rectus abdominis Muscles of the thorax, from sternum to vertebral column. Most SUPERFICIAL muscle of the abdomen Fibers are directed obliquely and pass in a direction Long, flat, paired strap-like muscle of the abdomen opposite of the external intercostals Extends the length of front of abdomen (From the pubis to the rib cage enclosed in a aponeurosis) FLEX the vertebral column ORIGIN Superior border of 2nd – 12th rib Separated by the linea alba “abdominal muscle” or “abs” Compress the abdominal content during defecation and INSERTION inferior border of the ribs above 1-11 childbirth / Forceful breathing ACTION Depresses the ribs, aids in forced expiration ORIGIN Crest of the pubis and pubic tubercle; front of pubis symphysis Diaphragm Muscles of the thorax INSERTION Crest of the pubis and pubic tubercle; front of Dome-shaped, musculofibrous septum pubis symphysis Separate thoracic & abdominal cavities Principal muscle of inspiration ACTION Flexes vertebral column Tenses abdominal wall Compresses abdominal viscera ORIGIN Xiphoid process, cartilages of ribs 7-12, anterior surface of the lumbar vertebrae, Internal Oblique crura of the upper two (left crus) and three Paired muscle deep to the external obliques. (right crus) lumbar vertebrae Fibers run at right angle to those of the external oblique. Thinner and smaller than external oblique ARISES from the iliac crest and INSERT into the last three INSERTION Central tendon that blends with the anterior ribs. longitudinal ligament of the vertebral column ORIGIN Lateral half of the inguinal ligament, middle ACTION Expands the thoracic cavity Compresses the lip of the iliac crest; and lumbodorsal for abdominal cavity thoracolumbar fascia MUSCLES OF THE ABDOMINAL WALL INSERTION Pubis, inferior border of the lower 3 or 4 ribs External oblique (9, 10-12), linea alba; aponeurosis fus Rectus abdominis Internal oblique ACTION Bilaterally: compresses the abdominal Transverse abdominis viscera; flexes the spine Unilaterally: laterally flexes and rotates ★ Reinforces body trunk – contain and protect the spine to same side abdominal contents ★ Muscle fibers forms a pair that runs in different direction ★ Exceptionally strong for its THICKNESS Transverse Abdominis Arises from the lower ribs and iliac crest into the pubis External Oblique “transverse” direction of the fibers Situated at the lateral and anterior part of the abdomen Most internal of flat muscles Fibers run downward and medially from the last eight ribs Located deep to the internal oblique and insert in the ilium Fibers run horizontally across the abdomen Largest and most superficial of the three flat muscles Muscle compresses the abdominal content. FLEXES the vertebral column, ROTATES the trunk and bend it LATERALLY ORIGIN Lateral third of the inguinal ligament, inner lip of iliac crest, inner surface of the cartilages of ORIGIN Sternum, external surfaces and inferior the lower 6 ribs, lumbodorsal (thoracolumbar) border of lower eight ribs (5-12) fascia and interdigitating with diaphragm INSERTION Pubis, line alba via an aponeurosis and the INSERTION Ends in an aponeurosis; upper ¾ forms the iliac crest back of the rectus sheath and insert on the linea alba; the lower 4 th forms the front of ACTION Bilaterally: compresses the abdomen and the rectus sheath and attaches to the pubis flexes the spine Unilaterally: laterally flexes the trunk to ACTION Compresses abdominal visceral tenses same side; rotate trunk to opposite side abdominal wall BSN1-A | 18  POSTERIOR MUSCLES ORIGIN Iliac crest, lumbar fascia Trapezius Most superficial muscle of posterior thorax; flat and triangular in shape; upper fibers run inferiorly to scapula; INSERTION Transverse process of upper lumbar middle fibers run horizontally to scapula; lower fibers run vertebrae superiorly to scapula ACTION Flexes spine laterally; extend spine ORIGIN Occipital bone, and all cervical and thoracic vertebrae III. THE MUSCULAR SYSTEM (UPPER AND LOWER LIMB) INSERTION Lateral third of clavicle, acromion and scapular spine of scapula A. Prime Movers of the Arm Pectoralis major ACTION Raises, retracts and rotates scapula Latissimus Dorsi Deltoid Muscles of the Humerus NERVE Accessory nerve (cranial nerve XI); C3 and Biceps Brachii SUPPLY C4 Brachialis Brachioradialis Triceps Brachii Latissimus Dorsi Two large flat muscle that covers the lower back Deltoid Two large flat muscle covering the lumbar region and “delta” – triangular lower half of the thoracic region Thick, multipennate muscle forming rounded shoulder Function include joining the upper limb with the axial muscle mass skeleton and facilitate motion of upper limb (example: Common site for intramuscular injection swimming striking a blow) ORIGIN Lower spine and iliac crest ORIGIN Lateral third of the clavicle; acromion; scapular spine INSERTION Proximal humerus INSERTION Deltoid tuberosity of the lateral side of the ACTION Extend and adducts the humerus body of the humerus Erectore Spinae ACTION Prime mover of arm abduction when all its Group of prime movers of back fibers contract simultaneously Paired muscle – deep muscle Composite muscle Antagonist of pectoralis major and latissimus ○ Longissimus dorsi which adduct the arm. ○ Iliocostalis ○ Spinalis Synergist of pectoralis major Power back extensor (“erectors”) – provides resistance of bending over the waist. ✔Anterior fibers are active - act powerfully in Common cause of lower back pain flexing and rotating humerus medially. ORIGIN Lower spine and iliac crest Ribs 2-3 and ✔ Posterior fibers are active - extension and vertebrae lateral rotation of arm Flexion and medial rotation of humerus INSERTION Ribs, thoracic and cervical vertebrae Abduction of the humerus ACTION Raises, retracts and rotates scapula Extension and lateral rotation of the humerus NERVE Extend and laterally flexes spine SUPPLY Nerve Axillary nerve (C5 and C6) Supply Quadratus Lumborum Forms part of the posterior abdominal wall Biceps Brachii Separately, each muscle FLEXES the spine LATERALLY. Two-headed fusiform muscle Collectively, EXTEND the lumbar spine. Bellies unite at insertion point is approached Arises from the iliac crest and insert into the upper lumbar Tendon of long head helps stabilize shoulder join vertebrae. Anterior flexor muscles of the elbow joint (powerful prime mover for flexion of forearm) BSN1-A | 19  Bulges when the elbow flexes Long head and short head Triceps Brachii The only muscle fleshing out of the posterior humerus Large upper limb muscle, posterior muscle of the elbow ORIGIN Short head: coracoid process joint Situated at the back of the arm, extends the entire length Long head: supraglenoid tubercle and lip of of the dorsal surface of humerus glenoid cavity. Powerful prime mover of elbow EXTENSION (ANTAGONIST of Biceps Brachii) Three head: INSERTION Deltoid tuberosity of the lateral side of the ○ Lateral head body of the humerus ○ Long head ○ Medical head Proximal radius “BOXERS” MUSCLE ACTION Flexion and medial rotation of humerus ORIGIN Long head: infraglenoid tubercle of scapula Abduction of the humerus Lateral head: posterior shaft of humerus Extension and lateral rotation of the humerus Medial head: posterior humeral shaft distal to Nerve Musculocutaneous nerve (C5 and C6 radial groove Supply INSERTION Olecranon process of the ulna Brachialis Strong muscle that is immediately deep to biceps brachii ACTION Powerful forearm extensor (prime mover, on distal humerus particularly medial head) Flexor muscle of the elbow Covers front of the elbow joint and lower half of the Antagonist of forearm flexors; long and humerus lateral heads mainly active in extending the forearm against resistance ORIGIN Front of distal humerus; embraces insertion of deltoid muscle Long head tendon may help stabilize shoulder joint and assist in arm adduction INSERTION Coronoid process of ulna and capsule of elbow joint. B. Muscles that Moves the Forearm ACTION A major forearm flexor (lifts ulna as biceps Pronator teres lifts the radius) pronation = turning palm posteriorly, or down teres = round Two-headed muscle; seen in superficial view between Nerve Musculocutaneous nerve proximal margins of brachioradialis and flexor carpi Supply radialis Forms medial boundary of cubital fossa. Brachioradialis Superficial muscle of lateral forearm; forms lateral Pronator teres boundary of cubital fossa; extends from distal humerus to distal forearm ORIGIN medial epicondyle of humerus; coronoid process of ulna ORIGIN Lateral supracondylar ridge at distal end of humerus INSERTION Common tendon into lateral radius, midshaft INSERTION Base of radial styloid process ACTION Pronates forearm; weak flexor of elbow ACTION Synergist in flexing forearm Acts to best advantage when forearm is partially flexed and semi pronated Stabilizes elbow during rapid flexion and extension BSN1-A | 20 Flexor carpi radialis flex = decrease angle between two bones carpi = wrist Flexor Digitorum Superficialis radi = radius digit = finger, toe superficial = close to surface) Runs diagonally across forearm; midway, its fleshy belly is Two-headed muscle; more deeply placed (therefore, replaced by a flat tendon that becomes cordlike at wrist actually forms an intermediate layer) Overlain by muscles above but visible at distal end of forearm Flexor carpi radialis ORIGIN medial epicondyle of humerus Flexor Digitorum Superficialis ORIGIN medial epicondyle of humerus, coronoid INSERTION Base of second and third metacarpals; process of ulna; shaft of radius insertion tendon easily seen and provides guide to position of radial artery at wrist (pulse taking) INSERTION four tendons into middle phalanges of fingers 2–5 ACTION Powerful flexor of wrist; abducts hand; weak synergist of elbow flexion ACTION Flexes wrist and middle phalanges of fingers 2–5 Nerve Median Nerve Supply Nerve Median nerve (C7, C8, and T1) Supply Palmaris longus Palma = palm Longus = long Small fleshy muscle with a long insertion tendon; often Flexor pollicis longus absent; may be used as guide to find median nerve that “flek·sr paa·luh·sis laang·guhs” lies lateral to it at wrist pollix = thumb Partly covered by flexor digitorum superficialis; parallels flexor digitorum profundus laterally Palmaris longus ORIGIN medial epicondyle of humerus Flexor pollicis longus ORIGIN anterior surface of radius and interosseous INSERTION palmar aponeurosis; (fascia of palm) membrane ACTION Tenses skin and fascia of palm during hand movements; weak wrist flexor; weak INSERTION distal phalanx of thumb synergist for elbow flexion ACTION Flexes distal phalanx of thumb Nerve Median Nerve Supply Flexor digitorum profundus Flexor carpi ulnaris profound = deep Most medial muscle of this group Extensive origin; overlain entirely by flexor digitorum Two-headed superficialis Ulnar nerve lies lateral to its tendon Flexor digitorum profundus Flexor carpi ulnaris ORIGIN coronoid process, anteromedial surface of ORIGIN Medial epicondyle of humerus; olecranon ulna, and interosseous membrane and posterior surface of ulna. INSERTION four tendons into distal phalange INSERTION Pisiform and hamate bones and base of fifth metacarpal ACTION Flexes distal interphalangeal joints; slow acting flexor of any or all fingers; helps flex ACTION Flexes wrist and abducts hands wrist Nerve Ulnar nerve (C7 and C8) Supply BSN1-A | 21 Pronator quadratus Extensor carpi digitorum quad = square, four-sided Lies medial to extensor carpi radialis brevis Deepest muscle of distal forearm; passes downward and Detached portion of this muscle, called extensor digiti laterally minimi, extends little finger Only muscle that arises solely from ulna and inserts solely into radius Extensor carpi digitorum Pronator quadratus ORIGIN Distal humerus ORIGIN distal portion of anterior ulnar shaft INSERTION Distal phalanges of second to fifth fingers INSERTION distal surface of anterior radius ACTION Extend fingers ACTION Prime mover of forearm pronation; acts with pronator teres; also helps hold ulna and Extensor carpi ulnaris radius together Most medial of superficial posterior muscles; long, slender muscle Extensor carpi radialis longus Extensor carpi ulnaris extend = increase angle between two bones Parallels brachioradialis on lateral forearm. ORIGIN Lateral epicondyle of humerus and posterior border of ulna Extensor carpi radialis longus INSERTION Base of fifth metacarpal ORIGIN Lateral supracondylar ridge of humerus ACTION Extends wrist in conjunction with extensor carpi radialis and adducts wrist in conjunction INSERTION Base of second metacarpal with flexor carpi ulnaris ACTION Extends wrist in conjunction with extensor carpi ulnaris and abducts wrist in conjunction Rhomboids with flexor carpi radialis Rhomboids Extensor carpi radialis brevis brevis = short ORIGIN Spinous processes of C7 and T1 (minor) and Shorter than extensor carpi radialis longus and lies deep spinous processes of T2–T5 (major) to it INSERTION Medial border of scapula Extensor carpi radialis brevis ACTION Stabilize scapula; act together (and with ORIGIN lateral epicondyle of humerus middle trapezius fibers) to retract (adduct) scapula INSERTION base of third metacarpal Assist trapezius in downward rotation of scapula ACTION Extends and abducts wrist; acts synergistically with extensor carpi radialis Adduction of scapula longus to steady wrist during finger flexion