MUSCLE ANATOMY & MOVEMENT Flashcards
Muscle Tissue Characteristics (3):
- Contraction –> Exhibits excitability to generate action potential and contract
- Relaxation –> Returns muscle to original length due to elasticity
- Extensibility –> Stretching and extending
Skeletal muscle
Organ consisting of various tissues; skeletal muscle fibers, blood vessels, nerve fibers, connective tissue and located throughout the body
Skeletal muscle functions (4)
- Causes body parts to move when contracted
- Controls movement of substances (swallowing)
- Protect internal organs
- Generate heat when contracted and maintain homeostasis
Skeletal muscle structure
Enclosed by 3 layers of connective tissue that compartmentalize muscle fibers
3 layers of skeletal muscle:
- Epimysium (outer)
- Perimysium (middle)
- Endomysium (inner)
Epimysium
Outer sheath of dense, irregular connective tissue surrounding entire muscle to allow it to contract and move powerfully; also separates muscle from other tissues/organs, allowing muscle to move independently
Perimysium
Middle layer surrounding bundles of muscle fibers (fascicle)
Endomysium
Innermost layer of thin connective tissue layer of collagen and reticular fibers surrounding individual muscle fibers containing extracellular fluid and nutrients for muscle fiber and supplied via blood
Relationship of tendons and the skeletal muscles
The collagen in the 3 layers intertwines with collagen of tendon, and the end of the tendon fuses with periosteum
Reason for the multinucleated skeletal muscle fiber
Embryonic myoblasts (each with ow nucleus) fuse with hundreds of other myoblasts
Multiple nuclei meaning
Means multiple copies of genes, permitting production of large amounts of protein and enzymes needed for muscle contraction
Sarcolemma
Cell membrane of muscle fiber
Sarcoplasm
Cytoplasm of muscle fibers
Sarcoplasmis reticulum (SR)
Specialized smooth ER that stores, releases, and retrieves calcium ions
Sarcomere
Functional unit of SKELETAL MUSCLE (arrangement of actin [thin], myosin [thick], other support proteins) with cylinder shape bordered by Z discs where actin is anchored
Myofibril
Repeating units of sacromeres that causes entire muscle cell to contract as each myofibril contracts
Reason for striated appearance of skeletal muscle fibers
Due to arrangement of actin and myosin
Troponin and tropomyosin
Regulatory proteins for each packet of actin and myosin
4 factors influencing movement at synovial joints (4):
- Orientation of muscle (origin and insertion)
- Action of other muscles (other muscles that may originate/insert on same bone)
- Type of joint that occurs between bone
- Muscle tension that can restrict full range of movement
Flexion and extension
Movement in sagittal plane and involve anterior and posterior movements of body/limbs
Flexion
Bending of neck or body and decreases the angle between bones
Extension
Straightening from flexed position and increases angle between bones and straightens joint
Lateral flexion
Movement towards right or left sides (eg. Bending head/body left or right)
Lateral flexion
Movement towards right or left sides (eg. Bending head/body left or right)
Hyperextension
Abnormal/excessive extension of joint beyond normal range of motion = injury
Hyperflexion
Excessive flexion at joint, common at hinge joints such as knee or elbow
Hyperflexion
Excessive flexion at joint, common at hinge joints such as knee or elbow
Abduction and adduction
Movement in coronal plane and involve medial or lateral movements of limbs, fingers, toes, or thumbs
Abduction
Moves limb laterally from midline of body (eg. Raising arm at shoulder)
Adduction
Moves limb medially towards midline of body (eg. Bringing arm down to side of body)
Circumduction
Movement of body region in circular manner so one region is relatively stationary, while the other describes a circle. Involves combination of flexion, extension, abduction, adduction at joint
Rotation
Twisting movement of body part around vertical axis and occurs at pivot or ball and socket joint (eg. Shaking head no, moving humerus/femur toward or away from midline)
Supination and pronation
Movements of forearm
Supinated position
Anatomical position with palm facing forward
Pronated position
Anatomical position with palms facing backwards
Supination
Moves forearm from palms facing backwards to forward
Pronation
Moves forearm from palms facing forward to backwards
Dorsiflexion and plantar flexion
Movements at ankle joint
Dorsiflexion
Lifting front of foot
Plantar flexion
Lifting heel of foot from ground and pointing toes downwards
Inversion and eversion
Complex movements involving multiple plane joints among tarsal bones of posterior foot
Inversion
Turning of foot toward midline
Eversion
Turning of foot away from midline
Protraction and retraction
Anterior-posterior movements of scapula (shoulder blades) and mandible (lower jaw)
Protraction
Pushing shoulder or lower jaw forwards
Retraction
Pulling shoulder or lower jaw backwards
Depression and elevation
Downward and upward movements of scapula or mandible
Depression
Occurs when shoulder or lower jaw moves downward
Elevation
Occurs when shoulder or upper jaw moves upwards
Sternocleidomastoid
Paired muscle that performs lateral flexion of the head, rotation of head, and flexion of head
Erector spinae group
Forms most of the muscle mass of the back and performs extension of the vertebral column
Abdominal muscles
4 pairs of muscles that cover the anterior and lateral abdominal region and meet at anterior midline. Muscles run in different orientations to allow various movements and rotations of trunk and to help protect internal organs
4 pairs of abdominal muscles:
- External obliques
- Internal obliques
- Transverse abdominis
- Rectus abdominis
Linea alba
White fibrous band that encloses the rectus abdominis muscles that perform flexion of abdomen
Diaphragm
Separates thoracic and abdominal cavities and is dome shaped at rest. Responsible for change in volume of thoracic cavity during breathing due to alternate contraction and relaxation and also functions with abdominal muscles for defecating, urination, and childbirth
3 openings for passage of structures between thorax and abdomen:
- Inferior vena cava passing through caval opening
- Esophagus passing through esophageal hiatus
- Aorta passing through aortic hiatus
Intercostal muscles
Three sets of muscles that span each of the intercostal spaces for breathing by allowing changes in dimension of rib cage
3 sets of intercostal muscle:
- External intercostal
- Internal intercostal
- Innermost intercostal
Trapezius
Important muscle affecting movements of pectoral (shoulder) girdle. Involved in diverse movements such as elevation, depression, and adduction of scapula and extension of head
Muscles that move the humerus (6):
- Pectoralis major; ADDUCTS humerus
- Latissimus dorsi; ADDUCTS humerus
- Coracobranchialis; flexes and ADDUCTS arm
- Deltoid; ABDUCTS humerus
- Supraspinatus; ABDUCTS arm
- Teres major and teres minor; extend arm
Muscles that move the forearm (radius and ulna)
Flexion of forearm by biceps branchii, branchioradialis, and branchialis. Extension of forearm by triceps branchii
Muscles that move the femur (3)
- Psoas major and iliacus that make up iliopsoas group; flexion of hip
- Gluteus maximus; lateral rotation and extension of hip
- Gluteus medius; adduction and medial rotation of hip
Muscles that move the femur, tibia, fibula (4)
- Gracilis; adduction of thigh and flexion of legs at knee
- Quadricepts femoris group; 4 muscles extension of lower leg at knee
- Sartorius; flexion of leg at knee and flexion, abduction and lateral rotation of leg at knee
- Hamstring group; flexion of leg at knee
Muscles that move feet and toes (4)
- Gastrocnemius; most superficial and visible of calf
- Soleus; deep to gastrocnemius and is wide and flat
- Both gastrocnemius and soleus contribute to plantar flexion
- Tibialis anterior; long thick muscle on lateral surface of tibia that raises front of foot when contracted (dorsiflexion)
Factors influencing muscle performance
Physical training and lack of use can result in marked increase and decrease in muscle performance
Hypertrophy
When muscles grow from use and structural proteins are added to muscle fibers (increase diameter)
Atrophy
When muscle fibers lose structural proteins due to the muscles not being used regularly (decrease muscle mass)
Sacropenia
Age related muscle atrophy
