Muscle Anatomy and Physiology Quiz

Bone Function

• Supports and protects vital organs
• Provides framework for movement
• Stores mineral reserves
• Produces blood cells (hematopoiesis)

Cartilage Structure & Types

• Hyaline cartilage: Smooth, glassy appearance found in ribs, nose, trachea, and articular surfaces of joints
• Elastic cartilage: More flexible and found in the ear and epiglottis
• Fibrocartilage: Strongest type, found in intervertebral discs and menisci of knee

Bone Types

• Compact bone: Dense, hard outer layer, provides strength and protection
• Spongy bone: Lighter, porous inner layer, provides flexibility and contains red bone marrow for blood cell production

Bone Classification

• Long bones: Longer than they are wide. Examples: femur, humerus
• Short bones: Cube-shaped, primarily for strength and stability. Examples: carpals, tarsals
• Flat bones: Thin, flat, curved for protection or broad muscle attachment. Examples: skull bones, ribs, scapula
• Irregular bones: Complex shapes that do not fit other categories. Examples: vertebrae, facial bones

Structure of a Long Bone

• Diaphysis: Long shaft of the bone
• Epiphyses: Expanded ends of the bone
• Epiphyseal plate: Growth plate made of hyaline cartilage, present during bone growth
• Periosteum: Tough outer covering of bone, contains blood vessels and nerves
• Endosteum: Lining of the medullary cavity, contains bone cells
• Medullary cavity: Hollow space within diaphysis, filled with yellow bone marrow (fat storage)

Microscopic Structure of Bone

• Osteon: Functional unit of compact bone, consists of concentric rings of bone matrix called lamellae
• Central canal: Runs through the center of the osteon, contains blood vessels and nerves
• Lacunae: Small spaces within lamellae that house osteocytes (mature bone cells)
• Canaliculi: Tiny canals that connect lacunae, allowing for nutrient and waste exchange

Bone Cells

• Osteoblasts: Immature bone cells that secrete bone matrix
• Osteocytes: Mature bone cells that maintain bone matrix
• Osteoclasts: Large, multinucleated cells responsible for bone resorption (breakdown)

Bone Development

• Intramembranous ossification: Bone formation directly from mesenchyme, how flat bones develop
• Endochondral ossification: Bone formation from a hyaline cartilage model, how long bones develop

Bone Growth

• Interstitial growth: Growth in length by cartilage cells in the epiphyseal plate
• Appositional growth: Growth in width by adding bone matrix to the surface

Bone Remodeling

• Continuous process of bone breakdown and formation
• Regulated by hormonal factors and mechanical stress

Bone Resorption

• Performed by osteoclasts
• Releases calcium and phosphate into the bloodstream

Bone Diseases

• Osteoporosis: Decreased bone density and increased fracture risk, often associated with aging, hormonal imbalances, or vitamin deficiency
• Osteomalacia: Softening of bones due to inadequate mineralization
• Osteopenia: Reduced bone density, not as severe as osteoporosis

Types of Bone Fractures

• Simple (closed): Bone does not break the skin
• Compound (open): Bone protrudes through the skin

Bone Markings

• Projections: Sites of muscle attachment or articulation
• Depressions: Hollows or indentations that allow passage of blood vessels or nerves

Axial Skeleton

• Skull: Protects the brain and provides attachment for facial muscles
  • Cranium (8 bones): Frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid
  • Facial bones (14 bones): Maxillae (2), palatine bones (2), zygomatic bones (2), nasal bones (2), lacrimal bones (2), inferior nasal conchae (2), vomer, mandible
  • Foramina: Openings in the skull for passage of nerves, blood vessels, and other structures
  • Foramen magnum: Large opening in the occipital bone, allows passage of the spinal cord
  • Skull sinuses: Air-filled cavities within the skull bones, lighten the skull and modify voice resonance
  • Sutures: Joints between the skull bones, allow for growth and flexibility
• Hyoid bone: Small, U-shaped bone in the neck, supports the tongue and aids in swallowing
• Vertebral column: Provides support and protection for the spinal cord, flexible and curved
  • Cervical vertebrae (7): Neck region, support the head, allow for flexion and extension
  • Thoracic vertebrae (12): Chest region, articulate with ribs, more rigid than cervical vertebrae
  • Lumbar vertebrae (5): Lower back region, bear the most weight of the body, large and robust
  • Sacrum (5 fused vertebrae): Forms the back portion of the pelvis, helps transfer weight to the lower limbs
  • Coccyx (4 fused vertebrae): Tailbone, provides attachment for some muscles
  • Abnormal curvatures: Scoliosis, lordosis, kyphosis
  • Primary curvatures: Develop in the fetus - thoracic and sacral curvatures
  • Secondary curvatures: Develop after birth - cervical and lumbar curvatures
  • Structure of a typical vertebra: Body, vertebral arch (pedicles, laminae), spinous process, transverse processes, articular processes
  • Intervertebral discs: Fibrocartilaginous cushions between vertebrae, shock absorbers
• Sternum: Breastbone, provides attachment for ribs and pectoral muscles
• Rib cage: Protects the heart and lungs, allows for breathing movements, composed of 12 pairs of ribs

Appendicular Skeleton

• Pectoral (shoulder) girdle: Connects upper limbs to axial skeleton, provides for movement and support
  • Clavicle (collarbone): Supports shoulder joint
  • Scapula (shoulder blade): Provides attachment for muscles of the back and shoulder
• Bones of upper extremities:
  • Humerus: Upper arm
  • Radius and ulna: Forearm
  • Carpal bones: Wrist
  • Metacarpal bones: Palm
  • Phalanges: Fingers

Pelvic Girdle

• Coxal bone: Hip bone, composed of ilium, ischium, and pubis
• Bones of lower extremities:
  • Femur: Thigh bone, largest and strongest bone in the body
  • Patella: Kneecap, protects the knee joint
  • Tibia and fibula: Lower leg
  • Tarsal bones: Ankle
  • Metatarsal bones: Sole of the foot
  • Phalanges: Toes

Skeletal Articulations (Joints)

• Functional classification: Based on the degree of movement allowed
  • Synarthroses: Immovable joints, found in the skull
  • Amphiarthroses: Slightly movable joints, found in the vertebrae
  • Diarthroses: Freely movable joints, found in the limbs
• Structural classification: Based on the type of connective tissue that binds the bones together
  • Fibrous joints: Bones connected by fibrous tissue
    • Sutures: Found in the skull
    • Syndesmoses: Joints between bones connected by ligaments, example: distal tibiofibular joint
    • Gomphoses: Joints between teeth and bone, example: tooth socket
  • Cartilaginous joints: Bones connected by cartilage
    • Synchondroses: Bones connected by hyaline cartilage, example: epiphyseal plate
    • Symphyses: Bones connected by fibrocartilage, example: pubic symphysis
  • Synovial joints: Most movable joint types
    • Structure: Synovial cavity, articular cartilage, joint capsule (fibrous capsule and synovial membrane), ligaments, menisci, bursae, tendons
    • Location: Found in the limbs, skull, and vertebral column
    • Degree of movement allowed: Vary depending on the type of joint
• Bursa: Fluid-filled sac that reduces friction between bones, tendons, and muscles
• Tendon sheath: Tubular bursa that surrounds tendons, reduces friction during movement

Classification of Diarthrotic Joints

• Uniaxial joints: Allow movement in one plane
  • Plane joint: Flat surfaces that slide over one another, example: carpals, tarsals
  • Hinge joint: Allows for flexion and extension, example: elbow, knee
  • Pivot joint: Allows for rotation, example: proximal radioulnar joint
• Biaxial joints: Allow movement in two planes
  • Condyloid joint: Allows flexion, extension, abduction, adduction, and circumduction, example: wrist, knuckles
  • Saddle joint: Allows similar movement to condyloid joint but with greater range of motion, example: carpometacarpal joint of thumb
• Multiaxial joints: Allow movement in all planes
  • Ball-and-socket joint: Allows for wide range of motion, example: shoulder, hip

Types of Synovial Joints

• Shoulder joint: Ball-and-socket joint, allows for a wide range of movements, prone to instability
• Hip joint: Ball-and-socket joint, very stable, allows for a wide range of movements
• Elbow joint: Hinge joint between humerus and ulna, allows for flexion and extension
• Knee joint: Large, complex hinge joint, allows for flexion, extension, and some rotation

Joint Disorders

• Bursitis: Inflammation of the bursa
• Tendonitis: Inflammation of a tendon
• Arthritis: Inflammation of a joint
  • Rheumatoid arthritis: Autoimmune disorder that attacks joint tissues
  • Osteoarthritis: Degenerative joint disease, wear and tear on joint cartilage
  • Gouty arthritis: Excess uric acid in blood crystallizes in joints

Types of Muscle Tissue

• Skeletal muscle: Attached to bones, responsible for voluntary movements, striated, multinucleated
• Cardiac muscle: Found in the heart, involuntary, striated, branching with intercalated discs
• Smooth muscle: Found in the walls of hollow organs, involuntary, non-striated, single-nucleated

Functional Characteristics of Muscles

• Excitability: Ability to respond to stimuli
• Contractility: Ability to shorten and thicken
• Extensibility: Ability to be stretched
• Elasticity: Ability to return to its original shape after stretching

Functions of Muscles

• Movement: Responsible for all types of body movement
• Maintain posture: Hold the body in position against gravity
• Support soft tissues: Provides support and protection for internal organs
• Regulate body temperature: Muscle contraction generates heat
• Controls passage of substances: Smooth muscles control the movement of substances through body cavities

Skeletal Muscle Anatomy

• Origin: Attachment of a muscle to the more stationary bone
• Insertion: Attachment of a muscle to the more movable bone
• Tendons: Connective tissue that attaches muscle to bone
• Aponeuroses: Broad, sheet-like tendons
• Muscle coverings:
  • Endomysium: Surrounds individual muscle fibers
  • Perimysium: Surrounds bundles of muscle fibers called fascicles
  • Epimysium: Outermost covering of the muscle, merges with the tendon
  • Deep fascia: Sheets of dense connective tissue that surround groups of muscles

Skeletal Muscle Fiber Structure

• Sarcolemma: Plasma membrane of a muscle fiber
• Sarcoplasm: Cytoplasm of a muscle fiber
• Sarcoplasmic reticulum: Network of tubules that stores calcium ions
• Myofibrils: Contractile units of the muscle fiber, composed of sarcomeres

Sarcomere Structure

• Myofilaments: Protein filaments within the sarcomere, composed of:
  • Actin: Thin filament
  • Myosin: Thick filament
• Sarcomere: Functional unit of a myofibril, extends from one Z-disc to the next
• Bands and lines/discs: Regions within the sarcomere with different protein arrangements:
  • A band: Dark band containing both myosin and actin filaments
  • I band: Light band containing only actin filaments
  • H zone: Central region of the A band containing only myosin filaments
  • M line: Midpoint of the H zone, anchors thick filaments
  • Z disc: Separates adjacent sarcomeres, anchors thin filaments

Muscle Proteins

• Actin: Provides binding sites for myosin heads
• Myosin: Thick filament, contains myosin heads that bind to actin
• Tropomyosin: Covers binding sites on actin when muscle is relaxed
• Troponin: Binds to calcium ions, moves tropomyosin off the binding sites on actin, allowing for muscle contraction
• Titin: Connects myosin to the Z disc, provides elasticity and stability to the sarcomere
• Actinin: Acts as a structural protein, connecting actin filaments to the Z disc
• Dystrophin: Helps link the sarcomere to the sarcolemma, strengthens the muscle fiber

Neuromuscular Junction

• Synaptic transmission: Communication between a nerve and a muscle fiber
• Motor neuron: Nerve that stimulates a muscle fiber
• Motor end plate: Region of the muscle fiber where the neuron makes contact
• Synaptic cleft: Small space between the neuron and the motor end plate
• Neurotransmitter: Chemical messenger released by the neuron, acetylcholine

Skeletal Muscle Physiology

• Sliding filament theory: Mechanism of muscle contraction
  • Myosin heads bind to actin filaments, pull them toward the M line, shortening the sarcomere
  • Requires calcium ions and ATP
• Excitation-contraction coupling: Sequence of events that links the nerve impulse to muscle contraction
• Mechanism of muscle contraction:
  • Nerve impulse releases acetylcholine at the neuromuscular junction
  • Acetylcholine binds to receptors on the sarcolemma, initiating an action potential
  • Action potential travels along the sarcolemma and into the T-tubules (invaginations of the sarcolemma), which are connected to the sarcoplasmic reticulum
  • Calcium ions are released from the sarcoplasmic reticulum, bind to troponin, shifting tropomyosin off the binding sites on actin
  • Myosin heads can now bind to actin, pulling it toward the M line, shortening the sarcomere
• Rigor mortis: Stiffening of muscles after death due to lack of ATP, preventing myosin from detaching from actin
• Energy demands of muscles: Muscle contraction requires a lot of energy (ATP)
  • ATP is produced by aerobic respiration (with oxygen) and anaerobic respiration (without oxygen)
  • Creatine phosphate and glycogen are used to provide energy for short-term muscle contraction
• Types of muscle fibers:
  • Red muscle fibers: Slow-twitch, oxidative, contain a lot of myoglobin (red pigment that stores oxygen), fatigue resistant, used for endurance activities
  • White muscle fibers: Fast-twitch, glycolytic, contain less myoglobin, fatigue more easily, used for short bursts of activity
  • Pink muscle fibers: Intermediate fibers, have characteristics of both red and white fibers
• Graded muscle contractions: Varying strength of muscle contraction, determined by:
  • Number of motor units recruited: More motor units = stronger contraction
  • Frequency of stimulation: Higher frequency = stronger contraction
• Muscle twitch: Contraction of a single muscle fiber in response to a single stimulus
  • Types of twitches:
    • Latent period: Short delay between stimulus and contraction
    • Contraction period: Muscle shortens
    • Relaxation period: Muscle returns to its resting length
• Isometric contraction: Muscle tension increases but length remains the same, example: holding a heavy object
• Isotonic contraction: Muscle tension remains constant while the muscle changes length, example: lifting a weight

Smooth Muscle

• Structure: Spindle-shaped fibers, not striated, single nucleus, lack sarcomeres
• Function: Controls involuntary movements of internal organs, regulates blood flow, and propels substances through body cavities
• Differences from skeletal muscle:
  • Slower contraction speed
  • Can sustain a prolonged contraction with less fatigue
  • Regulated by autonomic nervous system
• Myasthenia gravis: Autoimmune disorder that attacks acetylcholine receptors at the neuromuscular junction, results in muscle weakness and fatigue
• Duchenne muscular dystrophy: Genetic disorder that weakens muscles over time due to a lack of dystrophin, affecting mainly boys

Muscles of the Head and Neck (Selected muscles):

• Epicranius (occipitofrontalis): Raises eyebrows, wrinkles forehead
• Orbicularis oculi: Closes the eyelids
• Orbicularis oris: Closes the mouth, purses lips
• Zygomaticus major and minor: Smiling muscles
• Mentalis: Pouts the lower lip
• Platysma: Draws the corners of the mouth down, tenses the skin of the neck
• Masseter: Closes the jaw
• Temporalis: Closes the jaw, elevates and retracts mandible
• Buccinator: Compresses cheeks, helps with chewing, holds food between teeth
• Sternocleidomastoid: Flexes the neck, rotates the head to the opposite side

Anterior Trunk Muscles that Move the Arm and Shoulder (Selected muscles):

• Pectoralis major: Flexes, adducts, and rotates the arm medially
• Deltoid: Abducts, flexes, extends, and rotates the arm
• Serratus anterior: Protracts and rotates the scapula upward
• Pectoralis minor: Depresses and protracts the scapula
• Biceps brachii: Flexes the elbow, supinates the forearm
• Brachioradialis: Flexes the elbow

Posterior Trunk Muscles that Move the Arm and Shoulder (Selected muscles):

• Trapezius: Elevates, depresses, retracts, and rotates the scapula; extends the head
• Latissimus dorsi: Extends, adducts, and rotates the arm medially
• Triceps brachii: Extends the elbow
• Infraspinatus: Externally rotates the arm
• Teres major: Extends, adducts, and rotates the arm medially
• Teres minor: Externally rotates the arm
• Rhomboids major and minor: Retract and elevate the scapula

Muscles that Move the Wrist and Hand (Selected muscles):

• Flexor carpi ulnaris: Flexes and adducts the wrist
• Flexor digitorum superficialis: Flexes the middle phalanges of the fingers
• Extensor digitorum: Extends the fingers
• Extensor carpi ulnaris: Extends and adducts the wrist

Trunk Muscles that Move the Abdomen (Selected muscles):

• Rectus abdominis: Flexes the vertebral column, compresses the abdomen
• External oblique: Rotates and flexes the vertebral column, compresses the abdomen
• Internal oblique: Rotates and flexes the vertebral column, compresses the abdomen
• Transversus abdominis: Compresses the abdomen

Muscles of Respiration (Selected muscles):

• External intercostals: Elevate ribs during inspiration
• Internal intercostals: Depress ribs during forced expiration
• Diaphragm: Prime mover of inspiration

Anterior Muscles that Move the Leg at the Hip and/or Move the Knee (Selected muscles):

• Iliopsoas: Flexes the hip joint
• Sartorius: Flexes, abducts, and laterally rotates the hip joint; flexes the knee
• Gracilis: Adducts the hip joint; flexes the knee
• Adductor longus: Adducts the hip joint
• Quadriceps femoris: Extends the knee
  • Rectus femoris: Extends the knee and flexes the hip
  • Vastus lateralis: Extends the knee
  • Vastus medialis: Extends the knee
  • Vastus intermedius: Extends the knee

Posterior Muscles that Move the Leg at the Hip and/or Move the Knee (Selected muscles):

• Gluteus maximus: Extends and laterally rotates the hip
• Gluteus medius: Abducts the hip, prevents the pelvis from dipping when walking
• Gluteus minimus: Abducts and medially rotates the hip
• Hamstring muscles: Flex the knee and extend the hip
  • Biceps femoris: Extends the hip, flexes the knee, laterally rotates the leg
  • Semitendinosus: Extends hip, flexes the knee, medially rotates the leg
  • Semimembranosus: Extends the hip, flexes the knee, medially rotates the leg
• Gastrocnemius: Plantar flexes the foot
• Soleus: Plantar flexes the foot
• Tibialis anterior: Dorsiflexes and inverts the foot
• Peroneus longus: Plantar flexes and everts the foot
• Peroneus brevis: Plantar flexes and everts the foot

Test your knowledge on muscle anatomy, contractions, and their physiological roles with this quiz. It covers key concepts such as muscle fibers, neurotransmitters, and conditions affecting muscle strength. Perfect for students studying human anatomy and physiology.