Anatomy Lecture Exam #2

Components of skeletal system

Bones, cartilage, and joints that support, protect, and allow movement

Axial skeleton

Central 80 bones of skull, vertebral column, and thoracic cage that support and protect organs

Appendicular skeleton

Limbs plus pectoral and pelvic girdles that attach to axial skeleton and allow movement

Axial skeleton bones

Skull, auditory ossicles, hyoid, vertebral column, sternum, ribs

Appendicular skeleton bones

Clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, phalanges, hip bones, femur, patella, tibia, fibula, tarsals, metatarsals, phalanges

Clavicle attachment to sternum

Clavicle attaches to manubrium of the sternum

Frontal sinuses

Sinuses in frontal bone above the orbits

Sphenoidal sinuses

Sinuses within sphenoid bone

Maxillary sinuses

Largest sinuses, in maxilla on either side of nose

Ethmoid air cells

Cluster of small sinuses in ethmoid bone

Classification of bones

Long, short, flat, irregular, and pneumatised (bones with air spaces)

Long bones

Bones longer than they are wide, mostly in limbs (for example femur, humerus)

Short bones

Bones roughly cube-shaped (for example carpals, tarsals)

Flat bones

Thin bones that provide protection and broad surfaces for muscle attachment (for example sternum, skull)

Irregular bones

Complex shaped bones that do not fit other categories (for example vertebrae)

Pneumatized bones

Bones containing air cells or sinuses (for example ethmoid, sphenoid)

Tendon

Connective tissue that attaches muscle to bone

Ligament

Connective tissue that attaches bone to bone

Atrophy

Decrease in muscle size due to lack of use, causing weakness

Hypertrophy

Increase in muscle size due to use or training, causing greater strength

Muscle tissue characteristics

Excitability, contractility, extensibility, and elasticity

Excitability

Ability of muscle cells to respond to nerve signals

Contractility

Ability of muscle to shorten and generate force

Extensibility

Ability of muscle to stretch without damage

Elasticity

Ability of muscle to return to original length after being stretched or contracted

Skeletal muscle

Voluntary, striated muscle attached to bones for body movement

Cardiac muscle

Involuntary, striated muscle found only in heart, with intercalated discs

Smooth muscle

Involuntary, non-striated muscle found in walls of organs and vessels

Origin

Proximal or less movable attachment of a muscle

Insertion

Distal or more movable attachment of a muscle that moves toward origin during contraction

Prime mover (agonist)

Main muscle that produces a specific movement

Antagonist

Muscle that opposes the action of the agonist

Synergist

Muscle that assists agonist in performing a movement

Fixator

Muscle that stabilizes a joint, allowing other muscles to act

Motor neuron

Nerve cell that sends signals from CNS to muscle fibers

Motor unit

One motor neuron and all the muscle fibers it innervates

Fine (precise) control

Many small motor units, each controlling few fibers for delicate movements

Gross control

Fewer large motor units, each controlling many fibers for powerful movements

Fast-twitch fibers

Large-diameter fibers with more glycogen, quick powerful contractions, fatigue quickly

Slow-twitch fibers

Smaller-diameter fibers with more myoglobin, slower contractions, high endurance

Myoglobin in slow fibers

High myoglobin allows better oxygen storage and sustained activity

Glycogen in fast fibers

High glycogen provides rapid energy for short intense activity

Muscle shapes

Parallel, convergent, pennate, circular, and other shapes

Parallel muscle

Fibers run parallel to long axis and can shorten a lot (for example biceps brachii)

Convergent muscle

Fibers spread out then converge to a single tendon (for example pectoralis major)

Pennate muscle

Fibers attach at an angle to tendon, increasing force (for example deltoid, rectus femoris)

Circular muscle

Fibers arranged in rings around openings (for example orbicularis oris)

Connective tissue in muscle

Epimysium, perimysium, and endomysium surrounding muscle parts

Epimysium

Connective tissue surrounding the entire muscle

Perimysium

Connective tissue surrounding each fascicle

Endomysium

Connective tissue surrounding each individual muscle fiber

Fascicle

Bundle of muscle fibers inside a muscle

Muscle fiber

Single muscle cell containing myofibrils

Myofibrils

Rod

Sarcomere

Functional unit of muscle contraction from Z line to Z line

Thick filaments

Myosin

Thin filaments

Actin

Z line

Boundary of sarcomere where thin filaments attach

M line

Middle of sarcomere where thick filaments anchor

H band

Region in center of sarcomere with only thick filaments

Sliding filament theory

Thin filaments slide past thick filaments as cross

Cross

bridge formation

Muscle contraction sequence

Motor neuron fires, neurotransmitter released, muscle fiber depolarizes, calcium released, filaments slide and muscle contracts

Neuromuscular junction

Synapse between motor neuron and muscle fiber where neurotransmitter is released

Synovial joint

Joint with synovial cavity, fluid, capsule, and cartilage allowing free movement

Joint classification by movement

Immovable, slightly movable, and freely movable joints

Immovable joints

Joints with no movement (for example skull sutures)

Partially movable joints

Joints with limited movement (often cartilaginous joints)

Freely movable joints

Joints with wide range of motion (synovial joints)

Joint structural types

Fibrous, cartilaginous, and synovial joints

Fibrous joints

Joints joined by dense connective tissue, with little or no movement

Cartilaginous joints

Joints joined by cartilage, allowing partial movement

Synovial joints components

Joint capsule, synovial cavity, synovial fluid, articular cartilage, ligaments, sometimes menisci and bursae

Synovial fluid

Lubricating fluid in joint cavity reducing friction and nourishing cartilage

Articular cartilage

Hyaline cartilage covering bone ends in synovial joints

Meniscus

C

Bursa

Fluid

Three main joint movement types

Synarthrosis (immovable), amphiarthrosis (slightly movable), diarthrosis (freely movable)

Hinge joint

Synovial joint allowing flexion and extension in one plane (for example elbow, knee)

Knee joint

Complex hinge joint with femur, tibia, patella, menisci, ligaments, and bursae

True ribs

First seven rib pairs attaching directly to sternum via costal cartilage

False ribs

Ribs 8–10 attaching to sternum indirectly via cartilage of rib 7

Floating ribs

Ribs 11–12 not attaching to sternum

Costal vertebral joints

Joints where ribs articulate with thoracic vertebrae

Pectoral girdle

Clavicle and scapula that attach upper limb to axial skeleton

Pelvic girdle

Two hip bones (coxal bones) that attach lower limb to axial skeleton

Pelvis

Pelvic girdle plus sacrum and coccyx forming bony ring

Primary spinal curves

Thoracic and sacral curves present before birth and convex posteriorly

Secondary spinal curves

Cervical and lumbar curves that develop after birth and concave posteriorly

Kyphosis

Excessive thoracic curvature causing humpback appearance

Lordosis

Excessive lumbar curvature causing swayback appearance

Angular motion

Movement that changes the angle between bones (for example flexion, extension, abduction, adduction)

Rotational motion

Movement around bone’s long axis (for example internal and external rotation)

Flexion

Decreases angle between bones

Extension

Increases angle between bones

Abduction

Movement away from midline

Adduction

Movement toward midline

External (lateral) rotation

Rotating limb away from midline

Internal (medial) rotation

Rotating limb toward midline

Protraction

Moving a structure anteriorly (for example pushing jaw forward)