Anatomy: Skeletal and Muscular Systems Review

Vocabulary terms covering skeletal anatomy, joint classifications, and muscular contraction mechanisms from lecture notes.

Axial skeleton

The division of the body consisting of the head, neck, and trunk, totaling $80$ bones.

Hyoid bone

A U-shaped bone located between the chin and larynx that doesn't articulate with any other bone and is held in place by styloid processes.

Ear ossicles

Three bones per ear known as the Malleus, Incus, and Stapes.

Foramen

A round opening or passage through bone used by nerves and blood vessels to supply the face.

Foramen magnum

A passageway located in the occipital bone where the spinal cord meets the brainstem.

Sutures

Narrow gaps filled with dense fibrous tissue that join skull bones together via twisted, interlocking paths.

Pterion

The weakest part of the skull where multiple sutures converge.

Nucleus pulposus

The jelly-filled center of an intervertebral disc that is a remnant of the notochord.

Atlas

The first cervical vertebra ($C1$) which is ring-shaped and lacks a body to articulate with the skull.

Lordosis

Secondary spinal curves that are concave posteriorly, occurring in the cervical and lumbar regions.

Kyphosis

Primary spinal curves that are concave anteriorly, affecting the thoracic and sacral regions.

True ribs

The first $7$ pairs of ribs that articulate directly with the sternum.

Floating ribs

The last $2$ pairs of ribs that have no attachment at their distal end and are embedded in lumbar musculature.

Pelvic Girdle

A structure consisting of the two hip bones, sacrum, and coccyx, composed in adulthood by the fused ilium, ischium, and pubis.

Obturator foramen

A large opening encircled by the ischium and the pubis.

Trochanter

A structure in the tibia that connects to the femur side of the body.

Osteoporosis

A condition where increased activity of osteoclasts causes bones to become porous and fragile.

Synovial joints

Movable joints enclosed in an articular capsule lined with a synovial membrane that secretes lubricating fluid.

Synarthrotic

A functional classification for immovable joints, such as those forming the cranial cavity.

Amphiarthrotic

A functional classification for slightly movable joints, such as the discs between vertebrae.

Diarthrotic

A functional classification for movable joints, also known as synovial joints.

Flexion

An angular movement that decreases the angle between articulating bones, essentially closing a joint.

Extension

An angular movement that increases the angle between articulating bones, essentially opening a joint.

Intercalated discs

Specialized regions in cardiac muscle that form direct connections between adjacent cells to coordinate electrical signals and heartbeats.

Smooth muscle

Involuntary, non-striated, mononucleate muscle cells that are short and fusiform in shape, concerned with visceral functions.

Skeletal muscle

Voluntary, striated muscle packed with myofibrils that contain multinucleate cells fused together.

Sarcomere

The contractile unit within a muscle fiber composed of actin and myosin filaments.

Myosin

The protein that makes up thick filaments within a sarcomere, featuring subunits with tails and heads.

Actin

The protein that makes up thin filaments within a sarcomere, anchored in the $Z$ disk.

Sarcoplasmic reticulum

A membrane-bound structure in muscle cells that wraps around muscle fibers to store calcium ions necessary for contraction.

Troponin

A protein on actin filaments that binds calcium ions to expose myosin binding sites, enabling contraction.

Dystrophin

A cohesive protein located between the sarcolemma and myofilaments that maintains the structure of muscle fibers.

Origin

The fixed, immovable anchor point of a muscle, typically proximal to the insertion.

Insertion

The movable site where a muscle attaches to another structure, typically more distal.

Antagonist

A muscle that opposes the action of an agonist and must relax or lengthen to allow smooth motion.

Synergist

A muscle that assists the agonist by providing extra force or reducing unwanted movement.

Pinnate fibers

Muscle fibers arranged obliquely to the line of tension that can generate more force overall compared to parallel fibers.

Branchiomeric musculature

Musculature evolved from the gill system of ancestors, including muscles for the jaw, masseter, and facial expression.