Human Skeletal Muscle Anatomy and Nomenclature

Vocabulary practice flashcards covering human skeletal muscle terminology, anatomical naming principles (shape, size, fiber direction, action, attachments, location), and regional muscle functions from the head to the lower limb.

Human Skeletal Muscle Count

The human body possesses approximately 640 skeletal muscles, compared to 206 bones in the skeleton.

Deltoid Muscle

A multipennate shoulder muscle named after the triangular Greek letter delta; it suspends the weight of the upper limb and flexes, extends, and abducts the humerus at the glenohumeral joint.

Orbicularis Oculi

A circular, pepperoni-like muscle encircling the eye; its name derives from the Latin word 'orbicularis,' meaning circular.

Rhomboid Muscles

Back muscles (rhomboid major and minor) named after the Greek word 'rhombus' (a parallelogram shape) that connect the scapula to the vertebrae and retract the scapulae.

Platysma

A delicate, flat neck muscle whose name comes from the Greek word 'platus,' meaning flat and wide.

Serratus Anterior

A large muscle with slips attaching to the ribs that resembles the beveled edge of a saw (Latin 'serare,' meaning to saw); it protracts and rotates the scapula and helps pull on the ribs during breathing.

Vastus

A Latin term meaning 'great,' used to describe the three large muscles (vastus medialis, vastus intermedius, and vastus lateralis) located on the anterior thigh.

Gluteus Maximus

The largest muscle of the gluteal region, named from the Latin 'maximus' (largest or greatest); it acts as a powerful extensor of the hip joint when rising from a seated position.

Gluteus Minimus

The smallest of the three gluteal muscles, named from the Latin 'minimus,' meaning least or smallest.

Longus and Brevis

Latin descriptors of muscle length where 'longus' means long (e.g., longus capitis) and 'brevis' means short (e.g., abductor pollicis brevis).

Rectus Fiber Orientation

A fiber arrangement in which muscle fibers run straight and parallel to the midline (Latin 'rectus' meaning straight), as seen in rectus abdominis and superior rectus.

Transverse Fiber Orientation

A fiber pattern where muscle fibers run perpendicular to the midline, such as in the transverse muscle of the tongue and transversus abdominis.

Oblique Fiber Orientation

A fiber orientation where muscle fibers run diagonally at an angle or slant, seen in the external and internal abdominal oblique muscles.

Risorius Muscle

The 'smiling muscle,' named from the Latin word 'rhesus' (meaning laugh or smile), which pulls the corner of the mouth upward during laughing and smiling.

Biceps Brachii

A two-headed anterior arm muscle named from the Latin 'bi' (two) and Greek 'cephalos' or 'kephalos' (head); it functions to flex the elbow and supinate the forearm.

Sternohyoid Muscle

A neck muscle named after its skeletal attachments, originating on the posterior surface of the manubrium of the sternum and inserting onto the body of the hyoid bone.

Masseter

A primary muscle of mastication that moves the jaw in multiple directions to allow chewing, distinct in innervation and function from muscles of facial expression.

Splenius Muscles

Neck muscles named from the Greek word for 'bandage,' so called because they wrap around and cover other deeper muscles of the neck.

Scalene Muscles

Lateral neck muscles running between the vertebrae and the ribs that elevate the rib cage to assist with inhalation during deep breathing.

Sternocleidomastoid

A prominent superficial neck muscle attaching to the sternum, clavicle, and mastoid process; bilateral contraction flexes the neck (chin to sternum), while unilateral contraction causes rotation.

Trapezius

A large, superficial, trapezium-shaped muscle of the back and upper limb that stabilizes and moves the scapula, supports the head, and transfers the weight of the upper limb to the axial skeleton.

Erector Spinae

An intermediate muscle group of the back that extends into the neck, functioning to erect the spine and return the torso upright after bending over.

Intercostal Muscles

Three muscular layers located between the ribs that form a pressure wall, altering thoracic volume and pressure so air can move in and out of the lungs.

Diaphragm

A dome-shaped skeletal muscle separating the thorax and abdomen; upon contraction, it flattens and pulls down, increasing thoracic volume and drawing air into the lungs.

Levator Ani

A skeletal muscle group forming the pelvic floor that provides inferior structural support to the pelvic and abdominal contents.

Latissimus Dorsi

A broad back muscle known as the 'climber's muscle' that originates from the spine and fascia and inserts on the humerus, enabling body-weight pull-ups.

Quadriceps Femoris

A four-headed muscle group of the anterior thigh inserting via the patellar tendon into the tibia to extend the knee; its rectus femoris portion also crosses the hip to flex the hip.

Hamstrings

The posterior thigh muscle compartment (semitendinosus, semimembranosus, and biceps femoris laterally) that crosses both hip and knee joints to extend the hip and flex the knee.

Gastrocnemius and Soleus

Posterior compartment leg muscles inserting into the calcaneus (heel bone) that act as plantar flexors to lift body weight onto the tiptoes and stabilize the ankle.

Dorsiflexion

The ankle action of raising the dorsal surface of the foot and toes upward toward the shin, performed by muscles of the anterior leg compartment.

Fibularis Muscles

Muscles of the lateral leg compartment that pass around the lateral ankle along the fibula to produce eversion (turning the sole of the foot outward).