Muscle Anatomy and Functions

Skeletal, cardiac, and smooth muscle tissues make up the muscular system.

Muscles attached to the skeleton, enabling body movement.

Produce movement, maintain posture, support soft tissues, guard openings, and regulate body temperature.

Individual muscle cells, and are very long.

The basic contractile unit of a muscle fiber.

Connective tissue surrounding the entire muscle.

Connective tissue surrounding muscle fascicles (bundles).

Connective tissue surrounding individual muscle fibers.

The connection between a nerve ending and a muscle fiber.

Neurotransmitter that signals muscle contraction.

Mechanism of muscle contraction where filaments slide past each other.

Filaments composed of actin, tropomyosin, and troponin.

Protein forming thick filaments and for muscle contraction.

Lengthwise threads within a muscle fiber.

Deep invaginations of the sarcolemma, which transmit the action potential.

Shortening of muscle fibers; thin filaments sliding past thick filaments.

Calcium release from the SR triggers muscle contraction.

Muscle shortens and movement occurs.

Muscle develops tension but doesn't change length.

A single motor neuron and the muscle fibers it controls.

Normal tension and firmness of a muscle at rest.

Increase in muscle tension with successive stimuli.

Sustained muscle contraction without relaxation.

Electrical signal that travels along a nerve or muscle fiber, triggering a response.

Specialized endoplasmic reticulum in muscle cells, storing calcium ions.

Ions crucial for muscle contraction by binding to troponin.

Myosin heads attaching to actin filaments, initiating the contraction cycle.

Repeated process of cross-bridge binding, pivoting, and detaching, fueled by ATP.

Enzyme that breaks down acetylcholine, ending the signal.

Return of muscle to resting state, involving Ca2+ reuptake and active site recovery.

Infoldings of the sarcolemma that transmit action potentials into the muscle fiber interior.

These hormones stimulate the synthesis of contractile proteins, leading to muscle growth and enlargement.

These hormones increase the rate of energy consumption in both resting and active muscles.

Epinephrine enhances the duration and force of muscle contractions, allowing for more powerful and sustained effort.

The length of time a muscle can sustain a certain activity.

Muscle performance is influenced by individual physical condition and the types of muscle fibers present.

An increase in muscle size due to heavy training, resulting in larger muscle fibers, more myofibrils, and increased energy reserves (mitochondria, glycogen).

A decrease in muscle size, tone, and power resulting from lack of muscle activity.

Muscles become flaccid when inactive for days or weeks, and even fibrous tissue may replace muscle fibers with prolonged inactivity.

The type of muscle tissue found exclusively in the heart, responsible for pumping blood throughout the body.

The specialized cells that make up cardiac muscle tissue, also known as cardiocytes.

Specialized junctions between cardiomyocytes that maintain structural integrity, enhance communication, and conduct electrical signals.

Intercalated discs allow cardiomyocytes to act as a single, interconnected unit, ensuring synchronized contraction of the heart.

Cardiac muscle exhibits automaticity (self-excitation), conductivity (transmitting signals), excitability (responding to stimuli), and contractility (contraction), but it does NOT experience tetany (sustained contraction).

Muscle fibers run parallel to the long axis of the muscle, creating a straight, elongated shape. Examples include the sartorius and biceps brachii.

Muscle fibers converge from a broad origin to a single, narrow tendon, allowing for force in multiple directions. The pectoralis muscles are a good example.

Muscle fibers arranged in a circle and surround openings to control their opening and closing. Examples include the orbicularis oris (lips) and the external anal sphincter.

Muscle fibers are arranged on one side of a tendon, increasing force production in a single direction. The extensor digitorum is an example.

Muscle fibers attach to a tendon on both sides, providing strong force production in one direction. The rectus femoris is an example.

Muscle fibers attach to tendons at multiple points within the muscle, maximizing force generation. A good example is the deltoid muscle.

The fixed point of attachment for a muscle. Usually, the origin is proximal (closer to the center of the body) to the insertion.

The moving point of attachment for a muscle. Often, the insertion is distal (further from the center of the body) to the origin.

These six muscles originate on the orbit and insert on the sclera of the eyeball, controlling eye position.

These muscles all end in 'glossus' and are responsible for tongue movement, crucial for speech and swallowing.

Neck muscles are divided into three groups: anterior, posterior, and lateral. They help with head movement, posture, and swallowing.

These muscles are innervated by the Facial Nerve (VII) and control various facial expressions, like smiling, frowning, and blinking.

The Masseter is the strongest jaw muscle, responsible for closing the jaw and chewing.

A group of four muscles that surround the shoulder joint, providing stability, movement, and preventing dislocation. They are: Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis.

Muscles that connect the pelvic girdle to the lower limb and contribute to movement of the thigh, leg, foot, and toes.

Muscles that cover the lateral surface of the ilium and contribute to hip extension, rotation, and abduction.

Muscles that move the thigh towards the midline of the body, responsible for adduction, flexion, and rotation of the thigh.

A two-in-one muscle that flexes the hip, consisting of the psoas major and iliacus muscles.

The major extensor muscle of the elbow joint. It originates on the scapula and humerus, has three heads (long, medial, and lateral), and inserts on the olecranon process.

A muscle in the forearm responsible for pronation (turning the palm downwards). It originates on the humerus and ulna and inserts on the radius.

A muscle in the forearm responsible for supination (turning the palm upwards). It originates on the humerus and ulna and inserts on the radius.

These muscles are located in the forearm and only their tendons cross the wrist. They control movement of the hand and fingers.

Muscles located entirely within the hand. These muscles contribute to fine motor movements and precise hand actions.

A muscle that flexes and abducts (moves away from the midline) the wrist joint. It is one of the extrinsic muscles of the hand.

A muscle that extends and abducts (moves away from the midline) the wrist joint. It is one of the extrinsic muscles of the hand.

A muscle that extends and adducts (moves towards the midline) the wrist joint. It is one of the extrinsic muscles of the hand.

Oblique muscles are found in the abdominal wall and help compress internal structures and rotate the vertebral column.

Rectus muscles are located in the abdominal wall and contribute to flexing the vertebral column and opposing the erector spinae muscles.

The most superficial oblique muscle in the abdomen, fibers run downward and medially.

Located beneath the external oblique, internal oblique fibers run upward and medially.

Deepest abdominal oblique muscle, fibers run horizontally.

Located between the xiphoid process and symphysis pubis, separated by linea alba and divided transversely by tendinous inscriptions.

Separates the thoracic and abdominal cavities, primary muscle involved in inspiration during breathing.

Muscles that support pelvic organs, flex the sacrum and coccyx, and control urine and stool passage.

Area of skin anterior to the anus, extending to vaginal opening (female) or base of testicles (male), rich in nerve endings, site of episiotomy.

Superficial muscle covering the back and neck, inserting on clavicle and scapular spine.

Deep to trapezius, originating on cervical and thoracic vertebrae and inserting on medial scapular border.

Muscle on the chest, originating along ribs and inserting on anterior scapular margin.

Muscle between sternum and humerus, adducts and medially rotates the arm, flexes the shoulder.

Muscle between vertebrae and humerus, extends the shoulder, adducts and medially rotates the arm.

These muscles straighten the leg at the knee joint, moving the lower leg forward. They originate on the femoral surface and include the powerful quadriceps femoris.

These muscles bend the leg at the knee joint, bringing the lower leg backward towards the thigh. They originate on the pelvic girdle and include the hamstring group.

A large group of four muscles located at the front of the thigh; they are the primary extensors of the knee.

A group of three muscles located at the back of the thigh; they are the primary flexors of the knee.

One of the four muscles in the quadriceps group; it is unique for crossing both the hip and knee joint.

The other three muscles of the quadriceps; they are responsible for extending the knee joint.

A bony prominence on the front of the shinbone (tibia) where the quadriceps tendon attaches.

One of the three hamstring muscles; it is located on the medial (inner) side of the thigh.

One of the three hamstring muscles; it is located on the medial (inner) side of the thigh.

One of the three hamstring muscles; it is located on the lateral (outer) side of the thigh.

The movement of the foot downwards, pointing your toes away from the shin. This is done by the calf muscles.

The movement of the foot upwards, pointing your toes towards the shin. This is done by the tibialis anterior muscle.

A major calf muscle that helps with plantarflexion and knee flexion.

A deep calf muscle that assists with plantarflexion.

A strong tendon that attaches the calf muscles to the heel bone (calcaneus).