Muscle & Integumentary System

Muscle

Specialized for transforming ATP into mechanical energy of motion.

Cardiac muscle

Muscle type found in the heart.

Skeletal muscle

Striated muscle attached to bone.

Smooth muscle

Muscle type found in the walls of hollow organs.

Muscle fiber (Muscle cell)

Individual muscle cell.

Sarcolemma

Plasma membrane of a muscle fiber.

Sarcoplasm

Cytoplasm of a muscle fiber.

Myofibrils

Contractile structures within a muscle fiber.

Myofilaments

Fibrous proteins that carry out muscle contraction.

Thick filaments

Fibrous proteins made of myosin molecules.

Thin filaments

Fibrous proteins made of actin molecules.

Elastic filaments

Springy proteins called titin that anchor thick filaments.

Sarcomere

Contractile unit of a muscle fiber.

Neuromuscular Junction

Connection between a nerve and a muscle fiber.

Denervation atrophy

Shrinkage of a paralyzed muscle when a nerve is disconnected.

Excitability/responsiveness

Ability of a muscle to respond to chemical, stretch, and electrical signals.

Conductivity

Ability of a muscle to transmit waves of excitation through muscle fibers.

Contractility

Ability of a muscle to shorten when stimulated.

Extensibility

Ability of a muscle to be stretched between contractions.

Elasticity

Ability of a muscle to return to its original rest length after stretching.

Multiunit smooth muscle

Type of smooth muscle found in large arteries and air passages.

Single-unit smooth muscle

Type of smooth muscle found in the walls of hollow organs.

Endomysium

Thin connective tissue around each muscle fiber.

Perimysium

Thicker connective tissue that wraps bundles of muscle fibers.

Epimysium

Fibrous sheath surrounding the entire muscle.

Fascia

Sheet of connective tissue that separates neighboring muscles or muscle groups.

Fusiform muscle

Muscle shape that is thick in the middle and tapered at each end.

Parallel muscle

Muscle shape with parallel fascicles.

Triangular muscle

Muscle shape that is convergent and fan-shaped.

Pennate muscle

Muscle shape that is feather-shaped.

Circular muscle

Muscle shape that forms certain body openings.

Prime Mover (Agonist)

Muscle that produces most of the force during joint action.

Synergist

Muscle that aids the prime mover.

Antagonist

Muscle that opposes the prime mover.

Fixator

Muscle that prevents a bone from moving.

Muscle Origins and Insertions

Bony attachments at the stationary and mobile ends of a muscle.

Action

Effect produced by a muscle, whether it is to produce or prevent movement.

Gastrocnemius

Muscle that usually flexes the knee.

Sphincters

Internal muscular rings that control movement of food, blood, etc.

Latissimus dorsi

Muscle that forms the mass of the buttock and is the prime hip extensor.

Gluteus medius and minimus

Muscles that abduct and medially rotate the thigh.

Adductor brevis

A muscle that adducts the thigh.

Adductor longus

A muscle that adducts the thigh.

Adductor magnus

A muscle that adducts the thigh.

Gracilis

A muscle that adducts the thigh.

Pectineus

A muscle that adducts the thigh.

Quadriceps femoris

A muscle group that extends the knee and contains the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.

Sartorius

The longest muscle in the body.

Hamstring muscles

Muscles located in the posterior (knee flexor) compartment of the thigh, including the biceps femoris, semitendinosus, and semimembranosus.

Gastrocnemius

A muscle that plantar flexes the foot and flexes the knee.

Soleus

A muscle that plantar flexes the foot.

Plantaris

A weak synergist muscle.

Tibialis anterior

A muscle that dorsiflexes the foot at the ankle.

Compartment syndrome

A common athletic injury where muscles and tendons are vulnerable to sudden and intense stress.

Pulled hamstrings

A common athletic injury involving the hamstring muscles.

Pulled groin

A common athletic injury involving the muscles in the groin area.

Rotator cuff injury

A common athletic injury involving the rotator cuff muscles in the shoulder.

Integumentary System

The skin and its accessory organs, including hair, nails, and cutaneous glands.

Epidermis

The outermost layer of the skin, composed of keratinized stratified squamous epithelium.

Dermis

The layer of skin beneath the epidermis, consisting of the papillary layer and the reticular layer.

Hypodermis

The subcutaneous tissue beneath the skin, which pads the body and binds the skin to underlying tissues.

Melanin

Pigment produced by melanocytes that determines skin color.

Hair follicle

A diagonal tube that contains the hair root.

Nail plate

The hard part of the nail, consisting of the free edge, nail body, and nail root.

Cutaneous glands

Glands located in the skin, including sweat glands and sebaceous glands.