Skeletal Muscle Anatomy and Comparative Biology

Comprehensive vocabulary flashcards detailing skeletal muscle origins, insertions, actions, functional groups, and comparative feline versus human anatomical adaptations.

Origin

The point of muscle attachment to an immovable or less moveable bone.

Insertion

The point of muscle attachment to a movable bone.

Fascia lata

Dense connective tissue (also known as the IT band or iliotibial tract) that envelops thigh muscles and extends from the iliac crest to the tibia.

Tensor fasciae latae

A muscle situated at the top of the fascia lata that tightens the fascia lata to help stabilize the lateral side of the knee joint.

Femoral Triangle Muscles (Adductors)

Muscles on the medial aspect of the thigh that originate on the pubis of the os coxa, insert at various levels on the femur, and act to press the thighs together (adduction).

Adductor femoris

The largest adductor muscle in cats (split into adductor magnus and adductor brevis in humans); originates at the pubic symphysis, inserts on the femur, and adducts, flexes, and medially rotates the thigh.

Adductor longus

An adductor muscle originating at the pubic symphysis and inserting on the femur that acts to adduct the thigh.

Pectineus

A femoral triangle muscle originating on the pubis and inserting on the femur that acts to adduct the thigh.

Iliopsoas

A muscle originating on the vertebrae and ilium and inserting on the femur that flexes and rotates the thigh.

Quadriceps femoris

Anterior thigh group of four muscles acting as the prime mover of knee extension, inserting via the quadriceps tendon onto the patella and through the patellar ligament onto the tibial tuberosity.

Rectus femoris

A quadriceps muscle originating on the ilium and inserting onto the patella and tibial tuberosity that extends the knee and flexes the hip.

Vastus lateralis

A lateral quadriceps muscle originating on the femur and inserting onto the patella and tibial tuberosity that extends the knee.

Vastus medius

A quadriceps muscle originating on the femur and inserting onto the patella and tibial tuberosity that extends the knee.

Vastus intermedius

A deep quadriceps muscle originating on the femur and inserting onto the patella and tibial tuberosity that extends the knee.

Hamstrings

Posterior thigh group of three muscles (biceps femoris, semitendinosus, semimembranosus) originating at the ischial tuberosity, innervated by the sciatic nerve, that serve as prime movers of knee flexion and thigh extension.

Semimembranosus

A hamstring muscle originating at the ischial tuberosity and inserting on the femur and tibia that flexes the knee, extends the thigh, and medially rotates the leg.

Semitendinosus

A hamstring muscle originating at the ischial tuberosity and inserting on the tibia that flexes the knee, extends the thigh, and medially rotates the leg.

Biceps femoris

A hamstring muscle originating on the ischial tuberosity and femur and inserting on the patella and tibia that flexes the knee, extends the hip and thigh, and laterally rotates the leg.

Triceps surae

A group of three posterior calf muscles (gastrocnemius, soleus, plantaris) sharing a common insertion on the calcaneus via the calcaneal (Achilles) tendon; acts as the prime mover of plantar flexion.

Gastrocnemius

The largest muscle of the triceps surae, possessing medial and lateral heads; originates on the lateral and medial condyles of the femur and inserts on the calcaneus via the calcaneal tendon to cause plantar flexion.

Soleus

A calf muscle located under the lateral head of the gastrocnemius; originates on the fibula, inserts on the calcaneus via the calcaneal tendon, and causes plantar flexion.

Plantaris

A calf muscle located under the medial head of the gastrocnemius; originates on the femur, inserts on the calcaneus via the calcaneal tendon, and causes plantar flexion.

Gluteus maximus

A gluteal muscle originating on the vertebrae and ilium and inserting on the femur that abducts the thigh (forms most of the buttocks and extends the thigh in humans, but is smaller than the medius in cats).

Gluteus medius

A gluteal muscle originating on the vertebrae and ilium and inserting on the femur that abducts the thigh and extends the hip; it is notably larger than the gluteus maximus in cats.

Caudofemoralis

A muscle found exclusively in cats (cat ONLY) originating on the caudal vertebrae and inserting on the femur that flexes the tail.

Tibialis anterior

An anterior leg muscle originating on the tibia and fibula and inserting on the medial cuneiform and metatarsal I that produces dorsiflexion and inversion.

Flexor digitorum longus

A leg muscle originating on the tibia and inserting on the phalanges that flexes the digits (toes).

Extensor digitorum longus

A leg muscle originating on the tibia and inserting on the phalanges that extends the digits (toes).

Fibularis (Peroneus)

A lateral leg muscle originating on the fibula and inserting on the medial cuneiform and metatarsal I that produces plantar flexion and eversion.

Trapezius

A muscle that moves (elevates/depresses) and stabilizes the scapula ("shrugging shoulders"); consists of a single muscle in humans but is divided into three distinct muscles in cats.

Clavotrapezius

A trapezius division in cats originating on the skull and inserting on the clavicle.

Acromiotrapezius

A trapezius division in cats originating on the spinous process of vertebrae and inserting on the acromion of the scapula.

Spinotrapezius

A trapezius division in cats originating on the spinous process of vertebrae and inserting on the scapular spine.

Deltoid

A muscle that flexes, extends, abducts, and rotates the humerus (arm); exists as a single muscle in humans and three separate muscles in cats.

Clavodeltoid (Clavobrachialis)

A deltoid division in cats originating on the clavicle and inserting on the deltoid tuberosity.

Acromiodeltoid

A deltoid division in cats originating on the acromion of the scapula and inserting on the deltoid tuberosity.

Spinodeltoid

A deltoid division in cats originating on the scapular spine and inserting on the proximal end of the ulna.

Rhomboid Group

A muscle group that stabilizes the scapula and draws it downward and medially.

Rotator Cuff

A group of four muscles (supraspinatus, infraspinatus, subscapularis, teres minor) that rotate and stabilize the humerus at the shoulder joint.

Supraspinatus

A rotator cuff muscle originating in the supraspinous fossa of the scapula and inserting on the greater tubercle of the humerus; abducts and stabilizes the humerus.

Infraspinatus

A rotator cuff muscle originating in the infraspinous fossa of the scapula and inserting on the greater tubercle of the humerus; laterally rotates and stabilizes the humerus.

Subscapularis

A rotator cuff muscle originating in the subscapular fossa and inserting on the lesser tubercle of the humerus; medially rotates and stabilizes the humerus.

Levator scapulae ventralis

A cat muscle originating on the occipital bone and atlas and inserting on the scapula; acts to elevate the scapula.

Teres major

A muscle originating at the inferior angle of the scapula and inserting on the humerus that adducts, medially rotates, and extends the humerus.

Serratus ventralis

Known as the "Boxer's muscle"; originates on the ribs and inserts on the scapula to pull the scapula forward.

Erector Spinae Group

The largest muscles of the back, consisting of three columns along the vertebral column (iliocostalis, longissimus dorsi, spinalis dorsi) that extend the neck and vertebral column.

Biceps brachii

An anterior arm muscle originating on the scapula and inserting on the radial tuberosity; acts as prime mover of elbow flexion and supinates the forearm (has two heads in humans, single head in cats).

Brachialis

An anterior arm muscle originating on the humerus and inserting on the coronoid process of the ulna that flexes the forearm.

Triceps brachii

The only muscle of the posterior arm, containing three heads (long, lateral, and medial); originates on the scapula and humerus and inserts on the olecranon process of the ulna as prime mover of elbow extension.

Pectoralis Group

Superficial chest muscles that originate on the sternum, insert on the humerus, and adduct the arm; includes four muscles in cats and two in humans.

Pectoantebrachialis

A superficial pectoral muscle found only in cats (cat ONLY) that originates on the manubrium of the sternum, inserts onto fascia near the elbow, and adducts the humerus.

Pectoralis major

A chest muscle originating on the sternum and inserting on the humerus that adducts the humerus (arm).

Pectoralis minor

A chest muscle originating on the sternum and inserting on the humerus that adducts the humerus (arm).

Xiphihumeralis

A pectoral muscle found only in cats (cat ONLY) that originates on the xiphoid process of the sternum, inserts on the humerus, and adducts the humerus (arm).

External intercostals

Breathing muscles originating on the ribs and inserting on the ribs that elevate the ribs during inhalation.

Internal intercostals

Breathing muscles originating on the ribs and inserting on the ribs that depress the ribs during exhalation.

Scalenes

Deeper neck/chest breathing muscles originating on the ribs and inserting on the cervical vertebrae that elevate the ribs and flex the neck.

Abdominal Wall Muscles

A group of four muscles (rectus abdominis, external oblique, internal oblique, transversus abdominis) with fibers running in different directions forming a natural girdle to compress the abdomen.

Tendinous intersections

Four transverse fibrous bands dividing the rectus abdominis in humans to support and reinforce the abdominal wall and viscera for upright posture (absent in cats).

Masseter

The primary chewing muscle originating on the zygomatic arch and inserting on the mandible that elevates the mandible.

Digastric

An anterior neck muscle originating on the mandible and inserting on the hyoid bone that depresses the mandible.

Mylohyoid

A neck muscle originating on the mandible and inserting on the hyoid bone that elevates the floor of the mouth.

Sternohyoid

An anterior neck muscle originating on the manubrium of the sternum and inserting on the hyoid bone.

Sternomastoid

A neck muscle in cats originating on the manubrium of the sternum and inserting on the mastoid process of the temporal bone that rotates the head and flexes the neck.

Sternocleidomastoid

A human neck muscle originating on both the manubrium and clavicle and inserting on the mastoid process of the temporal bone that rotates the head and flexes the neck (separated into two muscles in cats: sternomastoid and cleidomastoid).

Bipedal vs. Quadrupedal Muscular Adaptations

The anatomical differences between human and cat muscular systems arising because humans are bipeds (walk upright on 2 legs) whereas cats are quadrupeds (walk on all 4s and use their upper limbs for locomotion).