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A&P Lab Essay

Evaluate how the name of a muscle can distinguish its location, action, shape, and function. Select five different muscles to make this distinction. Descriptive terms are used to name skeletal muscles. Some names give the location in the body. The temporalis muscle is attached to the temporal bone in the skull. The brachialis muscle is attached to the humerus bone, but brachial refers to the main artery in the arm. Some muscles are named for their origins and insertions, like the genioglossus muscle, for example, originates at the chin (geneion) and inserts in the tongue (glossus). Some muscles are named for the arrangement of the fascicle groups. For example the rectus abdominus is the straight muscle that is in the adbominus. Relative position is another naming convention. The sphincter ani externus is an elliptical shaped muscle surrounding the anus and attached to the skin. In this case ani refers to the location and externus refers to superficial, or just under the skin.

Distinct structural features are also used to name muscles. The quadriceps are named for four head muscles in the thigh; or the brevis adductor muscle which is a short muscle pulls the leg close to the body. There are also muscles named for what they do; the extensor carpi radialis longus muscle is a long muscle along the radial (lateral) border of the forearm; its primary function is extension at the carpus (wrist) (Martini, 2008). Evaluate the major muscle groups of the upper and lower limbs and relate their similarities and differences to their function. In the upper arm, the muscles responsible for flexing and extending the arm at the elbow joint are the biceps, brachialis, and triceps. In the upper leg, the muscles responsible for flexing and extending the limb at the knee are the hamstrings (biceps femoris, semimembranosus and semitendonosus muscles), the gastrocnemius (also affects foot movement), and the quadriceps femoris (YouTube, n.d.) .

In the lower arm, the two bones and muscles allow a reasonable degree of twisting (pronation and supination) between the hand and the elbow. The proximal and distal radioulnar joints make such movement possible. This movement is controlled by the pronator teres and supinator muscles. In the lower leg, the heaviest bone (Tibia) bears the weight of our bodies and transfers the weight to our feet, while the Fibula provides for additional stability and strength. The muscles of the lower leg allow us to flex and extend these limbs, but the muscles are far more powerful than in the arm, because their purpose is for moving the weight of the body in whatever direction we want to go (whether running for a touchdown or leaping to dunk a basketball). In both limbs, the two bones are joined with smaller bones which form the wrists and ankles. The small bones of the wrist and their respective joints, tendons, and muscles allow the hand-wrist to move in a reduced ball-and-socket motion (condyloid joint), which permits flexion, extension, adduction, and abduction.

Main muscles responsible for this movement are the flexors (carpi radialis and ulnaris) and the extensors (carpi radialis longus and brevis, and carpi ulnaris). The flexor and extensor retinaculum are tough bands of fiber stretching around the carpals, encasing them and providing stability and protection. Nerves and tendons pass through this area to the hands and fingers. Add the bones, joints, and small muscles of the hands and fingers, and the result is an amazing degree of dexterity, enabling us to pen a letter in detailed calligraphy, tap out tunes on a bongo drum, wiggle our fingers, play the piano, or signal to others on the freeway. We are able to move and control our fingers and thumbs individually, and opposing thumbs give us the ability to grasp and manipulate objects with great finesse and accuracy. Although a similar number of bones make up the foot, their shape and joinery differs a bit to support the function of weight bearing and locomotion.

Simply put, our feet (not our boots) are made for walking…and stomping, hopping, jumping, pedaling, running, sliding into home, kicking field goals, and tip-toeing through the tulips. Our ankles are actually hinge joints, and the bone and muscle structures of our feet clearly set these apart from their upper body counterparts. We don’t need five toes to walk (although our toes do assist with balance, we can manage without them – in fact, people who lose their thumbs often opt to have surgery to harvest a great toe to create a replacement thumb.) Our feet and toes are made to flex with our weight, literally standing up to the pressure and the stress as we run along, hopping, skipping, and jumping, and they support us in body balance. In fact, the entire weight of our bodies can be concentrated on just our toes if we pivot our weight forward and push up.

About the only thing we typically manipulate with our feet is wiggling our way into a pair of socks or shoes. The main muscles affecting movement in the joints of the ankle, foot, and toes are the anterior tibialis, soleus, and gastrocnemius. The long tendons crossing the ankle are also protected by synovial sheaths and strong ligament tissue (YouTube, n.d.). Examine the principal axial muscles of the body and distinguish their origins, insertions, actions, and innervations. The principle axial muscles arise from the axial skeleton; they control the movement of the head, the spinal column, and the rib cage; they make breathing possible. 60% of the muscles in the body are axial muscles.


Superior thorax between cartilage of 2nd rib and acromion of scapula Mandible and skin of the cheek
Depresses mandible; tenses skin of neck
Facial nerve
clavicular head attaches to sternal end of clavicle; sternal head attaches to manubrium clavicular head attaches to sternal end of clavicle; sternal head attaches to manubrium Together, they flex the neck; alone, one side bends head toward shoulder and turns face to opposite side Accessory nerve (N XI) and cervical spinal nerves (C2–C3) of cervical plexus

Spinous processes and ligaments connecting inferior cervical and superior thoracic vertebrae Mastoid process, occipital bone of skull, and superior cervical vertebrae Together, the two sides extend neck; alone, each rotates and laterally flexes neck to that side

Cervical spinal nerves
Transverse and costal processes of cervical vertebrae
Superior surfaces of first two ribs
Elevate ribs or flex neck
Cervical spinal nerves
External Coastals
Inferior border of each rib
Superior border of more inferior rib
Elevate ribs
Intercostal nerves (branches of thoracic spinal nerves)
External Oblique
External and inferior borders of ribs 5–12
Linea alba and iliac crest
Compresses abdomen, depresses ribs, flexes or bends spine
Intercostal, iliohypogastric, and ilioinguinal nerves
Xiphoid process, cartilages of ribs 4–10, and anterior surfaces of lumbar vertebrae
Central tendinous sheet
Contraction expands thoracic cavity, compresses abdominopelvic cavity
Phrenic nerves (C3–C5)
Deep Transverse Perineal
Ischial ramus
Central tendon of perineum
Stabilizes central tendon of perineum
Pudendal nerve, perineal branch (S2–S4)
Ischial spine
Lateral, inferior borders of sacrum and coccyx
Flexes coccygeal joints; tenses and supports pelvic floor
Inferior sacral nerves (S4–S5)

(Lecture 14, n.d.)
Examine the principal appendicular muscles of the body and distinguish their origins, insertions, actions, and innervations. The appendicular muscles stabilize or move components of the appendicular skeleton and include the remaining 40 percent of all skeletal muscles (Martini, 2008).

Levator Scapulae
Transverse processes of first four cervical vertebrae
Vertebral border of scapula near superior angle
Elevates scapula
Cervical nerves C3–C4 and dorsal scapular nerve (C5)
Serratus Anterior
Anterior and superior margins of ribs 1–8 or 1–9
Anterior surface of vertebral border of scapula
Protracts shoulder; rotates scapula so glenoid cavity moves superiorly (upward rotation)
Long thoracic nerve (C5–C7)
Occipital bone, ligamentum nuchae, and spinous processes of thoracic vertebrae
Clavicle and scapula (acromion and scapular spine) T12
Depends on active region and state of other muscles; may (1) elevate, retract, depress, or rotate scapula upward, (2) elevate clavicle, or (3) extend neck Accessory nerve (N XI) and cervical spinal nerves (C3–C4)

Clavicle and scapula (acromion and adjacent scapular spine)
Deltoid tuberosity of humerus
Whole muscle: abduction at shoulder; anterior part: flexion and medial rotation; posterior part: extension and lateral rotation
Axillary nerve (C5–C6)
Biceps Brachii
Short head from the coracoid process; long head from the supraglenoid tubercle (both on the scapula)
Tuberosity of radius
Flexion at elbow and shoulder; supination
Musculocutaneous nerve (C5–C6)
Lateral epicondyle of humerus, annular ligament, and ridge near radial notch of ulna
Anterolateral surface of radius distal to the radial tuberosity Supination
Deep radial nerve (C6–C8)
Palmaris Longus
Medial epicondyle of humerus
Palmar aponeurosis and flexor retinaculum
Flexion at wrist
Median nerve (C6–C7)
Extensor Digitorum
Lateral epicondyle of humerus
Posterior surfaces of the phalanges, fingers 2–5
Extension at finger joints and wrist
Deep radial nerve (C6–C8)
Adductor pollicis
Metacarpal and carpal bones
Proximal phalanx of thumb
Adduction of thumb
Ulnar nerve, deep branch (C8–T1)
Gluteus Maximus
Iliac crest, posterior gluteal line, and lateral surface of ilium; sacrum, coccyx, and thoracolumbar fascia
Iliotibial tract and gluteal tuberosity of femur
Extension and lateral rotation at hip
Inferior gluteal nerve (L5–S2)
Bicep Femoris
Inferior gluteal nerve (L5–S2)
Head of fibula, lateral condyle of tibia
Flexion at knee; extension and lateral rotation at hip
Sciatic nerve; tibial portion (S1–S3; to long head) and common fibular branch (L5–S2; to short head)
Tibialis Anterior
Lateral condyle and proximal shaft of tibia
Base of first metatarsal bone and medial cuneiform bone
Flexion (dorsiflexion) at ankle; inversion of foot
Deep fibular nerve (L4–S1)
Abductor Hallucis
Calcaneus (tuberosity on inferior surface)
Medial side of proximal phalanx of great toe
Abduction at metatarsophalangeal joint of great toe
Medial plantar nerve (L4–L5)

(Lecture 15, n.d.)
Lecture 15: Muscles of the Appendicular Skeleton. (n.d.). Lecture 15: Muscles of the Appendicular Skeleton. Retrieved October 6, 2014, from http://www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect15.html Lecture 14: Muscles III. (n.d.). Lecture 14: Muscles III. Retrieved October 6, 2014, from http://www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect14.html Muscle Actions, Origins and Insertions – Online Anatomy and Physiology Training. (n.d.). YouTube. Retrieved October 6, 2014, from http://www.youtube.com/watch?v=-C2FBZFNYXE Martini; Nath, F. (2008). Fundamentals of Anatomy & Physiology [VitalSouce bookshelf version]. Retrieved from http://digitalbookshelf.southuniversity.edu/books/0558542387/id/ch11fig3

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