Download Answers to What Did You Learn questions

McKinley/O’Louglin
Human Anatomy, 2nd Edition
CHAPTER 12
Answers to “What Did You Learn?”
1.
The serratus anterior and the pectoralis minor protract the scapula.
2.
The levator scapulae elevates the scapula.
3.
The latissimus dorsi and pectoralis major work together to cause medial rotation
of the arm.
4.
A single muscle such as the deltoid can perform opposite functions if only part of
the muscle contracts. When the anterior fibers of the deltoid contract, the muscle
flexes the arm. When the posterior fibers contract, the muscle extends the arm.
5.
Pronator teres and pronator quadratus pronate the forearm, while supinator and
biceps brachii supinate the forearm. Specifically, biceps brachii supinates the
forearm when the forearm also is flexed.
6.
The flexors of the forearm are biceps brachii, brachioradialis, and brachialis.
7.
The extensor carpi radialis longus and the extensor carpi radialis brevis muscles
extend the wrist and abduct the hand at the wrist.
8.
The intrinsic muscles of the hand that cause abduction of the fingers are the
abductor digiti minimi, dorsal interossei, and the abductor pollicis brevis.
9.
The tensor fascia latae and gluteus maximus muscles insert on the iliotibial tract..
10.
The adductor longus, adductor brevis, adductor magnus, gracilis, and the
pectineus adduct the thigh.
11.
Adductor magnus (hamstring part), iliopsoas, sartorius, gluteus maximus,
piriformis, superior gemellus, obturator internus, inferior gemellus, obturator
externus, and quadratus femoris laterally rotate the thigh.
McKinley/O’Louglin
12.
Human Anatomy, 2nd Edition
The muscle(s) that extend the thigh are the gluteus maximus, the long head of
biceps femoris, semimembranosus, and semitendinosus.
13.
The hamstring muscles collectively extend the thigh and flex the leg.
14.
The muscles that flex the leg are the adductors (longus, brevis and magnus),
gracilis, sartorius, biceps femoris, semimembranosus, semitendinosus,
gastrocnemius, popliteus, and the plantaris.
15.
The lateral compartment muscles of the leg both evert and plantar flex the foot.
16.
The extensor digitorum brevis and extensor hallucis brevis extend the toes. The
lumbicals, dorsal interossei and plantar interossei extend the toes at the IP joints
only (and conversely flex the MP joints).
Answers to “Content Review”
1.
The trapezius can elevate, depress, retract, and superiorly rotate the scapula.
2.
The movements possible at the glenohumeral joint and the muscles that perform
each movement are: abduction (deltoid, supraspinatus), adduction (latissimus
dorsi, pectoralis major, teres major, coracobrachialis), extension (latissimus dorsi,
deltoid, teres major, teres minor, infraspinatus), flexion (pectoralis major, deltoid,
coracobrachialis, long head of biceps brachii), lateral rotation (infraspinatus, teres
minor, deltoid), and medial rotation (subscapularis, deltoid, latissimus dorsi,
pectoralis major, and teres major).
3.
The anterior compartment of the arm contains biceps brachii, brachialis, and
coracobrachialis. Biceps brachii and brachialis flex the forearm, while
McKinley/O’Louglin
Human Anatomy, 2nd Edition
coracobrachialis flexes the arm. The posterior compartment of the arm contains
anconeus and triceps brachii, which extend the forearm.
4.
The flexor digitorum superficialis originates on the medial epicondyle of the
humerus and is located in the intermediate layer of the anterior forearm. It inserts
on the middle phalanges of fingers #2-5 and it causes flexion at the wrist, MP, and
PIP joints of these fingers. The flexor digitorum profundus is located in the deep
layer of the anterior forearm and originates on the anteromedial surface of the
ulna and the interosseous membrane. Flexor digitorum profundus inserts on the
distal phalanges of fingers #2-5 and it causes flexion of the MP, PIP and DIP
joints of these fingers. At the middle of the phalanges, the tendons of the flexor
digitorum superficialis split to allow the passage of the flexor digitorum
profundus tendons to the tips of the fingers.
5.
The retinacula hold the tendons close to the bone and prevent the tendons from
“bowstringing” outward when the joint is moved.
6.
Gluteus maximus, adductor magnus (hamstring portion), the long head of biceps
femoris, semitendinosus, and semimembranosus are responsible for thigh
extension. The gluteus maximus is the prime mover of thigh extension.
7.
The three muscles that abduct the thigh are gluteus medius, gluteus minimus and
tensor fasciae latae. The first two muscles are located in the gluteal region
(buttock), while tensor fasciae latae is located in the lateral compartment of the
thigh.
McKinley/O’Louglin
8.
Human Anatomy, 2nd Edition
When you are sitting at your desk, your thighs and flexed and adducted and your
legs are flexed. The muscles that flex the thigh include iliopsoas, sartorius,
adductors, gracilis, rectus femoris and pectineus. The adductors, gracilis and
pectineus also adduct the thigh. The muscles that flex the leg include sartorius,
gracilis, adductors, biceps femoris, semimembranosus, semitendinosus,
gastrocnemius, popliteus and plantaris.
9.
Standing on ‘tip-toes’ for extended periods requires well-developed plantar
flexors: gastrocnemius and soleus [prime movers], plantaris, and the flexor
digitorum longus, flexor hallucis longus, tibialis posterior, and the fibularis longus
and brevis.
10.
Tibialis anterior and tibialis posterior are responsible for foot inversion. The
antagonists to these muscles would be fibularis longus and brevis, which evert the
foot.