Human A&P Chapter 13

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1

Describe the actions of prime movers (agonists), antagonists, synergists, and fixators.

1. prime movers (agonists) - muscles that have the major responsibility for producing a specific movement
example - biceps brachii is prime mover of forearm flexion

2. antagonists - muscles that oppose or reverse a particular movement
example - triceps brachii extends the forearm

3. synergists - assist prime movers add force to a movement
reduce undesirable or unnecessary movement
example - when a muscle crosses two or more joints,its contraction affects all the spanned joints unless other musclesact as joint stabilizers

4. fixators - synergists that immobilize a bone or muscle’s origin
give prime mover a stable base on which to act
example - scapula is held to the axial skeleton only by muscles; fixator muscles immobilize the scapula

2

Describe different patterns of fascicle arrangement and name an example of each (Figure 10.2, page 322).

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3

Infer the action of a muscle given the position of the muscle relative to the joint it crosses (Figure 10.1, page 321).

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4

Correlate fascicle arrangement with a muscle’s range of motion and power.

range of motion - the longer & more nearly parallel the muscles are to a muscle’s long axis, the more the muscle can shorten

parallel fascicles - shorten the most, but not very powerful

muscle power - depends on total number of muscle fibers in the muscle
↑ number of muscle fibers = ↑ muscle power

5

Define the terms lever, fulcrum, effort, and load.

lever - a rigid bar that moves on a fixed point called a fulcrum

fulcrum - support or point on which a lever pivots

effort - force applied to a lever

load - object moved by effort; resistance

6

Explain mechanical advantage and mechanical disadvantage. Differentiate between a power lever and a speed lever.

power lever - lever that operates at a mechanical advantage

speed lever - allows a load to be moved rapidly over a large distance with a wide range of motion

7

State the arrangement of load, fulcrum, and effort in first-class, second-class, and third-class levers (Figure 10.4, page 325). Describe an example of each in the body.

...

8

List the general characteristics of the muscles of facial expression.

control facial expressions
lie in scalp & face, just deep to the skin
thin and variable in shape & strength
insert into skin or other muscles, not bone; adjacent muscles often fused
important in nonverbal communication
all innervated by cranial nerve VII (facial nerve)

9

Describe the epicranius. List its three main parts and describe the function of each.

Epicranius (occipitofrontalis) (epi = over, cran = skull) - bipartite (two part) muscle with a wide aponeurosis connecting the two muscle parts

frontal belly (front = forehead) - raises eyebrow
occipital belly (occipito = base of skull) - pulls scalp posteriorly
epicranial aponeurosis - connective tissue sheet connecting the frontal belly & occipital belly

10

Explain the functions of each of the 11 muscles of the face.

Corrugator supercilii (corrugo = wrinkle; supercilium = eyebrow) - draws eyebrows together

Orbicularis oculi (orb = circular; ocul = eye) - closes eye

Levator labii superioris (leva = raise; labi =lip; superior = above) - opens lips

Zygomaticus (zygomatic = cheekbone) - raises lateral corners of mouth upwards (smiling muscle)

Buccinator (bucc = cheek) - compresses cheek

Risorius (risor = laughter) - draws corner of lip laterally (synergist of zygomaticus)

Orbicularis oris (or = mouth) - closes lips

Mentalis (ment = chin) - wrinkles chin

Depressor labii inferioris (depressor = depresses; infer = below) - draws lower lip inferiorly

Depressor anguli oris (angul = angle, corner; or = mouth) - draws corners of lip downwards & laterally

Platysma (platy = broad, flat) - tenses skin of neck

11

List the general characteristics of the muscles of mastication.

Characteristics
mastication - chewing

buccinator muscle - aids muscles of mastication by compressing the cheek and keeping food between the grinding surfaces of the teeth during chewing

all are innervated by cranial nerve V (trigeminal nerve)

12

Name the cranial nerve that innervates the following groups of muscles: muscles of facial expression, muscles of mastication, and extrinsic tongue muscles.

...

13

Describe the functions of each of the 4 muscles of mastication

Temporalis (tempora = time) - a prime mover of jaw closure; elevates & retracts mandible

Masseter (maseter = chewer) - another prime mover of jaw closure; elevates mandible

Lateral pterygoid (lateral = away from median plane; pterygoid = winglike) - forward sliding & side-to-side grinding movements of lower teeth

Medial pterygoid (medial = toward median plane) - promotes side-to-side grinding movements

14

Differentiate between intrinsic and extrinsic tongue muscles.

intrinsic tongue muscles - learn later in A&P II
made up of muscle fibers that curl, squeeze, and fold during speaking & chewing
change the shape of tongue & make it nimble
do not really move the tongue

extrinsic tongue muscles - learn now
anchor & move the tongue
all are innervated by cranial nerve XII (hypoglossal

15

Describe the functions of each of the 3 muscles promoting tongue movement.

Genioglossus (geni = chin; glossus = tongue) - protracts tongue

Styloglossus (stylo = pertaining to styloid process) - retracts & elevates tongue

Hyoglossus (hyo = pertaining to hyoid bone) - depres

16

Differentiate between suprahyoid and infrahyoid muscles.

suprahyoid muscles - above (superior to) the hyoid bone
infrahyoid muscles - below (inferior to) the hyoid bone

17

Describe the functions of each of the 4 suprahyoid muscles and 5 infrahyoid muscles.

Digastric (di = two; gaster = belly) - anterior & posterior bellies united by a central tendon connected to hyoid bone; open mouth and depress mandible
Mylohyoid (myle = molar) - elevates hyoid bone & floor of mouth
Stylohyoid - elevates & retracts hyoid bone
Geniohyoid ( geni = chin) - pulls hyoid bone superiorly & anteriorly

Thyrohyoid (thyro = thyroid cartilage) - superior continuation of sternohyoid muscle; depresses hyoid; elevates larynx if hyoid fixed
Sternothyroid (sterno = sternum) - pulls larynx & hyoid bone inferiorly
Omohyoid (omo = shoulder) - superior & inferior bellies originate at scapula; depresses & retracts hyoid
Sternohyoid - pulls larynx & hyoid bone inferiorly
Pharyngeal constrictor muscles - superior, middle, & inferior muscles; constricts pharynx when swallowing

18

Describe the muscular actions that occur during swallowing.

1.suprahyoid muscles pull hyoid bone upward & forward, widening the pharynx (muscular tube from region posterior to nasal cavities to esophagus); larynx (voice box) is also pulled upward which covers it with the epiglottis (elastic cartilage at back of throat which prevents inhalation of food into the lungs)

2. small muscles elevate the soft palate (soft portion in the roof of the mouth) to close off the nasal passages; prevents food from entering the nasal cavity

3. pharyngeal constrictor muscles propel food into the esophagus

4. infrahyoid muscles return hyoid bone and larynx to their more inferior positions as swallowing ends

19

Describe the functions of each of the anterolateral neck muscles.

Sternocleidomastoid (sterno = sternum, cleido = clavicle, mastoid = mastoid process) - flexes & laterally rotates head

suprahyoid & infrahyoid muscles are synergists to head flexion

Scalene muscles (scalene = uneven) - anterior, middle, posterior; elevate first two ribs to aid in inspiration

20

Describe the functions of each of the intrinsic muscles of the back.

Splenius (splenion = bandage) - extends or hyperextends head

Erector spinae- prime mover of back extension; consists of three columns on each side of vertebral column
Iliocostalis (ilio = ileum; cost = rib) - lateral
Longissimus (longissimus = longest) - intermediate
Spinalis (spin = vertebral column, spine) - medial

Semispinalis (semi = half) - composite muscle (capitis, cervicis, thoracis); extends vertebral column & head and rotates them to opposite side

Quadratus lumborum (quad = four-sided; lumb = lumbar region) - flexes vertebral column laterally when muscles act separately on each side

21

Contrast the functions of the external intercostals and internal intercostals. Explain how the intercostal muscles aid in breathing

...

22

Describe the diaphragm and list its 3 openings. Explain how its contraction and relaxation cause inspiration and expiration.

prime mover of inspiration
broad, dome-shaped structure
flattens on contraction
increases thorax area when contracted
large central tendon
openings for aorta, inferior vena cava, & esophagus
innervated by phrenic nerves

23

Describe the direction of muscle fibers in the 4 muscles of the abdominal wall. Explain how this arrangement contributes to abdominal wall strength. Describe the linea alba.

1.External oblique (oblique = running at an angle) - largest, most superficial of the 3 lateral muscles; flexes vertebral column & compresses abdominal wall

2. Internal oblique - most fibers run upward & medially; same action as external oblique

3. Transversus abdominis (transverse = running straight across; abdom = abdomen) - deepest, horizontal fibers; compresses abdominal contents

4. Rectus abdominis (rectus = straight) - medial superficial; “six pack”/“washboard” abs; flexes & rotates lumbar regiono f vertebral column

linea alba (“white line”) - fused rectus abdomen is aponeuroses

24

Describe the 2 muscles of the pelvic diaphragm. Describe their functions.

1. Levator ani (ani = anus) - broad, thin tripartite muscle (2 parts visible in diagram); supports pelvic organs

2. Coccygeus (coccy = coccyx) - supports pelvic organs

close inferior outlet of the bony pelvis
support pelvic organs
elevate pelvic floor to help release feces
resist increased intra-abdominal pressure to prevent expulsion of contents of bladder, rectum, & uterus

25

26. Define the term perineum. Name the 2 sphincters and describe their functions.

Perineum - body region inferior to the pelvic diaphragm; stretches between the two sides of the pubic arch

1. External urethral sphincter (sphin = squeeze) - urination
2. External anal sphincter - defecation

26

27. Explain the functions of each of the 3 muscles of the anterior thorax and 3 muscles of the posterior thorax

1. Subclavius (sub = under, beneath; clav = clavicle) - helps stabilize & depress pectoral girdle

2. Pectoralis minor (pectus = chest, breast; minor = lesser) - with ribs fixed, pulls scapula forward & downward

3. Serratus anterior (serratus = saw) - rotates scapula

1. Trapezius (trapezion = irregular four-sided figure) - prime mover of shoulder elevation

2. Rhomboids (rhomboid = diamond shaped) - minor and major; stabilize scapula

3. Levator scapulae - another prime mover of shoulder elevation

27

28. Describe the functions of each of the 9 muscles crossing the shoulder joint.

Deltoid (delta = triangular) - prime mover of arm abduction

Pectoralis major (pectus = breast, chest; major = larger) - prime mover of arm flexion; adducts arm

Latissimus dorsi (latissimus = widest; dorsi = back) - prime mover of arm extension; adducts arm

Rotator cuff muscles (4) - reinforce shoulder capsule; act as synergists & fixators for arm movements

Subscapularis (sub = under; scapular = scapula)
Supraspinatus (supra = above, over; spin = spine)
Infraspinatus (infra = below)
Teres minor (teres = round; minor = lesser)

Coracobrachialis (coraco = coracoid; brachi = arm) - synergist; doesn’t contribute to shoulder joint reinforcement; flexes and adducts humerus

Teres major (teres = round; major = greater) - extends and adducts humerus

28

29. List 4 rotator cuff muscles

Subscapularis (sub = under; scapular = scapula)
Supraspinatus (supra = above, over; spin = spine)
Infraspinatus (infra = below)
Teres minor (teres = round; minor = lesser)

29

30. Define the term fascia.

layers of connective tissue that cover and separate muscles

30

31. Upper arm: explain the general functions of muscles in the anterior and posterior compartments; list which muscles are located in each compartment

Posterior muscles - forearm extension

Triceps brachii (triceps = three heads; brachi = arm) - prime mover of forearm extension

Anconeus (acon = elbow) - weak synergist of triceps brachii

Anterior muscles - forearm flexion
Biceps brachii (biceps = two heads) - flexes forearm & supinates forearm

Brachialis - deep to biceps; strongest forearm flexor

Brachioradialis ( radi = radius, ray) - synergist in forearm flexion; helps stabilize elbow

31

32. Forearm: explain the general functions of muscles in the anterior and posterior compartments; list which muscles are located in each compartment; name which muscles pronate or supinate the forearm

Posterior compartment - extends wrist & fingers
Anterior compartment - flexes wrist & fingers

Pronator quadratus (pronation + turning palm posteriorly, or down; quad = square, four-sided) - pronates forearm

Pronator teres (teres = round) - pronates forearm

Supinator (supination = turning palm anteriorly or upward) - synergist with biceps brachii in supinating forearm

32

33. Describe the actions of the intrinsic muscles of the hand.

Intrinsic hand muscles - small muscles lying entirely in the hand
all found in the palm; no muscles on hand’s dorsal side

move metacarpals & fingers

control precise movements (e.g., threading a needle)

main finger abductors & adductors

produce opposition of thumb

33

34. Thigh: explain the general functions of muscles in the anterior, posterior, and medial compartments; identify which muscles are thigh flexors and which are thigh extenders

...

34

35. List 3 hamstring muscles.

Biceps femoris (biceps = two heads)
Semitendinosus (semi = half; tendinosus = tendon)
Semimembranosus (semi = half; membranosus = membrane)

35

36. Explain the functions of the 3 gluteal muscles.

...

36

37. Explain the importance of thigh abduction and thigh adduction.

thigh abduction & adduction are important to balance; those movements shift the body’s weight over the limb that is on the ground

“pulled groin” - strain or stretching of this muscle group

37

38. Describe the structure and function of deep leg fascia

Deep leg fascia - is continuous with fascia lata of the thigh
prevents excessive swelling of muscles during exercise
aids return of venous blood to the heart

38

39. Leg: explain the general functions of the anterior, lateral, and posterior compartments; list which muscles are located in each compartment

Anterior compartment - dorsiflexes foot & extends toes
Lateral compartment - plantar flexes & everts foot
Posterior compartment - plantar flexes foot & flexes toes

39

40. Describe the functions of the intrinsic foot muscles.

help flex, extend, abduct, & adduct toes
support foot arches
one muscle on superior aspect of foot; several muscles on plantar aspect (sole)


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