Download Chapter 3

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts
no text concepts found
Transcript
Chapter 11
The Muscular System
HOW SKELETAL MUSCLES PRODUCE
MOVEMENT
Principles of Human Anatomy and Physiology, 11e
1
Muscle
Attachment
Sites:
Origin and
Insertion
• Skeletal muscles shorten & pull on the bones they are attached to
• Origin is the bone that does not move when muscle shortens
(normally proximal)
• Insertion is the movable bone
• Fleshy portion of the muscle in between attachment sites = belly
Principles of Human Anatomy and Physiology, 11e
2
Lever Systems and Leverage
• Muscle acts on rigid rod (bone)
that moves around a
fixed point called a fulcrum
• Resistance is weight of body
part & perhaps an object
• Effort or load is work done
by muscle contraction
• Mechanical advantage
– the muscle whose attachment is farther from the joint
will produce the most force
– the muscle attaching closer to the joint has the greater
range of motion and the faster the speed it can
produce
Principles of Human Anatomy and Physiology, 11e
3
First - Class Lever
• Can produce mechanical
advantage or not depending on
location of effort & resistance
– if effort is further from fulcrum
than resistance, then a strong
resistance can be moved
• Head resting on vertebral column
– weight of face is the resistance
– joint between skull & atlas is
fulcrum
– posterior neck muscles provide
effort
Principles of Human Anatomy and Physiology, 11e
4
Second - Class Lever
• Similar to a wheelbarrow
• Always produce mechanical
advantage
– resistance is always closer to
fulcrum than the effort
• Sacrifice of speed for force
• Raising up on your toes
– resistance is body weight
– fulcrum is ball of foot
– effort is contraction of calf muscles
which pull heel up off of floor
Principles of Human Anatomy and Physiology, 11e
5
Third - Class Lever
• Most common levers in the body
• Always produce a mechanical
disadvantage
– effort is always closer to fulcrum than
resistance
• Favors speed and range of motion over
force
• Flexor muscles at the elbow
– resistance is weight in hand
– fulcrum is elbow joint
– effort is contraction of biceps brachii
muscle
Principles of Human Anatomy and Physiology, 11e
6
Coordination Within Muscle Groups
• Most movement is the result of several muscle working at the
same time
• Most muscles are arranged in opposing pairs at joints
– prime mover or agonist contracts to cause the desired
action
– antagonist stretches and yields to prime mover
– synergists contract to stabilize nearby joints
– fixators stabilize the origin of the prime mover
• scapula held steady so deltoid can raise arm
Principles of Human Anatomy and Physiology, 11e
7
HOW SKELETAL MUSCLES ARE NAMED
• The most important characteristics include the direction in
which the muscle fibers run, the size, shape, action,
numbers of origins, and location of the muscle, and the sites
of origin and insertion of the muscle
• Examples from Table 11.2
– triceps brachii -- 3 sites of origin
– quadratus femoris -- square shape
– serratus anterior -- saw-toothed edge
Principles of Human Anatomy and Physiology, 11e
8
Muscles of Facial Expression
• Orbicularis oculi closes
the eye
• Orbicularis oris puckers
the mouth
Principles of Human Anatomy and Physiology, 11e
9
Muscles that Move the Mandible
• Masseter, temporalis
Arise from skull & insert
on mandible
• Protracts, elevates or
retracts mandible
– Temporalis &
Masseter elevate the
mandible (biting)
Principles of Human Anatomy and Physiology, 11e
10
Muscles
that Move
the Head
• Sternocleidomastoid muscle
– arises from sternum & clavicle & inserts onto mastoid process of
skull
– contraction of one, laterally flexes the neck and rotates face in
opposite direction
Principles of Human Anatomy and Physiology, 11e
11
Muscles of Abdominal Wall
Principles of Human Anatomy and Physiology, 11e
12
Muscles of Abdominal Wall
• sheetlike muscles
– rectus abdominis = vertically oriented
– external & internal obliques
• wrap around body to form anterior body wall
Principles of Human Anatomy and Physiology, 11e
13
Muscles Used in Breathing
• Breathing requires a change in
size of the thorax
• During inspiration, thoracic
cavity increases in size
– external intercostal lift the
ribs
– diaphragm contracts &
dome is flattened
• During expiration, thoracic
cavity decreases in size
– internal intercostal used in
forced expiration
Principles of Human Anatomy and Physiology, 11e
14
Stabilizing the Pectoral Girdle
• Anterior thoracic muscles
– Subclavius extends from 1st
rib to clavicle
– Pectoralis minor extends from
ribs to coracoid process
– Serratus anterior extends
from ribs to inner surface of
scapula
• Posterior thoracic muscle
– Trapezius extends from skull
& vertebrae to clavicle &
scapula
– Rhomboideus extends from
thoracic vertebrae to vertebral
border of scapula
Principles of Human Anatomy and Physiology, 11e
15
Axial Muscles that Move the Arm
• Pectoralis major & Latissimus dorsi extend from body
wall to humerus.
Principles of Human Anatomy and Physiology, 11e
16
Muscles that Move the Arm
• Deltoid arises from acromion & spine of scapula & inserts on arm
– abducts, flexes & extends arm
• Rotator cuff muscles extend from scapula posterior to shoulder joint to
attach to the humerus
– supraspinatus & infraspinatus: above & below spine of scapula
– subscapularis on inner surface of scapula
Principles of Human Anatomy and Physiology, 11e
17
Flexors of the Forearm (elbow)
• Biceps brachii
– scapula to radial tuberosity
– flexes shoulder and elbow &
supinates hand
• Brachialis
– humerus to ulna
– flexion of elbow
Principles of Human Anatomy and Physiology, 11e
18
Extensors of the Forearm (elbow)
• Triceps brachii
– long head arises scapula
– medial & lateral heads
from humerus
– inserts on ulna
– extends elbow & shoulder
joints
Principles of Human Anatomy and Physiology, 11e
19
Muscle that Pronate & Flex
• Flexor carpi muscles
– radialis
– ulnaris
• Flexor digitorum
muscles
Principles of Human Anatomy and Physiology, 11e
20
Muscles that Supinate & Extend
• Extensors of wrist and
fingers
– extensor carpi
– extensor digitorum
Principles of Human Anatomy and Physiology, 11e
21
Muscles Crossing the Hip Joint
• Quadriceps femoris has 4 heads
– Rectus femoris crosses hip
– 3 heads arise from femur
• Vastus lateralis, intermedius
and medialis
– all act to extend the knee
Principles of Human Anatomy and Physiology, 11e
22
Adductor Muscles of the Thigh
• Adductor group of
muscle extends from
pelvis to linea aspera
on posterior surface
of femur
– adductor longus
– gracilis
Principles of Human Anatomy and Physiology, 11e
23
Muscles of the Butt & Thigh
• Gluteus muscles
– maximus, medius &
minimus
– maximus extends hip
– medius & minimus
abduct
• Hamstring muscles
– semimembranosus
(medial)
– semitendinosus (medial)
– biceps femoris (lateral)
– extend hip & flex knee
Principles of Human Anatomy and Physiology, 11e
24
Muscles of the Calf (posterior leg)
• muscles insert onto calcaneus
– gastrocnemius arises femur
• flexes knee and ankle
– soleus arise from leg
• flexes ankle
Principles of Human Anatomy and Physiology, 11e
25
Muscles of the Leg and Foot
• Anterior compartment of leg
– extensors of ankle & toes
• tibialis anterior
• extensor digitorum longus
• Shinsplints syndrome
– pain or soreness on anterior
tibia
– running on hard surfaces
Principles of Human Anatomy and Physiology, 11e
26