chapter 10 the muscular system

muscles acting on the thigh

-muscles acting on the thigh are massive and help hold the body upright against the pull of gravity causing various movements at the hip joint -muscles acting on the leg form the flesh of the thigh. The thigh muscles cross the knee and cause its flexion or extension. Bc many of the thigh muscles also have attachments on the pelvic girdle, they can cause movement at the hip joint as well

iliopsoas

a fused muscle composed of two muscles, the iliacus and the psoas major origin- iliac bone and lower vertebrae insertion- lesser trochanter of the femur prime mover of hip flexion, keeps the upper body from falling backwards when standing erect

flexion

a movement, generally in the sagital plan, that decreases the angle of the joint and brings two bones closer together. flexion is typical of hinge joints (bending the knee or the elbow), but it is also common at ball-and-socket joints (bending forward at the hip)

tibialis anterior

a superficial muscle of the anterior leg origin- proximal tibia insertion- first cuneiform (tarsal bone) and first meta tarsal doriflexion and invert the foot

gastrocnemius

a two-bellied muscle that forms the curved calf of the posterior leg origin- it is arisen by two heads, one from each side of the distal femur insertion- through the large calcaneal tendon (achillies) into the heal of the foot (calcaneus prime mover for plantar flexion

pectoralis major

anterior trunk muscle a large fan-shaped muscle covering the upper part of the chest. it forms the anterior wall of the axilla origin- sternum, shoulder girdle (clavicle), and the first six ribs insertion- proximal end of the humerus acts to adduct and flex the arm (humerus)

diaphragm

anterior trunk muscle broad muscle; forms floor of the thoracic cavity; dome shaped in relaxed state; fibers coverage from the margins of thoracic cage toward a central tendon origin- inferior border of rib and sternum, coastal cartilages of last 6 ribs and lumbar vertebrae insertion- central tendon prime mover of inspiration. flattens on contraction resulting in increasing the vertical dimensions of thorax and increasing intra-abdominal pressure

pectoralis minor

anterior trunk muscle flat thin muscle beneath pectoralis major origin- anterior surface of ribs 3-5, near their costal cartilagess insertion- coracoid process of scapula draws scapula forward and inferiorly

Intercostal Muscles

anterior trunk muscles are deep muscles found between the ribs external intercostals raise the rib cage for breathing air in internal intercostals, which lie deep to the external intercostals, depress the rib cage, which helps to move air out of the lungs when you exhale forcibly

fixators

are specilized synergists. they hold a bone still or stabilize the origin of a prime mover so all the tension can be used to move the insertion bone. the postural muscles that stabilize the vertebral column are fixators, as are the muscles that anchor the scapulae to the thorax,

origin

attached to immovable/less movable joint

insertion

attached to the movable bone

number of origins

biceps- two origins, triceps- three, quadricepps- four ex. the biceps of the arms have two heads, or origins, and the triceps have three

every muscle is attached to

bone or other connective tissue structures at no less then two points

muscles of the lower limb

cause movement at the hip, knee, and foot joints -are among the largest, strongest muscles in the body and are specialized for walking and balancing the body -many muscles of the lower limb span two joints and can cause movement at both of them. Hence the terms origin and insertion are often interchangable in referring to these muscles -muscles originating on the leg cause assorted movements of the ankle and foot

masseter

chewing muscle covers the angle of the lower jaw origin- temporal bone insertion- mandible closes jaw by elevating the mandible

temporalis

chewing muscle is a fan-shaped muscle overlying the temporal bone origin- temporal bone insertion- mandible acts as a synergist of the masseter in closing the jaw

circumduction

combination of flexion, extension, abduction, and adduction commonly seen in ball-and-socket joints such as the shoulder. the proximal end of the limb is stationary, and its distal end moves in a circle. the limb as a whole outlines a cone

criteria used to name muscles

direction of the muscle fibers relative size of the muscle location of the muscle number of origins location of the muscles origin and insertion shape of the muscle action of the muscle

occipitalis muscle

facial muscle at posterior end of the cranial aponeurosis covers the posterior aspect of the skull and pulls the scalp posteriorly

frontalis

facial muscle covers the frontal bone origin- cranial aponeurosis insertion- skin of the eyebrow allows you to raise your eyebrows and wrinkles your forehead

zygomaticus

facial muscle extends from the corner of the mouth to the cheekbone origin- zygomatic bone insertion- skin and muscles at corner of lips called the smiling muscle- raises the corners of the mouth upward

orbicularis oris

facial muscle is the circular muscle of the lips origin- mandible and maxillia insertion- skin and muscle around mouth called the kissing muscle- closes the mouth and protrudes lips

orbicularis oculi

facial muscle run in circles around the eyes origin- frontal bone and maxilla insertion- tissue around the eyes allows you to close your eyes, squint, blink, and wink

buccinator

facial muscle and chewing muscle fleshy muscle runs horizontally across the cheek origin- mandible and maxilla near molars insertion- orbicularis oris flattens cheeks (whistling) and compresses the cheek to hold food between the teeth while chewing

circular arrangement of facial muscles

fasial muscles arranged in concentric rings found surrounding external body openings which the close by contracting. a term for such muscles is sphincters (squeezers) ex. orbicularis muscles surrounding the eyes and mouth

soleus

fleshy muscle locate deep to the grastonemius origin- proximal tibia and fibula insertion- calcaneus strong plantar flexor of the foot

abductor muscles

form the muscle mass at the medial side of each thigh origin-pelvis insertion- proximal aspect of the femur adduct or press the thighs together. since gravity does not work for them they tend to become flabby easily and need special exercise to stay toned

hamstring group

form the muscle mass of the posterior thigh and consists of three muscles the bicepps femoris, semimembraneous, and semitendinous origin- ishial tuberosity and run down the thigh insertion- both sides of the proximal thigh flex the knee and extend the hip

gluteus medius

found beneath the gluteus maximus origin- ilium insertion- proximal femur hip abductor, steadies pelvis while walking, site for giving intramuscular injections when more than 5ml is abministered

pelvic girdle is composed of

heavy, fused bones that allow little movement and so no special group of muscles is necessary to stabilize it (shoulder girdle requires several fixator muscles)

synergists

help prime movers by producing the same movement or by reducing undesirable movements.

how are muscles arranged and what does this do

in such a way that wwhatever one muscle (or group of muscles) can do, other muscles can reverse.because of this, mucles are able to bring about an immense variety of movements

muscles or the Abdominal girdle

include rectus abdominins, external and internal obliques, and transversus abdominis the fibers of each muscle or muscle pair run in a different direction forming a natural girdle reinforcing the body trunk

brachioradialis

is a fairly weak muscle origin- humerus insertion- distal forearm. it resides mainly in the forearm synergist in forearm flexion

triceps brachii

is the only muscle fleshing out the posterior humerus origin- its 3 heads arise from the shoulder girdle and proximal humerus insertion- olecranon process of the ulna prime mover of elbow extension and antagonist of the biceps brachii. boxer's muscle because it can deliver a straight-arm knockout

what happens when a muscle crosses 2 or more joints,

its contraction will cause movement in all the joints crossed unless synergists are there to stabilize them. example the finger-flexor muscles cross both the wrist and the finger joints. you can make a fist without bending your wrist because synergist muscles stabilize the finger joints

what does a muscles fascicle arrangement determine

its range of motion and power. the longer and the more nearly parallel the fascicles are to the muscles long axis, the more the muscle can shorten, but such muscles are not very powerful.

extensor digitorum longus

lateral to the tibialis anterior origin- proximal tibia and radius insertion- phalanges of toes 2-5 prime mover of toe extension and dorsiflexion of the foot

brachialis

lies deep to the biceps muscle origin- distal humerus insertion- proximal ulna elbow flexion

relative size of the muscle

longus (long) minimus (smallest) and maximus (largest example gluteus maximus is the largest of all the gluteal muscles

biceps brachii

most familiar of the forearm because it bulges when the elbow is flexed origin- by two heads from the shoulder girdle insertion- proximal radius (radial tuberosity) prime mover for flexion of the forearm and acts to supinate the forearm.

abduction

moving a limb away (generally on the frontal plan) from the midline, or the median plan of the body. it also applies to the fanning movement of the fingers or toes when the are spread apart

transverse abdominis

muscle of the abdominal girdle deepest muscle of the abdominal wall; fibers run horizontally across the abdominal wall at an angle to the external and internal obliques origin- lower ribs and iliac crest, run horizontally across the abdomen insertion- pubis compresses the abdominal contents

internal oblique

muscle of the abdominal girdle paired muscles locates deep to the external obliques, fibers run at a right angle to the external obliques origin- iliac crest insertion- last three ribs, fibers run at right angles to those of the external obliques flex the vertebral column and rotate the trunk and bend it laterally

external oblique

muscle of the abdominal girdle paired superficial muscles, make up the lateral walls of the abdomen, fibers run obliquely origin- the last 8 ribs, fibers run downwards and medially insertion- iliac crest rotate the trunk and bend it laterally

body movement occurs when

muscles contract across joints

rectus abdominis

muscles of abdominal girdle paired straplike muscles, most superficial muscles of the abdomen origin pubis insertion- sternum and 5th to 7th ribs, enclosed in an aponeurosis flex the vertebral column, compress the abdominal contents for defecation and childbirth, involved in forced breathing

antagonists

muscles that oppose or reverse a movement when a prime mover is active, its antagonist is stretched and relax. antagonists can be prime movers in their own right. Examples: biceps of the arm (prime mover of elbow flexion) is antagonized by the triceps (a prime mover of elbow extension

platysma

neck muscle is a single sheetlike muscle that covers the anterolateral neck origin- connective tissue covering of the chest muscles insertion- tissue around the mouth pulls the corners of the mouth inferiorly, producing a downward sag of the mouth

Scalenes (anterior, middle, and posterior)

neck muscle located more on lateral than anterior neck, deep to platysma and sternocleidomastoid origin- tranverse processes of cervical vertebrae insertion- anteriolaterally on ribs 1-2 flex and slightly rotate neck, elevate ribs 1-2 help in respiration

sternocleidomastoid

neck muscle pair of two-headed muscles, one found on each side of the neck origin- of the two heads of each muscle one arises from the sternum, the other from the clavicle insertion the heads fuse before inserting into the mastoid process of the temporal bone when both scm muscles contract together they flex your neck. if just one contracts, the head is rotated towards the opposite side

can muscles push

no they only pull as they contract so most often body movements are the result of the activity of two or more muscles acting together or against eachother

extension

opposite of flexion, so it is a movement that increases the angle, or the distance, between two bones or parts of the body (straightening the knee or elbow) if extension is greater than 180 it is called hyperextension

deltoid

posterior trunk muscle fleshy triangular shaped muscles that form the rounded shape of your shoulders origin winds across the shoulder girdle from the spine of the scapula to the clavicle insertion proximal humerus prime movers of arm abduction injection site when relatively small amounts of medicine must be given intamuscularly

levator scapulae

posterior trunk muscle located on the back of the neck; deep to the trapezius; thick strap like muscle border of scapula origin- transverse processes of c1-c4 vertebrae insetionmedial border of scapula elevates and adducts scapula; with fixed scapula, flexes neck to same side

trapezius

posterior trunk muscle most superficial muscles of the posterior neck and upper trunk. together they form a diamond, or kite shaped muscle mass origin-broad origin- from the occipital bone and including all cervical and thoracic vertebrae insertion- they flare laterally and insert on the scapular spine and clavicle extend the head, elevate, depress, adduct, stabilize, and rotate the scapula

erector spinae

posterior trunk muscle paired muscles deep muscles of the back. each erector spinae is a composite muscle consisting of 3 muscle columns that collectively span the entire length of the vertebral column origin- illiac crests, ribs 3-12, and vertebrae insertion- ribs, thoracic and cervical vertebrae acts as a powerful back extensors. provide resistance that helps control the action of bending over at the waist. injury to back structures causes these muscles to go into spasms and result in lower back ppain

teres minor

posterior trunk muscle rotator cuff muscle; small, elongated muscle; lies inferior to infraspinatus origin- lateral border of dorsal scapular surface insertion- greater tubercle of humerus inferior to infraspinatus insertion adducts arm

quadatus lumborum

posterior trunk muscles fleshy muscle forming part of the posterior abdominal wall origin iliac crest insertion transverse process of upper lumbar vertebrae and lower margin of 12th rib flexes vertebral column laterally when acting sepertely. when acting jointly lumbar spine is extended and 12th rib is fixed; maintains upright posture; assists in forced inspiration

latissimus dorsi

posterior trunk muscles is the large, flat muscle pair that covers the lower back origin- lower spine and ilium insertion- proximal end of humerus extend and adducts the humerus, very important in a power stroke

subscapularis

posterior trunk muscles rotator cuff muscle; forms part of the posterior wall of axilla; insertion tendon passes in front of shoulder joint origin-subscapular fossa insertion- lesser tubercle of humerus chief medial rotator of humerus; assisted by pectoralis major; helps to hold head of humerus in glenoid cavity thereby stabilizing shoulder joint

supraspinatus

posterior trunk muscles rotator cuff muscle; obscured by trapezius origin- infraspinatus fossa of the scapula insertion- humerus assists in anduction of humerus and stabilizes shoulder joint

infraspinatus

posterior trunk muscles rotator cuff muscle; partially covered by deltoid and trapezius origin- infraspinatus fossa of the scapula insertion- greater tubercle of the humerus lateral rotation of the humerus; helps hold head of humerus in glenoid cavity; stabilizes shoulder

direction of the muscle fibers

rectus (straight)- muscle fibers run parallel to the imaginary line (the midline of the body or the long axis of the bone) oblique- muscle fibers run at a slant to the imaginary line

give examples of bones with interchangeable insertions and origins

rectus femoris muscle of the anterior thigh crosses both the hip and the knee joints. its most common action is to extend the knee, in which case the proximal pelvic attachment is the origin. However, when the knee is bent (by other muscles), the rectus femoris can flex the hip and then its distal attachment on the leg is considered the origin.

rotation

rotation is movement of a bone around its longitudinal axis common movement of ball-and-socket joints and describes the movement of the atlas around the dens of the axis (shaking the head no)

pennate (feather) pattern

short fascicles attach obliquely to a central tendon. in extensor digitorum muscles of the leg, the fascicles insert into only one side of the tendon and the muscle is unipennate. if the fascicles insert into opposite sides of the tendon of form several different sides, the muscle is bipennate or multipennate, respectivley

neck muscles

small and straplike and move head and shoulder girdle

location of the muscle

some muscles are named according to the bone with which they are associated ex. temporalis and frontalis overlie the temporalis and frontalis bones

shape of the muscle

some muscles have a distictive shape that identifys them. ex. deltoid muscle is roughly triangular (deltoid means triangular

location of the muscles origins and insertions

sternocleidomastoid muscle has its origin on the sternum (sterno and the clavicle (cleido and inserts on the mastoid process of the temporal bone

gracilis

straplike superficial muscle of the medial thigh origin- body of pubis insertion- medial surface of tibia adducts thigh, flexes and medially rotates leg especially during walking

gluteus maximus

superficial muscle of hip that forms most of the flesh of the buttock origin sacrum and iliac bones insertion- gluteal tuberosity of the femur hip extensor that acts to bring the thigh in a straight line with the pelvis most important muscle for extending the hip when power is needed as in climbing the stairs or jumping

supination and pronation

supination occurs when the forearm rotates laterally so that the palm faces anteriorly and the radius and ulna are parallel. pronation occurs when the forearm rotates medially so that the palm faces posteriorly. pronation brings the radius across the ulna so that the two bones form an x.

convergent muscle

the fascicles converge toward a single insertion tendon. such a muscle is triangular or fan-shaped like the pectoralis majormuscles of the anterior thorax

parallel arrangment

the length of the fascicles runs parallel to the long axis of the muscle. these muscles are straplike. a modification of the parallel arrangement, called fusiform, results in a spindle shaped muscle with an expanded midsection like the biceps brachii muscle of the arm

the type of movement depends on

the mobility of the joint and on where thee muscle is located in relation to the joint

prime mover

the muscle that has the major responsibility for causing a particular movement

adduction

the opposite of abduction, so it is the movement of a limb toward the body midline

aponeuroses and linea alba

the perimysium of the external oblique, internal oblique, and tranversus abdominus blend into a broad aponeuroses. the perimysium of rectus abdominis also joins the aponeuroses. the line formed in the midabdominal region running from the sternum to the pubic symphysis is called linea alba

what does the muscles power depend more on

the total number of muscle cells in the muscle. the stocky bipennate and multipennate muscles, which pack in the most fibers, shorten very little but are very powerful

opposition

the touching of the thumb to tip of one of your other fingers on the same hand

why are facial muscles unique

they are inserted into soft tissues such as other muscles or skin. when they pull on the skin of the face, they permit us to smile faintly, grin widely, from, pout, deliver a kiss, etc.

quadriceps group

they form the muscle mass of the anterior thigh and consists of 4 muscles- rectus femoris and the three vastus muscles (lateralis, intermedius, medialis) origin- 3 vastus- the femur; the rectus femoris originates from the pelvis insertion- all 4 insert into the tibial tuberosity via the patellar ligament extend the knee powerfully. rectus femoris helps flex the hip. vastus lateralis and rectus femoris sometimes used as intamuscular injection sites particularly in infants

sartorius

thin strip like superficial muscle of the thigh origin- anterior iliac crest, runs obliquely across the thigh insertion- medial side of the tibia weak thigh flexor

fibularis muscles

three muscles- longus, brevis (short) and tertius (middle)- are found on the lateral part of the leg origin- fibula insertion- metatarsal bones of the foot plantar flexion and everts the foot

inversion and eversion

to invert the foot is to turn the sole medially. to evert the foot is to turn the sole laterally

dorsiflexion and plantar flexion

up and down movements of the foot at the ankle are given special names. lifting the foot so that its superior surface approches the shin is called dorsiflexion, depressing the foot is plantar fleaion

action of the muscle

when muscles are named for their actions, terms such as flexor, extensor, and adductor appear in their names. ex. the adductor muscles of the thigh all bring about its adduction and the extensor muscles of the wrist all extend the wrist.

three groups of upper limb muscles

1. muscles that arise from the shoulder girdle and cross the shoulder joint to insert into the humerus. They move the arm and include pectoralis major, latissimus dorsi, and deltoid. 2. includes muscles that enclose the humerus and insert on the forearm bone. causes movement at the elbow joint 3. includes muscles on the forearm, which insert on the hand bones and cause their movement. theses muscles are thin spindel shaped and there are many of them. have names that reflect their activities.ex. flexor carpi and flexor digitorum are found on the anterior aspect of the forearm and cause flexion of the wrist and fingers

The trunk muscles include

1. those that move the vertebral column (most of which are posterior antigravity muscles) 2. anterior thorax muscles, which move the ribs, head, and arms 3. muscles of the abdominal wall, which help to move the vertebral column and most importantly, form the muscular "natural girdle" of the abdominal body wall

serratus anterior

Anterior trunk muscle fan-shaped muscle deep to scapula; beneath and inferior to pectoral muscles on lateral rib cage origin- lateral aspect of ribs 1-8 (or 9) insertion- vertebral border of anterior surface of scapula moves scapula forward towards chest wall, rotates scapula, abduction and raising of arm