manatomyposterior

Photo: Matt www.flickr.com/photos/cheaterfive/

 

1. Trapezius

 

Greek, trapezoides, table shaped.

 

The left and right trapezius, viewed as a whole, create a trapezium in shape, thus giving this muscle its name.

 

Origin

Base of skull (occipital bone). Spinous processes of seventh cervical (C7) and all thoracic vertebrae, (T1-T12).

 

Insertion

Lateral third of clavicle. Acromion process. Spine of scapula.

 

Action

Upper fibres: Pull the shoulder girdle up (elevation). Helps prevent depression of the shoulder girdle when a weight is carried on he shoulder or in the hand.

Middle fibres: Retract (adduct) scapula.

Lower fibres: Depress scapula, particularly against resistance, as when using the hands to get up from a chair.

Upper and lower fibres together: Rotate scapula, as in elevating the arm above the head.

 

Nerve

Accessory X1 nerve. Ventral ramus of cervical nerves, C2, 3, 4.

 

Basic functional movement

Example (upper and lower fibres working together): Painting a ceiling.

 

Sports that heavily utilise this muscle

Examples: Shot put. Boxing. Seated rowing.

 

Common problems when muscle is chronically tight/ shortened

Upper fibres: Neck pain or stiffness, headaches.

 

Strengthening exercises

Shoulder press (upper fibres)

Dips (middle/lower fibres)

Chin-ups (middle/lower fibres)

Lateral dumb-bell raises

 

Stretches

Turn head to right and tuck chin in. Pull left shoulder down. Pull head and left shoulder apart from each other.

 

 

2. Deltoid

 

Greek, delta, fourth letter of Greek alphabet (shaped like a triangle).

 

The deltoid is composed of three part; anterior, middle and posterior. Only the middle part is multipennate, probably because its mechanical disadvantage of abduction of the should joint requires extra strength.

 

Origin

Clavicle, acromion process and spine of scapula.

 

Insertion

Deltoid tuberosity, situated halfway down the lateral surface of the shaft of the humerus.

 

Action

Anterior fibres: Flex and medially rotate the humerus.

Middle fibres: Abduct the humerus at the shoulder joint (only after the movement has been initiated by supraspinatus).

Posterior fibres: Extend and laterally rotate the humerus.

 

Nerve

Axillary nerve, C5, 6, from the posterior cord of the brachial plexus.

 

Basic functional movement

Examples: Reaching for something out to the side, or raising the arm to wave.

 

Sports that heavily utilise this muscle

Examples: Javelin. Shot put. Racket sports. Wind surfing. Weight lifting.

 

Strengthening exercises

Lateral dumb-bell raises (middle fibres)

Upright (vertical) rowing (mainly middle fibres)

Bench press (anterior fibres)

Shoulder press (mainly middle fibres)

Vertical flyes ('pec' deck/seated butterfly) (anterior fibres)

 

Self stretches

Keep your arms and torso straight and slowly bend your knees. Vary by placing back of hands on table (mainly for the anterior fibres).

Raise one arm to shoulder height. Flex the arm across to the other shoulder. Hold the raised elbow with the opposite hand and pull the elbow backward.

 

 

3. Latissimus Dorsi

 

Latin, latissimus, widest; dorsi, of the back.

 

Along with subscapularis and teres major, the latissimus dorsi forms the posterior wall of the axilla.

 

Origin

A broad sheet of tendon which is attached to the spinous processes of lower six thoracic vertebrae and all the lumbar and sacral vertebrae, (T7-S5). Posterior part of iliac crest. Lower three or four ribs. Inferior angle of the scapula.

 

Insertion

Twists to insert into the intertubercular sulcus (bicipital groove) of humerus, just below the shoulder joint.

 

Action

Extends the flexed arm. Adducts and medially rotates the humerus (i.e. draws the arm back and inwards towards the body).

 

It is one of the chief climbing muscles, since it pulls the shoulders downwards and backwards, and pulls the trunk up to the fixed arms (also active in crawl swimming stroke). Assists in forced inspiration, by raising the lower ribs.

 

Nerve

Thoracodorsal nerve, C6, 8, from the posterior cord fo the brachial plexus.

 

Basic functional movement

Example: Pushing on arms of chair to stand up.

 

Sports that heavily utilise this muscle

Examples: Climbing. Gymnastics (rings, parallel bars). Swimming. Rowing.

 

Strengthening exercises

Chin-ups (esp. wide grip)

Lat. pull-downs

Pull-overs

Seated rowing

Pulley shoulder adduction

 

Self stretches

Pull right elbow to left with left hand. Side bending to left will increase stretch.

From kneeling on all fours, sit back onto your ankles, keeping your hands fixed. Relax into it and hold for up to two minutes.

 

 

4. Triceps

 

Latin, triceps, three-headed muscle; brachii, of the arm.

 

The triceps originates from three heads and is the only muscle on the back of the arm.

 

Origin

Long head: Infraglenoid tubercle of the scapula (area just below socket of shoulder joint).

Lateral head: Upper half of posterior surface of shaft of humerus.

Medial head: Lower half of posterior surface of shaft of humerus.

 

Insertion

Olecranon process of the ulna (i.e. upper posterior area of ulna, near the point of the elbows).

 

Action

Extends (straightens) elbow joint. Long head can adduct the humerus and extend it from the flexed position. Stabilizes shoulder joint.

 

Nerve

Radial nerve, C6, 7, 8, T1.

 

Basic functional movement

Examples: Throwing objects. Pushing a door shut.

 

Sports that heavily utilise this muscle

Examples: Basketball or netball (shooting). Shot put. baseball (pitcher). Volleyball.

 

Movements or injuries that may damage this muscle

Throwing with excessive force.

 

Problems when muscle is chronically tight/ shortened

Extension deformity of elbow (elbow cannot be fully flexed); although not very common.

 

Strengthening exercises

Bench press

Push-ups

Dips

Triceps kick-back

 

Self Stretches

Keep your head up and elbow as far back as it comfortable, without hollowing your lower back.

Pull your hands towards each other. Most effective when the raised elbow is against the wall.

 

 

5. Anconeus

 

 

6. External (and internal) oblique

 

Latin, obliquus, diagonal, slanted.

 

The posterior fibres of the external oblique are usually overlapped by the Latissimus dorsi, but in some cases there is a space between the two, known as the lumbar triangle, situated just above the iliac crest. The lumbar triangle is a weak point in the abdominal wall.

 

Origin

External oblique: Lower eight ribs.

Internal oblique: Iliac crest. Lateral two-thirds of inguinal ligament.

Thoracolumbar fascia (i.e. sheet of connective tissue in lower back).

 

Insertion

External oblique: Anterior half of iliac crest, and into an abdominal aponeurosis that terminates in the linea alba (a tendinous band extending downwards from the sternum).

Internal oblique: Bottom three or four ribs, and linea alba via aponeurosis.

 

Action

Compresses abdomen, helping to support the abdominal viscera against the pull of gravity. Contraction of one side alone bends the trunk laterally to that side and rotates in to the opposite side.

 

Nerve

External oblique: Ventral rami of thoracic nerves, T5-T12.

Internal oblique: Ventral rami of thoracic nerves, T7-T12, ilioinguinal and iliohypogastric nerves.

 

Basic functional movement

Example: Digging with a shovel, raking.

 

Sports that heavily utilise these muscles

External obliques: Examples: Gymnastics. Rowing. Rugby.

Internal obliques: Examples: Golf. Javelin. Pole vault.

 

Common problems when muscles are weak

Injury to lumbar spine, because abdominal muscle tone contributes to stability of lumbar spine.

 

Strengthening exercises

Twisting it-ups

Abdominal machine crunch (for upper fibers)

Hanging leg raise

Reverse trunk twist

Side bends

 

Self Stretches

Try to twist using trunk rather than shoulders or arms.

Perform this exercise slowly, thus avoiding the tendency to use momentum.

Avoid or take care if you have back problems; check with your health professional first.

 

 

7. Supraspinatus

 

Latin, supra, above; spinatus, spine of the scapula.

 

A member of the rotator cuff, which comprise: supraspinatus, infraspinatus, teres minor, and subscapularis. The rotator cuff helps hold the head of the humerus in contact with the glenoid cavity (socket of shoulder joint) of the scapula during movements of the shoulder, thus helping to prevent dislocation of the joint.

 

Origin

Supraspinous fossa of scapula (hollow above the spine of the scapula).

 

Insertion

Greater tubercle at the top fo the humerus. Capsule of shoulder joint.

 

Action

Initiates the process of abduction at the shoulder joint, so that the deltoid can take over at the later stages of abduction.

 

Nerve

Suprascapular nerve, C4, 5, 6, from the upper trunk of the brachial plexus.

 

Basic functional movement

Example: Holding shopping bag away from side of body.

 

Sports that heavily utilise his muscle

Examples: Baseball. Golf. Racket sports.

 

Movements or injuries that may damage this muscle

Dislocation of the shoulder joint.

 

Strengthening exercises

Lateral dumb-bell raises

Seated rowing

Self Stretch

Raise one arm to shoulder height. Flex the arm across to the other shoulder. Hold the raised elbow with the opposite hand and pull the elbow backward.

 

 

8. Rhomboid major and minor

 

Greek, rhomb, a parallelogram with oblique angles and only the opposite sides equal; minor, small; major, large.

 

Rhomboideus major runs parallel to, and is often continuous with, rhomboideus minor.

 

Origin

Spinous processes of the seventh cervical and upper five thoracic vertebrae, (C7-T1).

 

Insertion

Medial (vertebral) border of scapula.

 

Action

Retracts (adducts) scapula. Stabilizes scapula. Slightly assists in outer range of adduction of arm (i.e. from arm overhead to arm at shoulder level).

 

Nerve

Dorsal scapular nerve, C4, 5.

 

Basic functional movement

Pulling something towards you, such as opening a drawer.

 

Sports that heavily utilise these muscles

Examples: Archery. Seated rowing. Wind surfing. racket sports.

 

Common problems when muscles are tight or overstretched

Tight: Soreness or aching between shoulder blades.

Overstretched: Rounded shoulders are both symptomatic of, and exacerbated by, overstretched rhomboids (which tend to get overstretched rather than become too tight).

 

Strengthening exercises

Seated rowing

Upright (vertical) rowing

Lat. pull downs

Pulley shoulder adduction

 

 

 

 

10. Teres minor

 

Latin, teres, rounded, finely shaped; minor, small.

 

A member of the rotator cuff, which comprise: supraspinatus, infraspinatus, teres minor, and subscapularis. The rotator cuff helps hold the head of the humerus in contact with the glenoid cavity (socket of shoulder joint) of the scapula during movements of the shoulder, thus helping to prevent dislocation of the joint.

 

Origin

Upper two-thirds of the lateral edge of the dorsal surface of scapula.

 

Insertion

Back of greater tubercle of humerus. Capsule of shoulder joint.

 

Action

As a rotator cuff, helps prevent upward dislocation of the shoulder joint. Laterally rotates humerus. Weakly adducts humerus.

 

Nerve

Axillary nerve, C5, 6, from the posterior cord of the brachial plexus.

 

Basic functional movement

Example: Brushing back of hair.

 

Sports that heavily utilise this muscle

Example: Back hand racket sports.

 

Movements or injuries that may damage this muscle

Dislocation of the shoulder joint.

 

Strengthening exercise

Seated rowing (limited effect)

 

 

11. Teres major

 

Latin, teres, rounded, finely shaped; major, large.

 

The teres major, along with the tendon of latissimus dorsi, which passes around it, and the subscapularis, forms the posterior fold of the axilla.

 

Origin

Lower third of the posterior surface of the lateral border of the scapula.

 

Insertion

Medial lip of intertubercular sulcus (bicipital groove) of humerus (i.e. back of upper shaft of humerus).

 

Action

Adducts humerus. Medially rotates humerus. Extends humerus from the flexed position.

 

Nerve

Lower subscapular nerve, C5, 6, 7, from the posterior cord of the brachial plexus.

 

Basic functional movement

Example: Reaching into your back pocket.

 

Sports that heavily utilise this muscle

Examples: Rowing. Cross-country skiing.

 

Movements or injuries that may damage this muscle

Sharply jerking the arm forwards, as in throwing a stone to skim it across a lake.

 

Strengthening exercises

Seated rowing

Pull-overs

PUlley shoulder adduction

 

Self stretches

Keep your arms and legs straight, flex the hips and flatten your back.

Raise one arm to shoulder height. Flex the arm across to the other shoulder. Hold the raised elbow with the opposite hand and pull the elbow backward.

 

 

 

12. External (and internal) intercostals

 

Latin, inter, between; costal, rib.

 

The lower external intercostal muscles may blend with the fibres of external oblique, which overlap them, thus effectively forming one continuous sheet of muscle, with the external intercostal fibres seemingly stranded between the ribs. There are 11 external intercostals on each side of the ribcage.

 

Internal intercostal fibres lie deep to, and run obliquely across, the external intercostals. There are 11 internal intercostals on each side of the ribcage.

 

Origin

External intercostals: Lower border of a rib.

Internal intercostals: Upper border of a rib and costal cartilage.

Insertion

External intercostals: Upper border of rib below (fibres run obliquely forwards and downwards).

Internal intercostals: Lower border of rib above (fibres run obliquely forwards and upwards towards the costal cartilage).

 

Action

Muscles contract to stabilize the ribcage during various movements of the trunk. Prevents the intercostal space from bulging out or sucking in during respiration.

 

Nerve

The corresponding intercostal nerves.

 

Sports that heavily utilise these muscles

All very active sports.

 

Common problems when muscles are chronically tight/ shortened

Kyphosis (rounded back) and depressed chest.

 

Strengthening exercise

Twisting sit-ups

 

Self stretch

Avoid or take care if you have back problems; check with your health professional first.

 

 

 

13. Spinalis thoracis

14. Longissimus thoracis} Erector Spinae (Sacrospinalis)

15. Iliocostalis thoracis

 

Latin, sacrum, sacred; spinalis, spinal.

 

The erector spinae, also called sacrospinalis, comprises three sets of muscles organized in parallel columns. From lateral to medial, they are: iliocostalis, longissimus and spinalis.

 

Origin

Slips of muscle arising from the sacrum. Iliac crest. Spinous and transverse processes of vertebrae. Ribs.

 

Insertion

Ribs. Transverse and spinous processes of vertebrae. Occipital bone.

 

Action

Extends and laterally flexes vertebral column (i.e. bending backward and sideways). Helps maintain correct curvature of spine in the erect and sitting positions. Steadies the vertebral column on the pelvis during walking.

 

Nerve

Dorsal rami of cervical, thoracic and lumbar spinal nerves.

 

Basic functional movement

Keeps back straight (with correct curvatures). Therefore maintains posture.

 

Sports that heavily utilise these muscles

Examples: All sports, especially swimming, gymnastics, and wrestling.

 

Movements or injuries that may damage these muscles

Lifting without bending the knees or keeping the back erect, or holding the object too far in front of the body.

 

Strengthening exercises

Back extension (back raise)

Lat. pull-downs

Squats

Side bends

 

Self stretches

Move towel up back with each set of stretching.

Pull knees into your chest and up towards your shoulders.

 

 

 

16. Internal oblique abdominal (see 6.)

 

 

Done