Myology: Shapes of Muscles 13

Bipennate Unipennate Semitendinous Broad, flat muscle Ring-like

(tibialis anterior) (semimembranosus) (semitendinosus) (latissimus dorsi) (sphincter ani externus)

Digastric Multiventral Multicaudal Serrated

(omohyoideus) (rectus abdominis) (flexor digitorum prof.) (serratus anterior)

Fusiform Bicipital Tricipital (triceps surae, Quadricipital

(palmaris longus) (biceps brachii) gastrocnemius, and soleus) (quadriceps femoris)

The human body possesses a great variety of muscles.

The architecture of the muscles depends on the functional

systems in which they are involved, i.e., the kind of movements, the form of the joints with their specific ligaments,

etc. The movements themselves vary to a great extent individually.

14 Myology: Structure of the Muscular System

Synovial sheaths of flexor tendons (palmar aspect of right hand,

semischematic drawing). The flexor retinaculum protects the

flexor tendons passing through the carpal tunnel (arrow).

1

2

3

4

2

7

3

9

10

5

6

A

8

5

Joints are moved by muscles. The highly differentiated

movements are coordinated by special groups of muscles

(synergists). Their counterparts are called antagonists.

Movements can only be carried out harmoniously if the

contraction of the synergists are supported by a corresponding dilatation of the antagonists. This interaction is

controlled by the nervous system. In order to carry out

certain directions of movements, often the tendons of

muscles have to be directed by ligaments. At those places,

the tendons often develop synovial sheaths, e.g., at the

wrist joint or at the fingers.

1 Deltoid muscle

2 Biceps brachii muscle

3 Brachioradialis muscle

4 Humerus

5 Triceps brachii muscle

6 Elbow joint

7 Brachialis muscle

8 Pectoralis major muscle

9 Radius

10 Ulna

Diagram illustrating the position of the flexor and extensor

muscles of the arm and their effect on the elbow joint.

A = axis of humero-ulnar joint; arrows = direction of movements;

red = flexion; black = extension.

Ventral aspect of the right arm. The biceps muscle appears

slightly contracted. In the area of the elbow joint, several

subcutaneous veins can be recognized.

15

4

5

6

Shoulder joint (MRI scan, coronal section) (from Heuck et al.,

MRT-Atlas, 2009).

Comparative Imaging of Skeletal and Muscular Structures in MRI and X-Ray

1

2

3

1

2

3

3

8

4

5

6

4

7

5

9

10

3

4

5

Shoulder joint (X-ray, a.-p. direction) (courtesy of

Dr. Holik, Spardorf).

1 Trapezius muscle

2 Supraspinatus muscle

3 Scapula

4 Acromion

5 Head of humerus

6 Deltoid muscle

7 Cavity of shoulder joint

8 Articular cartilage

9 Articular cavity

10 Humerus

Shoulder joint (schematic drawing of the MRI scan above) (from Heuck et

al., MRT-Atlas, 2009).

Frontal section of the shoulder joint (compare with

the two pictures above).

16 Organization of the Circulatory System

Heart and related vessels in situ (anterior aspect). Anterior thoracic wall,

pericardium, and epicardium have been removed. The trachea is divided.

1

2

3

4

5

1

2

3

4

6

A

B

D

C