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Transverse (also called horizontal) planes divide the body into upper and lower parts. TRANSVERSE PLANE Coronal (also called frontal) planes divide it into front and back parts. CORONAL PLANE Sagittal planes divide it into left and right parts. SAGITTAL PLANE Any transverse, coronal or sagittal plane must be parallel to the examples shown in Figure 2 and the three types of planes are always at right angles to each other. The sagittal plane, which passes through the middle of the body, is known as the median plane. Other terms in common use are midsagittal instead of median; and not so frequently, parasagittal instead of sagittal. The median plane is the only plane of external symmetry in the human body; the left half is a mirror image of the right half (except in small detail). We often imagine the body to have been cut and separated at a reference plane and then viewed looking directly at the plane. This is sometimes called a cross-section. Next time you are about to eat an apple, put it upright (stalk end uppermost) on a plate and cut it across in a transverse plane. Take one part of the apple and look at the cut surface - you are looking at a transverse section of an apple. 4.2 Directional Terms In skeletal anatomy directional terms are required for describing viewing directions, relative positions of body parts and relative directions of movement. The terms we will use in this module are defined in Tables 2 and 3. Examples are used to illustrate each definition - if you have difficulty visualising the examples, refer to Figure 3 (the skeleton) in Section 5. Term Definition Example Superior Further up (with the body erect), towards the head. The head is superior to the neck. Inferior Further down (with the body erect), towards the feet. The ankle is inferior to the knee. Sagittal Nearer to, or on the sagittal plane. The big toe is on the sagittal side of the foot. Lateral Further away from the sagittal plane. The smallest toe is on the lateral side of the foot. Anterior Nearer to the front of the body. The nose is anterior to the ear. Posterior Nearer to the rear of the body. The heel is posterior to the toes. Distal Further from the point of attachment of the limb to the trunk, or further from the sagittal plane. In a broken forearm bone, the distal fragment is the part nearest the wrist. Proximal Nearer to the point of attachment of the limb to the trunk, or nearer to the sagittal plane. The elbow is proximal to the hand; the knee is proximal to the foot. Valgus Bent, or twisted away from the sagittal plane. The big toe is in valgus when bent outwards in a transverse plane. Varus Bent or twisted towards the sagittal plane. The foot is in varus when it is bent inwards in the coronal plane. TABLE 2. DIRECTIONAL TERMS. The terms in Table 3 are used when describing directions of movement of limbs or parts of limbs. During motion, the proximal part is regarded as stationary and the distal part as moving. If you have difficulty visualising the movements, try them out yourself, and refer to an anatomy and physiology textbook for illustrations. Unit 1 - Basic Anatomy 4 MEDIAN PLANE