(from latin dorsum 'back') surface of an organism refers to the back, or upper side, of an organism. if talking about the skull, the dorsal side is the top. the ventral (from latin venter 'belly') surface refers to the front, or lower side, of an organism. for example, in a fish, the pectoral fins are dorsal to the anal fin, but ventral to the dorsal fin. cranial and caudal in the human skull, the terms rostral and caudal are adapted to the curved neuraxis of hominidae, rostrocaudal meaning the region on c shape connecting rostral and caudal regions. specific terms exist to describe how close or far something is to the head or tail of an animal. to describe how close to the head of an animal something is, three distinct terms are used: rostral (from latin rostrum 'beak, nose') describes something situated toward the oral or nasal region, or in the case of the brain, toward the tip of the frontal lobe. cranial (from greek κρανίον 'skull') or cephalic (from greek κεφαλή 'head') describes how close something is to the head of an organism. caudal (from latin cauda 'tail') describes how close something is to the trailing end of an organism. for example, in horses, the eyes are caudal to the nose and rostral to the back of the head. these terms are generally preferred in veterinary medicine and not used as often in human medicine. in humans, "cranial" and "cephalic" are used to refer to the skull, with "cranial" being used more commonly. the term "rostral" is rarely used in human anatomy, apart from embryology, and refers more to the front of the face than the superior aspect of the organism. similarly, the term "caudal" is used more in embryology and only occasionally used in human anatomy. this is because the brain is situated at the superior part of the head whereas the nose is situated in the anterior part. thus, the "rostrocaudal axis" refers to a c shape (see image). other terms and special cases anatomical landmarks the location of anatomical structures can also be described in relation to different anatomical landmarks. they are used in anatomy, surface anatomy, surgery, and radiology. structures may be described as being at the level of a specific spinal vertebra, depending on the section of the vertebral column the structure is at. the position is often abbreviated. for example, structures at the level of the fourth cervical vertebra may be abbreviated as "c4", at the level of the fourth thoracic vertebra "t4", and at the level of the third lumbar vertebra "l3". because the sacrum and coccyx are fused, they are not often used to provide the location.