In order to describe structures in the body of an animal it is necessary to have a system for describing the position of parts of the body in relation to other parts. For example it may be necessary to describe the position of the liver in relation to the diaphragm, or the heart in relation to the lungs. Certainly if you work in a veterinary clinic for example, it will be necessary to be able to accurately describe the position of an injury. The terms used for this are called directional terms.
The most common directional terms are right and left. However, even these are not completely straightforward especially when looking at diagrams of animals. The convention is to show the left side of the animal or organ on the right side of the page. This is the view you would get looking down on an animal lying on its back during surgery or in a post-mortem. Sometimes it is useful to imagine 'getting inside' the animal (so to speak) to check which side is which. The other common and useful directional terms are listed below and shown in the diagram.
Term
Definition
Give an example...
Dorsal
Nearer the back of the animal than
The backbone is dorsal to the belly
Ventral
Nearer the belly of the animal than
The breastbone is ventral to the heart
Cranial (or anterior)
Nearer to the skull than
The heart is cranial to the colon
Caudal (or posterior)
Nearer to the tail than
The colon is cadual to the heart
Proximal
Closer to the body than (only used for structures on limbs)
The breastbone is proximal to the tailbone
Distal
Further from the body than (only used for structures on limbs)
The tailbone is more distal than the breastbone
Medial
Nearer to the midline than
The stomach is more medial than the lungs
Lateral
Further from the midline than
The lungs is more lateral than the stomach
Ipsilateral
On the same side
The right kidney is ipsilateral to the right overies
Contralateral
On the opposite side
The right kidney is contralateral to the left kidney
Rostral
Towards the muzzle
The eyes are more rostral than the stomach
Palmar
The "walking" surface of the front paw
The front pad is more palmar to the radius
Plantar
The "walking" surface of the hind paw
The hind pad is more plantar than the tarsals
Superficial
Near the outside of the animal
The skin is more superficial than the spine
Deep
Near the centre of the animal
The muscle is more deep the skin
Note that we don't use the terms superior and inferior for animals. They are only used to describe the position of structures in the human body (and possibly apes) where the upright posture means some structures are above or superior to others.
In order to look at the structure of some of the parts or organs of the body it may be necessary to cut them open or even make thin slices of them that they can be examined under the microscope. The direction and position of slices or sections through an animal's body have their own terminology.
Using the BSAVA Textbook of Veterinary Nursing, can you name & briefly describe four of the sectional planes?
median/ mid-sagittal plane - a line which divides the body into left and right halves
sagittal/paramedian plane- any line parallel to the median plane
dorsal plane- parallel to the back of the animal
traverse plane - perpendicular to the long axis of the animal
Body Cavities
Anatomically, the body can be divided into different compartments. For each of the following body cavity, can you give a description of each & at least two body organs that can be found within?
• Thorax - lungs, heart -
• Abdomen - liver, spleen - mid section
• Pelvic- colon, rectum - not physical separated (anatomical term)
• Mediastinum- heart, trachea - space in the antreia chest
• Coelom (birds & reptiles)- heart, liver
