Anatomische begrippen,
De anatomische positie[1],
Als de anatomie van de mens of een andere diersoort beschreven wordt, is het handig om het betreffende onderwerp (mens of dier) te bestuderen en te beschrijven in de standaardanatomische positie, om verwarring tussen voor of achter en onder of boven te voorkomen. Dit is meestal de positie die mens of dier in normale omstandigheden ook aanneemt. Voor mensen is de standaardanatomische positie een rechtopstaande positie, met de voeten bij elkaar (en de tenen voorwaarts gericht), met de armen langs de zijden hangend en de handpalmen voorwaarts gericht (figuur 1). De duim is dus voor de oriëntatie anatomische gedefinieerd als het meest buitenwaarts gerichte lichaamsdeel. Links en rechts zijn altijd gedefinieerd vanuit het perspectief van de patiënt. Het hart bevindt zich dus in de linkerzijde van de thorax. Een dwarsdoorsnede wordt, tenzij anders aangegeven, vanuit het voeteneinde beschouwd. Bij een dwarsdoorsnede op thoraxniveau bevindt het hart zich dus aan de rechterzijde en de wervels zich aan de onderzijde van de afbeelding. Bij viervoeters is de standaardanatomische positie dat het dier met zijn vier poten op de grond staat, met het hoofd in een neutrale positie vooruit kijkend.
Anatomical planes[1],
Three types of planes are used in anatomy.
- A sagittal plane divides the body into a left and a right part.
- The midsagittal (or median) plane is then the plane that divides the body exactly in the middle.
- A frontal plane divides the body into dorsal and ventral parts (in humans: in a front and back part).
- A transverse or horizontal plane divides the body into a cranial and caudal part, or in the case of humans into an upper and lower part.
Indication of positions[1],
For general use
Most animals usually have one end where the head and mouth are located, and one with the anus and often a tail. The end with the head or head is the cranial side, the end with the tail is the caudal side. In Latin, cranium means skull, and cauda means tail. The lungs of a dog, for example, are more cranial (towards the head) than the intestines of the dog, which are more caudal.
When one wants to indicate a location in the animal's head, one uses the term rostral for tissues or organs that lie more towards the nose, and the term caudal (again) for tissues that lie further away from the nose, and thus more towards the tail.
The part of the body that is normally facing upwards, furthest from the ground, is the dorsal side (this comes from the Latin word for back, because this usually includes the back), the opposite part, which is normally facing downwards in an animal, closest to the ground, is the ventral side (after the Latin word for belly).
Some examples: in vertebrates, the spine is located on the dorsal side of the body. The dorsal fin of a dolphin is, unsurprisingly, located on the dorsal side of the dolphin body. The udder of a cow is located on the ventral side of the cow's body. The terms can also indicate a relative direction. For example, the kidneys in a dog will be more dorsal than the intestines, which are more ventral. In the limbs or other appendages of an animal, a point closer to the body is called proximal, while a point further away is called distal.
The right and left side of an animal (sometimes referred to in Latin as dexter - right and sinister - left) are always named from the animal's point of view.
For use in human anatomy[1],
The above terms are also used in human anatomy. It should be noted that ventral and dorsal still describe the belly and back of a human being, but because a human being walks upright, these terms do not describe the sides closest to, or furthest from, the ground, as is the case with quadrupeds.
Specific terms[1],
However, other terms are also used in human anatomy, which are not used in animal anatomy.
In humans, parts of the body closer to the head are called superior (Latin for: higher), but the term cranial is also used. The parts further from the head are called caudal, but also inferior (Latin for: lower). Points at the front are called anterior (Latin for: forward), but sometimes also, as with the animals, ventral. Points at the back are called posterior (Latin: backwards) or dorsal.
Relative positions[1],
Structures close to the midline of the body are called medial, while structures that are more on the sides (more to the left or right of the center) are called lateral. Ipsilateral means that two (or more) structures are on the same side (left or right), while contralateral means that two structures are on different sides. Bilateral means that both sides are involved; unilateral means that only one of the two sides is involved.
In the case of limbs or appendages, the words proximal or distal describe whether the words central or peripheral describe whether a particular point is closer or further from the attachment of the limb or appendage to the body. The words proximal and central then indicate a point closer to the point of attachment to the body, while the words distal and peripheral indicate a point further away. The elbow is thus more proximal or central than the wrist, which is distal or more peripheral. "In the case of tubular structures in the body (intestines, blood vessels, urinary tract, etc.), the words proximal and distal can also be used to indicate points more at the beginning or the end of the tube. In a tube system in which fluids flow back and/or forth to and from an organ, one can also use the terms afferent and efferent, in which the afferent vessel or the afferent tube provides a supply to a particular organ, while the efferent vessel always drains the fluid.
Structures that are closer to the body's surface are superficially located with respect to objects that are deeper.
In the body one can still speak of visceral and parietal, where visceral means that the structure in question is attached to, or associated with, the intestines, and parietal means that it is attached to the body wall (of chest or abdomen). For example, the pleura has a part that is attached to the lungs (called the visceral part) and a part that is attached to the inside of the chest (called the parietal part).
Left: X-ray of the thorax in the frontal plane; middle: CT scan of the abdomen in the transverse plane; right: MRI scan of the brain in the sagittal plane.
| anterior | more forward (in human anatomy synonymous with ventral = on the abdominal side; in comparative anatomy synonymous with cephaal and cranial = on the head side) |
| apicaal | towards the top |
| basaal | at or near the base |
| caudaal | on the tail side (see posterior) |
| cephaal | at the head side (see anterior) |
| craniaal | at the head side (see anterior) |
| distaal | toward the protrusion |
| dorsaal | on the back (see posterior) |
| frontaal | horizontal longitudinal cut (term derived from human anatomy) |
| inferior | more down (in human anatomy synonymous with caudal) |
| lateraal | toward the side |
| mediaal | toward the middle |
| mediaan | sagittal intersection, exactly through the centre line |
| posterior | more rearward (in human anatomy synonymous with dorsal = on the dorsal side; in comparative anatomy synonymous with caudal = on the tail side |
| proximaal | in the direction of the base (used for limbs, protrusions and nerves) |
| rostraal | on the head side (used for limbs, protrusions and nerves) |
| sagittaal | Vertical longitudinal cut (head to tail) |
| superior | more up (in human anatomy synonymous with cephaal) |
| transversaal | transverse intersection |
| ventraal | on the abdominal side (see anterior) |
References:
[1] Wikipedia, the free encyclopedia, https://en.wikipedia.org/wiki/Anatomical_terms_of_location#Planes