Directional Terms & Planes

What are "Cells"?

A Cell is the smallest unit of life. Organelles within the cell are specialized bodies performing specific cellular functions. Cells themselves may be specialized. Thus, there are nerve cells, bone cells, and muscle cells.

What is "Homeostasis"?

A characteristic of all living systems is homeostasis, or the maintenance of stable, internal conditions within specific limits. In many cases, stable conditions are maintained by negative feedback. Almost all homeostatic control mechanisms are negative feedback mechanisms. These mechanisms change the variable back to its original state or "ideal value". EXAMPLE: Have you ever wondered why your dog pants on hot days? ANSWER: It's because your dog is trying to maintain homeostasis. Homeostasis is a word that biologists use to describe how a living organism regulates its internal environment to maintain stability. One very important part of homeostasis is body temperature. On any particular day, the temperature might change by as much as 50º. In order for an organism's chemical reactions to continue as they should, the temperature on the inside of the organism needs to remain the same. QUESTION? When your body temperature begins to rise, what happens? ANSWER: You begin to sweat. Sweating is your body's way of cooling down, thus maintaining homeostasis. As the liquid dries on your skin, it cools your skin and lowers your temperature. Because dogs do not have sweat glands, they pant. Dogs have just a few sweat glands in their paws, so no matter how much they sweat; sweating could never cool them off. That's where the tongue-hanging out, mouth-open dog panting comes in. The major blood vessel in a dog's head runs very close to the surface of its nose. The fresh air a dog breathes works like a fan to cool the blood in the nose, which then circulates through the dog's body to cool the rest of the body. The dog then exhales the warm air out its mouth.

Disease

A result from abnormalities of the body that prevent the body from maintaining health or Homeostasis.

What is an "Organ"?

An organ is a group of different kinds of tissues working together to perform a particular activity. The heart is an organ composed of muscle, nervous, connective, and epithelial tissues.

What is an "Organ System"?

An organ system is two or more organs working together to accomplish a particular task. The digestive system, for example (at right), involves the coordinated activities of many organs, including the mouth, stomach, small and large intestines, pancreas, and liver.

What is an "Organism"?

An organism is a system possessing the characteristics of living things including the ability to: -obtain and process energy, -respond to environmental changes, -reproduce.

Anatomy

Anatomy is the study of the structure and relationship between body parts.

Directional Terms

Directional terms are used to describe the relative position of one body part to another. This standardized set of terms can be used across species.

Histology

Is the study of cells and microscopic anatomy.

Physiology

Physiology is the study of the function of body parts and the body as a whole.

Negative Feedback

Process that decreases disturbance added to a system.

Pathology

The study of diseases.

kinesiology

The study of muscular activity and the mechanics of body movement.

Plane

a surface by which any two points can be connected by a straight line

lateral

away from or relatively farther from the median plane

external (outer)

away from the center of an organ or structure

distal

away from the main mass or origin

internal (inner)

close to or in the direction of the center of an organ, body cavity or structure

dorsal plane

divides at right angles to the median transverse planes and thus divides the body into dorsal and ventral portions. Dorsal plane divides the body into the back (dorsum) and belly (ventral) portions. Also called the frontal plane.

transverse plane

divides the body at a right angle to its long axis. Transverse plane divides the body into front (cranial) and back (caudal) portions.

median plane (midline)

divides the body longitudinally into equal right and left halves. Also called midline or midsagittal plane. Envision an imaginary line going right down the middle of the body.

sagittal plane

divides the body parallel to the median plane. Sagittal plane is the plane that divides the body into UNEQUAL right and left sides.

deep

relatively near the center of the body or the center of a solid organ

proximal

relatively near the main mass or origin

superficial

relatively near the surface of the body, or the surface of a solid organ

palmar

the aspect of the forepaw on which the pads are located

plantar

the aspect of the hindpaw on which the pads are located

cranial

toward or relatively near the head

medial

toward or relatively near the median plane

rostral

toward or relatively near the nose

caudal

toward or relatively near the tail

dorsal

towards or relatively near the back and corresponding surface of the head, neck, or tail

ventral

towards or relatively near the belly