Anatomy and Physiology
Organization of the Body
Anatomy is structure; physiology is function. The body is organized from cells to tissues to organs to organ systems to the whole organism, and each level depends on the others. Homeostasis - maintaining a stable internal environment - is the central theme. Most control is by negative feedback (a change triggers a response that reverses it), while positive feedback amplifies a change and is rare (labor contractions, blood clotting).
Concepts to Master
- Anatomical position: standing, facing forward, arms at sides, palms forward. All directional terms assume it.
- Directional terms: superior/inferior, anterior/posterior, medial/lateral, proximal/distal, superficial/deep.
- Planes: sagittal (left/right), coronal or frontal (front/back), transverse (upper/lower).
- Cavities: dorsal (cranial, spinal) and ventral (thoracic, abdominopelvic), separated by the diaphragm.
- Organ systems: integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, reproductive - know each system’s primary organs and function.
Traps
Exams test whether you confuse planes, especially sagittal versus coronal. Right and left are the patient’s right and left, not yours. The thoracic and abdominopelvic cavities are both ventral; the diaphragm is the boundary. Do not confuse negative and positive feedback. Also know that the heart sits in the mediastinum, not the abdominal cavity.
Worked Example
A question asks which plane divides the body into equal right and left halves. The answer is the midsagittal plane; a coronal plane divides front from back, and a transverse plane divides top from bottom. Rule of thumb: when a question mentions direction, mentally place the patient in anatomical position before choosing.