The Human Body: An Orientation

Directional Terms

Directional terms are used to describe the locations of structures or regions of the body relative to other structures.

• Superior: Above or toward the head.

• Inferior: Below or toward the feet.

• Anterior: Toward the front of the body.

• Posterior: Toward the back of the body.

• Medial: Toward the midline of the body.

• Lateral: Away from the midline of the body.

• Proximal: Closer to the point of attachment or origin.

• Distal: Farther from the point of attachment or origin.

Body Planes

Body planes are imaginary lines used to divide the body into sections for anatomical study.

• Sagittal Plane: Divides the body into left and right portions.

• Frontal (Coronal) Plane: Divides the body into anterior (front) and posterior (back) portions.

• Transverse (Horizontal) Plane: Divides the body into superior (top) and inferior (bottom) portions.

Body Cavities

The body contains several cavities that house and protect vital organs.

• Dorsal Cavity: Contains the brain and spinal cord.

• Ventral Cavity: Contains the heart, lungs, stomach, and intestines.

• Cranial Cavity: Subdivision of the dorsal cavity; contains the brain.

Homeostasis

Homeostasis is the maintenance of a stable internal environment in the body.

• Negative Feedback: A mechanism that reverses a change to maintain balance (e.g., regulation of body temperature).

• Positive Feedback: A mechanism that increases or amplifies a change (e.g., blood clotting, labor contractions).

Basic Chemistry

Subatomic Particles

Atoms are composed of three main subatomic particles:

• Proton: Positively charged particle found in the nucleus.

• Neutron: Neutrally charged particle found in the nucleus.

• Electron: Negatively charged particle found in orbitals around the nucleus.

Chemical Bonds

Chemical bonds are forces that hold atoms together in molecules and compounds.

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating ions (e.g., NaCl).

• Covalent Bonds: Formed when atoms share electrons (e.g., H2O).

• Hydrogen Bonds: Weak attractions between polar molecules, important in the structure of water and DNA.

pH Scale

The pH scale measures the concentration of hydrogen ions in a solution, indicating its acidity or alkalinity.

• Acid: pH below 7

• Neutral: pH of 7

• Base (Alkaline): pH above 7

• Normal Blood pH: 7.35–7.45

Organic Compounds

Organic compounds are molecules that contain carbon and are essential for life.

• Carbohydrates: Provide quick energy (e.g., glucose).

• Lipids: Fats and oils used for long-term energy storage and cell membranes.

• Proteins: Serve as enzymes, structural components, and signaling molecules.

• Nucleic Acids: DNA and RNA, which store and transmit genetic information.

ATP (Adenosine Triphosphate)

ATP is the primary energy carrier in cells.

• ATP stores energy in its high-energy phosphate bonds.

• When energy is needed, ATP is converted to ADP (adenosine diphosphate) and a phosphate group, releasing energy.

Equation:

Important Prefixes & Suffixes

Understanding common prefixes and suffixes helps in interpreting medical and scientific terminology.

• hyper-: Excessive or above normal (e.g., hypertension = high blood pressure)

• hypo-: Low or below normal (e.g., hypoglycemia = low blood sugar)

• -itis: Inflammation (e.g., arthritis = inflammation of joints)

• -algia: Pain (e.g., neuralgia = nerve pain)

• -ectomy: Removal (e.g., appendectomy = removal of the appendix)

• -cyte: Cell (e.g., erythrocyte = red blood cell)

Practice Questions and Answers

Additional info: The cranial cavity is a subdivision of the dorsal cavity and specifically houses the brain. The practice questions reinforce key concepts from the study guide.