Introduction to Anatomy and Physiology

Definitions and Relationships

Anatomy is the study of the structure of body parts and their relationships to one another. Physiology is the study of the function of the body’s structural machinery. Understanding both is essential to appreciate how the human body works as an integrated whole.

• Structure and Function: The form of a body part is closely related to its function ("structure determines function").

• Example: The shape of the heart’s chambers allows it to pump blood efficiently.

Levels of Organization in the Human Body

The human body is organized into hierarchical levels, each building on the previous one.

• Chemical Level: Atoms and molecules

• Cellular Level: Cells and their organelles

• Tissue Level: Groups of similar cells

• Organ Level: Contains two or more types of tissues

• Organ System Level: Organs that work closely together

• Organismal Level: All organ systems combined to make the whole organism

Organ Systems of the Body

There are 11 major organ systems in the human body, each with specific organs and primary functions.

Homeostasis and Feedback Mechanisms

Homeostasis is the maintenance of a stable internal environment despite external changes. The body uses feedback mechanisms to maintain homeostasis.

• Stimulus: Produces change in variable

• Receptor: Detects change

• Input: Information sent to control center

• Output: Information sent to effector

• Response: Effector feeds back to reduce the effect of stimulus

• Negative Feedback: Reduces or shuts off the original stimulus (e.g., body temperature regulation)

• Positive Feedback: Enhances the original stimulus (e.g., blood clotting)

Anatomical Position and Directions

The anatomical position is a standard reference position used in anatomy: the body is erect, facing forward, arms at sides with palms facing forward.

• Directional Terms: Used to describe locations of structures (e.g., superior, inferior, anterior, posterior, medial, lateral, proximal, distal)

Body Regions and Cavities

• Surface Body Regions: Specific areas of the body surface (e.g., abdominal, thoracic, cervical)

• Major Body Cavities: Dorsal (cranial and vertebral) and ventral (thoracic and abdominopelvic) cavities

• Membranes: Serous membranes line body cavities and cover organs

Basic Chemistry for Anatomy and Physiology

Structure of the Atom

An atom consists of a nucleus (containing protons and neutrons) and electrons orbiting the nucleus.

• Proton: Positively charged particle

• Neutron: Neutral particle

• Electron: Negatively charged particle

Atomic Mass, Atomic Weight, Chemical Symbol, and Atomic Number

• Atomic Number (Z): Number of protons in the nucleus

• Atomic Mass: Sum of protons and neutrons

• Atomic Weight: Average mass of all isotopes of an element

• Chemical Symbol: One- or two-letter abbreviation for an element (e.g., H for hydrogen)

Isotopes, Cations, and Anions

• Isotope: Atoms of the same element with different numbers of neutrons

• Cation: Positively charged ion (lost electrons)

• Anion: Negatively charged ion (gained electrons)

Elements of the Human Body

The four main elements in the human body are:

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

Elements, Molecules, Compounds, and Mixtures

• Element: Pure substance of one type of atom

• Molecule: Two or more atoms bonded together (e.g., )

• Compound: Molecule containing two or more different elements (e.g., )

• Mixture: Physical combination of substances (not chemically bonded)

Energy Forms

• Chemical Energy: Stored in bonds of chemical substances

• Electrical Energy: Movement of charged particles

• Mechanical Energy: Directly involved in moving matter

• Radiant Energy: Energy that travels in waves (e.g., light)

Chemical Bonds

• Ionic Bonds: Transfer of electrons between atoms

• Covalent Bonds: Sharing of electrons between atoms

• Hydrogen Bonds: Weak attraction between a hydrogen atom and another electronegative atom

Chemical Reactions

• Synthesis Reaction: Atoms or molecules combine ()

• Decomposition Reaction: Molecule is broken down ()

• Exchange Reaction: Bonds are both made and broken ()

Solutions, Solutes, and Solvents

• Solution: Homogeneous mixture of two or more substances

• Solvent: Substance present in greatest amount (usually water in the body)

• Solute: Substance dissolved in the solvent

Biomolecules in the Human Body

Major Classes of Biomolecules

• Carbohydrates: Provide energy; include sugars and starches

• Lipids: Fats and oils; energy storage and cell membrane structure

• Proteins: Structural, enzymatic, and regulatory functions

• Nucleic Acids: DNA and RNA; store and transmit genetic information

Protein Structure and Binding

Proteins have four levels of structure:

• Primary: Sequence of amino acids

• Secondary: Alpha helices and beta sheets formed by hydrogen bonding

• Tertiary: 3D folding due to side chain interactions

• Quaternary: Association of multiple polypeptide chains

• Protein Binding Sites: Specific regions where molecules bind, critical for protein function (e.g., enzyme active sites)