Anatomy & Physiology: Foundations, Chemistry, and Biological Organization

Anatomy and Physiology: Introduction

Definitions and Scope

Anatomy and physiology are foundational sciences in understanding the human body. Anatomy focuses on the structure of body parts and their relationships, while physiology examines the function of these parts and how they work together to sustain life.

• Anatomy: Study of the structure of body parts and their relationships.

• Physiology: Study of the function of body parts and how they carry out life-sustaining activities.

Levels of Structural Organization

The human body is organized into hierarchical levels, each with increasing complexity.

• Chemical level: Atoms, molecules, and organelles.

• Cellular level: Single cell; basic structural and functional unit of life.

• Tissue level: Groups of similar cells working together for a specific function (e.g., blood, muscle, nerves).

• 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.

Necessary Life Functions

Maintenance of Life

To sustain life, organisms must perform several essential functions:

• Maintaining boundaries: Separation between internal and external environments (e.g., plasma membranes, skin).

• Movement: Muscular system allows movement, manipulation of environment, and locomotion.

• Responsiveness: Ability to sense and respond to stimuli (e.g., withdrawal reflex, control of breathing rate).

• Digestion: Breakdown of ingested foodstuffs, absorption of nutrients into blood.

• Metabolism: All chemical reactions in body cells, including catabolism (breakdown) and anabolism (synthesis).

• Excretion: Removal of wastes from metabolism and digestion (e.g., urea, carbon dioxide, feces).

• Reproduction: Cellular division for growth or repair; production of offspring at organismal level.

• Growth: Increase in size of body part or organism.

Organ Systems Overview

Humans are multicellular; organ systems are designed to serve the cells and maintain survival needs. There are 11 organ systems:

1. Integumentary System: Forms external body covering, protects deeper tissues, synthesizes vitamin D, houses receptors and glands.

2. Skeletal System: Protects and supports organs, provides framework for muscles, forms blood cells, stores minerals.

3. Muscular System: Allows manipulation, locomotion, facial expression, maintains posture, produces heat.

4. Nervous System: Fast-acting control system, responds to internal/external changes by activating muscles/glands.

5. Endocrine System: Glands secrete hormones regulating growth, reproduction, metabolism.

6. Cardiovascular System: Blood vessels transport blood, heart pumps blood.

7. Lymphatic System/Immunity: Picks up fluid leaked from blood, disposes debris, houses white blood cells, mounts immune response.

8. Respiratory System: Keeps blood supplied with oxygen, removes carbon dioxide.

9. Digestive System: Breaks down food, absorbs nutrients, eliminates indigestible foodstuffs as feces.

10. Urinary System: Eliminates nitrogenous wastes, regulates water, electrolytes, acid-base balance.

11. Reproductive System: Produces offspring; male and female organs produce gametes and support fertilization/development.

Survival Needs

For survival, humans require:

• Nutrients

• Oxygen

• Water

• Normal body temperature

• Appropriate atmospheric pressure

Homeostasis

Definition and Mechanisms

Homeostasis is the condition of maintaining the body's internal environment in a relatively constant state (e.g., blood pressure, glucose levels).

• Homeostatic imbalance: Anything that disturbs or alters the balance of the internal environment.

• Homeostatic control mechanisms: Self-regulating processes involving receptor, control center, and effector.

Feedback Mechanisms

• Negative feedback: Output shuts off the original effect of the stimulus or reduces its intensity. Example: regulation of body temperature.

• Positive feedback: Output enhances the original stimulus so that the response is accelerated. Example: blood clotting.

Basic Chemistry

Matter

Matter is anything that has mass or occupies space. It can be seen, smelled, or felt. Weight is mass plus the effects of gravity.

• States of matter: Solid (definite shape/volume), liquid (changeable shape/definite volume), gas (changeable shape/volume).

Energy

Energy is the capacity to do work or put matter into motion. It does not have mass or take up space.

• Kinetic energy: Energy in action.

• Potential energy: Stored (inactive) energy.

Energy can be transformed from potential to kinetic and vice versa.

Forms of Energy

• Chemical energy: Stored in bonds of chemical substances.

• Electrical energy: Results from movement of charged particles.

• Mechanical energy: Directly involved in moving matter.

• Radiant energy: Travels in waves (e.g., heat, visible light, ultraviolet light, X-rays).

Energy Form Conversions

• Energy may be converted from one form to another (e.g., electrical to light energy).

• Energy conversion is inefficient; some energy is "lost" as heat.

Atoms and Elements

Elements

Elements are substances that cannot be broken down into simpler substances by ordinary chemical methods.

• Four elements make up 96% of the body: Oxygen (65%), Carbon (18%), Hydrogen (10%), Nitrogen (3%).

• Periodic table lists all known elements.

Atoms

Atoms are the smallest particles of an element with properties of that element. Each element has a unique atomic symbol (e.g., O for oxygen, C for carbon).

• Protons: Positive charge (+), 1 amu.

• Neutrons: No charge, 1 amu.

• Electrons: Negative charge (-), virtually no weight.

Number of protons equals number of electrons in a neutral atom. Protons and neutrons are in the nucleus; electrons orbit the nucleus.

Atomic Number and Mass Number

• Atomic number: Number of protons in nucleus; written as subscript to left of atomic symbol (e.g., 1H).

• Mass number: Total number of protons and neutrons; written as superscript to left of atomic symbol (e.g., 2H).

Isotopes

Isotopes are structural variations of the same element, differing in number of neutrons.

Combining Matter

Molecules and Compounds

• Molecule: General term for two or more atoms bonded together.

• Compound: Specific molecule with two or more different kinds of atoms bonded together (e.g., C6H12O6).

Mixtures

Most matter exists as mixtures: two or more components physically intermixed.

• Solutions: Homogeneous mixtures; particles evenly distributed. Solvent: Substance present in greatest amount (usually water). Solute: Substance dissolved in solvent (e.g., glucose in blood plasma).

• Colloids: Heterogeneous mixtures; particles not evenly distributed, may appear cloudy or milky.

• Suspensions: Heterogeneous mixtures with large, visible solutes that settle out (e.g., sand and water, blood).

Chemical Bonds

Types of Chemical Bonds

• Ionic bonds: Formed by transfer of electrons between atoms, resulting in ions (cations and anions).

• Covalent bonds: Formed by sharing of two or more valence shell electrons between atoms. - Single, double, or triple bonds depending on number of shared electrons.

• Polar covalent bonds: Unequal sharing of electrons, resulting in electrically polar molecules (e.g., H2O).

• Nonpolar covalent bonds: Equal sharing of electrons (e.g., CO2).

• Hydrogen bonds: Attractive force between electropositive hydrogen and an electronegative atom of another molecule.

Electron Shells and the Octet Rule

• Electrons occupy areas around nucleus called electron shells (energy levels).

• Shell 1 holds 2 electrons; shell 2 holds 8 electrons; shell 3 holds 18 electrons.

• Atoms desire 8 electrons in their valence shell (octet rule).

• Atoms will gain, lose, or share electrons to achieve stability.

Additional info:

• Examples of feedback mechanisms: Negative feedback (body temperature regulation), Positive feedback (labor contractions).

• Energy conversions in the body are never 100% efficient; some energy is always lost as heat.