Introduction to Anatomy & Physiology

Definitions and Scope

Anatomy and physiology are two closely related branches of biology that study the human body. Anatomy focuses on the structure of body parts and their relationships to one another, while physiology concerns the function of the body, explaining how body parts work and carry out life-sustaining activities.

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

• Physiology: The study of the function of body parts and how they work together.

Levels of Structural Organization

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

• Chemical level: Atoms and molecules (e.g., water, proteins).

• Cellular level: Cells, the basic units of life.

• Tissue level: Groups of similar cells performing a common function (e.g., blood, muscle, nerves).

• Organ level: Structures composed of two or more tissue types (e.g., heart, liver).

• Organ system level: Groups of organs working together (e.g., digestive system).

• Organismal level: The complete living organism.

Essential Life Functions

Maintaining Boundaries

Separation between internal and external environments is vital for homeostasis.

• Plasma membranes separate cells.

• Skin separates the organism from the environment.

Movement

• Muscular system allows movement of body parts via skeletal muscles.

• Movement of substances via cardiac muscle (blood) and smooth muscle (digestion, urination).

Responsiveness

• Ability to sense and respond to stimuli.

• Withdrawal reflex prevents injury.

• Control of breathing rate in response to activity.

Digestion

• Breakdown of ingested foodstuffs.

• Absorption of simple molecules into blood.

Metabolism

• All chemical reactions occurring in body cells.

• Includes catabolism (breakdown of molecules) and anabolism (synthesis of molecules).

Reproduction

• Cellular level: division of cells for growth or repair.

• Organismal level: production of offspring.

Growth

• Increase in size of a body part or the organism as a whole.

Organ Systems of the Human Body

Humans are multicellular; organ systems are designed to service the cells and maintain life. There are 11 major organ systems:

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

2. Skeletal System: Protects and supports body organs, provides a framework for muscle movement, and produces blood cells.

3. Muscular System: Allows locomotion, maintains posture, and produces heat.

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

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

6. Cardiovascular System: Blood vessels transport blood carrying oxygen, carbon dioxide, nutrients, and wastes; heart pumps blood.

7. Lymphatic/Immune System: Returns leaked fluid to blood, disposes of debris, houses lymphocytes, and mounts immune responses.

8. Respiratory System: Keeps blood supplied with oxygen and removes carbon dioxide; gas exchange occurs in lung air sacs.

9. Digestive System: Breaks down food and absorbs nutrients; eliminates indigestible foodstuffs.

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

11. Reproductive System: Produces offspring; testes produce sperm and male hormones, ovaries produce eggs and female hormones, and mammary glands nourish newborns.

Survival Needs

Humans require several factors for survival, each in appropriate amounts:

• Nutrients (food)

• Oxygen

• Water

• Normal body temperature

• Appropriate atmospheric pressure

Homeostasis

Definition and Mechanisms

Homeostasis is the maintenance of a stable internal environment despite external changes. It is a dynamic process involving self-regulating mechanisms.

• Homeostatic control mechanisms involve at least three components: receptor, control center, and effector.

Feedback Mechanisms

• Negative feedback: Output shuts off the original effect of the stimulus or reduces its intensity (e.g., body temperature regulation).

• Positive feedback: Response enhances the original stimulus, accelerating the response (e.g., blood clotting, labor contractions).

Basic Chemistry for Anatomy & Physiology

States of Matter

Matter exists in three states:

• Solid: Definite shape and volume.

• Liquid: Definite volume, changeable shape.

• Gas: Changeable shape and volume.

Energy

• Energy is the capacity to do work or put matter into motion.

• Energy does not have mass or take up space.

• The greater the work done, the more energy is used.

Kinetic vs. Potential Energy

• Kinetic energy: Energy in action.

• Potential energy: Stored (inactive) energy.

Energy can be transformed from potential to kinetic energy.

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

Energy 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

• All matter is composed of elements.

• Four elements make up 96% of the body: carbon (C), oxygen (O), hydrogen (H), and nitrogen (N).

• The periodic table lists all known elements.

Atoms

• Elements are made up of atoms, the unique building blocks for each element.

• Atoms consist of three subatomic particles:

  • Protons: Positively charged, found in the nucleus.

  • Neutrons: No charge, found in the nucleus.

  • Electrons: Negatively charged, orbit around the nucleus.

• Number of protons is balanced by number of electrons, making atoms electrically neutral.

Atomic Number and Mass Number

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

• Mass number: Total number of protons and neutrons; written as superscript to the left of the atomic symbol.

Isotopes

• Isotopes are structural variations of the same element; they have the same atomic number but different mass numbers.

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.

Most atoms chemically combine to form molecules and compounds, which are essential for biological processes.

*Additional info: Some content was inferred and expanded for clarity and completeness, such as the names of the four major elements, the definition of feedback mechanisms, and the list of survival needs.*