1.1 Overview of Anatomy and Physiology

Anatomy and physiology are two complementary disciplines that together explain how the human body is built and how it functions. Anatomy focuses on structure, while physiology addresses how those structures work. Understanding both is essential because form and function are deeply linked: the shape of a body part almost always reflects what it does. This unit lays the groundwork for everything else in the course.

Introduction to Anatomy and Physiology

Anatomy vs physiology comparison

Anatomy is the study of the physical structure and organization of living things. It examines the shape, size, and location of body parts and how they relate to one another. Anatomists use techniques like dissection, imaging (X-ray, MRI, CT scans), and microscopy to study the body.

Physiology is the study of the functions and processes carried out by living things. It examines how the body and its parts work, including chemical and physical processes. Physiologists design experiments to measure body functions like blood pressure, heart rate, and respiratory rate.

A major theme in physiology is homeostasis, the body's ability to regulate its internal conditions (temperature, blood pH, glucose levels) within a narrow range. The body achieves this through feedback loops, which you'll study in detail later in this unit.

Structure-function relationship in the human body

One of the most important principles in this course is that structure determines function. The physical design of a body part is directly tied to the job it performs. Here are some core examples:

• Bones are hard and dense, providing support and protection for internal organs. Long bones like the femur are hollow on the inside, which reduces weight while maintaining the strength needed for movement.
• Muscles are composed of elongated cells (muscle fibers) arranged in parallel bundles, which allows them to contract and generate force. Muscles attach to bones via tendons; for example, the biceps muscle attaches to the radius bone to flex the forearm.
• The heart has four chambers that separate oxygen-rich and oxygen-poor blood, allowing efficient pumping to the lungs and the rest of the body. Valves (like the tricuspid and mitral valves) ensure blood flows in one direction and doesn't leak backward.
• The lungs have a spongy, elastic structure with a massive surface area. Airways branch repeatedly into smaller bronchi and bronchioles, ending in tiny air sacs called alveoli, where gas exchange actually occurs.
• The kidneys contain roughly one million tiny filtering units called nephrons. Each nephron has specialized cells (podocytes) that selectively filter substances from the blood based on size and charge, regulating fluid and electrolyte balance.

Specializations of anatomy and physiology

Both anatomy and physiology have subfields that focus on specific aspects of the body. You don't need to memorize every subfield, but understanding the major ones helps you see how the disciplines are organized.

Anatomy specializations:

• Gross (macroscopic) anatomy examines structures visible to the naked eye, such as organs, muscles, and bones. This is what you study during cadaver dissection.
• Microscopic anatomy (histology) examines structures at the cellular and tissue level using microscopes. You'll encounter the four basic tissue types here: epithelial, connective, muscle, and nervous tissue.
• Developmental anatomy (embryology) studies how an organism forms and develops from conception to birth. This field helps explain congenital disorders like spina bifida and how adult structures originate.

Physiology specializations:

• Neurophysiology focuses on the nervous system, including how the brain, spinal cord, and nerves control body functions like reflexes, sensory processing, and motor control.
• Endocrinology studies the endocrine system and hormones. Endocrine glands (pituitary, thyroid, adrenal) release hormones (insulin, estrogen, testosterone) that regulate growth, metabolism, and reproduction.
• Cardiovascular physiology studies the heart and blood vessels, including how the body maintains blood pressure, delivers oxygen, and transports nutrients. This covers topics like the cardiac conduction system and how blood vessels dilate or constrict.

Fundamental concepts in anatomy and physiology

Several foundational ideas run through the entire course:

Cell theory states that all living things are composed of cells, cells are the basic unit of life, and all cells arise from pre-existing cells. This is the starting point for understanding every structure and process in the body.

Levels of structural organization describe how the body is built from simple to complex:

1. Cells are the smallest living units
2. Tissues are groups of similar cells performing a common function
3. Organs are structures made of two or more tissue types working together
4. Organ systems are groups of organs that cooperate to carry out broad functions
5. The organism is the highest level, representing all systems functioning together

Organ systems don't work in isolation. The circulatory, respiratory, and digestive systems (among others) constantly interact to keep the body functioning. You'll see this interdependence throughout the course.

Metabolism refers to all the chemical reactions occurring in the body. This includes breaking down food (catabolism), building new molecules (anabolism), producing energy, and eliminating waste.

The scientific method is the framework used to study anatomy and physiology. It involves making observations, forming hypotheses, conducting controlled experiments, and drawing conclusions from the data.