Anatomy & Physiology

Anatomy & Physiology Study Guide

Chapter 2: General Organization of the Body

2.1 Hierarchy of Organization The human body has a hierarchy of organization. The organization at each level determines the structural characteristics of that level and the functions of higher levels. These levels of organization range from the molecule (the lowest level) to the cell (the smallest living unit) to the organism (the highest level). The Chemical (or Molecular) Level Atoms combine to form molecules with complex shapes. The form of the molecule determines its function. A molecule’s unique three-dimensional shape and atomic components dictate its functional properties. The Cellular Level Molecules interact to form various types of organelles. These “little organs” each have specific functions within cells , the smallest living units in the body. The Tissue Level A group of cells working together to perform one or more specific functions form tissue . Cardiac muscle cells (cardium, heart) interact with other cells and extracellular materials to formmyocardial tissue (myo-, muscle). The Organ Level Organs consist of two or more tissues working in combination. They perform several functions depending on their make-up. For example, layers of cardiac muscle tissue join with connective tissue to form the walls of the heart that will contract to pump blood. The Organ System Level Organs interact in organ systems. The heart contracts to pump blood through blood vessels to supply oxygen and nutrients to the body. The heart, blood, and blood vessels form the cardiovascular system, one of the eleven organ systems in the body. The Organism Level An organism is the highest level of organization. The human body has eleven organ systems that must work together to maintain the life and health of the organism. If the components of a system break down or are disrupted, it can affect the whole system or organism. For example, if heart tissue dies from a myocardial infarction (a heart attack) and the damage is extensive, the heart cannot pump blood effectively. Without the heart pumping blood, oxygen and nutrients cannot be distributed, even to cardiac tissue. Soon, the cardiac muscle tissue begins to break down as individual muscle cells die from oxygen and nutrient starvation. Even less blood is pumped, and other tissues and organs are affected and damaged due to lack of oxygen and

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