* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
LESSON 5: BODY SYSTEMS A. Cell Differentiation A unicellular organism contains organelles that perform all required life functions in one cell. Multicellular organisms are much more complex and are composed of many different types of cells. A specialized cell has a unique structure that allows it to perform a specific function. Ex. the structure and function of a red blood cell is much different from that of a fat cell It is more efficient to have “specialist” cells that perform one function very well instead of every cell having to perform every function. Cell differentiation is the process of creating specialized cells, and is controlled by the DNA. All multicellular organisms begin as a single cell. In humans this cell is called a zygote. The zygote goes through a series of cell divisions (mitosis) to form a group of identical cells called an embryo. At this point, the embryonic cells are called stem cells because they have the potential to become any type of cell! As the embryo develops, the cells begin to show differences in their shape, contents, and function. Embryonic stem cells – unspecialized cells that can differentiate into any cell type (this makes them valuable for medical research and treatment) Adult stem cells – exist in some tissues, but can only produce specific cell types (ex. bone marrow stem cells can form red blood cells, white blood cells, and platelets) B. Levels of Organization Multicellular organisms, such as plants and animals, are made of many types of specialized cells that are organized in a way that allows them to work together to keep that organism alive. There are levels of organization in each multicellular organism that form a hierarchy (levels of organization of increasing complexity). least complex most complex Cell – the smallest functional unit of life (ex. muscle cell) Tissue – a group of similar cells that work together to perform a simple function Organ – a structure composed of different tissues that work together to perform a more complex function Organ system – a group of organs that work together to perform a major body function Organism – a collection of organ systems that work together to keep the organism alive C. Tissues Animals have 4 main types of tissue. Each tissue contains many types of specialized cells, and each tissue is found in most organ systems. 1) Epithelial Tissue Description: thin sheets of tightly packed cells that cover body surfaces and lines internal organs and body cavities Ex. skin, lining of the digestive system Function: protection These cells divide very quickly to replace lost/damaged cells 2) Connective Tissue Description: various types of cells and held together by a liquid or solid substance called a “matrix Ex. bone, blood, tendons, cartilage Function: supports protects, connects the body’s organs, insulation These cells divide slowly so the body structure remains strong (exception: blood cells). 3) Muscle Tissue Description: bundles of long cells (“muscle fibres”) that can shorten (“contract”) Ex. biceps, hamstring, heart Function: movement, organ function These cells divide very slowly...cardiac and skeletal muscle cells do not divide at all! 4) Nervous Tissue Description: long, thin, branching cells that can conduct electrical impulses Ex. brain tissue, spinal cord, nerves Function: sends signals from one part of the body to another These cells never divide. Damage done to any nervous tissue cannot be repaired. D. Animal Organ Systems All animals accomplish the same basic life functions regardless of their appearance, behaviour, or habitat. The task of organ systems is to perform these life functions. There are 11 major organ systems in the human body. Use the provided handout to fill in the chart below. Organ System Function Organs that are part of this system E. Interactions of Body Systems Organ systems interact to keep the organism functioning. All organ systems interact with at least one other organ system. In complex animals, the circulatory system acts as a transport system that connects all other systems. a) The respiratory and circulatory systems work together to distribute oxygen to all body cells and to remove carbon dioxide. The respiratory system brings oxygen gas into the lungs where it diffuses into the blood in the circulatory system. The circulatory system transports the oxygen to all tissues, where it diffuses into the cells. Oxygen gas is used in the process of cellular respiration to produce energy. Carbon dioxide is a waste product of cellular respiration and it diffuses from the cells into the blood. The circulatory system transports the carbon dioxide back to the lungs, where it diffuses from the blood back into the lung airways to be breathed out. b) The digestive and circulatory systems work together to distribute nutrients to all body cells and to remove waste products. The digestive system breaks down food into small molecules that diffuse through the walls of the digestive tract and into the blood. The circulatory system then transports these nutrients to all tissues in the organism, where they diffuse into the cells. Any waste products diffuse out of the cells and into the blood and are transported to the urinary system. The waste products are filtered out of the blood and end up being expelled from the body in urine. c) The lymphatic and circulatory systems work together to protect the body from foreign invaders (ex. viruses and bacteria). The lymphatic system filters out any disease-causing organisms that get into the body’s tissues. The lymphatic system also produces white blood cells and antibodies which are released into the bloodstream to be transported all over the body to fight invading germs.