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LEC.2 حسام العزاوي. د Body Organization All organisms are built from simple to more complex levels Chemicals form the materials that make up cells, which are the body’s structural and functional units. Groups of cells working together make up tissues, which in turn make up the organs, which have specialized functions. Organs become components of the various systems, which together comprise the whole organism. The Cell The cell is the basic unit of living organisms. Cells accomplish all the activities and produce all the components of the body. They carry out metabolism, the sum of all the body’s physical and chemical activities. They provide the energy for metabolic reactions in the form of the chemical ATP (adenosine triphosphate), commonly described asthe energy compound of the cell. The study of cells is cytology (sī-TOL-ōjē), based on the root cyt/o, meaning “cell.” has career information in the fi eld of cytology. Levels of organization. The organ shown is the stomach, which is part of the digestive system. Tissues Cells are organized into four basic types of tissues that perform specifi c functions: ■ Epithelial (ep-i-THĒ-lē-al) tissue covers and protects body structures and lines organs, vessels, and cavities ■ Connective tissue supports and binds body structures ■ Muscle tissue (root: my/o) contracts to produce movement. There are three types of muscle tissue: ■ Skeletal muscle moves the skeleton. ■ Cardiac muscle forms the heart. ■ Smooth or visceral muscle forms the walls of the abdominal organs Generalized animal cell, sectional view. The main organelles are shown. Cell Structures NAMe plasma membrane (PLAZ-ma) Microvilli (mī-krō-VIL-ī) Nucleus (NŪ-klē-us) cytoplasm (SĪ-tō-plazm) DESCRIPTION FUNCTION outer layer of the cell encloses the cell contents short extensions of the cell membrane absorb materials into the cell large, dark-staining organelle near the center of the cell contains the chromosomes, hereditary units colloidal suspension that fills the cell site of many cellular activities. endoplasmic reticulum network of membranes (en-dō-PLAZ-mik re-TIK-ū-lum) within the cytoplasm. ribosomes (RĪ-bō-sōmz) small bodies free in the cytoplasm or attached to the ER Mitochondria (mī-tō-KON-drē-a) large organelles with folded membranes inside Golgi apparatus (GŌL-jē) layers of membranes lysosomes (LĪ-sō-sōmz) small sacs of digestive enzymes peroxisomes (per-OKS-i-sōmz) surface projections membrane-enclosed organelles containing enzymes structures that extend from the cell cilia (SIL-ē-a) flagellum rough ER sorts proteins Smooth ER is involved lipid synthesis. manufacture proteins convert energy from nutrients into ATP makes compounds containing proteins, sorts and prepares these compounds for transport to other parts of the cell or out of the cell digest substances within the cell short, hair-like projections from the cell long, whip-like extension from the cell break down harmful substances move the cell or the fluids around the cell move the fluids around the cell moves the cel (fla-JEL-um) Terminology Key Terms ATP The energy compound of the cell that stores energy needed for cell activities; adenosine triphosphate (a-DEN-ō-sēn trī-FOS-fāt) carbohydrate The category of organic compounds that includes sugars and starches kar-bō-HĪ-drāt cell The basic structural and functional unit of the living organism, a microscopic unit that sel combines with other cells to form tissues (root: cyt/o) chromosome A thread-like body in a cell’s nucleus that contains genetic information KRŌ-mō-sōm cytology Study of cells sī-TOL-ō-jē cytoplasm The fluid that fills a cell and holds the organelles SĪ-tō-plazm DNA The genetic compound of the cell, makes up the genes; deoxyribonucleic (dē-ok- sē-rī-bōnū- KLĒ-ik) acid enzyme An organic substance that speeds the rate of a metabolic reaction EN-zīm gene A hereditary unit composed of DNA and combined with other genes to form jēn the chromosomes glucose A simple sugar that circulates in the blood, the main energy source for GLŪ-kōs metabolism(roots: gluc/o, glyc/o) Histology Study of tissues his-TOL-ō-jē homeostasis A steady state, a condition of internal stability and constancy hō-mē-ō-STĀ-sis lipid A category of organic compounds that includes fats (root: lip/o) LIP-id metabolism The sum of all the physical and chemical reactions that occur within an me-TA-bō-lizm organism mitosis Cell division mī-TŌ-sis nucleus The cell’s control center; directs all cellular activities NŪ-klē-us organ A part of the body with a specific function, a component of a body system OR-gan organelle A specialized structure in the cytoplasm of a cell OR-ga-nel RNA An organic compound involved in the manufacture of proteins within cells; ribonucleic(rī-bō-nū-KLĒ-ik) acid tissue A group of cells that acts together for a specific purpose (roots: hist/o, histi/o) TISH-ū