1、Cells,Tissues,and OrgansHaijian XIA（夏海坚）（夏海坚）,Associate Professor,Ph.D.,M.D.Department of Neurosurgery The First Affiliated Hospital of Chongqing Medical UThe Cell The body can be studied from its simplest to its most complex level,beginning with the cell,the basic unit of living organisms.Cells car
2、ry out metabolism,the sum of all of the physical and chemical activities that occur in the body.Providing the energy for metabolic reactions is the chemical ATP(adenosine triphosphate),commonly described as the energy compound of the cell.The main categories of organic compounds of the cell are:Prot
3、eins,which include the enzymes,some hormones,and structural materials.Carbohydrates,which include sugars and starches.The main carbohydrate is the sugar glucose,which circulates in the blood to provide energy for the cells.Lipids,which include fats.Some hormones are derived from lipids,and adipose(f
4、at)tissue is designed to store lipids.Within the cytoplasm that fills the cell are subunits called organelles,each with a specific function.The main cell structures are named and described as below:The nucleus is the control region of the cell.It contains the chromosomes,which carry genetic informat
5、ion.Each human cell,except for the sex cells,contains 46 chromosomes.The chromosomes are composed of a complex organic substance,DNA(deoxyribonucleic acid),which is organized into separate units called genes.Genes control the formation of enzymes,the catalysts needed for metabolic reactions.To help
6、manufacture enzymes,the cells use a compound called RNA(ribonucleic acid),which is chemically related to DNA.When a body cell divides,by the process of mitosis,the chromosomes are doubled and then equally distributed to the two daughter cells,which is shown as below:Sex cells(egg and sperm)divide by
7、 another process(meiosis)that halves the chromosomes in preparation for fertilization.TissueCells are organized into four basic types of tissues that perform specific functions:Epithelial tissue covers andprotects body structures and lines organs,vessels,and cavities.Connective tissue supports and b
8、inds body structures.It contains fibers and other nonliving materialbetween the cells.Included are adipose(fat)tissue,cartilage,bone,and blood.Muscle tissue contracts to produce movement.There are three types of muscle tissue:Skeletal or voluntary muscle moves the skeleton.Cardiac muscle forms the h
9、eart.It functions without conscious control and is described as involuntary.Smooth,or visceral muscle forms the walls of the abdominal organs;it is also involuntary.Nervous tissue makes up the brain,spinal cord,and nerves.It coordinates and controls body responses by the transmission of electrical i
10、mpulses.The simplest tissues are membranes.Mucous membranes secrete mucus,a thick fluid that lubricates surfaces and protects underlying tissue.Serous membranes,which secrete a thin,watery fluid,line body cavities and cover organs.ecdbabadecOrgans and Organ SystemsTissues are arranged into organs,wh
11、ich serve specific functions.The organs,in turn,are grouped into systems.Bear in mind,however,that the body functions as a wholeno system is independent of the others.They work together to maintain the bodys state of internal stability,termed homeostasis.Organs of the digestive tractExercisesThank for your attention!
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