UnitDne: Intro to the Human Body  
Humn Body Structure  
7033ag  
Human beings are arguably the most caplexorganisms on this planel  Imagine billions of microscopic parts, each with owridentity, working together i  an organize-d manner for the benefit of the total eing.The human body is a singl  structure but it is made up of billions of smaller suctues of four major kinds:  Cells The basic unil of life  
Cells have long been recognized as the simlest nits of living., matter that car  maintain life and reproduce themselves. The hmanbody, which is made up d  numerous cells, begins as a single, newly fertilizd cel  groups of anilot clls working to gether  Tissues  S  Isues are somewhat more_complex units than cells. By definitin, atssue is an organization of t  greamany similar cells with vairying amounts and kinds of nonlivin, intecellular substance betweer  i~J them  
Orgas  
2  Vi  `  S  d  Ggans are more complex unils than tssues An organ is an orgnizabn of several different kindi  of tisues SO arranged that together they can perform a special fundon. 4or example, the stomach  an oganization of muscle, connective, epithelial, and nervous tissus. Mscle and connective tissuet  S  form ts wall, epithelial and conr nective tissues form its lining and nrVou tissue extends throughou.  both  wall and its lining  J19  Systms  2  JA  
Sstems are the most cornplex_of the component units of te hunan body. A systemn is_ar  orgaization of varying numbe rs and kinds of organs so arrange thattogether they can perfor  compex functions for the body. Ten major systems compose the hunan bdy:  Skeletal  2  S  1  2 Muscular  3 Nervous (peall  a! 4 Endocrine  5 Cardiovascular  J 6 Lymphatic  7 Respiratory  AI8 Digestive  9 Urinary  (J ,. Reproductive