The document discusses the six levels of structural organization in the human body: chemical, cellular, tissue, organ, organ system, and organism levels. At each level, more complex structures and functions emerge, starting from atoms forming molecules to cells making up tissues, which in turn form organs and organ systems. The organism level represents the whole living individual, where all components work together to maintain life.

1. By – Devendra Kumar Rawat
Assistant Professor
M.Pharm (Pharmacology)
B.M.S. College Of Pharmacy, Nasratpur, Tiloi, Distt.
Amethi
(Chapter – 1)
(Lecture – 2)

2. Levels of Structural Organization
The human body contains multiple levels of structural
organization :
1. Chemical level
2. Cellular level
3. Tissue level
4. Organ level
5. Organ system level
6. Organism level

5. 1. Chemical level
 The simplest level of structural organization of living
organisms is the chemical level.
 Atoms of various elements combine to form larger, more
complex structures termed Molecules.
 Organic molecules aggregate to form cellular organelles.
 Certain atoms such as Carbon, hydrogen, oxygen,
nitrogen, phosphorus, calcium, and sulfur, are essential for
maintaining life.
 Two familiar molecules found in our body are DNA and
Glucose.

6. 2. Cellular level
 The cellular level is made up of the smallest unit of living
matter, i.e. cell.
 Molecules combine to form cells, the basic structural and
functional unit of an organism.
 Cells are building blocks of the human body.

7. 3. Tissue level
 Cells of similar structure and function congregate to form
tissues.
 There are 4 principle types of tissues in the human
organism :
i. Epithelial tissue
ii. Connective tissue
iii. Muscular tissue
iv. Nervous tissue

8. 4. Organ level
 Two or more types of tissues are combine within the same
structure to form an organ.
 Organs have specific functions and usually have
recognizable shapes.
 Examples of organs are the stomach, skin, bones, heart,
liver, lungs, and brain.
 Complex functions begin to emerge at this level.
 Most organs contain all 4 of the principle types of tissues.

9. 5. Organ system level
 Individual organs that function cooperatively to
accomplish a common purpose are grouped together into
organ system.
 An example of the system level is the Digestive system,
which breaks down and absorbs food.
 Digestive system includes many organs such as mouth,
salivary glands, pharynx, oesophagus, stomach, intestine,
liver, gallbladder, and pancreas.
 Other organ system of the body are integumantary system,
skeletal system, nervous system, muscular system,
endocrine system, respiratory system, lymphatic system,
urinary system and reproductive system.

11. 6. Organism level
 An organism is any living individual, like microorganism
or human body. All the parts of the human body
functioning together constitute the whole organism.
 The organism level is the highest level of the organization.
It is the sum total of all structural levels working together.
 In short, it is the human being or organism as a whole.
 An organism is a living being that has a cellular structure
and that can independently perform all physiologic
functions necessary for life.
 In multi-cellular organisms, including humans, all cells,
tissues, organs, and organ systems of the body work
together to maintain the life and health of the organism.