Before you begin to research the various structures and also functions of the human being body related to nutrition, the is helpful to consider the an easy architecture that the body; that is, how its smallest components are assembled right into larger structures. That is practically to think about the frameworks of the body in terms of fundamental levels of company that rise in complexity: atoms, molecules, cells, tissues, organs, organ systems, and organisms. Higher levels of company are developed from lower levels. Therefore, atoms combine to type molecules, molecules integrate to type cells, cells combine to kind tissues, tissues integrate to form organs, organs integrate to type organ systems, and organ systems integrate to type organisms (Figure 3.1).

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Figure 3.1. Levels the structural organization of the human body. The organization of the body frequently is questioned in terms of distinct levels of enhancing complexity, from the smallest chemical structure blocks come a distinct human organism.

The levels of Organization

Consider the simplest structure blocks of matter: atoms and also molecules. In Unit 1, you had actually an development to atoms and also molecules. Remember, all issue in the world is written of one or much more unique elements, such together hydrogen, oxygen, carbon, and nitrogen. The the smallest unit of any type of of these aspects is an atom. Atom of individual aspects combine to do molecules, and also molecules bond together to make bigger macromolecules. Four macromolecules—carbohydrates, lipids, proteins, and also nucleic acids (e.g., DNA, RNA)—make up all of the structural and functional systems of cells.

The basic Structural and Functional Unit that Life: The Cell

Cells are the most basic building block of life. Every living things are composed that cells. Brand-new cells room made from preexisting cells, which division in two. Who you are has actually been determined due to the fact that of 2 cells that came with each other inside your mother’s womb. The two cells containing every one of your genetic information (DNA) unify to begin the advancement of a brand-new organism. Cells divided and also differentiated into other cell with particular roles that caused the formation of the body’s countless organs, systems, blood, blood vessels, bones, tissues, and also skin. While all cells in an individual contain the exact same DNA, each cell just expresses the genetic codes that relate to the cell’s particular structure and function.

As an adult, you are made up of trillions that cells. Every of her individual cells is a compact and efficient type of life—self-sufficient, however interdependent top top the various other cells within her body to supply its needs. There are hundreds of species of cells (e.g., red blood cells, nerve cells, skin cells). Every individual cell conducts all the an easy processes that life. It need to take in nutrients, excrete wastes, detect and also respond come its environment, move, breathe, grow, and also reproduce. Plenty of cells have actually a brief life span and also have come be replaced continually. For example, enterocytes (cells the line the intestines) are changed every 2-4 days, and skin cell are changed every couple of weeks.

Although a cabinet is characterized as the “most basic” unit of life, it is structurally and also functionally complex (Figure 3.2). A human being cell frequently consists of a flexible external cell membrane (also called a plasma membrane) the encloses cytoplasm, a water-based cellular fluid, along with a selection of to work units referred to as organelles. The oribelles are like tiny organs created from number of macromolecules external inspection together. A typical animal cell has the complying with organelles:

Nucleus: homes genetic product (DNA)Mitochondria: often dubbed the powerhouse of the cell, generates usable power for the cell from energy-yielding nutrientsRibosomes: assemble proteins based upon genetic codeEndoplasmic reticulum: processes and also packages proteins and also lipidsGolgi apparatus (golgi body): distributes macromolecules favor proteins and also lipids around the cellLysosomes: digestive pouches which breakdown macromolecules and also destroy foreign invaders

Figure 3.2. The cabinet structure

Tissues, Organs, organ Systems, and also Organisms

A tissue is a team of many comparable cells that share a common structure and work together to do a particular function. There space four basic types of human tissues: connective, i m sorry connects tissues; epithelial, i beg your pardon lines and protects organs; muscle, i beg your pardon contracts because that movement and support; and nerve, i m sorry responds and also reacts to signal in the environment.

An organ is a group of similar tissues arranged in a particular manner to execute a details physiological function. Examples include the brain, liver, and heart. An organ mechanism is a group of 2 or an ext organs that work together to perform a details physiological function. Examples incorporate the digestive device and central nervous system.

There room eleven unique organ systems in the human being body (Figure 3.3). Assigning organs to organ systems have the right to be imprecise due to the fact that organs the “belong” to one device can likewise have functions integral to an additional system. In fact, countless organs contribute to more than one system. And also most the these body organ systems are involved in nutrition-related functions within the body (Table 3.1). Because that example, the cardiovascular system plays a role in nutrition by transporting nutrients in the blood come the cell of the body. The endocrine mechanism produces hormones, countless of i beg your pardon are involved in regulating appetite, digestive processes, and nutrient level in the blood. Even the reproductive mechanism plays a role in offering nutrition to a occurring fetus or growing baby.

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Organ System

Major body organ Components

Major Functions


Heart, blood/lymph vessels, blood, lymph

Transport oxygen, nutrients, and also waste products


Mouth, esophagus, stomach, intestines, salivary glands, pancreas, liver and also gallbladder

Digestion and absorption


Endocrine glands (e.g., thyroid, ovaries, pancreas)

Produce and also release hormones, regulate nutrient levels


White blood cells, lymphatic tissue, marrow

Defend against foreign invaders


Skin, nails, hair, sweat glands

Protection, human body temperature regulation


Skeletal, smooth, and also cardiac muscle

Body movement


Brain, spinal cord, nerves

Interpret and respond to stimuli, appetite control


Gonads, genitals

Reproduction and sexual characteristics


Lungs, nose, mouth, throat, trachea

Gas exchange (oxygen and carbon dioxide)


Bones, tendons, ligaments, joints

Structure and support, calcium storage


Kidneys, bladder, ureters

Waste excretion, water balance

Table 3.1. The eleven body organ systems in the person body and their major functions

An organism is the highest possible level the organization—a finish living system capable of conducting every one of life’s organic processes. In multicellular organisms, including humans, all cells, tissues, organs, and organ solution of the body job-related together to preserve the life and also health the the organism.