6 Levels Of Body Organization

Theme 1: What Makes Us Unique?

1.1 Structural Organization of the Human Body

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Earlier you begin to study the different structures and functions of the human torso, it is helpful to consider its basic architecture; that is, how its smallest parts are assembled into larger structures. It is convenient to consider the structures of the body in terms of fundamental levels of system that increase in complication: subatomic particles, atoms, molecules, organelles, cells, tissues, organs, organ systems, organisms and biosphere ( Effigy one ).

Levels of Structural Organization of the Human Torso

This illustration shows biological organization as a pyramid. The chemical level is at the apex of the pyramid where atoms bond to form molecules with three dimensional structures. An example is shown with two white hydrogen atoms bonding to a red oxygen atom to create water. The next level down on the pyramid is the cellular level, as illustrated with a long, tapered, smooth muscle cell. At this level, a variety of molecules combine to form the interior fluid and organelles of a body cell. The next level down is the tissue level. A community of similar cells forms body tissue. The example given here is a section of smooth muscle tissue, which contains many smooth muscle cells closely bound side by side. The next level down is the organ level, as illustrated with the bladder and urethra. The bladder contains smooth muscle while the urethra contains skeletal muscle. These are both examples of muscle tissues. The next level down is the organ system level, as illustrated by the entire urinary system containing the kidney, ureters, bladder and urethra. At this level, two or more organs work closely together to perform the functions of a body system. At the base of the pyramid is the organismal level illustrated with a woman drinking water. At this level, many organ systems work harmoniously together to perform the functions of an independent organism. — **Effigy i.** The organisation of the body often is discussed in terms of six singled-out levels of increasing complexity, from the smallest chemical building blocks to a unique homo organism.

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The Levels of Organization

To written report the chemic level of organization, scientists consider the simplest building blocks of matter: subatomic particles, atoms and molecules. All thing in the universe is composed of one or more than unique pure substances called elements, familiar examples of which are hydrogen, oxygen, carbon, nitrogen, calcium, and atomic number 26. The smallest unit of any of these pure substances (elements) is an atom. Atoms are fabricated upwardly of subatomic particles such as the proton, electron and neutron. Two or more atoms combine to form a molecule, such every bit the water molecules, proteins, and sugars constitute in living things. Molecules are the chemical building blocks of all torso structures.

Acell is the smallest independently functioning unit of measurement of a living organism. Even bacteria, which are extremely small, independently-living organisms, have a cellular construction. Each bacterium is a unmarried cell. All living structures of human anatomy contain cells, and most all functions of human physiology are performed in cells or are initiated by cells.

A man cell typically consists of flexible membranes that enclose cytoplasm, a water-based cellular fluid together with a variety of tiny functioning units called organelles. In humans, every bit in all organisms, cells perform all functions of life. A tissue is a grouping of many like cells (though sometimes composed of a few related types) that work together to perform a specific role. Anorgan is an anatomically distinct construction of the body composed of two or more tissue types. Each organ performs ane or more specific physiological functions. Anorgan system is a grouping of organs that piece of work together to perform major functions or meet physiological needs of the trunk.

Figure ii shows some of the organ systems of the body that nosotros will consider over the grade of this semester. Many organs have functions integral to more than i organ system.

Organ Systems of the Human Trunk

The lymphatic system returns fluid to the blood and defends against pathogens. The lymphatic system includes the thymus in the chest, the spleen in the abdomen, the lymphatic vessels that spread throughout the body, and the lymph nodes distributed along the lymphatic vessels. The respiratory system removes carbon dioxide from the body and delivers oxygen to the blood. The respiratory system includes the nasal passages, the trachea, and the lungs. The digestive system processes food for use by the body and removes wastes from undigested food. The digestive system includes the stomach, the liver, the gall bladder (connected to the liver), the large intestine, and the small intestine. The urinary system controls water balance in the body and removes and excretes waste from the blood. The urinary system includes the kidneys and the urinary bladder. The reproductive system of males and females produce sex hormones and gametes. The male reproductive system is specialized to deliver gametes to the female while the female reproductive system is specialized to support the embryo and fetus until birth and produce milk for the infant after birth. The male reproductive system includes the two testes within the scrotum as well as the epididymis which wraps around each testis. The female reproductive system includes the mammary glands within the breasts and the ovaries and uterus within the pelvic cavity. — **Figure 2.** Organs that work together are grouped into organ systems.

The organism level is the highest level of organization considered in anatomy/physiology. An organism is a living being that has a cellular structure and that tin can independently perform all physiologic functions necessary for life. In multicellular organisms, including humans, all cells, tissues, organs, and organ systems of the trunk work together to maintain the life and wellness of the organism.

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Section Summary

Life processes of the human torso are maintained at several levels of structural organization. These include the chemical, cellular, tissue, organ, organ system, and the organism level. College levels of organisation are built from lower levels. Therefore, molecules combine to form cells, cells combine to course tissues, tissues combine to class organs, organs combine to form organ systems, and organ systems combine to form organisms.