From
the smallest to the largest, six levels of organization will helps us to
understand anatomy and physiology: the chemical, cellular, tissue, organ,
system, and organismal levels of organization.
1)
Chemical
level: This very basic
level and includes atoms, the smallest units of matter that participate
in chemical reactions, and molecules, two or more atoms joined together.
Certain atoms, such as carbon (C), hydrogen (H), oxygen (O), nitrogen (N),
phosphorus (P), calcium (Ca), and sulfur (S), are essential for maintaining
life. Two familiar molecules found in the body are deoxyribonucleic acid (DNA),
the genetic material passed from one generation to the next, and glucose,
commonly known as blood sugar.
2)
Cellular
level: Molecules combine
to form cells, the basic structural and functional units of an organism
that are composed of chemicals. Cells are the smallest living units in the
human body. Among the many kinds of cells in your body are muscle cells, nerve
cells, and epithelial cells.
3)
Tissue
level: Tissues are groups
of cells and the materials surrounding them that work together to perform a
particular function. There are just four basic types of tissues in your body:
epithelial tissue, connective tissue, muscular tissue, and nervous tissue.
Epithelial tissue covers body surfaces, lines hollow organs and cavities, and
forms glands. Connective tissue connects, supports and protects body
organs while distributing blood vessels to other tissues. Muscular tissue contracts
to make body parts move and generates heat. Nervous tissue carries
information from one part of the body to another through nerve impulses.
4)
Organ
level: At the organ
level different types of tissues are joined together. Organs are
structures that are composed of two or more different types of tissues; they
have specific functions and usually have recognizable shapes. Examples of
organs are the stomach, skin, bones, heart, liver, lungs, and brain. For
example, several tissues make up the stomach. The stomach’s outer covering is a
layer of epithelial tissue and connective tissue that reduces friction when the
stomach moves and rubs against other organs. Underneath are three layers of a
type of muscular tissue called smooth muscle tissue, which contracts to
churn and mix food and then push it into the next digestive organ, the small
intestine. The innermost lining is an epithelial tissue layer that
produces fluid and chemicals responsible for digestion in the stomach.
5)
System
level: A system consists
of related organs with a common function. An example of the system level, also
called the organsystem level, is the digestive system, which breaks down
and absorbs food. Its organs include the mouth, salivary glands, pharynx
(throat), esophagus (food tube), stomach, small intestine, large intestine,
liver, gallbladder, and pancreas. Sometimes an organ is part of more than one
system. The pancreas, for example, is part of both the digestive system and the
hormone-producing endocrine system.
6)
Organismal
level: All the parts of
the human body functioning together constitute the total organism.
The Eleven Systems of the Human Body
1)
INTEGUMENTARY
SYSTEM
· Components:
Skin and associated
structures, such as hair, fingernails and toenails, sweat glands,
and oil glands.
· Functions:
Protects body; helps regulate body
temperature; eliminates some wastes; helps
make
vitamin D; detects sensations such as touch, pain, warmth, and cold.
2)
SKELETAL SYSTEM
·
Components: Bones
and joints of the body and their
associated cartilages.
· Functions:
Supports and protects body; provides surface area
for muscle attachments; aids body movements; houses cells that produce blood
cells; stores minerals and lipids (fats).
3)
MUSCULAR SYSTEM
·
Components: Specifically,
skeletal muscle tissue—muscle usually attached to bones (other muscle
tissues include smooth and cardiac).
· Functions:
Participates in body movements, such as
walking; maintains posture; produces heat.
4)
NERVOUS SYSTEM
·
Components: Brain,
spinal cord, nerves, and special sense organs, such as eyes
and ears.
· Functions:
Generates action potentials (nerve impulses)
to regulate body activities; detects changes in body’s internal and external
environments, interprets changes, and responds by causing muscular contractions
or glandular secretions.
5)
ENDOCRINE SYSTEM
·
Components: Hormone-producing
glands (pineal gland, hypothalamus, pituitary gland, thymus, thyroid gland,
parathyroid glands, adrenal glands, pancreas, ovaries, and testes) and
hormone-producing cells in several other organs.
· Functions:
Regulates body activities by releasing
hormones (chemical messengers transported in blood from endocrine gland or
tissue to target organ).
6)
CARDIOVASCULAR
SYSTEM
· Components:
Blood, heart, and
blood vessels.
· Functions:
Heart pumps blood through blood vessels; blood
carries oxygen and nutrients to cells and carbon dioxide and wastes away from
cells and helps regulate acid–base balance, temperature, and water content of
body fluids; blood components help defend against disease and repair damaged blood
vessels.
7)
LYMPHATIC SYSTEM
AND IMMUNITY
·
Components: Lymphatic
fluid and vessels; spleen, thymus, lymph nodes, and
tonsils; cells that carry out immune responses (B cells, T cells, and
others).
· Functions:
Returns proteins and fluid to blood; carries
lipids from gastrointestinal tract to blood; contains sites of maturation and
proliferation of B cells and T cells that protect against disease-causing
microbes.
8)
RESPIRATORY
SYSTEM
·
Components: Lungs
and air passageways such as the pharynx (throat),
larynx (voice box), trachea (windpipe), and bronchial tubes leading
into and out of lungs.
· Functions:
Transfers oxygen from inhaled air to blood and
carbon dioxide from blood to exhaled air; helps regulate acid–base balance of
body fluids; air flowing out of lungs through vocal cords produces sounds.
9)
DIGESTIVE SYSTEM
· Components:
Organs of gastrointestinal tract, a long tube
that includes the mouth, pharynx (throat), esophagus (food tube),
stomach, small and large intestines, and anus; also includes
accessory organs that assist in digestive processes, such as salivary
glands, liver, gallbladder, and pancreas.
· Functions:
Achieves physical and chemical breakdown of
food; absorbs nutrients; eliminates solid wastes.
10) URINARY
SYSTEM
·
Components: Kidneys,
ureters, urinary bladder, and urethra.
o
Functions: Produces,
stores, and eliminates urine; eliminates wastes and regulates volume and chemical
composition of blood; helps maintain the acid–base balance of body fluids;
maintains body’s mineral balance; helps regulate production of red blood cells.
11) REPRODUCTIVE
SYSTEMS
·
Components: Gonads
(testes in males and ovaries in
females) and associated organs (uterine tubes, uterus, vagina, and mammary
glands in females and epididymides, ductus deferens, seminal vesicles,
prostate, and penis in males).
o
Functions: Gonads
produce gametes (sperm or oocytes) that unite to form a new organism; gonads
also release hormones that regulate reproduction and other body processes;
associated organs transport and store gametes; mammary glands produce milk.
