Organ System	Major Organs	Major Functions
Integumentary	Skin, hair, nails, sweat glands, sebaceous glands	Protect tissues, regulate body temperature, support sensory receptors
Skeletal	Bones, ligaments, cartilages	Provide framework, protect soft tissues, provide attach-
		ments for muscles, produce blood cells, store inorganic salts
Muscular	Muscles	Cause movements, maintain posture, produce body heat
Nervous	Brain, spinal cord, nerves, sense organs	Receive and interpret sensory information, stimulate muscles and glands
Endocrine	Glands that secrete hormones: pituitary, thyroid, parathy- roid, adrenal, pancreas, ovaries, testes, pineal, thymus	Control metabolic activities of organs
Cardiovascular	Heart, blood vessels	Move blood and transport substances throughout body
Lymphatic	Lymph vessels and nodes, thymus, spleen	Defend body against infection, return tissue fluid to blood, carry certain absorbed food molecules
Digestive	Mouth, tongue, teeth, salivary glands, pharynx, esophagus, stomach, liver, gallbladder, pancreas, small and large intestines	Receive, break down, and absorb food; eliminate unabsorbed material
Respiratory	Nasal cavity, pharynx, larynx, trachea, bronchi, lungs	Intake and output air, exchange gases between air and blood
Urinary	Kidneys, ureters, urinary bladder, and urethra	Remove wastes from blood, maintain water and electrolyte balance, store and transport urine
Reproductive	Male: scrotum, testes, epididymides, vasa deferentia, sem- inal vesicles, prostate, bulbourethral glands, urethra, penis Female: ovaries, fallopian tubes, uterus, vagina, vulva	Produce and maintain sperm cells, transfer sperm cells into female reproductive tract Produce and maintain egg cells, receive sperm cells, sup- port development of an embryo, function in birth process

BODY SYSTEMS

An body is a structure composed of several tissues that work together to carry

out specific functions. For example, the skin is an organ that has different tissues in

it such as epithelial cells, hair, nails, and glands.

An body system is a group of organs with a specific collective function such as

digestion, circulation, or respiration. For example, the nose, pharynx, larynx, trachea,

bronchi, and lungs work together to achieve the total function of respiration

The different organs in an organ system are usually interconnected. For example,

in the urinary organ system the organs are the kidneys, ureters, bladder,

and urethra, and they are all connected

All your organ systems work together to ensure that your body’s internal environment

remains relatively constant. This process is called homeostasis. It ensures

that cells receive adequate nutrients and oxygen and that their waste products are

removed. Your cells can then function normally. Disease affecting an organ or

organ system disrupts this game plan of homeostasis.

The body has 11 organ systems, shown in. Muscular and skeletal are

considered one organ system, the musculoskeletal system (see Chapter 9). Each body

system has a chapter in this book where the terms associated with it are defined.

COMPOSITION OF THE BODY

• The whole body or organism is composed of organ systems.

• Organ systems are composed of organs.

• Organs are composed of tissues.

• Tissues are composed of cells.

• Cells are composed in part of organelles.

• Organelles are composed of molecules.

• Molecules are composed of

atoms.

THE CELL

The result of the fertilization of an egg by a sperm is a single fertilized cell, the

zygote  This cell is the origin of every cell in your body. It divides and

multiplies into millions of cells that are the basic unit of every tissue and organ.

The structure and all the functions of your tissues and organs are due to their cells.

Cytology is the study of cell structure and function.

BODY CAVITIES

The body contains many cavities. Some, like the nasal cavity, open to the outside.

Five cavities do not open to the outside; they are shown in Figure 2.4 and listed below.

1. Cranial cavity: Contains the brain within the skull.

2. Thoracic cavity: C ontains the heart, lungs, thymus gland, trachea

and esophagus, and numerous blood vessels and nerves.

3. Abdominal cavity: Is separated from the thoracic cavity by the diaphragm

and contains the stomach, intestines, liver, spleen, pancreas, and kidneys.

4. Pelvic cavity: Is surrounded by the pelvic bones and contains the urinary

bladder, part of the large intestine, the rectum and anus, and the internal

reproductive organs.

5. Spinal cavity: Contains the spinal cord.

The abdominal cavity and pelvic cavity can be combined as the abdominopelvic

cavity.

ANATOMICAL PLANES

Different views of the body are based on imaginary “slices” producing flat surfaces

(planes) that pass through the body .

The three major anatomical planes are:

• Transverse or horizontal: A plane passing across the body parallel to the floor

and perpendicular to the body’s long axis. It divides the body into an upper or

superior portion and a lower or inferior portion.

• Saggital: A vertical plane that divides the body into right and left portions.

• Frontal (coronal): A vertical plane that divides the body into front ( anterior )

and back ( posterior ) portions.