Organization of the Body
CHAPTER OBJECTIVES
• To name the body systems and their functions
• To identify body cavities and specific organs within them
• To list the divisions of the back
• To identify three planes of the body
• To analyze, pronounce, and spell new terms
Body Systems
All the parts of your body are composed of individual units called cells. Examples are muscle, nerve, skin (epithelial), and bone cells.
Similar cells grouped together are tissues. Groups of muscle cells are muscle tissue, and groups of epithelial cells are epithelial tissue.
Collections of different tissues working together are organs. An organ, such as the stomach, has specialized tissues, such as muscle, epithelial (lining of internal organs and outer layer of skin cells), and nerve, that help the organ function.
Groups of organs working together are the systems of the body. The digestive system, for example, includes the mouth, throat (pharynx), esophagus, stomach, and intestines, which bring food into the body, break it down, and deliver it to the bloodstream.
Figure 2-1 reviews the differences between cells, tissues, organs, and systems. There are 11 systems of the body, and each plays an important role in the way the body works.
The circulatory system (heart, blood, and blood vessels such as arteries, veins, and capillaries) transports blood (containing all types of blood cells) throughout the body. The lymphatic system includes lymph vessels, and nodes that carry a clear fluid called lymph. Lymph contains white blood cells called lymphocytes that fight against disease and play an important role in immunity.
The digestive system brings food into the body and breaks it down so that it can enter the bloodstream. Food that cannot be broken down is then removed from the body at the end of the system as waste.
The endocrine system, composed of glands, sends chemical messengers called hormones into the blood to act on other glands and organs.
The female and male reproductive systems produce the cells (eggs and sperm) that join to form the embryo. Male (testis) and female (ovary) sex organs produce hormones as well.
The musculoskeletal system, including muscles, bones, joints, and connective tissues, supports the body and allows it to move.
The nervous system carries electrical messages to and from the brain and spinal cord.
The respiratory system controls breathing, a process by which air enters and leaves the body.
The skin and sense organ system, including the skin and eyes and ears, receives messages from the environment and sends them to the brain.
The urinary system produces urine and sends it out of the body through the kidneys, ureters, bladder, and urethra.
Table 2-1, lists selected organs and structures and the systems to which they belong.
Table 2-1
| Organ/Structure | System |
| 1. Bronchial tubes | Respiratory |
| 2. Cerebrum | Nervous |
| 3. Coccyx (tailbone) | Musculoskeletal |
| 4. Colon (large intestine) | Digestive |
| 5. Esophagus (food tube) | Digestive |
| 6. Kidneys | Urinary |
| 7. Larynx (voice box) | Respiratory |
| 8. Lungs | Respiratory |
| 9. Ovaries | Female reproductive/endocrine |
| 10. Pharynx (throat) | Digestive/respiratory |
| 11. Pituitary gland | Endocrine |
| 12. Prostate gland | Male reproductive |
| 13. Spinal cord | Nervous |
| 14. Trachea (windpipe) | Respiratory |
| 15. Ureters | Urinary |
| 16. Urethra | Urinary |
| 17. Uterus | Female reproductive |
| 18. Vertebrae (backbones) | Musculoskeletal |
At the end of the book you will find useful and important reference information. Appendix 1, page 211, contains diagrams of each body system with combining forms for body parts; examples of terminology, pathology, and laboratory tests; and diagnostic and treatment procedures. Appendix 2, page 291, names and explains common diagnostic tests and procedures, and Appendix 3, page 311, defines medical abbreviations, acronyms, and symbols. Appendix 4, page 331, provides health careers information. The Mini-Dictionary: Glossary of Medical Terms, page 341, and the Glossary of Word Parts, page 375, contain definitions of terms and meanings of word parts, respectively. Use these valuable references as you work through this book.
Body Cavities
Figure 2-2 shows the five body cavities. A body cavity is a space that contains organs. Label the figure in the spaces provided as you read the following paragraphs.
The cranial cavity (1) is located in the head and surrounded by the skull (CRANI/O means skull). The cranial cavity contains the brain and other organs, such as the pituitary gland (an endocrine gland located below the brain).
The thoracic cavity (2), also known as the chest cavity (THORAC/O means chest), is surrounded by the breastbone and ribs. The lungs, heart, windpipe (trachea), bronchial tubes (leading from the trachea to the lungs), and other organs are in this cavity.
Figure 2-3 shows a front view of the thoracic cavity. The lungs are each surrounded by a double membrane known as the pleura. The space between the pleural membranes is the pleural cavity. The large area between the lungs (yellow in Figure 2-3) is the mediastinum. The heart, esophagus (food tube), trachea, and bronchial tubes are organs within the mediastinum.
In Figure 2-2, the abdominal cavity (3) is the space below the thoracic cavity. The diaphragm is the muscle that separates the abdominal and thoracic cavities. Organs in the abdomen include the stomach, liver, gallbladder, and small and large intestines.
The organs in the abdomen are covered by a double membrane called the peritoneum (Figure 2-4). The peritoneum attaches the abdominal organs to the abdominal muscles and surrounds each organ to hold it in place.
Turn back to Figure 2-2 and locate the pelvic cavity (4), below the abdominal cavity. The pelvic cavity is surrounded by the pelvis (bones of the hip). The major organs located within the pelvic cavity are the urinary bladder, ureters (tubes from the kidneys to the bladder), urethra (tube from the bladder to the outside of the body), rectum, and anus, and the uterus (muscular organ that nourishes the developing embryo and fetus) in females.
Label the spinal cavity (5) on Figure 2-2. This is the space surrounded by the spinal column (backbones). The spinal cord is the nervous tissue within the spinal cavity. Nerves enter and leave the spinal cord and carry messages to and from all parts of the body.
Double membraneYou can visualize the way organs are surrounded by a double membrane by imagining your fist pushing deep into a soft balloon. The balloon is then in two layers folded over your fist, just the way membranes such as the pleura and peritoneum surround an internal organ. Double wrapping around organs provides protection and cushioning as well as attachment to muscles. In the event of inflammation or disease to organs or membranes, fluid may collect in the space between the membranes and surrounding the organs. This collection of fluid in the pleural cavity is called a pleural effusion. The collection of fluid in the peritoneal cavity is called ascites (see page 62).
As a quick review of the terms presented in this section, match the term with its meaning and write it in the space provided.
Divisions of the Back
The spinal column is a long row of bones from the neck to the tailbone. Each bone in the spinal column is called a vertebra (backbone). Two or more bones are called vertebrae.
A piece of flexible connective tissue, called a disk (or disc), lies between each backbone. The disk, composed of cartilage, is a cushion between the bones. If the disk slips or moves out of its place, it can press on the nerves that enter or leave the spinal cord, causing pain. Figure 2-5 shows a side view of vertebrae and disks.
The divisions of the spinal column are pictured in Figure 2-6. Label them according to the following list:
| DIVISION | BONES | ABBREVIATION |
| 1. Cervical (neck) region | 7 bones | C1-C7 |
| 2. Thoracic (chest) region | 12 bones | T1-T12 |
| 3. Lumbar (loin or waist) region | 5 bones | L1-L5 |
| 4. Sacral (sacrum or lower back) region | 5 fused bones | S1-S5 |
| 5. Coccygeal (coccyx or tailbone) region | 4 fused bones |
Planes of the Body
A plane is an imaginary flat surface. Organs appear in different relationships to one another according to the plane of the body in which they are viewed.
Figure 2-7 shows three planes of the body. Label them as you read the following descriptions:
| 1. Frontal (coronal) plane | A vertical plane that divides the body, or body part such as an organ, into front and back portions. |
| Anatomically, anterior means the front portion and posterior means the back portion. | |
| 2. Sagittal (lateral) plane | A vertical plane that divides the body or organ into right and left sides. The midsagittal plane divides the body vertically into right and left halves. |
| 3. Transverse (axial) plane | A horizontal plane that divides the body or organ into upper and lower portions, as in a cross section. (Think of cutting a long loaf of French bread into circular sections.) |
Knowing the planes of the body is helpful in looking at imaging studies such as x-ray films (radiographs) and computed tomography (CT) scans. See Figure 2-8.
Magnetic resonance imaging (MRI) is another technique for producing images of the body. With MRI, magnetic waves instead of x-rays are used to create the images, which show organs and other structures in specialized detail and in all three planes of the body (Figure 2-9). Figure 2-10 shows a patient undergoing MRI.
Terminology
Write the meanings of the medical terms on the line provided. Check your answers with the Mini-Dictionary Glossary of Medical Terms, page 341.
COMBINING FORMS| COMBINING FORM | MEANING | MEDICAL TERM | MEANING |
| abdomin/o | abdomen | abdominal | ____________________ |
| anter/o | front | anterior | ____________________ |
| The suffix –IOR means pertaining to. | ____________________ | ||
| bronch/o | bronchial tubes (leading from the windpipe to the lungs) | bronchoscopy | ____________________ |
| cervic/o | neck of the body or neck (cervix) of the uterus | cervical | ____________________ |
| You must decide from the context of what you are reading whether cervical means pertaining to the neck of the body or pertaining to the uterine cervix (lower portion of the uterus). Figure 2-11 shows the uterus and the cervix | ____________________ | ||
| chondr/o | cartilage | hypochondriac | ____________________ |
| This term refers to the regions of the abdominopelvic cavity under the cartilage of the ribs. (Figure A on page 77 shows the abdominopelvic regions.) It also describes a person who experiences unusual anxiety about his or her health and has symptoms that cannot be explained. The Greeks thought that organs (liver and spleen) in the hypochondriac regions of the abdomen were the origin of imaginary illnesses. | ____________________ | ||
| coccyg/o | coccyx, tailbone | coccygeal | ____________________ |
| -EAL means pertaining to. | ____________________ | ||
| crani/o | skull | craniotomy | ____________________ |
| epitheli/o | skin, surface tissue | epithelial | ____________________ |
| The term epithelial was first used to describe the surface (EPI means upon) of the breast nipple (THELI/O actually means nipple). More correctly, it describes the cells on the outer layer (surface) of the skin as well as the lining of the internal organs that lead to the outside of the body. | ____________________ | ||
| esophag/o | esophagus (tube from the throat to the stomach) | esophageal ____________________ | ____________________ |
| hepat/o | liver | hepatitis | ____________________ |
| lapar/o | abdomen | laparoscopy | ____________________ |
| laryng/o | larynx (voice box) | laryngeal | ____________________ |
| The larynx (pronounced LAR-inks) is found in the upper part of the trachea. | ____________________ | ||
| laryngectomy | ____________________ |
| later/o | side | lateral |
| lumb/o | loin (waist) | lumbar |
| -AR means pertaining to. A lumbar puncture (“spinal tap”) is the placement of a needle within the membranes in the lumbar region of the spinal cord to inject or withdraw fluid. See Figure 2-12. | ||
| lymph/o | lymph (clear fluid in tissue spaces and lymph vessels) | lymphocyte |
| Lymphocytes are white blood cells that fight disease. One type of lymphocyte (B cell) produces disease-fighting proteins called antibodies. | ||
| mediastin/o | mediastinum (space between the lungs) | mediastinal |
| pelv/o | pelvis (bones of the hip) | pelvic |
| peritone/o | peritoneum (membrane surrounding the abdominal organs) | peritoneal |
| Peritoneal fluid, produced by the peritoneal membrane, lubricates the surfaces of the peritoneum to prevent friction. With inflammation of the peritoneum or disease affecting abdominal organs, fluid may accumulate in the peritoneal cavity. This accumulation of fluid is called ascites (see Figure 2-13). |
| pharyng/o | pharynx (throat) | pharyngeal |
| The pharynx (pronounced FAR-inks) is the common passageway for food from the mouth and air from the nose. See Figure 2-14. | ||
| pleur/o | pleura | pleuritis ____________________ |
| poster/o | back, behind | posterior ____________________ |
| sacr/o | sacrum (fve fused bones in the lower back) | sacral  |
| spin/o | spine (backbone) | spinal |
| thorac/o | chest | thoracotomy |
| thoracic | ||
| trache/o | trachea (windpipe) | tracheotomy |
| See Figure 2-15. | ||
| vertebr/o | vertebra (backbone) | vertebral |
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