Organization of the Human (Structure and Function) (Nursing) Part 1

Learning Objectives

1. Define the term homeostasis and relate this to the study of anatomy and physiology.

2. Define the terms chemistry, physics, and matter. State how these concepts relate to homeostasis.

3. State the three types of matter and describe the three states of matter.

4. Describe the basic organization of atoms, elements, compounds, and mixtures.

5. Explain the difference between a physical and a chemical change.

6. Demonstrate the ability to break down medical terms into the root, prefix, and suffix.

7. Define and differentiate among anatomy, physiology, and pathophysiology.

8. Demonstrate the anatomic position, describing its importance in healthcare. Differentiate among the sagittal, transverse, and frontal planes.

9. Define the following terms relating to body direction: superior, inferior, anterior, posterior, proximal, distal, ventral, and dorsal.

10. Describe the four basic structural levels of the body, differentiating among each level.

11. Identify the basic structural elements of the human cell, describing the functions of each element.

12. Differentiate between RNA and DNA.

13. Compare and contrast mitosis and meiosis.

14. List the four major types of tissue. Give an example of each.


15. Identify the major organs that make up each body system.

IMPORTANT TERMINOLOGY

anabolism

element

physical change

anatomic position

enzyme

physiology

anatomy

eponym

plane

atom

frontal

plasma membrane

body cavity

gene

platelet

catabolism

homeostasis

protoplasm

cell

medical terminology

quadrant

cell membrane

meiosis

sagittal

chemical change

membrane

system

chromosome

metabolism

tissue

cilia

mitosis

transverse

compound

mixture

ventral

cytoplasm

nucleus

viscera

diaphragm

organ

dorsal

pathophysiology

Acronyms

DNA

RLQ

ER

RNA

LLQ

RUQ

LUQ

WBCs

RBCs

The human body is a precisely structured arrangement of liquids, gases, and solids. The body is made up of atoms, molecules, and chemicals, and is approximately 45% to 75% water, depending on age and sex (see Table 17-1). Many chemical reactions are organized and result in specific independent, yet interrelated, actions. These actions are essential for normal body function. Nurses must be knowledgeable about these concepts because caring for clients involves looking at individual body systems and how alterations in one system affect other systems. Most healthcare is interdisciplinary in nature. Individuals working in some areas, such as the laboratory or pharmacy, use information related to the cellular, molecular, and chemical aspects of the body. Other individuals, including physicians, nurses, and therapists, focus more on body structures and normal and abnormal functioning of complete body systems. All healthcare professionals share a basic understanding of body structure and function and use common terminology when communicating. This topic briefly introduces medical terminology, chemistry, and the science of anatomy and physiology.

CHEMISTRY AND LIFE

Before beginning any course in life science, a basic knowledge of chemistry and physics is important. Chemistry is the science concerned with the structure and composition of matter and the chemical reactions these substances can produce. Physics is the science of the laws of matter and their interactions with energy.

Chemistry is the basis for homeostasis, the dynamic interactions between anatomy and physiology. Homeostasis means physical and emotional equilibrium (balance) and involves an individual’s cumulative chemical reactions, physical condition, and emotional status.

A simplified discussion of chemistry begins with the discussion of matter. Matter can be defined as anything that occupies space and has weight. The three types of matter are elements, compounds, and mixtures. The three states of matter are solids, liquids, and gases.

Elements, Compounds, and Mixtures

All matter, living and nonliving, can be broken down into 92 natural and 20 manufactured elements (Cohen & Wood, 2000). An element is a pure, simple chemical. Twenty-one elements are found in the human body. All elements have specific letter abbreviations, some of which are used in healthcare settings. Seven elements make up approximately 99% of human body weight. These elements and their symbols are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), and calcium (Ca). Elements found in very small amounts, but which are vital to human life, are sodium (Na), chlorine (Cl), potassium (K), iron (Fe), and iodine (I). Other elements found in trace amounts in the body are fluorine (F), chromium (Cr), manganese (Mn), cobalt (Co), copper (Cu), zinc (Zn), selenium (Se), magnesium (Mg), and molybdenum (Mo).

An atom is the smallest part of any element. Atoms are composed of subatomic (smaller than an atom) particles or structures. The main subatomic particles are electrons, protons, and neutrons. Protons and neutrons are located in the nucleus (center) of the atom. Electrons whirl around the nucleus. An atom of one element differs from that of another element owing to the arrangement of its subatomic particles. For instance, a hydrogen atom has one proton and one neutron forming the nucleus, with one electron whirling around it. An oxygen atom has a nucleus composed of eight protons and eight neutrons, with eight electrons whirling around it (Fig. 15-1).

The compound water (H2O). Note the structure of the oxygen and hydrogen atoms.

FIGURE 15-1 · The compound water (H2O). Note the structure of the oxygen and hydrogen atoms.

Atoms of one element are able to interact only with atoms of certain other elements. When atoms of two or more elements react chemically with one another, they form a substance called a compound. In every compound, the elements combine in specific proportions. For example, the most common compound found on earth and in the human body is water. Water forms when two hydrogen atoms combine with one oxygen atom. The two hydrogen atoms each have one electron and one proton. The oxygen atom has eight electrons and eight protons, which because of its specific electrical charge, can combine with only two hydrogen atoms. In chemical shorthand, water is expressed as H2O (two parts hydrogen to one part oxygen).

Not all elements or compounds combine chemically when brought together. A mixture is a blend of two or more substances that have been mixed together without forming a new compound. Salt water (saline) is an example of a mixture. Both the salt and the water remain as separate compounds. Their chemical composition is not changed. They can be brought together in any proportion, and they can be easily separated.

Physical and Chemical Changes

If you lower the temperature of water (normally a liquid) so it freezes, it changes to a solid (ice); if you raise the temperature of the water so it boils, it becomes water vapor (steam, a gaseous state). The water has undergone a physical change, that is, a change in its outward properties. However, the chemical composition is still H2O in any of the three states in which it occurs. Its chemical structure remains unchanged.

If you pass a direct electric current through a sample of water, however, a different change occurs. The water gradually disappears because the electric current causes water to break down into its two invisible gaseous elements: hydrogen and oxygen. A chemical change has occurred. Familiar types of chemical changes are the processes of burning (combustion) and the rusting of iron (oxidation). In chemical reactions, substances change into other substances that no longer have the same chemical structures as before. Completely rusted iron no longer has the same characteristics as iron; burned wood is no longer wood, but ashes and gases.

Key Concept Physical change: Outward properties change, but chemical properties remain the same (e.g., changes in temperature convert water into ice or steam).

Chemical change: One substance changes to another, or the compound breaks down into atoms of elements, and its energy is transferred (e.g., an electric current breaks down water into hydrogen, oxygen, and heat).

MEDICAL TERMINOLOGY

To study body structure and function, an understanding of the vocabulary used in the healthcare field, commonly called medical terminology, is necessary. So much is involved in medical terminology that it is often considered to be a separate course of study.

Sources of Medical Terms

Learning the meaning of a medical term is easier when you break it down into its components. Many medical terms have their roots in Greek or Latin words. Common usage is another source of medical words. Some terms are acronyms, words formed by combining letters of a word or phrase. For instance, MASH stands for “mobile army surgical hospital.” AIDS is an acronym for “acquired immunodeficiency syndrome.” Eponyms are words based on the names of people—for example, Parkinson’s disease or Alzheimer’s disease.

Parts of Words

Most medical terms consist of two or three parts: prefix, root, and suffix. The prefix is at the beginning of a word. Not all medical terms have a prefix.The root of a word is the word’s foundation. All medical terms have at least one root, which may begin the word. The suffix is the word’s ending. Most medical words have a suffix.

A combining vowel (usually o) joins a root to another root or to a suffix, for example, thermometer (therm = heat; meter = measuring device). Medical terminology texts list roots combined with a vowel; this form is known as the combining form. Examples of combining forms are hepat-o (pertaining to the liver), oste-o (pertaining to bone), and neur-o (pertaining to nerves).

Although the root is the core of the word, a prefix or suffix can totally change its meaning. A prefix introduces another thought or explains the root. For example, epigastric means “on the stomach,” whereas hypogastric means “below the stomach.” The suffix is added to clarify, to make a new word, or to change the meaning of the root. For example, tonsillitis means “inflammation of the tonsils,” and tonsillectomy means “removal of the tonsils.”

Prefixes, roots, and suffixes may be used in various combinations. Sometimes a word may be a combination of two or three roots and connecting vowels. For example, electrocardiogram breaks down to the following: a record (suffix: -gram) of electricity (root: electr-) of the heart (root: cardi-). Note the two uses of o as a combining vowel: joining two roots, and joining a root and suffix. Therefore, electrocardiogram means “a record of the electrical activity of the heart.” In comparison, an electroencephalogram is “a record of the electrical activity of the brain” because cephal-o means head or brain.

Medical terms are analyzed by breaking them into components. Start with the suffix, then the prefix, then the root. For example, intravenous:

-ous (suffix) means “pertaining to”

intra- (prefix) means “within”

ven (root) means “vein”

Thus, the word intravenous means “pertaining to within a vein.”

Key Concept Healthcare professionals use medical terminology to communicate assessment findings, diagnostic test results, and other pertinent information.

NCLEX Alert Understanding medical terminology is important when answering NCLEX questions. Appropriate and effective communication, as well as coordination of client care, is demonstrated by correct knowledge of the language of medicine.

ANATOMY AND PHYSIOLOGY

The study of body structure is called anatomy. (Gross anatomy relates to structures that can be observed with the naked eye. Microscopic anatomy requires the use of a microscope or other device.) The study of how the body functions is called physiology. Nursing requires knowledge of body structure as well as how these structures relate to and function with one another. An awareness of normal anatomy and physiology is important before the nurse can begin to understand abnormal conditions, such as disease or injury. The study of functioning disorders is called pathophysiology.

BODY DIRECTIONS, AREAS, AND REGIONS

Now that medical terminology has been introduced, you are ready to apply these terms to body structure and function. Several terms are used to designate areas and directions of the body. These terms help students to specify the location of an organ or system. They also help healthcare professionals to communicate with each other.

Body planes. The body is shown here in anatomic position.

FIGURE 15-2 · Body planes. The body is shown here in anatomic position.

Anatomic Position

Medical texts often present the body from a standard reference point known as anatomic position. The body is pictured standing erect with arms at the sides and palms turned forward (Fig. 15-2). When viewing anatomic pictures or diagrams, the right side of the body is on the left side of the drawing (the same as looking at a person facing you).

Body Planes

A body plane is an imaginary flat surface that divides the body into sections (see Fig. 15-2). The following are planes of the body (which can be imagined in the center or at another position):

Frontal (coronal plane): the vertical plane that passes through the body longitudinally from head to toe, dividing it into front and back parts Sagittal: the vertical plane that passes through the body lengthwise and divides the body into right or left sides; the midsagittal plane passes through the midline from top to bottom, dividing the body into equal right and left halves Transverse: the horizontal plane that passes through the body, dividing it into upper (superior) and lower (inferior) parts

Body Position

In addition to viewing the body in terms of planes, the body is also described by the relationship of one body part to another. These are termed body positions or body directions (Fig. 15-3). Body directions will assist you in describing the locations of organs or body positions. Table 15-1 lists and describes these body directions and positions.

Body Cavities

A body cavity is a space within the body that contains internal organs (viscera). Within the body are two groups of cavities that contain various organs. They are the dorsal (posterior, back) and the ventral (anterior, front) cavities (Fig. 15-4). The dorsal cavity is subdivided into the cranial and spinal cavities. The ventral cavity is subdivided into the thoracic and abdominal cavities. The diaphragm is a large muscle that separates the ventral cavities. Often, the abdominal cavity is subdivided again into the abdominal and pelvic portions or is referred to as the abdominopelvic cavity. (No specific anatomic division exists between the abdominal and pelvic areas.) Table 15-2 lists the contents of each body cavity.

The abdominal cavity can be divided into more precise areas containing specific organs by two different methods. The first method divides the abdomen into four quadrants, using the umbilicus (navel) as a central crossing point for the horizontal (from side to side) and vertical dividing lines. The vertical dividing line extends from the tip of the xiphoid process to the mons pubis. These divisions result in the formation of four quadrants or rectangles referred to as the right upper quadrant (RUQ), right lower quadrant (RLQ), left upper quadrant (LUQ), and left lower quadrant (LLQ) (Fig. 15-5).

The second method uses the costal (rib) margins and pubic bones as horizontal dividing lines for three major regions. The central area above the costal margins is referred to as the epigastric (epi = above; gastr = stomach) region. The central area below the pubic bones is referred to as the hypogastric (hypo = under) or suprapubic (on the pubis) region. The central area between these two dividing lines is referred to as the umbilical region. Corresponding lateral (side) regions are referred to as the left and right hypochondriac; left and right iliac; and between these, the left and right lumbar regions (Fig. 15-6).

(A) Body directions assist in describing the location of organs or body positions. (B) Directional terms.

FIGURE 15-3 · (A) Body directions assist in describing the location of organs or body positions. (B) Directional terms.

 Side view of the body cavities.

FIGURE 15-4 · Side view of the body cavities.

Quadrants of the abdomen, showing some of the organs within each quadrant.

FIGURE 15-5 · Quadrants of the abdomen, showing some of the organs within each quadrant.

TABLE 15-1. Body Directions

POSITION

DEFINITION

EXAMPLES

Superior

"Above” or in a higher position

The knee is superior to the toes, but inferior to the femur

Inferior

"Below” or in a lower position

The lips are inferior to the nose, but superior to the chin.

Cranial

In or near the head

The brain is in the cranial cavity.

Caudal

Near the lower end of the body (i.e., near the end of the spine), "tail”

The buttocks, the muscles on which we sit, are located at the caudal end of the body.

Anterior or ventral

Toward the front or "belly” surface of the body

The nose is on the anterior, or ventral, surface of the head.

Posterior or dorsal

Toward the back of the body

The calf is on the posterior, or dorsal, surface of the leg.

Medial

Nearer the midline

The nose is medial to the eyes.

Lateral

Farther from the midline, toward the side

The ears are lateral to the nose.

Internal

Deeper within the body

The stomach is an internal body organ.

External

Toward the outer surface of the body

The skin covers the external surface of the body.

Proximal

Nearest the origin of a part

In the upper extremity (arm), the area above the elbow is proximal to the forearm below.

Distal

Farthest from the origin of a part

In the lower extremity (leg), the area below the knee is distal to the thigh.

Central

Situated at or pertaining to the center

The brain and the spinal cord are part of the central nervous system.

Peripheral

Situated at or pertaining to the outward part of a surface

The peripheral nerves go out to body parts and return to the central nervous system.

Parietal

Pertaining to the sides or the walls of a cavity

The walls of the abdominal cavity are lined with a membrane called the "parietal peritoneum.”

Visceral

Pertaining to the organs within a cavity

The stomach and intestines are visceral organs in the abdominal cavity.

Supine

Lying with the face upward

A person lying on the dorsal surface of the body (on the back) is supine.

Prone

Lying with the face downward

A person lying on the ventral surface, or the front of the body, is prone.

Deep

Away from the surface

The knife wound was deep in the abdomen.

Superficial

On or near the surface

The child had a superficial cut.

TABLE 15-2. Body Cavities and Their Contents

CAVITY

CONTENTS

Dorsal (Posterior) Cavity

Cranial cavity

Brain

Vertebral cavity (spinal cavity)

Spinal cord

Ventral (Anterior) Cavity (See Figure I5-3A and B.)

Thoracic cavity

•    Pericardial cavity

•    Two pleural cavities Mediastinum

Heart

Each contains a lung Large blood vessels, trachea, esophagus, and thymus gland

Abdominal cavity (abdominopelvic cavity)

• Upper abdominal cavity

Stomach, most of the intestines, liver, gallbladder; pancreas, spleen, kidneys, adrenal glands, and ureter

• Pelvic cavity

Urinary bladder, remaining part of intestines, rectum, and internal reproductive organs

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