Body balance and disease

Acid-Base balance in the body

The acid-base balance is a basic concept that the medical assistant needs to understand when learning about the physiology of the body. Knowing the normal pH range of the body and how the body adjusts to keep the pH within the normal range helps one to understand how homeostasis is maintained.

pH of the body

The pH refers to the acid-base level of a solution on a scale of 1 to 14. A neutral pH is 7. An acidic solution has a pH under 7 and contains more hydrogen ions. A base or an alkaline solution has a pH over 7 and contains fewer hydrogen ions.

To maintain homeostasis, the body attempts to keep the pH between 7.35 and 7.45.

To maintain the acid-base range in the body, the concentration of hydrogen ions must remain constant. If the pH moves outside of this range, serious illness or even death can occur.

Factors that change the acid-base balance

The pH of our bodies can change based on the food we eat, the air we breathe, and the urine we excrete. To help maintain the pH range, the urinary system, the respiratory system, and chemical buffers must all work together.

Buffers (e.g., bicarbonate) work to prevent changes in the pH. If there are more hydrogen ions, which will lower the pH, buffers will absorb some of the hydrogen ions. This will raise the pH. If the pH is too high, the buffers will “donate” hydrogen ions, bringing the pH down to the normal range.

The respiratory system regulates the carbon dioxide (CO₂) in our blood. CO₂ in the blood can combine with water to form the buffer bicarbonate. If a person hyperventilates (breathes rapidly), the CO₂ levels in the blood decrease, which also causes a decrease in the bicarbonate levels in the blood. This causes the pH of the body to rise.

The urinary system also has a role in the acid-base levels. The kidneys can absorb more base or more acid, depending on what the body needs for homeostasis. The kidneys can also produce bicarbonate if needed.

Pathology basics

Pathology is the study of diseases. In the ambulatory care setting, many patients’ visits relate to the diagnosis or treatment of one or more disease processes. As a person ages, it is common to have more than one chronic illness.

Sidenote

Why this matters

Understanding common diseases helps medical assistants better understand the conditions discussed throughout the body system chapters.

The body system chapters that follow will cover the most common diseases affecting the system discussed. This chapter provides you with the basics to help you understand the concepts discussed in the future chapters. Common pathology terminology, protective mechanisms in the body, predisposing factors for disease, and causes of disease will be discussed.

Pathology terminology

As you learn more about diseases, you will notice different terms used. Here is a list of terms commonly used when discussing pathology:

Definitions

Disease

A specific illness with a recognizable group of signs and symptoms and a clear cause (e.g., infection, environment)

Syndrome

A group of signs and symptoms that occur together and are associated with a condition

Disorder

A disruption of the function or structure of the body; many times, the words disorder and disease are used interchangeably in healthcare

Prevalence

How often the disease occurs

Incidence

Reflects the number of people newly diagnosed with the disease

Morbidity

Illness

Mortality

Death

Acute

A severe, sudden onset of a disease

Chronic

A disease, disorder, or syndrome that lasts longer than 6 months

Prognosis

A medical prediction of the outcome of the disease or disorder process

Prevention

Methods to avoid getting the disease

The specialty chapters will discuss common diseases. For most of the diseases, the following sections will be discussed. It is important for the medical assistant to be familiar with the terminology used:

Definitions

Etiology

The cause of the disorder or disease

Sign

Something that is measured or observed by others; also called objective data. Examples of signs include redness, swelling or edema, blood pressure, and pulse.

Symptom

Something that is only perceived by the patient; also called subjective data. Examples include pain, headache, dizziness, and nausea. Many times, signs and symptoms are used interchangeably, but there is a difference in their definitions.

Diagnostic procedures

Tests and procedures that are used to help diagnose or monitor a condition

Treatments

Management of a disease or disorder; can include follow-up care and home treatments (e.g., medications, special diets, testing)

Protection mechanisms

The body has built-in mechanisms that protect against infection. The body’s first line of defense includes chemical and physical barriers.

The body’s first line of defense consists of physical and chemical barriers that help prevent pathogens from entering the body.

Consider these examples:

• Skin forms a waterproof barrier.
• Tears and saliva contain an enzyme that breaks the cell wall of the pathogen.
• Mucus is a slick secretion produced in the respiratory, reproductive, and digestive systems. It protects the tissues and traps substances (e.g., bacteria, dust).
• Cilia are fine hairs that work closely with the mucus in the respiratory tract, trapping substances.
• Stomach acid is a very strong acid that kills bacteria, parasites, and other invaders that are swallowed.
• “Good” bacteria found on the skin and in the digestive system prevent “bad” bacteria from taking over.
• Urine flushes pathogens from the bladder and urethra.

If the structures are altered (e.g., a cut in the skin), pathogens can get into the body. When this happens, the second line of defense, the immune system, kicks in. White blood cells and the lymphatic system work together to protect the body.

Predisposing factors

Predisposing factors are risk factors for disease. These factors make it more likely or increase the risk that the person may develop the disease or condition. Some predisposing factors can be changed to reduce the risk of developing a disease, whereas others cannot be changed.

Predisposing factors include the following:

• Hereditary or genetic factors: Certain diseases can be inherited, or members of a family can have a higher-than-normal risk of getting a specific disease.
• Age: Certain diseases occur in childhood, whereas others occur more often in older adults. Some diseases occur as a result of changes in the body structures with age. For instance, the ear structures in an infant are different from those of an older person. Degenerative diseases occur in the older generations due to the wear and tear on the structures.
• Sex: Certain diseases occur more in one sex than the other. For instance, testicular cancer affects males, whereas uterine cancer affects females. Sometimes both sexes may get a disease, but one sex has a higher risk factor. Women are at higher risk for breast cancer than men.
• Environmental factors: Certain diseases are more common when a person has been exposed to pollutants in the air, land, or water. Though pesticides can reduce the risk of disease (e.g., West Nile virus disease and rabies), exposure to certain pesticides has been found to increase the risk of cancer.
• Lifestyle: Stress, poor diet, infrequent exercise, or abuse of nicotine, alcohol, or drugs can increase the risk for disease.

Causes of disease

Disease can result from a change in homeostasis or can be the result of the body’s response to a perceived threat. There are several common causes of diseases, including genetics, infectious pathogens, inflammatory processes, immunity, nutritional imbalance, trauma and environmental agents, and neoplasms.

The following sections describe these causes.

Genetics

Each person is made up of 46 chromosomes, which carry genetic information (genes). We get 23 chromosomes from each of our parents. Genes are the basic units of heredity or the instructions on how our bodies should develop and function. Genes provide the differences among us and the similarities in families. From genes we get our physical appearance and our susceptibility to disease.

Recall that chromosomes are found in the cell’s nucleus. During the process of conception and the cell division that follows, an extra chromosome or a change in the chromosome structure may occur. A genetic disease may result from a chromosomal error or the patient inheriting a defective gene from either parent.

Types of monogenic disorders

A monogenic disorder is caused by a single defective gene that is inherited from one or both parents. There are three main categories of monogenic disorders:

• Dominant. The child only needs to inherit one defective dominant gene to get the disease. Examples of autosomal dominant disorders include Huntington’s disease, Marfan syndrome, and neurofibromatosis type 1 (NFI).

• Recessive. The child would need to inherit a defective, recessive gene from both parents to get the disease. Examples of autosomal recessive disorders include cystic fibrosis, Tay-Sachs disease, sickle cell anemia, albinism, and phenylketonuria (PKU).

• X-linked. Sex determination is based on the father:

  • Dominant X-linked traits appear in a person who inherits one defective X chromosome. Fragile X syndrome (FXS) is an example of a dominant X-linked disorder. Both males and females are affected, but females usually have milder symptoms.
  • For recessive X-linked traits, the female would need two recessive X-linked genes to get the disorder. Because the male only has one X chromosome, inheriting one recessive X-linked gene will produce the recessive trait. Red-green color blindness and hemophilia A are examples of X-linked recessive conditions.

X and Y Chromosomes

The X and Y chromosomes are sex chromosomes. A biological female will have two X chromosomes, one from each parent. A biological male will have an X chromosome and a Y chromosome. The X chromosome comes from the mother and the Y chromosome from the father.

Sidenote

Remember!

The X chromosome is much larger than the Y chromosome and contains significantly more genes.

The X chromosome is about three times the size of the Y chromosome. The X chromosome contains more than 900 genes, also called X-linked genes. The Y chromosome only has about 55 genes, which are called Y-linked genes. These traits are only expressed in males.

With a chromosomal disorder, an abnormal number of chromosomes or a change in the chromosomal structure causes the disease.

These are examples of chromosomal disorders:

• Down syndrome: The person has an extra chromosome.
• Trisomy X syndrome: The female has three X chromosomes.
• Turner syndrome: The female inherits only one copy of the X chromosome.