BIOL 1310: Introduction to Pathophysiology

• Infection


  A host organism's response to a pathogen, or disease-causing substance. It results when tissue-destroying microorganisms enter and multiply in the body.
• Examples of infections

  • Minor illnesses, such as colds and ear infections
  • Sepsis, a life-threatening organ dysfunction caused by a dysregulated host response to infection
• Types of microorganisms that can cause infection

  • Viruses
  • Bacteria
  • Fungi
  • Parasites
• Viruses


  • Microscopic genetic parasites that contain genetic material, such as DNA or RNA. They have no metabolic capability and need a host cell to replicate.
  • Viral infections occur when normal inflammatory and immune responses fail. The virus develops in the cell and "hides" there.
  • After it's introduced into the host cell, the inner capsule releases genetic material, causing the infection.
  • Some viruses surround the host cell and preserve it; others kill the host cell on contact.
• Bacteria


  • One-celled microorganisms that have no true nucleus and reproduce by cell division.
  • Pathogenic bacteria contain cell-damaging proteins that cause infection.
  • These toxins cause fever and aren't affected by antibiotics.
  • Bacteria are classified by their shape, growth requirements, motility, and whether they are aerobic (requiring oxygen) or anaerobic (don't require oxygen to survive).
  • Exotoxins are released during cell growth, while endotoxins are released when the bacterial cell wall decomposes.
• Fungi


  • Nonphotosynthetic microorganisms that reproduce asexually (by division). They are large compared to other microorganisms and contain a true nucleus.
  • Although fungi are part of the human body's normal flora, they can overproduce, especially when the normal flora is compromised.
  • Infections caused by fungi are called mycotic infections because pathogenic fungi release mycotoxin.
  • Most of these infections are mild unless they become systemic or the patient's immune system is compromised.
• Parasites


  • Organisms that live on or inside another organism (the host), depend on the host for food and protection, and harm the host.
  • Most common parasitic infections, such as pinworm and tapeworm, occur in the intestines.
  • Parasites typically enter the body through the mouth or skin. Ingestion of parasites in contaminated food or water is the most common pathway for infection.
  • Parasites can also enter through the soles of the feet of a person walking barefoot, or through the skin or mouth of a person who swims or bathes in water that contains parasites.
• Infection process


  1. Infection occurs when the body's defense mechanisms break down or when certain properties of microorganisms, such as virulence or toxin production, override the defense system.

  2. Other factors that create a climate for infection include: poor nutrition, stress, humidity, poor sanitation, crowded living conditions, pollution, dust, medications, and hospitalization (health care–associated infection).
• Cancer ranks second to cardiovascular disease as the leading cause of death in the United States
• Cancer


  Malignant neoplasm
• Alteration of apoptosis


  A process where cells evade programmed cell death, leading to uncontrolled cell growth and cancer development
• Every year, more than 1.5 million cancer cases are diagnosed in the United States, and 600,000 people die of cancer-related causes, with more than 1,600 people dying of cancer each day (National Cancer Institute, 2016)
• One-third of these cancer deaths are related to nutrition problems, physical inactivity, obesity, smoking, alcohol use, and other lifestyle factors and could have been prevented
• About 78% of all cancers are diagnosed in people age 55 and older
• Early detection of cancer


  Enables more effective treatment and a better prognosis for the patient
• Abnormal cell growth in cancer

  1. Cancer cells first develop from a mutation in a single cell.

  2. This cell grows without the control that characterizes normal cell growth.

  3. At a certain stage of development, the cancer cell fails to mature into the type of normal cell from which it originated (anaplasia).

  4. In addition to this uncontrolled localized growth, cancer cells can spread from the site of origin, a process called metastasis (cells autonomy).
• Classification of cancers


  • Carcinomas (originate from epithelial tissues)
  • Adenocarcinomas (originate from glandular tissues)
  • Sarcomas (originate from connective, muscle, and bone tissues)
  • Gliomas (originate from tissue of the brain and spinal cord)
  • Melanomas (originate from pigment cells)
  • Myelomas (originate from plasma cells)
  • Lymphomas (originate from lymphatic tissue)
  • Leukemia (originates from leukocytes)
  • Erythroleukemia (originates from erythrocytes)
• Histologic characteristics of cancer cells

  • Cancer is a destructive (malignant) growth of cells, which invades nearby tissues and may metastasize to other areas of the body.
  • Dividing rapidly, cancer cells tend to be extremely aggressive.
• How cancer metastasizes


  Cancer cells metastasize through three mechanisms: by directly spreading by diffusion to other body cavities, by circulation through the blood and lymphatic system, and by direct transportation of cells from one site to another (for example, cells can accidentally be carried to another site on instruments or gloves during surgery or another procedure).
• Causes of cancer


  • Viruses (animal studies show that viruses can transform cells, and certain viruses are associated with specific cancers)
  • Overexposure to ultraviolet radiation (linked to skin cancers)
  • Environmental carcinogens (such as tobacco, asbestos, and alkylating agents)
  • Compromised immune system (transplant recipients and those with AIDS have increased cancer risk)
  • Diet and lifestyle factors (associated with colorectal cancer)
• About 5% of all cancers are strongly hereditary
• Genetics


  The study of heredity, the passing of traits from parents to their children
• Counting chromosomes


  1. A human ovum contains 23 chromosomes.

  2. A sperm also contains 23 chromosomes, each similar in size and shape to a chromosome in the ovum.

  3. When ovum and sperm unite, the corresponding chromosomes pair up. The result is a fertilized cell with 46 chromosomes (23 pairs) in the nucleus.

  4. The fertilized cell soon undergoes cell division (mitosis). In mitosis, each of the 46 chromosomes produces an exact duplicate of itself.

  5. The cell then divides, and each new cell receives one set of 46 chromosomes.

  6. Each of the two cells that result likewise divides, and so on, eventually forming a many-celled human body.

  7. Therefore, each cell in a person's body (except the ova or sperm) contains 46 identical chromosomes.
• Transmitting an inheritance


  Inherited traits are transmitted from parents to offspring through genes in germ cells, or gametes. Human gametes are eggs, or ova, and sperm.
• Chromosomes


  • A human ovum contains 23 chromosomes
  • A sperm also contains 23 chromosomes, each similar in size and shape to a chromosome in the ovum
  • When ovum and sperm unite, the corresponding chromosomes pair up. The result is a fertilized cell with 46 chromosomes (23 pairs) in the nucleus
  • The fertilized cell soon undergoes cell division (mitosis). In mitosis, each of the 46 chromosomes produces an exact duplicate of itself
  • The cell then divides, and each new cell receives one set of 46 chromosomes
  • Each of the two cells that result likewise divides, and so on, eventually forming a many-celled human body
  • Each cell in a person's body (except the ova or sperm) contains 46 identical chromosomes
• Transmitting an inheritance


  1. Inherited traits are transmitted from parents to offspring through genes in germ cells, or gametes

  2. Human gametes are eggs, or ova, and sperm

  3. A person's genetic makeup is determined at fertilization, when ovum and sperm are united

  4. In the nucleus of each germ cell are structures called chromosomes. Each chromosome contains a strand of genetic material called deoxyribonucleic acid (DNA)
• A different division


  1. The ova and sperm are formed by a different cell division process called meiosis

  2. In meiosis, there are two cell divisions, and each new cell (an ovum or sperm) receives one set of 23 chromosomes
• Locus


  The location of a gene on a chromosome
• The locus of each gene is specific and doesn't vary from person to person
• This allows each of the thousands of genes in an ovum to join the corresponding genes from a sperm when the chromosomes pair up at fertilization
• Dominant gene


  The more influential gene that is more likely to be expressed
• Recessive gene


  The less influential gene that is less likely to be expressed
• Allele


  A variation of a gene and the trait it controls
• Heterozygous


  When two different alleles are inherited
• Homozygous


  When the alleles are identical
• If the allele is dominant, only one copy may be necessary for expression of the trait, so a dominant allele may be expressed in both the homozygous and heterozygous states
• A recessive allele is incapable of expression unless recessive alleles are carried by both chromosomes in a pair
• Mutation


  A permanent change in genetic material. When a gene mutates, it may produce a trait that's different from its original trait
• Gene mutations in a gamete may be transmitted during reproduction
• Forms of serious or deadly disorders caused by mutations

  • Single-gene disorders
  • Chromosomal disorders
  • Multifactorial disorders