1.1

• Categories of human diseases

  • Degenerative diseases
  • Immune disorders
  • Infectious diseases
  • Metabolic disorders
  • Neoplasms (cancers and other types of tumors)
  • Nutritional disorders
  • Psychiatric disorders
• Only infectious diseases are caused by microbes
• Microbial intoxications


  Diseases that follow ingestion of a toxin produced outside the body (in vitro) by a pathogen
• Infectious diseases (or infections)


  Diseases that follow colonization of some body site by a pathogen
• Some infectious diseases affect more than one anatomic site, and some pathogens move from one body site to another during the course of a disease
• Skin


  • Intact skin is a type of nonspecific host defense mechanism, serving as a physical barrier
  • The indigenous microbiota of the skin, a low pH, and the presence of chemical substances, such as lysozyme and sebum, also serve to prevent colonization of the skin by pathogens
• Epidermis


  The superficial portion of the skin
• Dermis


  The inner layer of skin, containing blood and lymphatic vessels, nerves, nerve endings, glands, and hair follicles
• Dermatitis


  Inflammation of the skin
• Sebaceous glands


  Glands in the dermis that usually open into hair follicles and secrete an oily substance known as sebum
• Folliculitis


  Inflammation of a hair follicle, the sac that contains a hair shaft
• Stye (or stye)


  Inflammation of a sebaceous gland that opens into a follicle of an eyelash
• Furuncle


  A localized pyogenic (pus-producing) infection of the skin, usually resulting from folliculitis; also known as a boil
• Carbuncle


  A deep-seated pyogenic infection of the skin, usually arising from a coalescence of furuncles
• Macule


  A surface lesion that is neither raised nor depressed, such as the lesions of measles
• Papule


  A surface lesion that is firm and raised, such as the lesions of chickenpox
• Vesicle


  A blister or small fluid-filled sac, such as is seen in chickenpox and shingles
• Pustule


  A pus-filled surface lesion
• Otitis media


  Infection of the middle ear
• Otitis externa


  Infection of the outer ear canal
• Conjunctiva


  The thin, tough lining that covers the inner wall of the eyelid and the sclera (the white of the eye)
• Conjunctivitis


  An infection or inflammation of the conjunctiva
• Keratitis


  An infection or inflammation of the cornea-the domed covering over the iris and lens
• Keratoconjunctivitis


  An infection that involves both the cornea and the conjunctiva
• Retinitis


  Inflammation that involves the retina. Often caused by viral infection
• Upper respiratory tract (URT)


  Includes the paranasal sinuses, nasopharynx, oropharynx, epiglottis, and larynx ("voice box")
• Lower respiratory tract (LRT)

  Includes the trachea ("windpipe"), bronchial tubes, and alveoli of the lungs
• LRT infections are the most common cause of death from infectious diseases