Cellular Adaptation: Understanding Adaptive Cellular Responses

Cellular Adaptation

• Cells adapt to increased work demands or threats to survival by changing their size (atrophy and hypertrophy), number (hyperplasia), and form (metaplasia)
• Normal cellular adaptation occurs in response to an appropriate stimulus and ceases once the need for adaptation has ceased

Dysplasia

• Characterized by deranged cell growth of specific tissue that results in cells that vary in size, shape, and organization
• Strongly implicated as a precursor to cancer
• Adaptive and potentially reversible if irritating cause is removed
• Mostly occurs in respiratory tract and uterine cervix
• Examples: cervical cancer develops in a series of incremental epithelial changes from severe dysplasia to invasive cancer

Cell Injury and Death: Mechanisms of Cell Injury

• At least three major mechanisms whereby most injurious agents exert their effects:
  • Free radical formation
  • Oxidative damage has been implicated in many diseases
  • Oxidative stress is thought to play an important role in the development of cancer

Free Radicals

• Highly reactive chemical species with an unpaired electron in the outer orbit (valence shell) of the molecule
• Unpaired electron causes free radicals to be unstable and highly reactive, so they react nonspecifically with molecules in the vicinity

Klinefelter Syndrome

• Condition of testicular dysgenesis accompanied by the presence of one or more extra X chromosomes in excess of the usual male XY complement
• Males with Klinefelter syndrome have congenital hypogonadism, which results in an inability to produce normal amounts of testosterone accompanied by an increase in hypothalamic gonadotrophic hormones

Mitochondrial Gene Disorders

• Mitochondria contain their own DNA, which is distinct from the DNA contained in the cell nucleus
• Multiple disease-causing rearrangements and mutations can occur in mitochondrial DNA (mtDNA)

Stress

• Period of Vulnerability: the embryo's development is most easily disturbed during the period when differentiation and development of the organs are taking place
• Caregiver stress contributes to abuse of older adults, highlighting the importance of educating about available resources and support systems
• Resilience (coping skills to effectively deal with stress) will help the child to achieve balance

Innate and Adaptive Immunity

• Intact skin is the most formidable physical barrier available to infection
• Epithelial cells line and protect the gastrointestinal, respiratory, and urogenital tracts and physically prevent microorganisms from entering the body
• When pathogens breach the epithelial defenses, the innate immune response is initiated by the body's leukocytes, which recognize common surface receptors present on the invading microorganisms

Infectious Disease Terminology

• Host: any organism capable of supporting the nutritional and physical growth requirements of another
• Infection: presence and multiplication within a host of another living organism, with subsequent injury to the host
• Microflora: internal and external exposed surfaces of the human body are normally and harmlessly inhabited by a multitude of bacteria

Disorders of the Conjunctiva

• Allergic: usually characterized by itching, bilateral tearing, and redness of the eye
• Viral: common cause is adenovirus, symptoms include generalized conjunctival hyperemia, copious tearing, and minimal exudate
• Bacterial: burning, tearing, mucopurulent or purulent discharge, usually begins in one eye and within 24 to 48 hours it spreads to the unaffected eye