Pelvis and Changes in Body Weight

Chapter 4: Cellular Biology This chapter explores altered cellular and tissue biology, focusing on cellular adaptation, injury, manifestations of cellular injury, cellular death, aging, and the various types of cell death such as necrosis and apoptosis. Cellular adaptation allows cells to respond to physiological and pathological conditions, but severe or prolonged stressors can lead to cellular injury or death. Common sources of cell injury include lack of oxygen, free radicals, infections, inflammation, and metabolic derangements. Cellular aging also contributes to changes in structure and function. Bullet points Biological aging ● The passage of time cannot be stopped (chronologic aging), but it may be possible to delay the decline in health (biologic aging) Aging: Degenerative Extracellular Changes, Cellular Changes, and Tissue and Systemic Aging ● Degenerative changes: binding of collagen, increase in free radicals, alterations of tendons, ligaments, bones, and joints ● Cellular changes: atrophy, decreased function, loss of cells possibly by apoptosis ● Tissue and systemic aging: progressive stiffness or rigidity affects many systems, thymus atrophy, reproductive system changes, stomach changes, muscular atrophy, decrease in height, reduction in circumference of neck, thighs, and arms Pelvis and Changes in Body Weight ● Pelvis may experience lengthening of the nose and ears ● In middle age, there may be an increase in body weight followed by a decrease in stature, weight, fat-free mass, and body mass ● Increased body fat distribution, particularly abdominal fat, is associated with non-insulin-dependent diabetes and heart disease ● As the amount of fat increases, the percentage of total body water decreases ● Total body potassium concentration decreases Causes of Aging ● Studies suggest that the aging process may be largely influenced by epigenetic factors or influences on gene expression ● It has been suggested that the "aging clock" can be altered by changing the cell's differentiation program Life Span and Life Expectancy ● The maximal life span of humans is generally between 80 to 100 years and does not vary significantly among populations ● Life expectancy is the average number of years of life remaining at a given age ● Improved public health strategies and health advances have increased life expectancy in the United States by about 30 years between 1900 and 2000 ● Life expectancy differs across the United States, and certain populations may not experience the same increase Health Disparities and Frailty ● Health measures and life expectancy in the United States lag behind those of other high-income countries, despite high healthcare spending ● Chronic health problems associated with modifiable risk factors contribute to soaring medical costs and burden individuals and families ● Frailty is a common clinical syndrome in older adults characterized by overall weakness, decreased stamina, and functional decline ● Frailty is influenced by multiple aging mechanisms, including genetic and epigenetic factors, as well as environmental factors ● Frailty can involve osteopenia, cognitive impairment, anemia, and other alterations ● Differences between men and women in frailty presentation include muscle mass, hormone levels, immune function, and activity levels Sarcopenia and Cachexia ● Sarcopenia and cachexia are common consequences of aging and can also occur as a result of chronic illnesses Epigenetic Mechanisms ● Epigenetic factors can influence gene expression and play a role in the aging process Frailty ● Frailty is a disorder of multiple interrelated physiologic systems ● A gradual decline progresses with aging, but in frailty this decline becomes accelerated ● Homeostatic mechanisms begin to fail, and vulnerability becomes disproportionate to changes in health status after a relatively minor stressor event Somatic death ● Somatic death is systemic death of the entire body ● Postmortem change is diffuse and does not involve an inflammatory response ● Immediate manifestations include the complete cessation of respiration and circulation Stages after somatic death ● Pallor mortis: The surface of the skin becomes pale and yellowish ● Algor mortis: Body temperature decreases gradually after death, then decreases more rapidly ● Rigor mortis: Muscles stiffen due to the depletion of ATP ● Livor mortis: Blood settles in dependent tissues, causing blue-purple discoloration ● Putrefaction: Tissues and organs break down into gaseous and liquid matter Stages of decomposition after death: ● Putrefaction occurs most rapidly in ambient air ● Discoloration of the skin, particularly over the abdomen, is the first sign ● Slippage or loosening of the skin from underlying tissues occurs ● Black discoloration to the tissues follows ● Gases with characteristic odors are released ● Gas buildup leads to swelling or bloating ● Liquefactive changes occur as internal organs begin to liquefy ● Decomposition occurs when the body's organic matter is broken down and recycled ● Skeletonization occurs when tissues have degraded, exposing the skeleton ● Fossilization, a rare stage, may occur where bones are replaced with mineral deposits Summary of cellular adaptation: ● Cellular adaptation is a reversible response to physiological or pathological conditions ● Types of cellular adaptation include atrophy, hypertrophy, hyperplasia, metaplasia, and dysplasia ● Atrophy is a decrease in cellular size and can be caused by aging, disuse, or insufficient blood supply ● Hypertrophy is an increase in cell size in response to mechanical stimuli ● Hyperplasia is an increase in the number of cells due to increased cell division ● Metaplasia is the reversible replacement of one mature cell type with another less mature cell type ● Dysplasia is an abnormal change in the size, shape, and organization of mature tissue cells Summary of cellular injury: ● Injury to cells and extracellular matrix leads to tissue and organ injury ● Cellular injury affects structural patterns Cellular Injury and Death ● Cellular injury occurs when the cell fails to maintain homeostasis due to insult or stress ● Injured cells may recover (reversible injury) or die (irreversible injury) Biochemical Events in Cell Injury and Death ● ATP depletion leads to mitochondrial damage ● Accumulation of oxygen and radical oxygen species (ROS) causes membrane damage ● Increased intracellular calcium concentration and loss of calcium steady state ● Mitochondrial damage causes loss of membrane potential and activation of cell death ● Membrane damage and protein folding defects Common Forms of Cell Injury ● Ischemic and hypoxic injury ● Ischemia-reperfusion injury ● Oxidative stress or accumulation of oxygen-derived free radicals ● Chemical injury Hypoxia and Ischemia ● Hypoxia is the lack of sufficient oxygen in cells ● Ischemia, or reduced blood supply, is the most common cause of cellular injury