Describe the essential components of a typical cell and functions

plasma membrane

lipid bilayer, proteins, and carbohydrate

forms the outer surface of cell

site of contact between cell and environment

nucleus

within cell surrounded by nuclear membrance

contains genetic material (DNA), RNA, and proteins

essential for survival of most cells

cytoplasm

matrix of cell

contains hyaloplasm, cytoskeleton, organelles

Mitochondria: consists of outer and inner membranes, site of TCA and oxidative phosphorylation, leads to production of ATP

ER: meshwork of membranes continuous with plasma membrane, is differentiated into RER and SER

Golgi Apparatus: system of tubules and flattened cisterne, processes protein from RER, synthesizes glycoproteins and lipoproteins

Ribosomes: consist of RNA and protein, free/attached to RER, necessary for protein synthesis

Lysosomes: vesicles that break off of golgi apparatus, contain digestive/lytic enzymes

RER: site of protein synthesis

SER: metabolism or hormone synthesis

Maintained through the supply of O2 and nutrients to provide energy to maintain homeostasis

Point of no returnL injury to cell beyond its capacity to return to normal steady state, although this point is poorly understood

Deficiency

1. lack of oxygen, ischemia will decrease ATP formation
2. primary nutrient deficiency
3. secondary nutrient deficiency
4. viral infection: virus infected cells use up nutrients

Intoxication

1. exogenous: microbial toxins, drug OD, chemicals
2. endogenous: accumulation of a normal substance in body to toxic levels

Trauma

1. hypothermia: ice in cytoplasm
2. hyperthermia
3. mechanical pressure
4. microbial injury
5. radiation: production of free radicals
6. immunological injury: Ab, complement

Oxygen radicals are oxygen compounds with an extra electron in their orbital.

Oxygen radicals include superoxides and peroxide which causes cellular damage to DNA, cell membrances, and proteins

They can be formed by normal metabolism, by radiation, chemicals, NO.

Vitamins C and E and other antioxidants are thought to be protective against these

Cellular response to adverse environmental stimulus within range of homeostasis caused by low level injury.

Cell will return to steady state with cessation of stimulus, usually mild and short-lived.

Cells can adapt by changing in size and number

Atrophy: decrease in size of cell

• physiologic: menopause
• pathologic: muscle disuse/denervation

Hypertrophy: increase in size of cell

• physiologic: muscle with exercise
• pathologic: overwork of heart

Hyperplasia: increase in number of cells

• physiologic: uterus in pregnancy
• pathologic: callus on skin with excessive contact

1. Hydrophic changes/vascuolar degeneration: Increased water entry into cell

If an injury decreases cell ability to make ATP, the Na+, K+, ATPase pump of a cell cannot pump Na+ out of the cell, therefore creating increase of osmotic pressure, causing water to enter the cell. 

Increase water causes swelling of cell, increased number of vacuoles, formation of blebs, swelling of organelles.

2. Cell cannot get rid of inclusions, may accumulate fat, lipofuscin

3. Other structural changes: Formation of myelin figures

• distortions and gaps in cell membrane
• myelin figures
• decreased numbers of lysosomes
• nuclear changes which may be either: pyknosis, karyorrhexis, or karyolysis

Programmed cell death

Examples:

embryonic development, hormone dependent changes, inflammation, immune responses, low level injury

Microscopic morphology:

cell shrinkage, chromatin condensation, nuclear fragmentation, blebs, apoptotic bodies, phagocytosis of apoptotic cells and bodies by healthy cells

most common type

• cells die but outline of cell is maintained
• no lysis of cell membrance
• tissue appears like a solid mass of boiled meat
• usually caused by anoxia in solid internal organs

• tissue looks yellow-white, cheesy
• this is coagulative with some liquefaction
• some cells fall apart
• typical of TB

• characterized by dissolution of tissues, which become soft and diffluent, usually soft semifluid

• mush ultimately transformed into a soft fluid-filled cavity

• most often occurs in brain with brain injury

• a special form of liquefactive necrosis limited to fat tissue usually found around the pancreas

• area appear like liquefied fat with chalky soap spots

• happens in acute pancreatitis

• enzymes released by damaged cells break down surrounding fat

Gangrene: Anaerobic bacteria grow in area of coagulative necrosis and produce toxic products

dry: necrotic tissue dries out

wet: some liquefaction occurs in necrotic tissue, due to enzymes of phagocytic cells

Distrophic calcification: Ca++ accumulation in dead/necrotic cells, necrotic tissue is rigid and brittle

Metastatic calcification: occurs in living cells especially lung, kidney, blood vessels, GI lining

ischemia: CNS neurons have high metabolic rate and will die within a few minutes of oxygen deprivation, as in stroke, suffocation, drowning.

CCL4: toxic only to liver cells, since metabolized to a free radical, not metabolized by other cells

ionizing radiation: toxic to rapidly dividing cells

polio virus: can only enter cells of anterior horn of spinal cord