Pathopart3

Copyright © 2017, 2013, 2009 Pearson Education, Inc. All Rights Reserved.

Bryan E. BledsoeRichard A. Cherry Robert S. Porter

Paramedic Care: Principles & PracticeVolume 1, 5e

PathophysiologyPart 3



Part 3

Disease at the Cellular Level



Disease at the Cellular Level• The Cell

– Basic unit of all living organisms.– Nucleus: central portion of cell. – Organelles: structures within nucleus that carry out

biological processes.– Prokaryotic cells: do not contain nucleus or organelles.– Eukaryotic cells: contain nucleus and organelles.



Figure 12-32 Eukaryotic cells, such as the generalized animal cell shown here, have internal membrane-bound organelles.(Goodenough, Judith and Betty A. McGuire, Biology of Humans: Concepts, Applications, and Issues, 3rd Edition, © 2010. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ.)



Disease at the Cellular Level• The Plasma Membrane and Cytoplasm

– Plasma membrane: consists of chemicals; phospholipids.

– Cell membrane: lipid bilayer.– Cytoplasm (cytosol): fills inside of cells; water, salts,

organic molecules, enzymes that catalyze biochemical reactions.



Disease at the Cellular Level• The Plasma Membrane and Cytoplasm

– Intracellular fluid: water component of cytoplasm.– Membrane proteins:

Linkers Enzymes Receptors Transporters



Disease at the Cellular Level• Plasma Membrane Functions

– Cells adhere to each other or stick together; cell adhesion molecules (CAMs).

– Cell-cell recognition; ability of cell to distinguish one type of cell from another.

– Maintains structural integrity of cell.



Table 12-7 Mechanism of Transport across the Plasma Membrane

Mechanism DescriptionSimple diffusion Random movement from region of high to region of low

concentrationFacilitated diffusion Movement from region of high to region of low

concentration with the aid of a carrier or channel protein

Osmosis Movement of water from a region of high water concentration (low solute concentration) to a region of low water concentration (high solute concentration)

Active transport Movement from region of high to region of low concentration with the aid of a carrier or channel protein and energy, usually from ATP

Endocytosis Materials engulfed by the plasma membrane and drawn into the cell in a vesicle

Exocytosis Membrane-bound vesicle from inside the cell fuses with the plasma membrane and spills contents outside the cell




– Role in communications between cells.– Regulates movement of substances into and out of

cell.– Simple diffusion: random movement of molecules from

area of higher concentration to area of lower concentration.



Figure 12-36 Simple diffusion is the random movement of molecules from a region of higher concentration to a region of lower concentration. Solutes diffuse across the membrane until equilibrium is reached on both sides.




– Rate of diffusion proportional to concentration gradient across membrane.

– Osmotic gradient: movement of water across semipermeable membrane.

– Osmosis: movement of water molecules from area of high water concentration to area of low water concentration.




– Free water: water free of solute.– Water: universal solvent.– Isotonic: concentrations of solutions on both sides of

semipermeable membrane are equal.– Hypertonic: solution on one side of membrane more

concentrated than solution on other side.




– Osmosis generates pressure: osmotic pressure. – Osmolarity: concentration of solute particles in solution.– Osmolality: measures concentration of particles in body

fluids.




– Facilitated diffusion: no expenditure of metabolic energy; transport assisted by integral proteins in plasma membrane. Carrier proteins Ion channels




– Active transport: cell moves solute across plasma membrane against concentration gradient. Carrier protein; energy in form of ATP.

– Sodium-potassium pump: transport of sodium ions out of cell and potassium ions into cell, against concentration gradient.




– Endocytosis: plasma membrane encircles substance to be ingested. When separated from cell membrane, vesicle released into

cell.

– Phagocytosis: cell engulfs large particles or bacteria.



Figure 12-43 Phagocytosis. The cell engulfs large particles or bacteria.(Goodenough, Judith and Betty A. McGuire, Biology of Humans: Concepts, Applications, and Issues, 3rd Edition, © 2010. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ.)




– Pinocytosis: cell engulfs droplets of fluid carrying dissolved substances.

– Endocytosis: large molecules leave cell by becoming encircled in membrane vesicle.

– Exocytosis: membrane-bound vesicle containing substance to be released from cell approaches cell membrane.



Disease at the Cellular Level• Cellular Environment: Fluids and Electrolytes

– Severe derangements in fluid and electrolyte status can result in death.

– Water: most abundant substance in body (60 percent); total body water (TBW).

– Intracellular fluid (ICF): all fluid found inside body cells.



Table 12-8 Body Fluid Compartments

Compartment Percentage of Total Body Water

Volume in 70-kg Adult (42 L total body water)

Intracellular fluid 70.0 percent 29.40 LExtracellular fluid 30.0 percent 12.60 L

Interstitial fluid 25.0 percent 10.50 LIntravascular fluid 5.0 percent 2.10 L




– Extracellular fluid (ECF): all fluid found outside body cells.

– Intravascular fluid: fluid found outside cells and within circulatory system.

– Interstitial fluid: all fluid found outside cell membranes; not within circulatory system.




– Total body water and distribution vary with age and physiologic condition.

– Infant's TBW is 75 to 80 percent of body weight; 65 percent TBW average adult.

– Elderly, like very young, high risk for dehydration and disorders related to electrolyte imbalances.




– Intake: water coming into body.– Output: water excreted from body.– To maintain homeostasis, intake must equal output.– Thirst regulates fluid intake.– Body maintains fluid balance by shifting water from one

body space to another.




– Dehydration: abnormal decrease in total body water. Gastrointestinal losses Increased insensible loss Increased sweating Internal losses Plasma losses




– Fluid replacement based on fluid and electrolyte deficits.

– Dehydrated patient: dry mucous membranes, poor skin turgor, excessive thirst.

– Overhydration: edema; heart failure may be present.




– Electrolytes: substances that dissociate into electrically charged particles when placed into water.

– Ions: charged particles.– Cations: ions with positive charge.– Anions: ions with negative charge.




– Cations Sodium (Na+) Potassium (K+) Calcium (Ca++) Magnesium (Mg++)




– Anions Chloride (Cl-) Bicarbonate Phosphate

– Electrolytes measured in milliequivalents per liter (mEq/L).




– Body's fluid compartments separated by cell membranes.

– Semipermeable; selectively permeable.– Compounds with small molecules (H2O) pass readily

through membrane; larger compounds (proteins) restricted.




– Movement of fluids through membrane enabled by pores in membrane.

– Electrolytes do not pass through membrane as readily as water due to their electrical charge.

– Water moves across cell membrane to dilute area of increased electrolyte concentration.




– Movement of water more rapid than movement of electrolytes.

– Within extracellular compartment, movement of water between plasma in intravascular space and interstitial space function of forces in capillary beds.




– Blood plasma generates oncotic force. – Hydrostatic pressure: blood pressure; force against

vessel walls by contractions of heart.– Filtration: hydrostatic pressure forces water out of

plasma across capillary wall into interstitial space.– Starling's hypothesis: Net filtration = (Forces favoring

filtration) - (Forces opposing filtration)




– Edema: accumulation of water in interstitial space. Decrease in plasma oncotic force Increase in hydrostatic pressure Increased capillary permeability Lymphatic channel obstruction




– Edema: localized or generalized.– Sign of underlying disease or problem; edema itself

causes problems.– Antidiuretic hormone (ADH) or vasopressin: chief

regulator of water retention and distribution.



Disease at the Cellular Level• Intravenous Therapy (IV)

– Introduction of fluids and other substances into venous side of circulatory system. Replace blood lost through hemorrhage Electrolyte or fluid replacement Medications directly into vascular system



Disease at the Cellular Level• Intravenous Therapy

– Blood: fluid of cardiovascular system.– Transports nutrients, oxygen, hormones, heat.– Plasma: liquid portion.– Blood cells: formed elements.

Red blood cells: erythrocytes White blood cells: leukocytes Platelets: thrombocytes




– Erythrocytes: hemoglobin; transports oxygen; 99 percent of blood cells.

– Hemoglobin: iron-based compound that binds with oxygen.

– Leukocytes: responsible for immunity and fighting infection.

– Thrombocytes: major role in blood clotting.



Figure 12-49 Blood components.




– Plasma can be separated from formed elements by centrifugation.

– Hematocrit: percentage of blood occupied by erythrocytes.

– Most desirable fluid for blood loss replacement is whole blood.



Table 12-9 Resuscitation Fluids

Resuscitation Fluid UsedDiagnosis 1st Choice 2nd Choice 3rd Choice 4th ChoiceHemorrhagic shock

Whole blood Packed RBCs Plasma or plasma substitute

Lactated Ringer's or normal saline

Shock due to plasma loss (burns)

Plasma Plasma substitute

Lactated Ringer's or normal saline

—

Dehydration Lactated Ringer's or normal saline

— — —




– Blood often fractionated (separated into parts); packed red blood cells used.

– Typed and cross-matched to prevent severe allergic reaction.

– Transfusion reactions: discrepancy between blood type of patient and blood type of blood being transfused.




– Intravenous fluids: colloids and crystalloids.– Colloid: proteins; remain in intravascular space for

extended period. Plasma protein fraction (Plasmanate) Salt-poor albumin Dextran Hetastarch (Hespan)




– Crystalloids: primary compounds used in prehospital intravenous fluid therapy. Isotonic solutions Hypertonic solutions Hypotonic solutions

– Intravenous replacement fluids: needs of patient; underlying problem.




– Most commonly used solutions in prehospital care: Lactated Ringer's solution 0.9 percent sodium chloride (normal saline) 5 percent dextrose in water (D5W)

– Lactated Ringer's solution and normal saline used for fluid replacement.



Disease at the Cellular Level• Organelles and Their Functions

– Nucleus: largest organelle; contains cell's genetic information.

– Genetic information encoded by base sequences on DNA molecule.

– DNA controls cell functions and production of specific proteins.

– Genetic information on threadlike structures called chromosomes.



Figure 12-52 Diagram of the nucleus. (Goodenough, Judith and Betty A. McGuire, Biology of Humans: Concepts, Applications, and Issues, 3rd Edition, © 2010. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ.)




– Humans: 46 chromosomes (23 pairs).– Nuclear envelope: double membrane encases nucleus.– Nucleoplasm: chromatin and materials inside nucleus.– Nuclear pores: openings in nuclear envelope.




– Nucleolus: region of DNA active in production of ribosomal RNA (rRNA).

– Ribosomes: synthesis of polypeptides and proteins.– Endoplasmic reticulum: network of tubules, vesicles,

sacs; interconnect with plasma membrane, nuclear envelope, other organelles in cell.




– Rough endoplasmic reticulum (RER): contains ribosomes during protein synthesis.

– Smooth endoplasmic reticulum (SER): without ribosomes.

– Endoplasmic reticulum: role in replenishment and maintenance of plasma membrane.



Figure 12-55 The endoplasmic reticulum has rough and smooth portions. Rough endoplasmic reticulum (RER) has ribosomes attached during protein synthesis. Smooth endoplasmic reticulum (SER) has no attached ribosomes and serves various functions, depending on the cell type.(Goodenough, Judith and Betty A. McGuire, Biology of Humans: Concepts, Applications, and Issues, 3rd Edition, © 2010. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ.)




– Golgi apparatus (Golgi complex): processes proteins for cell membrane and other cell organelles.

– Lysosomes: "garbage disposal system" of cells. Break down foreign substances and invaders; degrade worn

out parts of cell. Process macromolecule products.




– Vacuoles: membrane-bound organelles used for temporary storage or transport of substances.

– Peroxisomes: generate and degrade hydrogen peroxide (H2O2); highly toxic to cells. Detoxify harmful substances; regulation of oxygen tension

within cell.




– Mitochondria: "powerhouses" of cells; provide energy needed for all of cell's biochemical processes.

– Cellular respiration.– Cristae: inner membrane folds form shelves within

mitochondria.



Disease at the Cellular Level• Cytoskeleton and Internal Cell Structures

– Microtubules: long, hollow rods made of protein tubulin. – Microfilaments: made from protein actin.– Centrioles: cylindrical structures composed of groups

of microtubules.



Figure 12-58 Mitochondria are sites of energy conversion in the cell.(Goodenough, Judith and Betty A. McGuire, Biology of Humans: Concepts, Applications, and Issues, 3rd Edition, © 2010. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ.)



Disease at the Cellular Level• Cytoskeleton and Internal Cell Structures

– Cytoskeleton: three-dimensional structure; serves as skeleton for cell stability.

– Cilia: hairlike structures that move in back-and-forth motion.

– Flagella: much longer than cilia; move in undulating, wavelike manner.



Disease at the Cellular Level• Cellular Respiration and Energy Production

– Digestive system breaks down nutrients: carbohydrates, proteins, lipids.

– Cellular respiration: aerobic; requires oxygen. – Fermentation: anaerobic; does not require oxygen.




– Oxidation: loss of electrons from one atom to another.– Reduction: gain of electrons by one atom from another.– Three biochemical processes glucose molecule must

pass to produce energy through cellular respiration: glycolysis, citric acid cycle, electron transport.




– Glycolysis Occurs in cytoplasm; breakdown of six-carbon sugar glucose. Energy-using and energy-yielding phases.

– Citric acid cycle (Kreb's cycle or tricarboxylic acid [TCA] cycle): Completely oxidizes remainder of glucose molecule.




– Electron Transport Chain Five types of carriers. Electrons transferred from one molecule to next; energy

released. Passed to oxygen; ultimate electron acceptor.




– Fermentation Breakdown of glucose without oxygen Final electron acceptor is pyruvate, not oxygen Very inefficient Lactic acid fermentation Alcohol fermentation



Disease at the Cellular Level• Cellular Response to Stress

– Cellular adaptation: physiologic and structural changes to cell, in response to change or stress. Hyperplasia Hypertrophy Atrophy Metaplasia




– Hyperplasia: increase in number of cells in tissue or organ. Hormonal hyperplasia: stimulation by hormones. Compensatory hyperplasia: increase in tissue mass following

tissue injury or loss. Can be pathological.




– Hypertrophy: increase in size of cells in tissue or organ. Due to creation of more structural components within cell Physiologic hypertrophy: increased physical demand Pathological hypertrophy: abnormal stress




– Atrophy: decrease in size of cell. May be physiologic (effect of hormones) or pathological (result

of disease or injury).

– Metaplasia: cell can change from one adult cell type to another adult cell type; reversible. Protects organism from stress.



Figure 12-67 Abnormal cell responses to stress include hypertrophy, hyperplasia, atrophy, metaplasia, and dysplasia.



Disease at the Cellular Level• Cell Injury and Cell Death

– Cells stressed to point they can no longer adapt, or exposed to toxic agents, cell injury results.

– Cell injury persistent or severe, cell death occurs.– Irreversibly damaged cells undergo necrosis or

apoptosis; normal process of keeping body healthy.




– Ischemia: diminished blood flow.– Hypoxia: decreased availability of oxygen. – Cellular respiration impaired; energy production limited

to glycolysis.




– Oxygen free radicals steal electrons from other compounds and generate new species of free radicals. Process can continue until components of cell used up.

– Various chemicals, including drugs, can cause injury to a cell.




– Apoptosis: cellular program activated; causes release of enzymes that destroy genetic material within nucleus of cell and selected proteins in cytoplasm. Can be physiologic or pathological.

– Dysplasia: abnormal or disordered growth in a cell. Precursor to development of cancer.

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