Essentials of Pathophysiology: Concepts of Altered Health States (Point (Lippincott Williams & Wilkins))

864 Pages·2006·33.86 MB·English

by  Carol Mattson Porth

Contents
UNIT ONE UNIT TWO
Mechanisms of Disease Alterations in Body Defenses
1 Cell Structure and Function 1 7 Stress and Adaptation 121
Edward W. Carroll Mary Pat Kunert
Functional Components of the Cell 2 Homeostasis 122
Cell Metabolism and Energy Sources 7 Stress 123
Cell Membrane Transport, Signal Transduction, Disorders of the Stress Response 128
and Generation of Membrane Potentials 9
8 The Immune Response 134
Body Tissues 14
Cynthia V. Sommer
2 Tissue Adaptation and Injury 24 The Immune System 134
Developmental Aspects of the Immune System 148
Cellular Adaptation 24
Cell Injury and Death 27 9 Inflammation, Tissue Repair,
and Fever 150
3 Genetic Control of Cell Function 36
Cynthia V. Sommer, Carol M. Porth
Edward W. Carroll The Inflammatory Response 150
Genetic Control of Cell Function 36
Tissue Repair and Wound Healing 157
Chromosomes 41
Temperature Regulation and Fever 161
Patterns of Inheritance 44
Gene Mapping and Technology 46 10 Alterations in the
Immune Response 168
4 Genetic and Congenital Disorders 50
Carol M. Porth, Kathleen Sweeney
Genetic and Chromosomal Disorders 50 Allergic and Hypersensitivity Disorders 168
Disorders Due to Environmental Influences 58 Transplantation Immunopathology 174
Autoimmune Disorders 175
5 Alterations in Cell Growth Immunodeficiency Disorders 178
and Replication: Neoplasia 64
UNIT THREE
Kathryn Ann Caudell
Concepts of Cell Growth 64 Alterations in the Hematologic System
Characteristics of Benign
and Malignant Neoplasms 67 11 Alterations in White Blood Cells 191
Carcinogenesis and Causes of Cancer 72
Kathryn Ann Caudell, Kathryn J. Gaspard
Clinical Features 77 Hematopoietic and Lymphoid Tissue 191
Childhood Cancers 81 Non-neoplastic Disorders of White Blood Cells 194
Neoplastic Disorders of Hematopoietic
6 Alterations in Fluids, Electrolytes,
and Lymphoid Origin 197
and Acid-Base Balance 84
12 Alterations in Hemostasis
Composition and Compartmental Distribution
of Body Fluids 84 and Blood Coagulation 205
Sodium and Water Balance 90 Kathryn J. Gaspard
Potassium Balance 99 Mechanisms of Hemostasis 205
Calcium and Magnesium Balance 103 Hypercoagulability States 209
Acid-Base Balance 108 Bleeding Disorders 210
xix
xx Contents
13 Alterations in Red Blood Cells 216 21 Alterations in Respiratory Function:
Kathryn J. Gaspard Disorders of Gas Exchange 376
The Red Blood Cell 216 Disorders of Lung Inflation 376
Anemia 220 Obstructive Airway Disorders 380
Polycythemia 227 Interstitial Lung Diseases 390
Age-Related Changes in Red Blood Cells 227 Pulmonary Vascular Disorders 392
Respiratory Failure 395
UNIT FOUR
Alterations in the Cardiovascular System UNIT SIX
Alterations in the Urinary System
14 Structure and Function of
the Cardiovascular System 231 22 Control of Kidney Function 401
Organization of the Circulatory System 232 Kidney Structure and Function 402
Principles of Blood Flow 233 Tests of Renal Function 412
The Heart as a Pump 236
Blood Vessels and the Peripheral Circulation 246 23 Alterations in Renal Function 415
Neural Control of Circulatory Function 251 Congenital and Hereditary Disorders of the Kidney 415
Obstructive Disorders 417
15 Alterations in Blood Flow 254 Urinary Tract Infections 421
Disorders of the Arterial Circulation 254 Disorders of Glomerular Function 425
Disorders of the Venous Circulation 266 Tubulointerstitial Disorders 429
Disorders of Blood Flow Caused by Neoplasms 430
Extravascular Forces 269
24 Renal Failure 433
16 Alterations in Blood Pressure 274 Acute Renal Failure 433
Control of Blood Pressure 274 Chronic Renal Failure 436
Hypertension 279 Renal Failure in Children and Elderly Persons 443
Orthostatic Hypotension 287
25 Alterations in Urine Elimination 446
17 Alterations in Cardiac Function 291 Control of Urine Elimination 446
Disorders of the Pericardium 291 Alterations in Bladder Function 449
Coronary Heart Disease 294 Cancer of the Bladder 456
Myocardial and Endocardial Disease 302
Valvular Heart Disease 308
UNIT SEVEN
Heart Disease in Infants and Children 312
Alterations in the
18 Heart Failure and Circulatory Shock 320 Gastrointestinal System
Candace Hennessy, Carol M. Porth
Heart Failure 320 26 Structure and Function of
Circulatory Failure (Shock) 330 the Gastrointestinal System 459
Heart Failure in Children and the Elderly 336
Structure and Organization of
the Gastrointestinal Tract 460
UNIT FIVE Innervation and Motility 463
Alterations in the Respiratory System Hormonal and Secretory Function 466
Digestion and Absorption 468
Anorexia, Nausea, and Vomiting 471
19 Structure and Function of
the Respiratory System 339 27 Alterations in Gastrointestinal
Structural Organization of the Respiratory System 340 Function 473
Exchange of Gases Between the Atmosphere
Disorders of the Esophagus 473
and the Lungs 344
Disorders of the Stomach 476
Exchange and Transport of Gases 351
Disorders of the Small and Large Intestines 480
Control of Breathing 356
20 Alterations in Respiratory Function:
Infectious Disorders and Neoplasia 359
Respiratory Tract Infections 359
Cancer of the Lung 367
Respiratory Disorders in Infants and Children 369
Contents xxi
28 Alterations in Hepatobiliary 35 Sexually Transmitted Diseases 627
Function 494 Patricia McCowen Mehring
The Liver and Hepatobiliary System 494 Infections of the External Genitalia 627
Disorders of the Liver 500 Vaginal Infections 630
Disorders of the Gallbladder and Extrahepatic Vaginal-Urogenital-Systemic Infections 632
Bile Ducts 510
Disorders of the Exocrine Pancreas 513 UNIT TEN
Alterations in the Nervous System
29 Alterations in Body Nutrition 517
Joan Pleuss
36 Organization and Control of
Regulation of Food Intake and Energy Metabolism 517
Overnutrition and Obesity 521 the Nervous System 637
Undernutrition 524 Edward W. Carroll, Robin L. Curtis
Nervous Tissue Cells 637
Nerve Cell Communication 641
UNIT EIGHT
Development and Organization of
Alterations in the Endocrine System
the Nervous System 644
The Spinal Cord and Brain 651
30 Organization and Control of The Autonomic Nervous System 660
the Endocrine System 529
37 Alterations in Brain Function 667
Glenn Matfin, Safak Guven, Julie A. Kuenzi
The Endocrine System 529 Diane Book
Brain Injury 668
31 Alterations in Pituitary, Thyroid, Cerebrovascular Disease 679
Parathyroid, and Adrenal Function 538 Infections and Neoplasms 685
Seizure Disorders 688
Glenn Matfin, Safak Guven, Julie A. Kuenzi
Dementias 691
General Aspects of Altered Endocrine Function 538
Pituitary and Growth Hormone Disorders 539
38 Alterations in Neuromuscular
Thyroid Disorders 545
Parathyroid Hormone Disorders 551 Function 696
Disorders of Adrenal Cortical Function 552 Carol M. Porth, Robin L. Curtis
The Organization and Control of Motor Function 696
32 Diabetes Mellitus 560 Skeletal Muscle and Peripheral Nerve Disorders 702
Safak Guven, Julie A. Kuenzi, Glenn Matfin Basal Ganglia and Cerebellum Disorders 709
Energy Metabolism 560 Upper and Lower Motoneuron Disorders 713
Diabetes Mellitus 565 Spinal Cord Injury 716
39 Pain 725
UNIT NINE
Elizabeth C. Devine
Alterations in the Male and Female
Organization and Control of
Reproductive Systems
Somatosensory Function 725
Pain 731
33 Alterations in the Male Alterations in Pain Sensitivity and Special Types
Reproductive System 581 of Pain 739
Headache 741
Physiologic Basis of Male Reproductive Function 581
Pain in Children and Older Adults 744
Disorders of the Penis, the Scrotum and Testes,
and the Prostate 587
40 Alterations in Special Sensory
Disorders in Childhood and Aging Changes 597
Function 747
34 Alterations in the Female Edward W. Carroll, Susan A. Fontana
Reproductive System 602 The Eye and Disorders of Vision 747
The Ear and Disorders of Auditory Function 763
Patricia McCowen Mehring
The Vestibular System and Maintenance
Structure and Function of the Female
of Equilibrium 772
Reproductive System 602
Disorders of the Female Reproductive Organs 607
Menstrual Disorders 619
Disorders of the Breast 622
xxii Contents
44 Alterations in Skin Function
UNIT ELEVEN
Alterations in the Skeletal and Integrity 835
and Integumentary Systems Gladys Simandl
Structure of the Skin 835
Manifestations of Skin Disorders 839
41 Structure and Function of Skin Damage Caused by Ultraviolet Radiation 841
the Skeletal System 779 Primary Disorders of the Skin 842
Characteristics of Skeletal Tissue 779 Nevi and Skin Cancers 853
Skeletal Structures 785 Age-Related Skin Manifestations 857
42 Alterations in the Skeletal System:
Trauma, Infection, and Glossary 863
Developmental Disorders 789
APPENDIX A: Lab Values 873
Kathleen E. Gunta
Injury and Trauma of Musculoskeletal Structures 789
Bone Infections 799 APPENDIX B: Weblinks 875
Neoplasms 802
Index 879
Disorders of Skeletal Growth and Development
in Children 805
43 Alterations in the Skeletal System:
Metabolic and Rheumatoid
Disorders 814
Debra Bancroft Rizzo, Kathleen E. Gunta
Metabolic Bone Disease 814
Rheumatic Disorders 820
Rheumatic Diseases in Children and the Elderly 832
UNIT
One
Mechanisms
of Disease
CHAPTER
1
Cell Structure and Function
Signal Transduction and Cell Communication
Functional Components of the Cell
Cell Membrane Receptors
The Nucleus
Messenger-Mediated Control of Nuclear Function
The Cytoplasm and Its Organelles
Membrane Potentials
Ribosomes
Electrical Potentials
Endoplasmic Reticulum
Action Potentials
Golgi Complex
Body Tissues
Lysosomes and Peroxisomes
Cell Differentiation
Mitochondria
Embryonic Origin of Tissue Types
The Cytoskeleton
Epithelial Tissue
Microtubules
Simple Epithelium
Microfilaments
Stratified and Pseudostratified Epithelium
The Cell Membrane
Glandular Epithelium
Cell Metabolism and Energy Sources
Connective or Supportive Tissues
Anaerobic Metabolism
Loose Connective Tissue
Aerobic Metabolism
Dense Connective Tissue
Cell Membrane Transport, Signal Transduction,
Muscle Tissue
and Generation of Membrane Potentials
Skeletal Muscle
Movement Across the Cell Membrane
Smooth Muscle
Passive Movement
Cell Junctions and Cell-to-Cell Adhesion
Active Transport and Cotransport
Endocytosis and Exocytosis
Ion Channels
The cell is the smallest functional unit that an organism
can be divided into and retain the characteristics neces-
sary for life. Cells with similar embryonic origin or func-
tion are often organized into larger functional units called tis-
sues.These tissues in turn combine to form the various body
structures and organs. Although the cells of different tissues
1
2 Unit One: Mechanisms of Disease
and organs vary in structure and function, certain characteris- proteins, glycoproteins, and lipoproteins. Lipids comprise
tics are common to all cells. Cells are remarkably similar in 2% to 3% of most cells. The most important lipids are the
their ability to exchange materials with their immediate envi- phospholipids and cholesterol, which are mainly insoluble in
ronment, obtaining energy from organic nutrients, synthesiz- water; they combine with proteins to form the cell membrane
ing complex molecules, and replicating themselves. Because and the membranous barriers that separate different cell com-
most disease processes are initiated at the cellular level, an un- partments. Some cells also contain large quantities of triglyc-
derstanding of cell function is crucial to understanding the dis- erides. In the fat cells, triglycerides can constitute up to 95% of
ease process. Some diseases affect the cells of a single organ, the total cell mass. The fat stored in these cells represents stored
others affect the cells of a particular tissue type, and still others energy, which can be mobilized and used wherever it is needed
affect the cells of the entire organism. in the body. Few carbohydrates are found in the cell, and these
are used primarily for fuel. Potassium, magnesium, phosphate,
sulfate, and bicarbonate ions are the major intracellular elec-
FUNCTIONAL COMPONENTS
trolytes. Small quantities of sodium, chloride, and calcium
OF THE CELL
ions are also present in the cell. These electrolytes facilitate the
generation and transmission of electrochemical impulses in
Although diverse in their organization, all eukaryotic cells nerve and muscle cells. Intracellular electrolytes participate in
(cells with a true nucleus) have in common structures that per- reactions that are necessary for cellular metabolism.
form unique functions. When seen under a light microscope,
three major components of the eukaryotic cell become evident:
The Nucleus
the nucleus, the cytoplasm, and the cell membrane (Fig. 1-1).
The internal matrix of the cell is called protoplasm. Proto- The nucleus of the cell appears as a rounded or elongated struc-
plasm is composed of water, proteins, lipids, carbohydrates, ture situated near the center of the cell (see Fig. 1-1). It is en-
and electrolytes. Water makes up 70% to 85% of the cell’s closed in a nuclear membrane and contains chromatin and a
protoplasm. The second most abundant constituents (10% to distinct region called the nucleolus.All eukaryotic cells have at
20%) of protoplasm are the cell proteins, which form cell struc- least one nucleus (prokaryotic cells, such as bacteria, lack a nu-
tures and the enzymes necessary for cellular reactions. Proteins cleus and nuclear membrane). The nucleus is the control cen-
can also be found complexed to other compounds as nucleo- ter for the cell. It contains deoxyribonucleic acid (DNA) that is
Cilia
Microvilli
Secretory
vesicles
Nuclear
pores
Mitochondrion
Golgi
apparatus
Nucleolus
Free
Nuclear envelope
ribosomes
surrounding nucleus
Peroxisome
Rough
endoplasmic Microtubule
reticulum
Lysosome
Cell
membrane
■FIGURE 1-1■ Composite cell
Chromatin designed to show in one cell all of
Smooth the various components of the
endoplasmic reticulum nucleus and cytoplasm.
Chapter 1: Cell Structure and Function 3
membrane contains many structurally complex circular pores
KEY CONCEPTS
where the two membranes fuse to form a gap. Many classes of
THE FUNCTIONAL ORGANIZATION molecules, including fluids, electrolytes, RNA, some proteins,
OF THE CELL and perhaps some hormones, can move in both directions
through the nuclear pores.
■ Cells are the smallest functional unit of the body.
They contain structures that are strikingly similar to The Cytoplasm and Its Organelles
those needed to maintain total body function.
The cytoplasm surrounds the nucleus, and it is in the cyto-
■ The nucleus is the control center for the cell. It also plasm that the work of the cell takes place. Cytoplasm is es-
contains most of the hereditary material. sentially a colloidal solution that contains water, electrolytes,
suspended proteins, neutral fats, and glycogen molecules.
■ The organelles, which are analogous to the organs
Although they do not contribute to the cell’s function, pig-
of the body, are contained in the cytoplasm. They
ments may also accumulate in the cytoplasm. Some pigments,
include the mitochondria, which supply the energy such as melanin, which gives skin its color, are normal con-
needs of the cell; the ribosomes, which synthesize stituents of the cell.
proteins and other materials needed for cell func- Embedded in the cytoplasm are various organelles, which
tion; and the lysosomes, which function as the cell’s function as the organs of the cell. These organelles include the
digestive system. ribosomes, endoplasmic reticulum, Golgi complex, lysosomes
and peroxisomes, and mitochondria.
■ The cell membrane encloses the cell and provides for
intracellular and intercellular communication, trans- Ribosomes
port of materials into and out of the cell, and main- The ribosomes serve as sites of protein synthesis in the cell.
tenance of the electrical activities that power cell They are small particles of nucleoproteins (rRNA and pro-
function. teins) that can be found attached to the wall of the endoplas-
mic reticulum or as free ribosomes (Fig. 1-2). Free ribosomes
are scattered singly in the cytoplasm or joined by strands of
mRNA to form functional units called polyribosomes.Free ribo-
somes are involved in the synthesis of proteins, mainly as
essential to the cell because its genes contain the information
intracellular enzymes.
necessary for the synthesis of proteins that the cell must pro-
duce to stay alive. These proteins include structural proteins
Endoplasmic Reticulum
and enzymes used to synthesize other substances, including
The endoplasmic reticulum (ER) is an extensive system of
carbohydrates and lipids. The genes also represent the individ-
paired membranes and flat vesicles that connects various parts
ual units of inheritance that transmit information from one gen-
of the inner cell (see Fig. 1-2). The fluid-filled space, called the
eration to another. The nucleus is also the site of ribonucleic
acid (RNA) synthesis. There are three types of RNA: messenger
RNA (mRNA), which copies and carries the DNA instructions
for protein synthesis to the cytoplasm; ribosomal RNA (rRNA), Rough ER
which moves to the cytoplasm, and becomes the site of protein Ribosomes
synthesis; and transfer RNA (tRNA), which also moves into the
cytoplasm, where it transports amino acids to the elongating
protein as it is being synthesized (see Chapter 3).
The complex structure of DNA and DNA-associated proteins
dispersed in the nuclear matrix is called chromatin.Each DNA
molecule is made up of two extremely long, double-stranded Matrix
helical chains containing variable sequences of four nitroge-
nous bases. These bases form the genetic code. In cells that are
about to divide, the DNA must be replicated before mitosis,or
cell division, occurs. During replication, complementary pairs
Tubular elements
of DNA are generated such that each daughter cell receives an
of the ER
identical set of genes.
The nucleus also contains the darkly stained round body
Free
called the nucleolus.The rRNA is transcribed exclusively in the
ribosomes
nucleolus. Nucleoli are structures composed of regions from
five different chromosomes, each with a part of the genetic
Smooth
code needed for the synthesis of rRNA. Cells that are actively ER
synthesizing proteins can be recognized because their nu- Vesicular elements
cleoli are large and prominent and the nucleus as a whole is of the ER
euchromatic.
■FIGURE 1-2■Three-dimensional view of the rough endoplas-
Surrounding the nucleus is a doubled-layered membrane mic reticulum (ER) with its attached ribosomal RNA and the
called the nuclear envelope or nuclear membrane. The nuclear smooth endoplasmic reticulum.
4 Unit One: Mechanisms of Disease
matrix,between the paired ER membrane layers is connected
with the space between the two membranes of the double-
layered nuclear membrane, the cell membrane, and various
cytoplasmic organelles. It functions as a tubular communica-
tion system through which substances can be transported
from one part of the cell to another. A large surface area and
multiple enzyme systems attached to the ER membranes also
provide the machinery for a major share of the metabolic
Endoplasmic
functions of the cell.
reticulum (ER)
Two forms of ER exist in cells: rough and smooth. Rough ER
is studded with ribosomes attached to specific binding sites on Transfer
vesicles Secretory Golgi
the membrane. The ribosomes, with the accompanying strand
granules apparatus
of mRNA, synthesize proteins. Proteins produced by the rough
ER are usually destined for incorporation into cell membranes ■FIGURE 1-3■Hormone synthesis and secretion.In hormone se-
cretion, the hormone is synthesized by the ribosomes attached to
and lysosomal enzymes or for exportation from the cell. The
the rough endoplasmic reticulum. It moves from the rough ER to
rough ER segregates these proteins from other components of
the Golgi complex, where it is stored in the form of secretory gran-
the cytoplasm and modifies their structure for a specific func-
ules. These leave the Golgi complex and are stored within the cyto-
tion. For example, the production of plasma protein by liver plasm until released from the cell in response to an appropriate
cells take place in the rough ER. All cells require a rough ER for signal.
the synthesis of lysosomal enzymes.
The smooth ER is free of ribosomes and is continuous with
the rough ER. It does not participate in protein synthesis; in- enzymes are acid hydrolases, which means that they require an
stead, its enzymes are involved in the synthesis of lipid mole- acid environment. The lysosomes provide this environment by
cules, regulation of intracellular calcium, and metabolism and maintaining a pH of approximately 5 in their interior. The pH
detoxification of certain hormones and drugs. It is the site of of the cytoplasm is approximately 7.2, which protects other cel-
lipid, lipoprotein, and steroid hormone synthesis. The sar- lular structures from this acidity.
coplasmic reticulum of skeletal and cardiac muscle cells is a Lysosomal enzymes are synthesized in the rough ER and
form of smooth ER. Calcium ions needed for muscle contrac- then transported to the Golgi apparatus, where they are bio-
tion are stored and released from cisternae of the sarcoplasmic chemically modified and packaged as lysosomes. Unlike those
reticulum. Smooth ER of the liver is involved in glycogen stor- of other organelles, the sizes and functions of lysosomes vary
age and metabolism of lipid-soluble drugs. considerably from one cell to another. The type of enzyme
packaged in the lysosome by the Golgi complex determines
Golgi Complex this diversity. Although enzymes in the secondary lysosomes
The Golgi apparatus, sometimes called the Golgi complex,con- can break down most proteins, carbohydrates, and lipids to
sists of stacks of thin, flattened vesicles or sacs. These Golgi their basic constituents, some materials remain undigested.
bodies are found near the nucleus and function in association These undigested materials may remain in the cytoplasm as
with the ER. Substances produced in the ER are carried to the residual bodiesor be extruded from the cell. In some long-lived
Golgi complex in small, membrane-covered transfer vesicles. cells, such as neurons and heart muscle cells, large quantities of
Many cells synthesize proteins that are larger than the active residual bodies accumulate as lipofuscin granules or age pig-
product. Insulin, for example, is synthesized as a large, inactive ment. Other indigestible pigments, such as inhaled carbon par-
proinsulin molecule that is cut apart to produce a smaller, ac- ticles and tattoo pigments, also accumulate and may persist in
tive insulin molecule within the Golgi complex of the beta cells residual bodies for decades.
of the pancreas. The Golgi complex modifies these substances Lysosomes play an important role in the normal metabo-
and packages them into secretory granules or vesicles. Enzymes lism of certain substances in the body. In some inherited dis-
destined for export from the cell are packaged in secretory vesi- eases known as lysosomal storage diseases,a specific lysosomal
cles. After appropriate signals, the secretory vesicles move out enzyme is absent or inactive, in which case the digestion of cer-
of the Golgi complex into the cytoplasm and fuse to the inner tain cellular substances does not occur. As a result, these sub-
side of the plasma membrane, where they release their contents stances accumulate in the cell. In Tay-Sachs disease, an auto-
into the extracellular fluid. Figure 1-3 is a diagram of the syn- somal recessive disorder, the lysosomal enzyme needed for
thesis and movement of a hormone through the rough ER and degrading the GM ganglioside found in nerve cell membranes
2
Golgi complex. In addition to its function in producing secre- is deficient (see Chapter 4). Although GM ganglioside accu-
2
tory granules, the Golgi complex is thought to produce large mulates in many tissues, such as the heart, liver, and spleen,
carbohydrate molecules that combine with proteins produced its accumulation in the nervous system and retina of the eye
by the rough ER to form glycoproteins. causes the most damage.
Smaller than lysosomes, spherical membrane-bound or-
Lysosomes and Peroxisomes ganelles called peroxisomes contain a special enzyme that de-
The lysosomes can be viewed as the digestive system of the cell. grades peroxides (e.g.,hydrogen peroxide). Peroxisomes func-
They consist of small, membrane-enclosed sacs containing hy- tion in the control of free radicals (see Chapter 2). Unless
drolytic enzymes capable of breaking down worn-out cell parts degraded, these highly unstable chemical compounds would
so they can be recycled. They also break down foreign sub- otherwise damage other cytoplasmic molecules. For example,
stances such as bacteria taken into the cell. All of the lysosomal catalase degrades toxic hydrogen peroxide molecules to water.
Chapter 1: Cell Structure and Function 5
Peroxisomes also contain the enzymes needed for breaking mitochondria. Although mitochondrial DNA directs the syn-
down very–long-chain fatty acids, which are ineffectively de- thesis of 13 of the proteins required for mitochondrial func-
graded by mitochondrial enzymes. In liver cells, peroxisomal tion, the DNA of the nucleus encodes the structural proteins
enzymes are involved in the formation of the bile acids. of the mitochondria and other proteins needed to carry out cel-
lular respiration.
Mitochondria Mitochondrial DNA is inherited matrilineally (i.e.,from the
The mitochondria are literally the “power plants” of the cell be- mother) and provides a basis for familial lineage studies.
cause they transform organic compounds into energy that is Mutations have been found in each of the mitochondrial
easily accessible to the cell. Energy is not made here but is ex- genes, and an understanding of the role of mitochondrial DNA
tracted from organic compounds. Mitochondria contain the in certain diseases is beginning to emerge. Most tissues in the
enzymes needed for capturing most of the energy in foodstuffs body depend to some extent on oxidative metabolism and can
and converting it into cellular energy. This multistep process re- therefore be affected by mitochondrial DNA mutations.
quires oxygen and is often referred to as aerobic metabolism.
Much of this energy is stored in the high-energy phosphate
The Cytoskeleton
bonds of compounds such as adenosine triphosphate (ATP),
which powers the various cellular activities. In addition to its organelles, the cytoplasm contains a network
Mitochondria are found close to the site of energy con- of microtubules, microfilaments, intermediate filaments, and
sumption in the cell (e.g.,near the myofibrils in muscle cells). thick filaments (Fig. 1-5). Because they control cell shape
The number of mitochondria in a given cell type is largely de- and movement, these structures are a major component of the
termined by the type of activity the cell performs and how structural elements called the cytoskeleton.
much energy is needed to undertake this activity. For example,
large increases in mitochondria have been observed in skeletal Microtubules
muscle that has been repeatedly stimulated to contract. The microtubules are slender tubular structures composed
The mitochondria are composed of two membranes: an of globular proteins called tubulin.Microtubules function in
outer membrane that encloses the periphery of the mitochon- many ways, including the development and maintenance of
drion and an inner membrane that forms shelflike projections,
calledcristae(Fig. 1-4). The outer and inner membranes form
two spaces: an outer intramembranous space and an inner ma-
Cell membrane
trix that is filled with a gel-like material. The outer membrane
Mitochondrion
is involved in lipid synthesis and fatty acid metabolism. The
Microtubule
inner membrane contains the respiratory chain enzymes and Rough
transport proteins needed for the synthesis of ATP. endoplasmic
Mitochondria contain their own DNA and ribosomes and reticulum
are self-replicating. The DNA is found in the mitochondrial
matrix and is distinct from the chromosomal DNA found in the
nucleus. Mitochondrial DNA, known as the “other human
genome,” is a double-stranded, circular molecule that encodes
the rRNA and tRNA required for intramitochrondial synthesis
of proteins needed for the energy-generating function of the
Outer limiting
membrane
Cristae
Matrix
space
Nucleus
Microfilament Ribosomes
Inner limiting
Intermediate
membrane
filaments
■FIGURE 1-4■Mitochondrion. The inner membrane forms ■FIGURE 1-5■Microtubes and microfilaments of the cell.The
transverse folds called cristae, where the enzymes needed for the microfilaments associate with the inner surface of the cell and aid
final step in adenosine triphosphate (ATP) production (i.e.,oxida- in cell motility. The microtubules form the cytoskeleton and main-
tive phosphorylation) are located. tain the position of the organelles.