Essentials of Oral Histology and Embryology: A Clinical Approach, 3e

244 Pages·2005·146.54 MB·English

by  James K. Avery

ESSENTIALS OF
ORAL HISTOLOGY
AND EMBRYOLOGY

A Clinical Approach
THIRD EDITION
JAMES K. AVERY, DDS, PhD
Professor Emeritus ofDentistry, School ofDentistry
Professor Emeritus of Anatomy, Medical School

University of Michigan

Ann Arbor, Michigan

DANIElj. CHIEGO,jR., MS, PhD
Associate Professor, School ofDentistry
Department of Cariology, Restorative Sciences and Endodontics

University of Michigan

Ann Arbor, Michigan

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ESSENTIALS OF ORAL HISTOLOGY AND EMBRYOLOGY: ISBN 9780-323-03339-8
A CUJ\TICAL APPROACH ISBN 0-323-03339-3
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PREFACE

T
he central purpose ofthis textbook is to educate embryology, and oral anatomy. The third edition now
students in the dental professions with an expla­ includes a list of Learning Objectives and Key Terms at
nation of the structures related to histology of the beginning of each chapter. Learning Objectives list
the masticatory apparatus. The fields of head and neck the main ideas discussed in each chapter and what the
embryology and histology are of utmost importance in student can be expected to know by reading its content,
the study ofdental practice and dental hygiene. Oral his­ thus allowing readers and instructors to set goals for
tology is paramount to the understanding of dental comprehension and engage in more directed learning at
pathology, so connecting these fields of study provides the outset of the chapter. The Key Terms are listed
an explanation for the cause-and-effect nature ofdental alphabetically and are then bolded where they are dis­
conditions and resulting treatment choices. To under­ cussed in the text, where the reader will find a contextual
take the best treatment for the patient, one must first explanation of that term. The Glossary at the end of the
understand what is normal to gain better awareness of book provides definitions for these key terms that will
the abnormal. allow students to use them in their clinical vocabulary
The third edition of Essentials of Oral Histolog;y and with confidence.
Embryolog;y: A Clinical Approach is therefore designed as Special features such as the Consider the Patient boxes
the basic science information text to help in the compre­ and Clinical Comment boxes are continued in this edition.
hension of the microscopic anatomy of the oral and Consider the Patient boxes demonstrate the applicability of
facial tissues. Chapter 2 of this edition, "Structure and the book's concepts by presenting the reader with situa­
Function of Cells, Tissues, and Organs," has been espe­ tions and patient questions relevant to the current chap­
cially revised to provide more essential information ter discussion that could occur in clinical practice. Each
about these building blocks ofthe body's systems. Other box has a coordinating Discussion box at the end of the
areas of the book, including Suggested Reading and chapter that provides common answers to the questions
Self-Evaluation Questions at the end of each chapter, or possible recommendations and explanations for cer­
have been updated with new information. As with previ­ tain conditions, thereby preparing students for how they
ous editions ofthe text, an effort has been made to posi­ would respond to similar situations in real life and
tion explanatory diagrams and illustrations as close as opening the door to further discussion ofother possible
possible to their accompanying textual descriptions. In solutions. Additional Clinical Comment boxes placed
addition, most illustrations are now presented in color throughout this edition offer clinical tips and notes of
to enable students to better correlate structure with interest pertaining to chapter content.
function by observing histology as they would view it in The most drastic change in this third edition is the
reality. We believe that the use ofso many detailed pho­ inclusion of an Evolve website that accompanies and
tographs, drawings, and diagrams will allow a greater enhances the textual material. This website, available at
ease in understanding the numerous theoretical and the URL listed on the inside front cover of this book,
clinical concepts presented here. contains multiple online learning resources to aid the
Another key to learning the content of this text effec­ student and instructor alike in their efforts to cover
tively is possessing a thorough grasp of the sometimes the content of the book. The weblinks listed connect
complicated terminology used in the fields of histology, readers to up-to-date articles and current information
v
TABLE OF CONTENTS

1 Development and Structure of Cells and 10 Cementum, 137
Tissues, 1
11 Periodontium: Periodontal Ligament, 145
2 Structure and Function of Cells, Tissues, and
12 Periodontium: Alveolar Process and
Organs, 19
Cementum, 157
3 Development of the Oral Facial Region, 37
13 Temporomandibular Joint, 167
4 Development of the Face and Palate, 51
14 Oral Mucosa, 177
5 Development of Teeth, 63
15 Salivary Glands and Tonsils, 195
6 Eruption and Shedding of the Teeth, 81
16 Biofilms, 207
7 Enamel, 97
8 Dentin, 107 Glossary, 217
9 Dental Pulp, 121
ix
DEVELOPMENT AND

STRUCTURE OF CELLS

AND TISSUES
CHAPTER OUTLINE
Overview Induction
Brain and spinal cord
Cell Structure and Function Gene regulation
Cranial nerves
Cell Nucleus Cell Differentiation
Connective Tissue
Cell Cytoplasm Periods ofPrenatal
Connective tissue proper
Cell Division Development Blood and lymphatic tissues
Cell Cycle Ovarian Cycle, Fertilization, Cartilage and bone
Mitosis Implantation, and Muscle
Meiosis Development of the Cardiovascular system
Apoptosis Embryonic Disk Developmental abnormalities
Origin ofHuman Tissue Development ofHuman Tissues Self-Evaluation Questions
Epithelial Mesenchymal Epithelial Tissue Consider the Patient Discussion
Interaction Nervous System Suggested Reading
LEARNING OBJECTIVES
After reading this chapter the student will be able to:
• describe the cell and how it divides
• discuss the origin of tissue, the ovarian cycle, and development of the embryonic disk
• describe the various tissues of the human body and some of the adverse factors such as environmental stress and
hereditary and dietary factors that may affect development of these tissues
KEY TERMS
Absorption Assimilation Centrioles
Agranulocytes Astral rays/ asters Centromere
Anaphase Basophils Cerebellum
Angioblasts Blastocyst Cerebral hemispheres
Angiogenic clusters Cartilage Chondroblasts
Appositional Cell cycle Chromatids
2 ESSENTIALS OF ORAL HISTOLOGY AND EMBRYOLOGY
KEY TERMS-cont'd
Chromosomes Gastrointestinal tract Myotome
Conductivity Gene expression Neural plate, tube
Cytoplasm Genetic mechanisms Neuroblasts
Cytosol Golgi apparatus, complex Neurons
Deoxyribonucleic acid (DNA) Granulocytes Neutrophils
Dermatome Growth Nuclear envelope
Dermis Growth factors Nuclear pores
Ectodermal Hemoglobin Nucleolus
Elastic or fibrous cartilage Hyaline cartilage Nucleus
Embryonic disk Implantation Organizer
Embryonic period Induction Osteoblasts
Endochondral bone development Intercalated disks Plasma
Endodermal Intercellular material Plasma membrane.
Endometrium Interstitial Pons
Endoplasmic reticulum (ER) Interstitial growth Proliferative period
Eosinophils Intramembranous bone formation Prophase
Epidermis Irritability Reproduction
Epiphyseal line Leukocytes Respiration
Epithelium Lymphatic system Ribonucleic acid (RNA)
Equatorial plate Lymphocytes S phase
Eryth rocytes Lysosomes Sclerotome
Excretion Melanocytes Smooth muscle cells
Fetal period Mesenchymal cells Somites
Fibroblasts Mesodermal Spindle fibers
Fluid Metaphase Striated voluntary muscles
Foramen ovale Metaphysis Telophase
Forebrain, midbrain , and hindbrain Microtubules Umbilical system
Frontal, temporal, and occipital Mitochondria Visceral mesoderm
lobes Monocytes Vitelline vascular system
GI phase, G2 phase Morula Zygote
OVERVIEW
of the mesodermal components involving connective
The smallest unit ofstructure in the human body is the tissues of the body, such as fibrous tissue, three types
cell, composed of a nucleus and cytoplasm. The nucleus of cartilage, two types of bone, three kinds of muscles,
contains deoxyribonucleic acid (DNA) and ribonucleic and the cardiovascular system. The reader will better
acid (RNA), the fundamental strucrures of life. The comprehend the origin, development, organization,
cytoplasm functions in absorption and cell duplication, and structure of the various cells and tissues of the
in which organelles perform specific actions. The cell human body.
cycle is the time required for the DNA to duplicate
before mitosis. This chapter discusses the four stages
CELL STRUCTURE AND FUNCTION
of mitosis: prophase, metaphase, anaphase, and telo­
phase. Also described are the three periods of prenatal The human body is composed ofcells, intercellular sub­
development: proliferative, embryonic, and fetal. The stance (the products ofthese cells), and fluid that bathes
fertilization of the ovum in the distal uterine tube, these tissues. Cells are the smallest living units capable
zygote migration, and the zygote's implantation in the of independent existence. They carry out the vital
uterine wall are discussed. In addition, the origin of processes of absorption, assimilation, respiration,
human tissues-ectoderm, mesoderm, and endoderm-is irritability, conductivity, growth, reproduction, and
presented, followed by the differentiation oftissue types, excretion. Cells vary in size, shape, structure, and func­
such as those of ectodermal origin, epithelium and skin tion. Regardless of function, each cell has a number
with its derivatives, and the central and peripheral nerv­ of characteristics in common with other cells, such as
ous systems. This chapter also delineates development cytoplasm and a nucleus, which contains a nucleolus.
Chapter. DEVELOPMENT AND STRUCTURE OF CELLS AND TISSUES 3
However, some cell characteristics are related to func­ ovoid, depending on the cell's shape. Ordinarily a cell
tion. A cell on the surface ofthe skin, for example, serves has a single nucleus; however, it may be binucleate, as are
best as a thin, flattened disk, whereas a respiratory cell cardiac muscle cells or parenchymal liver cells, or multi­
functions best as a cuboidal or columnar cell to facilitate nucleate, as are ostebclasts and skeletal muscle cells. The
adsorption with mobile cilia to move fluid from the nucleus is important in the production of DNA and
lung to the oropharynx. Surrounding each cell is the RNA. DNA contains the genetic information in the cell,
intercellular material that provides the cell with nutri­ and RNA carries information from the DNA to sites of
tion, takes up waste products, and provides the body actual protein synthesis, which are located in the cell
with form. It may be as soft as loose connective tissue or cytoplasm. The nucleus is bound by a membrane, the
as hard as bone cartilage or teeth. Fluid, the third nuclear envelope, which has openings at the nuclear
component of the body, is the blood and lymph that pores. This envelope is composed of two phospholipids
travel throughout the body in vessels or the tissue fluid layers similar to the plasma membrane of the cell. The
that bathes each cell and fiber of the body. pores are associated with the endoplasmic reticulum
that forms at the end of each cell division. The nucleus
Cell Nucleus
contains from one to four nucleoli, which are round,
A nucleus is found in all cells except mature red blood dense bodies constituting the RNA contained in the
cells and blood platelets. The nucleus is usually round to nucleus. Nucleoli have no limiting membrane (Fig. 1-1).
Tight junction
Desmosome
Plasma
membrane
Rough
endoplasmic
reticulum
Golgi complex
Centrioles
Mitochondria
Receptor
Gap junction
Lysosome
Nuclear pore
Filaments and Nucleolus
free glycogen
Lipid droplets
Polyribosomes
Fig. 1-1 Nucleus, rough surface endoplasmic reticulum, mitochondria, Golgi apparatus, centrioles, and gap junctions as
viewed by electron microscopy. Cells communicate with each other to regulate organization, growth, and development.
4 EsSENTIALS OF ORAL HISTOLOGY AND EMBRYOLOGY
Cell Cytoplasm
Microtubules are small tubular strucrures in the
Cytoplasm contains structures necessary for adsorption cytoplasm that are composed of the protein tubulin.
and for creation ofcell products. The cytosol is the part These structures may appear as singles, as doublets, or as
of the cytoplasm that contains the organelles and triplets. They probably function as structural and force­
solutes. The cytosol uses the raw materials brought into generating elements and relate to cilia (motile cell
the cell to produce energy. It also functions in the excre­ processes) and to centrioles in relation to mitosis. They
tion of waste products. These functions are carried out have cytoskeletal functions in maintaining cell shape.
by the endoplasmic reticulum (ER)-parallel mem­ Centrioles are short cylinders appearing near the
brane-bound cavities in the cytoplasm that contain nucleus. Their walls are composed of nine triplets of
newly acquired and synthesized protein. Two types of microtubules. Centrioles are microtubule-generating
ER, smooth surfaced and granular or rough surfaced, centers and are important in mitosis, self-replicating
can be found in the same cell. Rough-surfaced ER is before mitosis begins.
caused by ribosomes on the surface ofthe reticulum and Surrounding the cell is the plasma membrane or
is the site at which protein production is initiated. plasmalemma, which envelops the cell and provides a
Proteins are vital to the cell's metabolic processes, and selective barrier that regulates transport of substances
each type of protein is composed ofa number ofdiffer­ into and out of the cell. All membranes are composed
ent amino acids linked in a specific sequence. Amino mainly of lipids and proteins with a small amount of
acids form protein-containing groups, which, in tum, carbohydrates. The plasma membrane also receives sig­
form acids or bases. nals from hormones and neurotransmitters. In addition,
Ribosomes are particles that translate genetic codes cells contain proteins, lipids, or fatty substances that
for proteins and activate mechanisms for their produc­ provide energy in the cell and are important compo­
tion. They can be found as separate particles in the nents ofcell membranes and permeability. Carbohydrates
cytoplasm, clustered, or attached to the ER membranes. are also important in cells as the most available energy
Ribosomes are nonspecific as to what type of protein component in the body. These carbohydrates may exist
they synthesize. The type is dependent on the messenger as polysaccharide-protein complexes, glycoprotein com­
RNA (mRNA), which carries the message directly from plexes, glycoproteins, and glycolipids. Carbohydrate
the DNA ofthe nucleus to the RNA in the ER. This mol­ compounds are important in cell function and for
ecule attaches to the ribosomes and gives orders about development ofcell products, such as supportive tissues
the formation of the amino acids. and body lubricants.
The ER transports substances in the cytoplasm. Genetic mechanisms help a cell to develop and
The ER is connected to the Golgi apparatus via small maintain a high degree oforder. The ability is dependent
vesicles. The Goigi apparatus or complex helps sort, on the genetic information that is expressed within the
condense, package, and deliver proteins arriving from cell. The basic genetic processes in the cell are RNA and
the ER. The Golgi apparatus is composed of cisternae protein synthesis, DNA repair, and replication and
(flat plates) or saccules, small vesicles, and large genetic recombination. These processes produce type
vacuoles. From here the secretory vesicles move or flow proteins and nucleic acids ofa cell. These genetic events
to the cell surface, where they fuse with the cell mem­ are relatively simple compared with other cell processes.
brane and the plasmalemma and release their contents
by exocytosis.
CEll DIVISION
Lysosomes are small, membrane-bound bodies that
contain a variety ofacid hydrolase and digestive enzymes
Cell Cycle
to help break down substances both inside and outside
the cell. They are in all cells except red blood cells but are Cell division is a continuous series of discrete steps by
prominent in macrophages and leukocytes. which the cell component divides. This function is
Mitochondria are membrane-bound organelles that related to the need for growth or replacement of tissues
lie free in the cytoplasm and are present in all cells. They and is partly dependent on the length of the cell's life.
are important in generating energy, are a major source of Continually renewing cells line the gastrointestinal tract
adenosine triphosphate (ATP), and therefore are the site and compose the epidermis and the bone marrow. A sec­
ofmany metabolic reactions. These organelles appear as ond type ofcell is part ofan expanding population-the
spheres, rods, ovoids, or threadlike bodies. Usually the cells ofthe kidney, liver, and some glands. The third type
inner layer of their trilaminar bounding membrane ofcell does not undergo cell division or DNA synthesis.
inflects to form transverse-appearing plates, the cristae An example is the neurons of the adult nervous system.
(see Fig. 1-1). Mitochondria lie adjacent to the area that For a somatic cell to undergo cell division, it must pass
requires their energy production. through a cell cycle, which ensures time for DNA genetic