Epithelial Tissue - Chapter 5 - PDF

Epithelial Tissue: Chapter 5 – Part 1 of 4 Dr. Claude E. Gagna, Professor New York Institute of Technology Department of Biological and Chemical Sciences © 2012 Pearson Education, Inc. Introduction...

Epithelial Tissue: Chapter 5 – Part 1 of 4 Dr. Claude E. Gagna, Professor New York Institute of Technology Department of Biological and Chemical Sciences © 2012 Pearson Education, Inc. Introduction Atoms make up molecules Molecules make up cells Cells make up tissues Tissues make up organs Organs make up organ systems Organ systems make up organisms © 2012 Pearson Education, Inc. Introduction This chapter concentrates on cells and tissues There are over 75 trillion cells in the body All cells can be placed into one of the four tissue categories Epithelial tissue Connective tissue Muscular tissue Neural tissue © 2012 Pearson Education, Inc.  Figures and Tables from Ross Textbook © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc.  Continue! © 2012 Pearson Education, Inc. Figure 3.1 An Orientation to the Tissues of the Body MOLECULES Combine EPITHELIA to form ATOMS Organic / Inorganic Cover exposed surfaces Line internal passageways Interact and chambers to form Produce glandular secretions See Figures 3.2 to 3.10 That EXTRACELLULAR secrete CELLS and MATERIAL regulate AND FLUIDS CONNECTIVE TISSUES Combine to form Fill internal spaces Provide structural support Store energy TISSUES See Figures 3.11 to 3.19, 3.21 with special functions Combine to form MUSCLE TISSUE Contracts to produce active ORGANS movement See Figure 3.22 with multiple functions Interact in NEURAL TISSUE Conducts electrical impulses ORGAN SYSTEMS Carries information See Figure 3.23 Chapters 4–27 © 2012 Pearson Education, Inc. Epithelial Tissue Epithelial Tissue Characteristics Cellularity Cells are bound close together No intercellular space Polarity Have an exposed apical surface Have an attached basal surface © 2012 Pearson Education, Inc. Epithelial Tissue Epithelial Tissue Characteristics (continued) Attachment Basal layer is attached to the basal lamina Avascularity Do not consist of blood vessels © 2012 Pearson Education, Inc. Epithelial Tissue Epithelial Tissue Characteristics (continued) Arranged in sheets Composed of one or more layers of cells Regeneration Cells are continuously replaced via cell reproduction © 2012 Pearson Education, Inc. Figure 3.2a Polarity of Epithelial Cells Cilia Microvilli Apical surface Golgi apparatus Nucleus Mitochondria Basal lamina Basolateral surfaces Many epithelial cells differ in internal organization along an axis between the apical surface and the basal lamina. The apical surface frequently bears microvilli; less often, it may have cilia or (very rarely) stereocilia. A single cell typically has only one type of process; cilia and microvilli are shown together to highlight their relative proportions. Tight junctions prevent movement of pathogens or diffusion of dissolved materials between the cells. Folds of plasmalemma near the base of the cell increase the surface area exposed to the basal lamina. Mitochondria are typically concentrated at the basolateral region, probably to provide energy for the cell’s transport activities. © 2012 Pearson Education, Inc. Epithelial Tissue Functions of Epithelial Tissue Provides physical protection Controls permeability Provides sensation Produces secretions © 2012 Pearson Education, Inc. Epithelial Tissue Specialization of Epithelial Cells Microvilli For absorption and secretion Stereocilia Long microvilli, commonly found in the inner ear Ciliated epithelium Moves substances over the apical surfaces of the cells © 2012 Pearson Education, Inc. Figure 3.2a Polarity of Epithelial Cells Cilia Microvilli Apical surface Golgi apparatus Nucleus Mitochondria Basal lamina Basolateral surfaces Many epithelial cells differ in internal organization along an axis between the apical surface and the basal lamina. The apical surface frequently bears microvilli; less often, it may have cilia or (very rarely) stereocilia. A single cell typically has only one type of process; cilia and microvilli are shown together to highlight their relative proportions. Tight junctions prevent movement of pathogens or diffusion of dissolved materials between the cells. Folds of plasmalemma near the base of the cell increase the surface area exposed to the basal lamina. Mitochondria are typically concentrated at the basolateral region, probably to provide energy for the cell’s transport activities. © 2012 Pearson Education, Inc. Figure 3.2b Polarity of Epithelial Cells Cilia Microvilli An SEM showing the surface of the epithelium that lines most of the respiratory tract. The small, bristly areas are microvilli found on the exposed surfaces of mucus-producing cells that are scattered among the ciliated epithelial cells. © 2012 Pearson Education, Inc. Epithelial Tissue Maintaining the Integrity of the Epithelium Three factors involved in maintenance Intercellular connections Attachment to the basal lamina Epithelial maintenance and renewal is self- perpetuated © 2012 Pearson Education, Inc. Figure 3.3a Epithelia and Basal Laminae Epithelial cells are usually packed together and interconnected by intercellular attachments. (See Figure 2.18) © 2012 Pearson Education, Inc. Figure 3.3b Epithelia and Basal Laminae CAMs Proteoglycans (intercellular cement) Basal Clear layer Plasmalemma lamina Dense layer Connective tissue At their basal surfaces, epithelia are attached to a basal lamina that forms the boundary between the epithelial cells and the underlying connective tissue. © 2012 Pearson Education, Inc. Figure 3.3c Epithelia and Basal Laminae TEM × 2600 Adjacent epithelial plasmalemmae are often interlocked. The TEM, magnified 2600 times, shows the degree of interlocking between columnar epithelial cells. © 2012 Pearson Education, Inc. Epithelial Tissue Classification of Epithelia Simple Epithelium has only one layer of cells Stratified Epithelium has two or more layers of cells © 2012 Pearson Education, Inc. Epithelial Tissue Epithelial Tissue Cells Squamous cells Thin, flat cells / “squished” nuclei Cuboidal cells Cube-shaped cells / centered, round nucleus Columnar cells Longer than they are wide / nucleus near the base Transitional cells Mixture of cells / nuclei appear to be scattered © 2012 Pearson Education, Inc. Epithelial Tissue Simple Squamous Epithelium Consists of very delicate cells Location Lining body cavities, the heart, the blood vessels Function Reduces friction Absorbs and secretes material © 2012 Pearson Education, Inc. Figure 3.4a Histology of Squamous Epithelia Simple Squamous Epithelium Locations: Mesothelia lining ventral body cavi- ties; endothelia lining heart and blood vessels; portions of kidney tubules (thin sections of nephron loops); inner lining of cornea; alveoli of lungs Functions: Reduces friction; controls vessel Connective permeability; performs tissue absorption and secretion Cytoplasm Nucleus Lining of peritoneal cavity LM × 238 A superficial view of the simple squamous epithelium (mesothelium) that lines the peritoneal cavity © 2012 Pearson Education, Inc. Epithelial Tissue Stratified Squamous Epithelium Location Surface of skin Lines: mouth, esophagus, anus, vagina Function Protection © 2012 Pearson Education, Inc. Figure 3.4b Histology of Squamous Epithelia Stratified Squamous Epithelium Locations: Surface of skin; lining of mouth, throat, esophagus, rectum, anus, and vagina Functions: Provides physical protection against abrasion, pathogens, and chemical attack Squamous superficial cells Stem cells Basal lamina Connective tissue Surface of tongue LM × 310 Sectional views of the stratified squamous epithelium that covers the tongue © 2012 Pearson Education, Inc. Epithelial Tissue Simple Cuboidal Epithelium Location Thyroid gland, ducts, kidney tubules Function Secretion, absorption © 2012 Pearson Education, Inc. Figure 3.5a Histology of Cuboidal Epithelia Simple Cuboidal Epithelium LOCATIONS: Glands; ducts; portions of kidney tubules; thyroid gland FUNCTIONS: Limited protection, secretion, absorption Kidney tubule Connective tissue Nucleus Cuboidal cells Basal lamina LM × 1400 A section through the simple cuboidal epithelium lining a kidney tubule. The diagrammatic view emphasizes structural details that permit the classification of an epithelium as cuboidal. © 2012 Pearson Education, Inc. Epithelial Tissue Stratified Cuboidal Epithelium Location Ducts of sweat glands Function Secretion, absorption © 2012 Pearson Education, Inc. Figure 3.5b Histology of Cuboidal Epithelia Stratified Cuboidal Epithelium LOCATIONS: Lining of some ducts (rare) FUNCTIONS: Protection, secretion, absorption Lumen of duct Stratified cuboidal cells Basal lamina Nucleus Connective tissue Sweat gland duct LM × 1413 A sectional view of the stratified cuboidal epithelium lining a sweat gland duct in the skin © 2012 Pearson Education, Inc. Epithelial Tissue Simple Columnar Epithelium Location Lining: stomach, intestines, uterine tubes Function Secretion, absorption, protection © 2012 Pearson Education, Inc. Figure 3.6a Histology of Columnar Epithelia Simple Columnar Epithelium LOCATIONS: Lining of stomach, intestine, gallbladder, uterine tubes, and collecting ducts of kidneys FUNCTIONS: Protection, secretion, absorption Microvilli Cytoplasm Nucleus Basal lamina Loose connective tissue LM × 350 Intestinal lining A light micrograph showing the characteristics of simple columnar epithelium. In the diagrammatic sketch, note the relationships between the height and width of each cell; the relative size, shape, and location of nuclei; and the distance between adjacent nuclei. Contrast these observations with the corresponding characteristics of simple cuboidal epithelia. © 2012 Pearson Education, Inc. Epithelial Tissue Stratified Columnar Epithelium Location Pharynx, epiglottis, mammary glands, salivary glands Function Protection © 2012 Pearson Education, Inc. Figure 3.6b Histology of Columnar Epithelia Stratified Columnar Epithelium LOCATIONS: Small areas of the pharynx, epiglottis, anus, mammary gland, salivary gland ducts, and urethra FUNCTION: Protection Loose connective tissue Deeper basal cells Superficial columnar cells Lumen Lumen Cytoplasm Nuclei Basal lamina Salivary gland duct LM × 175 A stratified columnar epithelium is sometimes found along large ducts, such as this salivary gland duct. Note the overall height of the epithelium and the location and orientation of the nuclei. © 2012 Pearson Education, Inc. Epithelial Tissue Pseudostratified Ciliated Columnar Epithelium Nucleus situated at different levels Location Nasal cavity, trachea, bronchi Function Protection, secretion © 2012 Pearson Education, Inc. Figure 3.7a Histology of Pseudostratified Ciliated Columnar and Transitional Epithelia Pseudostratified ciliated columnar epithelium LOCATIONS: Lining of FUNCTIONS: Protection, nasal cavity, trachea, and secretion bronchi; portions of male reproductive tract Trachea Cilia Cytoplasm Nuclei Basal lamina Loose connective tissue LM × 350 Pseudostratified ciliated columnar epithelium. The pseudostratified, ciliated, columnar epithelium of the respiratory tract. Note the uneven layering of the nuclei. © 2012 Pearson Education, Inc. Epithelial Tissue Transitional Epithelium Consists of many layers Consists of a combination of cuboidal and “odd” shaped cells Location Urinary bladder Function Ability to stretch extensively © 2012 Pearson Education, Inc. Figure 3.7b Histology of Pseudostratified Ciliated Columnar and Transitional Epithelia Transitional epithelium LOCATIONS: Urinary bladder; renal pelvis; ureters FUNCTIONS: Permits expansion and recoil after stretching Epithelium (relaxed) Basal lamina Relaxed bladder Connective tissue and smooth muscle layers LM × 450 Epithelium (stretched) Basal lamina Connective tissue and Stretched bladder smooth muscle layers LM × 450 Transitional epithelium. A sectional view of the transitional epithelium lining the urinary bladder. The cells from an empty bladder are in the relaxed state, while those lining a full urinary bladder show the effects of stretching on the arrangement of cells in the epithelium. © 2012 Pearson Education, Inc. Epithelial Tissue Glandular Epithelia Many epithelia are mixed with gland cells Types of glands Serous glands: secrete watery fluids rich in enzymes Mucous glands: secrete glycoproteins (mucins) that absorb water to produce mucus Mixed exocrine glands: contain both serous and mucous secretions © 2012 Pearson Education, Inc. Epithelial Tissue Glandular Epithelia (continued) Endocrine glands Secretions enter into the blood or lymph Exocrine glands Secretions travel through ducts to the epithelial surface © 2012 Pearson Education, Inc. Epithelial Tissue Glandular Epithelia Classification Simple glands Do not have branching ducts Compound glands Have various branching ducts © 2012 Pearson Education, Inc. Figure 3.9 A Structural Classification of Simple and Compound Exocrine Glands (Part 1 of 2) Simple Glands Duct Gland cells SIMPLE SIMPLE COILED SIMPLE BRANCHED SIMPLE ALVEOLAR SIMPLE BRANCHED TUBULAR TUBULAR TUBULAR (ACINAR) ALVEOLAR Examples: Examples: Examples: Examples: Examples: Intestinal glands Merocrine sweat Gastric glands Not found in adult; a stage Sebaceous (oil) glands Mucous glands of in development of simple glands esophagus, tongue, branched glands duodenum Glands whose glandular cells form tubes are Those that form blind pockets are alveolar or tubular; the tubes may be straight or coiled. acinar. © 2012 Pearson Education, Inc. Figure 3.9 A Structural Classification of Simple and Compound Exocrine Glands (Part 2 of 2) Compound Glands COMPOUND TUBULAR COMPOUND ALVEOLAR (ACINAR) COMPOUND TUBULOALVEOLAR Examples: Examples: Examples: Mucous glands (in mouth) Mammary glands Salivary glands Bulbo-urethral glands (in Glands of respiratory male reproductive system) passages Testes (seminiferous tubules) Pancreas © 2012 Pearson Education, Inc. Epithelial Tissue Glandular Epithelia Modes of Secretion Merocrine secretion Apocrine secretion Holocrine secretion © 2012 Pearson Education, Inc. Epithelial Tissue Modes of Secretion Merocrine Secretion Secretions released through exocytosis Examples: Goblet cells of the trachea Cells in the axilla region regarding sweat production © 2012 Pearson Education, Inc. Figure 3.10a Mechanisms of Glandular Secretion Secretory Salivary vesicle gland Golgi apparatus Nucleus TEM × 2300 In merocrine secretion, secretory vesicles are discharged at the surface of the gland cell through exocytosis. © 2012 Pearson Education, Inc. Epithelial Tissue Modes of Secretion Apocrine Secretion Secretions released via the loss of cytoplasm Example: Cells of the mammary glands for milk secretion © 2012 Pearson Education, Inc. Figure 3.10b Mechanisms of Glandular Secretion Golgi apparatus Breaks down Mammary gland Secretion Regrowth Apocrine secretion involves the loss of cytoplasm. Inclusions, secretory vesicles, and other cytoplasmic components are shed at the apical surface of the cell. The gland cell then undergoes a period of growth and repair before releasing additional secretions. © 2012 Pearson Education, Inc. Epithelial Tissue Modes of Secretion Holocrine Secretion Secretions released upon bursting of the glandular cells Example: Cells of the sebaceous glands © 2012 Pearson Education, Inc. Figure 3.10c Mechanisms of Glandular Secretion Cells burst, releasing cytoplasmic contents Cells produce secretion, increasing in size Cell division replaces lost cells Stem cell Hair Holocrine secretion occurs as superficial gland Sebaceous cells break apart. Continued secretion involves the gland replacement of these cells through the mitotic Hair follicle division of underlying stem cells. © 2012 Pearson Education, Inc.