Chapter 4-3.pdf

Because learning changes everything.® Chapter 04 Tissue Level of Organization Human Anatomy SIXTH EDITION McKinley O’Loughlin Pennefather-O’Brien © 2021 McGraw Hill. All rights reserved. Aut...

Because learning changes everything.® Chapter 04 Tissue Level of Organization Human Anatomy SIXTH EDITION McKinley O’Loughlin Pennefather-O’Brien © 2021 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.  Introduction A tissue is a group of similar cells and extracellular products that perform a common function Histology is the study of tissues The extracellular matrix is produced by the cells and surrounds them Generally composed of water, protein fibers, dissolved molecules Composition, volume, and consistency are different across tissues Four types of tissues in the body: 1. Epithelial tissue 2. Connective tissue 3. Muscle tissue 4. Nervous tissue © McGraw Hill 2  Epithelial Tissue Epithelial tissue lines every body surface and all body cavities Organs are lined on the outside and inside by epithelial tissue The majority of glands are derived from epithelial tissue Epithelial tissue possesses little to no extracellular matrix, and no blood vessels © McGraw Hill 3  Characteristics of Epithelial Tissue Cellularity: composed almost entirely of cells bound by intercellular junctions; little extracellular matrix between cells Polarity: epithelia have an apical surface, lateral surface, and a basal surface Apical surface is exposed and may have modifications (for example, microvilli) Lateral surfaces have intercellular junctions Basal surface is attached to connective tissue underneath it © McGraw Hill 4  Characteristics of Epithelial Tissue Attachment to a basement membrane: Basal surface attaches to basement membrane, which is a structure produced by both epithelial and neighboring connective tissues Avascularity: Epithelial tissues lack blood vessels; receive nutrients by diffusion from underlying tissues Innervation: Epithelia are richly innervated to detect changes in environment (externally or internally) High regeneration capacity: Because exposed apical surface is frequently damaged, epithelial cells are quickly replaced © McGraw Hill 5  Polarity in an Epithelium Figure 4.1a © McGraw Hill 6  Functions of Epithelial Tissue Physical protection: defend against dehydration and abrasion, as well as physical, chemical, and biological agents Selective permeability: regulate passage of molecules in or out of certain regions of the body Secretion: secrete substances for use in the body (for example, hormone) or for elimination from the body (for example, sweat) Sensation: possess nerve endings that can detect light, taste, sound, smell, and hearing © McGraw Hill 7  Specialized Structures of Epithelial Tissue The basement membrane is a specialized structure of an epithelium Found between epithelium and underlying connective tissue Composed of proteins and carbohydrates in layers. Functions of basement membrane: Provides physical support Anchors epithelial tissue Acts as a barrier regulating passage of large molecules between epithelium and connective tissue © McGraw Hill 8  Specialized Structures of Epithelial Tissue 2 Epithelial cells are strongly bound to each other on their lateral surfaces by membrane specializations called intercellular junctions There are several types of these junctions: Tight junctions Adhering junctions Desmosomes Gap junctions © McGraw Hill 9  Intercellular Junctions in an Epithelium Figure 4.1b © McGraw Hill 10  Tight Junctions Tight junctions encircle epithelial cells near their apical surface and completely attach each cell to its neighbor Prevent molecules from traveling between epithelial cells Ensures molecules must go through epithelial cells rather than in between them, as a form of selective permeability “Gatekeepers” between an external and internal environment © McGraw Hill 11  Adhering Junctions Adhering junctions are formed completely around the cell deep to the tight junction Microfilaments are anchored to membrane, and membrane proteins link cells together Adhering junctions help stabilize the apical surface of the epithelial cell © McGraw Hill 12  Desmosomes Desmosomes are junctions that appear at locations of mechanical stress between cells Like a button or snap between adjacent cells Consist of a thickened protein plaque on each of the apposed cell membranes with a fine network of proteins spanning the intercellular space between the plaques On the cytoplasmic side, intermediate filaments attach to the plaques and provide support and stability Some basal epithelial cells have hemidesmosomes anchoring them to basement membrane © McGraw Hill 13  Gap Junctions Gap junctions span the intercellular space between neighboring cells A connexon is a group of membrane proteins that forms a pore The fluid-filled pore connects the cytoplasms of the two cells Allow adjacent cells to communicate with each other by the flow of ions and small molecules © McGraw Hill 14  Classification of Epithelial Tissue Many different types of epithelial tissues Epithelia are classified according to two criteria: Number of layers of cells Shape of the cells at the apical surface Each epithelium has a two-part name, reflecting its classification First part reflects the number of layers of cells Second part reflects the shape of the apical cells © McGraw Hill 15  Classification by Number of Cell Layers Simple epithelium: consists of a single layer of cells All cells have an apical surface and attach to the basement membrane Stratified epithelium: consist of two or more layers of cells Not all cells have an apical surface nor do all cells attach to the basement membrane Pseudostratified epithelium: appears to have multiple layers, but all cells attach to the basement membrane A subtype of simple epithelium © McGraw Hill 16  Epithelium Classified by Layers Figure 4.2a © McGraw Hill 17  Classification by Cell Shape Squamous: flat, wide, and somewhat irregular in shape Cuboidal: about the same size on all sides; nucleus is usually centrally located Columnar: taller than they are wide; nucleus is oval and located in basal region of the cell Transitional: cells change shape depending on degree of stretch of epithelium Polyhedral (“many-sided”) in a relaxed state Squamous when stretched For example, found lining the urinary bladder © McGraw Hill 18  Epithelium Classified by Shapes Figure 4.2b © McGraw Hill 19  Organization and Relationship of Epithelia Types Figure 4.3 © McGraw Hill 20  Simple Squamous Epithelium Single layer of flat cells Allows for rapid exchange Examples: lining the lung air sacs (alveoli), lining of blood vessels When lining blood and lymphatic vessels, the epithelium is called an endothelium The simple squamous epithelium of a serous membrane is called a mesothelium © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 21  Simple Cuboidal Epithelium Single layer of cells as tall as they are wide Allows for absorption, secretion Examples: kidney tubules, ducts of exocrine glands © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 22  Simple Columnar Epithelium Single layer of tall, narrow cells Allows for absorption and secretion Ciliated and nonciliated forms Nonciliated form may have microvilli (brush border) and goblet cells (secrete mucin) Nonciliated examples: most of digestive tract, from stomach to anal canal Ciliated example: uterine tube © McGraw Hill 23  Simple Columnar Epithelia Nonciliated Ciliated Access the text alternative for slide images. © McGraw Hill (Left): ©McGraw-Hill Education/Al Telser, photographer; (Right): ©Victor P. Eroschenko 24  Pseudostratified Columnar Epithelium Single layer of narrow cells with varying heights Appears stratified but is simple All cells touch basement membrane, but not all reach the apical surface Ciliated and nonciliated forms Functions in protection; ciliated form secretes mucin, moves mucus Example: respiratory tract lining Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 25  Stratified Squamous Epithelium Multiple layers; only the deepest layer of cells contacts the basement membrane Apical cells are squamous (flat) and deeper layers are cuboidal or polyhedral Functions in protection Keratinized and nonkeratinized varieties Keratinized stratified squamous epithelium: apical cells are dead, flat, and filled with the tough protein keratin; found in the epidermis of the skin Nonkeratinized stratified squamous epithelium: apical cells are flat, moist, and alive; found in the esophagus and lining of vagina © McGraw Hill 26  Stratified Squamous Epithelia Keratinized Nonkeratinized Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 27  Stratified Cuboidal Epithelium Multiple layers of cells, apical cells are as tall as they are wide Protection, secretion, support the walls of some ducts Example: lining of sweat gland duct Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 28  Stratified Columnar Epithelium Multiple layers of cells, apical cells are elongated Protection, support, and secretion Example: part of male urethra, ducts of some salivary glands Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 29  Transitional Epithelium Multiple layers, apical cell shape varies depending on degree of stretch Polyhedral when resting, squamous when stretched Some binucleated cells Example: lining of urinary tract Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 30  Glands Glands are individual cells or multicellular organs composed primarily of epithelial tissue that perform a secretory function Produce mucin, hormones, enzymes, waste products Glands fall into two categories: 1. Endocrine glands do not possess ducts; secrete hormones (chemical messengers) directly into interstitial fluid or bloodstream 2. Exocrine glands possess ducts and their cells secrete products into their ducts © McGraw Hill 31  Exocrine Gland Structure Goblet cells are unicellular exocrine glands typically found in simple columnar and pseudostratified epithelia Multicellular exocrine glands are often enclosed in a fibrous capsule Deep to the capsule, septa divide the gland into lobes Microscopic lobules contain secretory acini and ducts Glands contain a connective tissue network (stroma) that supports and organizes the parenchyma (functional cells that produce the secretion) © McGraw Hill 32  Goblet Cell: A Unicellular Exocrine Gland Figure 4.4 Access the text alternative for slide images. © McGraw Hill (a) EM Research Services/Newcastle University 33  General Structure of Multicellular Exocrine Glands Figure 4.5 Access the text alternative for slide images. © McGraw Hill 34  Classification of Exocrine Glands 1 Glands classified by: 1. Form and structure 2. Type of secretion 3. Method of secretion Structural categorization depends on the complexity of the duct and the shape of the secretory portion Duct type distinguishes simple from compound glands Secretory portion can be tubular, acinar or tubuloacinar Gland secretion types are serous, mucous, or mixed Serous glands produce watery fluids (such as sweat) Mucous glands secrete mucin Mixed glands produce a mixture of watery and mucoid secretions (for example, salivary glands under oral cavity) © McGraw Hill 35  Structural Classification of Multicellular Exocrine Glands Figure 4.6 Access the text alternative for slide images. © McGraw Hill 36  Classification of Exocrine Glands 2 Secretion methods Merocrine: secrete products from vesicles via exocytosis Apocrine: product stored in apical part of cell that pinches off Holocrine: cell accumulates product, then disintegrates Figure 4.7 Access the text alternative for slide images. © McGraw Hill 37  Connective Tissue Connective tissue is the most diverse, abundant, widely distributed, and structurally varied of the four main tissue types It is the “glue” of the body Includes blood, tendons, ligaments, fat, bones, cartilage © McGraw Hill 38  Characteristics of Connective Tissue All connective tissues contain cells, protein fibers, and ground substance Cells: different cells in different types of connective tissue Examples include fibroblasts, osteocytes, and adipocytes Protein fibers: elastic fibers, collagen, reticular fibers Ground substance: a mixture of proteins and carbohydrates with variable amounts of salts and water Protein fibers and ground substance comprise the extracellular matrix © McGraw Hill 39  Connective Tissue Components and Organization Figure 4.8 Access the text alternative for slide images. © McGraw Hill 40  Functions of Connective Tissue Physical protection—for example, bones and fat protecting the organs they surround Support and structural framework—for example, bones are the framework for the body; cartilage supports the trachea Binding of structures—for example, ligaments connect bones Storage—for example, adipose stores fat Transport—for example, blood carries nutrients, wastes Immune protection—leukocytes (white blood cells) patrol many types of connective tissue © McGraw Hill 41  Development of Connective Tissue Arises from mesoderm Two types of embryonic CT: 1. Mesenchyme: the source of all adult connective tissue 2. Mucous connective tissue: found in umbilical cord © McGraw Hill 42  Types of Embryonic Connective Tissue Access the text alternative for slide images. © McGraw Hill (Left): ©McGraw-Hill Education/Al Telser, photographer; (Right): ©Ed Reschke 43  Classification of Connective Tissue Types present after birth can be classified into three broad categories: 1. Connective tissue proper 2. Supporting connective tissue 3. Fluid connective tissue © McGraw Hill 44  Connective Tissue Classification Figure 4.9 Access the text alternative for slide images. © McGraw Hill 45  Connective Tissue Proper Connective tissue proper includes multiple subtypes Subtypes vary in number and types of cell and in properties of extracellular matrix There are two groups of cells in connective tissue proper: 1. Resident cells: include fibroblasts, adipocytes, fixed macrophages, and mesenchymal cells 2. Wandering cells: include mast cells, plasma cells, free macrophages, and other leukocytes © McGraw Hill 46  Cells of Connective Tissue Proper Table 4.5 Cells of Connective Tissue Proper Type of Cell Appearance Function Resident Cells Maintain and repair extracellular matrix; store materials Fibroblasts Abundant, large, relatively flat cells, often with Produce fibers and ground substance of the tapered ends extracellular matrix Adipocytes Fat cells with a single large lipid droplet; cellular Store lipid reserves components pushed to one side Fixed macrophages Large cells derived from monocytes in blood; Phagocytize foreign materials reside in extracellular matrix after leaving the blood Mesenchymal cells Stellate or spindle-shaped embryonic stem cells Divide in response to injury to produce new connective tissue cells Wandering Cells Repair damaged extracellular matrix; active in immune response Mast cells Small cells with a granule-filled cytoplasm Release histamine and heparin to stimulate local inflammation Plasma cells Small cells with a distinct nucleus derived from Form antibodies that bind to foreign activated B-lymphocytes substances, bacteria, viruses Free macrophages Mobile phagocytic cells formed from monocytes Phagocytize foreign materials of the blood Other leukocytes White blood cells that enter connective tissue Attack foreign materials (lymphocytes) or directly combat bacteria (neutrophils) © McGraw Hill 47  Protein Fibers of Connective Tissue Proper Three types of fibers produced by cells and secreted into the extracellular matrix: collagen fibers, elastic fibers, reticular fibers Collagen fibers: long, strong, unbranched Most abundant protein in human body Elastic fibers: thinner than collagen; stretch easily, branch, and rejoin Allow structures (for example, blood vessels) to stretch and recoil Reticular fibers: thinner than collagen fibers; form a branching, woven framework Found in the stroma of organs with abundant spaces such as liver, lymph nodes, and spleen © McGraw Hill 48  Ground Substance of Connective Tissue Proper A combination of proteins and carbohydrates Texture is usually gelatinous Additional content such as water and salts can result in a texture anywhere from semi-fluid (adipose) to hard (bone) © McGraw Hill 49  Categories of Connective Tissue Proper Connective tissue proper is classified into two categories: loose and dense Loose connective tissue: serves as the body’s packing material, found in spaces around organs Types include areolar, adipose, and reticular Dense connective tissue: strong, has fibers (mostly collagen) packed tightly together Types include dense regular, dense irregular, and elastic © McGraw Hill 50  Areolar Connective Tissue Contains all cells of connective tissue proper, especially fibroblasts Abundant ground substance, collagen, and elastic fibers Surrounds and protects; connects epithelia to deeper tissues Example: papillary layer of dermis Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 51  Adipose Connective Tissue Primarily composed of adipocytes, each containing a lipid droplet Stores energy, cushions organs, insulates Example: subcutaneous fat Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 52  Reticular Connective Tissue Meshwork of reticular fibers, fibroblasts, and leukocytes Provides supportive framework for many lymphatic organs Example: stroma of spleen Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 53  Dense Regular Connective Tissue Densely packed parallel collagen fibers, fibroblasts, scarce ground substance Resists stress in one direction Example: tendons Access the text alternative for slide images. © McGraw Hill ©Ed Reschke 54  Dense Irregular Connective Tissue Randomly arranged collagen fibers, fibroblasts, ground substance Resists stress in all directions Example: reticular layer of dermis Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Dennis Strete, photographer 55  Elastic Connective Tissue Many branching elastic fibers, fibroblasts, ground substance Allows stretching and recoil Example: walls of large, elastic arteries Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 56  Supporting Connective Tissue Two types of supporting connective tissue: 1. Cartilage 2. Bone © McGraw Hill 57  Cartilage Firm, gel-like extracellular matrix composed of protein and ground substance Cells are called chondrocytes Chondrocytes occupy small spaces enclosed by their extracellular matrix called lacunae Strong and resilient to provide support and withstand deformation Usually covered by perichondrium Dense irregular connective tissue and stem cells for cartilage growth © McGraw Hill 58  Types of Cartilage There are three types of cartilage: 1. Hyaline cartilage 2. Fibrocartilage 3. Elastic cartilage © McGraw Hill 59  Hyaline Cartilage Glassy matrix; chondrocytes in lacunae Most common type of cartilage, but also the weakest Smooths joint surfaces, model for bone growth Example: articular cartilage of long bones Access the text alternative for slide images. © McGraw Hill ©Ed Reschke 60  Fibrocartilage Parallel collagen fibers in matrix; chondrocytes in lacunae Absorbs shock Example: intervertebral discs Access the text alternative for slide images. © McGraw Hill ©Ed Reschke 61  Elastic Cartilage Numerous elastic fibers; closely packed chondrocytes in lacunae Extremely resilient and flexible Example: external ear Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 62  Bone Two-thirds of bone’s weight is inorganic (mostly calcium salts); one-third is organic (collagen and other proteins) Organic parts provide flexibility Inorganic parts provide compressional strength Periosteum: Dense irregular connective tissue covering Mature bone cells are called osteocytes Two forms of bone: compact bone and spongy bone Compact bone is arranged in cylindrical osteons, each containing concentric lamellae surrounding a central canal Osteocytes contact one another through canaliculi Spaces within spongy bone house hemopoietic cells that generate blood cells © McGraw Hill 63  Compact Bone Calcified matrix organized in osteons Protects organs, provides levers for movement, stores calcium Example: bones of body Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Dennis Strete, photographer 64  Fluid Connective Tissue Fluid connective tissue refers to blood and lymph Blood consists of: Plasma: a watery ground substance containing protein fibers Erythrocytes: red blood cells Leukocytes: white blood cells Platelets: fragments of blood cells involved in blood clotting Lymph is derived from plasma—has no formed elements © McGraw Hill 65  Blood Contains blood cells, platelets, and plasma Transports respiratory gases, nutrients, wastes, hormones; governs immune response Found in heart and in blood vessels throughout body Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 66  Body Membranes Membranes line the major body cavities and cover organ surfaces Consist of epithelial sheet and underlying connective tissue layer Mucous membranes line passages that open to external environment Serous membranes (for example, pericardium) have two layers (parietal and visceral) and secrete friction-reducing fluid between them Cutaneous membrane is the skin (epidermis and dermis) Synovial membranes line the cavities of some joints and secrete friction-reducing fluid there © McGraw Hill 67  Muscle Tissue Muscle is comprised of cells called muscle fibers When cells are active, internal changes cause them to shorten The result of shortening is movement Examples: movement of bones, blood, food © McGraw Hill 68  Classification of Muscle Tissue Three histological types of muscle in the body: 1. Skeletal muscle tissue 2. Cardiac muscle tissue 3. Smooth muscle tissue © McGraw Hill 69  Skeletal Muscle Tissue Long, cylindrical, striated fibers Multiple nuclei in periphery of each fiber Moves body (voluntary control) Attaches to bone and/or skin Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Al Telser, photographer 70  Cardiac Muscle Tissue Cells are: Branched (Y-shaped) and shorter than skeletal fiber cells Striated Autorhythmic—initiate own contraction Attached end-to-end by strong gap junctions at intercalated discs that allow rapid passage of electrical current from one cell to the next during each heartbeat Contraction causes movement of blood Found in wall of the heart (myocardium) Access the text alternative for slide images. © McGraw Hill ©Victor P. Eroschenko 71  Smooth Muscle Tissue Cells are: Relatively short, wide in the middle, and tapered at the ends (fusiform) Not striated Contraction causes involuntary movement of food, blood, sperm Found in walls of most internal organs Examples: stomach, intestines, urinary bladder Access the text alternative for slide images. © McGraw Hill ©Victor P. Eroschenko 72  Nervous Tissue Two types of cells in nervous tissue: Neurons: nerve cells capable of initiating and conducting electrical activity throughout the body Each cell has a prominent cell body, branches of dendrites that receive signals, and a long axon that carries signals toward other cells Glial cells: cells that support and protect neurons Communication and control of body functions Found in brain, spinal cord, and nerves Access the text alternative for slide images. © McGraw Hill ©McGraw-Hill Education/Richard Gross, photographer 73  Tissue Change and Aging Tissues changes: Metaplasia: epithelia lining respiratory airways of people who smoke change from pseudostratified ciliated to stratified squamous Hypertrophy: an increase in the size of existing cells Hyperplasia: an increase in number of cells in a tissue Neoplasia: out-of-control growth, which forms a tumor Atrophy: shrinkage of tissue by cell size or number Tissue aging: Epithelia thin, connective tissues lose pliability Repair processes lose efficiency © McGraw Hill 74