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CHAPTER 4 TISSUES Tissues Classification of Epithelia A tissue is a group of cells with similar Epithelial tissues are classified primar...

CHAPTER 4 TISSUES Tissues Classification of Epithelia A tissue is a group of cells with similar Epithelial tissues are classified primarily structure and function, plus extracellular according to the number of cell layers and substance surrounding them. the shape of the superficial cells. Histology is the study of tissues The cell layers can be simple, stratified, or pseudostratified. Types of Tissues The cell shapes can be squamous, cuboidal, - There are four tissue types in the human columnar, or a special transitional shape body: that varies with the degree of stretch. 1. Epithelial- a covering or lining tissue Simple epithelium consists of a single layer 2. Connective- a diverse primary tissue type of cells, with each extending from the that makes up part of every organ in the basement to the free surface. body Stratified epithelium consists of more than 3. Muscle- a tissue that contracts or shortens, one layer of cells, but only the basal layer making movement possible attaches the deepest layer to the basement 4. Nervous- responsible for coordinating and membrane controlling many body activities Pseudostratified columnar epithelium is a special type of simple epithelium that appears to be falsely stratified. Epithelial Tissues It consists of one layer cells, with all the cells Epithelium, or epithelial tissue, covers and attached to the basement membrane protects surfaces, both outside and inside the Due to variations in the shape of the cells, the body epithelia appears stratified Included under the classification of epithelial tissue are the exocrine and Classification of Epithelia endocrine glands There are three types of epithelium based on idealized shapes of the epithelial cells: Epithelial Tissue Characteristics 1. Squamous - cells are flat or 1. Mostly composed of cells scalelike 2. Covers body surfaces 2. Cuboidal - cells are cube-shaped 3. Distinct cell surfaces about as wide as they are tall 4. Cell and matrix connections 3. Columnar - cells tend to be taller 5. Nonvascular than they are wide 6. Capable of regeneration Simple Squamous Epithelium Simple squamous epithelium is a single layer of thin , flat cells Some substances easily pass through this thin layer of cells, but substances do not. The lungs, simple squamous epithelium, allows gas exchange The kidneys, simple squamous epithelium, helps filter wastes from the blood while keeping the blood cells inside the blood Functions of Epithelial Tissues vessels. 1. Protects underlying structures 2. Acts as a barrier 3. Permits passage of substances 4. Secretes substances 5. Absorption of substances KYLA ELYSHA MARIE P. RONDAN BSN 1-F 1  CHAPTER 4 TISSUES Simple Cuboidal Epithelium Stratified Squamous Epithelium Simple cuboidal epithelium is a single layer Stratified squamous epithelium forms a of cube-like cells that carry out active thick epithelium because it consist of several transport, facilitated diffusion, or secretion. layers of cells They have a greater secretory capacity than Though the deepest cells are cuboidal or simple squamous epithelial cells columnar and are capable of dividing and producing new cells, the naming is base on the shape of the surface cells There are two types of stratified squamous epithelia: Keratinized stratified squamous and nonkeratinized stratified squamous epithelia Keratinized Stratified Squamous Epithelium The outer layer of the skin is comprised of a Simple Columnar Epithelium keratin squamous epithelium Simple columnar epithelium is a single The keratin reduces the loss of water from the layer of tall, thin cells body The large size of these cells enables them to perform complex functions, such as secretion. Nonkeratinized Stratified Squamous The simple columnar epithelium of the small Epithelium intestine produces and secretes mucus and Stratified squamous epithelium of the mouth digestive enzymes. is a moist nonkeratinized stratified squamous epithelium This nonkeratinized stratified squamous epithelium provides protection against abrasion and acts as a mechanical barrier Water, however, can move across it more readily than across the skin (keratinized stratified squamous) Pseudostratified Columnar Epithelium Pseudostratified columnar epithelium secretes mucus, which covers its free surface Cilia in the airways move the mucus and accumulated debris toward the throat, where it is swallowed Stratified Cuboidal Epithelium Stratified cuboidal epithelium consists of more than one layer of cuboidal epithelial cells This epithelial type is relatively rare and is found in sweat gland ducts, ovarian follicular cells, and the salivary glands It’s function in absorption, secretion, and protection KYLA ELYSHA MARIE P. RONDAN BSN 1-F 2  CHAPTER 4 TISSUES Stratified Columnar Epithelium Cell Connections Stratified ColumnarEpithelium consists of Cells have several structures that hold one more than one layer of epithelial cells; the cell to one another or to the basement surface cells are columnar but the deeper membrane cells are irregular or cuboidal in shape These structures do three things: Like stratified cuboidal epithelium, stratified mechanically bind the cells together, help columnar epithelium is relatively rare, found form a permeability barrier, and provide a in the mammary gland ducts, the larynx, mechanism for intercellular communication and a portion of the male urethra Desmosomes are mechanical links that bind This epithelium carries out secretion, cells together protection, and some absorption. Hemidesmosomes are half desmosomes that anchor cells to the basement membrane Transitional Epithelium Tight junctions prevent the passage of Transitional epithelium is a special type of materials between epithelial cells because stratified epithelium that can be greatly they completely surround each cell, similar stretched to the way a belt surrounds the waist. Tight The shape of the cells change as the junctions are found in the lining of the epithelium is stretched intestines Transitional epithelium lines cavities that Materials that pass through the epithelial can expand greatly, such as the urinary layer must pass through the cells, so those bladder cells regulate what materials can cross It also protects underlying structure, like the Gap junctions are small channels that allow urinary bladder, from the caustic effects of small molecules and ions to pass from one urine epithelial cell to an adjacent one Most epithelial cells are connected to one another by gap junctions, and researchers believe that molecules or ions moving through the gap junctions act as communication signals to coordinate the activities of the cells Free Cell Surfaces Most epithelia have a free surface that is not in contact with other cells and faces away from underlying tissues The characteristics of the free surface reflect its functions The free surface can be smooth or lined with microvilli or cilia Cili move materials over the top of the cell Microvilli increase surface area KYLA ELYSHA MARIE P. RONDAN BSN 1-F 3  CHAPTER 4 TISSUES Glands Exocrine Glands Glands are secretory organs that secretes Exocrine glands can be classified according substances onto a surface, into a cavity, or to how products leave the cell into the bloodstream Merocrine secretion involves the release of Glands are composed primarily of secretory products by exocytosis epithelium, with a supporting network of Apocrine secretion involves the release of connective tissue secretory products as pinched-off fragments Glands with ducts are called exocrine glands of the gland cells Both the gland and its ducts is lined with Holocrine secretion involves the shedding of epithelium the entire cells Endocrine glands are ductless glands; they secrete their products (termed hormones) into the bloodstream Most exocrine glands are multicellular, comprised of many cells Some exocrine glands are composed of a single cell, like goblet cells, that secretes mucus Multicellular exocrine glands can be classified according to the structure of their ducts and secretory regions Simple glands have a single, non-branched Connective Tissue duct, some have branched ducts Connective tissue is a diverse primary tissue Compound exocrine glands have multiple, type that makes up part of every organ in the branched ducts body Glands with secretory regions shaped as Connective tissue differs from the other three tubules (small tubes) are called tubular, tissue types in that it consist of ells separated whereas those shaped in saclike structures from each other by abundant extracellular are called acinar or alveolar matrix Tubular glands can be straight or coiled Connective tissue is diverse in both structure Glands with a combination of the two are and function called tubuloacinar or tubuloalveolar Connective tissue is comprised of cells, protein fibers, and extracellular matrix Exocrine Gland Structures Function of Connective Tissue 1. Enclose and separate other tissues 2. Connecting tissues to one another 3. Supporting and moving parts of the body 4. Storing compounds 5. Cushioning and insulating 6. Transorting 7. Protecting KYLA ELYSHA MARIE P. RONDAN BSN 1-F 4  CHAPTER 4 TISSUES Connective Tissue Cells Matrix Ground Substance The specialized cells of the various connective The ground substance consists of non-fibrous tissues produce the extracellular matrix molecules and is shapeless The name of the cell identifies the cell It consists of proteoglycans, which are large functions molecules that consist of a protein core Osteoblasts form bone, osteocytes maintain attached to many long polysaccharides it, and osteoclasts break it down Proteoglycans trap large quantities of water Fibroblasts are cells that form fibrous between the polysaccharides, which allows connective tissue, and fibrocytes maintain it them to return to their original shape when Chondroblasts from cartilage and compressed or deformed chondrocytes maintain it Found in connective tissue are cells Types of Connective Tissue associated with the immune system, such as The two types of connective tissue are white blood cells embryonic and adult connective tissue Macrophages are large cells that are By eight weeks of development, most of the capable of moving about and ingesting embryonic connective tissue has become foreign substances, including specialized to form the types of connective microorganisms in the connective tissue tissue seen in adults Mast cells are nonmotile cells that release Loose connective tissue consists of relatively chemicals, such as histamine, that promote few protein fibers that form a lacy network, inflammation with numerous spaces filled with ground substance and fluid Three subdivisions of loose connective tissue Extracellular Matrix are areolar, adipose, and reticular The extracellular matrix of connective tissue Areolar connective tissue primarily consists has three major components: protein fibers, of collagen fibers and a few elastic fibers ground substance, and fluid The most common cells in loose connective Ground substance consists of non-fibrous tissue are the fibroblasts protein and other molecules Adipose tissue consists of adipocytes, or fat The structure of the matrix is responsible for cells, which contain large amounts of lipid the functional characteristics of connective for energy storage. Adipose tissue pads and tissues- for example, they enable bones and protects parts of the body and acts as a cartilage to bear weight thermal insulator Reticular tissue forms the framework of lymphatic tissue, such as in the spleen and lymph nodes, as well as in bone marrow and Matrix Protein Fibers the liver Three types of protein fibers—- collagen, reticular, and elastic—- help form most connective tissues Collagen fibers, which resemble microscopic ropes, are very flexible but resist stretching Reticular fibers are very fine, short collagen fibers that branch to form a supporting network Elastic fibers have the ability to return to their original shape after being stretched or compressed, giving tissue an elastic quality KYLA ELYSHA MARIE P. RONDAN BSN 1-F 5  CHAPTER 4 TISSUES Types of Connective Tissues Cartilage Dense connective tissue has a relatively Cartilage is composed of chondrocytes, large number of protein fibers that form located in spaces called lacunae within an thick bundles and fill nearly all of the extensive matrix extracellular space Collagen in the matrix gives cartilage There two major subcategories of dense flexibility and strength connective tissue: collagenous and elastic Cartilage is resilient because proteoglycans of the matrix trap water Dense Collagenous Cartilage provides support, but if bent or Dense collagenous connective tissue has an slightly compressed, it resumes its original extracellular matrix consisting mostly of shape collagen fibers Dense collagenous connective tissue having Three Types of Cartilage collagen fibers oriented in the same direction 1. Hyaline cartilage is the most abundant type is termed dense regular if cartilage and has many functions, such as Examples of dense regular are tendons and covering the ends of bones, where they form ligaments joints Dense collagenous connective tissue having 2. Fibrocartilage has more collagen than does the collagen fibers oriented in the multiple hyaline cartilage and is able to withstand directions is termed dense irregular compression and resist tearing or pulling Examples of dense irregular are in the - Fibrocartilage is found in the disks dermis of the skin and in organ capsules between the vertebrae (bones at the back) and in some joints, such as the knee and temporomandibular (jaw) joints 3. Elastic Cartilage contains elastic fibers in addition to collagen and proteoglycans - The elastic fibers appear as coiled fibers among bundles of collagen fibers - Elastic cartilage is able to recoil to its original shape when bent Dense Elastic - The external era, epiglottis, and Dense elastic connective tissue has abundant auditory tube contain elastic elastic fibers among its collagen fibers cartilage The elastic fibers allow the tissue to stretch and recoil Examples include the dense elastic connective tissue in the vocal cords A genetic condition called Marfan syndrome results from, in part the inability to properly maintain and form elastic fibers KYLA ELYSHA MARIE P. RONDAN BSN 1-F 6  CHAPTER 4 TISSUES Muscle The main function of muscle tissue is to contract, shorten, making movement possible. Muscle contraction results from contractile proteins located within the muscle cells Three types of Muscle 1. Skeletal muscle attaches to the skeleton and Bone enables the body to move Bone is a hard connective tissue that consists - Skeletal muscle cells are striated, or of living cells and a mineralized matrix. banded, because of the Osteocytes are located within lacunae arrangement of contractile proteins The strength and rigidity of the mineralized within the cells matrix enables bones to support and protect other tissues and organs Two types of bone tissue exist: spongy bone and compact bone Spongy bone has spaces between trabeculae or plates, of bone and therefore resembles a sponge Compact bone is more solid, with almost no space between many thin layers of mineralized matrix 2. Cardiac muscle is the muscle of the heart; it is responsible for pumping blood. - Cardiac muscle cells are cylindrical but much shorter than skeletal muscle cells - Cardiac muscle cells are striated and usually have one nucleus per cell - They are often branched and connected to one another by Blood intercalated disks Blood is a liquid connective tissue It contains a liquid matrix, termed the plasma, along with formed elements The formed elements are erythrocytes, leukocytes, and platelets It functions in transport of food, oxygen, waste, hormones, and other substances KYLA ELYSHA MARIE P. RONDAN BSN 1-F 7  CHAPTER 4 TISSUES 3. Smooth muscle forms the walls of hollow Tissue Membranes organs; it is also found in the skin and the The skin, termed the cutaneous membrane, is eyes an external body surface membrane - Smooth muscle is responsible for a Many, but not all, mucous membranes number of functions, such as secrete mucus moving food through the digestive The functions of mucous membranes include tract and emptying the urinary protection, absorption, and secretion bladder - Smooth muscle cells are tapered at Mucous Membranes each end, have a single nucleus, and The mucous membranes line cavities that are not striated open to the outside of the body, such as the digestive, respiratory, and reproductive tracts Mucous membranes consist of epithelial cells, their basement membrane, and thick layer of loose connective tissue. Serous Membranes Serous membranes line cavities that do not open to the exterior of the body, such as the pericardial, pleural, and peritoneal cavities Nervous Tissue Serous membranes consist of three components: a layer of simple squamous Nervous tissue forms the brain, spinal cord, epithelium, its basement membrane, and and nerves. It is is responsible for delicate layer of loose connective tissue coordinating and controlling many body Serous membranes do not contain glands, activities but they secrete a small amount of fluid Nervous tissue consists of neurons and called serous fluid, which lubricates the support cells, termed glial cells surface of the membranes The neuron is responsible for conducting action potentials. It is composed of three parts: cell body, dendrites, and an axon Synovial Membranes Synovial membranes line the cavities of freely movable joints They are made up of only connective tissue and consist of modified connective tissue cells Synovial membranes produce synovial fluid, which makes the joint very slippery, thereby reducing friction and allowing smooth movement within the joint Tissue Membranes A tissue membrane is a thin sheet or layer of tissue that covers a structure or lines a cavity Most membranes consist of epithelium and the connective tissue on which the epithelium rests There are four tissue membranes in the body: cutaneous, mucous, serous, and synovial KYLA ELYSHA MARIE P. RONDAN BSN 1-F 8  CHAPTER 4 TISSUES Regeneration can completely repair some Tissue Inflammation tissues, such as the skin and the mucous Inflammation is usually a beneficial process membrane of the intestine. In these cases, occurring when tissues are damaged. regeneration is accomplished primarily by When viruses infect epithelial cells of the stem cells upper respiratory tract, inflammation and Stem cells are self-renewing, the symptoms of the common cold are undifferentiated cells that continue to divide produced sequential steps The inflammatory process occurs in stages Inflammation mobilizes the body’s defenses and isolates and destroys microorganisms, foreign materials, and damaged cells so that tissue repair can proceed Inflammation produces five major symptoms: 1. Redness 2. Heat 3. Swelling 4. Pain 5. Disturbance of function Tissue Repair Tissue repair involves substitution of dead cells for viable cells Tissue repair can occur by regeneration or by fibrosis In regeneration, the new cells are the same type as those that were destroyed, and normal function is usually restored In fibrosis, or replacement, a new type of tissue develops that eventually causes scar production and the loss of some tissue function KYLA ELYSHA MARIE P. RONDAN BSN 1-F 9