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Tissues tissue = many cells w/ same structure and function cell shape aids its function tissue shape aids its function Histology = study of tissues 4 types of tissues Epithelial coverings contact openings Connective support connect other tissues Muscle movement contraction Nerve control conduct impulse we, our organs, are built in layers epithelial tissue dense connective tissue adipose c.t. muscle bone (not seen) organs are built in layers : epithelial tissue dense connective tissue adipose c.t. muscle functions of epithelial tissues : protection prevent passage across epithelia permeability allow passage across epithelia lubrication of surfaces the function of the epithelial tissue depends on its structure characteristics of epithelia: contact opening covers body surfaces lines hollow organs forms glands skin mouth lung stomach urinary bladder blood vessels respiratory tract skin digestive tract opening epithelium apical surface = free surface basal surface contacts the opening contacts connective tissue apical surface basal surface lumen open space in organ or blood vessel lumen cellularity specialized contacts between cells tight junctions zona occludens seals area between cells desmosomes anchoring junctions holds cells together basement membrane holds epithelium to connective tissue Figure 3.5 Special characteristics of epithelium. Cilia Narrow extracellular space Microvilli Apical region of an epithelial cell Cell junctions Tight junction Epithelium Desmosome Gap junction Basal region Nerve ending Connective tissue Capillary Copyright © 2011 Pearson Education, Inc., publishing as Pearson Benjamin Cummings. Basal lamina Basement Reticular membrane fibers Figure 3.5 Cell junctions. Plasma membranes of adjacent cells Microvilli Intercellular space Basement membrane Intercellular space Plaque Interlocking junctional proteins Intercellular space Intercellular space Channel between cells (connexon) Intermediate filament (keratin) (a) Tight junctions: Impermeable junctions prevent molecules from passing through the intercellular space. Linker glycoproteins (cadherins) (b) Desmosomes: Anchoring junctions bind adjacent cells together and help form an internal tension-reducing network of fibers. Copyright © 2011 Pearson Education, Inc., publishing as Pearson Benjamin Cummings. (c) Gap junctions: Communicating junctions allow ions and small molecules to pass from one cell to the next for intercellular communication. avascular regeneration no blood vessels active mitosis replaces cells that are lost definitions simple stratified = = one layer many layers squamous cuboidal columnar = = = flat box like tall simple squamous epithelium structure one row of very thin cells function thin - allow exchange of chemicals through the tissue smooth - to decrease friction in the lumen location lung capillaries blood vessels Figure 19.3a Capillary structure. Pericyte Red blood cell in lumen Intercellular cleft Endothelial cell Basement membrane Tight junction Endothelial nucleus Pinocytotic vesicles Continuous capillary. Least permeable, and most common (e.g., skin, muscle). © 2013 Pearson Education, Inc. simple squamous smooth , thin Figure 22.8 Respiratory zone structures. Alveoli Alveolar duct Respiratory bronchioles Alveolar duct Terminal bronchiole Alveolar sac Respiratory bronchiole Alveolar duct Alveoli Alveolar sac © 2013 Pearson Education, Inc. Alveolar pores Figure 4.3a Epithelial tissues. Simple squamous epithelium Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia. Air sacs of lung tissue Nuclei of squamous epithelial cells Function: Allows materials to pass by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae. Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae). Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (140x). © 2013 Pearson Education, Inc. artery wall simple squamous epithelium artery wall : simple squamous (endothelium) connective tissue simple cuboidal epithelium structure one row of square/oval cells round nucleus function secretions into the opening location glands (exocrine glands) kidney why simple? simple cuboidal basement membrane connective tissue Glands are long, coiled openings lined with cuboidal cells. So, when we slice through the tissue, we get many circular arrangements of cuboidal cells Figure 4.3b Epithelial tissues. Simple cuboidal epithelium Description: Single layer of cubelike cells with large, spherical central nuclei. Simple cuboidal epithelial cells Nucleus Function: Secretion and absorption. Basement membrane Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface. Connective tissue Photomicrograph: Simple cuboidal epithelium in kidney tubules (430x). © 2013 Pearson Education, Inc. kidney tubules simple cuboidal epithelium Simple cuboidal epithelium (kidney tubules) Simple cuboidal epithelium Lumen of kidney tubule Nucleus Cuboidal cell Figure 4.5 Types of multicellular exocrine glands. Tubular secretory structure Simple duct structure Compound duct structure (duct does not branch) (duct branches) Simple tubular Simple branched tubular Example Example Compound tubular Intestinal glands Stomach (gastric) glands Duodenal glands of small intestine Example Alveolar secretory structure Simple alveolar Simple branched alveolar Compound alveolar Example No important Example Sebaceous (oil) Example Mammary glands example in humans glands Surface epithelium Copyright © 2010 Pearson Education, Inc. Duct Compound tubuloalveolar Example Salivary glands Secretory epithelium simple columnar epithelium structure one row of tall cells function absorption from the opening ; and some secretion location stomach small and large intestines why simple? Figure 4.3c Epithelial tissues. Simple columnar epithelium Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucussecreting unicellular glands (goblet cells). Microvilli Simple columnar epithelial cell Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action. Mucus of goblet cell Location: Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus. Basement membrane Photomicrograph: Simple columnar epithelium of the small intestine mucosa (660x). © 2013 Pearson Education, Inc. Goblet cells specialized columnar cell function secretes mucus ; lubricates the free surface location small intestine large intestine respiratory tract ciliated epithelium hair-like organelle that protrudes out of the cell function to move things along the tract location respiratory tract fallopian tube ciliated columnar epithelium pseudostratified ciliated columnar epithelium Pseudostratified epithelium (trachea) Cilia Pseudostratified epithelium Nuclei of epithelial cells Figure 4.3d Epithelial tissues. Pseudostratified columnar epithelium Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia. Cilia Pseudostratified epithelial layer Function: Secrete substances, particularly mucus; propulsion of mucus by ciliary action. Location: Nonciliated type in male’s sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract. Trachea © 2013 Pearson Education, Inc. Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (800x). Basement membrane pseudostratified ciliated columnar epithelium microvilli structure folds of the cell membrane on columnar or cuboidal cells function increases surface area for absorption location small and large intestines = brush border kidney Figure 4.6 Cell junctions. Plasma membranes of adjacent cells Microvilli Intercellular space Basement membrane Copyright © 2011 Pearson Education, Inc., publishing as Pearson Benjamin Cummings. simple columnar epithelium - with microvilli Figure 4.3c Epithelial tissues. Simple columnar epithelium Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells). Microvilli Simple columnar epithelial cell Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action. Location: Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus. © 2013 Pearson Education, Inc. Mucus of goblet cell Basement membrane Photomicrograph: Simple columnar epithelium of the small intestine mucosa (660x). stratified squamous epithelium structure several rows of flat cells may have cuboidal-like cells near basal area function protection location skin mouth esophagus vagina anal canal Figure 4.3e Epithelial tissues. Stratified squamous epithelium Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers. Stratified squamous epithelium Function: Protects underlying tissues in areas subjected to abrasion. Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane. © 2013 Pearson Education, Inc. Nuclei Basement membrane Connective tissue Photomicrograph: Stratified squamous epithelium lining the esophagus (285x). Stratified squamous epithelium (esophagus) Squamous cell Nuclei Stratified squamous epithelium transitional epithelium structure several rows of round cells may decrease # of rows, and flatten, when stretched function allows epithelia to stretch, when organ is filled location urinary bladder ureter Figure 4.3f Epithelial tissues. Transitional epithelium Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch. Transitional epithelium Function: Stretches readily, permits stored urine to distend urinary organ. Location: Lines the ureters, bladder, and part of the urethra. Photomicrograph: Transitional epithelium lining the bladder, relaxed state (360x); note the bulbous, or rounded, appearance of the cells at the surface; these cells flatten and elongate when the bladder fills with urine. © 2013 Pearson Education, Inc. Basement membrane Connective tissue transitional epithelium note: this is not stratified cuboidal stratified cuboidal epithelium structure two rows of square/oval cells location ducts of glands Figure 4.3f Epithelial tissues. (f) Stratified cuboidal epithelium Description: Generally two layers of cubelike cells. Basement membrane Cuboidal epithelial cells Function: Protection Location: Largest ducts of sweat glands, mammary glands, and salivary glands. Duct lumen Photomicrograph: Stratified cuboidal epithelium forming a salivary gland duct (285). old text Copyright © 2011 Pearson Education, Inc., publishing as Pearson Benjamin Cummings. Stratified cuboidal epithelium gland (gland ducts) Lumen of duct Stratified cuboidal epithelium Figure 4.5 Types of multicellular exocrine glands. Simple duct structure (duct does not branch) Tubular secretory structure Simple tubular Example Intestinal glands Compound duct structure (duct branches) Simple branched tubular Example Compound tubular Stomach (gastric) glands Duodenal glands of small intestine Example Alveolar secretory structure Simple alveolar Simple branched alveolar Example Compound alveolar No important example in humans Example Example Sebaceous (oil) glands Mammary glands Surface epithelium © 2013 Pearson Education, Inc. Compound tubuloalveolar Example Salivary glands Duct Secretory epithelium typical cross sections through glands ; ducts