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Biology 220 Test 1 Chapter 5: Histology  This chapter deals with the four basic tissue types: epithelia (simple squamous, cuboidal, columnar, transitional,  pseudostratified,  stratified, & glandular), connective (blood, loose areolar,  dense  regular, dense irregular, adipose, cartilage, & bone), muscle (skeletal, smooth, & cardiac), and nervous (neurons & neuroglial cells). It also covers membranes (mucous, serous, synovial, & cutaneous).  Introduction ● histology : the study of tissues (group of similar cells that do a specific job for you that the individual cell cannot do by itself) ● four types of tissue: ▪ epithelial ▪ connective ▪ muscle ▪ nervous  Epithelial Tissue ● consists of a sheet of closely-packed adhering cells; with the upper surface exposed to the environment or to an internal space in the body; extracellular material is thin ● covers  the  body  surface,  lines body cavities, forms external & internal linings of many organs, & constitutes most gland tissue ● protection ▪ protects deeper tissues from invasion & injury ● secretion ▪ produces mucus, sweat, enzymes, hormones, & most of the body’s other secretions; glands are composed largely of epithelial tissue ● excretion ▪ epithelia void wastes from tissues ● absorption ▪ epithelia absorb chemicals from the adjacent medium ● filtration ▪ all substances leaving the blood are selectively filtered through epithelia that lines the blood vessels; urinary waste is filtered through epithelia of kidneys ● sensation ▪ epithelia are provided with nerve endings that sense stimulation ranging from a touch on the skin to irritation of the stomach ● epithelia are  avascular (no room between cells for blood vessels) ● almost always lies on a vessel-rich layer of loose connective tissue ● between epithelium & connective tissue is a layer called the  basement membrane  ▪ contains collagen, glycoproteins, & other protein-carbohydrate complexes

▪ serves to anchor epithelium to the connective tissue ▪ regulates exchange of materials ▪ binds growth factors from below that regulate epithelial development ● surface  of  epithelia  that  faces  the basement membrane is its  basal membrane, & the one that faces away from the basement membrane toward the internal cavity (lumen) of an organ is the  apical surface ● epithelia has 2 broad categories:  simple (single layer of cells) & s tratified (multiple)  Simple Squamous Epithelium ● microscopic appearance ▪ one layer of t hin, scaly, flat cells ▪ nuclei appear round ▪ has desmosomes (gap welding) ● representative locations ▪ air  sacs (alveoli) of lungs, glomerular capsules of kidneys, some kidney tubules,  inner  lining (endothelium) of heart &  blood vessels, serous membranes of stomach,  intestines, & some other viscera, & surface mesothelium of pleura, pericardium, peritoneum, & mesenteries ● functions ▪ allows rapid diffusion or transport of substances through membrane − endocytosis, exocytosis, diffusion, osmosis, & filteration ▪ secretes lubricating serious fluid ▪ lines spaces & covers organs in spaces that do not  open to the  outside world  Simple Cuboidal Epithelium ● microscopic appearance ▪ one layer of s quare or round cells ▪ in  glands, cells are often pyramidal & arranged like segments of an orange around a central space ▪ spherical, centrally placed nuclei ▪ with a brush border of microvilli in some kidney tubules ▪ ciliated in bronchioles of the lung ● representative locations ▪ liver, thyroid, mammary, slavery, & other glands, most kidney tubules (nephron unit) , & bronchioles ▪ nephron: structural & functional unit of kidney that consists of glomerulus & renal tubules ● functions ▪ absorption & secretion ▪ production of protective mucous coat ▪ movement of respiratory mucus ▪ important for o  smosis & diffusion 

Simple Columnar Epithelium ● microscopic appearance ▪ one layer of tall, narrow  cells with oval  or sausage-shaped  nuclei  that  are  vertically orientated, usually in the  basal half of the cell ▪ apical portion of the cell often shows secretory vesicles visible with TEM ▪ often shows a brush border of m  icrovilli (increase surface area) ▪ ciliated in some organs ▪ may have  goblet cells which release mucus (cause epithelial can be glandular) − serves as a u  ni-cellular  exocrine gland ▪ protein molecules can act as a buffer & are  amphoteric  − act as a receptor or give up (acid or base) ● representative locations ▪ inner lining of the stomach, intestines, gallbladder, uterus, uterine tubes, & some kidney tubules ● functions ▪ absorption ▪ secretion of mucus & other products ▪ movement of egg & embryo in uterine tube  Pseudostratified Epithelium ● microscopic appearance ▪ give off a “false” appearance ▪ looks multilayered , but each cell touches the basement membrane ▪ nuclei at several levels in deeper half of the epithelium ▪ often consist of goblet cells ▪ often are ciliated ● representative locations ▪ respiratory tract from  nasal  cavity  to  bronchi  & portions of the male urethra ● functions ▪ secretes & propels mucus  Transitional Epithelium ● microscopic appearance ▪ somewhat resembles stratified squamous epithelium, but surface cells are rounded & often bulge ▪ typically 5 or 6 cells thick when relaxed & 2 or 3 when stretched ▪ cells may be flatter & thinner when epithelium is stretched (distended bladder) ▪ some cells have 2 nuclei ▪ would never expect to find a gap junction or desosome between these cells ▪ avascular (no blood vessels) ● representative locations

urinary tract – part of the kidney, ureter, bladder, part of uretha, & umbilical cord ● functions ▪ stretches to allow filling of the urinary tract ▪

 Glands ● gland: cell or organ  composed predominately  of  epithelial  tissue  that  secretes  substances for use elsewhere in the body or for elimination as waste ● gland product may be something synthesized by the gland cells or something removed from the tissues & modified by the gland ● the product is called  secretion if it is useful to the body (enzymes & hormones) ● the product is called  excretion if it is a waste product (urine)  Glandular Epithelium Tissue ● exocrine glands ▪ all multicellular (tubular or acinar) glands, but can also be unicellular (goblet) ▪ maintain contact with the surface by the way of a  duct ▪ secretion may be released to the body surface − sweat, mammary, & tear glands ▪ more often released into the cavity (lumen) of another organ − salivary glands, the liver, & the  pancreas ● endocrine glands ▪ lose contact with the surface & have no ducts ▪ high density of blood capillaries & secrete products directly into the blood ▪ secretions of endocrine glands, called h  ormones, function as chemical messengers to stimulate cells elsewhere in the body ▪ pituitary, thyroid, & adrenal glands  Classify Glands by Function ● holocrine glands ▪ compound, thinner gland ▪ cells accumulate a product & then the entire cell disintegrates ▪ secretion is a m  ixture  of cell fragments & the substance the cell had synthesized prior to disintegration ▪ can become infected with bacteria leaving a boil − if not removed completely, the left over cells will reproduce ▪ oil-producing glands of the scalp & certain glands of the eyelids ● merocrine (eccrine) glands ▪ vessels that release secretion that is made by exocytosis ▪ tear glands, p  ancreas, gastric glands, etc. ▪ ring around the bathtub is this oil ● apocrine glands ▪ secretion composed of blobs of apical cytoplasm that broke away from the cell surface

▪ cross between holocrine & merocrine glands ▪ axillary (armpit), sweat, & mammary glands (all odor glands)  Connective Tissues ● most abundant, widely distributed, & histologically variable of primary tissues ● include fibrous tissue, adipose tissue, cartilage, bone, & blood ● cells are scattered around & occupy less space than the extracellular matrix ● cells m  ake the connective tissue & the matrix ● serve to bind organs to each other, form structural framework, or support & protect ● vary in vascularity ● binding of organs ▪ tendons bind muscle to bone, ligaments bind one bone to another, fats hold the kidneys & eyes in place, & fibrous tissue binds skin to underlying muscle ● support ▪ bones support the body ▪ cartilage supports the ears, nose, trachea, & bronchi ▪ fibrous tissues form structural framework of organs (liver, spleen, etc.) ● physical protection ▪ cranium, ribs, & sternum protect organs such as the brain, lungs, & heart ▪ fatty cushions around the kidneys and eyes protect these organs ● immune protection ▪ cells attack foreign invaders ▪ fiber forms a “battlefield” under the skin & mucous membranes where immune cells can be quickly mobilized against disease agents ● movement ▪ bones provide lever system for body movement ▪ cartilages are involved in movement of vocal cords & ease joint movements ● storage ▪ fat is the body’s major energy reserve ▪ bone is a reservoir of calcium & phosphorus that can be used when needed ● heat production ▪ metabolism of brown fat generates heat in infants & children ● transport ▪ blood transports gases, nutrients, wastes, hormones, & blood cells  Fibrous Connective Tissue ● also called fibroconnective tissue or c onnective tissue proper  ● most diverse type ● cell types: ▪ fibroblasts : large, fusiform cells that often show slender, wispy branched; produce fibers & ground substances that form the matrix of the tissue ▪ macrophages: large, phagocytic cells that wander through tissue, where they engulf & destroy bacteria, other foreign particles, & dead/dying cells;

activate immune system when sense foreign matter (antigens); arise from white blood cells called monocytes or from the same stem cells ▪ leukocytes or  white blood cells: travel briefly in bloodstream, then crawl out the walls of a small vessel & spend time in tissue; type of neutrophils (attack bacteria) & lymphocytes (react against bacteria, toxins, & other foreign agents, & form dense patches in the mucous membranes) ▪ plasma cells : certain lymphocytes that turn into plasma cells when they detect foreign agents; synthesize disease-fighting proteins called antibodies; rarely seen except in walls of intestines & inflamed tissue ▪ mast  cells: found alongside blood vessels, secrete a chemical called heparin that  inhibits blood clotting, & one called histamine that increases blood flow by dilating blood vessels ▪ adipocytes or f at cells: appear in small clusters in tissue ▪ a blast is a cell that is in the process of reproducing & growing, where a cyte is the adult or mature cell; many cells can drift back and forth from blast to cyte ● fiber types (protein): ▪ collagenous fibers : tough & flexible fibers made of collagen, that resist stretching; have a white appearance in tendons, thus called white fibers; in tendons, ligaments, & dermis; pervades matrix of cartilage & bone; when shrivel you age − reticular fibers : thin collagen fibers coated with glycoproteins; form a sponge-like framework for organs such as the spleen & lymph notes − elastic fibers : thinner than  collagenous fibers; branch  &  rejoin each other along their course; made of a protein (elastin) whose coiled structures allow it to stretch & recoil; account for ability of lungs, skin, & arteries to spring back after they are stretched; fresh fibers called yellow fibers ● ground substances: ▪ glycosaminoglycan (GAG): long polysaccharide composed of unusual disaccharides called amino sugars & uronic acid; negatively charged; regulate water & electrolyte balance of tissue − chondroitin sulfate: responsible for stiffness of cartilage ▪  p  roteoglycan : create structural bond between cells and extracellular macromolecules & help to hold tissue together ▪ adhesive glycoproteins : protein-carbohydrate complexes that bind plasma membrane proteins to collagen & proteoglycans outside the cell ● tissue types: ▪ loose connective : much of the space is occupied by ground substances ▪ dense connective: fibers occupy more space than the cells  & ground substances  Loose Areolar Connective Tissue ● microscopic appearance

▪ loose arrangement of collagenous & elastic fibers in many directions ▪ scattered cells of various types ▪ abundant ground substance & numerous blood vessels ● representative locations ▪ underlying  nearly all epithelia tissue, surrounding blood vessels, nerves, esophagus,  & trachea, fascia between muscles, mesenteries, & visceral layers of pericardium & pleura  ● functions ▪ loosely binds epithelia to deeper tissues ▪ allows passage of nerves & blood vessels through other tissues ▪ provides an arena for immune defense ▪ blood vessels provide nutrients & waste removal for overlying epithelia  Reticular Loose Connective Tissue ● microscopic appearance ▪ loose network of reticular fibers & cells (fibroblasts) ▪ infiltrated with numerous leukocytes, especially lymphocytes ● representative locations ▪ lymph nodes, spleen, thymus, bone marrow ● functions ▪ supportive stroma (framework) for lymphatic organs  Dense Regular Connective Tissue ● microscopic appearance ▪ densely packed,  parallel , often wavy collagen fibers ▪ slender fibroblast nuclei compressed between collagen bundles ▪ scanty open space (ground substance) ▪ scarcity of blood vessels ● representative locations ▪ tendons & ligaments ● functions ▪ ligaments tightly bind bones together and resist stress ▪ tendons attach muscle to bone & transfer muscular tension to bones  Dense Irregular Connective Tissue ● microscopic appearance ▪ densely packed collagen fibers running in r andom directions  with few visible cells ▪ scanty open space (ground substance) ▪ scarcity of blood vessels ● representative locations ▪ deeper portion of dermis of skin, capsules around viscera such as liver, kidney, & spleen, & fibrous sheaths around cartilages & bones ● functions

▪ durable,  hard to tear so withstands stresses applied in unpredictable directions  Adipose Connective Tissue ● microscopic appearance ▪ dominated by adipocytes (large, empty-looking cells with thin margins) ▪ tissue sections are often very pale because of scarcity of stained cytoplasm ▪ nucleus is pressed against the plasma membrane ▪ blood vessels are present ● representative locations ▪ subcutaneous fat beneath  skin, breast, heart surface, mesenteries, & surrounding organs such as kidneys & eyes ● functions ▪ energy storage ▪ thermal insulation ▪ heat production by brown fat ▪ protective cushion for some organs ▪ filling space & shaping body  Cartilage Connective Tissue ● relatively stiff connective tissue with a flexible rubbery matrix ● shapes & supports the nose & ear ● partially enclose the larynx (voice box), trachea (windpipe), & thoracic cavity ● produced by cells called chondroblasts, which secrete the matrix & surround themselves with it until they become trapped in little cavities called lacunae ● once enclosed in lacunae, the cells are called chondrocytes (mature) ● rarely  exhibits  blood  vessels; nutrition & waste removal depends on solute diffusion ● matrix is rich in glycosaminoglycans & collagen fibers ● types of tissue: hyaline, elastic, & fibrocartilage   Hyaline Cartilage ● microscopic appearance ▪ clear, glassy matrix, often stained light blue or pink in tissue sections ▪ fine, dispersed collagen fibers, not usually visible ▪ chondrocytes  enclosed in lacunae, often in small clusters of 3-4 cells (cell nests) ▪ usually covered by perichondrium ● representative locations ▪ thin  articular  cartilage,  lacking  perichondrium,  over  the  ends  of  bones  at  moveable joints,  supportive  rings  &  plates around  trachea & bronchi, boxlike enclosure around the larynx, much of the fetal skeleton, & a costal cartilage attaches the end of a rib to the breastbone ● functions

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eases joint movement holds airway open during respiration moves vocal cords during speech a precursor of a bone in the fetal skeleton growth zones of long bones in children

 Elastic Cartilage ● microscopic appearance ▪ elastic fibers from weblike mesh amid lacunae ▪ always covered by perichondrium ● representative locations ▪ external ear & epiglottis ● functions ▪ provides flexible, elastic support  Fibrocartilage ● microscopic appearance ▪ parallel collagen fibers similar to those of tendon ▪ rows of chondrocytes in lacunae between collagen fibers ▪ never has perichondrium ● representative locations ▪ pubic symphysis (anterior joint between 2 halves of pelvic girdle), intervertebral discs (seperate bones of vertebral column), menisci (pads of shock-absorbing cartilage) in knee joint, & at points where tendons insert on bones near articular hyaline cartilage ● functions ▪ resists compression & absorbs shock in some joints ▪ often a transitional tissue between dense connective tissue & hyaline cartilage  Bone Connective Tissue ● two forms: ▪ spongy bone: calcified & hard, but silvers & plates give spongy appearance; fills the heads of long bones & forms middle layer of flat bones such as sternum & cranial bones ▪ compact (dense) bone: dense calcified tissue with no spaces visible; forms external surfaces of all bones, including spongy bone ● compact bone arranged in cylinders of tissue that surround central ( haversian or osteonic) canals which run longitudinally through shafts of long bones ● bone matrix deposited in concentric lamellae, which are onionlike layers around each central canal ● a central canal & its surrounding lamellae are called an o  steon ● tiny lacunae between lamellae are occupied by mature bone cells, or osteocytes ● delicate canals called canaliculi radiate from each lacuna to its neighbors ● whole bone is covered with a tough fibrous periosteum 

 Compact Bone Connective Tissue ● microscopic appearance ▪ calcified matrix arranged in concentric lamellae around central canals ▪ osteocytes in lacunae between adjacent lamellae ▪ lacunae interconnected by delicate canaliculi ● representative locations ▪ skeleton ● functions ▪ physical support of the body ▪ leverage for muscle action ▪ protective enclosure of viscera ▪ reservoir of calcium & phosphorus  Blood Connective Tissue ● microscopic appearance ▪ erythocytes (red blood cells) appear as pale pink dics with light centers & no nuclei ▪ leukocytes (white blood cells) are slightly larger, much fewer, & have variously shaped nuclei, usually stained violet ▪ platelets are cell fragments with no nuclei ● representative locations ▪ contained in heart & blood vessels ● functions ▪ transports gases, nutrients, wastes, chemical signals, & heat throughout body ▪ provides defensive leukocytes ▪ contains clotting agents to minimize bleeding ▪ platelets secrete growth factors that promote tissue maintenance & repair  Skeletal Muscle Tissue ● microscopic appearance ▪ long, threadlike, unbranched cells (fibers) relatively...