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Tissues Chapter 3. Histology Study of tissues (approximately 220 types!) Tissues: groups of highly specialized cells performing functions that benefit.

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Presentation on theme: "Tissues Chapter 3. Histology Study of tissues (approximately 220 types!) Tissues: groups of highly specialized cells performing functions that benefit."— Presentation transcript:

1 Tissues Chapter 3

2 Histology Study of tissues (approximately 220 types!) Tissues: groups of highly specialized cells performing functions that benefit the organism as a whole –Cells must be similar in structure & function and come from similar embryonic origin Four Primary tissue types –Epithelium (covering) –Connective (support) –Muscle (movement) –Nervous (control) Organs contain several tissue types, and arrangement of tissues determines organ’s structure & function

3 Primary Germ Layers All tissues & organs of the body develop from one of three primary germ layers: –Ectoderm (outside) Lining, skin, nervous –Endoderm (inside) Organs, mucosae & glands, linings of cavities and tracts –Mesoderm (middle) Connective tissue (i.e. blood, bone) and most muscle tissue

4 Extracellular Materials ECF: usually fluid, but can be more gel-like or calcified (i.e. bone) ECF provides a medium for: –Dissolving & mixing solutes –Transporting substances –Carrying out chemical reactions

5 Epithelial Tissue a.k.a. epithelium (“epithe” = laid on, covering) Lining, covering, and glandular tissue of the body Covers all free body surfaces and contains versatile cells Nearly all substances that the body gives off or receives must pass through epithelium Functions: –Protection –Filtration –Absorption –Secretion

6 Characteristics of Epithelium Cells fit closely together to form continuous sheets – single or multiple layers (desmosomes & tight junctions); little extracellular materials Membranes always have one free (unattached) surface or edge (apical surface) that is exposed to body’s exterior or to the cavity of an internal organ (some have modifications like cilia or microvilli) Basal surface (lower) of epithelium rests on a basement membrane – structureless material secreted by both epithelial cells and connective tissue cells that border the epithelium Epithelial tissues have no blood supply of their own (avascular) and depend on diffusion from the capillaries in underlying connective tissue for food and oxygen Regenerate easily (high mitotic rate) Have a nerve supply Derived from all three primary germ layers

7 Motion Induced Blindness Motion, your mind, and a myriad of shapes team up to rob you of your sight! Simply stare at the dot in the middle of the screen and see what happens. Don't worry, there are no lasting side effects... We think.

8 Classification of Epithelium Two names: –1 st indicates relative number of cell layers Simple (one layer) or stratified (multiple layers) or pseudostratified (looks like multiple layers) –2 nd indicates the shape of its cells Squamous (flat) Cuboidal (cube) Columnar (shaped like columns) Transitional (varies) Stratified epithelium is named based on cells at the free surface! Arrangement reflects location and function

9 Types of Epithelial Tissue Covering & Lining Epithelium –Simple Epithelia Simple squamous epithelium Simple cuboidal epithelium Simple columnar epithelium Pseudostratified columnar epithelium –Stratified Epithelia Stratified squamous epithelium Stratified cuboidal epithelium Stratified columnar epithelium Transitional epithelium Glandular Epithelium

10 Epithelial Tissue ID Quiz Tissues you need to be able to identify: Simple squamous Simple cuboidal Simple columnar Stratified squamous Transitional Pseudostratified Tissue/ cell parts you need to know: Nucleus Apical (free) surface Basal surface Basement membrane Cilia Goblet cell Keratin

11 Simple Squamous Epithelium Single layer, flat shape All cells attached to basement membrane Fit closely together Forms membranes where filtration or exchange of substances by rapid diffusion occurs (absorption, secretion, filtration) Ex: air sacs of lungs (O 2 & CO 2 exchanged), walls of capillaries (nutrients and gases pass between the tissue cells and blood in capillaries), form serous membranes (serosae) – slick membranes that line ventral body cavity and cover organs in that cavity Endothelium – lines blood vessels Mesothelium – lines body cavities and mesenteries

12 Simple Cuboidal Epithelium Single layer/cube shape Common in glands and their ducts Ex. Salivary glands and pancreas, walls of kidney tubules, covers surface of ovaries Tubule lining – longitudinal cut Tubule lining – cross-section

13 Simple Columnar Epithelium Single layer/column (tall) shape Often have goblet cells – produce lubricating mucus Ex: lines entire length of digestive tract from stomach to anus Mucosae (mucous membranes): epithelial membranes that line body cavities open to the body exterior

14 Pseudostratified Columnar Epithelium Appear to be multi-layered, but are actually one single layer that rest on the basement membrane Nuclei appear at different heights and some cells shorter than others Mainly functions in absorption and secretion Can be ciliated (pseudostratified ciliated columnar epithelium) Also can have goblet cells Ex: respiratory tract – mucus produced by goblet cells in this epithelium traps dust and other debris, and the cilia propel the mucus upward and away from the lungs

15 Stratified Squamous Epithelium Multiple layers, flat shape Most common stratified epithelium in body Cells at free edge are squamous, and those close to basement membrane can be cuboidal or columnar Found in sites that receive a good deal of abuse or friction Keratin – protein coating on apical surface (i.e. skin) –Can be keratinized or non-keratinized Ex. Esophagus, mouth, outer portion of skin Non-keratinized Keratinized

16 Stratified Cuboidal Epithelium Two cell layers with (at least) the surface cells being cuboidal in shape Fairly rare in body; distribution extremely limited Mainly in ducts of large glands (larger ducts of mammary glands, sweat and salivary glands, pancreas)

17 Stratified Columnar Epithelium Multiple layers/Columnar cells Basal cells vary in size and shape, see multiple nuclei Even less common in body; distribution extremely limited Mainly in ducts of large glands Ex. Urethra, pharynx

18 Transitional Epithelium Variable shapes Highly modified, sratified squamous epithelium that forms the lining of only a few organs –Urinary bladder, ureters, and part of the urethra Subject to considerable stretching Cells of basal layer cuboidal or columnar & cells at free surface vary in appearance Not stretched: superficial cells rounded and domelike Distended: epithelium thins and surface cells flatten and become squamouslike Distended

19 Glandular Epithelium Gland: one or more cells that make and secrete a particular product Secretion: typically contains protein molecules in an aqueous fluid Endocrine glands: ductless glands; secretions (hormones) diffuse directly into the blood vessels that weave through the glands (i.e. thyroid, adrenals, pituitary) Exocrine glands: ducts; secretions empty through ducts to epithelial surface (i.e. sweat & oil glands, liver, pancreas)

20 Face/Candlestick Illusion This is an image of two people about to make out. Or, it's a nice all-white candlestick. If you're a people person, you're likely to think it's the former, whereas aesthetically-minded domestic types will want to see an inanimate object perfect for the dinner table. Either way, those folks sure have big foreheads and that candlestick hold sure is awfully wide!

21 Connective Tissue Connects body parts Found everywhere in body Most abundant and widely distributed tissue Primary functions: –Protecting –Supporting –Binding together body tissues

22 Connective Tissue Characteristics Three basic elements: cells, ground substance, fibers –Extracellular matrix: ground substance + fibers Fibers made of protein (collagen is most abundant protein in body – 25%) No free surface (connects!) Has nerve supply (except cartilage) Highly vascular –except cartilage (avascular) & tendon (poorly vascularized) Matrix may be fluid, semifluid, gelatinous, fibrous, or calcified (depends on ground substance) –Secreted by connective tissue cells & adjacent cells –ground substance: structureless; water plus some adhesion proteins & large, charged, polysaccharide molecules –Determines tissue’s qualities

23 Embryonic Origin Mesenchyme: undifferentiated connective tissue cells in embryo All Connective tissue is derived from mesoderm!! –How is this different from Epithelial tissue?

24 Embryonic Connective Tissue Embryo (0-2 months); Fetus (2 mos.-birth) Mesenchyme: almost exclusively in embryo; tissue from which all connective tissue will eventually arise Mucous (Wharton’s Jelly): umbilical cord of fetus – gives support

25 Connective Tissue Cells Mesenchymal cells become blast cells (immature) Blast cells undergo mitosis and secrete the matrix Mature cells do not divide & make matrix – just maintain what is there

26 Connective Tissue Fibers Type of fiber depends on type of tissue Fibers made of proteins Types of fibers: –Collagen fibers – tough & resistant to stretching/pulling forces; bone, cartilage, tendons, ligaments –Elastic fibers – strength & stretching; skin, blood vessels, lungs (smaller than collagen fibers) –Reticular fibers – collagen + glycoprotein; support in blood vessel walls & form strong supporting network around fat cells, nerve fibers, skeletal/smooth muscle fibers; form basement membrane and framework of soft organs

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28 Types of Connective Tissue All CT consist of living cells surrounded by a matrix Differences: special cell types, fiber types, # of fibers Types: Bone (Osseous) Cartilage Hyaline cartilage Fibrocartilage Elastic cartilage Dense Connective Dense regular Dense irregular Dense elastic Loose Connective Loose areolar Adipose Loose reticular Blood

29 Connective Tissue ID Quiz Tissue types: Loose areolar Adipose Dense connective Cartilage Bone Blood Parts: Fibroblast Fibers Nucleus Adipocyte Lipids (fats) Chondrocyte Lacuna(e) Osteocyte Canaliculi Haversian system (osteon) Red blood cell (erythrocyte) White blood cell (leukocyte) Platelet (thrombocyte)

30 Bone (Osseous Tissue) composed of osteocytes (bone cells) sitting in lacunae (pits) Surrounded by layers of very hard matrix of calcium salts & collagen fibers Exceptional ability to protect & support other body organs –Great strength & some flexibility Movement, storing minerals, houses blood-forming tissue, stores lipids (yellow marrow) Parts: –haversian system (osteon) – basic unit –canaliculi – small canals that supply nutrients –central canal – contains blood vessels and nerves –Periosteum surrounds central canal – made of dense irregular CT –Lamellae – rings of matrix (mineral salts & collagen) p. 139 – Bone chapter

31 Cartilage Less hard and more flexible than bone Chondrocyte: cartilage cells Hyaline cartilage (most widespread) –Abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance –Supporting structures of larynx (voice box), attaches ribs to the breastbone, and covers the ends of many bones where they form joints –Makes up the fetal skeleton –Epiphyseal (growth) plates in long bones during youth Fibrocartilage –Highly compressible, forms the cushionlike disks between the vertebrae of the spinal column Elastic Cartilage –Found in structures with elasticity –Supports external ear

32 Hyaline Cartilage No blood vessels (except perichondrium)

33 Fibrocartilage Bundles of collagen in matrix Pubic symphysis, intervertebral discs, meniscus of knee Support & fusion No perichondrium Strongest type: strength & rigidity

34 Elastic Cartilage Threadlike fibers in gel matrix Support & maintains shape Has perichondrium Similar to hyaline, but more elastic fibers –Strength & exceptional stretchability Epiglottis (“lid” on larynx), auditory tubes

35 Dense Connective Tissue Also called dense fibrous tissue Collagen fibers are main matrix element Fibroblasts (fiber-forming cells) manufacture the building blocks of the fibers Forms long, ropelike structures –Tendons: attach skeletal muscles to bones –Ligaments: connect bones to bones at joints (contain more elastic fibers than tendons) Also makes up lower layers of skin (dermis) Types: –Dense Regular –Dense Irregular –Dense Elastic

36 Dense Regular Connective Tissue Closely packed bundles of collagen fibers running in same direction – fibers regular and parallel Great resistance to tension Crowded between collagen fibers are fibroblasts that make fibers & ground substance Found in tendons, ligaments, aponeuroses, and fascia

37 Dense Irregular Connective Tissue Randomly arranged collagen fibers & few fibroblasts Fascia, dermis of skin, periosteum, perichondrium, joint capsules, membrane capsules around organs, heart valves Provides strength Places where pulling in various directions occurs (found in sheets) Same structural elements as dense regular, just arranged irregularly and with thicker fibers

38 Dense Elastic Connective Tissue Elastic fibers & fibroblasts Allows stretching of various organs and elasticity (returns to original shape) Lungs, walls of trachea, arteries, bronchial tubes, true vocal cords, and some ligaments

39 Loose Connective Tissue Softer, more cells and fewer fibers than any other connective tissue type (*except blood) Types: –Areolar Tissue –Adipose Tissue –Reticular Connective Tissue

40 Loose Areolar Connective Tissue All three types of fibers, semi-fluid ground substance, several cells Most widely distributed connective tissue Soft, pliable – cushions and protects body organs Universal packing tissue and connective tissue “glue” –Holds organs together and in proper positions Reservoir of water and salts for surrounding tissues –All cells obtain nutrients from & release wastes into this “tissue fluid” Edema: areolar tissue in area soaks up excess fluid when area is inflamed – area swells and becomes puffy Phagocytes scavenge for bacteria and debris and dead cells in this tissue to destroy

41 Adipose Tissue Commonly called fat Adipocytes: specialized to store triglycerides Droplet of oil occupies most of fat cell & compresses nucleus Subcutaneous tissue beneath skin – insulates body and protects from bumps and extremes of heat & cold Cushions individual organs and stores fat for fuel if needed Newborns – brown fat (rich blood supply & more mitochondria) –Helps them maintain body temperature

42 Loose Reticular Connective Tissue Made of reticular cells (resemble fibroblasts) & reticular fibers Limited to certain sites – forms “stroma” – internal framework that supports free blood cells (lymphocytes) in lymphoid organs (i.e. lymph nodes, liver, spleen, bone marrow) Binds together smooth muscle

43 Blood (Vascular Tissue) Plasma + formed elements (erythrocytes, leukocytes, thrombocytes) Blood plasma = nonliving, fluid matrix –“fibers” – soluble protein molecules that are visible only during blood clotting Transport vehicle for cardivoascular system –Carries nutrients, wastes & respiratory gases; immunity; clotting

44 Muscle Tissue Highly specialized to contract and produce movement Types of muscle tissue: –Skeletal Muscle –Cardiac Muscle –Smooth Muscle

45 Muscle & Nervous Tissue ID Quiz Tissue types: Skeletal muscle Cardiac muscle Smooth muscle Nervous tissue Parts: Nucleus Striations (bands) Intercalated disc Neuron Cell body Dendrite Axon Neuroglia

46 Skeletal Muscle Tissue Packaged by connective tissue sheets into organs Attached to bones Controlled movements/voluntary movements Muscular System Cells are long, cylindrical, multinucleate, have striations (stripes) Cells called “muscle fibers” because they are elongated Fibers run parallel to each other Function: Motion, maintenance of posture, heat production (maintaining temperature)

47 Cardiac Muscle Tissue Only in heart wall Function: pump and propel blood Involuntary Striations, uninucleate relatively short, branching cells that fit tightly together at intercalated discs (attach cells end to end) Contain gap junctions that allow ions to pass freely from cell to cell resulting in rapid conduction of electrical impulse across the heart

48 Smooth Muscle Tissue no striations visible Involuntary muscle Single nucleus, spindle-shaped (pointed at each end) Stomach, uterus, blood vessels, airways, walls of hollow organs (viscera) i.e. urinary & gall bladder –Contracts: cavity becomes smaller (constriction) –Relaxes: cavity dilates and enlarges (dilation) Peristalsis – wavelike motion keeps food moving through small intestine Contracts more slowly than other types

49 Nervous Tissue Internal communication Found in brain, spinal cord, and nerves Two types of cells: –Neurons: receive and conduct electrochemical impulses from one part of the body to another –Neuroglia: supporting cells that insulate, support, and protect delicate neurons within the structures of the nervous system

50 Neurons Receive & conduct electrochemical impulses Two functional characteristics: –Irritability –Conductivity Cytoplasm drawn out into long processes Parts: –Cell body – nucleus & organelles –Dendrites – processes that receive impulse –Axons – process(es) that send impulse

51 Neuroglia Supporting cells of the nervous tissue Don’t generate nerve impulse Often sites of tumors because they can divide Insulate, support, protect neurons

52 Tissue Repair (Wound Healing) Tissue injury stimulates the body’s inflammatory and immune responses and healing begins almost immediately Returning to homeostasis Tissue repair/wound healing occurs in two ways: –Regeneration – replacement of destroyed tissue by the same kind of cells (parenchyma cells – functioning cells of organ) –Fibrosis – repair by dense (fibrous) connective tissue (scar tissue) – (stroma – supporting cells of organ – connective tissue) –Which type depends on: Type of tissue damaged Severity of injury Different tissue types have different capacities for renewal of parenchyma cells –During embryonic development, muscle & nervous become highly differentiated and lose capacity for mitosis; epithelial and connective tissues general have a capacity for renewal

53 Tissue Repair (Wound Healing) 1.Inflammation –Nonspecific body response that tries to prevent further injury –Inflammatory chemicals are released and make capillaries permeable –Fluid with clotting proteins seep into injured area from blood –Clot is constructed to stop loss of blood and hold wound together –Scab forms where clot is exposed to air

54 Tissue Repair (Wound Healing) 2. Granulation Tissue –Delicate pink tissue composed largely of new capillaries –Grow into damaged area from undamaged blood vessels nearby –Fragile & bleed freely (i.e. when scab picked) –Contains phagocytes that dispose of blood clot –Contains connective tissue cells (fibroblasts) that produce the building blocks of collagen fibers (scar tissue) to permanently bridge the gap

55 Tissue Repair (Wound Healing) 3. Regeneration & Fibrosis –Surface epithelium regenerates across the granulation tissue below the scab –Scab detaches when surface epithelium has covered wound –Fibrosis (scar) usually underneath regenerated epithelium Scar Tissue: strong, lacks flexibility, in ability to perform normal tissue functions Adhesions can result from fibrosis and cause abnormal joining of adjacent tissue (recent surgery sites) – can cause obstructions (abdomen)

56 Tissue Repair (Wound Healing) Tissue repair can be affected by: –Nutrition –Blood circulation Transport of oxygen, nutrients, antibodies, etc. Removal of tissue fluids, bacteria, and debris –Age Young are better nutritionally Better blood supply Cells have higher metabolic rate Cells & extracellular components change with age Collagen/elastic fibers change with age


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