Tissues Chapter 3

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 Ectoderm Mesoderm Endoderm

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

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8. Classification of Epithelium • Two names: • 1st indicates relative number of cell layers • Simple (one layer) or stratified (multiple layers) or pseudostratified (looks like multiple layers) • 2nd 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 (O2 & CO2 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 top view JayDoc LUMEN

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 apical surface basement membrane Tubule lining – cross-section Tubule lining – longitudinal cut

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 goblet cell basement membrane (basal surface) LUMEN

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 cilia cilia goblet cell LUMEN

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 apical surface keratin basal surface Keratinized Non-keratinized LUMEN

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 LUMEN

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) Colon

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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 Mesenchyme Mucous (Wharton's jelly)

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 osteocyte leukocyte chondroblast fibroblast Immature Mature adipocyte osteoblast

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

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. p. 139 – Bone chapter 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) Haversian system osteocyte canaliculi blood vessels (in lacuna) and nerves

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) lacuna containing chondrocyte

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

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 elastic fibers

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 fibroblast collagen fibers

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 fibroblast collagen 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 elastic fiber fibroblast

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 fiber cell

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 Nucleus lipids adipocyte

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 reticular fiber

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 erythrocyte leukocyte (red blood cell) (white blood cell) thrombocyte (platelet)

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) striation

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 Intercalated disc

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 Axon Dendrite Cell body