4 The Tissue Level of Organization

1. 4 The Tissue Level of Organization

2. An Introduction to Tissues Tissues Structures with discrete structural and functional properties Tissues in combination form organs, such as the heart or liver Organs can be grouped into 11 organ systems

3. 4-1 Four Types of Tissue • Tissue • Are collections of cells and cell products that perform specific, limited functions • Four types of tissue • Epithelial tissue • Connective tissue • Muscle tissue • Neural tissue

4. 4-1 Four Types of Tissue • Epithelial Tissue • Covers exposed surfaces • Lines internal passageways • Forms glands • Connective Tissue • Fills internal spaces • Supports other tissues • Transports materials • Stores energy

5. 4-1 Four Types of Tissue • Muscle Tissue • Specialized for contraction • Skeletal muscle, heart muscle, and walls of hollow organs • Neural Tissue • Carries electrical signals from one part of the body to another

6. 4-2 Epithelial Tissue • Epithelia • Layers of cells covering internal or external surfaces • Glands • Structures that produce secretions

7. 4-2 Epithelial Tissue • Characteristics of Epithelia • Cellularity (cell junctions) • Polarity (apical and basal surfaces) • Attachment (basement membrane or basal lamina) • Avascularity • Regeneration

8. Figure 4-1 The Polarity of Epithelial Cells Cilia Microvilli Apicalsurface Golgiapparatus Nucleus Mitochondria Basement membrane Basolateralsurfaces

9. 4-2 Epithelial Tissue • Functions of Epithelial Tissue • Provide Physical Protection • Control Permeability • Provide Sensation • Produce Specialized Secretions (glandular epithelium)

10. 4-2 Epithelial Tissue • Specializations of Epithelial Cells • Move fluids over the epithelium (protection) • Move fluids through the epithelium (permeability) • Produce secretions (protection and messengers) • Polarity • Apical surfaces • Microvilli increase absorption or secretion • Cilia (ciliated epithelium) move fluid • Basolateral surfaces

11. 4-2 Epithelial Tissue • Maintaining the Integrity of Epithelia • Intercellular connections • Attachment to the basement membrane • Epithelial maintenance and repair

12. 4-2 Epithelial Tissue • Intercellular Connections • Support and communication • CAMs (cell adhesion molecules) • Transmembrane proteins • Intercellular cement • Proteoglycans • Hyaluronan (hyaluronic acid) • Glycosaminoglycans

13. 4-2 Epithelial Tissue • Intercellular Connections • Cell junctions • Form bonds with other cells or extracellular material • Tight junctions • Gap junctions • Desmosomes

14. 4-2 Epithelial Tissue • Tight Junctions • Between two plasma membranes • Adhesion belt attaches to terminal web • Prevents passage of water and solutes • Isolates wastes in the lumen

15. 4-2 Epithelial Tissue • Gap Junctions • Allow rapid communication • Are held together by channel proteins (junctional proteins, connexons) • Allow ions to pass • Coordinate contractions in heart muscle

16. 4-2 Epithelial Tissue • Desmosomes • CAMs, dense areas, and intercellular cement • Spot desmosomes • Tie cells together • Allow bending and twisting • Hemidesmosomes • Attach cells to the basal lamina

17. 4-2 Epithelial Tissue • Attachment to the Basement Membrane • Clear layer (lamina lucida) • Thin layer • Secreted by epithelia • Barrier to proteins • Dense layer (lamina densa) • Thick fibers • Produced by connective tissue • Strength and filtration

18. Figure 4-2 Cell Junctions Interlockingjunctionalproteins Tight junction Tight junction Adhesion belt Terminal web Spotdesmosome Adhesion belt Gapjunctions Hemidesmosome Embedded proteins(connexons) Intermediatefilaments Clearlayer Basementmembrane Denselayer Dense area Cell adhesionmolecules (CAMs) Proteoglycans

19. Figure 4-2a Cell Junctions Tight junction Adhesion belt Terminal web Spotdesmosome Gapjunctions Hemidesmosome This is a diagrammatic view of an epithelial cell,showing the major types of intercellularconnections.

20. Figure 4-2b Cell Junctions Interlockingjunctionalproteins Tight junction Terminal web Adhesion belt A tight junction is formed by the fusion of the outer layers of two plasma membranes. Tight junctions prevent the diffusion of fluids and solutes betweenthe cells. A continuous adhesion belt lies deep to the tight junction. This belt is tied to the microfilaments of the terminal web.

21. Figure 4-2c Cell Junctions Embedded proteins(connexons) Gap junctions permit the free diffusion of ions and small molecules between two cells.

22. Figure 4-2d Cell Junctions Intermediatefilaments Cell adhesionmolecules (CAMs) Dense area Proteoglycans A spot desmosome tiesadjacent cells together.

23. Figure 4-2e Cell Junctions Clearlayer Basementmembrane Denselayer Hemidesmosomes attach a cell to extracellular structures, such as the protein fibers in the basement membrane.

24. 4-2 Epithelial Tissue • Epithelial Maintenance and Repair • Epithelia are replaced by division of germinative cells (stem cells) • Near basement membrane

25. 4-3 Classification of Epithelia • Singular = Epithelium; Plural = Epithelia • Classes of Epithelia • Based on shape • Squamous epithelia — thin and flat • Cuboidal epithelia — square shaped • Columnar epithelia — tall, slender rectangles • Based on layers • Simple epithelium — single layer of cells • Stratified epithelium — several layers of cells

26. Table 4-1 Classifying Epithelia

27. Table 4-1 Classifying Epithelia

28. 4-3 Classification of Epithelia • Squamous Epithelia • Simple squamous epithelium • Absorption and diffusion • Mesothelium • Lines body cavities • Endothelium • Lines heart and blood vessels

29. Figure 4-3a Squamous Epithelia Simple Squamous Epithelium LOCATIONS: Mesothelia lining ventral body cavities; endothelia lining heartand blood vessels; portions of kidney tubules (thin sections of nephron loops); inner lining of cornea; alveoli of lungs FUNCTIONS: Reduces friction; controls vessel permeability; performsabsorption and secretion Cytoplasm Nucleus Connective tissue LM  238 Lining of peritoneal cavity

30. 4-3 Classification of Epithelia • Squamous Epithelia • Stratified squamous epithelium • Protects against attacks • Keratin protein adds strength and water resistance

31. Figure 4-3b Squamous Epithelia Stratified Squamous Epithelium LOCATIONS: Surface of skin; lining of mouth, throat, esophagus, rectum, anus, and vagina FUNCTIONS: Provides physical protection against abrasion, pathogens, and chemical attack Squamoussuperficial cells Stem cells Basementmembrane Connectivetissue Surface of tongue LM  310

32. 4-3 Classification of Epithelia • Cuboidal Epithelia • Simple cuboidal epithelium • Secretion and absorption • Stratified cuboidal epithelia • Sweat ducts and mammary ducts

33. Figure 4-4a Cuboidal and Transitional Epithelia Simple Cuboidal Epithelium LOCATIONS: Glands; ducts;portions of kidney tubules; thyroidgland Connectivetissue FUNCTIONS: Limited protection,secretion, absorption Nucleus Cuboidalcells Basementmembrane Kidney tubule LM  650

34. Figure 4-4b Cuboidal and Transitional Epithelia Stratified Cuboidal Epithelium LOCATIONS: Lining of some ducts(rare) FUNCTIONS: Protection, secretion,absorption Lumenof duct Stratifiedcuboidalcells Basementmembrane Nuclei Connectivetissue Sweat gland duct LM  500

35. 4-3 Classification of Epithelia • Transitional Epithelium • Tolerates repeated cycles of stretching and recoiling and returns to its previous shape without damage • Appearance changes as stretching occurs • Situated in regions of the urinary system (e.g., urinary bladder)

36. Figure 4-4c Cuboidal and Transitional Epithelia Transitional Epithelium LOCATIONS: Urinarybladder; renal pelvis;ureters FUNCTIONS: Permitsexpansion and recoilafter stretching Epithelium(relaxed) Basement membrane Connective tissue andsmooth muscle layers LM  400 Empty bladder Epithelium(stretched) Basement membrane LM  400 Connective tissue andsmooth muscle layers LM  400 Full bladder Urinary bladder

37. 4-3 Classification of Epithelia • Columnar Epithelia • Simple columnar epithelium • Absorption and secretion • Pseudostratified columnar epithelium • Cilia movement • Stratified columnar epithelium • Protection

38. Figure 4-5a Columnar Epithelia Simple Columnar Epithelium LOCATIONS: Lining ofstomach, intestine, gallbladder,uterine tubes, and collectingducts of kidneys Microvilli Cytoplasm FUNCTIONS: Protection,secretion, absorption Nucleus Basementmembrane Looseconnective tissue LM  350 Intestinal lining

39. Figure 4-5b Columnar Epithelia Pseudostratified Ciliated Columnar Epithelium LOCATIONS: Lining ofnasal cavity, trachea, andbronchi; portions of malereproductive tract Cilia Cytoplasm FUNCTIONS: Protection,secretion, move mucuswith cilia Nuclei Basementmembrane Looseconnective tissue Trachea LM  350

40. Figure 4-5c Columnar Epithelia Stratified Columnar Epithelium LOCATIONS: Small areas ofthe pharynx, epiglottis, anus,mammary glands, salivarygland ducts, and urethra Looseconnective tissue Deeper basalcells FUNCTION: Protection Superficialcolumnar cells Lumen Lumen Cytoplasm Nuclei Basementmembrane Salivary gland duct LM  175

41. 4-3 Classification of Epithelia • Glandular Epithelia • Endocrine glands • Release hormones • Into interstitial fluid • No ducts • Exocrine glands • Produce secretions • Onto epithelial surfaces • Through ducts

42. 4-3 Classification of Epithelia • Glandular Epithelia • Modes of Secretion • Merocrine secretion • Apocrine secretion • Holocrine secretion

43. 4-3 Classification of Epithelia Merocrine Secretion Produced in Golgi apparatus Released by vesicles (exocytosis) For example, sweat glands Apocrine Secretion Produced in Golgi apparatus Released by shedding cytoplasm For example, mammary glands

44. 4-3 Classification of Epithelia Holocrine Secretion Released by cells bursting, killing gland cells Gland cells replaced by stem cells For example, sebaceous glands

45. Figure 4-6 Modes of Glandular Secretion Secretoryvesicle Golgiapparatus Nucleus TEM  3039 Salivary gland Breaksdown Mammary gland Golgi apparatus Secretion Regrowth Hair Sebaceousgland Cells burst, releasingcytoplasmic contents Hair follicle Cells produce secretion,increasing in size Cell division replaceslost cells Stem cell

46. Figure 4-6a Modes of Glandular Secretion Secretoryvesicle Salivary gland Golgiapparatus Nucleus Mammary gland TEM  3039 Merocrine. In merocrine secretion, secretory vesicles are discharged at the apical surface of the gland cell by exocytosis. Hair Sebaceousgland Hair follicle

47. Figure 4-6b Modes of Glandular Secretion Salivary gland Breaksdown Mammary gland Golgi apparatus Secretion Regrowth Apocrine. Apocrine secretion involves the loss of apical cytoplasm. Inclusions, secretory vesicles, and other cytoplasmiccomponents are shed in the process. The gland cell then undergoes growth and repair before it releases additional secretions. Hair Sebaceousgland Hair follicle

48. Figure 4-6c Modes of Glandular Secretion Salivary gland Cells burst, releasingcytoplasmic contents Mammary gland Cells produce secretion,increasing in size Cell division replaceslost cells Stem cell Hair Holocrine. Holocrine secretion occurs as superficial gland cells burst. Continued secretion involves the replacement of these cells through the mitotic division of underlying stem cells. Sebaceousgland Hair follicle

49. 4-3 Classification of Epithelia • Glandular Epithelia • Types of Secretions • Serous glands • Watery secretions • Mucous glands • Secrete mucins • Mixed exocrine glands • Both serous and mucous

50. 4-3 Classification of Epithelia • Glandular Epithelia • Gland Structure • Unicellularglands • Mucous (goblet) cells are the only unicellular exocrine glands • Scattered among epithelia • For example, in intestinal lining