Tissues : The living fabric Chapter 4

1. Tissues : The living fabricChapter 4

2. Histology = the study of tissues • Tissues: • groups of cells which are similar in structure and which perform common or related functions

3. Four Basic Kinds of Tissues • Epithelial Tissue (protection) • Connective Tissue (support) • Muscle Tissue (movement) • Nervous Tissue (control)

4. Epithelial Tissue • Locations: • covers the body • lines the cavities, tubes, ducts and blood vessels inside the body • covers the organs inside body cavities

5. Epithelial Tissue Functions: • Protection from physical & chemical injury • Protection against microbial invasion • Contains receptors which respond to stimuli • Filters, secretes & reabsorbs materials • Secretes serous fluids to lubricate structures. • SUMMARY: protection, absorption, filtration and secretion

6. Special characteristics of epithelium • Cellularity – cells close together • Specialized contacts – tight junctions and desmosomes • Polarity – one free surface exposed to body exterior or internal cavity • Avascularity – no blood vessels • Basement membrane – nonliving, adhesive that reinforces • Regeneration – high capacity

8. Classification of epithelial shapes: • squamous – flattened and sac like • cuboidal – as tall as they are wide • columnar – tall and column shaped Classification of epithelial layers present: • simple – single layer of cells • stratified – multiple cell layers

10. Simple Squamous Epithelium • Simple – one cell thick • Forms solid layer of cells which line blood vessels, body cavities & cover organs in body cavities

12. Stratified Squamous Epithelium • Stratified – multiple layers • Forms epidermis

14. Duct Simple Cuboidal Epithelium Cuboid Cells • Simple – one cell thick • Roughly cube shaped • Line ducts in kidneys, etc, where reabsorption and secretory activities take place.

16. Duct Stratified Cuboidal Epithelium • two layers cube like cells • Ducts of sweat glands, mammary and salivary glands Cuboid Cells

18. Simple Columnar Epithelium • Simple – one cell thick • Column shaped (long & narrow) • Line digestive tract where re-absorption & secretion occurs.

20. Stratified Columnar Epithelium • Several cell layers • Basal cells usually cuboidal; superficial cells long and columnar; may bear cilia • RARE – small amounts at epithelial junctions (stomach-esophagus)

22. Pseudostratified Epithelium • Single layer of cells of differing heights. • May bear cilia – found in trachea & upper respiratory tract • Non ciliated – ducts of large glands, male urethra

24. Transitional Epithelium • Surface cells dome shaped or squamous • Basal cells cuboidal or columnar • Stretches readily • Location: lines ureters, bladder, urethra

25. Transitional Epithelium

26. Other......... Goblet cells = specialized cells within some epithelial tissues that secrete mucus (example: epithelium lining the digestive and respiratory tracts)

27. Cilia = hair-like extensions from the cell that beat back and forth uniformly to move mucus along the surface of the epithelium Microvilli = finger like cell projections that cover the surface of small intestinal epithelium and function to increase surface area for absorption

28. Classifying epithelia by location • Endothelium – simple epithelial sheet composed of a single layer of squamous cells attached to a basement membrane • Permeable and thin • Lines all hollow circulatory system organs: lymphatic vessels, blood vessels, heart

29. Epithelial membranes • Continous multi-cellular sheet composed of at least two tissue types: epithelium bound to underlying connective tissue • Called “simple organs” • 3 types: mucous, cutaneous, serous

30. Mucous membrane • Line body cavities that are open to the exterior (digestive, respiratory, urogenital) • Contain stratified squamous or simple columnar epithelium • Adapted for absorption and secretion • Wet or moist membranes

31. Cutaneous membrane • Your skin • Dry membrane, exposed to air • Consists of stratified squamous epithelium (epidermis) firmly attached to a thick connective tissue layer (dermis)

32. Serous membrane • Moist membrane found in closed ventral body cavities • Simple squamous epithelium (mesothelium) resting on a tiny amount of loose connective tissue • Parietal layer – lines cavity wall • Visceral layer – covers outer surface of organ • Secrete thin layer of serous fluid – lubricates and prevents organs from sticking together

33. Serous membrane (cont.) • Pleura – encloses lungs • Pericardium – encloses heart • Peritoneum – abdominopelvic cavity and viscera (internal organs)

34. Glandular epithelia • Gland= one or more cells that produce and secrete a particular product (endocrine or exocrine) • the product is called a secretion (water based fluid typically containing proteins) • Secretion is also a process – glands take needed substances from the blood and chemically transform them into their secretory product

35. Endocrine glands • Eventually lose their ducts • Produce hormones which are secreted directly into the extracellular spaceand then enter the blood or lymphatic fluid • Covered more in Ch. 17

36. Exocrine glands • More numerous than endocrineglands • Sweat & oil glands, salivary glands, liver (secretes bile), pancreas (digestive enzymes), mammary glands, mucous glands

37. Exocrine glands can be: • Unicellular– no ducts, produce mucin which forms a slimy coating (mucus) for protection/lubrication; ex: goblet cells found in trachea & digestive tract • Multicellular - secrete their products through a duct onto body surfaces or into body cavities

38. End of epithelial tissue

39. Connective Tissue • Most abundant & widely distributed tissue • Functions: • Connects, binds and supports structures • Tendons, ligaments, etc. • Protects & cushions organs and tissues • Insulates (fat) • Transports substances (blood)

40. Connective tissue common characteristics: • Common origin – all arise from mesenchyme (embryonic tissue) • Different degrees of vascularity(avascular to highly vascular) • Matrix – composed largely of non-living extracellular matrix, which separates living cells • Allows connective tissue to bear weight, withstand tension, endure physical trauma and abrasion

41. Structural elements • Ground substance – unstructured material that fills the space between cells and contains fibers • Fibers - 3 types • collagen (most abundant) • elastic • reticular

42. Cells – each class has a fundamental cell type • Immature form = suffix “-blast” • Mature form = suffix “-cyte” • Fibroblasts (connective tissue proper) • chondroblasts (cartilage) • osteoblasts (bone) • hemocytoblast (blood)

43. Macrophages • large, irregulary shaped • phagocytize both foreign matter (immune system) and dead tissue cells • May be fixed or migrate freely • Not limited to connective tissue

44. Specific Connective Tissue Types: • Mesenchyme • Areolar • Adipose • Reticular • Dense regular & irregular • Elastic • Hyalaine cartilage • Fibrocartilage • Elastic cartilage • Bone • Blood Loose connective tissues dense connective tissues

45. Connective tissue proper • 2 subclasses • Loose connective tissues – areolar, adipose, and reticular • Dense connective tissues – dense regular, dense irregular and elastic

46. Mesenchyme • Found in embryo • Gives rise to all other connective tissue

47. Gel-like matrix with fibers (all 3 types) running in random directions and scattered cells of various types • distributed under epithelia - in mucous membranes, around organs and capillaries Areolar • Wraps and cushions organs, role in inflamation, holds and conveys fluid

48. Adipose • Location: under skin, around kidneys, eyeballs, in bones, w/in abdomen, in breasts • Honeycomb or chickenwire appearance • Nucleus pushed to the side & large internal fat droplet • Function: • stores energy (fat) – reserve fuel • Insulates against heat loss • supports & protects organs

49. Reticular • Network of reticular fibers in loose ground substance w/reticular cells • Location: liver, lymph nodes, bone marrow, spleen Function: body protection (phagocytic); fibers support other cell types

50. Dense Regular • Primarily parallel collagen fibers; few elastin; fibroblasts • Withstands great stress; ligaments and tendons Dense Irregular • Irregularly arranged collagen/elastic fibers; fibroblasts • Dermis of skin, digestive tract, organs and joints • Withstands tension in many directions