Understanding Tissue Types: The Living Fabric of the Body

1. Chapter 4 Tissue: The Living Fabric G.R. Pitts, Ph.D,J.R. Schiller, Ph.D. &James F. Thompson, Ph.D.

2. General • Tissues - groups of cells with similar basic structures which cooperate to perform a related function • Four basic types of tissues • Epithelial – linings for protection, coordination, synthesis, absorption, elimination • Connective – support • Muscle – for movement • muscle tissue is a highly specialized connective tissue • Nervous – for control and coordination • nervous tissue is a highly specialized epithelial tissue

3. Epithelial Tissue Characteristics • Cellularity - densely packed • Polarity • apical surface • basal surface (or basolateral) • Specialized contacts - tight junctions and desmosomes • Supported by connective tissue • basal lamina (epithelial “glue”) • reticular lamina (connective tissue “glue”) • basement membrane - reticular and basal laminae together • Innervated but avascular (no direct blood supply) • Regeneration – high capacity for regeneration

4. Classifying Epithelial Tissues Simple Stratified • By number of cell layers Pseudostratified epithelium (from the respiratory tree) appears stratified, but actually is a single layer of cells of varying heights; each cell touches the basement membrane

5. Classifying Epithelial Tissues Squamous Transitional Cuboidal Columnar • By cell shape

6. Glandular Epithelial Tissues • functions in secretion – a gland may be one cell or a group of specialized cells • two major types • exocrine glands have ducts leading to body surfaces • various products are synthesized and stored for release • secretions are secreted into the duct system • e.g., sweat glands, salivary glands, etc. • endocrine glands are ductless • hormones are synthesized and stored for release • hormones are secreted into the tissue fluid and then diffuse into the blood stream • e.g., thyroid and parathyroid glands

7. Exocrine Gland Classification • Unicellular glands • single cell glands • goblet cells

8. Exocrine Gland Classification • Multicellular glands • Structurally classified by duct configuration and by the shape of the secretory units • simple glands have a single duct • compound glands have branched ducts • Merocrine glands • Exocytosis • Holocrine glands • Cell rupture

9. Connective Tissue Characteristics • Two basic components • Cells – fewer, rarely touching, surrounded by a matrix • immature forms (-blasts) secrete the matrix and can still divide • once the matrix is secreted, the cells mature into -cytes which have decreased cell divisions and secrete less matrix material • chondro- cartilage, osteo- bone, fibro – connective, etc. • Extracellular Matrix • ground substance (gelatinous glycoproteins) • structural fibers (fibrous proteins, e.g., collagen, elastin, reticulin) • Common embryological origin (from mesoderm) • Innervated and Vascular (direct blood supply) • Cartilage is the one exception with no capillary beds

10. Connective Tissue Matrix • Ground Substance • supports cells, binds them together • may be solid, fluid, or gel • interstitial fluid • Glycoproteins called proteoglycans - large polysaccharide molecules bound to a protein core (like a bottle brush) • Hyaluronic acid – gelatinous, separates cells, traps extracellular fluid; lubricates joints; gives shape to eyeballs; fills body spaces • Chondroitin sulfate – capable of being mineralized; cartilage, bones, skin, blood vessels • Dermatin sulfate – harder; skin, tendons, blood vessels, heart valves • Keratin sulfate - still harder; bone, cartilage, cornea of the eyes

11. Connective Tissue Matrix • Protein fibers are embedded in the ground substance • Used for structural support, adhesion, and to connect cells • Provide strength and support • Collagen fibers • highly polymerized, gigantic molecules • tough, moderate flexibility • protein collagen - parallel bundles of fibers • bone, cartilage, tendons, ligaments • Elastic fibers (elastin) • branched; smaller, thinner fibers than collagen • Very flexible and elastic but also strong • can be stretched to 150% of its original length • require special stains to be seen • Reticular fibers • thin, less polymerized collagen fibers • require special stains to be seen

12. Types of Connective Tissues • Connective Tissue Proper • areolar (loose fibrous) connective tissue • adipose tissue • reticular connective tissue • dense (fibrous) regular connective tissue • dense (fibrous) irregular connective tissue • Cartilage • hyaline cartilage • elastic cartilage • fibrocartilage • Bone • Blood

13. Connective Tissue Types Classified by the characteristics of the matrix Also see Table 4.1 Details covered in lab

14. Connective Tissue Diseases • Many diseases • Most of them very rare • They may involve the joints but primarily affect other organs • Cause(s) of these diseases unknown • But in all of them, the immune system seems to be activated and causes damage to different organs in the body

15. Systemic Lupus Erythematosus http://www.niehs.nih.gov/health/topics/conditions/lupus/index.cfm • Symptoms: skin rash, mild arthritis, and generalized weakness or tiredness • Rarer symptoms: hair loss, mouth ulcers, headaches and poor circulation in the fingers • Serious complications of kidney, heart, and brain inflammation • 9 times more likely in women • 4 times more likely in African-Americans

16. Marfan Syndrome • Genetic defect on chromosome 15 that encodes the fibrilin protein

17. Nervous Tissue • Highly specialized epithelial cells • Convert stimuli into electro-chemical signals for transfer of information • Structure • cell body (soma) and extensions • dendrites (highly branched) – carry incoming signal • axon (long, usually single strand) – carry outgoing signal

18. Muscle Tissue Characteristics • a high degree of cellularity • cells contain contractile proteins • well vascularized • a highly specialized type of connective tissue

19. Classification of Muscle Tissues • two types are Striated: • Skeletal muscle • attached to bones • multinucleate • voluntary • fibers are parallel and cylindrical • Cardiac muscle • most of the heart wall • single nucleus (usually) • involuntary • branched cylinders connected by intercalated discs

20. Classification of Muscle Tissues • One type is non-striated • Smooth muscle • located in the walls of hollow organs: • blood vessels • digestive tract • airways • bladder • involuntary • single nucleus • spindle shaped

21. Epithelial Membranes A particular Epithelium and its underlying Connective Tissue support trachea skin

22. Cutaneous Membrane – The Skin

23. Mucous Membranes • Line body structures which open directly to the exterior • Viscous mucus secretions lubricate surfaces and provide a defensive barrier that traps particles and microbes

24. Serous Membranes • Line closed body cavities and their organs • Watery serous fluid lubricates the cavity and its organs • pleura – lungs • pericardium - heart • peritoneum - abdominal organs • parietal • visceral

25. Tissue Injury & Repair • Inflammation • redness • swelling • heat • pain • loss of function • Organization restores blood supply • Blood clot replaced by granulation tissue • Regeneration and Fibrosis • Epithelium regenerates • Fibrous conn. tissue matures and contracts

26. Tissue Repair • During development some cells lose their ability to divide with specialization • Some cells maintain the ability to replace others • Stem cells • immature, undifferentiated cells • hide in protected areas in skin/GI tract to replace cells • Tissue repair • new cells come from parenchyma (functioning portion) or stroma (connective tissue) • if parenchyma cells proliferate then repair nearly complete; if not, then we get scar tissue formation • fibroblasts will produce collagen and other matrix materials during fibrosis – a less functional tissue

27. Conditions Affecting Repair • Nutrition • adequate protein in the diet for repair • necessary vitamins and other nutrients • Blood circulation • transport oxygen, nutrients, antibodies and other defensive molecules and cells to the site • WBCs remove debris which would otherwise interfere with healing • Age • young people heal faster and have less obvious scars • young people have a better nutritional status, a better blood supply, and a higher metabolism

28. Embryonic Germ Layers We’ll see the embryonic tissues again in Chapter 28 next semester

29. End Chapter 4 Exam 1 covers Chapters 1-4

30. Connective Tissue Structure

31. Embryonic Structure