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TISSUES

TISSUES. STRUCTURAL ORGANIZATION. Life is characterized by hierarchical orders of organization Atoms Molecules Organelles Cells Tissues Organs Organ systems Organism (Population) (Community) (Ecosystem). STRUCTURAL ORGANIZATION.

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TISSUES

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  1. TISSUES

  2. STRUCTURAL ORGANIZATION • Life is characterized by hierarchical orders of organization • Atoms • Molecules • Organelles • Cells • Tissues • Organs • Organ systems • Organism • (Population) • (Community) • (Ecosystem)

  3. STRUCTURAL ORGANIZATION • The cell is the lowest level of organization that can live independently as an organism Amoeba Paramecium

  4. STRUCTURAL ORGANIZATION • In multicellular organisms, specialized cells are grouped into tissues • A tissue is a group of cells similar in structure and performing a common function • Organs are comprised of combinations of various tissues • Organ systems include multiple organs working together

  5. INTERCELLULAR JUNCTIONS • Neighboring cells within a multicellular organism often adhere, interact, and communicate through intracellular junctions • Tight junctions • Desmosomes • Gap junctions

  6. INTERCELLULAR JUNCTIONS

  7. TISSUE TYPES Four major tissue types • Epithelial tissue • Connective tissue • Muscle tissue • Nervous tissue

  8. EPITHELIAL TISSUE • Sheets of cells covering body surfaces or lining body cavities • Form boundaries between different environments • e.g., Epidermis of skin separates inside and outside of body • e.g., Epithelium lining urinary bladder separates underlying cells from urine

  9. EPITHELIAL TISSUE • Many diverse functions • Protection • Absorption • Filtration • Excretion • Secretion • Sensory reception

  10. CLASSIFICATION OF EPITHELIA Cell layers • Simple epithelia • Single cell layer • Facilitates absorption and filtration • Stratified epithelia • Two or more cell layers • Common in high-abrasion areas • e.g., Skin surface, mouth

  11. GLANDULAR EPITHELIA • A gland consists of one or more cells that produce and secrete a product (secretion) • Secretion: verb and noun • Endocrine vs. exocrine • Unicellular vs. multicellular

  12. ENDOCRINE GLANDS • “Ductless glands” • (Ducts are eventually lost) • Produce hormones • Secreted directly into extracellular space via exocytosis • Many (but not all) are epithelial derivatives • More information in their own chapter

  13. EXOCRINE GLANDS • More numerous than endocrine glands • Secrete into body cavities or onto body surfaces • (i.e., Not into extracellular space) • Unicellular glands via exocytosis • Multicellular glands via ducts • Diverse • e.g., Mucous, sweat, oil, and salivary glands, etc.

  14. EXOCRINE GLANDS Multicellular Glands: Structural Classification • Simple • Compound • Tubular • Alveolar (acinar) • Tubuloalveolar

  15. CONNECTIVE TISSUE • Found everywhere in the body • Most widely distributed primary tissue • Four main classes • Connective tissue proper • Cartilage • Bone tissue • Blood

  16. CONNECTIVE TISSUE • Major functions • Binding and support • Protection • Insulation • Transportation • Which of these functions are accomplished by bone and cartilage? Fat? Blood?

  17. CONNECTIVE TISSUE Common Characteristics • Common origin • All connective tissues arise from mesenchyme (an embryonic tissue) • Degrees of vascularity • Avascular • poorly vascular • highly vascular • Extracellular matrix • Largely composed of non-living extracellular matrix

  18. CONNECTIVE TISSUE • Three main structural elements • Ground substance • Fibers • Cells • Ground substance + fibers = matrix

  19. TYPES OF CONNECTIVE TISSUE Connective Tissue Proper • Two subclasses • Loose connective tissue • Areolar • Adipose • Reticular • Dense connective tissue • Dense regular • Dense irregular • Elastic

  20. TYPES OF CONNECTIVE TISSUE Cartilage • Three varieties • Hyaline cartilage • Elastic cartilage • Fibrocartilage

  21. TYPES OF CONNECTIVE TISSUE Bone (Osseous Tissue) • Matrix similar to cartilage • More abundant collagen fibers • Inorganic calcium salts • Rocklike hardness • Ability to support & protect

  22. TYPES OF CONNECTIVE TISSUE Bone (Osseous Tissue) • Osteoblasts produce organic portion of matrix • Bone salts then deposited on & between fibers • Osteoblasts  osteocytes • Osteocytes reside in lacunae within the matrix • Vascular

  23. TYPES OF CONNECTIVE TISSUE Blood • Very atypical connective tissue • Does NOT connect things • Provides NO mechanical support • Why is it considered connective tissue? • Derived from mesenchyme

  24. TYPES OF CONNECTIVE TISSUE Blood • Various types of cells • Blood plasma is fluid matrix • Plasma proteins are “fibers” • Various functions • Transportation • Protection

  25. MEMBRANES • Continuous multiple sheets comprised of • Epithelium • Underlying layer of connective tissue • Three types of covering and lining membranes • Cutaneous • Mucous • Serous These membranes are multicellular structures, and are quite different from the plasma membrane of a cell

  26. CUTANEOUS MEMBRANES • a.k.a., “Skin” • Organ system • Consists of • Keratinized stratified squamous epithelium • “Epidermis” • Thick layer of dense irregular connective tissue • “Dermis” • Dry membrane

  27. MUCOUS MEMBRANES • a.k.a., “Mucosae” • Line body cavities open to exterior • e.g., digestive, respiratory, & urogenital tracts • “Wet” membranes • Bathed in secretions or urine • Often adapted for absorption and secretion • Many secrete mucus • Not all (urinary)

  28. SEROUS MEMBRANES • a.k.a., “Serosae” • Moist membranes found in closed ventral body cavities • Consist of • Simple squamous epithelium (mesothelium) • Thin layer of loose connective (areolar) tissue • Name based on location • Pleura of lungs • Pericardium of heart • Peritoneum of abdominopelvic cavity

  29. SEROUS MEMBRANES • Produce serous fluid • Blood filtrate + hyaluronic acid secreted by mesothelium • Lubricates facing surfaces of parietal and visceral layers

  30. NERVOUS TISSUE • Main component of the nervous system • Brain, spinal cord, and nerves • Regulates and controls body functions • Two main cell types • Neurons • Generate and conduct nerve impulses • Supporting cells • Non-conducting cells that support, insulate, and protect neurons

  31. MUSCLE TISSUE • Highly cellular • Well vascularized • Responsible for most types of body movement • Possess myofilaments • Actin and myosin • Three types • Skeletal muscle • Cardiac muscle • Smooth muscle

  32. SKELETAL MUSCLE • Skeletal muscle cells • a.k.a., “Muscle fibers” • Long, cylindrical cells • Multinucleate • Striated • Voluntary

  33. SKELETAL MUSCLE • Forms organs called skeletal muscles • Packaged by sheets of connective tissue • Attached to bones of skeleton • Contract to pull on bones or skin • Movement results

  34. CARDIAC MUSCLE • Found only in the wall of the heart • Contractions propel blood through blood vessels • Cardiac muscle cells • “Myocytes” • Striated • Uninucleate • Branching • Involuntary

  35. SMOOTH MUSCLE • Found mainly in walls of hollow organs • e.g., Intestines, esophagus, blood vessels, etc. • Contractions squeeze substances through these organs • No visible striations • Smooth muscle cells • Spindle shaped • Uninucleate • Involuntary

  36. BODY DEFENSES • Mechanical barriers are the body’s first line of defense against injury and infection • Skin and mucous membranes • Respiratory cilia • Acids secreted into stomach and from skin • Tissue injury breaches this first line of defense • Stimulates inflammatory and immune responses • Second and third lines of defense, respectively • Tissue is ultimately repaired

  37. TISSUE REPAIR • Injured cells release growth factors • Stimulate cells to divide and migrate • Two major tissue repair means: • Regeneration • Replacement of destroyed tissue with same type of tissue • Fibrosis • Replacement with fibrous connective tissue (scar tissue) • Type of repair dependent upon • Type of tissue damaged • Severity of injury

  38. TISSUE REPAIR Inflammation • Injured cells, macrophages, and mast cells release inflammatory chemicals • Dilation and increased permeability of capillaries • Plasma and leukocytes enter injured area • Plasma proteins form clot • Halts blood loss • Isolates injured area • Prevents spread of microbes • Forms scab

  39. TISSUE REPAIR Organization • Blood clot replaced by granulation tissue • Capillaries • Proliferating fibroblasts • Produce growth factors, collagen fibers • Pull margins of wound together • Macrophages • Digest clot • Granulation tissue ultimately becomes scar tissue

  40. TISSUE REPAIR Permanent Repair • Surface epithelium begins to regenerate • Grows under scab • Scab ultimately detaches • Epithelium fully regenerated • Fibrous material beneath epithelium matures and contracts • Scar tissue beneath epithelium • Scar may be visible or not

  41. TISSUE REPAIR • The regenerative capacity of different tissues varies widely • Some tissues regenerate extremely well • e.g., Epithelial, bone, areolar connective tissue, blood-forming tissue • Some tissues have a moderate regenerative capacity • e.g., Smooth muscle, dense regular connective tissue • Some tissues have a weak regenerative capacity • e.g., Skeletal muscle, cartilage • Some tissues have a virtually no functional regenerative capacity • e.g., Cardiac muscle, nervous tissue

  42. TISSUE REPAIR • In non-regenerative tissue and severe wounds, damaged tissue is replaced by fibrosis • Resulting scar tissue is strong, but lacks flexibility, elasticity, and function of normal tissue

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