Tissues – Cells Working Together

1. Tissues – Cells Working Together Dr. Anderson GCIT

2. Tissues • Collections of similar cells that work together in an organ to perform a very specific function in that organ for the organism • Four basic tissue types • Epithelial • Connective • Movement • Control

3. Epithelial Tissue • Sheets of cells that cover the body or line body cavities • Covering – lining epithelium • Skin • Lines open cavities of digestive, respiratory, cardiovascular and reproductive systems • Glandular epithelium • Makes up the various glands (secretory organs) of the body

4. Functions of Epithelia • Protection • Protects stomach from digesting itself by secreting buffering compounds • Absorption • Cells can take in substances via endocytosis/diffusion/active transport • Filtration • Certain substances are preferentially removed/added to blood • Excretion • Wastes exit via exocytosis, diffusion • Secretion • Cells products (proteins) are exported via exocytosis, diffusion • Sensory Perception • Cells on the surface contain nerve endings that respond to stimulus (heat, pain, pressure, etc.)

5. Characteristics of Epithelia • Polarity • All epithelial cells have two distinct “ends” • Apical Surface – free surface exposed to exterior or lumen of a body cavity • Basal Surface – bordered by the basal lamina, anon-cellular adhesive sheet to which epithelial cells are attached that acts as a filter between the epithelia and underlying connective tissue

6. Polarity of Epithelial Cells Apical surface Basal surface Basal lamina

7. Epithelial Connections • Tight Junctions • Prevent the movement of materials between cells • Desmosomes • Provide support and tensile strength to tissues

8. Epithelial Support • All epithelial cells are supported by a thin layer of connective tissue called the reticular lamina (just deep to the basal lamina) • The basal lamina and the reticular lamina form the basement membrane

9. Communication and Transport • Epithelial cells are innervated (nerves penetrate into the tissue) • However, epithelial cells are NOT perfused directly with blood vessels • Materials must be transported to and from blood in vessels lying under the basement membrane

10. Epithelial Cell Arrangement

11. Epithelial Regeneration • Cells are frequently lost due to abrasion, wounds, etc. • Epithelial cells have the capacity to regenerate the lost tissue via mitosis • How is this adaptive to the organism?

12. Classification of Epithelia • Morphology • Squamous • Cuboidal • Columnar • Arrangement • Simple • Stratified

13. Epithelial Morphology • Squamous – flat, much shorter than wide • Cuboidal – height and width are equidistant • Columnar – Height much greater than width

14. Simple Epithelium

15. Stratified Epithelium • Contain two or more cell layers • Major role: Protection • E.G - skin

16. Glandular Epithelia • Tissues that secrete substances (usually proteins) made by the cells in the tissue • Endocrine glands – no ducts • Produce hormones, proteins, steroids, etc. • Exocrine Glands – secrete onto body surfaces or into cavities • Mucus, sweat, oil, pancreas, salivary,

17. Endocrine Glands

18. Exocrine Glands • Unicellular – mucus glands and goblet cells • Multicellular - 3 parts • Duct - for export • Secretory unit – makes product to be secreted • Fibrous capsule – connective tissue, blood vessels and nerves; may divide the gland into lobes

19. Mode of Secretion • Cells metabolize the chemical to be released • Cells release this chemical into the duct via exocytosis (or cell lysis)

20. Tubular – if secretory cells are present in the duct Alveolar – if secretory cells are in the pocket of tissue

21. Connective Tissue • Function • Binding and support (Bone, cartilage, fascia) • Protection – Osteocytes (Bone) • Insulation – Adipose Tissue (fat) • Transportation ( Blood)

22. Common Characteristics • Common embryologic origin (mesenchyme) • Degrees of vascularity • Consists of living cells and an extracellular matrix • Non-living cell-derived substances • Made of ground substance and fibers

23. Ground Substance • Made of interstitial fluid, cell adhesion proteins, proteoglycans • Can range from very little to great viscosity • Serves to control diffusion rates into and out of adjoining cells (between blood vessels and epithelium)

24. Fibers • Collagen – provide tensile strength • Elastic Fibers - (elastin) can stretch, allowing flexibility • Reticular Fibers – collagen-based fibers that support small blood vessels and organs

25. Cells • Relative to what organ is being examined, each has a different job • Osteocytes • Chondrocyte • Hemocyte

26. Types of Connective Tissue • Loose Connective Tissue • Areolar • Adipose • Dense Connective Tissue • Regular • Irregular • Elastic

27. Areolar Connective Tissue • Very loosely arranged fibers in matrix • Provides a reservoir for water and salts for surrounding tissues • Very viscous • Damage to this area or nearby tissues results in water retention – an edema

28. Adipose Connective Tissue • Fat tissue – composed of adipocytes • Almost the entire volume of the cell is taken up by stored lipids • Stores energy, but subcutaneous fat (under the skin) acts as a • Shock absorber • Insulator

29. Dense Regular Connective Tissue • Contains closely packed collagen fibers that run parallel to the direction of pull providing great tensile strength • Fibroblasts are interspersed within this tissue to make new collagen fibers • Found in: • Tendons – connect muscle to bone • Aponeuroses – connect muscles to muscles • Fascia – covering that surrounds individual muscles

30. Dense Irregular Connective Tissue • Also contains bundles of collagen fibers, but are arranged irregularly • Forms fibrous coverings (capsules) that surround some organs and joints, e.g. kidneys, bones, cartilage, etc.

31. Combines flexibility and strength for support and shock absorption • Not vascular and not innervated • Hyline cartilage • Elastic Cartilage • Fibrous Cartilage Cartilage

32. Hyaline Cartilage • Hyaline (glassy) cartilage • Provides firm support to the ends of long bones (cushioning) • Connects bones and provides structure • Bridge of nose • Connects ribs to sternum • Predecessor to bone in human embryos

33. Elastic Cartilage • More flexible and less rigid than hyaline cartilage • Examples • Ear • Epiglottis

34. Fibrocartilage • Able to resist heavy compressive forces in areas of the body under the most strain • Cartilage between the femur and tibia/fibula in the knee • Intervertebral discs

35. Bone • Primarily provides support to the body, but also houses tissues that produce fat and blood cells (marrow) • Bone is well supplied by blood vessels (bones are living tissue) • Great diversity of shapes and functions

36. Blood • Blood cells (WBC, RBC, platelets) surrounded by a liquid matrix (plasma) • Transports materials to all of the cells in the body • O2, CO2, food, wastes, hormones, etc. • Provides the second line of defense against pathogens

37. Nervous Tissue • Comprises the brain, spinal cord, and peripheral nerves • Major cell type • Neurons – respond to stimuli and transmit impulses

38. Muscle Tissue • Responsible for most types of movement • Internal movement as well as external • Three types • Skeletal – under voluntary control, moves skeleton • Smooth – under involuntary control, moves substances into, out of, or through the body • Cardiac – heart muscle, under involuntary control (largely)