Tissue and Skin

1. Tissue and Skin

2. Tissues • Tissues are layers or groups of similar cells with a common function • 4 types of tissues include: • Epithelial • Connective • Muscle • Nervous

3. Epithelial Tissue • Epithelial tissue covers all free body surfaces, forms the inner lining of body cavities, lines hollow organs, and is the major tissue of glands. • A basement membrane anchors epithelium to connective tissue. Epithelial tissue lacks blood vessels, has cells that are tightly packed, and is continuously replaced. • It functions in protection, secretion, absorption, and excretion.

4. Epithelial Tissue Apical Surface Basal Surface Basement membrane Lower surface of epithelium Structureless material secreted by the cells. • A free surface or edge exposed to the body’s exterior or to the cavity/lumen of an internal organ.

5. Types of Epithelial Tissue Simple • Squamous • Cuboidal • Columnar • Pseudostratified Stratified • Squamous • Cuboidal • Columnar • Transitional

6. Simple Squamous Epithelial • This tissue consists of a single layer of thin, flattened cells through which substances pass easily. • It functions in the exchange of gases in the lungs and lines blood vessels, lymph vessels, and membranes within the thorax and abdomen.

7. Simple Cuboidal Epithelium • This tissue consists of a single layer of cube shaped cells. • It carries on secretion and absorption in the kidneys and various glands.

8. Simple Columnar Epithelium • This tissue is composed of elongated cells whose nuclei are near the basement membrane. • It lines the uterus and digestive tract, where it functions in protection, secretion and absorption.

9. Pseudostratified Columnar • This tissue appears stratified because the nuclei are at two or more levels. • Its cells may have cilia that move mucus over the surface of the tissue. • It lines tubes if the respiratory system.

10. Stratified Squamous Epithelium • This tissue is composed of many layers of cells; the top layers are flattened. • It protects underlying cells from harmful environmental effects. • It covers the skin and lines the oral cavity, esophagus, vagina and anal canal.

11. Stratified Cuboidal Epithelium • This tissue is composed of two or three layers of cube-shaped cells. • It lines the larger ducts of the sweat gland, salivary glands and pancreas. • It functions in protection.

12. Stratified Columnar Epithelium • The top layer of cells in this tissue contains elongated columns. Cube-shaped cells make up the bottom layers. • It is in part of the male urethra and parts of the pharynx • Functions in protection and secretion.

13. Transitional Epithelium • Specialized to become distended. • It is in the walls of organs of the urinary tract. • It helps prevent the contents of the urinary passageways from diffusing out.

14. Connective Tissue • Connects, supports, protects, fills spaces, stores fat, produces blood cells, protects against infections, and helps repair damage tissues • Most are well vascularized except tendons, ligaments and cartilage • Fibers—made by CT cells and secreted • Collagen fibers (white) • Elastic fibers (yellow) • Reticular fibers (fine collagen)

15. Types of Connective tissue • From most rigid to softest: • Bone • Cartilage • Dense connective tissue • Loose connective tissue • Blood

16. Major Cell types • Fibroblasts produce collagenous and elastic fibers • Macrophages are phagocytes • Mass cells release heparin and histamine and usually are near blood vessels

17. Bone • The extracellular matrix of bone contains mineral salts and collagen • Its cells usually form concentric circles around osteonic canals • Active tissue that heals rapidly • Osseus tissue • Most rigid connective tissue, with deposits of mineral salts and collagen within the matrix. • Bone cells, called osteocytes, lie within lacunae and are arranged in concentric circles • Good blood supply, enabling rapid recovery after an injury. • Rocklike hardness allows protection and support of other body organs

18. Cartilage • Provides a supportive framework for various structures. • Cartilage cells (chondrocytes) lie within lacunae in the gel-like fluid matrix.

19. Types of Cartilage • Hyaline cartilage is white with abundant fine collagen fibers, is found at the ends of bones, and supports respiratory passages. • Elastic cartilage, with elastic fibers, provides a framework for the external ears and parts of the larynx. • Fibrocartilage is a tough tissue that provides a shock-absorbing function in intervertebral disks and in the knees and pelvic girdle.

20. Dense Connective Tissue • This tissue consists of densely packed collagenous fibers and is very strong but lacks a good blood supply. • Fibroblasts—cells that make fibers • It is found as part of tendons and ligaments.

21. Loose Connective Tissue • This type of tissue forms delicate, thin membranes throughout the body that bind body parts together. • Fibroblasts are separated by a gel-like ground substance that contains collagenous and elastic fibers. • It binds the skin to underlying organs and fills spaces within muscle.

22. Areolar Tissue • Most widely distributed connective tissue in the body • Cusions and protects body organs it wraps • “Glue” that holds internal organs together

23. Adipose Tissue • Fat storing connective tissue • Found beneath the skin (insulates the body), around joints, padding the kidneys and other internal organs, and in certain abdominal membranes.

24. Reticular Connective Tissue • Network of interwoven reticular fibers associated with reticular cells • Internal supporting framework

25. Blood • Blood is composed of cells (red and white) suspended in a fluid matrix (plasma). • It is formed in the blood-forming tissues inside red bone marrow and functions to transport substances throughout the body.

26. The Integumentary System • The skin and its accessory structures make up the integumentary system. • Five major functions • Serving as a barrier against infection and disease • Helping to regulate body temperature • Removing waste products from the body • Providing protection against Ultraviolet radiation from the sun • Producing vitamin D

27. Layers of Skin • Epidermis • Dermis • Subcutaneous layer • beneath dermis • not part of skin

28. Subcutaneous Layer • Hypodermis • Loose Connective Tissue • Adipose Tissue • Major Blood Vessels

29. Epidermis • Layer of stratified squamos epithelium that lacks blood vessels • Thickest on Palms • Keratonized • Outermost Layer • Its layers are made of Mostly DEAD CELLS. • Most of the cells of the epidermis undergo rapid cell division (MITOSIS). • As new cells are produced, they push older cells to the surface of the skin.  The older cells become flattened, lose their cellular contents and begin  making KERATIN.

30. Dermis • Composed of irregular dense connective tissue that binds the epidermis to underlying layer • Contains blood vessels • Nerve tissue is scattered through the dermis