Tissues

1. Tissues Chapter 4

2. Tissue - groups of cells with similar structure and function. Four principle human tissue types: epithelium (covering) connective (support) muscle (movement) nervous (control) Histology: study of tissues

3. A fertilized egg called a zygote will rapidly divide into a blastocyst. By week 3: three layered embryo (gastrulation) - ectoderm: “outer skin”, epidermis and nervous system - mesoderm: skeletal, muscular and circulatory systems - endoderm: “inner skin” linings of the digestive and respiratory tracts

5. Epithelial: sheet of cells that covers body surfaces and lines inside of body cavities. Glandular epithelium: glands Functions: - protection - absorption - filtration - excretion - secretion - sensory reception - gas exchange

6. Characteristics of epithelial tissue: - Cellularity: composed of closely packed cells - Specialized contacts: tight junctions and desmosomes bind these closely packed cells - Polarity: apical surface: - free surface exposed basal surface: - lower surface attachment - Basement membrane: basal lamina (filtering) + reticular lamina (collagen protein fibers). Together they help resist tearing and stretching of epithelium

7. Avascularity: epithelial tissue does not have a blood supply. • Regeneration: replace lost tissue via cell division

8. Epithelium classification: All epithelial tissue has two names: 1st: number of cell layers 2nd: shape of cells Number of cell layers: Simple: single layer (absorption and filtration) Stratified: multiple layers (protection) Pseudostratified: artificial/false layers Shape of cells: Squamous: flat and scale like Cuboidal: cube shaped Columnar: column shaped Transitional: varies

10. 1) Simple Squamous Epithelium: a.       Description:  single layer of flattened cells with a disc-shaped central nuclei and sparse cytoplasm. b.      Function:  allows passage of materials by diffusion and filtration in sites where protection is not important. Also secretes lubricant. c.       Locations:  Kidney glomeruli, air sacs of lungs, capillaries, linings of heart and lymphatic system.

12. 2) Simple cuboidal epithelium a.       Description:  single layer of cube-like cells with large spherical centrally located nuclei. b.      Function:  secretion and absorption c.       Locations:  Kidney tubules, ducts and secretory portions of glands, ovary surface

14. 3)    Simple columnar epithelium a.       Description:  single layer of tall cells with round to oval nuclei; some cells bear cilia; may contain goblet cells that produce mucus. b.      Function: absorption; secretion of mucus and enzymes; cilia propel substances. c.       Location:  non-ciliated type lines digestive tract, gallbladder, and ducts from glands; ciliated type lines small bronchi, uterine tubes, and uterus.

16. 4)    Pseudostratified columnar epithelium a.       Description: single layer of cells of differing heights so that nuclei are a differing levels; may contain goblet cells and bear cilia. All cells contact the basement membrane but not the free surface (only the tallest cells). Nuclei are at different levels giving the false appearance b.      Function:  secretion, propulsion by ciliary action. c.       Location:  non-ciliated type lines male reproductive ducts; ciliated type lines much of respiratory tract.

18. 5)   Stratified squamous epithelium a.       Description: thick layers of flattened cells; often keratinized layer and a mitotic layer. b.      Function:  protects underlying tissues in areas subject to abrasion c.       Location:  non-keratinized type lines the mouth and vagina; keratinized type forms the epidermis of skin.

20. 6)   Transitional epithelium a.       Description:  resembles both stratified squamous and stratified cuboidal.  Basal cells are cuboidal or columnar; surface cells are dome shaped. b.      Function:  stretches readily and permits distension. c.       Location:  Lines uterus, bladder, and urethra

22. 7)     Glandular epithelium a.       Endocrine glands: “ductless” glands that produce hormones. b.      Exocrine glands: glands possessing ducts                                                                                      Merocrine: secrete products by exocytosis. pancreas and sweat glands                                                                                      Holocrine: accumulate products until the cell ruptures. Sebaceous “oil” glands

23. Connective tissue: most abundant tissue in human body. - binding and support (ligaments) - protection (bone) - insulation (adipose) - transportation (blood) - absorb shock - immunity Ground substance: unstructured material that fills the space between cells and contains the fibers.

24. Classification of connective tissues I- Embryonic connective tissue - mesenchyme (all connective tissue derived) - mucous connective tissue (Wharton’s jelly found in fetus) II- Mature connective tissue A. Loose connective tissue - areolar tissue - adipose tissue - reticular connective tissue

25. B. Dense connective tissue - dense regular connective tissue - dense irregular connective tissue - elastic connective tissue C. Cartilage - hyaline cartilage - fibrocartilage - elastic cartilage D. Bone (osseous) tissue E. Blood (vascular) tissue

27. Blast cells are active cells that secrete both fibers and ground substance (matrix). Cyte cells are mature cells that maintain (repair or regenerate) matrix. Examples of connective tissue cell types are as follows: Connective tissue proper - fibroblasts/fibrocytes Cartilage - chondroblast/chondrocyte Blood - hemocytoblast/hemocyte - Hematopoietic stem cells: blood producing cells Bone - osteoblast/osteocyte

28. Loose connective tissue- loosely woven fibers Areolar: Most widely distributed connective tissue in the body - binds body parts - wraps around small blood vessels and nerves. - binds skin to underlying structures - composed mainly of fibroblasts - forms lamina propria in mucous membranes

31. Adipose: primarily made of adipocytes. - storage of triglycerides - nucleus is pushed to the side - insulator - reduces heat loss through skin. - energy reserve - subcutaneous, around kidneys, omentum (over intestines), behind eyeball (orbital fat)

33. Omentum

34. Reticular: composed of reticular fibers - forms stroma (internal framework) in organs; mainly lymphoid - spleen - lymph nodes - bone marrow - supports white blood cells - binds smooth muscle cells together.

36. Dense regular connective tissue - fibrous connective tissue - bundles of collagen fibers with fibroblasts strongest and most abundant. - high tensile strength fibrous protein - collagen molecules are secreted in the extracellular spaces and fibers are spontaneously formed; called white fibers

37. - tendons: muscle to bone - aponeuroses : sheet like tendons (muscles to other muscle/bones) - ligaments : bone to bone. Contain more elastin fibers so they have a better ability to stretch.

38. Tendon

40. Dense irregular connective tissue: contains collagen fibers that have an irregular pattern. - seen in sheets - tensions are exerted in various directions - dermis of skin - periosteum of bone - heart valves

42. Cartilage: ability to endure great stress. - contains dense network of collagen and elastic fibers embedded in chondroitin sulfate. - chondrocytes are located in spaces called lacunae. - has no blood supply - no nerves

43. Hyaline cartilage: called gristle. Most abundant type of cartilage - located: ends of long bones (articular cartilage) - nose - trachea - bronchi - ends of ribs - flexibility - movement of joints - support

45. Fibrocartilage: chondrocytes scattered among collagen. - pubic symphysis - intervertebral discs - menisci of the knee. - support and fusion - absorb compressive shock

48. Elastic cartilage: Similar to hyaline cartilage, more elastic fibers present (stretching) - pinna of ear - epiglottis - vocal cords - walls of artery

50. Bone (osseous) tissue: Support, protection, storage, blood forming tissues. - calcified matrix with many collagen fibers - lie in “little lakes” called lacunae. - blood cell formation (hematopoiesis) - well vascularized - mature cells called osteocytes