Body Tissues

Body Tissues

1. EPITHELIUM TISSUE

   • . A lining, covering and glandular tissue of the body . Covers all free body surfaces and contains versatile cells ( allow substances to pass through ) > One covers outer layer of skin > Others line cavities inside body . Functions> Skin & respiratory epithelium - protection> Small intestine epithelium - absorption> Kidney epithelium - filtration> Salivary epithelium - secretion
   • SIMPLE EPITHELIUM
     • Simple squamous
       • . Single layer of flattened cells . Nucleus located at the top . Lines the glomerulus . Usually forms membrane to line body cavities, lungs and capillaries > Serous membrane - a slick membrane that line the ventral body cavity and cover the cavities in that cavity.
     • Simple cuboidal
       • . Single layer of cube-like cells lying on the basement membrane  . Nucleus located at the middle . Common in glands and their ducts . Covers the ovaries . Forms walls of kidney tubules 
     • Simple columnar
       • . Single layer of tall cells . Nucleus located at the bottom . Include goblet cells, which produce mucus . Lines digestive tract and gall bladder
     • Pseudostratified
       • . Single layer . Some cells are shorter than others, causing nuclei to appear at different heights above the basement membrane therefore, giving the pseudo (fake) impression that it is a doubled-layer cell. . Cilitated in the respiratory tract ( known as : pseudostratified cilitated columnar epithelium ) . Function in absorption/secretion
   • STRATIFIED EPITHELIUM
     • Stratified squamous
       • . Most common in the body . Double layer with cells flattened at the free edge . Protective covering for friction . Located at mouth and skin, areas where friction is common
     • Transitional epithelium
       • . Shape of cells is flexible ( depends upon the amount of stretching ) . Lines organs of the urinary system ONLY. . When organs are not stretched, membrane may appear many-layered ; superficial cells rounded and dome-like.. Surface cells flattened and become squamous like when organs disten with urine.. The ability of transitional cells to slide past one another & change shape allow uterus to stretch and distend to allow more urine to be stored.

2. CONNECTIVE TISSUE

   • . Connect body parts  . Found everywhere in the body . Functions > Binds body tissue together > Supports the body > Provides protection . Extracellular matrix > non-living material that surrounds living cells > Forms a packaging tissue around organs to bear weight, protect and support the organs
   • Bone
     • . Known as Osseous tissue . Composed of  > bone cells in lacunae (cavities - filled with osteocytes) > hard matrix of calcium salts > large no. of collagen fibers . Used to protect and support the body
   • Cartilage
     • Hyaline Cartilage
       • . Consists of lacunae . Composed of > Abundant collagen fibers > Rubbery matrix . Fetal skeleton (skeleton of a fetus) = hyaline cartilage - later replaced by bones close to birth . Only epiphyseal/growth plates in long bones are not replaced which facilitates growth during youth.
     • Fibrocartilage
       • . Highly compressible . Forms the cushion-like disks between vertebrae of spinal column.
     • Elastic Cartilage
       • . Found in structures with elasticity
   • Dense Connective Tissue
     • . Main matrix element is collagen fibers . Cells are fibroblasts > Tendon - attach muscle to bone > Ligaments - attach bone to bone
   • Loose Connective Tissue
     • . Matrix is a tissue in which fat globules predominate . Many cells contain large lipid deposits . Functions > Insulates the body > Protects some organs > Serves as a site of fuel storage ( Adipose Tissue )
   • Reticular Connective Tissue
     • . Limited to certain sites . Forms the stroma (literally bed/matress)/ internal framework which supports many free blood cells (lymphocytes) in lymphoid organs
   • Vascular Tissue
     • . Blood > consists of blood surrounded by non-living, fluid matrix, blood plasma, therefore, it is a connective tissue.

3. MUSCLE TISSUE

   • Skeletal Muscle
     • . Cells can be controlled voluntarily . Cells are attach to connective tissue . Cells are striated . Cells have more than 1 nucleus (multi-nucleate cells)
   • Cardiac Muscle
     • . Found only in the heart . Involuntary muscle - pump blood . Cells attached to other cardiac muscle cells at intercalated disks (jaggered) . Cells are striated . One nucleus per cell. 
   • Smooth Muscle
     • . Involuntary muscle . Attached to other smooth muscle cells . Surrounds hollow organs . No visible striations . One nucleus per cell

4. Nervous Tissue

   • . Neurons and nerve support cells . Function > Send impulses(irritability, conductivity) to other areas of the body

5. Tissue repair

   • Regeneration
     • . Replacement of destroyed tissue (subjected to wear and tear) by the same kind of cells TISSUE REGENERATION . Tissue that regenerate easily - epithelium tissue, fibrous connective tissue and bone . Tissue that regenerate poorly - skeletal muscle . Tissue that are replaced by largely scar tissue - cardiac muscle, nervous tissue within the brain and spinal cord
   • Fibrosis
     • . Repair by dense fibrous connective tissue (scar tissue) . Determination of method > type of tissue damaged > severity of the injury