Human Tissues

Human Tissues

1. Definition of Tissues

   • groups of cells that have a similar structure and act together to perform a specific function

2. Epithelial

   • line body cavities and cover internal and external body surfaces
   • Types
     • Covering and Lining
       • classified through arrangement
         • Cell Layers
           • Simple = 1 single layer
           • Stratified = multiple layers
           • Pseudostratisfied = appears to have more than 1 layer, only has 1
         • Cell Shape
           • Squamous
             • thin/flat
             • allow for rapid passages of substances
             • Simple Squamous
             • Stratified Squamous
             • Simple Squamous
               • located in air sacs of lungs, lines heart, blood vessels, and lymphatic vessels
               • function is diffusion, filtration, secretion
             • Stratified Squamous
               • lines esophagus, mouth, and vagina
               • function is protection against abrasion (makes skin)
           • Cuboidal
             • cubes or hexagons
             • function in secretion or absorption
             • Simple Cuboidal
             • Stratified Cuboidal
             • Simple Cuboidal
               • located in kidney tubules and lines ducts of glands
               • function is secretion and absorption
             • Stratified Cuboidal
               • function is protection
               • located in sweat glands, salivary glands, mammary glands
           • Columnar
             • taller than they are wide
             • contain cilia or microvilli
             • Simple Columnar
             • Stratified Columnar
             • Simple Columnar
               • function is absorption and secretion of mucus and enzymes
               • located in bronchi of lungs, uterine tubes, uterus (with cilia) or digestive tract, bladder (without)
             • Stratified Columnar
               • located in male urethra and ducts of some glands
               • function is secretion and protection
             • Pseudostratified Columnar
               • lines trachea and upper respiratory tract
               • secretes mucus and ciliated moves mucus
           • Transitional
             • change shape from flat to cuboids
             • allows urinary organs to expand and stretch
             • lines the urinary bladder, ureters and urethra, and in the ducts of the prostrate gland
     • Glandular
       • function: secretion
       • endocrine glands secrete hormones into the bloodstream
       • deep to covering and lining epithelium
       • gland: 1+ highly specialized cells that secrete
       • exocrine glands secrete products through ducts and empty at covering and lining epithelium
   • avascular - no blood cells
   • have a nerve supply
   • high capacity for cell division
   • cells have:
     • apical surface (exposed to body
     • lateral surface (side)
     • basal surface (attached to basement membrane)
       • *thin, extracellular structure between epithelium and deeper connective tissue
   • little extracellular matrix between closely packed cells

3. Nervous

   • function is to conduct nerve impulses
   • groups of organized cells in the nervous system
   • types of cells
     • Neurons
       • convert stimuli into nerve impulses and conduct them
     • Neuroglia
       • do not generate nerve impulses, but serve supportive functions

4. Connective

   • Types
     • Dense
       • Regular
         • located in tendons and ligaments
         • attaches muscles to bones or to muscles
       • Irregular
         • located in dermis of skin
         • provides structural strength
       • Elastic
         • located in several organs, including the largest arteries in the body
         • provides elasticity and extensibility to the dermis and assists in recovery from deformation
     • Loose
       • Areolar
         • surrounds blood vessels, nerve bundles, muscles, and organs.; fills the spaces between organs and connects skin to underlying muscle
         • wraps and cushions organs
       • Adipose
         • provides reserve fuel
         • under skin, around internal organs, between muscles, within bone marrow, and in breast tissue
       • Reticular
         • located in lymphoid organs, the kidney, spleen, lymph nodes, and bone marrow
         • forms the stroma and provides structural support
     • Bone
       • function in support, movement, protection, production of blood cells, storage of ions, and endocrine regulation
     • Blood
       • contained within blood vessels
       • transport respiratory gases, nutrients, wastes, and more substances
     • Cartilage
       • Hyaline
         • forms most of the embryonic skeleton; ends of bones in free-moving joints as articular cartilage, at the ends of the ribs, and in the nose, larynx, trachea, and bronchi
         • supports and reinforces; flexibility
       • Fibrocartilage
         • located in intervertebral discs and at the insertions of ligaments and tendons
         • tensile strength with the ability to absorb compressive shock
       • Elastic
         • located in skin, lungs, arteries, veins, elastic cartilage, fetal tissue, and other structures
         • maintains the shape of a structure while allowing great flexibility, provides elasticity and extensibility to the dermis and assists in recovery from deformation

5. Muscular

   • Skeletal Muscle
     • Pulls on bones allowing body movements
     • voluntary and striated
   • Cardiac Muscle
     • pumps blood through blood vessels
     • forms wall of heart
     • involuntary and striated
   • Smooth Muscle
     • found in walls of hollow organs such as stomach and bladder
     • function in maintaining and controlling the blood pressure and flow of oxygen throughout the body and more
     • involuntary

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