Unit 7.5

• Types of Tissues


  • Epithelial
  • Connective
  • Muscular
  • Nervous
• Epithelial Tissue


  • Forms a continuous layer over body surfaces
  • Lines body cavities
  • Forms glands
  • Epithelial cells may be connected by tight junctions, adhesion junctions, or gap junctions
  • Functions include protection, secretion, absorption, excretion, filtration

  
• Types of Epithelial Tissue


  • Simple
  • Stratified
  • Glandular

  
• Simple Epithelium


  • A single layer of cells, all touching basement membrane
• Types of Simple Epithelium


  • Squamous (flattened cells)
  • Cuboidal (cube-shaped cells)
  • Columnar (cells resembling columns)
• Glandular Epithelium


  • Secretes a product
  • Can be a single epithelial cell or contain many cells
  • Exocrine glands secrete products into ducts or cavities
  • Endocrine glands secrete products directly into the bloodstream
• Stratified Epithelium


  • Layers of cells, only bottom layer touching basement membrane

  
• Types of Connective Tissue


  • Fibrous
  • Supportive
  • Fluid

  
• Fibrous Connective Tissue


  • Consists of fibroblast cells and a matrix containing collagen and elastic fibers
  • Loose fibrous connective tissue allows organs to expand
  • Adipose tissue stores energy and provides insulation and padding
  • Dense fibrous connective tissue is strong (tendons, ligaments)

  
• Supportive Connective Tissue


  • Cartilage - classified by type of collagen and elastic fibers, cells lie in small chambers (lacuna) in the matrix
  • Bone - matrix is inorganic salts deposited around protein fibers, bone cells located in lacunae arranged in concentric circles within osteons around central canals

  
• Fluid Connective Tissue


  • Blood - cells embedded in a liquid matrix (plasma), transports nutrients, oxygen, and removes wastes
  • Lymph - fluid connective tissue located in lymphatic vessels

  
• Muscular Tissue


  • Contractile cells containing actin and myosin filaments
  • Three types: skeletal (voluntary, striated, multinucleated), smooth (involuntary, no striations), cardiac (striated, mostly involuntary, bound by intercalated disks, relies on pacemaker cells)

  
• Nervous Tissue


  • Conducts electrical impulses and conveys information
  • Includes neurons (transmit information), neuroglia (support and nourish neurons), and nerves (bundles of fibers outside brain and spinal cord)
• Nervous System Functions


  • Sensory input - sensory receptors detect changes and transmit information to spinal cord and brain
  • Data integration - spinal cord and brain integrate data and decide on appropriate response
  • Motor output - response is transmitted to effector (gland or muscle) which initiates the actual response
• Organ


  Composed of two or more tissue types working together for a particular function
• Organ System


  Composed of various organs that cooperate to carry out a general process
• Body Cavities


  • Dorsal cavity (cranial cavity, vertebral canal)
  • Ventral cavity (thoracic cavity, abdominal cavity, pelvic cavity)
• Integumentary System


  • Covers and protects underlying body regions
  • Regulates body temperature
  • Contains sensory receptors
• Regions of the Skin


  • Epidermis
  • Dermis
  • Subcutaneous Layer
• Epidermis


  • Stratified squamous epithelium
  • New cells pushed outward, become keratinized, and sloughed off
  • Melanocytes produce melanin
  • UV radiation can cause skin cancer
• Dermis


  • Fibrous connective tissue containing elastic and collagen fibers
  • Contains receptors, nerve fibers, blood vessels

  
• Subcutaneous Layer


  Loose, connective tissue located below dermis

  
• Accessory Structures of Human Skin

  • Nails
  • Hair follicles
  • Sweat glands
• Homeostasis


  The ability of an organism to maintain a relatively constant internal environment
• Organ Systems Contributing to Homeostasis


  • Digestive system
  • Respiratory system
  • Liver and kidneys
• Homeostatic Control


  • Partially controlled by hormones
  • Ultimately controlled by the nervous system
• Negative Feedback


  The primary homeostatic mechanism that keeps a variable close to a set value
• Positive Feedback


  A mechanism that brings about an ever greater change in the same direction, does not result in equilibrium, not as common as negative feedback