Bio 150 lecture 3 notes

• Tissue


  a group of similar cells that arise from the same region of the embryo and work together to perform a specific function in an organ.
• Histology


  the microscopic study of tissues and how they are arranged into organs
• Four types of tissues:


  -Epithelial tissue

  -Connective tissue

  -Nervous tissue

  -Muscular tissue
• Epithelial Tissue:


  - Flat sheet of closely adhering cells

  -One or more cells thick

  -Upper surface usually exposed to the environment or an internal space in the body

  -Covers body surface

  -Lines body cavities

  -Forms the external and internal linings of many organs

  -Constitutes most glands

  -Extracellular material is so thin it is not visible with a light microscope

  -Epithelia allows no room for blood vessels

  -Lie on a layer of loose connective tissue and depend on its blood vessels for nourishment and waste removal
• Basement membrane

  - layer between an epithelium and the underlying connective tissue

  -Anchors the epithelium to the connective tissue below it
• Basal surface

  - surface of an epithelial cell that faces the basement membrane
• Apical surface


  -surface of an epithelial cell that faces away from the basement membrane
• Simple epithelium


  -Contains one layer of cells

  -Named by shape of cells

  -All cells touch the basement membrane
• Stratified epithelium


  -Contains more than one layer

  -Named by shape of apical cells

  -Some cells rest on top of others and do not touch basement membrane
• simple squamous epithelium


  - rapid diffusion and transport:

  
  

  - Endothelium of blood vessels

  -Mesothelium of serous membranes

  - Alveoli of lungs, parts of kidney tubules
• Simple cuboidal


  - secretion and absorption: Kidney tubules and ducts of glands
• Simple columnar


  - secretion and absorption: Digestive system and female reproductive system
• Pseudostratified columnar


  - Looks stratified - not all cells reach the free surface but every cell reaches the basement membrane

  - Lines the respiratory tract
• Goblet cells


  -mucus secreting cells found in simple columnar and pseudostratified epithelia
• Stratified Epithelia


  - Range from 2 to 20 or more layers of cells

  - Specialized for resistance to physical wear and tear

  - Named for the shapes of their apical cells
• Stratified squamous


  - Most common

  - Skin (keratinized) and mucosa (non-keratinized)
• Stratified cuboidal


  glands and ducts (uncommon)
• Stratified columnar


  - glands and ducts (uncommon)
• Transitional epithelium


  - Urinary bladder and ureters

  - Transitions between cuboidal (relaxed) and squamous (when stretched)
• Connective tissue


  - Connects cells and tissues

  - Cells are dispersed in an extra cellular matrix composed proteins and a fluid or solid ground substance.

  Functions:
• Connective tissue Functions

  Binding of organs - tendons and ligaments

  Support - bones and cartilage

  Physical protection - cranium, ribs, sternum, organ capsules

  Immune protection - white blood cells attack foreign invaders

  Movement - bones provide lever system

  Storage - fat, calcium, phosphorus

  Heat production - metabolism of adipose tissue

  Transport - blood and lymph
• Cells:

  Fibroblasts


  - produce fibers and ground substance
• Mesenchymal cells


  multipotent stem cells that can differentiate into any type of connective tissue cells (for repair and healing)
• Macrophages


  - phagocytize foreign material and activate immune system when sense foreign matter (antigen)

  - Arise from white blood cell - monocytes
• Leukocytes


  - white blood cells
• Neutrophils


  wander in search of and attacking bacteria
• ymphocytes


  react against bacteria, toxins, and other foreign material
• Plasma cells


  - synthesize disease fighting antibodies Arise from lymphocytes
• Mast cells


  - found along side of blood vessels

  - Secrete heparin inhibits clotting

  - Histamine that dilates blood vessels
• Adipocyte


  - store triglycerides (fat molecules)
• Collagen fibers


  - Tough, flexible, and resist stretching and tearing (tensile strength)

  - Tendons, ligaments, and deep layer of the skin are mostly collagen
• Reticular fibers

  - Thin collagen fibers coated with glycoprotein

  - Form structural framework (stroma) of such organs as spleen and lymph nodes
• Elastic fibers


  - Made of protein called elastin

  = Allows stretch and recoil
• Ground substance:


  Made of proteoglycans (made up of hyaluronic acid and proteins) that combine with water to form a clear, viscous (thick), colorless gelatinous matrix.
• Adipose Tissue:


  - Fat storage

  - Little extracellular matrix

  Lots of blood vessels

  - Insulation, shock absorption, energy storage
• Areolar Tissue


  - Fills the spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal cavity

  - Underlies most epithelia

  - Web-like network rich in nerves and blood vessels to feed surrounding tissues.
• Reticular Tissue:


  Mesh-like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver
• Dense Connective Tissue


  More collagen than loose connective tissue makes dense connective tissue more resistant to stretching
• Dense Regular Connective Tissue:
• Dense Irregular Connective Tissue:


  - Random fiber directions gives strength in all directions

  - Ex. Dermis of skin, walls of arteries