TISSUES

• The body contains at least 200 distinct cell types. These cells contain essentially the same internal structures yet they vary enormously in shape and function.
• The different types of cells are not randomly distributed throughout the body; rather they occur in organized layers, a level of organization referred to as tissue.
• The variety in shape reflects the many different roles that cells fulfill in your body.
• The human body starts as a single cell at fertilization.
• Four broad categories of tissues

  • Epithelial
  • Connective
  • Muscle
  • Nervous
• Cell shapes

  • Squamous (flattened and thin)
  • Cuboidal (boxy, as wide as it is tall)
  • Columnar (rectangular, taller than it is wide)
• Number of cell layers

  • One (simple epithelium)
  • More than one (stratified epithelium)
  • Pseudostratified (false stratification)
  • Transitional
• Simple cuboidal epithelium


  • Active in the secretion and absorption of molecules
  • Lining of kidney tubules
  • Ducts of glands
• Simple columnar epithelium


  • Active in the absorption and secretion of molecules
  • Lining of some sections of the digestive system
  • Parts of the female reproductive tract
• Ciliated columnar epithelium


  • Simple columnar epithelial cells with cilia on their apical surfaces
  • Found in the lining of the fallopian tubes and parts of the respiratory system, where the beating of the cilia helps remove particulate matter
• Pseudostratified columnar epithelium


  • Appears to be stratified but consists of a single layer of irregularly shaped and differently sized columnar cells
  • Found in the respiratory tract, where some of these cells have cilia
• Stratified epithelium


  • Several stacked layers of cells
  • Protects against physical and chemical wear and tear
• Stratified squamous epithelium


  • Mammalian skin
  • Lining of the mouth cavity
• Stratified cuboidal epithelium and stratified columnar epithelium


  Can be found in certain glands and ducts, but are uncommon in the human body
• Transitional epithelium


  • Found only in the urinary system (ureters and bladder)
  • Gradual changes in the shapes of the apical cells as the bladder fills with urine
• Dense regular connective tissue


  Collagenous fibers packed into parallel bundles
• Dense irregular connective tissue


  Collagenous fibers interwoven into a mesh-like network
• Reticular tissue


  Loose connective tissue made up of a network of reticular fibers that provides a supportive framework for soft organs
• Areolar tissue


  Loose connective tissue widely spread throughout the body, containing all three types of fibers (collagen, elastin, and reticular) with much ground substance and fibroblasts
• Adipose tissue


  Loose connective tissue that consists of fat cells with little extracellular matrix, stores fat for energy and provides insulation
• Bone connective tissue

  • Two types: compact and spongy
• Types of cartilage


  • Hyaline cartilage (provides support with some flexibility)
  • Fibrocartilage (provides some compressibility and can absorb pressure)
  • Elastic cartilage (provides firm but elastic support)
• Blood


  Fluid connective tissue containing erythrocytes and various types of leukocytes that circulate in a liquid extracellular matrix
• Muscle tissue


  • Characterized by properties that allow movement
  • Muscle cells are excitable and respond to a stimulus
  • Muscle cells are contractile and can shorten to generate a pulling force
  • Some muscle movement is voluntary and under conscious control
• Neuron


  • The cell body of a neuron, also called the soma, contains the nucleus and mitochondria
  • The dendrites transfer the nerve impulse to the soma
  • The axon carries the action potential away to another excitable cell
• Nervous tissue


  • Characterized as being excitable and capable of sending and receiving electrochemical signals that provide the body with information
  • Two main classes of cells: neuron and neuroglia
  • Neuroglia play an essential role in supporting neurons and modulating their information propagation
• a DISRUPTION of the structure is a sign of injury or disease
• Epithelial tissue - also referred to as the epithelium
• Epithelial tissue - refers to the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands
• Connective tissue - binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body
• Muscle tissue - responds to stimulation and contracting to provide movement
• Nervous tissue - allows the propagation of ELECTROCHEMICAL SIGNALS in the form of nerve impulses that communicate between different regions of the body
• Simple epithelium

  • one
  • where every cell rests on the basal lamina
• Stratified epithelium

  • more than one
  • only the basal layer of cells rests on the basal lamina
• Pseudostratified

  • describes tissue with a single layer of IRREGULARLY SHAPED CELLS that give the appearance of more than one layer.
• pseudo = false
• Transitional

  • describes a form of specialized stratified epithelium in which the shape of the cells can vary.
• Simple Squamous Epithelium

  • appearance of thin scales
  • nuclei tend to be flat, horizontal, and elliptical, mirroring the form of the cell
• The endothelium is the epithelial tissue that lines vessels of the lymphatic and cardiovascular system, and it is made up of a single layer of squamous cells
• the thinness of the cell allows rapid passage of chemical compounds is observed