ap150 - tissues/epithelial tissues objectives

tissue

• cells + matrix

  • matrix: non-living material around/between cells

epithelial tissue basics

• covering, barriers, secretion/absorption

  • creates boundaries

connective tissue

• connects, protects, bears weight

  • binds body parts together, shape, weight

shared epithelial tissue characteristics

• cellular (little matrix)

  • cells are tightly packed

• covers/lines surfaces

  • enables tissue to act as a barrier

• polarity

  • top - apical surface

  • bottom - basal surface

• attached to the material it covers by a basement membrane

• avascular

  • no direct blood supply

  • obtains O2 and nutrients by diffusion from nearby blood vessels

• cells divide rapidly (mitotically active/regenerative)

  • many cancers are epithelial in origin

    • high rate of division = higher mutation rate

• innervated

  • contains sense receptors and neurons/nerves

layers of epithelial tissue

• simple = 1 layer

• stratified = 2+ layers

shape of epithelial tissue

• squamous = flattened (fried egg)

• cuboidal = cube (square)

• columnar = tall and thin (column)

cell volume and functions

• least active:

  • squamous

• more active:

  • cuboidal

• most active:

  • columnar

thickness of simple epithelium vs stratified epithelium

• simple epithelium

  • highly permeable

    • less physically protective

• stratified epithelium

  • low permeability

    • very protective

simple squamous (endothelium/mesothelium)

• thin, low volume cells

  • quick and easy to get through (highly permeable)

    • diffusion, osmosis, & filtration

      • passive process

• found in alveoli, capillaries, kidneys

simple cuboidal

• thin enough to be readily passed through

  • cells are large enough to be active

    • absorption:

      • active transport into cells and/or across epithelial layer

        • transport proteins, endo/exocytosis

    • secretion:

      • active creation of substances for release

• found in: kidneys and sweat glands

simple columnar

• thin enough to be readily passed through

  • cells are large enough to be active

    • absorption:

      • active transport into cells and/or across epithelial layer

        • transport proteins, endo/exocytosis

    • secretion:

      • active creation of substances for release

    • contains goblet cells

      • produces mucin

        • mucin + water = mucus

• found in: intestines

  • productive of enzymes for digestion

  • transport of nutrients out of the intestines through epithelium

  • release of materials into the intestines

psuedostratified ciliated columnar epithelium

• single layer of irregular cells with cilia

• found in respiratory tract: nasal cavity, pharynx, larynx, trachea, bronchi

• contains goblet cells

• cilia: sweeps away dirty mucus

stratified squamous

• many layers of cells, apical cells, squamous shape

• thick layer

• difficult to pass through (low permeability)

• highly protective

• found in: skin & oral cavity

glands

• clump of epithelial cells designed for producing and releasing substances

  • secretion

    • sweat, saliva, enzymes, hormones

exocrine glands

• secretion releases through a duct (tube)

endocrine glands

• secretion released directly into blood or interstitial space (spaces between cells)

  • creates substances that are released in cells

microvilli

• make cells better at absorbing

cilia

• beat & sweep materials ALONG apical surface

connective tissue

• cells + fibers + ground substance

  • CT typically have lots of matrix

common components of connective tissue proper

• cells

  • fibroblasts

    • makes proteins/fibers

  • adipocytes

    • stores lipids/triglycerides

  • macrophages

    • removes debri & pathogens

  • plasma cells

    • release antibodies

  • mast cells

    • release heparin & histamine

• matrix fibers

  • elastic fibers

    • stretch & recoil

  • collagen fibers

    • strong

    • inelastic

    • pink

  • reticular fibers

    • form a loose mesh for cells to hold onto

areolar connective tissue

• mixture of all 3 matrix fibers

  • fibroblasts are common

• fibers are loosely binded

  • widely spaced

• gel-like ground substance

  • vascular: abundant blood vessels

• function:

  • supportive tissue that loosely binds materials together, but allows independent movement of objects

adipose fat tissue

• adipocytes

  • stores and (creates) lipids/triglycerides

• fibers:

  • no notable amount of fibers

• vascular: abundant blood vessels

  • subcutaneous, intramsuclar, & visceral fat

• function:

  • create, store, and release lipids

    • store energy for future use/energy reserve

  • soft, protective, space-filling material

  • thermally insulates

  • releases hormones; endocrine function

dense collagenous irregular connective tissue

• predominately fibroblasts

• fibers:

  • predominantly collagen

    • tightly packed

    • multiple directions/orientations

• functions:

  • tensile strength in multiple directions

  • bind/hold things together against multidirectional loads/forces

dense collagenous regular connective tissue

• predominately fibroblasts

• fibers:

  • predominantly collagen

    • tightly packed

    • simple direction/orientation

• functions:

  • tensile strength in multiple directions

  • bind/hold things together against multidirectional loads/forces

POORLY VASCULARIZED = heals slowly