- Explain how cells form a tissue, with the digestive system as an example.
Chapter 4 : page 161 to 172
- Able to recognize and name different types of epithelia.
- Able to explain the relation between shape and function of different types of
epithelia.
- Able to name cellular characteristics, and associated functions, of epithelia.
- Able to name intracellular connections, and associated functions, between epithelial
cells.
4 basic types of tissue:
- Epithelial tissue first layer on top of an organ (skin)
- Connective tissue connects epithelial and muscle tissue
- Muscle tissue movement for digestion (can contract)
- Nervous tissue the muscle tissue is innovated by this
Ectoderm: nervous tissue, skin
Endoderm: digestive tissue. Lung
Mesoderm: muscle, connective tissue (from mesenchyme)
An epithelium is a tissue existing of cells that are tightly connected to each other. It is
derived from one of the three primary germ layers (ecto-, endo- or medo-derm)
There are two types:
- Covering epithelia (skin)
- Glands (invagination of epithelial layers)
An epithelium is classified based on its embryonic origin, morphology and cell organization:
- Ecto-, endo-, or mesodermal
- The chape of the cells
- Number of cell layers (strata)
Cell layers:
- Simple: one layer of cells, (cuboidal)
- Stratified:
o Stratified: squamous
o Pseudo-stratified: pseudostratified columnar
looks stratified, but is actually not.
Characteristics of epithelia:
- No blood circulation
- Polarized (apical (top) and baso (bottom) -lateral (side))
- Surface specializations
- Presence of a basal membrane