1. Tissue Level Of Organization

2. The Tissue Level of Organization
Group of similar cells
common embryonic origin
common function
bound together by intercellular substance
Histology
study of tissues

3. The Origin of Tissues
Morula
Blastula
Gastrula

4. 4 Basic Tissues Categories
Epithelial
Connective
Muscle
Nervous

5. Epithelial Tissue -- General Features
Cover surfaces, line cavities and form glands
FUNCTION – To create tissue that line, cover, protect, secrete. Tend to act as a barrier or covering.
Attached to underlying connective tissue by a basement membrane.
Cells are tightly packed together, to form tight network.
Avascular---without blood vessels
nutrients diffuse in from blood vessels in underlying connective tissue
What does this mean for especially thick epithelia like skin?
Rapid cell division; responsive to environmental stresses.
Named according to the SHAPE and ARRANGEMENT of cells.

6. Epithelial Tissues and Their Basement Membrane

7. Simple Squamous Epithelium
Single layer (= SIMPLE) of flat cells (Squamous).
lines blood vessels, form capillary walls, form alveoli.
VERY THIN LAYER--.
What is the primary function of this tissue?

8. Examples of Simple Squamous Epithelium
Section through lungs
Why would simple squamous be a good design for alveoli ?
Surface view of lining of peritoneal (abdominal) cavity

9. Simple Cuboidal Epithelium
Single layer of cube-shaped cells viewed from the side.
Cuboidal cells usually are found lining/forming gland ducts.

10. Example of Simple Cuboidal Epithelium
Sectional view of kidney tubules.

11. Nonciliated Simple Columnar
Unicellular glands =goblet cells secrete mucus
lubricate GI, respiratory, reproductive and urinary systems.
Microvilli = fingerlike cytoplasmic projections on the cell membrane’s top surface. Microvilli are designed to increase surface area to increase absorption.

12. Example Nonciliated Simple Columnar Epithelium
Section from small intestine
The term “brush border” is often used to describe this tissue.
Why is having increased surface area along surface of small intestine a good design?

13. Ciliated Simple Columnar Epithelium
Single layer of rectangular cells with cilia, cilia are locomotive structures that consist of a 9 +2 arrangement of microtubules that are covered with cell membrane.
Mucus from goblet cells moved along by cilia.
Why would we want the bronchi and bronchioli lined with this type of tissue?

14. Example Ciliated Simple Columnar Epithelium
Section of fallopian tube.
Why would we want this structure lined with cilliated columnar cells?

15. Stratified Squamous Epithelium
Several cell layers thick
Surface cells flat
Keratinized = surface cells dead and filled with Keratin protein
Examples include the skin (epidermis) and mucous membranes (non-keratinized)
What do you think the the primary function of this type of epithelium is all about?

16. Example of Stratified Squamous
Section of vagina

17. Stratified Cuboidal Epithelium
Multilayered
Surface cells cuboidal
rare (only found in sweat gland ducts & male urethra)

18. Stratified Columnar Epithelium
Multilayered
Surface cells columnar
Rare (very large ducts & part of male urethra)

19. Transitional Epithelium
Multilayered
Surface cells varying in shape from round to flat if stretched
Lines hollow organs of the urinary tract that expand from within.
Perfect example is the urinary bladder

20. Pseudostratified Columnar
PSEUDO = FALSE
Single cell layer
All cells attach to basement membrane but not all reach free surface
Nuclei at varying depths
Non-Ciliated version found in part of male Urethra and in Vas Deferens
Ciliated version found in Trachea

21. EPITHELIAL Tissues