1. Tissues- A group of similar cells that perform a common function.
Ch. 5

2. Types of Tissues
Epithelial- covers & protects the body surface, lines body cavities, moves substances in & out of blood, and forms many glands.
Connective Tissue- Supports body, holds body parts together, transports substances through the body & protects it from foreign invaders.

3. Embryonic Development of Tissues
After fertilization, the cell divides and becomes a hollow ball of cells called a blastocyst. These cells regroup and form the three primary layers (gastrulation):
Endoderm
Mesoderm
Ectoderm
These layers then differentiate into tissues (histogenesis)

4. Functions of Epithelial Tissue
Protection- from injury & foreign particles
Sensory- found in skin, nose, eye & ear
Secretion- include hormone, mucus, digestive juices & sweat.
Absorption- of nutrients & gases in lungs
Excretion- kidney & urine

5. Classification Based on Cell Shape
Four cell shapes:
squamous: flat & platelike
cuboidal: cube-shaped
columnar: narrow & cylindrical
pseudostratified columnar: oddly shaped with some nuclei near the top & some near the bottom of the cell
(Figure 5-2)

6. Classification Based on Layers of Cells
Simple- cells arranged in a single layer
Stratified- cells layered one on another
Transitional- differing cell shapes in a stratified or layered sheet
(Figure 5-2)

8. Simple Squamous Epithelium
One layer of flat, scalelike cells.
Substances can readily diffuse or filter through.
Examples include the microscopic air sacs (alveoli) in the lungs & lining of blood vessels)
(Figure 5-5)

9. Simple Cuboidal Epithelium
One layer of cuboidal cells
Found in many types of glands & ducts.
Also found in organs, such as the kidney.

10. Simple Columnar Epithelium
Lines the stomach, intestine, uterus, uterine tubes, and parts of the respiratory tract.
Because these cells are larger they offer more protection while still allowing secretion/absorption to take place.

11. Pseudostratified Columnar Epithelium
Found lining the air passages of the respiratory system & certain segments of the male reproductive system such as the urethra.
Cells are of differing heights

12. Stratified Squamous Epithelium
Multiple layers of flat cells
Some are composed of keratin (helps protect & waterproof) & are found in the skin
Others are nonkeratinized and are found in the vagina, mouth & esophagus

13. Stratified Cuboidal Epithelium
Generally serves as protection
Located in sweat gland ducts, in the pharynx & over parts of the epiglottis

14. Stratified Columnar Epithelium
Not common in the body
Found only in parts of the male urethra & in the mucous layer near the anus

15. Stratified Transitional Epithelium
Has the ability to stretch & flatten out
Found in the walls of the bladder
Protects the bladder wall from tearing when stretched

16. Exocrine Glands- discharge their secretions into ducts
Endocrine Glands- discharge their secretions directly into the blood

17. Types of Exocrine Glands
Apocrine glands- Milk producing Ex. mammary glands
Holocrine glands- produce oil to lubricate the skin
Merocrine glands- Salivary glands

19. Connective Tissue
Connective tissue connects, supports, transports and defends.
Connects tissue to tissue, muscle to muscle, bone to muscle and bones to bones.
Blood is a connective tissue that transports substances between parts of the body
Other connective tissue cells defend us against microorganisms & invaders

20. Loose Connective Tissue
Stretchable & widely distributed around the body
Not as specialized as other connective tissue

21. Adipose Tissue
Forms a protective barrier around the kidneys & other various structures
Storage for excess food
Insulates the body to conserve heat

23. Reticular Tissue
Forms the framework of the spleen, lymph nodes & bone marrow.
Helps defend the body against foreign substances

24. Dense Fibrous Tissue Is flexible but very strong
Tendons & ligaments are made of this
Forms the strong inner skin layer called the dermis
Also forms the outer layer of organs like the kidney & the spleen