1. Chapter 5 Tissues

2. Principal Types of Tissue
Epithelial tissue
Covers and protects the body surface
Lines body cavities
Secretion, excretion, absorption
Forms many glands
Connective tissue
Supports the body and it parts
Connects and holds parts together
Transports substances and protects from foreign invaders
Separated by large quantities of nonliving matrix

3. Principal Types of Tissue
Muscle tissue
Produces movement
Contractility
Nervous tissue
Most complex tissue
Communication between various parts of the body and in integration of their activities
Generation of complex messages for the coordination of body functions

4. Embryonic Development of Tissues
Tissues appear in the embyonic period of development
First two months after conception
Zygote divides repeatedly
Blastocyst implants in uterus
Gastrulation produces three primary germ layers
Endoderm – epithelial tissue
Mesoderm – epithelial, connective and muscle tissue
Ectoderm – epithelial and nerve tissue
Histogenesis
The process by which the primary germ layers differentiate into different kinds of tissue

6. Epithelial Tissue Types and locations
Epithelium is divided into two types:
Membranous (covering or lining) epithelium
Covers the body and some of its parts
Lines the cavities, vessels, and tracts
Glandular epithelium
Grouped in solid cords or specialized follicles that form the secretory units of endocrine and exocrine glands

7. Epithelial Tissue Functions Protection Sensory functions Secretion
Most important function of membranous epithelium
Sensory functions
Skin, nose, eye, and ear
Secretion
Glandular epithelium
Hormones, mucus, digestive juices, and sweat
Absorption
Lining epithelium of the gut and respiratory tract allow for absorption of nutrients and exchange of gases between the lungs and the blood
Excretion
Lining of the kidney tubules makes the excretion and concentration of excretory products in the urine possible

8. Epithelial Tissue Generalizations about epithelial tissue
Limited amount of matrix material
Appear to be continuous sheet of cells when view under the microscope
Membranous type is attached to a noncellular layer of adhesive, permeable material called the basement membrane
Basement membrane is attached to connective tissue
B.M. is synthesized by the epithelia and connective tissue
Basal lamina - glycoprotein material made by epithelium
Reticular lamina –fibers made by connective tissue

9. Epithelial Tissue Generalizations about epithelial tissue Avascular
Contains no blood vessels
Oxygen and nutrients must diffuse from capillaries in the connective tissue through the B.M. to reach epithelium
Many desmosomes and tight junctions
Capable of reproducing itself
Frequent cell division
Considerable wear and tear require rapid regeneration

10. Epithelial Tissue Classification of epithelial tissue
Membranous (covering or lining) epithelium (Table 5-1)
Classification based on cell shape (Figure 5-2)
Squamous
Cuboidal
Columnar
Pseudostratified columnar

11. Epithelial Tissue Classification of epithelial tissue (cont.)
Classifications based on layers of cells (Table 5-1)
Simple epithelium
Cells in a single layer
Stratified epithelium
Cells are layered one on another
Transitional epithelium
Differing cell shapes in a stratified, or layered, sheet
Stratified tissue types are named for the shape of the cells in their top layer only

13. Epithelial Tissue Classification of epithelial tissue (cont.)
Classifications based on layers of cells (Table 5-2)
Simple epithelium
Simple squamous epithelium (Figures 5-2, 5-3, 5-4)
One-cell layer of flat cells
Permeable to many substances
Examples: endothelium—lines blood vessels; mesothelium—pleura
Simple cuboidal epithelium (Figure 5-5)
One-cell layer of cuboidal cells
Found in many glands and ducts

14. Simple Squamous Epithelium

15. Simple Cuboidal Epithelium

16. Epithelial Tissue Simple epithelium (cont.)
Simple columnar epithelium (Figure 5-6)
Single layer of tall, column-shaped cells
Cells often modified for specialized functions
goblet cells (secretion)
cilia (movement)
microvilli (absorption)
Often lines hollow visceral structures

17. Epithelial Tissue Simple epithelium (cont.)
Pseudostratified columnar epithelium (Figure 5-7)
Columnar cells of differing heights
All cells rest on basement membrane but may not reach the free surface above
Cell nuclei at odd and irregular levels
Found lining air passages and segments of male reproductive system
Motile cilia and mucus are important modifications

18. Pseudostratified Ciliated Epithelium

19. Epithelial Tissue Stratified epithelium
Stratified squamous (keratinized) epithelium
Multiple layers of flat, squamous cells (Figure 5-8)
Cells filled with keratin
Covers outer skin on body surface
Stratified squamous (nonkeratinized) epithelium (Figure 5-9)
Lines vagina, mouth, and esophagus
Free surface is moist
Primary function is protection

20. Epithelial Tissue Stratified epithelium (cont.)
Stratified cuboidal epithelium
Two or more rows of cells are typical
Basement membrane is indistinct
Located in sweat gland ducts and pharynx
Stratified columnar epithelium
Multiple layers of columnar cells
Only most superficial cells are typical in shape
Found in in very few places in the body
Located in segments of male urethra and near anus

21. Epithelial Tissue Stratified epithelium (cont.)
Stratified transitional epithelium (Figure 5-10)
Located in lining of hollow viscera subjected to stress (e.g., urinary bladder)
Often 10 or more layers thick
Protects organ walls from tearing by changing from cuboidal to squamous in appearance

22. Epithelial Tissue Glandular epithelium
Specialized for secretory activity
Exocrine glands—discharge secretions into ducts
Endocrine glands—“ductless” glands; discharge secretions directly into the blood or interstitial fluid
Structural classification of exocrine glands (Figure 5-12; Table 5-2)
Multicellular exocrine glands are classified by the shape of their ducts and the complexity of their duct system
Tubular and alveolar are saclike
Simple exocrine glands—only one duct leads to the surface
Compound exocrine glands—have two or more ducts

23. Exocrine Glands in the Stomach

24. Epithelial Tissue Glandular epithelium (cont.)
Functional classification of exocrine glands (Figure 5-12)
Apocrine glands
Secretory products collect near apex of cell and are secreted by pinching off the distended end
Secretion process results in some damage to cell wall and some loss of cytoplasm
Mammary glands are good examples of this secretory type
Holocrine glands
Secretion products, when released, cause rupture and death of the cell
Sebaceous glands are holocrine
Merocrine glands
Secrete directly through cell membrane
Secretion proceeds with no damage to cell wall and no loss of cytoplasm
Most prevalent gland type

25. Exocrine Glands