Download Chapter 5 Tissues

Chapter 5
Tissues
Principal Types of Tissue
• Epithelial tissue
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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
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
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
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
Epithelial Tissue
• Functions
– Protection
• 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
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
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
Epithelial Tissue
• Classification of epithelial tissue
– Membranous (covering or lining) epithelium (Table
5-1)
• Classification based on cell shape (Figure 5-2)
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Squamous
Cuboidal
Columnar
Pseudostratified columnar
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
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
Simple Squamous Epithelium
Simple Cuboidal Epithelium
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
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
Pseudostratified Ciliated Epithelium
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
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
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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
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
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
Exocrine Glands in the Stomach
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
Exocrine Glands