Tissues: The Living Fabric (Ch.4)

What is tissue?

Groups of cells similar in structure and function

What are the 4 types of tissues?

Epithelial, Connective, Muscle, and Nerve

What are the two types of epithelial tissue?

Covering and Lining epithelia & Glandular Epithelia

What is covering and lining epithelia?

External and internal surfaces epithelial tissue (skin, digestive tract, etc.)

What is Glandular epithelia?

Secretory tissue in glands

What are the characteristics of Epithelial Tissue?

1. Cell have polarity (different charges) and asymmetry (different surface)

2. Are composed of closely packed cells

3. Supported by a connective tissue reticular lamina (under the basal lamina)

4. Avascular (No blood vessels) but innervated (has nerves)

5. High rate of regeneration (cell division quickly)

How do epithelial tissue have polarity and nonpolarity?

Circular (non-polarity); Circular with a basement membrane (polarity)

Explain cells polarity with apical and basal surfaces

Apical - has a top and are free; (apical surface may bear microvilli or cilia)

Basal - has a basement membrane (ex. basal lamina, reticular lamina); non-cellular basal lamina of glycoprotein and collagen lies adjacent to basal surface

How are epithelial tissue closely packed cells?

Continuous sheet held together by tight junctions and desmosomes

What is the basement membrane made up of?

Basal and reticular lamina

Why is cancer dangerous in epithelial cells?

Cancerous epithelial cells are not contained by the basement membrane boundary.

They penetrate the boundary and invade underlying tissues, resulting in spread of cancer

How do you classify epithelial layers?

1 layer = simple epithelium; all cells touch basement membrane

>1 layer = stratified epithelium; only most basal layer touches basement membrane

How do you name an epithelial cell that is stratified?

The name of a stratified tissue cell is based on the apical cell type

What are the 3 types of cell shapes?

Squamous (flat), Cuboidal (cube), Columnar (column)

Description, Function, and Location of simple squamous epithelium

Description: single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia;

Function: Allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae

Location: Kidney glomeruli; air sacs of longs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae)

What are the two important location of simple squamous epithelia?

Endothelium: the lining of lymphatic vessels, blood vessels, and heart

Mesothelium: The epithelium of serous membranes in the ventral body cavity

Description, Function, and Location of simple cuboidal epthelium

Description: single layer of cubelike cells with large, spherical central nuclei.

Function: Secretion and absorption

Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface

Description, Function, and Location of simple columnar epithelium

Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular gland (goblet cells)

Function: Absorption; secretion of mucus, enzyme , and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action

Location: Nonciliated - most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands

Ciliated - lines small bronchi, uterine tubes, and some regions of the uterus

Description, Function, and Location of pseudostratified columnar epithelium

Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia

Function: Secretion, particularly of mucus; propulsion of mucus by ciliary action

Location: Nonciliated type: in male’s sperm-carying ducts and ducts of large glands;

Ciliated variety: lines the trachea, most of the upper respiratory tract

Where is Stratified cuboidal found and how many layers does it have?

Found in some sweat and mammary glands; quite rare in body

Typically two cell layers thick

What is the location of Stratified Columnar

Small amounts in pharynx, male urethra, and lining some glandular duct

Also occurs at transition areas between two other types of epithelia

Limited distribution in body

Description, Function, and Location of stratified squamous epithelium

Description: Thick membrane composed of several cell layer; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of dead keratin; basal cells are active in mitosis and produce the cells of the more superficial layers.

Function: Protects underlying tissues in areas subjected to abrasion

Location: Nonkeratinized - forms the moist lining of the esophagus, mouth, and vagina

Keratinized - variety forms the epidermis of the skin, a dry membrane

Description, Function, and Location of Transitional epithelium

Description: Resembles both stratified squamous and stratified cuboidal; basal cell cuboidal or columnar; surface cell dome shaped or squamouslike, depending on degree of organ stretch

Function: Stretches readily and permits distension of urinary organ by contained urine

Location: Lines the ureters, urinary bladder, and part of the urethra

What is Glandular Epithelia and how is it classified?

A gland is one or more cells that makes and secretes a fluid

Classified by: Sites of produce release - endocrine or exocrine; Relative number of cells forming the gland - unicelluar (e.g. goblet cells) or multicellular

What is endocrine glands and what is the function?

Ductless glands

Secrete hormones that travel through lymph or blood to target organs

What is Exocrine glands and what is it function

Secret products into ducts.

Secretions released onto body surfaces (skin) or into body cavities

Ex. mucous, sweat, oil, and salivary glands

(More numerous than endocrine glands)

What is an example of Unicellular Exocrine glands?

Goblet Cell - lines the inside of organs in the respiratory, gastorintestinal, and reproductive tracts to produce and secrete mucus

What are multicellular exocrine glands composed of?

Multicellular exocrine glands are composed of a duct and a secretory unit?

Classified according to: 1. Duct type (simple or compound) 2. Structure of their secretory units (tubular, alveolar, or tubuloalveolar)

What are the 3 modes of secretion and what are their function?

Merocrine: Products are secreted by exocytosis (e.g. pancreas, sweat and salivary glands)

Holocrine: Product are secreted by rupture of gland cells (e.g., sebaceous gland)

Apocrine: Over active merocrine gland that looks as if the apical portion of the cells are rupturing (apocrine sweat glands)