Lecture 2: Lecture 2: Tissue Types & Epithelium

Tissues

Related cells with similar properties and common functions, individual body cells are specialized, and each type performs specific functions that maintain

homeostasis

4 basic types of tissues

Epithelium

Connective tissue (Bone, Cartilage, Blood, Connective Tissue Proper)

Muscle tissue

Nervous tissue

Epithelium

Covers body surface or lines cavities

Connective tissue

Few cells, lots of extracellular matrix (ground

substance & fibers). 4 types: CT proper, Loose = areolar, adipose, reticular; Dense = regular, irregular, elastic, | Cartilage: Hyaline, Elastic, Fibrocartilage | Bone: Compact, Spongy | Blood

Muscle Tissue

body movements, contractions, skeletal, cardiac, smooth

Nervous Tissue

brain, spinal cord, nerves, neurons, dendrites

Properties of Epithelial Tissue

1. Rests on basement membrane (or basal lamina), supported byconnective tissue

2. Polarized: apical, lateral, and basal sides of cells and tissues

3. Highly Cellular: little/no extracellular matrix

4. Specialized cell contacts bind cells into sheets

5. Avascular, but innervated: nourishment by diffusion throughbasement membrane

6. High regenerative capacity through mitosis

Surface modifications

Cilia, Microvilli, Keratinization, Goblet cells and Stereocilia

Types of Epithelia

Simple squamous, Simple cuboidal, Simple columnar, Pseudostratified columnar, Stratified squamous, Stratified cuboidal, Stratified columnar, Transitional

Label Epithelial Tissue

Layers + cell shape + "epithelium" + any

surface modifications

Simple Squamous Epithelium

Allows passage of materials by

diffusion and filtration in sites where

protection is not important - NO SURFACE MODIFICATIONS

Location of Simple Squamous Epithelium

Kidney glomeruli, alveoli, peritoneum,

serous pericardium, pleurae

Stratified Squamous Epithelium

To shield underlying structures from mechanical stress, abrasion, dehydration, and pathogen invasion - Keratinized or Non Keratinized

Location of Stratified Squamous Epithelium

Mouth, esophagus, vagina, skin

Simple Cuboidal Epithelium

Single layer of cubelike cells with large central nuclei, usually involved in secretion/absorption. - NO MODIFICATIONS

Location of Simple Cuboidal Epithelium

Kidney tubules, small glands, ovaries

Simple Columnar Epithelium

The nuclei of simple columnar epithelium are all at the same level, near the basal surface. Absorption, secretion, and protection. - Cilia, Microvilli, Goblet cells, Stereocilia.

Location of Simple Columnar Epithelium

Digestive tract, gall bladder, small bronchi,

uterine tube, uterus

Pseudostratified Columnar Epithelium

Pseudostratified columnar epithelium has a single cell layer. Looks like more because the nuclei are at different levels. Absorption, secretion, and protection. - Cilia, Microvilli, Goblet cells, Stereocilia.

Location of Pseudostratified Columnar Epithelium

Trachea, ductus deferens

Transitional Epithelium

Cells in transitional epithelium can change their shape to allow the bladder/ureters to stretch/expand. They fill and return to their original shape when empty, while also acting as a waterproof, protective barrier against the toxic wastes found in urine. - NO MODIFICATIONS

Location of Transitional Epithelium

Ureter, bladder, urethra

Cilia

small, dense, brush-like extra-cellular microtubules; used to move fluids

Microvilli

Small finger-like extensions of cell membrane, can't see clearly; increased surface area for absorption

Keratinization

Extracellular protein matrix; prevents desiccation &

resists abrasion

Goblet cells

Secrete (lots of) mucous

Stereocilia

Long extensions of the cell membrane; rare

Glandular Epithelia

Has cells that are specialized to produce secretions

Exocrine

Cells release their secretions into

passageways called ducts

Endocrine

Cells release their secretions into the

interstitial fluid (Secretions are called hormones)