Physiology Chapter 4 - Epithelial Tissues

Histology

The study of tissues

Tissue

A group of cells that are similar in structure (and therefore function)

Nervous Tissue

Brain, Spinal Cord, Nerves

\-Internal Communication

Muscle Tissue

Skeletal (Bones), Cardiac (Heart), Smooth (Walls of hollow organs)

\-Contracts to cause movement

Epithelial Tissue

Lining of GI tract and other hollow organs; epidermis (skin tissue)

\-Forms boundaries between different environments; protects, secretes, absorbs, filters

Hollow Organs

Organs that have a small or narrow cavity or lumen (aka hollow tube) inside them:

Esophagus, stomach, small intestine, gallbladder, fallopian tubes, and urinary bladder

Types of epithelial tissues (2)

1. Covering or lining epithelium: outer layer of the skin and walls and organs of closed body cavity
2. Glandular epithelium: glands of the body

Functions of epithelial tissues (6)

1. Protection (GI tract)
2. Absorption (lungs)
3. Filtration (kidneys)
4. Excretion (sweat glands)
5. Secretion (glands release hormones)
6. Sensory Reception (nerve endings embedded)

Epithelium Special Characteristics (5)

1. Polarity (differences in structure, composition and, function between 2 parts inside 1 cell)


2. Specialized Contacts (fit tightly together via tight junctions/desmosomes)
3. Supported by connective tissue on the basal/bottom surface
4. Avascular (no blood supply) but innervated (penetrated by nerve endings)
5. Regeneration (stem cells in the lower layers)

Apical Surfaces

Top/Free surface = Exposed to an internal body cavity

Basal Surfaces

Lower/Bottom surface = Attached to a thin basement membrane above connective tissue

Classification of epithelia (2)

1. Cell Shape
2. Cell Layering (strata)

\

Squamous

Cuboidal

Columnar

Glandular Epithelia

One or more cells that makes and secretes an aqueous fluid (secretion)

Endocrine

Internally secreting (hormones)

Exocrine

Externally secreting (sweat)

Unicellular

One cell forming the gland (goblet cells)

Multicellular

Multiple cells forming the gland (salivary)

\-Surrounded by supportive connective tissue that supplies blood and nerve fibers to the gland

Simple Duct Structure

Duct that does not branch

Compound Duct Structure

Duct that branches off

Tubular Secretory Structure

Shaped like a tube

Alveolar Secretory Structure

Shaped like a sphere

Merocrine

Secretes products by exocytosis (sweat)

Holocrine

Accumulates products within then ruptures (sebaceous oil glands aka pimples)

Apocrine

Accumulates products within, only ruptures out of the TOP/apex

What happens when you injure tissue? (3)

1. Inflammation Stage- Innate, non-specific response to tissue injury
2. Organization- Restores blood supply
3. Regeneration/Fibrosis- Proliferation of fibrotic connective tissue/Scar

Steps of Inflammation (2)

1. Increase capillary permeability (increases fluid leakage, seals off the wound, fluid accumulation/swelling + edema)
2. Clot formation (Stops bleeding + Prevents contamination)

Parts of Organization (5)

1. Granulation tissue formed
2. Capillaries form
3. Collagen fibers bridge gap
4. Macrophages phagocytize debris
5. Regeneration of epithelial cells

Parts of Fibrosis (3)

1. Regeneration - Epithelium + macrophages
2. Fibrosed area - Matures + contracts; epithelium thickens
3. Fully regenerated epithelium (Underlying area of scar aka fibrotic area)

Epithelial Membranes

Continuous multicellular sheet composed of at least 2 primary tissue types

Cutaneous Membrane

The skin/dry membrane; epidermis + dermis attached to each other

Epidermis

Keratinized stratified Squamous epithelium

Dermis

Thick layer of connective tissue

Mucous Membrane

Lines body cavities **open** to the exterior

\-Digestive, respiratory + urogenital organs

\-Wet/moist due to secretions or urine

\-Stratified squamous, simple columnar, or pseudostratified

Lamina Propria

Epithelial sheets that lie over loose connective tissue

Serous Membranes/ Serosae

Found in **closed** ventral body cavities (not open to the outside environment)

\-Moist

\-Enrich capillary fluid w/ hyaluronic acid (lubrication)

\-Allows layers to slide across each other

\-Simple squamous tissue on loose areolar connective tissue