A&P1 CH4 Junctions & Epithelial Tissue

Tissue

Same type cells with same function

Organ

Greater than or equal to 2 tissues functioning together

System

Greater than or equal to 2 organs functioning together

Cell Junction: Tight

Impermeable barrier between adjacent cell membranes (zipper-like fastening) from proteins.

No extracellular space between cells

Found: stomach, intestine, bladder

Cell Junctions: Anchoring Junctions

Strong and flexible connections.

Found in skin + other areas.

Anchoring Junction: Desmosome

Plasma membranes from different cells are connected.

On inner cell membranes see plaque thickenings/patches with protein filaments of cadherin that extend between the cells and connect the plasma membranes.

Anchoring Junction: Hemidesmosome

Similar to Desmosomes but 1/2.

Uses protein integrin to anchor cell to extracellular matrix.

Anchoring Junction: Adherring

Connect cells together or to the extracellular matrix.

Use adherin and/or integrin proteins connected to actin filaments on inner surface of plasma membrane.

Shape & folding.

Gap Junction

Communication channel/hollow cylinder (connexon) or passageway between cells for exchange of small molecules/ions.

Found: heart and some muscle

Epithelial Tissue

Covering, lining, forming glands.

Covers body surfaces, organs, lines body inner cavities/hollow organs, lines and forms some glands/ducts.

2 Forms of Epithelial Tissue

1. Covering & Lining Form

2. Glandular Form

Covering and Lining Form

Outer skin, lines cavities of urogenital, digestive, and respiratory system, covers the walls and organs of the ventral cavity.

Glandular Form

Glands (they secrete)

Characteristics of Epithelial Tissue

Protects, secretes, absorbs, filters, excretes, and involved with sensing. (Except for glands, it forms sheets of closest packed cells, tight junctions)

No blood vessels (avascular) but has nerve supply (innervated).

May be modified with cilia and microvilli.

Arises from embryonic ectoderm, mesoderm, and endoderm.

Epithelial Tissue

Has polarity = one surface contacts open space = free surface = apical (top layer) surface and one surface connects to a basal lamina (bottom layer) of glycoprotein and collagen (filer and scaffold for repair) = basal surface

Epithelial Tissue: Reticular Lamina

Collagen rich connective tissue below basal lamina.

Epithelial Tissue: Basement Membrane

Two layers at the base of the tissue.

Both lamina together (basal and reticular)

Epithelial/Epithelium/Endothelium/Mesothelium

Covers/Lines, forms ducts, regenerates all the time, no blood vessels, nervous supply (innervated).

Epithelial Tissue: Organization

Named according to cell shape and number of layers:

Simple = 1 layer

Stratified = many layers

Pseudostratified = appears as many layers but it’s one layer of cells at different heights

Epithelial Tissue: Cell Shapes

Named according to cell shape:

Squamous = flat, scale-like, irregular sides

Cuboidal = boxlike

Columnar = column or pillar shaped

Always has layers!!

A) Simple Squamous Epithelial Tissue

Flat, irregular shaped cells.

Lines lung air sacs, kidneys, blood & lymphatic vessels, heart & forms capillaries = endothelium.

In serous membranes = mesothelium

For filtration and Exchange

B) Stratified Squamous Epithelial Tissue

For protection (strong waterproofing - eratine)

Epidermous

Keratinized, Stratified, Squamous, Epithelial Tissue

Two Types of Stratified Squamous Tissues

1. Keratinized

2. Nonkeratinized

Keratinized

Cells dehydrated, shrink and accumulate waterproofing keratin protein (outer layer of skin)

Pigmented skin

Nonkeratinized

Lines wet surfaces of nose, mouth, esophagus, vagina, anal canal

Vaginal cells

Cuboidal Epithelium

Round nucleus in the center of square shaped cell.

For secretion and absorption.

Two types of Cuboidal Epithelium

C) Simple: lines kidney tubules, ovary surface, and lines ducts.

D) Stratified: sweat and mammary glands.

E) Columnar Epithelium

Cells are taller than wide, nucleus near base (columns/pillars).

Absorption and secretion.

May have microvilli or cilia.

Columnar Epithelium: Goblet Cells

Tubular glands that secrete mucous and digestive substances.

Two Types of Columnar Epithelium

Simple: lines digestive tract & female reproductive tract.

Stratified: lines male urethra, pharynx, & forms glandular ducts.

Pseudostratified Ciliated Columnar Epithelium (Ciliated Pseudostratified)

Lines upper respiratory tract secretes and absorbs.

Cells at different heights, shape differs.

Goblet cells are present.

Transitional Epithelium

Can be stretched or distended.

Found in urinary system: bladder and ureters

Apical cells change shape with stretching, e.g. cuboidal to squamous

Secretion

One or more cells that make + secrete a particular product.

Epithelial Glands

Unicellular scattered throughout epithelial tissue. (NO ducts! Because the duct would be bigger than the gland!)

multicellular formed by invagination (goes deep) of epithelial tissue. (HAS ducts)

Two types: Endocrine & Exocrine

Endocrine Glands

One cell = NO ducts

Secretes hormones directly into extracellular or interstitial fluid that enters the blood stream (“internally secreting”), then taken to cells that respond to them.

Exocrine Glands

Multiple cells = HAS ducts

May secrete substance into ducts (salivary, mucous, sweat, mammary glands) onto epithelial tissue (“externally secreting”)

NEVER secretes hormones!

Characteristics of Endocrine Glands

Ductless, unicellular.

Produce hormones into extracellular space that enter blood/lymphatic tissue to target organs.

Secrete amino acids, peptides, glycoproteins, and steroids.

Characteristics of Exocrine Glands

Secrete onto body surfaces or into body cavities.

Secretions = saliva, mucous, sweat, milk, oil, bile, digestive products.

Characteristics of Exocrine Glands

Secrete onto body surfaces or into body cavities.

Secretions = saliva, mucous, sweat, milk, oil, bile, digestive products.

Exocrine Glands: multicellular

Has ducts and secretory unit (acinus).

Simple have I branched duct and compound have branched duct.

Makes the substance, then the duct transports it.

Exocrine Glands: multicellular Secretory Unit

Tubular form tubes.

Alveolar/Acinar form small, flask-like sacs.

Tubulialveolar have tubes and sacs.

Exocrine Gland Secretions: Multicellular

Merocine, Holocrine, Apocrine

Merocrine

Cells secrete product as produced = saliva and sweat glands.

Holocrine

Cells product until rupture = oil glands

Apocrine

Cells accumulate product and small area erupts at tip to release product (mammary glands).

Serous

More watery fluid

Mucous

More viscous fluid