Ch. 4 Part 2

Epithelial tissues

Epithelial Tissue

• Epithelial tissue or epithelium– Consists of cells arranged in continuous sheets in

either single or multiple layers– Cells are closely packed and held tightly together

by cell junctions– Have various surfaces• Apical (free)• Lateral• Basal

Epithelial Tissue

• Surfaces– Apical – faces body surface, body cavity,

lumen (interior space), or tubular duct– Lateral – face adjacent cells on all sides;

lateral surfaces contain junctions– Basal – opposite of apical; deepest layer of

cells; adhere to basement membrane; have hemidesmosomes

– Note: apical layer refers to most superficial basal layer refers to deepest layer

Basement Membrane

• Thin extracellular layer that consists of two layers: basal lamina and reticular lamina– Basal lamina (lamina = thin) – closer to epithelial cells

• Contains proteins: collagen, laminin, glycoproteins, proteoglycans

– Reticular lamina – closer to underlying connective tissue• Contains fibrous proteins (fibroblasts)

• Function: point of attachment and support for overlying epithelial tissue

Basement Membrane

Epithelial Tissue Types

• Based on 2 factors: layers and shape• Layers– Simple = single

• Function: diffusion, osmosis, filtration, secretion, absorption– Stratified = layer

• Function: protection from wear and tear– Pseudostratified (pseudo = false)

• Actually simple, but appear stratified because of nuclei arrangement

• Function: ciliated, secrete mucus

Epithelial Tissue Types• Shape

– Squamous• Arranged like floor tiles, thin• Function: rapid passage of substances

– Cuboidal• Shaped like cubes or hexagons• Function: secretion or absorption

– Columnar• Taller than wide, like columns• Function: protection, secretion or absorption

– Transitional• Change shape from flat to cuboidal• Function: stretch (urinary bladder)

Epithelial Tissue Types

• Combine layers with shape to get all epithelial tissue types (plus some extra)– Ciliated – have cilia

• Simple squamous, simple cuboidal, simple columnar, pseudostratified columnar

• Stratified squamous, stratified cuboidal, stratified columnar, transitional– Keratinized – contains keratin (protein)

Epithelial Tissue Types

• Red book p. 113 – 117• Blue book p. 100-105

Simple Squamous

Simple Cuboidal

Nonciliated Simple Columnar

Ciliated Simple Columnar

Pseudostratified Columnar

Stratified Squamous

Stratified Cuboidal

Stratified Columnar

Transitional

Checkpoint

• Describe the various layering arrangements and cell shapes of epithelium.

• What characteristics are common to all epithelial tissues?