ch5 epithelial Tissues

Epithelial tissue

Covers body surfaces

Little to no EC matrix

Lines body cavities + organs

Forms glands

epithelial tissue characteristics

Cellularity - tightly packed cells, minimal space b/w

Regenerative - barrier quickly restored when damaged

Avascularity - pathogens separated from blood

Attached -  basement membrane, stable barrier over underlying tissues

Polar - Apical surface: Exposed to external environment.

Basal surface: Anchored to underlying connective tissue.

epithelial functions

physical protection (resist dehydration, abrasion, destruction)

selective permeability (kidneys)

absorption (SI)

secretion (goblet cells)

sensation

Tight junctions

bands of fused membranes, encircle entire cell, near surface

seal space b/w adjacent cells, selective permeability

block liquids, ions, and pathogens from passing between them

Adherens junctions

deep to TJ, encircle entire cell

structural stability - anchoring cell membranes to internal microfilament networks

Desmosomes

Act like spot welds or rivets to anchor neighboring cells together, preventing the tissue from tearing under mechanical stress

gap junctions

small pores allows smalll molec pass

comprised of connexons

Simple epithelium

single layer cells attached to basement membrane.

absorption, secretion, filtration because substances can easily pass across a thin single layer

alveoli of lungs (rapid gas exchange), capillaries (nutrient exchange), small intestine (nutrient absorption)

Stratified Epithelium

two or more stacked layers of cells.

protection against physical wear, chemical abrasion, and infection

skin, mouth, and esophagus

Simple Squamous epithelium

Single layer of flat, irregular cells

diffusion, filtration, secretion

(air sacs of lungs, endothelium)

squamous cell

Nucleus squamous cell

Simple Cuboidal epithelium

Single layer of cube cells

absorb, secretion

kidney tubules, glands,

Simple Cuboidal epithelium

Cuboidal epithelial cell

Cuboidal epithelial cell

nucleus Cuboidal epithelial cell

nucleus Cuboidal epithelial cell

lumen collecting duct (kidney)

receives tubular fluid

nonciliated Simple Columnar epithelium

Single layer of tall cells

absorption, secretion

digestive tract

nonciliated Columnar epithelium nucleus

nonciliated Columnar epithelium cell

microvilli (brush border)

increase cell surface area

transport/absorb

SI, kidney

jejunum lumen

receives secretions from goblet cell, partially digested material from duodenum

basement membrane Simple Columnar epithelium

b/w epithelium and underlying connective tissue

basal and reticular lamina

anchors epithelium, physical support, molecular filter

Goblet cell nonciliated Simple Columnar epithelium

jejunum

• Secretes protective mucus into lumen jejunum

hypertonic

water moves out - SHRINK

hypotonic

water into cell - SWELL

Pseudostratified columnar epithelium (ciliated)

respiratory/urinary tract, lines glands

single layer cells, only some reach apical

protection + secretion

Basal cell nucleus (pseudostratified columnar epithelial cell)

trachea lumen

conducts air to and from lungs

Goblet cell (pseudostratified columnar epithelium)

columnar epithelial cell

TALL

Cilia (pseudostratified columnar epithelium)

sweep mucus and trapped particles away

Stratified squamous epithelium (keratinized)

skin epidermis

apical cells NO nuclei

protects underlying tissue

squamous cell w/o nucleus

epidermis

avascular

Stratified squamous epithelium (nonkeratinized)

oral cavity, esophagus, reproductive/urinary

apical cells HAVE nuclei

protects underlying tissue

squamous cell with nucleus

squamous cell nucleus

Transitional epithelium

multiple layer cells

relaxed = apical cells dome shape/cuboidal

distention = flat/squamous

lining urinary

loose connective tissue

more ground substance and fewer cells and protein fibers than dense connective tissue

subcue tissue, around organs

• Support epithelia

• Protects organs

• Surrounds blood + lymphatic vessels + nerves

•  environment diffusion materials ( gases, electrolytes, nutrients, and cellular waste products)

Dome-shaped luminal cells transitional epithelium

epithelial tissue: ___ relationship Permeability vs. Protection

Inverse

maximize mechanical or chemical protection restrict the movement of molecules

rapid diffusion or nutrient absorption leave the tissue physically vulnerable

Exocrine Glands

Retain a duct

Secretes products onto an internal or external body surface

Sweat glands

Endocrine Glands

Ductless glands

Produce and release hormones directly into the interstitial fluid and bloodstream

Thyroid gland