histo lab 2

epithelial tissue

• Interface tissue that forms boundaries

between environments and lines

surfaces

• Composed of aggregated polyhedral

cells with strong adhesion to one another

• Forms cellular sheets lining the cavities

of organs and covers surfaces

Functions pf epithelial tissue

• Covering, lining and protection of

surfaces

• Absorption

• Secretion

1. Covering epithelia

• Covers the surface or lines

cavities of an organ

• Arranged by layers

• Simple (1 cell layer)

• Stratified (2 or more layers)

• Characteristic shapes

• Squamous

• Cuboidal

• Columnar

• Some epithelia are keratinized

(contains keratin filaments)

• Epidermis of the skin

2. Secretory epithelia

• Formed by cells that facilitate

production and secretion of

molecules

• Proteins, lipids, carbohydrates, water

• Contains glands

• Develops during the fetal stage via

cell proliferation and growth

• From covering epithelia into the

underlying connective tissue

• Exocrine (connected to epithelium,

contains ducts)

• Endocrine (not connected, no ducts,

attached to capillaries)

1. SIMPLE SQUAMOUS EPITHELIUM

• Single layer of flat hexagonal cells

• Functions for diffusion, filtration,

secretion, and protection

• Found in the alveoli of lungs,

Bowman's capsule, lining of blood

vessels, lymph vessels

2. STRATIFIED SQUAMOUS EPITHELIUM

• Found on epidermis of skin

packed with keratin filaments

(keratinized)

• Found on moist internal cavities

like the mouth, esophagus, and

vagina with sparse keratin (non-

keratinized)

3. SIMPLE CUBOIDAL EPITHELIUM

• Single layer of cube-shaped cells

• May contain microvilli or cilia

• Functions for absorption and

secretion

• Found on kidney tubules, terminal

bronchioles of lungs, choroid

plexuses

4. STRATIFIED CUBOIDAL EPITHELIUM

• Multiple layers of cube-like

shaped cells

• Found on sweat gland ducts,

salivary gland ducts, ovarian

follicular cells(?)

5. SIMPLE COLUMNAR EPITHELIA

• Single layer of tall, narrow cells

• Some cells contain cilia

• Functions for movement of

particles, absorption, secretion

by cells on glands

• Found on bronchioles of the

lungs, auditory tubes, stomach

intestines, bile ducts, uterus

6. STRATIFIED COLUMNAR EPITHELIUM

• Multiple layers of tall narrow

cells

• Has both protective and

secretion functions

• Found on conjunctiva of

eyes, pharynx, anus, urethra

in males

7. PSEUDOSTRATIFIED COLUMNAR

EPITHELIUM

• Single layer of cells present, mostly

ciliated

• Cell nuclei are at different levels

showing a "stratified" appearance

• Functions for movement of fluid or

mucus and synthesis and secretion

of mucus

• Found in lining of nasal cavity,

pharynx, trachea, bronchi of lungs

8. TRANSITIONAL EPITHELIUM

• Stratified cells that appear

cube-shaped when organ is not

stretched; squamous when

organ is stretched

• Functions to accommodate

fluctuations in fluid volume

within an organ

• Located in the urinary bladder,

ureter, urethra, uterus

1. Microvilli

• Cytoplasmic projections, functions for

absorption

• Brush border of intestinal tract

2. Stereocilia

• Absorption functions (male reproductive

system)

• Motion-detecting functions (ear sensory

cells)

Cilia

• Motility and movement

Atrophy

• decrease in cell size and organ

Hypertrophy

• increase in cell size and organ

Hyperplasia

• increase in number of cells

Metaplasia

• mature differentiated adult cell type is replaced

with another differentiated adult cell type

Dysplasia

• deranged cell growth with alteration in size, shape,

and orientation with the loss of differentiation

GLANDS

• Organs composed of secretory cells

• Produces and secretes various macromolecules

• Develops from in folding or out folding of epithelium in the

embryo

Exocrine-

gland remains connected with surface epithelium

and uses tubular ducts to deliver secreted material

Endocrine-

gland that has lost original connection to

epithelium; ductless; specialized for protein or hormone

synthesis; secretions are transported directly into blood through

capillaries

Merocrine

• Typical exocytosis from

membrane bound vesicles or

secretory granules

Apocrine

• Secreted product accumulates

at cell's apical ends

• Extrusion to release secreted

product with small amount of

cytoplasm and cell membrane

Holocrine

• Cell accumulates product as

they enlarge

• Cell ruptures to release product

along with cell debris