Epithelium

Question 1

Basic tissue types

Answer 1

Epithelium, Connective tissue, Muscle, Nerve

Question 2

How do you characterize epithelium?

Answer 2

Shape and number of layers

Question 3

Epithelium

Answer 3

closely aggregated polyhedral cells, strong adhesion, forms cellular sheets

Question 4

Connective tissue

Answer 4

cells produce an abundance of extracellular material (extracellular matrix), support nourishment, protection

Question 5

Muscle

Answer 5

Movement, contractility

Question 6

Nerve

Answer 6

transmission of impulses

Question 7

How to identify Epithelial tissues-Type

Answer 7

squamous/cuboidal/columnar/transitional, number of layers

Question 8

How to identify epithelial tissue- structure

Answer 8

Shape of cell and position of nucleus

Question 9

how to identify epithelial tissue: function

Answer 9

Covering/lining/protecting surfaces, absorption, secretion, proliferation, contractility (myoepithelial cells)

Question 10

How to identify epithelial tissues- location

Answer 10

Found throughout the body (covers body surface, lines organs and vessels)

Question 11

Characteristics of epithelial tissue

Answer 11

Forms cellular sheets, cells in close contact, produce very little intercellular substance- possess many junctional complexes (multicellular adhesion)

Secrete an ECM at base of cell, anchoring the epithelium to the underlying CT

Avascular (no blood or lymphatic supply)- nutrients and waste diffuse

Cell regions are polarized

Question 12

Epithelial tissue embryonic origin: Endoderm

Answer 12

gut, respiratory, urinary, bladder,pancreas, liver

Question 13

Epithelial tissue- ectoderm

Answer 13

skin/glands of skin

Question 14

Epithelial tissue- mesoderm

Answer 14

epithelial linings

Question 15

Simple

Answer 15

1 layer of cells

Question 16

Stratified

Answer 16

2 or more layers of cells

Question 17

Morphology of cells in surface layer

Answer 17

Squamous
Cuboidal
Columnar
Transitional

Question 18

Junctional compexes- Zona occludens

Answer 18

Tight junctions- forms a tight seal preventing a

seal between epithelial cells (transmembrane protein – claudin and occludin)

Question 19

Junctional complexes- zona Adherens

Answer 19

provides firm adhesion (“glue”) between cells
(linked by cadherins to catenin which is linked by actin-binding proteins to actin [*actin filaments form terminal web (possesses
contractile proteins that provide microvilli with contractile properties)]

Question 20

Junctional complexes- Macula Adherens (Desmosome)

Answer 20

provides firm adhesion (“spot weld”) between cells (extracellular side – cadherins, cytoplasmic side – various anchoring proteins in a dense plaque and intermediate filaments (e.g.cytokeratin, desmin or vimentin)

Question 21

Junctional complexes- Communicating Junction

Answer 21

provides rapid exchange of chemical and electrical signals allowing coordination of cellular activity (protein connexins form connexons (forms pores between cells)

Question 22

Tight junctions

Answer 22

Most apical portion of cell

Band completely encircles the cell

Fuses the outer leaflets of plasma membranes between adjacent cells - tight seal formed

Function is to prevent materials from entering the lateral border of cells

Question 23

Hemidesmosomes

Answer 23

Transmembrane proteins are integrins*

Function is to increase adhesion to basal lamina

Located on basal cell surface

Question 24

Basal lamina

Answer 24

Components secreted by epithelial cells
Specialized structure that cells rest on
Structure visible only at EM level
Lamina densa and/or lamina lucida (laminin and proteoglycan)

Question 25

Basement membrane

Answer 25

Thicker structure Basal lamina + reticular lamina Reticular lamina secreted by fibroblasts in underlying connective tissue Sometimes visible with light microscope

Question 26

Specialization of epithelial cells

Answer 26

Ion transport Pinocytosis Myoepithelial cells Absorption

Question 27

Epithelial glands

Answer 27

Collections of secretory cells specialized to synthesize and to secrete specific products Secretory molecules stored in the cell in membrane- bound vesicles called secretory granules Secretory product may be protein, lipid, or a combination Compound glands have: 1) a parenchyma (the gland and duct portion) 2) a stroma (the connective tissue components)

Question 28

Mechanism of secretion

Answer 28

HAM Holocrine- discharge of whole cells together with their secretory product (ex. sebaceous glands) Apocrine- release of secretory granules together with a small amount of attached cytoplasm (ex. mammary gland) Merocrine- secretory granules discharge their contents by fusion with plasma membrane (ex. sweat glands, pancreas)

Question 29

Morphology of ducts-Simple

Answer 29

Simple- unbranched ducts that may also be coiled

Question 30

Morphology of ducts: Compound

Answer 30

Compound- has a branching duct system

Question 31

Nature of secretion: Mucus secretion

Answer 31

Mucous secretion- Contain glycoproteins that become very hydrated and forms mucus (a viscous elastic, protective lubricating gel). Ex. Goblet cell

Question 32

Nature of secretion: Serous secretion

Answer 32

Serous secretion- Contain proteins in a watery secretion; Secretions contained in secretory granules in apical portion of the cell. Ex. Pancreas, Parotid gland

Question 33

Nature of secretion: Mixed (seromucous)

Answer 33

Mixed (seromucous)- Some glands contain both types of cells. Ex. submandibular gland