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Flashcards in Epithelium And Glands Deck (33):
1

Epithelium

- sheets of cells covering a surface of lining a cavity
- responsible for the major function of most organs

2

Connective Tissue

-cells and ECM that support and connect other basic tissue types in organs
-include bone and cartilage and blood

3

Muscle

-contractile tissues

4

Nervous Tissue

-conductive tissues that distribute signals that control various body functions

5

Characteristics of Epithelial

-continuous sheets
- rest on basement membrane
- junctions
-polarized
-Surface modifications
- Avascular - no blood vessels in the actual epithelium

6

Epithelium Functions

- barrier
- absorption and secretion
- removal of particulate matter
- gas exchange
- filtration

7

Surface Modifications

-apical surface:
1) Microvilli - actin cytoskeleton, increase absorptive surface area, found in GI tract there they promote uptake of nutrients
2) Stereocilia - very long Microvilli, actin cytoskeleton, increase absorptive SA, found I epididymis where they promote concentration of sperm, not motile
3) cilia - microtubule cytoskeleton, motile surface extension that move luminal contents, in respiratory tract move particulate matter out of lungs, in female reproductive tract assist in movement of gametes

8

Microvilli

- increase apical surface area for absorption and secretion
- actin core provides support to the plasma membrane
- anchored by terminal web

9

Cilia

-motile
- found in locations where movement serves function
- respiratory epithelium - cilia keep airway free of particulate matter

10

Basal Surface Specializations

- basal unfolding of the plasma membrane
- associated with mitochondria
-high level of transport activity
- find in proximal convoluted tubule in the kidney and striated ducts of salivary glands

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Classification of Epithelial

- based on shape of cells and number of cellular layers

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Squamous

- thin, flattened appearance

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Cuboidal

-height and width are similar

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Columnar

-height greater than width

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Simple

-single layer

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Stratified

-multiple layers

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Pseudostratified

-appears stratified, but all cells touch basement membrane, some do not reach apical surface

18

Transitional

-transitional appearance between stratified columnar and stratified squamous and depends on physiological state

19

Simple Squamous

-mesothelium found lining the external surface of internal organs
- secrets fluid that reduces friction between organs
- Endothelium found lining the internal surfaces of the heart and blood vessels
- facilitates transport of fluids, nutrients, metabolites, and gas exchange between flood and surrounding tissues

20

Simple Cuboidal

- lining of ducts of glands, kidney tubules, thyroid follicles
- taller cells provide additional support
- cells can be active in transport, synthesis and secretion of substances
- Height can depend on activity of the cell and range from low to almost columnar

21

Simple columnar

- found lining the digestive tract and uterine tube
- can have more than one type with different functions
- absorptive
-secretory (mucus)

22

Stratified Epithelium

- multiple layers of cells, number of layers varies
- basal layer rests o basement membrane, upper layers rest on cells below not on the basement membrane
-uppermost layer at the free surface
-take their name from the uppermost layer, can be squamous, cuboidal or columnar
-basal layer can be one type and the upper layer a different type
- cells in the basal layer may divide to maintain the integrity of the epithelium as upper layers are lost

23

Stratified squamous

- thick and thin skin, non-keratinizing wet skin (mouth)

24

Stratified cuboidal

-glandular ducts and large salivary excretory duct

25

Stratified Squamos Epithelium

- 2 types: non-keratinizing, keratinizing
- provides barrier and protection against abrasion
- Non-keratinizing is found in moist areas that are subject to abrasion such as oral cavity, esophagus, vagina and anal canal
- keratinizing is found in skin where upper layers lose their nuclei and contain large amounts of keratin

26

Pseudostratified Epithelium

-may appear stratified
- nuclei are at different heights making epithelium appear stratified
-however all cells touch the basement membrane
- some cells are not as tall as others and the apical surface of the cell may not reach the top of the epithelium
- found in respiratory tract and epididymis

27

Transitional Epithelium

-found exclusively in the bladder and adjacent regions of the urinary system
- changes shape depending on the extension of the bladder
- Relaxed: multiple layers, surface layer has rounded dome cells that are often binucleate
- Extended - multiple layers, but doesn't appear as many as relaxed state

28

Glands

-invaginations of sheets of epithelium that grow downward into the underlying connective tissue
- Exocrine: glands that maintain their connection to the surface, secretory products released into the duct and travel to the surface (sweat glands)
- Endocrine: glands that lose their connection to the surface, surrounded by capillaries where secretory products enter the blood (adrenal, thyroid)

29

Exocrine

- unicellular, single cell type (goblet cells in intestines)
- multicellular (most common), Ductal portion, secretory portion
- Classification:
1) Structure of the duct (simple or compound)
2) shape of secretory units ( tubular or actin acinar/alveolar)
3) Type of secretion (serous, mucous or mixed)
4) Mechanism of secretion (apocrine, merocrine, holocrine)

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Duct Shape

1) Single duct - simple gland
2) Branched duct - compound gland

31

Secretory unit shape

- tubular gland
- acinar gland is sphere-like in shape

32

Large exocrine gland anatomy: Connective tissue divides gland into lobes and lobules

- Parenchyma - functional component of organ
- Stroma - supportive CT component of organ
- Hillum: Doorway for ducts, nerves, and blood and lymph vessels to go to/from gland. These structures course through the CT of trabeculae (septa) to reach parenchyma

33

Mechanisms of secretion

-Apocrine secretion: loss of cytoplasm and apical cell membrane, occurs in mammary gland
-Merocrine secretion: exocytosis of secretory vesicles, occurs in typical glands (salivary)
-Holocrine secretion: entire cell is shed and cell breaks down releasing its substance stored in vesicles, occurs in sebaceous glands