The tissue level of organization - Epithelia tissue Flashcards

1
Q

Define tissues

A

Collections of specialized cells and cell products that perform specific functions

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2
Q

What is histology

A

is the study of tissues

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3
Q

What are the four types of tissue

A
  1. Epithelial
  2. Connective
  3. Muscle
  4. Nervous
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4
Q

Describe epithelial tissue

A

– Covers exposed surfaces
– Lines internal passageways
– Forms glands

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5
Q

Describe the connective tissue

A

Fills internal spaces
– Supports other tissues
– Transports materials
– Stores energy

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6
Q

Describe the muscle tissue

A

Specialized for contraction
– Skeletal muscle, heart muscle, and muscular walls of hollow organs

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7
Q

Describe the nervous tissue

A

– Carries electrical signals from one part of the body to another

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8
Q

Epithelial tissue includes

A

– Epithelia (singular, epithelium)
* Layers of cells covering internal or external surfaces
– Glands
* Structures that produce fluid secretions

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9
Q

What is the function of the epithelial tissue

A
  1. Provide physical protection
  2. Control permeability
  3. Provide sensation
  4. Produce specialized secretions
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10
Q

States some characteristics of epithelia

A

– Polarity (apical and basal surfaces)
– Cellularity (cell junctions)
– Attachment (basement membrane)
– Avascularity (avascular)
– Regeneration

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11
Q

Describe the specializations of epithelial cells

A
  1. Move fluids over the epithelium (protection)
  2. Move fluids through the epithelium (permeability)
  3. Produce secretions (protection and messaging)
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12
Q

Explain polarity

A

4-2 Epithelial Tissue
▪ Specializations of epithelial cells
1. Move fluids over the epithelium (protection)
2. Move fluids through the epithelium (permeability)
3. Produce secretions (protection and messaging)
▪ Polarity
– Apical surface
* Microvilli increase absorption or secretion
* Cilia on a ciliated epithelium move fluids
– Basolateral surface

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13
Q

Identify the structures of the epithelia

A
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14
Q

How is the integrity of the epithelia maintaned

A
  1. Intercellular connections
  2. Attachment to the basement membrane
  3. Epithelial maintenance and repair
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15
Q

What is the purpose for intercellular connections

A

– Support and communication
* Cell adhesion molecules (CAMs)
– Transmembrane proteins
* Proteoglycans act as intercellular cement
– Contain glycosaminoglycans such as hyaluronan (hyaluronic acid)

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16
Q

What is cell junctions

A

Form bonds with other cells or extracellular material

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17
Q

What are the types of cell junctions

A
  1. Gap junctions
  2. Tight junctions
  3. Desmosomes
18
Q

Describe gap junctions

A

– Allow rapid communication
– Cells held together by interlocking transmembrane
proteins (connexons)
– Allow small molecules and ions to pass
– Coordinate contractions in heart muscle

19
Q

Describe the tight junctions

A

– Between two plasma membranes
– Adhesion belt attaches to terminal web
– Prevent passage of water and solutes
– Keep enzymes, acids, and wastes in the lumen of the digestive tract

20
Q

Describe desmosomes

A

– CAMs and proteoglycans link opposing plasma
membranes
– Spot desmosomes
* Tie cells together
* Allow bending and twisting
– Hemidesmosomes
* Attach cells to the basement membrane

21
Q

Identify the cell junctions on the cell

22
Q

What is attached to the basement membrane

A

– Basal lamina
* Closest to the epithelium
– Reticular lamina
* Deeper portion of basement membrane
* Provides strength

23
Q

Explain the epithelial maintenance and repair

A

– Epithelial cells are replaced by continual division of
stem cells
* Located near basement membrane

24
Q

Explain the classification of epithelia

A
  1. Based on shape
    * Squamous—thin and flat
    * Cuboidal—square shaped
    * Columnar—tall, slender rectangles
  2. Based on layers
    * Simple epithelium—single layer of cells
    * Stratified epithelium—several layers of cells
25
Describe the simple squamous epithelia
– Simple squamous epithelia * Absorption and diffusion * Mesothelium – Lines body cavities * Endothelium – Forms inner lining of heart and blood vessels
26
Explain the function of Stratified squamous epithelia
* Protect against mechanical stresses * Keratin adds strength and water resistance
27
Describe simple cuboidal epithelia
* Secretion and absorption * Glands and portions of kidney tubules
28
Describe stratified cuboidal epithelia
* Relatively rare * Ducts of sweat glands and mammary glands
29
Describe the transitional Epithelia
– Tolerate repeated cycles of stretching without damage – Appearance changes as stretching occurs – Found in the urinary bladder
30
Describe simple columnar epithelia
* Absorption and secretion * Found in stomach, small intestine, large intestine
31
Describe pseudostratified columnar epithelia?
* Typically have cilia * Found in nasal cavity, trachea, bronchi
32
Describe stratified columnar epithelia
* Relatively rare * Provide protection in pharynx, anus, urethra
33
Define Gland
Glands are collections of epithelial cells that produce secretions
34
What are the two types of glands and describe
– Endocrine glands * Release hormones that enter bloodstream * No ducts – Exocrine glands * Produce exocrine secretions * Discharge secretions through ducts onto epithelial surfaces
35
Gland structure has
– Unicellular glands – Multicellular glands
36
Describe the unicellular glands
– Goblet cells are unicellular exocrine glands * In epithelia of intestines * Secrete mucin, which mixes with water to form mucus
37
Describe the multicellular glands
are classified by 1. Structure of the duct * Simple (undivided) * Compound (divided) 2. Shape of secretory portion of the gland * Tubular (tube shaped) * Alveolar or acinar (blind pockets) 3. Relationship between ducts and glandular areas * Branched (several secretory areas sharing one duct)
38
State the three methods of secretion
1. Merocrine 2. Apocrine 3. Holocrine
39
Describe Merocrine secretion
Released by secretory vesicles (exocytosis) – Example: merocrine sweat glands
40
Describe Apocrine secretion
– Released by shedding cytoplasm – Example: mammary glands
41
Describe Holocrine secretion
– Released by cells bursting, killing gland cells – Gland cells replaced by stem cells – Example: sebaceous glands
42
What types of secretions are produced by exocrine glands
– Serous glands * Watery secretions – Mucous glands * Secrete mucins – Mixed exocrine glands * Both serous and mucous