Chapter 4 - Part 1 (epithelia and intro) Flashcards
1
Q
Epithelial tissue includes _____ and ______
A
epithelia and glands
1
Q
Epithelial tissue includes _____ and ______
A
epithelia and glands
2
Q
What is an epithelium?
A
an avascular layer of cells that forms a barrier and regulates permeability
3
Q
What are glands?
A
Structures that produce fluid secretions (either attached to or derived from epithelia)
4
Q
What kind of passageways does epithelia line?
A
All passageways that communicate with the outside world
5
Q
Give some examples of tracts that epithelia line
A
Digestive, urinary, reproductive
6
Q
Name 5 important characteristics of epithelial tissue
A
-cellularity
-polarity
-attachment
-avascularity
-regeneration
7
Q
Explain “cellularity”
A
epithelia are composed almost entirely of cells bound closely by junctions
8
Q
explain “polarity”
A
many structural and functional differences between the exposed (apical) and attached (basal) surfaces
9
Q
explain “attachment”
A
the base of an epithelium is bound to a basement membrane
10
Q
what is another name for the basement membrane
A
basal lamina
11
Q
explain “avascularity”
A
epithelia lack blood vessels
12
Q
how do epithelial cells obtain nutrients if they’re avascular?
A
by diffusion or absorption across either their exposed or attached surface
13
Q
explain “regeneration”
A
epithelial cells that are damaged or lost at the exposed surface are continuously replaced through STEM CELL DIVISIONS
14
Q
The rates of replacement are _____ in epithelial tissue than other tissues
A
HIGHER
15
Q
Name 4 FUNCTIONS of epithelial tissue
A
-Provide physical protection
-Provide sensation
-Control permeability
-Produce specialized secretions
16
Q
“control permeability”……. how can the epithelial barrier be modified in response to stimuli???
A
-hormones can affect the transport of ions and nutrients
-physical stress can alter the structure of epithelia (calluses on hand)
17
Q
“provide sensation”…….. what is the epithelium called that is specialized to perform sensory function?
A
neuroepithelium
18
Q
Epithelial cells that produce secretions are called..?
A
gland cells
19
Q
What is the name for the epithelium in which most or all of the epithelial cells produce secretions?
A
glandular epithelium
20
Q
Secretions can do 2 things:
A
-Be discharged to the surface of the epithelium
-Released into the surrounding interstitial fluid or blood
21
Q
When secretions are discharged to the surface of the epithelium, what is the purpose?
A
To provide physical protection or temperature regulation
22
Q
When secretions are released into surrounding interstitial fluid and blood, what is the purpose???
A
to act as chemical messengers
23
Q
Many epithelial cells that line internal passageways have _____on their exposed surfaces
A
microvilli
24
Microvilli are especially prominent along which 2 tracts? why?
digestive and urinary
absorption and secretion is prominent in these 2 tracts
25
The epithelial cells with microvilli have how many times more surface area than cells that lack it?
20 TIMES
26
The epithelial cell is divided into 2 functional regions:
-Apical surface
-Basolateral surface
27
How are substances moved over the epithelial surface?
By the synchronous beating of cilia
28
Which tract has cilia?
respiratory
29
A typical ciliated cell contains about ____ cilia
250
30
How can the cilia in the respiratory tract be damaged?
abrasion or exposure to toxic compounds (nicotine, carbon monoxide)
31
What are the 3 factors that help maintain the physical integrity of an epithelium?
1. Intercellular connections
2. Attachment to the basement membrane
3. Epithelial maintenance and repair
32
Epithelial cells are specialists in ______ connection
intercellular
33
Large areas of opposing plasma membranes are interconnected by __________proteins called _______
transmembrane proteins called CAMs (cell adhesion molecules)
34
What are cell junctions?
specialized areas of the plasma membrane that attach a cell to another cell or extracellular material
35
What are the 3 most common types of cell junctions
1. Tight junctions
2. Gap junctions
3. desmosomes
36
What is the lumen?
The space inside a tube (for example the intestinal tract)
37
What do tight junctions do in relation to the lumen?
tight junctions isolate the contents of the lumen from the basolateral surfaces of the cell
38
How are TIGHT junctions bound together?
the lipid portions of the plasma membrane interlock their membrane proteins
39
How are cells held together at GAP junctions
two interlocking transmembrane proteins called CONNEXONS
40
What kind of proteins are connexons? What does this allow them to do?
They're channel proteins which allows small molecules and ions to pass from cell to cell
41
In which other tissues are gap junctions common?
cardiac muscle and smooth muscle
42
Which junctions are very strong to resist stretching and twisting?
desmosomes?
43
Which junctions are very strong to resist stretching and twisting?
desmosomes
44
How are desmosomes connected?
CAMs and proteoglycans link the plasma membranes of adjacent cells
45
What connection gives the desmosome its remarkable strength?
a "dense area" connected to the cytoskeleton in each cell
46
What are the 2 kinds of desmosomes?
hemidesmosomes and spot desmosomes
47
Describe the structure and function of spot desmosomes
small discs connected to bands of intermediate filaments. Helps maintain shape of the cell
48
Describe the structure and function of hemidesmosomes
Resemble half of a spot desmosome. Attaches a cell to extracellular filaments in the base - NOT one cell to another. Helps stabilize position of the cell and anchor it to underlying tissues
49
The basement membrane has 2 parts. What are they?
clear layer and dense layer
50
What does the clear layer contain?
glycoproteins and fine protein filaments
51
Is the clear layer below or above the dense layer?
above
52
What is the function of the clear layer?
prevent the movement of proteins and large molecules from the connective tissue into the epithelium
53
What does the dense layer contain?
coarse protein fibers produced by the connective tissue cells
54
Which layer gives the basement membrane its strength - clear or dense layer?
dense layer
55
Which desmosomes attach epithelial cells to the basement membrane?
hemidesmosomes
56
Which layer of the basement membrane acts as a filter between adjacent cells and the epithelium?
dense layer
57
Adhesion belts are where in relation to tight junctions?
inferior to (below)
58
The only way the epithelium can maintain its structure over time is by..?
the division of stem cells
59
Where are most epithelial stem cells located?
near the basement membrane
60
What is another name for epithelial stem cells?
germinative cells
61
What is the probable function of an epithelial surface whose cells bear many microvilli?
absorption or secretion. microvilli increase the surface area available for absorption and secretion
62
What do gap junctions help to do?
the beating of cilia
the coordination of muscle contractions in cardiac and smooth muscle tissue
(allows small molecules and ions to pass from cell to cell)
63
What are the 2 categories in which we classify epithelia?
1. The cell shape
2. The number of cell layers between the basement membrane and the exposed surface of the epithelium
64
What are the 3 epithelial cell shapes?
squamous, cuboidal, columnar
65
What are the 2 options for the number of cell layers?
simple or stratified
66
Where are simple epithelium found in the body? why?
Because they are so thin and do not provide much protection, they are only found in protected areas of the body such as lining internal compartments and passageways such as ventral body cavities, heart chambers, and blood vessels
67
Simple epithelia are also found in regions where _____ or _____ take place. Why?
absorption or secretion because they are so thin so time is reduced for materials to cross the epithelial barrier. (intestines, lungs)
68
Where are stratified epithelium generally located?
in areas exposed to mechanical or chemical tress such as the surface of the skin and lining of the mouth
69
Describe the structure of squamous epithelium
thin, flat, and somewhat irregular in shape
70
What is the most delicate type of epithelium?
simple squamous
71
In general, where is simple squamous epithelium located?
protected areas where absorption or diffusion takes place
72
Name some specific places where simple squamous epithelium is found
alveoli, lining of the ventral body cavities, lining of the heart and blood vessels
73
Why are SMOOTH linings so important?
any irregularity in the lining of a blood vessel could form a clot
74
The simple squamous epithelium that lines the ventral body cavities is called....
mesothelium
75
The simple squamous epithelium lining the inner surface of the heart and blood vessels is called....
endothelium
76
Where are STRATIFIED squamous epithelium generally located?
Places of mechanical stress such as the surface of the skin and lining of the mouth, anus, esophagys
77
stratified squamous epithelia can be un______ or_______
UNKERATINIZED OR KERATINIZED
78
Where are KERATINIZED stratified squamous epithelia found?
EXPOSED body surfaces
79
Where are UNkeratinized stratified squamous epithelia found?
oral cavity, pharynx, esophagus, vagina
80
What is an important characteristic of unkeratinized stratified squamous epithelia??
will resist abrasion, but will dry out unless kept moist
81
Simple cuboidal epithelium provide....
limited protection and are found in places where secretion or absorption takes place
82
Stratified cuboidal epithelium are....
relatively rare. found in the ducts of sweat glands and mammary glands
83
Where is transitional epithelium found and why is it given that name?
the appearance of this epithelium changes when it's stretched, but returns to normal shape when recoiled.
found in the urinary bladder
84
unstretched, the transitional epithelium cells appear ______ but when stretched they appear______
unstretched - plump and cuboidal
stretched- appear stratified squamous
85
Simple columnar epithelium are generally found where?
places where absorption or secretion occurs. small/large intestine, stomach
86
what is the unique type of columnar epithelium?
pseudo stratified columnar epithelium
87
Why is pseudo stratified columnar epithelium given that name?
the distances between nuclei and exposed surfaces vary, so it appears to be stratified, but in reality all cells are attached to the basement membrane
88
pseudostratified columnar epithelium possess....
cilia
89
where in the body are pseudostratified epithelia found?
parts of male reproductive tract, bronchi, trachea, nasal cavity
90
What is the name for the glands that release secretions into the interstitial fluid?
endocrine glands
91
What is the name for the glands that release secretions into passageways (called ducts) that open onto an epithelial surface??
exocrine glands
92
What are endocrine glands secretions called?
hormones
93
What are 2 examples of endocrine glands?
Pituitary gland
Thyroid gland
94
Endocrine glands are also called?
ductless glands
95
Most exocrine glands release their secretions through....
tubular ducts
96
What are some examples of exocrine secretions?
tears from the eyes, perspiration on the skin, milk produced by mammary glands
97
How are exocrine glands classified?
Their mode of secretion
98
What are the 3 modes of secretion?
1. Merocrine
2. Apocrine
3. Holocrine
99
What is an example of a unicellular exocrine gland?
goblet cell
100
What happens in merocrine secretions?
Product is released by secretory vesicles in exocytosis
101
Which is the most common mode of secretion? (merocrine, apocrine, or holocrine)
merocrine
102
Which type of secretion forms mucus?
merocrine
103
Give 2 examples of merocrine glands in the body
sweat glands
salivary glands
104
What happens in apocrine secretion??
Involves the loss of the cytoplasm and secretory product. The apical portion is packed with the secretory product and then shed
105
What is an example of a mix of merocrine and apocrine gland in the body??
mammary gland
106
What happens in holocrine secretion?
The entire cell becomes packed with secretory product and bursts
107
Since holocrine secretion destroys the cell, how can further secretion take place?
the division of stem cells to produce new cells
108
What is an example of a holocrine gland in the body??
sebaceous glands - hair follicles that produce an oily hair coating
109
Besides modes of secretion, how else are exocrine glands classified?
Type of secretion produced
110
What are the 3 TYPES OF SECRETION PRODUCED?
-Mucous glands
-Serous glands
-Mixed exocrine glands
111
What do serous glands secrete?
Watery solution that contains enzymes
112
What do mucous glands secrete?
mucins that hydrate to form mucous
113
What do mixed exocrine glands secrete?
two different secretions: serous and mucous
114
Besides mode and type, how else are exocrine glands classified?
Gland structure
115
What are goblet cells and what do they secrete?
The ONLY unicellular exocrine glands in the body. Secrete mucins
116
What are the 3 characteristics used to describe the structure of multicellular exocrine glands
1. Structure of the duct
2. Shape of the secretory portion of the gland
3. Relationship between ducts and glandular areas
117
The skin has what kind of epithelium??
stratified squamous epithelium
118
Why can't the skin have simple squamous epithelium?
Not enough protection against infection, abrasion, and dehydration
119
Why do the pharynx, esophagus, anus, and vagina have a similar epithelial organization?
All are subject to mechanical trauma and abrasion
120
Name the 2 primary types of glandular epithelia.
endocrine and exocrine
121
sebaceous glands exhibit ______ secretion
holocrine
122
Which type of gland releases its secretions directly into the extracellular fluid?
endocrine
123
Transitional epithelium can either be ___ or ____
stretched or relaxed
124
When relaxed, what do the cells of transitional epithelium look like?
rounded - ciboidal appearance
125
When stretched, the cells of transitional look like..
squamous
126
Where are transitional epithelium found?
the urinary tract
127
The epidermis consists of _____ed _____ _____ cells
keratinized stratified squamous
