Lecture 3: Basic cell types Flashcards
(144 cards)
1
Q
What are the four basic tissue types?
A
Epithelial tissue, supporting tissue, muscular tissue, nervous tissue
2
Q
What are epithelial tissues?
A
Diverse group of tissues including surface epithelia and solid organs
3
Q
What do epithelial tissues cover?
A
All body surface, cavities and tubes
4
Q
What are the functions of epithelial tissues?
A
Containment, selective diffusion/absorption, secretion and physical protection
5
Q
What do all epithelial tissues contain?
A
Cytokeratin intermediate filaments (makes them recognizable)
6
Q
What are all epithelia supported by?
A
Basement membrane of variable thickness
7
Q
What does the basement membrane separate the epithelium from?
A
Underlying supporting tissue
8
Q
What does the basement membrane not contain?
A
Blood vessels
9
Q
What is the consequence of basement membranes not containing blood vessels?
A
Epithelial cells are dependent on diffusion of nutrients and oxygen from connective tissue
10
Q
Because of the basement membrane, epithelial cells are ______
A
polarised
11
Q
What is the name of the side of the epithelial cells facing the basement membrane?
A
Basal surface
12
Q
What is the name of the side of the epithelial cells facing towards the surface (not the basement membrane)
A
Apical surface
13
Q
On what three properties are epithelial tissues classified?
A
No.cell layers, shape of cells, presence of surface specialisations
14
Q
What are the two types of epithelial tissues based on the number of cell layers?
A
Single layer: simple
Multilayered: stratified
15
Q
What are the three shapes of component cells of epithelial tissues?
A
Squamous (flattened), cuboidal columnar
16
Q
In stratified epithelia, the shape of which part of the tissues cells determine its name?
A
The surface shape
17
Q
Describe the shape of simple squamous epithelium
A
Flattened, irregular shaped cells, form a continous surface
18
Q
Simple squamous epithelium is often called…
A
Pavemented epithelium
19
Q
What supports simple squamous epithelium?
A
A delicate underlying basement membrane
20
Q
Where is simple squamous epithelium found?
A
Lining surfaces involved in diffusion of gases or fluids (lungs, blood capillaries etc.)
21
Q
How can simple squamous epithelium be recognized?
A
Nucleus bulges into the lumen
22
Q
How is simple cuboidal epithelial tissue recognised?
A
Nucleus is round and located in the centre of the cell
23
Q
Where is simple cuboidal epithelial tissue found?
A
Small ducts that are excretory, secretory or absoptive
24
Q
Give an example of where simple cuboidal epithelium is found in the body.
A
Collecting tubules of kidney
25
What do cell borders of simple cuboidal epithelium look like?
Indistinct
26
Where are nuclei located in simple columnar epithelium?
Base, apex or centre of cytoplasm: this is polarity of nucleus
27
Where are simple columnar epithelium found?
Absorptive surfaces (small intestine, gall bladder) or secretory (e.g. stomach)
28
Name another type of simple epithelia.
Psuedostratified columnar ciliated epithelium
29
Why is psuedostratified columnar ciliated epithelium classed as simple epithelia?
All cells rest on basement membrane, just nuclei are at different levels
30
Where is psuedostratified columnar ciliated epithelium found?
Airways: also known as respiratory epithelium
31
What do the cilia do in psuedostratified columnar ciliated epithelium tissue and what is this called?
Propel mucus to the pharynx
| Mucociliary escalator
32
What function does stratified epithelia have?
Mostly protective (too thick for absorption/secretion)
33
What are the shape of the cells at the top and bottom of stratified squamous epithelium?
Flattened at the top
| Cuboidal at the base
34
What is the epidermis made of?
Keratinising stratified squamous epithelium
35
How is the epidermis adapted to withstand constant abrasion/dessication?
Tough non-living surface layer composed of protein keratin wrapped in plasma membrane
36
What happens as the epithelium within the epidermis matures?
Nuclei are eventually lost
37
Describe the structure of stratified cuboidal epithelium
Thin, usually 2-3 layers of cuboidal cells only
38
Where is stratified cuboidal epithelium found?
Lining of larger excretory ducts of exocrine glands (salivary glands etc)
39
What is the strength of stratified cuboidal epithelium vs simple?
More robust
40
Is stratified cuboidal epithelium involved in significant secretory or absoptive activity?
No
41
What name is given to the epithelia found in the urinary tract of mammals?
Transitional epithelium (urothelium)
42
What is urothelium specialised for?
To accommodate stretch and the toxicity of urine
43
What types of epithelial cells does transitional epithelium have?
Intermediate between stratified cuboidal and squamous epithelia
44
When relaxed, what shape are the cells of the urothelium?
Large and rounded
45
When stretched, what shape are the cells of the urothelium?
Intermediate and surface layers are flattened
46
What are cilia?
Motile structures projecting from luminal surface of epithelial cells
47
Where are cilia most notably found? (As a specialisation of epithelia)
Female reproductive and respiratory tract
48
Cilia are not easily seen under a light microscope. True or false?
False
49
How do cilia move?
Wave-like synchronous rhythm to propell particles/fluid in a consistent direction
50
How long may cilia be?
10 micrometers
51
How many cilia may a cell have?
Up to 300
52
What are microvilli?
Minute, finger-like projections of the luminal plasma membrane
53
Where are microvilli found?
Epithelia specialised for absoption
54
How much can microvilli increase surface area by?
30 fold (may be thousands on one cell)
55
How long are microvilli?
1 micrometer
56
How do microvilli appear under a light microscope?
Cannot be resolved, but appear as a brush border
57
Where are microvilli found within the body?
Small intestine
58
What are goblet cells?
Modified columnar epithelial cells that synthesise and secrete mucus
59
Where are goblet cells found?
Scattered amongst simple epithelia, particualarly in the GI and respiratory tract
60
How do you stain goblet cells?
PAS staining: stains bright pink
61
What is epithelium primarily involved in secretion often arranged into?
stuctures called glands
62
What are glands?
Invaginations of the epithelial surface which proliferate into the underlying connective tissue
63
What do all glands have?
A continous basal rate of secretion which is modulated by nervous and hormonal influences
64
What comprises exocrine glands?
Solid organs of largely epithelial cells, connected to surface epithelium of GI tract by branching system of ducts
65
Give examples of exocrine glands
Small sweat glands
Salivary glands
Liver
66
What are exocrine glands divided into?
Secretory components and duct system
67
What are the types of secretory component?
Tubular or acinar
| Coiled or branched
68
What may the shape of the duct system be?
Branched (compound) or unbranched (simple)
69
Where are simple tubular glands found?
Large intestine
70
What type of gland are sweat glands?
Simple coiled tubular gland
71
What do simple coiled tubular glands appear as under a microscope?
Different portions seen in each plane of section because of tight coiled shape
72
Where is simple branched tubular glands found mostly?
In the stomach mucus
73
How are endocrine glands formed>
Lose their connection to epithelial surface during development
74
Where do endocrine glands release their secretions?
Directly into blood (and lymph??
75
Why are most endocrine glands composed of more than one type of secretory cell?
They release more than one hormone product
76
How is endocrine gland secretion usually controlled?
Metabolic factors (e.g. glucose)
Secretion of other hormones
Nervous system
77
Describe the general structure of most endocrine glands
Clusters of secretory cells, each with their own basement membrane, surrounded by blood vessel network
78
Of what origin is supporting tissue?
Mesodermal origin
79
What does supporting tissue do?
Provide structural and metabolic support for other tissues and organs
80
What does supporting tissue mediate?
Exchange of nutrients, gases and metabolites between tissues and the circulatory system
81
Name two forms of specialised supporting tissues
Blood, cartilage and bone
82
What are supporting tissue composed of?
- Specialised cells
| - Extracellular matrix
83
What is extracellular fluid?
Dominant component of many supporting tissues, which determines physical properties of the tissues
84
What is the extracellular matrix composed of?
Ground substance
| Fibres
85
In an H&E stain, what does fibrous proteins in the supporting tissues look like?
Wavy bundles of pink-stained material
86
In an H&E stain, what does ground substance appear as?
Pale, unstained
87
What is the overall appearance of an H&E stain of supporting tissue?
Generally, cell density is low.
88
What is the most abundant protein in the body?
Collagen
89
What does collagen provide?
Tensile strength
90
In what form is collagen secreted from a cell?
Secreted as tropocollagen
91
What happens to tropocollagen after it has been secreted into the extracellular matrix?
Polymerises into collagen
92
Where is type 1 collagen found?
Dermis, tendons, ligaments, bone and fibrous supporting tissue
93
In what form is type 1 collagen visible under light microscopes?
Bundles
94
Where is type 2 collagen found?
Hyaline cartilage
95
What is the appearance of type 2 collagen under a light microscope?
Fine fibrils dispersed in the ground substance
96
What is type 3 collagen also called?
Reticulin
97
What is the structure of type 3 collagen/reticulin?
Delicate branching supporting meshwork in highly cellular tissues
98
Where is type 3 collagen found?
Liver, bone marrow and lymphoid organs
99
How is type 3 collagen stained under a light microscope?
Absorb metallic silver, by which they are stained black
100
What does type 4 collagen do?
Forms a mesh-like structure in basement membranes
101
What is type 7 collagen?
Anchoring fibrils that link to the basement membrane
102
What cells are derived from mesenchyme?
Fibroblasts, myofibroblasts, chondrocytes, adipocytes, defence and immune cells
103
What are the most common cells?
Fibroblasts
104
What do fibroblasts do?
Responsible for secreting extracellular matrix
105
What is the function of myofibroblasts?
Contractile function and secretion of extracellular fluid
106
What cells are responsible for secreting the extracellular matrix in cartilage?
Chondrocytes
107
What cells are responsible for secreting the extracellular matrix in bone?
Osteocytes
108
What are adipocytes specialised for?
Storage and metabolism of fat, collectively form adipose tissue
109
What cells make up defence and immune cells?
Mast cells, tissue macrophages and plasma cells
110
What is the name given to the embryonic tissue from which all connective tissue is derived?
Primitive mesenchyme
111
What shape are mesenchymal cells?
Stellate shaped
| Delicate branching cytoplasmic extensions
112
What shape are the nuclei of mesenchymal cells?
Oval
113
Describe the extracellular matrix of mesenchyme cells
Mainly ground substance,very few fibres
114
How does mature fibroblasts collagen fibres appear in an H&E stain?
Dense and very pink
115
What is the shape of mature fibroblast nuclei?
Condensed and elongated in the direction of collagen bundles
116
What is the main function of mature fibroblasts?
Maintain integrity of the tissue by slow turnover of extracellular matrix
117
Where might supporting tissue be loose?
Bowel submucosa
118
What is the basement membrane made of?
Sheet like arrangements of extra-cellular matrix proteins
119
What is the basement membrane an interface between?
Support tissue and parenchymal cells
120
What name is given to the basement membrane in nerve and muscle tissue?
External lamina
121
What do basement membranes act as a barrier to?
Downward epithelial growth
122
Where is the selective permability of supporting tissue of particular importance?
Kidney
123
What are the main constituents of basement membranes?
Collagen type 4
| Structural glycoproteins laminin, entactin and fibronectin
124
What produces the main constituents of basement membranes (except fibronectin)
Epithelial cells
125
What produces fibronectin?
Fibroblasts
126
What three layers make up the basement membrane?
Lamina lucida, lamina densa and lamina fibroreticularis
127
What is the lamina lucida?
Transparent layer abuts the plasma membrane of the basal epithelial cells
128
What is the lamina densa?
Intermediate electron-dense layer
129
What is the lamina fibroreticularis?
Broad electrolucent layer which merges with supporting tissue underneath
130
What does lamina densa and lucida mainly consist of?
Type 4 collagen and laminin
131
What does lamina fibroreticularis mainly consist of?
Type 3 collagen and fibronectin
132
Adipose tissue generally has a rich blood supply. True or false? Why?
True
| For releasing energy
133
What might influence fat metabolism of adipocytes?
Hormones, nervous system, diet and energy expenditure
134
What proteins are adipocytes responsible for releasing?
Adipocytokines
135
Give an example of an adipocytokine.
Leptin, tumour necrosis factor alpha
136
What does adipocytokines do?
Regulate body mass and influence general metabolism
137
What % body weight does white adipose tissue make up in adults?
20% males
| 25% females
138
Where is white adipose tissue distributed?
Throughout the body, especially deep in the dermis
139
What other function does white adipose tissue have?
Thermal insulator and a cushion against mechanical shock (e.g. in kidney)
140
What receptors do adipocytes have?
Insulin, cortisol, growth hormone and noradrenaline
141
What shape does fat cells have?
Signet ring shape
142
What is brown adipose tissue?
Highly specialised type found in newborn mammals
143
What is the role of brown adipose tissue?
Temperature regulation
144
How is brown adipose tissue arranged?
Lobules separated by fibrous septae which convey blood vessels and nerves
