Epithelia and supporting tissue lecture - week 2 Flashcards
(107 cards)
1
Q
What are the four basic tissues?
A
- epithelial tissue
- supporting tissue
- msucular tissue
- nervous tissue
2
Q
Define epithelial tissues
A
- diverse group of tissues including surface epithelia and solid organs
3
Q
Where can epithelial tissues be found?
A
surface epithelia cover and line all body surface, cavities and tubes - interface between different compartments
4
Q
What processes are epithelial tissues involved in?
A
containment, selective diffusion, absorption, secretion, physical protection
5
Q
What do all epithelial tissues contain?
A
cytokeratin intermediate filaments - makes them recognisable on immumohistochemistry
6
Q
What supports all epithelia cells?
A
by a basement membrane of variable thickness
7
Q
What does the basement membrane do?
A
- separates the epithelium form the underlying supporting tissue
- does not contain blood vessels so epithelium is dependent on diffusion of nutrients and oxygen from connective tissue for survival
8
Q
Are epithelial cells polarised?
A
yes
9
Q
How are epithelial cells polarised?
A
with one side facing the basement membrane (basal surface) and one towards the surface (apical surface)
10
Q
How are surface epithelial cells classified?
A
- according to number of cell layers
- shape of the component cells
- presence of surface specialisations
11
Q
What is a simple epithelial cell?
A
single layered
12
Q
What is a multilayered epithelial cell?
A
stratified
13
Q
Name different shapes an epithelial cell can have
A
squamous - flattened
cuboidal or columnar
14
Q
Name 4 types of simple epithelial
A
- simple squamous epithelium
- simple cuboidal
- simple columnar
- pseudo stratified columnar ciliated epithelium
15
Q
What is the structure of a simple squamous epithelium?
A
flattened irregular shaped cells forming a continuous surface surface - pavemented epithelium
16
Q
What is the BM of a simple epithelia?
A
delicate underlying basement membrane
17
Q
Name examples for when simple epithelia is used
A
lining surfaces involved in diffusion of gases eg. lungs or fluids eg. blood capillaries
18
Q
How do simple epithelia look like?
A
cells are so flat they can only be recognised by nucleus which bulges into lumen
19
Q
What is the simple cuboidal epithelia?
A
the intermediate between simple squamous and simple columnar
20
Q
What about the nucleus of simple cuboidal epithelia cells?
A
nucleus Is round and located in the centre of the cell
21
Q
Where can simple cuboidal cells be found?
A
lines small ducts and may have excretory, secretory or absorptive functions eg. collecting tubules of kidney
22
Q
How can you identify a simple cuboidal epithelial cell ?
A
cell border may be distinct, nuclei give away - very big
23
Q
What are simple columnar epithelial cells like compared to the others?
A
like simple cuboidal but cells are taller
24
Q
Where is the nuclei located in the cell of the simple columnar epithelial cell?
A
nuclei elongated, may be located towards base, apex or centre of the cytoplasm - this is the polarity of the nucleus
25
Where are simple columnar epithelial cells found?
on absorptive surfaces eg. small intestine, gall bladder (absorbs water) or play a secretory role eg. stomach
26
What do simple columnar epithelial cells look like?
long rectangles, nucleus all towards one side of the cell
27
What is a pseudo stratified columnar ciliated epithelium ?
- true simple epithelium because all cells rest on basement membrane, but nuclei are all at different levels giving the appearance of different cell layers
28
Where are pseudo stratified columnar collated epithelium cells found?
confined to airways so known as respiratory epithelium: cilia propel mucous to pharynx = muscociliary escalator
29
What is the main function of stratified epithelia?
mainly a protective function
30
Why are stratified epithelia cells poorly sited for absorption and secretion?
due to thickness of all the cell layers
31
Name two kinds of stratified epithelia cells
- stratified squamous epithelium
- transitional epithelium (urethelium)
32
Where are transitional epithelium (urethelium) found?
only in the urinary tract in mammals
33
What is the function of transitional epithelium (urethelium)?
highly specialised to accommodate stretch and toxicity of urine
34
Where is the transitional epithelium located?
intermediate between stratified cuboidal and squamous epithelia
35
How do transitional epithelium cells look like?
- relaxed: surface cells are large and round
- stretched: intermediate and surface layers are extremely flattened
36
Name two types of membrane specialisations of epithelia?
cilia, microvilli, goblet cells
37
What are cilia?
motile structures that protect forms he luminal surface of the epithelial cells,
38
Where are cilia found?
notably int eh female reproductive and respiratory tract
39
are cilia seen under a light microscope?
yes, easily
40
How do cilia move?
beat with a wave-like synchronous rhythm propelling particles / fluid in a consistent direction over the epithelia surface
41
How long can cilia be ?
10 micrometers long
42
How many cilia might be on a cell?
300 cilia
43
What are microvilli?
minute finger-like projections of the luminal plasma membrane found in epithelia that are specialised for absorption
44
How many microvilli are on one cell, what do they do ?
may b thousands on one cell, increase surface area by x30 fold
45
How long is a microvilli ?
only 1 micrometre in length
46
Can microvilli be seen under a light microscope?
no, cannot - appearing as a brush border
47
where are microvilli found?
in the small intestine
48
What are goblet cells?
modified columnar epithelial cells that synthesis and secrete mucus
49
Where can goblet cells be found?
scattered amongst many simple epithelia, particularly in the GI and respiratory tract
50
How do goblet cells look stained?
stains bright prink with PAS staining
51
What is the glandular epithelium?
epithelium primarily involved in secretion is often arranged into structures called glands
52
What are glands?
invaginations of epithelial surface which proliferate into the underlying connective tissue
53
What do all glands have in common and how is this modulated?
- a continuous basal rate of secretion, modulated by nervous and hormonal influences
54
What is an exocrine gland?
comprise solid organs of largely epithelial cells, connected to surface epithelium of GI tract by branching system of ducts ie. vary from small sweat glands to salivary glands to liver
55
What are exocrine glands divided into?
different secretory components
- tubular or acing
- coiled or branched
their duct system
- branched (compound) or unbranched (simple)
56
name three types of exocrine glands
- simple tubular glands
- simple coiled tubular glands
- simple branched tubular glands
57
Where can simple tubular glands be found?
large intesine
58
How do simple tubular glands look like?
single straight tubular lumen into which the secretory products are discharged
59
what lines the entire duct of simple tubular glands?
secretory cells
60
what is an example of a simple coiled tubular gland?
the sweat gland
61
what do simple coiled tubular glands look like?
- tightly coiled in 3D, different portions seen in each plane of section
62
Where are simple branched tubular glands found?
mainly in the stomach mucus - secreting glands
63
How do simple branched tubular glands look like?
several tubular secretor portions which converge onto a single unbranched duct
64
How do endocrine glands release secretions?
- lost connection to epithelial surface during development
- reseals secretion directly into blood eg. thyroid gland
65
Why are most endocrine glands composed of more than one type of secretory cell?
because they release more than one hormone product
66
What controls the secretion of endocrine glands?
generally controlled by metabolic factors eg. glucose, the secretion of the hormones and/or the nervous system
67
What do most endocrine glands contain?
- clusters of secretory cells, each with their own basement membrane, surrounded by a rich network of blood vessels
68
What do endocrine glands do?
release hormones into the intercellular spaces, form whence they diffuse rapidly into the blood
69
What is supporting tissue?
tissue of mesodermal origin - provides structural and metabolic support for other tissues and organs
70
What is the function of the supporting tissue?
mediates exchange of nutrients, gases and metabolites between tissue and circulatory system
71
What does supportive tissue generally contain?
blood and lymphatic vessels
72
what are specialised supportive tissues?
- blood, cartilage and bone tissues
73
What is supporting tissue composed of?
- specialised cells
- extracellular matrix
74
What is the extracellular matrix?
- dominant component of many sporting tissues,
- comprised of ground substances and fibres
- determines physical properties of tissue
75
What is the main type of fibre in supporting tissues?
collagen
76
What is collagen and what is it's function?
- mot abundant protein in the body
- provides tensile strength
77
How is collagen formed?
secreted as tropocollagen which polymerises in the extracellular matrix to form collagen
78
Name five common types of collagen
type 1,2,3,4,7
79
Where is type 1 collagen found?
in dermis, tendons, ligaments, bone and fibrous supporting tissue
- bundles visible with light microscopy
80
Where is type 1 collagen found?
in hyaline cartilage, fine fibrils dispersed in the ground substance
81
Where is type 3 collagen found?
delicate branching supporting meshwork in highly cellular tissues eg. liver, bone marrow, lymphoid organs, absorb metallic silver which they are stained black
82
where is type 4 collagen found?
forms a mesh-like structure in basement membranes
83
where is tape 7 collagen found?
anchoring fibrils that link to the basement membrane
84
Where are supporting tissue cells derived from?
mesenchyme
85
What does the mesenchyme include?
- fibroblasts
- myofibroblasts
- chondrocytes/ osteocytes
- adipocytes
- defence and immune cells
86
What are fibroblasts?
most common cells - responsible for secreting extracellular matrix
87
What are myofibroblasts?
contractile function and secretion of extracellular matrix
88
What are chondrocytes/ osteocytes ?
responsible for secreting extracellular matrix in cartilage and bone respectively
89
What are adipocytes?
highly specialised for the storage and metabolism of fat, may collectively form adipose tissue
90
What are defence and immune cells?
mast cells, tissue macrophages and plasma cells, may be static or migrating elsewhere
91
What is primitive mesenchyme?
embryonic tissue form which all connective tissue is derived
92
How do mesenchymal cells look like?
- stellate shaped with delicate branching cytoplasmic extensions
- oval nuclei
- extracellular matrice is mainly ground substance, few fibres - white appearance
- permits free diffusion
93
What do mature fibroblasts look like?
- collagen fibres - dense and very pink
- fibroblast nuclei condensed and elongated in direction of collagen bundles
little cytoplasm
94
What is the main function of mature fibroblasts?
maintains the integrity of tissue by slow turnover of the extracellular matrix constituents
95
Name some variation in supporting tissues?
- may be loose eg. bowel submucosa
- where more strength is needed, pink collagen bundles are more dense, eg. muscle fascia, dura
96
What is the basement membrane made up of?
main constituents are fibrous protein collagen type 4 + structural glycoproteins laminin, ent actin and fibronectin
97
What produces the components of the basement membrane?
all produced by the epithelial cells, except for fibronectin, which fibroblasts produce
98
How many layers is the basement membrane composed of?
3 layers
99
name the three layers of the basement membrane
- lamina lucida
- lamina densa
- lamina fibroreticularis
100
What is the lamina Lucida?
relatively transparent layer abuts the plasma membrane of the basal epithelial cells
101
What is the lamina densa?
intermediate electron-dense layer
102
What is the lamina fibroreticularis?
- broad relatively electrolucent layer which merges with supporting tissue underneath
- consists of mainly type 3 collagen and fibronectin
103
What are lamina Lucida and densa made up of?
type 4 collagen and laminin
104
What is brown adipose tissue?
- highly specialised type found in newborn mammals
105
What os the role of brown adipose tissue?
temperature regulation
106
How much brown adipose tissue is contained in adult humans?
very little
107
How is brown adipose tissue arranged?
in lobules separated by fibrous septal which convey blood vessels and nerves
