Tissues Flashcards
4 main types of tissues
cells, amount of ECM, main functions
- Connective (aggregated polyhedral cells, small, lining surface or body cavities and glandular secretion)
- Epithelial (several types of fixed and wandering cells, lots, support and protection)
- Muscle (elongated contractile cells, moderate, movement)
- Nervous (intertwining elongated processes, none, transmission of nervous impulses)
Wandering cells
Can migrate and move towards/away from different signals
Epithelial tissue (location, nutrition, 3 major functions)
L: external and internal surfaces of the body, rest on a basement membrane
N: avascular, so dependent on proximity to connective tissue
F: coverings/linings (protection), absorption (in intestines), or secretions (glands). also sensation and contraction
Simple squamous epithelium
Consists of a single layer of flattened cells
Found where there is a rapid passage of chemicals
Can perform some simple secretion and some filtering
Ex: endothelium of lymphatic vessels, alveoli, lining of capillaries, some parts of kindey
Simple cuboidal epithelium
Single layer of cube shaped cells
Can allow the passage of chemicals (not as well as simple squamous)
Thicker (more protective)
Have more complex cytoplasm, and perform more complex functions in terms of secretion and absorption
Ex: secretory part of most glands, most tubules of kidney
Simple columnar epithelium
Single layer of tall cells
Nucleus tends to be elongated and localized near the basement membrane
Thickness contains many organelles and they have enough energy to carry out complex tasks
Very active in absorption and secretion
May have microvilli and/or cilia
Ex: small intestine and bronchioles
Pseudostratified columnar epithelium
Cells are tall and thin but vary in height
All touch the basement membrane, but not all make it to the apical surface
Nuclei may be at varying levels
Ex: trachea
Stratified squamous cell epithelium
Multilayered
Named based on the type of cell found at the apical surface
Multiple layers provide increased protection and durability
Stratified squamous cell epithelium
Keratinized type
Flattened superficial layer loses their nuclei and become filled with keratin
Constitutes the epidermis
Stratified squamous cell epithelium
Non-keratinized, mucosal type
Consists of several layers of cells with the most superficial layer composed of flat living cells
Lines the moist body surfaces such as mouth, esophagus, vagina
Stratified cuboidal epithelium
Consists of two or more layers of cells with most superficial being cuboidal in shape
Lines the ducts of sweat glands but otherwise uncommon
Stratified columnar epithelium
Consists of two or more layers of cells
Most superficial being columnar in shape
Uncommon but occasionally found in large excretory ducts of some glands and in the cavernous urethra
Transitional epithelium
Consists of a stratified epithelium which undergoes marked changes in appearance, depending on the degree of stretch
Lines excretory passages in the urinary system
5 types of cell junctions
- Occluding (zonula occludens or tight junctions)
- Adhering (zonula adherens)
- Desmosomes (macula adherens)
- Communicating (gap junctions)
- Adhering to basal lamina (hemidesmosomes)
Tight junctions
Also called zonula occludens
Form a barrier
Restricts the passage of water, electrolytes and other small molecules across the epithelium
Appear as fusions of the cell membranes to one another, but formed by proteins like occulin or claudin
Attached to actin
2 proteins in tight junctions involved infusion
Occulin
Claudin
Adhering junctions
Adhering
Sticking adjacent cells together
Made of proteins such as cadherin
Attached to actin filaments all around the cell
Desmosomes
Also called macula adherens Adhering Points of attachment Cells can have a bit of space between Spanned by intermediate filaments (cytokeratin)
Gap junctions
Communication
Pores formed by arrangement of connexin proteins (6) that permit passage of ions and other molecules
Zonula adherens
Below the tight junctions
Holds the epithelial cells together
Transmembrane cadherins on each cell interact with one another to form a link
Actin on the inside of the cell interacts with the junction and forms a “belt” all the way around the inside of the cell
Hemidesmosomes
Cell adhesion on the basal surface
Anchors cells to the basal lamina through laminin
Held together by integrins
Anchored to keratin filaments within cells
Exocrine gland
Retain a passage and secrete onto the surface of the epithelium
Have ducts
Can secrete mucus, serous, or sebaceous
Ex: salivary
Endocrine gland
Lost contact with the epithelium - secrete into vessels
Ex: thyroid
Can act on neighbouring cells (paracrine) or over long distances (neuroendocrine)
What is: 1 mucus 2 serous 3 sebaceous rich in?
1 glycoproteins
2 proteins and watery
3 lipids
Brightfield light microscopy
Suitable for observing the natural colours of a specimen or the observation of stained samples
The specimen appears darker on a bright background
Phase contrast microscopy
Useful for observing unstained specimens that lack a color
The optics will convert the differences in refractive index of the specimen into brightness differences
Differential Interference Contrast microscopy
Another method of deriving contrast in an unstained specimen from differences in index of refraction
Transforms the phase shift of light, induced by the specimen refractive index, into detectable amplitude differences
Utilizes optical path differences within the specimen to generate contrast the 3D appearance may not represent reality