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
Basic (or cationic dyes)
Have positively charged color radicals forming electrostatic linkages with acidic groups, such as phosphate groups in nucleic acids
3 Examples of basic dyes
Toluidine blue
Methylene blue
Hematoxylin
Acid (or anionic) dyes
Have negatively charged color radicals establishing electrostatic linkages with basic groups such as basic proteins
3 Examples of acid dyes
Orange G
Acid fuchsin
Eosin
Magnification equation
Image size/actual size
Numerical aperture
The ability of the lens to collect the light
What cells make collagen?
Fibroblasts
What two cell lines do connective tissue come from? And where did these cells originate?
From hemaotpoietic stem cells and undifferentiated mesenchymal cells
These came from the mesoderm of the germ layer of the embryo
Fibroblasts
Synthesize collagen, elastin, proteoglycans and glycoproteins
Most common type of cell in connective tissue proper
Proteoglycans
Made up of glycosaminoglycans
Very good at absorbing water (90% of the ECM)
ECM is very good at resisting compressive forces because of this
Protein core and an extension of GAG (most GAGs can attach to core proteins
Glycosaminoglycans
Linear (no branches) polysaccharides consisting of repeating disulphide units
They are charged and attract water (hydrophilic)
They are inflexible
Resistant to compressive forces
Collagen fibers
Wide and wavy in appearance Stain pink Most abundant protein of ECM and body 30% of the protein in the body is collagen Over 25 different types of collagen
Elastic fibers
Thing, flexible fibers made from elastin
Stain black
Branched and coiled
May be stretched up to 150% of their resting length
Produced by fibroblasts and smooth muscle cells of arteries
Reticular fibers
Thin collagen fibers - mostly type 3 collage
Spider web appearance
Stain black
Produced by reticular cells
3 things connective tissue proper is made up of
- Cells (mostly fibroblasts)
- A homogenous ground substance or matrix, which may be tissue fluid, an amorphous gel-like material, or solid
- Extracellular fibers (collagens, reticular and elastic)
Loose connective tissue
Contains many cells, a loose arrangement of fibers, and moderately viscous fluid matrix
Many cells, few fibers
Areolar connective tissue
A type of loose connective tissue
Slippery and supportive outer coat of organs
Attaches epithelial tissue to other underlying tissue
Reticular connective tissue
A type of loose connective tissue
Web like internal skeleton for some organs
Dense connective tissue compared to loose
Contains more fibers but less matrix and fewer cells when compared to loose
Regular connective tissue
A type of dense CT
Collagen fibers are densely packed and arranged in parallel
Found in ligaments and tendons
Resistant to tension forces in one direction, but allow some stretch
Attenuated fibroblasts found between groups of fibers
Irregular connective tissue
A type of dense CT
Contains a dense woven network of collagenous and some elastic fibers in a viscous matrix
Found in joints and forms the dermis of skin
Impact resistant, strength in all directions
Pericytes
Contractile cells that wrap around the endothelial cells of capillaries and venules throughout the body
White Adipose Cells
Responsible for the synthesis and storage of fat (long-term energy reserves)
Largely made up of TAGs - high in energy
Other less efficient energy source is glycogen (mainly liver, skeletal muscle)
Unilocular
Unilocular definition
The cytoplasm and nucleus squeezed to a thin rim around the periphery of the cell (cells do not divide)
Forms adipose tissue when present in large numbers
Brown adipose cells
Multilocular
Provide body heat (thermoregulation)
Multilocular
These cells contain many small fat droplets, and groups of these cells form brown fat
3 types of cartilage
- Hyaline (most common, found in joints and resp passages, collagen fibers)
- Fibrocartilage (associated with dense connective tissue and is resilient, in vertebral discs, strongest (most fibers))
- Elastic (more flexible, in the ear, elastic fibers, most cells)
Functions of compact and spongy bone
Compact: strong, so supports the entire body
Spongy: porous nature = greater SA - allows bone marrow to develop in the region
Canaliculi
Microscopic canals that radiate out from the lacunae
Lamellae
Concentric layers of the osteon
Osteoblasts
Synthesize the organic components of the matrix (collagen, proteoglycan, and glycoproteins)
Located at the surface of bone tissue
Differentiate into osteocytes
Osteocytes
Derived from osteoblasts
Found in lacunae (cavities) Involved in the maintenance and mineralization of bone
Osteoclasts
Multinucleated cells involved in the reabsorption of bone tissue
Smooth muscle
Surrounding blood vessels and intenstine
Single central nuclei
Lack striated appearance
Skeletal muscle
Movement of skeleton
Long fused cells
Multiple offset nuclei
Striated appearance
Cardiac muscle
Contraction of the heart Branched cells Single offset/central nuclei Striated Has intercalated discs
Neuroglia
Or glial cells
Assist the propagation of the nerve impulse and provide nutrients to the neuron
Mesothelium
The simple squamous epithelium that covers the body cavities
3 parts of connective tissue
Cells
Ground substance
Fibers
Stroma
Connective tissue within organs
Forms a structural framework that aids in organ function
Some functions of connective tissue
Forming a site for storage of fat (e.g., storage of energy reserves) Aiding in the defense and protection of the body (e.g., infection) Reduces friction (e.g., reduction of wear on joints) Repair after injury (e.g., fibroblast remodeling of damaged tissue). Bones, cartilage provide structural form while ligaments hold bones together, and tendons attach muscles to bone. Blood transports gases, nutrients, waste, performs immune functions, wound healing.
