session 2: cells/tissues + connective/ adipose tissue Flashcards
what are cell junctions?
types?
structures found between adjacent cells, making sure they are tightly adhered together
What are the 3 cell junctions?
Tight junction
Desmosomes
Gap junctions
What are tight junctions ?
impermeable junction that prevents moleculs from passing
What are desmosomes ?
anchoring junctions that bind adjacent cells together
What are gap junctions?
communicating junctions that allow ions and small molecules to pass
All cells sit on..?
basement membrane
How are cells attached to the basement membrane?
Hemi-desmosomes
Focal adhesion
Hemi-desmosome?
While desmosomes link two cells together, hemidesmosomes attach one cell to the extracellular matrix
What are the functions of focal adhesions?
Anchor intraellular actin filaments to the basemment membrane
play a role in call movement “migration of epithelial cells of skin”
What are the functions of integrins?
- attach cell to ECM
- activate signal transductionpathways from ECM to cell upon ligand binding
- immune patrolling
- cell migration
- binding to cells by certain viruses
what are integrins?
transmembrane receptors that facilitate cell-extracellular matrix (ECM) adhesion.
Which of the following is involved in cell migration?
(Gap junctions, desmosomes, focal adhesions, hemi-desmosomes, integrins)
focal adhesions
integrins
which of the following in NOT involved in lateral domain cell contact?
(desomosomes, gap junctions, hemi-desmosomes, tight junctions)
hemi-desmosomes
What is this communication called?
autocrine
Why are cultured cells different than normal cells?
when they come into contact with other cells they stop growing “Contct inhibition”
they have a limitd life span “senescence”
Explain Senescence?
loss of a cell’s power of division and growth
What are gap junctions made of?
channels of Connexon
Explain the paracrine communication?
cell-cell communication in which a cell produces signals/ chemicals to induce changes in nearby cells
Explain the endocrine communication?
Communication between endocrine organs, as they are ductless and secrete directly into the blood stream
Explain the synaptic communication?
Communication between neurons is achieved at synapses by the process of neurotransmission and the release of neurotransmitters
NA - sympathetic
Ach - parasympathetic
Explain the neurocrine communication?
What 3 areas can we find them in our body?
electrical signaling traveling along the nerve and releases chemicals into the blood stream instead of at a synapse
Examples: hypothalamus, posterior pituitary, adrenal medulla
What process involved in cell replacement?
mitosis
Necrosis vs. apoptosis?
explain necrosis?
Physical distrusting through cell injury,
bacterial toxins, or nutritional deprivation
-> cell swells then bursts -> cytotoxic
cellular components spill out -> damage
and inflammation
explain apoptosis?
Bcl-2 protein on outer mitochondrial membrane inhibits apoptosis,
deactivating Bcl-2 initiates apoptosis -> catabolic reactions take place +
enzymes digest cytotoxic compounds and DNA fragments-> Caspases:
target specific proteins in nuclear lamina and cytoskeleton -> cell
repackaged for safe removal -> cell shrink and fragments into small
apoptotic bodies to be phagocytized
What type of cell death causes
1. inflammation?
2. Caspases activation?
- necrosis
- apoptosis
What is meant by Stable cells?
Where can we find them?
Stable cells are cells that multiply only when needed.
They spend most of the time in G0 phase
fibroblasts, endothelium, SMCs
liver, the proximal tubules of the kidney, and endocrine glands
What is meant by Static/ permenant cells?
Where can we find them?
cells that are incapable of regeneration
This includes brain cells, neurons, heart cells, skeletal muscle cells and (RBCs?)
What is inherited exclusively through the maternal lineage?
mitochondia
What is meant by Labile cells?
Where can we find them?
cells that multiply constantly throughout life
including hepatocytes, skin cells, GI tract, and blood cells in the bone marrow
which cell type is associted with cancer and why?
labile/ renewing cells, bcuz constantly dividing cells have a higher risk of becoming malignant and develop cancer, dividing uncontrollably
which cells that are rarely cancerous? why?
muscle cells, since they are not constantly dividing cells “static/ permenant”
which of the following methods of ell communication involve scretion of hormone?
paracrine, endocrine, autocrine, meurocrine, direct contact
endocrine
neurocrine
where can we find anaerobic prokaryotes in our body?
colon
prokaryotes vs. eukaryotes?
Explain Endosymbiosis?
aerobic bacteria wa taken into an anaerobic eukaryote and fomed the mitochondria
what are the 4 basic tissue types?
epithelial
muscle
nerve
connective tissue
what are the 6 specialized connective tissues?
adipose
lymphatic
blood
hemopoietic
cartilage
bone
What is an Epithelium? Function?
A tissue composed of cells that covers the exterior body surface and
lines internal closed cavities and body tubes that communicate with
the exterior.
Epithelium also forms the secretory portion of glands
and lines their ducts.
specialised epithelium functions as
receptors for the special senses (smell, taste, hearing and vision)
What are epithelioid?
Where can we find them?
activated macrophages resembling epithelial cells, but lack an apical surface
found in:
- leyding cells (testis)
- lutein cells (ovary)
- islets of langerhans (pancreas)
- parenchyma (adrenal gland)
what structures can we find on th apical domain of epithelial cells?
microvilli
stereovilli
cilia
what are Microvilli?
location?
membrane protrusions that increase the surface area for diffusion (brush borders), found in:
intesitines
kidney tubules
eggs (sperm attachemnt)
WBCs (migration)
what are Stereovilli?
microvilli limited to epididymis and
sensory hair cells of ears
what are cilia?
motile ctoplasmic processes that can bat synchrony with rapid forward movement “effective stroke”, and slow return “recovery stroke”
found in:
tracheobrachial tree
oviducts
What is a connective tissue?
connective tissue is sparsely populated by cells and contains an extensive extracellular matrix consisting of protein fibers, glycoproteins, and proteoglycans.
The function of this type of tissue is to provide structural and mechanical support for other tissues, and to mediate the exchange of nutrients and waste between the circulation and other tissues
Give examples of wondering and fixed cells?
Wondering: plasma cells, macrophages, WBCs, mesenchymal cells
Fixed: melanocytes, macrophages, mast cells, fibroblasts, adipocytes
What are the 3 types of loose connective tissue?
Areolar, adipose, reticular
What are the functions of connective tissue?
- Connects cells to form tissues, connects tissues to form organs and connects organs to form the body. Some tissues provide support as well as connecting (cartilage and bone)
- Transportation - provide a medium for diffusion of nutrients and wastes
- Protection - provide a cushion between tissues and organs and provides insulation (adipose tissue)
- Storage (adipose tissue)
- Defense against infection (blood, lymph, fixed and wandering cells)
- Wound healing (macrophages, fibroblasts, myofibroblasts)
What are the 3 main components of connective tissue?
Cells, fibers, ground substance
What are the 3 main fibers found in connectives tissues?
Collagen – Flexible with high tensile strength
Reticular – Provide a supporting framework/sponge (type III collagen)
Elastin – Allows tissues to recoil after stretch or distension
Describe the ground substance in connective tissues?
Components?
Ground substance is a viscous, clear substance with a slippery feel.
It has a high water content. Composed of proteoglycans
- A proteoglycan is a large macromolecule consisting of a core protein to which glycosaminoglycans are covalently bound
- Glycosaminoglycans (GAGs) are long-chained polysaccharides.
GAGs attract water to form a hydrated gel that permits rapid diffusion but also resists compression.
What type of Glycosaminoglycans is found in cartilage?
Function?
hyaluronic acid that is bound to proteoglycans by a link protein to form giant hydrophilic macromolecules.
The swelling pressure or turgor that occurs in cartilage ground substance allows it to resist compression without inhibiting flexibility
What is the extracellular matrix?
Complex meshwork of proteins and carbohydrates that consists of ground substance and fibres
Loose vs Dense
connective tissue?
Loose
– Many cells
– Sparse collagen fibres
– Abundant ground substance
– Viscous, gel-like consistency
– Important role in transport (by diffusion)
Dense
– Few cells, nearly all fibroblasts
– Many collagen fibres
– Little ground substance
components of connective tissue
Where can we find loose connective tissues?
beneath epithelia (to facilitate diffusion)
Associated with epithelium of glands
around small blood vessels
what type of connective tissue is found in the superficial layer of the skin?
loose
what type of connective tissue is found in submucosa of the colon?
Loose
What are the types of dense CT?
Regular
– Collagen fibres are arranged in parallel bundles and are densely packed. Between the bundles are fibroblasts
– Designed to withstand stress in a single direction
– Seen in tendons, ligaments and aponeuroses
Irregular
– Collagen fibres are arranged in bundles orientated in various directions. Between the bundles are fibroblasts
– Designed to withstand stress in multiple directions
– Examples are submucosa of intestine and deep layers of dermis
Name what the arrows are pointing at?
Rows of elongated flattened fibroblasts lie between the collagen bundles
What is the myotendinous junction MTJ?
complex specialized region located at the muscle-tendon interface that represents the primary site of force transmission
What type of connective tissue is found in the anterior cruciate ligament?
Dense regular
label
What type of CT is found in the Dermis?
Dense irregular
gylcosaminoglycans repel water X
it contain many collagen fibers
all exept the last
What are fibroblasts?
Fibroblasts synthesise and secrete both ground substance and the fibres that lie within the ground substance
They are very important in wound healing and are the cells
primarily responsible for the formation of scar tissue
What are myofibroblasts?
modified fibroblasts that contain actin. They
are responsible for wound contraction when tissue loss has occurred
What do fibroblasts secrete?
Region of synthesis?
Procollagen synthesized from the RER, which assembles into collagen fibrils
What are macrophages? Functions ?
Macrophages are derived from blood monocytes which move into loose connective tissue, especially when there is local inflammation
Macrophages are phagocytic and can degrade foreign organisms and cell debris
Macrophages are ‘professional antigen presenting cells’ (i.e. they can present foreign material to the T lymphocytes of the immune system)
What are mast cells? What do they secrete?
Found in connective tissue near blood vessels, but absent from the central nervous system to avoid damaging effects of oedema there
Mast cell cytoplasm contains abundant granules
These granules contain:
• Histamine (increases blood vessel wall permeability)
• Heparin (an anticoagulant)
• Substances that attract eosinophils and neutrophils
Mast cell degranulation induces which type of hypersensitivity?
Type I “ immediate”
Explain the process of mast cell degranulation?
Mast cells become coated with Immunoglobulin E (IgE), molecules which specifically bind allergens. When an allergen cross-links these surface-bound IgE molecules, the contents of the granules are all rapidly released from the cell.
The secretions of the granules can result in immediate hypersensitivity reactions, allergy and anaphylaxis.
What is collagen?
How many type?
main structural protein in the extracellular space in the various connective tissues
28 types identified
What type of collagen is reticulin?
Type III collagen
What type of collagen is the most abundant in our body?
Type I collagen
Which type of collagen that does not form fibers?
Where can we find it?
Type II collagen
Fibrils form fibres around muscle and nerve cells and within
lymphatic tissues and organs.
It is called reticulin
Which type of collagen found in hyaline and elastic cartilage ?
Type II collagen
What type of collagen found fin skin?
Type I collagen
Which type of collagen is found in the basement membrane?
Type IV collagen in the basal lamina
Explain the collagen fibril production process?
Fibroblasts secrete procollagen that is converted to collagen
molecules outside the cell.
The collagen molecules are then aggregated to form the final collagen fibrils
In some tissues fibrils group together to form collagen fibers
Note that Vitamin C is required for the intracellular production of procollagen.
Vitamin C deficiency leads to scurvy which include poor wound healing and impaired bone formation
What is scurvy?
Main cause?
Vit. C deficiency = not enough collagen = bruises easily
- muscle and joint pain
- tiredness
- the appearance of red dots on the skin
- bleeding and swelling of the gums
What is osteogenesis imperfecta?
Main cause?
genetic bone disorder (autosomal dominant) characterized by fragile bones that break easily, and caused by abnormal type I collagen
the picture shows dense iregular tissue.. label
TEM of macrophage.. label
What type of collagen is found in lymph nodes?
Type III
Where can we fin elastic fibers?
Dermis
Artery walls
Lungs
What is Marfan’s syndrome?
Main cause?
Features?
Marfan’s syndrome is an autosomal dominant disorder in which expression of the fibrillin gene is abnormal such that elastic tissue is abnormal.
Sufferers are abnormally tall, exhibit arachnodactyly, have frequent joint dislocation and can be at risk of catastrophic aortic rupture.
What layer of blood vessels can we find elastic fibers, and collagen?
Tunica media - elastic fibers
Tunica adventitia - collagen
What cells are responsible of producing elastin, collagen and matrix in the tunica media of the aorta?
Smooth muscle cells
What is the main cause of pneumothorax?
Loss of lung elastic recoil
What are the 2 types of fat cells?
White and brown
Why do adipose tissue show as empty balloons on histology?
because the toluene and xylene, used in tissue preparation, have dissolved away the lipid.
Main functions of adipose tissue?
Adipose tissue contains fat, a fuel reserve, but also has a role in thermal insulation and in shock- absorbtion.
White vs brown adipose tissue?
- *White** - unicellular
- *Brown** - multicellular: each contain many lipid droplets and a central nucleus
What is the main function of brown adipose tissue?
These cells are found close to the scapula, sternum and axillae, especially in the newborn.
They Are also present in the upper chest and neck of adult
The brown colour is due to the rich vascular supply and abundant mitochondria.
There is thus a high respiratory capacity for the generation of heat ‘Non-shivering thermogenesis’ is important for babies and for hibernating animals
