Connective Tissue Flashcards
What determines if you can call a connective tissue dense or loose?
The density of collagen fibers
Along what do cells in loose connective tissue travel?
Cells in loose connective tissue move along fibronectin and collagen in the ECM
Reticular connective tissue is loose or dense connective tissue? What type of collagen makes up reticular fibers?
Reticular connective tissue is a type of loose connective tissue with a lot of reticular fibers. Reticular fibers are made of type III collagen. For example, lymphatic organs such as spleen, thymus and lymph node are reservoirs for lymphocytes and sites of immune system action. The parenchyma (substance) of these loose tissues is held together by this fiber network (reticulum).
though not connective tissues, the liver and kidney have a lot of what?
reticular fibers.
Collagen fibers in dense connective tissue?
larger in diameter than collagen fibers in loose connective tissue.
What do the fibers look like in dense regular connective tissue? What does this allow for?
Fibers are oriented parallel to each other. This organization provides a high level of tensile strength to withstand stress of muscle contraction and movement.
How can you tell tendons (dense regular CT) from smooth muscle?
There are nuclei of fibroblasts between fibers. However, you don’t see nuclei within fibers. This is one way of telling dense CT from smooth muscle, which looks similar. In smooth muscle, the pink structures are muscle cells which contain nuclei.
What type of tissue is the cornea? How are the fibers deposited?
Dense regular CT. The fibers are deposited in alternating layers at right angles to each other.
What type of tissue is the dermal papillae? How about the layers underneath them?
Dermal papillae (fingers of dermis that project into epidermis) contain loose C.T. The subjacent layers of dermis are full of thick collagen bundles; hence this part of the dermis is dense irregular connective tissue.
Where are fibroblasts formed from? What do they synthesize
From mesenchymal cells in the embryo; connective tissue cells that synthesize collagen and other ECM molecules
Fibroblasts have lots of what two things?
RER and golgi
Electron microscopy shows lots of activity at the plasma membrane: phagocytosis and pinocytosis. This is in what cell?
macrophages.
What do mast cells secrete? What do these contain?
release granules during allergic reactions and inflammation. Granules contain proteoglycans like heparin sulfate, histamine, and ECF-A – a chemotactic factor that attracts eosinophils
What do chemoattractants do?
Chemoattractants (neutrophil chemotactic factor and eosinophil chemotactic fator) activate endothelial cells so neutrophils and eosinophils attach to endothelium.
What are the steps for leukocytes leaving blood to go to tissue? specific ligands in order?
- attachment- leukocytes attach to endothelium
- rolling- They roll along endothelium with transient interactions
- activation- Leukocytes respond to chemoattractant from activated macrophages on other side of endothelium
- Arrest and adhesion strengthens- Tethering through cell-surface ligands stops the leukocyte
- migration (diapedesis)- leukocyte passes through endothelial cells
Ligands in order: selectins, integrins and ICAMs, PECAM-1
Leukocyte Adhesion Deficiency =
genetic lack of beta-integrins: frequent infections because leukocytes cannot enter connective tissue
Function of neutrophils? When are they seen in CT?
Function is to phagocytose bacteria and destroy them with lysosomal enzymes. Only seen in CT during inflammation, come from blood otherwise.
What do eosinophils do? Where are they from? What do they look like?
Bi-lobed nucleus. Have pink acidophilic granules that are during allergic reactions and parasitic infections; also phagocytose antigen-antibody complexes. Also from blood, but found in CT.
Where are basophils from and what do they do?
Another granulocyte from blood; granules similar to those of mast cells; released in allergic reactions
When and where are lymphocytes found in CT?
Found in connective tissue sites of infection and inflammation. Also found in connective tissue underlying epithelia which are continually exposed to microorganisms and other foreign antigens
What three types of cells are normally found in CT near layers of epithelia, where microbes might come?
macrophages, lymphocytes and plasma cells
Cytoplasm and golgi of plasma cells?
Enlarged cytoplasm. Clear (poorly stained) area in cytoplasm represents Golgi apparatus
What hormones are secreted by adipocytes and what do they do?
- Leptin - a circulating satiety factor
- Angiotensinogen - increases blood pressure
- Steroid hormones (testosterone, estrogen and glucocorticoids)
- Growth factors: TNF-alpha, TGF-beta, IGF-1 and cytokines:
Ghrelin and Peptide YY:
What are they and what do they do?
Short or long term for each?
- Both are GI peptide hormones
Ghrelin- Appetite stimulant
Peptide YY- Appetite supressor
Short term weight regulation for both.
What type of weight regulation is leptin in?
What is it, what does it act on?
Obese humans have high or low levels?
Long term weight reg. A satiety factor secreted by fat cells; acts on hypothalamus. Defects in leptin or leptin receptor lead to genetic obesity in mice. Leptin treatment causes weight loss in mice, but not in humans. Obese humans have high leptin levels and do not respond to leptin. Function thought to be protection of body against weight loss in food deprivation.
Insulin is in what type of weight reg?
What does it act on?
Long term weight reg. Enhances conversion of glucose to lipids in fat cells. Also acts on hypothalamus
Amylin is what type of weight reg?
Secreted from?
What does it do (2)?
Long term weight reg. Secreted from b-cells in pancreatic islets with insulin. Slows gastric emptying and suppresses increase in blood sugar
- Purpose of PPAR?
- Early lipoblasts or preadipocytes are where? Known as?
- What happens to midstage lipoblasts?
- What happens to late lipoblasts?
- Are lipids membrane bound?
- Peroxisome proliferator-activated receptor gamma (PPAR): transcription factor that plays a major role in differentiation
- Early lipoblasts or preadipocytes along small blood vessels in fetal stage – “primitive fat organs”
- Midstage lipoblasts become oval; many vesicles and lipid droplets around the nucleus
- Late lipoblast: lipid vacuoles coalesce to form large lipid vacuoles
- lipid is not membrane-bounded
- Fat droplets in brown adipose?
- Differentiation is controlled by what?
- Serve as a source of?
- High in who?
- Lipid is mobilized/head generated after stimulization of what?
- Where is the nucleus in brown adipose?
- Numerous fat droplets in cells (reticulated appearance)
- Differentiation controlled by norepinephrine (NE)
- Source of heat resulting from expression of mitochondrial uncoupling protein, UCP-1
- High in newborns, offsets high surface-to-mass ratio
- Lipid is mobilized and heat generated after stimulation by sympathetic nervous system
- nucleus is central!
Which cells are resident cells?
fibroblasts, adipose, macrophages, mast cells, dendritic cells, chondrocytes
Is loose CT vascularized?
Amount of collagen fibers?
Well vascularized
sparse collagen
Is dense regular CT vascularized?
Amount of collagen?
avascular
more numerous collagen
Is dense irregular CT vascularized?
How is the collagen?
what else is present?
well vascularized
thick ropy collagen arranged in no particular pattern
typically only fibroblasts present
How can you recognize a plasma cell?
clock-faced nuclei.
how can you recognize a mast cell?
look like fried eggs. dark nucleus. granules in cytoplasm.
Reticular fibers are made of what type of collagen?
collagen type III
Overproduction of what in Prader-Willi syndrome?
Overproduction of ghrelin in Prader-Willi Syndrome
