Connective Tissue Flashcards
what does the connective tissue mainly consist ?
ECM of protein fibers, ground substance, and cells
originate
where do connective tissue originate?
from the Mesenchyme – mesoderm
what does mesenchyme largely consist ?
viscous ground substance with few collagen fibers and mesenchymal cells
Mesodermal cells give rise to ______________ and are the ________ stem cells to other tissues such as blood, vascular endothelium, and muscle
connective tissues, stem cells
describe embryonic mesenchyme
- undifferentiated
- large nuclei
- scant collagen (white looking)
- look like floating sperms with tails
- high synthetic activity
- stem/progenitor cells
- spindled shaped like fibroblasts
Why do embryonic mesenchyme have large nucleus?
because they are always actively dividing
fibroblasts, adipocytes, macrophages, mast cells, adult stem cells, plasma cells, lymphocytes, eosinophils, monocytes, basophils, neutrophils are all cells derived from?
bone marrow
fibroblasts, adipocytes, macrophages, mast cells, adult stem cells are all what kind of connective tissue cells?
resident cells
plasma cells, lymphocytes, eosinophils, monocytes, basophils, neutrophils are what kind of connective tissue cells ?
transient cells
What do transient cells do and give an example
go in and out
ex: from blood –> peripheral tissue
what cells secret immunoglobins ?
plasma cells
what proteins do fibroblasts secrete ?
- the different types of
collagen - elastin / elastic fibers
- proteoglycans
- glycosaminoglycans
- Multi adhesive glycoproteins of the ECM
fibroblasts form ________ cells.
fiber
What is a characteristic of fibroblasts?
- thin, attenuated cytoplasm
- sharp ends
- resident cells
- large nucleus
- ovoid
- euchromatic (less dense, transcriptionally active)
- prominent nucleolus
-ER, Golgi Apparatus
fibroblast vs. fibrocyte
fibroblast: active cell (euchromatic)
fibrocyte: quiescent (quiet, no function cell (heterochromatic)
what are fibroblasts involved in wound healing called?
myofibroblasts
where are adipocytes derived from?
mesenchyme/ mesoderm
what are the two types of adipocytes, what colors are they, and what are their functions?
unilocular (white) & multilocular (brown)
- storage of neutral fats for insulation and heat generation
- key regulators of energy metabolism
- sensitive to hormones and nervous stimuli
What are the chief phagocytic cells of the human body and are found in loose connective tissue or the interstitium?
macrophages
where do macrophages derive from?
RBCs ka monocytes that enter the bloodstream from the bone marrow
In connective tissue, monocytes differentiate into macrophages also known as…
histiocytes
True or False: Macrophages are difficult to identify in routine hematoxylin and eosin (H&E) stained sections.
True
Macrophages contain numerous ___________ and are actively
phagocytic for material in connective tissue or interstitium.
residual bodies of lysosomes (numerous folds, fingerlike projections)
What feature assists in identifying macrophages ?
indented/kidney shaped nucleus
What substances do macrophages ingest in the alveolar interstitium (lung)?
carbon deposits (look like holes/huge pores/pen stabs)
What are alveolar macrophages clinically referred to ?
dust cells
While the main function of macrophages is to engulf/ digest (phagocytic), they also act as ___________ in immune reactions
antigen presenting cells - ingesting antigens and secreting cytokines that influence immune response, anaphylaxis (swelling of throat, tongue), and inflammation
what are the names of the multinucleated foreign body giant cells fuse to make?
Langhans cells
True or False: Mast cells are bone marrow-derived
True
Are the dense mast cell granules that exhibit metachromasia (certain tissues or cells stain a different color than the dye used) acidophilic or basophilic?
mast cell granules are basophilic
what do mast cells release that cause increased vascular permeability and smooth muscle contraction?
histamine
what do mast cells release that activate various mediators of inflammation?
serine protease
what do mast cells release that attract leukocytes?
eosinophil and neutrophilic chemotactic factors
what do mast cells release that direct activities of leukocytes?
cytokines
what do mast cells release that are precursors converted to prostaglandins, leukotrienes, and other mediators of inflammation?
phospholipids
where are mast cells found?
- near small blood vessels in skin and mesenteries
- digestive and respiratory tract
after activation, what do mast cells granules extrude?
mediators and generate lipid-derived substances that induce immediate allergic inflammation
what do mast cells look like physically?
- nucleus very hard to see
- big round purple flowers or black
- vascular permeability
how can plasma cells be identified?
position of their nuclei and pattern of heterochromatin
Why is the plasma cell cytoplasm basophilic?
due to rough ER content
Why does the plasma cell membrane have a great amount of rough ER ?
Because the cell is actively synthesizing and secreting
protein
How many nucleoluses are in the plasma cell ?
1 nucleolus
plasma cells are derived from …. and why?
B-lymphocytes to produce immunoglobins for immune system
Because plasma cells don’t undergo mitosis, they are terminally…
differentiated cells
where are plasma cells normally found and what is their life span?
approximately 2 weeks
Leukocytes are known as the _______ cells in the connective tissue.
wandering
How do Leukocytes leave blood?
by migrating between endothelial cells of venules to enter connective tissue
when are leukocytes most numerously seen?
during inflammation response to injury and foreign substances
What common leukocyte cell is seen in acute cases?
neutrophils
What common leukocyte cells are seen in chronic situations?
lymphocytes & monocytes
What common leukocyte cell is seen in parasitic cases?
eosinophils
What is the most abundant protein secreted largely by fibroblasts and the key fiber on all connective tissues, epithelial basement membrane and external laminae of muscle and nerve cells?
Collagen
How many collagens are there and what are there 3 subgroups?
28
- 4 fibrillar: Types, I, II, III, V
- 2 network-forming collagens: Types IV, X
- 1 linking/anchoring collagen: Type
VII
describe Type I Collagen
- most abundant form of eosinophilic bundles called collagen fibers
- connective tissue (dermis in skin, tendon, ligament, bone, & organ capsules)
- fibrillar
describe Type II Collagen
- found in cartilage and vitreous body
- fibrillar
describe Type III Collagen
- argyrophilic reticular fibers
- found in skin, muscle, blood vessels
- fibrillar
describe Type V Collagen
- fetal tissue, skin, bone, placenta, & interstitial tissue
- fibrillar
describe Type IV Collagen
- basal & external lamina
- supports epithelial cells
- serves as filtration
-network-forming
Describe Type X Collagen
- hypertrophic zone in endochondral bone formation, increasing bone density
-network-forming
Describe Type VII Collagen
- epithelial basement membrane
-anchors the basal lamina to underlying reticular lamina
What is collagen secreted by?
fibroblasts
How does collagen appear in histology?
overlapping paint brush look
- dark and light bands
What does Masson Trichrome stain and what color does it appear?
Masson Trichrome stains collagen
- collagen bundles appear blue
What Type Collagen do reticular fibers consist of ?
Type III Collagen
What do reticular fibers form?
an extensive network called reticulum
What color are reticular fibers stained when impregnated with silver salts?
black
why are reticular fibers termed argyrophilic ?
because they have a high affinity for silver salts and can be stained by them
Why do reticular fibers stain also stain with PAS?
due to high sugar chains bound to Type III Collagen
what are reticular cells
fibroblasts that produce reticular fibers
where are reticular cells found?
- reticular lamina of basement membrane
- surrounding adipocytes, smooth muscle, nerves, & blood vessels
- supporting stroma for liver & endocrine glands
- adrenal cortex
- stroma of hemopoietic tissue (spleen, lymph nodes)
what do reticular fibers sort of look like?
frog eggs, silver stain, black fibers
what are elastic fibers?
thin fibers that form sparse networks interspersed among collagen bundles
Why are elastic fibers seen in organs that are subjected to stretch and bending?
due to their rubberlike properties
what are elastic fibers called in very large arteries?
elastic lamellae
what does fibrillin form?
network of microfibrils
- embedded in larger mass of cross-linked elastin
- many lysine rich regions
when fibrillin micro fibrils decompose, ________ converts the lysine amino groups to from a desmosine ring to maintain the rubberlike properties.
lysyl oxidase
fibrillin makes ________ that are secreted by fibroblasts and smooth muscle cells
microfibrils
_______ is deposited on microfibrils and forms an _______________ structure
elastin, amorphous
in a hematoxylin & orcein stain, how can one identify elastic fiber?
dark stained, thin amongst pink acidophilic collagen fibers
- look wavy in H&E stains between multiple nuclei of smooth muscle cells
describe ground substance
viscous clear substance with slippery feel and high water content
what are the 3 major divisions of connective tissue?
1.Connective tissue proper
2. Embryonic connective tissue
3. Specialized connective tissue.
What are the 2 types of Connective tissue proper?
Loose and Dense (irregular & regular)
describe loose connective tissue
aka areolar tissue
- found below lining epithelial and fills spaces between tissues
describe connective tissue
contains fibroblasts & increased bundles of Type 1 Collagen
how can you distinguish dense irregular and dense regular connective tissue?
irregular: collagen fibers interwoven, dermis, capsules
regular: collagen arranged parallel, tendons, aponeuroses, ligaments
blood and lymphatic vessels found in Connective Tissue
