Connective Tissue Flashcards
what a large difference between epithelial tissue and connective tissue?
connective tissue is directly supplied by blood/lymphatic vessels/nerves, epithelial tissue is not
what embryo layer does connective tissue develop from?
mesodermal layer, mesenchyme cells
shape of mesenchymal cells
stellate and spindle-shaped (fusiform) with EUCHROMATIC nuclei and PROMINENT nucleoli, the extracellular matrix is mostly ground substance (hyaluronic acid)
what does euchromatin look like in a stained cell
lightly stained nucleus, with a prominent, dark and solid nucleolus
what does heterochromatin look like in a stained cell
darkly stained clumps in the nucleus, cannot see nucleolus
where would you see a euchromatic nucleus?
a ribosome
activity of adipocytes
storage of fat for energy and heat production
activity of fibroblasts and derivatives (chondroblasts, osteoblasts)
production of ECM fibers and ground substance
activity of plasma cells
antibody production
activity of macrophages
cytokine production, phagocytosis, antigen presentation
activity of mast cells
production of inflammatory mediators
activity of leukocytes (neutrophils, eosinophils, basophils, lymphocytes)
immune defenses, migratory from the blood and lymph
where are connective tissue cells derived from?
hematopoietic stem cells (bone marrow) or undifferentiated mesenchymal cells
which are the most common cells in connective tissue?
fibroblast
what do fibroblasts look like in a stained cell
stellate, spindle shaped, ovoid or flattened nuclei with light pink collagen surrounding
what are fibrocytes?
less active fibroblasts
how are fibroblasts stimulated to divide?
specific growth factors
how are fibroblasts functional in a wound?
they synthesize connective tissue fibers to create scar tissue they also can use specialized fibroblasts called myofibroblasts to bring wound edges together (myofibroblasts have actin)
what do macrophages look like in a stained cell
large, irregularly shaped cell with large nucleus, many lysosomes, well developed RER and golgi “lumpy bumpy junk in the cytoplasm”
what do macrophages do
function as phagocytes, antigen presenting cells, and cytokine producers
what are epithelioid cells
activated macrophages resembling epithelial cells
what are multinucleated giant cells
epithelioid cells that have merged together, usually see a “horseshoe” arrangement of nuclei around the apical side of cell
what condition could arise from epithelioid cells or multinucleated giant cells
granulomas, because they are kind of like a large aggregate
what do mast cells look like in stained cell
large oval cell, cytoplasm filled with dark basophillic granules that sometimes obscure small round nucleus (cytoplasm darker than nucleus)(granule filled)
what are mast cells derived from?
same progenitor in bone marrow as basophils
what is the function of mast cell?
inflammation, allergies, innate immunity, tissue repair
what does histamine do
causes increased vascular permeability and vasodilation
what does heparin do
is an anticoagulant
what are examples of inflammatory mediators
serine proteases, cytokines, chemotactic factors, phospholipid precursors
what do granules do in the mast cell
stored, and when they degranulate, they release vasoactive mediators like histamine, heparin, and inflammatory mediators
how to stain mast cells
dont use paraffin, will degenerate granules. use H&E and toluidine blue
plasma cells stained
large, ovoid cells with basophilic cytoplasm, clock face appearance due to alternating areas of heterochromatin and euchromatin, golgi can be seen next to nucleus as a paler stain
where are plasma cells derived
B lymphocytes
type of connective tissue fibers
- collagen 2. elastic 3. reticular fibers
what is the most abundant protein in the body
collagen
what color does collagen stain with H&E?
pink
main function collagen
tensile strength
important structural note about collagen
EVERY 3RD AMINO ACID IS GLYCINE
how to remember collagen types 1-IV
I - Skin, bone, tendon, fascias II - Cartilage III - Arteries, smooth muscle IV - Basement membrane
describe type I collagen synthesis
- procollagen alpha chains form in the RER by fibroblasts 2. proline and lysine residues hydroxylated by prolyl and lysyl hydroxylase 3. hydroxylysines undergo glycosylation 4. procollagen triple helix is assembled and secreted through exocytosis (into ECM, where it is assembled and matured) 5. procollagen triple helix is cleaved of nonhelical end and aggregated into collagen fibrils in the ECM 6. the fibrillar structure is reinforced with lysine cross link formation via lysyl oxidase
what is required for type I collagen synthesis regarding hydroxylation?
vitamin C and copper are needed for the proline and lysine to be hydroxylated
what hydroxylated area is glycosylated?
hydroxylysine is glycosylated
what causes scurvy?
vitamin C deficiency, leading to decreased type I collagen production due to inability to hydroxylate proline and lysine
what diseases can be caused by type I collagen mutation?
ehler’s danlos syndrome and osteogenesis imperfecta
what is the makeup of reticular fibers
heavily glycosylated type III collagen
where are reticular fibers found
extensive FLEXIBLE networks of ECM within organs that need a lot of structure (liver, endocrine glands, spleen, lymph nodes, bone marrow), they provide framework for cell attachment
how are reticular fibers seen best and why?
silver salts because they are argyrophylic PAS staining due to the extensive glycosylation reticular fibers look branch like
what do elastic fibers look like stained
thinner than collagen, form SPARSE networks interspersed with collagen bundles, hair like
function of elastic fibers
needed for tissues subject to bending and stretching, like the wall of large arteries, dermis, or mesentery
what 2 unique amino acids are found in elastin and what is their function
desmosine and isodesmosine - consist of modified lysine residues they help form crosslinks
where is elastin assembled and matured?
ECM
what are elastic fibers made up of?
tropoelastin (contains desmosine), fibulin, and fibrillins
how are elastic fibers best visualized
orcein or fuscin stain
what causes marfan syndrome?
fibrillin 1 mutation, therefore elastic fibers are not manufactured.
symptoms marfan syndrome
tall, long arms, long fingers, long toes, increased risk of mitral valve prolapse, dilation of root of aorta and aortic dissection
what diseases are caused by mutations in elastic fibers?
marfan syndrome cutis laxa
what is ground substance made up of?
GAG proteoglycan glycoprotein
function of ground substance
fills the space between cells and fibers, acts as lubricant and barrier due to viscosity (rich in water), important in cell adhesion and signaling
what are glycosaminoglycans
linear polysaccharides with repeating disaccharide units consisting of hexosamine (glucosamine/galactosamine) and uronic acid (glucuroninc acid)
what is the largest and most unique GAG
hyaluronan (hyaluronic acid) - forms dense network of polymers that readily bind water
what are proteoglycans?
core proteins to which straight chain GAGs attach
what makes up a proteoglycan aggregate in the ECM?
hyaluronan molecule with core proteins attached that have GAGs (glycoslylated) on them (unit called proteoglycans)
what is a glycoprotein
large protein with short branched oligosaccharide chains, they have multiple binding sites for cell surface receptors and ECM fibers, and play important role in embryonic development and cancer metastasis
exampled of glycoproteins
fibronectin laminin
what does fibronectin do
mediates cell adhesion to collagen and GAGs in the ECM
what does laminin do
is a basal lamina component that mediates epithelial cell adhesion
difference between fibronectin and laminin in a stained cell
fibronectin is found everywhere and diffuses through ECM laminin is restricted in location - in basal lamina
what is interstitial fluid
derived from blood plasma, dissolved components into/out of capillaries + fluid in surrounding connective tissue
how does edema occur?
capillaries become more permeable during inflammatory reactions, excess ISF accumulates
where are mesenchymal cells found
throughout embryo, umbilical cord (wharton’s jelly), and pulp of developing teeth – contain stem cells/progenitor cells for adult connective tissue cells
describe mesenchymal cells
abundant ECM rich in proteoglycans and water small amounts of collagen and reticular fibers have spindle/stellate shaped mesenchymal cells widely spaced
what does wharton’s jelly do
it is mucous tissue that supports and cushions large blood vessels in umbilical cord - made up of mesenchymal cells
describe areolar loose connective tissue
loose network of collagen and elastic fibers, fixed and wandering cells are suspended here, have roughly equal parts of cells, fibers, and ground substance
not very resistant to stress, is well vascularized
describe dense connective tissue
type I collagen fibers dominate, less abundant ground substance and fewer cells, NOT WELL VASCULARIZED, arranged in pattern(regular) or woven into “irregular”
predominant cells in dense connective tissue
fibroblasts
compare aerolar/loose connective tissue and dense connective tissue
loose connective tissue is well vascularized, is flexible but not resistant to stress
dense connective tissue is not well vascularized, less flexible, but more resistant and protective
what does dense regular connective tissue look like stained
collagen is packed into parallel bundles
condensed, flattened fibroblast nuclei between fibers (cytoplasm is not distinguishable)
importance of tensile strength in dense regular connective tissue
transmits force of muscle contraction, attaches bones and protects organs
where is dense regular connective tissue found
tendons, ligaments, aponeuroses, periosteum, perichondrium, deep fascia, some organ capsules
where is areolar connective tissue found
under epithelial tissue, srrounds most blood vessels and nerves, part of mucous membrane, packaging organs, around capillaries
where is adipose tissue found
under skin, around kidneys and eyeballs, within abdomen, in breasts, fills and pads space
where is dense irregular connective tissue found
covers fragile tissue and organs, reticular layer of dermis of skin, submucosa of digestive tract, fibrous capsules of organs and joints
where is reticular connective tissue found
lymphoid organs like nodes, bone marrow and spleen
main difference between dense regular and dense irregular connective tissue?
irregular’s woven pattern of collagen bundles resists tensile stress from any direction
regular’s pattern helps tensile stress from one direction only
how are elastic connective tissues arranged
contains mostly elastic fibers arranged in thick wavy parallel bundles, provides flexible support
where are elastic connective tissues found
walls of large elastic arteries (aorta), vertebral column’s ligamenta flava, penile suspensory ligaments
