Lecture 8 - Connective Tissue Flashcards
Connective Tissue made of
ECM (ground substance, fibers, structural glycoproteins) and and cells
Functions
Structural Support; Site of Exchange of nutrients/waste between tissues; defense/protection from foreign bodies; storage of fat
Ground substance
glycosaminoglycans (GAG, long carb chains), proteoglycans (many gag chains attached to protein core, mostly carbohydrate in composition). V. negative so retains lots of salt and water
Types of GAGs
Hyaluronic acid –> not sulfated or bound to protein, so not negative so proteoglycans bound to them. The other gags fill the space between the proteoglycan bound; keratin sulfate (skin); heparan sulfate (basement membrane, stain positive PAS); dermatan sulfate (skin); chondroitin sulfate (cartilage)
Three types of connective tissue
Collagen fiber, reticular fiber, elastic fiber
Type I collagen
tendon, ligaments, bone, fibrous cartilage, dermis of skin; forms fibrils
Type II collagen
Hyaline cartilage, elastic cartilage; forms fibrils
Type III collagen
Also called reticular fibers, thinner than type I/II; lymphoid organs, muscle cells, blood vessels, liver, endocrine glands, lung, kidney; forms fibrils
Type IV collagen
Basement membrane (found around epithelium, endothelium, muscle, nerve axons); forms mesh like structure
Properties shared by Types I-III
Mechanical support, gives tensile strength to tissue, resistance to stretching when pulled
Fibril under EM
Can see alternating dark and white bands at 64 nm periodicity, specific to collagen
fibril vs. fiber
Many fibrils make up one fiber
Silver stain
Stains Type III collagen black
Type IV collagen
basement membrane (heparan sulfate), mesh like structure, so do not see banding. PAS positive
Elastic fiber components
Elastin (desmosine and isodesmosine) and microfibrils (fibrillin)
Structure of elastic fibers
Thin branched forming irregular networks in connective tissue
Properties of elastic fibers
Stretchable as rubber bc of desmoseine and isodesmoseine; elastic recoil
Cells that make elastic fibers
Fibroblasts in CT, smooth muscle cells, chondroblasts and chondrocytes found in elastic cartilage
Classification of connective tissue
- Loose connective
2. Dense connective tissue –> two types, regular and irregular
specialized types of CT
Reticular Tissue; Elastic Tissue; Adipose Tissue
Embryonic CT
Mesenchyme; Mucous
Loose CT, what and where
More Cells than collagen fibers, seen in most tissues and organs,
Largely type III collagen/lining of mucous membranes called lamina propria
Dense Irregular CT
More collagen fibers than cells, irregularly arranged.
Largely types I and III, some elastic fibers
Dermis
Dense regular CT
Parallel bundles of collagen fibers, separated by linear rows of fibroblasts
Type I collagen
Tendon and ligaments
Reticular Tissue
Loose network Type III
Forms suportive tissue for tissue/organs, seen in lymphatic tissue
Elastic Tissue
Seen in wall of aorta, elastic ligaments
Stained by resorcin fuschin stain
Types of adipose tissue and functions
White –> All over body; for thermal insulation, storage of energy, visceral fats correlated to obesity
Yellow –> Bone marrow
Mesenchyme CT
Embryonic
Stellate/spindle shaped, delicate branching of mesenchymal cells, surrounded by ground substance
Unspecialized, can differentiate into all CT types
Mucous CT
Umbilical cord, also called whatron’s jelly
Cell Types of CT
Fibroblasts, mast cells, macrophages, plasma cells, lymphocytes, neutrophils, eosinophils, adipocytes
Fibroblasts
Splindle shaped, nuclei and cytoplasm elongated Cytoplasm slightly basophilic --> RER Produces ECM (collagens, elastic fibers, ground substance)
Mast Cells
Single round dark purple nucleus, strongly acidophilic cytoplasm Finely granular (seen in EM) Have IfE receptors that bind antibodies, trigger allergic rxns
Where are Macrophages found
Found in CT, lungs, lymphoid organs and bone marrow. Some types are tissue specific (ex. microglia in CNS)
Monocytes
pre-cursor to macrophages, develop in bone marrow, circulate in the blood. After leaving blood for CT, diff. into macrophages
Macrophages unique properties
Lysosomes, which contain acid phosphotase (stain red under azo dye)
Phagocytosis
secrete cytokines which are signals to other immune cells
present antigens on cell surface to T-cells
Where are lymphocytes found
Develop in bone marrow; two types (T & B); leave circulation for CT, live 2-3 years
Plasma Bodies/Cells
Created from B lymphocytes; Make antibodies; live in loose CT; nucleus off center; depends on RER (protein synthesis) –> slightly basophilic cytoplasm;
Neutrophils
Multilobed nucleus (3-5 lobes); slightly pink cytoplasm; usually in circulation, found in CT in cases of acute infection for 2-3 days. Defunct neutrophils are pus cells
Eosinophil
Bilobed nucleus, strongly pink cytoplasm, seen in parisitic infection and allergic rxn; seen in loose CT in chronic inflammation
