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collagen type 1
most common; widespread distribution, "classic collagen"
collagen type 2
found in hyaline, elastic cartilage and fibrocartilage (intervertebral disks)
collagen type 3
assoc w/ type 1; "reticular fibers"; structural scaffolding of lymphoid tissues and bone marrow
collage type 4
What is connective tissue derived from?
- splanchnic mesoderm (walls of GI tract)
- somatic mesoderm (body walls)
What is the pathway of collagen formation?
preprocollagen (rER)--->procollagen (w/in rER)--->tropocollagen/collagen (outside cell via protease)--->collagen fibrils (outside cell)--->collagen fibers (in ECM)
What is CT comprised of?
collagen and proteoglycans
What are proteoglycans made of?
glycosaminoglycans (GAGs) and a protein core
What (primarily) makes GAGs and collagen?
How do GAGs make a hydrated gel?
GAGs have lots of negative charges and attract Na+ which allows water to follow...hydrated gel
What is the function of the hydrated gel of GAGs?
rapid diffusion of water soluble molecules through ground substance and slowing the passage of lg molecules and bacteria
What can synthesize collagen?
fibroblasts/fibrocytes, sm muscle cells, chrondroblasts/chondrocytes, osteoblasts/osteocytes
Where else is collagen found besides CT?
reticular layer of basement membrane
Where are reticular fibers synthesized?
fibroblasts/cytes in LCT and reticular cells in lymphoid tissues and in bone marrow
What are the functions of reticular fibers?
supportive lattices in LCT near epithelium and adipose tissue; hematopoietic and lymphoid tissues
What is the composition of elastic fibers?
elastin protein and fibrillin (glycoprotein)
What makes elastic fibers?
smooth muscle cells, fibroblasts/cytes, chondroblasts/cytes
What are some physical characteristics of elastic fibers?
not easily seen w/ reg staining; highly pliable and elastic
What happens if connective tissue is damaged?
fibrocytes--->fibroblasts repair damage--->fibrocytes (same for chondrocytes/blasts and osteocytes/blasts)
What are the differences btw fibrocytes/blasts
- fibroblast: LCT and CT undergoing repair
- fibrocytes: dense CT
- both synth and secrete all major components of ECM
- DIFF: activity level
What is the job of a reticular cell?
prod reticular fibers in hematopoietic and lymphoid tissues; phagocytize antigenic mat and cellular debris; collect Ag on surface--->activate immunocompetent cells
What usually lives with reticular cells?
lymphocytes, macrophages, FDC
dense connective tissue
fewer cells; thick matrix
dense irregular connective tissue
dense matrix is non directional
dense regular connective tissue
dense matrix is directional (i.e. tendons and ligaments)
- adipose tissue
- cartilage and bone
- lymphatic tissue
What are the functions of adipose tissue?
store energy in the form of stored lipids; cushions and insulates body
What is characteristic of white adipose?
What is characteristic of brown adipose?
What is subcutaneous fat?
- beneath skin
- comprises "panniculus adiposus"
- can be thicker or thinner depending on person
What is intra-abdominal fat?
in variable amts surrounding blood/lymphatic vessels in omentum and mesenteries
located in retroperitoneal areas
What is adipose tissue responsible for making?
What are some characteristics of LCT?
- made of fibroblasts
- support vascular channels supplying other basic tissues
What cells live in LCT?
- mast cell
- plasma cell
- *do not originate in LCT but migrate there once mature
- derived from bone marrow precursors
- abundant basophilic granules in cytoplasm: heparin and histamine
- from circulating monocytes
- phagocytic once active
- several can fuse to become a multinucleated cell
- lg, irregular, lg pale staining nuc
- primary source of sec Ab
- abundant in areas susceptible to invasion (GI tract)
- lg, ovoid, eccentric nuc, abundant rER (bc sec Ab)
- present in variable numbers around body
- sm, round cell w/ dk round nuc
- migratory, phagocytic, short-lived
- multilobed nuc
- abundant cytoplasmic lysosomes
- bilobed nuc
- bright-red cytoplasmic granules