Tissues & Extracellular Matrix Flashcards
Four types of tissue
Nervous, Muscle, Epithelial, Connective
What makes Nervous tissue distinct?
Electrical impulses
What makes muscle tissue distinct?
Contractile capabilities
What are the three functions of epithelial tissue?
- Absorption (nutrients) 2. Secretion (mucus, glands) 3. covering, lining, protecting (tissue)
What does epithelial tissue protect?
Integumentary system, GI tract, respiratory canal etc
True/False: Epithelial tissue is vascular tissue
False
Why is epithelial tissue avascular?
Cells are packed tightly together, leaving no space for blood vessels
What is a basement membrane?
Basal lamina (epithelial cells) + Reticular lamina (connective tissue cells)
How are the cells in lower layers different than other cells in epithelium?
They are usually mitotic - actively dividing and creating new cells to replace those towards the top. However, more mitosis usually leads to a potential for mistakes
What are the two types of epithelial cells?
Membranous (lining & protection) and Glandular (secretion/absorption)
What are the two parts of the basal lamina?
Lamina lucida (looks like empty space) and Lamina densa
What are the functions of connective tissue?
- Binds structures together 2. Provides support, structure, and protection
What are notable characteristics of connective tissue?
- Well vascularized
- Composed of cells & supporting ECM
- Cells are usually spaced far apart, not in direct contact with each other
What is the ECM and what is it comprised of?
Predominantly associated with connective tissue
Comprised of:
- Fibers
- Ground Substance
What are the three types of collagen?
- Fibrillar
- Sheet-forming
- Linking/anchoring
Describe Fibrillar collagen
- Long, thick strands
- Types 1-3 collagen
- Types 1&2 can be seen with a light microscope
Describe sheet-forming collagen
- Interlaced network of ultra-thin strands
- Type IV
- Major structural component of basal lamina
Describe Linking/anchoring collagen
- Short strands - connect fibrillar collagens to each other and to other components within the ECM
- Type VII collagen - anchors reticular lamina to basal lamina
Describe Reticular fibers
- very thin fibers formed predominantly of type III collagen
- main component of reticular lamina
- forms flexible scaffolding within orgains like liver, spleen, lymph nodes, & red bone marrow
- may be found scattered throughout ground substance
Describe elastic fibers
thin fibers primarily made of the protein elastin, overlaid on scaffolding of glycoproteins
Describe the ground substance
- “maple syrup consistancy”
- transparent mixture of macromolecules, widely varying in consistency
What are the three components of ground substance?
- GAGs (glycosaminoglycans)
- Proteoglycans
- Glycoproteins
What are glycosaminoglycans?
long linear polysaccharides
highly hydrophilic
highly viscous
polyanionic (negatively charged, attracting positively charged molecules)
What is the largest and most ubiquitous glycosaminoglycan?
Hyaluronic Acid
(highly hydrophilic, lubricates joints/membranes)
What are the 4 sulfated GAGs?
- Dermatin (epithelial production; skin)
- Chondroitin (cartilage)
- Keratan (hair/skin/nails)
- Heparin (blood)
What are proteoglycans?
Large molecules consisting of numerous sulfated glycosaminoglycans bonded covalently to a large rod-like core protein (aggrecan & syndecan)
What are glycoproteins?
Large, globular proteins covalently bonded to large monosaccharide chains (e.g. fibronectin; laminin)
How does the ground substance hold/support fibers and cells?
- Linkages between cell-surface protein molecules & GAGs and/or glycoproteins anchor the cell in place
- GAGs & glycoproteins bind to the fibers, anchoring them & connecting them to cells/each other
- laminins bind underside of epithelial cells to fibers, creating basal lamina
What are additional functions of the ground substance?
- Passes nutrients from blood supply to cells
- Passes waste from cells to blood supply via diffusion
- Facilitates/regulates cell to cell communication in ECM
What is interstitial/extracellular fluid?
Fluid in connective tissue that is not bound up by large molecules of ground substance
What is interstitial fluid derived from?
Blood plasma via diffusion/filtration
*Much lower concentration of blood proteins because most proteins are too large to cross the vessel wall
