Lec 2 Connective tissue Flashcards
How is CT different from Epi
CT is mostly matrix (cell products) and has fewer cells
The matrix mostly determine the properties and functions of the CT
What is Matrix composed of
Protein fibres and ground substance
Organic protein fibres part of the GS is produced by CT cells
What are the 3 kinds of CT and the cells associated with them
CT proper - FIbrocytes, Cartilage - Chondrocytes, Bone - osteocytes
What is the order of CT, matrix, proteins…
CT - Cells and Matrix
Matrix - Proteiid substance
Fibers - collagen and elastic fibres
Ground substance - tissue fluid, organic molecules
Organic molecules - proteoglycans, adhesive glycoproteins
Collagen characteristics
Flexible, inelastic, provide tensile strength
What is the multistep process for fibrillarcollagen synthesis
Preprocollagen -> Procollagen -> Collagen (A TRIMER: 2 alpha, 1 Beta) -> Fibrils -> Fibres -> Bundles -> Tendon
Collagen biosynthesis: what occurs inside the RER
Synthesis of alpha chains of preprocollagen
Then its modified and cleaved into procollagen triple helix with registration peptides on the ends
What does registration peptides do
Maintains solubility of the procollagen such that it wont self assemble intracellularly
When is the registration peptides cleaved
After procollagen is transported to the golgi for post-trans mods and packaged
Vesicles carry the procollagen to the cell surface to be exocytosed.
During exocytosis, membrane bound procollagen peptidases cleave the registration peptides
Why do collagen fibrils have a banded look
There are gaps regions that line up in the fibril, heavy metals accumulate in there
What are type 1,2,3,4,7 collagen fibres
Type 1: CT proper (tendon and ligaments) and bone - most common
Type 2: Cartilages - dont get past the fibrillar form
Type 3: reticular fibres
Type 4: BM mesh - dont get the registration peptides cleaved so it forms a mesh sheet associated with the BM
Type 7: Anchoring fibrils - Binds to the BM underlying type 1 and 3 collagen
What is collagen type 3
How important?
Collagen type 3 are reticular fibres
Forms a scaffold - helps cells organize themselves
Scaffolding is called STROMA in organ cells to form their parenchyma - Eg: hepatocytes organize themselves around reticular fibres
Elastic fiber properties
What does it need to form fibers
Stretch and recoil
composed of elastin embedded in microfibrils made of fibrillin.
What is the role of ground substance
GS mediates the diffusion of molecules between plasma and ICF
Provides adhesion for tissue components
GS resists compression as GS binds water, and fibers will withstand tensile forces
Where is the lowest hydrostatic pressure found
Lowest pressures in the lymphatic vessels
- excess interstitial fluid becomes lymph
Where does lymph drain from and where do they go
Lymph drain away from CT in lymphatic vessels
Lymphatic vessels drain into lymph nodes to be filtered, protect from disease
Drains back into vein in the neck
What can edema be the result from
Increased production of tissue fluid: form incr vascular perm (damage) and decr oncotic pressure ( less plasma protein)
Decr clearance of tissue fluid: from increased venous pressure
Lymphatic obstruction - filariasis(elephantitis)
What are GS proteoglycans responsible for
gel-like matrix, ability for CT to resist compression, molecular filter(charge distribution), slow diffusion of cells n pathogens n stuff
What are proteoglycans composed of
GAG - glycosaminoglycans and a core protein (rod shape)
What are properties of GAGs (3)
- Inflexible unbranched polysaccharides made of disaccharide subunits
- Has high negative charge (can attract Na) thus it is very hydrophillic PLUS proteoglycans will repel each other - All resulting in a slippery texture to the GS
- Chemistry of GAG is specific to tissue types
What is adhesive glycoproteins made of and its role in GS
They are proteins with bound carbohydrates (Fibro, osteo, chondro - nectins and laminin).
They are binding sites for protein fibers, GAGs, and integrins of the cell membrane.
Stabilizes the ECM, links parts to cell surface
MORE BM INFO
Also surround smooth muscle, schwann and at cells to sep from CT
Has type 4, 7 collagen fibres
Has heparin sulfate proteoglycans
Has laminin containing adhesive glycoprotein
What is broad types of cells are normally found in normal CT / CT proper
Fixed cells - function locally
Wandering cells - increases with tissue dmg or infection
What are specific fixed cells found in the CT proper
- Fibroblasts: Prod fibers - organic part
- Fixed macrophages - phagocytic protects tissue
- Adipocytes: lipids for nrg, insulation and physical protection
- Mast cells: mediating inflammation, release his
- Mesenchymal cells: stem cells
What are specific wandering cells in the CT proper
- Monocytes: respond to chemotactic sigs - becomes macrophages
- Lymphocytes: with antigen exposure, become antibody prod plasma cells
- Microphages: Neutrophils and eosinophils, responds to chemotactic sigs
When does WBC/leukocytes function
Carried in blood, FUNCTIONS in CT
What are classifications of the CT
CT proper:
Loose: Areolar
Dense: Regular, irregular, elastic
Specialized CT proper: Reticular, Adipose
Supporting CT:
Cartilage: Hyaline, Elastic, Fibrocartilage
Bone
What are the advantages of Loose areolar CT
What is it composed of (cells n acellular stuffs)
Where can it be found and why
Least specialized CT: has all cell and fibre types
- Gives support while allowing independent movement
Is mostly GS in volume, BUT cellular relative to other CT
Between muscles, BVs, joints and as LAMINA PROPIA in digestive epi
Food antigens passing epi go into the loose areolar CT filled with WBCs - protect against disease/pathogens
What is DENSE REGULAR CT made of.
What does it FUNCTION to do
What is its cell composition look like
Where found
Made of mostly collagen type 1 fibres in PARALLEL arrays
Gives tensile strength in ONE direction
Relatively little GS, not a lot of cells and cell types
Dense meaning its mostly fibres and fibrocytes
They are in TENDONS, LIGAMENTS and APONEUROSES (forms sheets)
What is DENSE IRREGULAR CT made of
What does it function to do
What is its cell composition look like
Where found
Mostly type 1 collagen fibres arranged in a mesh sheet
- in longitudinal and cross sectional directions
Resists tensional forces in multiple directions
Little GS, relatively fewer cells and cell types, MOSTLY FIBROBLASTS and its fibers
Found in SKIN, as PERIOSTEUM, PERICHONDRIUM, Joints and Organ capsules and submucosa of GI
What is ELASTIC tissue made of
What does it function to do
What is its cell composition look like
Where found
Made of elastin molecules with fibrillin microfibre scaffolding - Makes elastin fibres
Funcs to increase tissue resiliency, stretches under pressure and recoil
Found with collagen fibres with loose areolar CT and dense CT as elastic ligaments
WITHOUT fibrillin, elastin forms fenestrated sheets/elastic lamellae - in AORTA(stretch when filling for systole)
What is specialized CT proper - RETICULAR CT made of (Fibres)
What does it function to do
What is its cell composition look like
Where found
Mostly type 3 collagen fibres (delicate reticular fibres)
Organizes cells in certain ways
Forms the stroma (scaffold) for highly cellular organs to arrange their parenchyma (functional cells)
Abundant in liver, kidney, spleen, lymph node, smooth muscle and bone
What is specialized CT proper - ADIPOSE composed of
What does it function to do
Where found
Mostly adipocytes, very vascular, in a reticular fibre network (organizes the adipocytes)
Store triglycerides as large lipid droplet
FUNCS as nrg depot, thermal insulator and shock absorber
Found with areolar CT
Abundant deep in skin, back of eyes, around kidneys
