connective tissue Flashcards
components of connective tissue
- cells
- extracellular matrix
- protein fibers:
collagen
reticular
elastic
- ground substance
classification of connective tissue
- Embryonic Connective Tissue
○ Mesenchyme
○ Mucous connective tissue - Connective Tissue Proper
○ Loose connective tissue
○ Dense connective tissue - Specialized Connective Tissue
○ Cartilage
○ Bone
○ Adipose Tissue
○ Blood
○ Hematopoietic tissue
○ Lymphatic Tissue
Which germ layer does hematopoietic tissue come from?
Mesoderm (the middle germ layer).
- hematopoietic tissue can be found in embryo and umbilical cord
The primitive connective tissue primarily found in the embryo
mesenchyme
- small, spindle-shaped cells
- extracellular space: viscous ground substance tht contains collagen and reticular fibers
this tissue is present in the umbilical cord.
mucous CT
- consists of gelatin-like ECM:
hyaluronic acid
ground substance (Wharton Jelly)
contains mesenchymal stem cells, which also has the capability to
differentiate into different types of cells
wharton jelly
- chondrocytes
- adipocytes
- osteocytes
loose connective tissue
- aka areolar tissue
- thin, sparsed collagen finbers and ground substance
(GS: helps moe nutrients and oxygen from BV to tissue)
found in lamina propria and papillary layer of the skin - first defense whr the immune system fights infections
dense irregular connective tissue
- v little ground substance and mostly collagen fibers (diff directions = strong and resistant to stretching)
- protect organs by providing strength and flexibility
- found in:
reticular layers of the cell
submucosa of the hollow organs
dense regular connective tissue
- v little ground substance and mostly collagen fibers in parallel directions
- strong flexible support = withstand pulling forces
- main components:
tendons (muscles to bones)
ligaments (bone to bone) *more elastic fibers
aponeuroses (wide, flat tendons) *CF in 90degree angle for extra strength
Most abundant structural components of connective tissue, characterized by their flexibility and high tensile strength.
collagen fibers
- have the strength of 1000 steel
large to small:
collagen fibers
collagen fibrils
collagen molecule
it is a right-handed triple helix composed of three intertwined polypeptide chains.
collagen molecule
- the classes of collage fibers based on their polymerization pattern
1. fibrillar collagens
2. fibril-associated collagens w interrupted triple helices (FACITs)
3. hexagonal network- forming C
4. transmembrane C
5. multiplexin C
6. basement membrane- forming C
biosynthesis and degradation of collagen fibers
BIOSYNTHESIS:
Collagen production follows the central dogma (DNA → RNA → Protein).
Process:
1. Preprocollagen → First form, directly from gene expression (freshest type).
2. Procollagen → Modified form, undergoes enzymatic processing to mature.
3. Collagen Molecules → Fully matured and start self-assembling.
4. Collagen Fibrils → Multiple collagen molecules come together (fibrillogenesis).
5. Collagen Fibers → Fibrils group into larger, stronger structures.
DEGRADATION:
. Proteolytic Degradation (outside the cells)
Special enzymes called Matrix Metalloproteinases (MMPs) break down collagen in the extracellular matrix.
2. Phagocytic Degradation (inside the cells)
Macrophages (immune cells) engulf and digest damaged collagen pieces inside the cell.
Provide a supporting framework for the cellular constituents of various tissues and organs
- found in
- composed of
-produced by - function
reticular fibers
- thin and branching
- do not form thick bundles
[Acts like a supporting net for cells in different tissues and organs.]
found in:
Lymphatic system (e.g., lymph nodes)
Bone marrow (where blood cells are made)
Hematopoietic tissues (blood-forming tissues)
composed of type Ill collagen.
produced by: reticular cells
function:
support in blood-forming
immune system tissues
how to see reticular fibers in a microscope
Special stains are needed
- PAS stain
- Gomori stain
- Mallory stain
- Wilder stain
- normal stains, H&E does not work
elastic fibers
- function
- structure
- made of
- key protein involved
- found in
function:
stretch and return to original shape
structure:
thinner than collagen fibers
form branching network
more elastic than collagen fiber
made of:
Elastin → Main stretchy protein. (rich in proline and glycine but poor in hydroproline and lacks hydroxylysine)
Fibrillin microfibrils → Act as a scaffold for elastin to form elastic fibers.
Special amino acids (Desmosine & Isodesmosine) → Help elastin stick together.
key protein involved:
Fibrillin-1 → Forms a structure for elastin to wrap around.
EMILIN-1 & MAGP-1 → Help control elastic fiber formation (Elastogenesis).
why are the elastic fibers stretchy
rich in nonpolar (hydrophilic) amino acids like proline and glycine
how to see elastic fibers in a microscope
Need special stains:
Weigert elastic stain (purple-violet)
Gomori aldehyde fuchsin stain (blue-black)
Verhoeff hematoxylin stain (black)
Modified Taenzer-Unna orcein stain (red-brown)
process of formation of elastic fibers
elastogenesis
it surrounds the fibrillin microfibrils
elastin
elastin material in…
ligaments:
thick elastic fibers
arteries: fenestrated lamellae
Caused by a deficit or abnormality in the production of specific collagens.
Collagenopathies
- most are attributed to mutations in genes encoding the a-chains
[are genetic disorders that affect connective tissues, making them weak or dysfunctional]
type of collage and its diseases
transes
A complex and intricate structural network that surrounds and supports cells within the connective tissue.
extracellular matrix
contains:
collagen
protein fibers
ground subs
- proteoglycans
- multiadhesive glycoproteins
- glycosaminoglycans , GAG
The most abundant heteropolysaccharide components of the ground substance.
GAGs glycosaminoglycans
- highly negative charges = attracts h20, due to their polarity
Always present in the extracellular matrix as a free, long (-1000) carbohydrate chain.
Hyaluronan
- not covalently bound to protein
- forms proteoglycans aggregate (able to resist compression w/o inhibiting flexibility)
Composed of GAGs covalently attached to core proteins.
proteoglycans
- found in ground subs in all CT and membrane-bound molecules
- receptors to specific extracellular protein
Major component of cartilage
aggrecan
- its struck-absorbing
properties
- composed mainly of:
proteoglycan and indirectly bound hyaluronan
- resist compression w/o inhibiting flexibility and excellent shock absorbers
Unique as it can be found in the
lymphocytes and present during early development of lymphocytes
Syndecan-1
- helps anchor lymphocyes to bone marrow
- found in plasma cells (help bind to ECM)
Syndecan-1 and Lymphocyte Maturation
🔸 Early stage: High Syndecan-1 → Lymphocytes stay in bone marrow
🔸 Mature stage: Low Syndecan-1 → Lymphocytes enter bloodstream
Play an important role in stabilizing the ECM and linking it to cell surfaces and has a multifunctional molecules of different shapes, and possess multiple binding sites for a variety of ECM proteins.
Multiadhesive Glycoproteins
- serves as a receptors for certain proteins
resident cells vs wandering cell population
★ Resident cells
○ Fibroblasts
○ Macrophages
○ Adipocytes
○ Mast cells
○ Adult stem cells
★ Wandering cell population
○ Lymphocytes
○ Plasma cells
○ Neutrophils
○ Eosinophils
○ Basophils
○ Monocytes
Principal cell of connective tissue, and are responsible for the synthesis of collagen, elastic, and reticular bers and the complex carbohydrates of the ground substance.
fibroblasts
Displays properties of both fibroblasts and smooth muscle
cells.
myofibroblasts
- presence of bundles of actin laments with associated actin motor proteins
A type of actin found in vascular smooth muscles and myofibroblasts, helping them contract.
alpha-smooth muscle actin
How do myofibroblasts contribute to tissue repair?: How do myofibroblasts contribute to tissue repair?
They pull the edges of a wound together and strengthen the tissue by transmitting forces through actin filaments.
A system where forces generated by actin filaments are transmitted to the extracellular matrix, aiding in contraction and tissue repair.
mechanotransduction system in myofibroblasts
difference between fibroblast and myofibroblasts
Fibroblasts = “Construction workers” 🏗️ → They build the materials that form connective tissue.
Myofibroblasts = “Tissue tighteners” 💪🏽 → They contract to pull wounds together and help healing.
Process lf formation of elastic fibers
Elastogenesis
Surrounds fibrils in micro fibrils
Elastin
Caused by a deficit in the production of specific collagens
Collagenopathies
The most abundant heteropolysaccaride components of the ground substance
GAGs
Glycosaminoglycans
- highly negative charge
- attracts water due to high polarity
Always present in the ecm as a free matrix, long (-1000) carbohydrate chain
Hyaluronan
Forms proteoglycans aggregates, which asap count for their ability to resist compression without inhibit g flexibility
Hyaluronan
[withstand pressure (resist compression) while still staying flexible]
Composed of GAGs covalently attached to core proteins
Proteoglycans
Major component of cartilage
Aggrecan
(Composed mainly of proteoglycan and indirectly bound hyaluronan)
Its presence correlates with the early development stage of lymphocytes
Syndecan-1
In the early stage of development, they are anchored to bone marrow.
Once matured,release to the blood
Can be found in the plasma cells
Multifunctional molecules of different shapes, and possess multiple binding sites for a variety of ECM proteins.
Multiadhesive glycoproteins
Displays both properties of both fibroblast and smooth muscle cells
Mayofibroblasts
