Prac 3 IMMS - Connective Tissue Flashcards
Origin of connective tissue
Derived from MESENCHYMAL CELLS
and from haematopoetic stem cell line
3 constituents of connective tissue
Cells
Ground Substance
Visible Fibres
Example of connective tissue cells
- Fibroblasts
- Adipose
Example of connective tissue Ground substance
- Proteoglycans
- Glycosaminoglycans
Example of connective tissue Visible fibres
collagen
elastic
reticulin
3 types of connective tissue
Fibrous
hard
fatty
Fibrous tissue types
loose
dense
e.g of hard connective tissue
Bone
Cartilage
Types of fatty connective tissue
white
brown
Collagen structure
Fibroblasts which secrete tropocollagen sub-units
- tropocollagen - triples helix of peptides
Individual collagen fibrils consists of overlapping linear strands of tropocollagen
-Each tropocollagen subunit consists of three linear polypeptide chains, (usually two similar and one dis-similar chains) wound together in an alpha helix.
How are collagen fibres assembles
EXTRACELLULARY
Type 1 collagen found
skin
Type 3 collagen?
RETICULIN Provides scaffold for organs eg liver bone marrow spleen
Collagen with H&E?
Stain Pink
Whats the difference between muscle fibres and collagen fibres
Collagen = EXTRACELLULAR
Muscle fibres = INTRACELLULAR
Describe loose connective tissue
Widely spread thin collagen fibres and fibroblasts
with unstained ground substance inbetween
Describe dense connective tissue
Closely packed thick fibres with intervening nuclei of the fibroblasts that have produced them
less abundant unstained ground substance
Describe dense connective tissue
Closely packed thick fibres with intervening nuclei of the fibroblasts that have produced them
less abundant unstained ground substance
Example of regular and irregular connective tissue
Regular - tendons
irregular - penil fascia
Purpose of the Fibroblast
Synthesis of extracellular matrix, also can synthesize several different extracellular constituents depending on its environment and mode of stimulation.
Soft connective tissue
flexible and gel-like, present in most tissues interspersed between the major tissue elements, divisible into fibrous or fatty connective tissue.
Hard connective tissue:
various forms of cartilage and bone.
Fibrous connective tissue
containing large numbers of fibres such as collagen, elastic or reticulin. Described as loose irregular if it contains few visible fibres that are randomly orientated or dense irregular if it contains large numbers of fibres with relatively little intervening amorphous matrix. Dense regular connective tissue contains large numbers of fibres that are all arranged in long parallel bundles.
Fatty connective tissue
containing mainly fat cells with intervening blood vessels particularly capillaries.
Structure of Elastic tissue
consists of microfibres of fibrillin set in an amorphous matrix of elastin. It forms fine fibres or flat sheets.
How can elastin be distinguished if they both look so similar with H&E
They may stain more strongly than collagen and sometimes produce a glassy birefringent appearance.
Where is elastin found?
It is present in most connective tissues and in the walls of blood vessels.
How are the walls of the arterys near the heart different from other arteries?
the wall of most arteries contains a large amount of smooth muscle but in those close to the heart the muscle is replaced by concentric sheets of elastic tissue.
What stain used to distinguish elastic fibres?
Van Gieson - Appear dark brown
How is the thick medial layer in the wall of the carotid artery different to wall in muscular arteries
The thick medial layer contains many concentric layers (sheets) of elastic tissue that stain brown. This elastic tissue replaces the smooth muscle found in this layer in muscular arteries.
Which is more abundant. white or brown adipose
White fat is far more abundant.
Structure and purpose of white fatty cells
It consists of large cells each with a single fat droplet. These cells are used to protect the vital organs and also serve as energy stores.
Why does fatty connective tissue display a rich network of fine blood vessels.
Fat is usually deposited alongside capillaries
When is brown fat abundant?
Brown fat is abundant in the new-born but has a limited distribution around the body in later life.
Why is brown fat refered to as multi-locular
the cells contain numerous separate droplets of fat rather than one single one.
How are cells embedded in cartilage
the cells are embedded in a dense glycosaminoglycan rich matrix containing variable amounts of collagen and elastic tissue. This is flexible, compressible and hardwearing.
How is cartilage formed
formed initially by chondroblasts . These eventually become trapped within the matrix and mature into chondrocytes. The trapped cells are unable to migrate through the matrix.
cartilage is formed initially by chondroblasts that differentiate from precursor cells in the perichondrium. Once the cells become trapped in the matrix they become quiescent chondrocytes.
What is the perichondrium and whats its purpose
Cartilage is surrounded by a fibrous capsule (collagen), known as the perichondrium.
This capsule contains undifferentiated progenitor cells capable of differentiating into chondroblasts should the need arise.
What are the 3 forms of cartilage
hyaline,
elastic and
fibrous cartilage
Hyaline cartilage
In hyaline cartilage the GAG-rich matrix contains fine fibrils of collagen and elastic which can not be resolved with a light microscope but confer a glassy appearance on the matrix. Hyaline cartilage normally stains poorly with the H&E stain.
Articular surfaces, the supporting ‘rings’ of the trachea and the cartilages of the larynx are all examples of hyaline cartilage. Also, all long bones of the body are formed initially from hyaline cartilage which is subsequently replaced by bone by the process of endochondral ossification
Elastic cartilage
irregularly arranged fibres of elastic can be seen in the matrix. The epiglottis and the pinna of the ear both contain this form of cartilage. As the name suggests this form of cartilage has increased elasticity
Fibrous cartilage
In this the matrix is filled with collagen which can be seen often as distinct bands. Inter-vertebral discs are largely composed of this form of cartilage.
Describe fibrous cartilage in vertebrae
discs have a thick fibrous outer shell with a more fluid centre. Chrondrocytes are distributed throughout both phases although the ‘texture’ of the matrix varies.
In the outer casing strong bands of collagen fibres are evident while at the centre the collagen is more evenly dispersed.
Where is skeletal muscle found?
ound mainly attached to the bony skeleton and responsible for its stability and movement.
Where is smooth muscle found?
found in many internal organs and in blood vessels.
Other groups of contractile cells …
There are also a group of other cells with contractile properties including pericytes, that lie alongside some small blood vessels, myofibroblasts, that are involved in scar formation and myoepithelial cells whose role is to assist with the expression of milk during lactation.
Structure of smooth muscle
consists of discrete cells couple together by cell junctions so that they function as a whole.
How does smooth muscle appear in longitudinal and transverse sections
When cut longitudinally the cells appear elongated with tapered ends (fusiform) and their nuclei appear cylindrical.
When sectioned transversely both the cells and their nuclei appear round.
How are contractile proteins organised in smooth muscle
The contractile proteins within smooth muscle cells are not organised into regularly repeating sarcomeres (as in skeletal muscle) but are anchored focally (in clumps) to the inside of the cell membrane.
How are smooth muscle cells joined together?
Smooth muscle cells secrete a reticulin rich external lamina (basement membrane) that joins the cells together.
The cells are joined by gap junctions (electrically coupled) that permit a stimulus to pass rapidly through the muscle,.
They also have a number of surface receptors which allows them to respond to a variety of hormonal stimuli.
What type of junctions joins smooth muscle cells together?
Gap junctions
Structure of the gap junction which joins smooth muscle cells together
Each junction consist of a complex of 6 connexon proteins that span the cell membranes linking the interiors of adjacent muscle cells.
How do gap junctions work?
The guarded central pore in the connexon complex permits small molecular weight molecules (signal molecules) to pass from one cell to the next in the chain, electrically coupling them and allowing the contraction stimulus to pass from one cell to the next without the need to be transported across the cell membranes (quicker!).
Eg. of invisible fibres
Laminin
Fibronectin
Example of cells derived from mesenchymal cells
Fibroblasts
Osteoblasts
Chondroblasts
Example of cells derived from heamatopoetic stem cells
Monocytes
Purpose of white adipose tissue
Shock absorber
Energy storage
Insulation
Purpose of brown adipose tissue
Generates heat
ESP. In babies bc high SA:V ratio
Ligament
Connect bone to bone
Tendon
Connect muscle to bone
