Connective Tissue Flashcards
What are the four basic categories of cell in the body
Connective tissue
Nerve tissue
Muscle tissue
Epithelial tissue
Supporting tissue is derived from which embryonic layer
Mesoderm
What are connected tissue cells responsible for
The synthesis and maintenance of extracellular matrix
What are the four types of connective tissue cells
Fibroblast
Adipocyte
Chondroblast and chondrocyte
Osteoblast and osteocyte
What is the most common connective-tissue cell
Fibroblast
What does a fibroblast look like and light microscopy
an elongated nucleus is usually the only visible structure
It can be difficult to distinguish other components due to the thickness of the cell and its fusiform shape tapering towards both ends
What do you electron micrographs of mature fibroblasts look like
They show an elongated cell with a prominent nucleus and a scanty cytoplasm rich in rough ER
Fibroblasts have a cytoplasm rich in rough ER. What does this reflect about the fibroblast’s role
It has a role in protein synthesis and secretion
When activated what do fibroblasts give rise to in muscle
Myofibroblasts which have contractile function and play a role in tissue repair, defence and immunity
What are the rules of white adipocytes
Energy storage
Protective cushioning
Thermal insulation
How do you white adipocytes store fat
As a single lipid droplets occupies most of the cell, compressing and displacing the nucleus to one side
What does a white adipocyte look like?
Has a sparse cytoplasm which is peripherally distributed as a thin layer around the lipid droplet
How are white adipocytes distributed
They can be found on their own throughout loose and dense connective tissue or forming a solid tissue with very little intercellular material between them
How do brown adipocytes store fat
What do these cells look like
As numerous lipid droplets
They have a large nucleus, numerous mitochondria whose cytochromes account for the brown colour and are smaller than white adipocytes
Which organisms tend to have lots of brown adipocytes
Neonates and hibernating mammals
They have a key role in heat generation and body temperature regulation in such organisms
What do chondroblasts and chondrocytes do
Secrete and maintain the extracellular matrix of cartilage
What do osteoblasts and osteocytes do
Maintain the extracellular matrix of bone
Describe the extracellular matrix
And organised meshwork of protein and polysaccharide molecules that fill the space between cells
It also participates in the regulation of cell differentiation, growth, shape, proliferation and migration
How is the extracellular matrix synthesised and secreted
By fibroblasts
What are the two components of extracellular matrix
Fibrous proteins e.g. collagen and elastin
Ground substance, a hydrated amorphous polysaccharide gel in which the fibrous proteins are embedded
What is the most abundant protein in the body and what does it provide
Collagen
What is the precursor of collagen
Tropocollagen / procollagen
Where does assembly of tropocollagen into long collagen fibres occur
Extracellularly
How many types of collagen are there and which is the most abundant
There are four types with type one being 90% of the total amount
Where is type II collagen found
It consists of fine fibres embedded in cartilage matrix
Where is Type III collagen found
Skin and round blood vessels
Where is type IV collagen found
It forms a meshwork of fine fibres and is the main component of epithelial basement membranes
How does collagen appear in LM
As an acidophilic mesh
Collagen molecules can only be seen as bundles, If they do not form a bundle they cannot be distinguished from the surrounding ground substance except by immunohistochemistry
Describe the appearance of collagen one fibres under the EM
They have a striations at intervals of 67 mm along the length
This periodicity reflects the staggering of tropocollagen molecules in the fibres
What do elastic fibres consist of
And amorphous glycoprotein called elastin and numerous proteinaceous microfibrils that become embedded in the elastin
What synthesises elastin
It is synthesised in the fibroblasts as a precursor called tropoelastin
What secretes the ground substance of the extracellular matrix
What does the aqueous phase of it allow
It is secreted primarily by fibroblasts and consists mostly of glycosaminoglycan and proteoglycan
The diffusion of salts, nutrients, hormones and metabolites between blood and tissue cells
What are proteoglycans composed of
A core protein to which straight-chain polymers of repeating sugar heterodimers are covalently attached
These sugars differ giving different classes of proteoglycans
They are negatively charged and take on an extended form in tertiary structure
The extracellular matrix contains glycoproteins. What are these?
Proteins to which she also branched oligosaccharide chains are covalently pound
the glycoproteins of ground substance are much smaller than proteoglycans
Give examples of Glycoproteins in ground substance
Laminin (A component of basement membrane is that mediate attachment of epithelial cells)
Fibronectin (A component which promotes cell adhesion)
True or false:
Ground substance is simply there to fill up the space
False
It contributes to the physical properties of the tissue
Ground substances orientate cells during development, control diffusion and are involved in healing and repair
Describe loose connective tissue
The fibres (mostly collagen) are sparse ( 10–20% by volume) and the ground substance fairly fluid, providing ample opportunity for functional cellular growth and differentiation as well as space for considerable transient populations of white blood cells in places such as the gut epithelium
Describe dense connective tissue
In some places, usually wear a polo or an expansion has to be resisted, the proportion of college and increases and a higher density of fibre is found
In places such as tendons and ligaments college and contribution can rise to 90% or more
Describe elastic connective tissue
This shows a preponderance of elastic fibres and is found in the long Alviola sector, skin the wall of the year and your brother on the walls of the arteries
As tissues age the elastic content decreases
Why does skin wrinkle with age
As tissues age the elastic content decreases
What are chondroblasts
Connective tissue cells that produce the cartilage extracellular matrix consisting of connective-tissue fibres (mainly collagen and elastic fibres,) in the various proportions and abundant ground substance rich in proteoglycans
Secretion of the matrix traps the chondrocytes, separating them
What is most cartilage surrounded By
A layer of irregular collagenous connective-tissue called perichondrium
This also contains some inactive fibrocytes
What happens to the inactive fibrocytes in perichondrium
They can become chondroblasts in the inner surface
The Chondroblasts can grow, divide and produce new cartilage matrix
Which are more mature:
chondrocytes or chondroblasts
Chondrocyte are more mature
Where are chondrocytes found
What are they responsible for
They are located within small lacunae
Maintaining the integrity of the extracellular matrix
How do you chondrocytes receive metabolites
Cartilage lacks blood vessels
So chondrocytes depend on metabolite diffusion from the capillaries at the edge through the water of the ground substance
Describe hyaline cartilage
Where is it found
Contains abundant ground substance with scattered fibres to form a thick into cellular material
It is the commonest form of cartilage
In the trachea, nose, larynx , ribs and all articular surfaces
How much of hyaline cartilage is ground substance and what kind of collagen does it to contain
70% ground substance
Type II cartilage
Describe fibrocartilage
Contains abundant type II collagen fibres
This resilient cartilage is formed from alternating layers of hyaline cartilage matrix and layers of dense collagen fibres
Where is fibrocartilage found
In intervertebral discs, where ligaments or tendons connect to bone and in the pubic symphysis
Describe elastic cartilage
Where is it found
Has a structure similar to hyaline cartilage but contains abundant branching elastic fibres and Type II collagen
In the external air and external auditory canal as well as in part of the laryngeal cartilages and in the epiglottis
How does bone differ from cartilage
Mineral salts are deposited in the intercellular material to give increased rigidity
Why is blood considered to be a connective tissue
It originates in the mesoderm and has a matrix
What do you all blood cells arise from
The same pluripotent uncommitted stem cell
What is haematopoiesis?
The process of blood production which is usually carried out in the bone marrow
What do pluripotent stem cells differentiate into
Progenitor cells which differentiate into various types of blood cells
How many litres of red blood cells do we have
2 L
5x10^6 RBC per mm3
How long is the lifespan of a human red blood cell
120 days
What is the shape of a red blood cell
Biconcave
What are reticulocytes
What do they contain
Immature RBCs that are releases from
The bone marrow to the circulation where they mature after 1-2 days
Some rER and small mitochondria
What is the proportion of reticulocytes in human blood
1% of the total number of mature red blood cells
How many blood cells are white blood cells
About one cell in 1000 blood cells is a leucocyte
How are white blood cells classified
According to their appearance in the light microscope, the presence of granules in the cytoplasm and how the granules are covered with Leishmann’s stain
How are white blood cells divided
Into granulocytes and agranulocytes
Name the three granulocytes
Neutrophils
Eosinophils
Basophils
Name the two types of agranulocytes
Lymphocyte
Monocyte
What are thrombocytes
How big are they
Platelets
1-4μm in diameter
Describe a platelet
Non-nucleated, by convex fragments formed in the bone marrow from the cytoplasm of megakaryocytes
They contain the most cytoplasmic organelles of any cell
What consists of ~20% of the platelet volume
Electron dense granules containing serotonin and many proteins
How many platelets are there
150-400x10^3 per μm of normal circulating blood
What is the role of platelets
Haemostasis (control of bleeding)
Plugging sites of vascular damage
Facilitating vascular repair
What are granulocytes generally
White blood cells with cytoplasmic granules that contain substances that participate in inflammatory and allergic responses
Describe a neutrophil
Contains neutrophilic granules that do not stain well
It is best to identify them by the fact that the nucleus is divided into several lobes – the polymorphic nucleus
Neutrophils are the most numerous am on the white blood cells
What percentage of white blood cells are neutrophils
60%
What are eosinophils?
Eosinophilic Granules of relatively uniform size that stain red or orange with acidic dyes
How do the sizes of eosinophils and neutrophils compare
Eosinophils > neutrophils
Describe basophils
Contain course but you do feel like granules that staying with basic dies and pick up azure and stain blue
The granules vary in size and shape and a larger than those of eosinophils
These are the rarest I’m on the white blood cells making up only 1% of total leucocytes
Describe a lymphocyte
Cells with a round nucleus and a clear scanty cytoplasm
Describe a monocyte
A large cell with an indented bean shaped, curved nucleus and abundant cytoplasm
Describe the function of neutrophils
They are the first line defence against infectious pathogens
They ingest and destroy antibody /antigen complexes and bacteria
The granules contain hydrolyses as well as proteolytic, lipolytic and carbohydrate digestive enzymes
The chemicals they release course fever and inflammatory responses
What is the main constituent of pus
The dead remnants of neutrophils
What is the half life of neutrophils
6 hours In Circulation
How do many neutrophils into the tissues
between the endothelial cells of capillaries by dispedesis
What do eosinophils do
What is the half life like
How do they enter tissue
Release inflammatory substances and kill parasites
The number increases in allergic reactions eg asthma
V short
Through capillary walls
What do basophils do
Enter tissues and release inflammatory substances and histamine when activated
They play a part in the stomach anaphylaxis and hypersensitivity reactions which results in the release of vasoactive agents from their granules
Name two things found in basophil granules.
Histamine
Heparin (an anticoagulant)
How are lymphocytes divided
Functionally into B- and T- lymphocytes
Both of which help acquire immunity
NK cells (natural killer cells) Are larger and much less abundant than B- or T- lymphocytes and play a role in innate immunity
Discuss B lymphocytes
Produced in the bone marrow and involved in the production of circulating antibodies
Discuss T lymphocytes
Involved in cell mediated immunity
Produced in bone marrow but complete their maturation in the thymus
What is the half life of a monocyte
What happens after this
~72 hours
They enter the tissues and become tissue macrophages
As macrophages they show avid phagocytosis and are important in and ingesting and destroying bacteria and foreign particulate material
Tissue macrophages comprise…
Kupffer cells of the liver
Macrophages of the pulmonary alveolus (dust cells)
Microglia of the brain
What are mast cells
Granulated, wondering cells that originate in the bone marrow but are released into the circulation as mast cell progenitors that mature when they are in the tissue
What do the granules of mast cells contain
Histamine
Heparin
Proteases
Where are mast cells found
What are other functions of mast cells
In areas of connective-tissue where they play A role in inflammatory responses e.g. post defence to invading parasites and allergic reactions
Recruitment of immune cells, smooth muscle contraction and increased vascular permeability
