Connective Tissue Flashcards
(31 cards)
What do connective tissue consist of?
Connective tissue
consists of cells embedded in large quantities of extracellular matrix.
What is the extracellular matrix of connective tissue composed of?
The extracellular matrix of connective tissue is composed of protein fibres, amorphous
ground substance and tissue fluid.
What are the functions of connective tissue?
Space filler and mechanical support.
Attachment and protection
Highway for nutrients
Main fat store and calcium store
Site of many immunological defence reactions
What are connective tissue subdivided into?
Soft connective tissue
Hard Connective Tissue
Blood and lymph
What consists of soft connective tissue?
Tendons, ligaments,
mesentery, stroma of
organs, dermis of the
skin, etc
What consists of hard connective tissue?
Bone and cartilage
What does blood and lymph consist of?
blood and lymph is considered as a specialized form of
connective tissue
What is the type of connective tissue determined by?
The type of connective tissue is determined by the
types and relative amounts of these two
components.
What are the resident cells present in connective tissue?
- Fibroblasts
- Adipose cells
- Osteocytes: cells of bone
- Chondrocytes: cells of cartilage
What are fibroblasts?
Fibroblasts are elongated cells
with tapered ends that are
widely distributed and that
produce and maintain the
extracellular matrix. Tissue
damage causes fibroblasts
to divide and they are very
important in wound repair.
What are adipose cells?
Adipose cells are fat cells and provide energy for other cells by releasing fatty acids into the blood stream.
They are found scattered in many connective
tissues, but are the predominant cell by far in adipose tissue
(fat). This type of tissue is also called ‘white fat’ or unilocular
fat.
What are the features of Adipose Tissue?
Adipose tissue is the largest store of energy in the body.
It is in a continuous state of turnover and is sensitive to both hormonal
and nervous stimuli.
Subcutaneous layers of adipose tissue help to shape the body, while
deposits in the form of pads act as shock absorbers, e.g. soles of feet &
palms.
Elsewhere it fills up the spaces between tissues and helps to keep some
tissues in position.
In men of normal weight 15-20% of body weight is made up of adipose
tissue and in women 20-25% consists of adipose tissue.
What cells may you see in connective tissue?
During wound healing, myofibroblasts can be found. Myofibroblasts cause wound contraction by producing collagen fibres and tugging on them to draw together the wound margins.
What are some immigrant cells that can be found in connective tissue?
Lymphocytes, plasma cells,
granulocytes and macrophages are commonly found in loose
connective tissue. These migrate from the blood stream. The
number of these cells increases dramatically at sites of inflammation
or infection.
Mast cells, which can be found in connective tissue, contain
granules of heparin, histamine and substances that stimulate
inflammation and attract white blood cells. The release of histamine is responsible for the symptoms of allergic reactions.
What transient cells are found in connective tissue?
Leukocytes
These migrate from the blood.
1. Neutrophils leave the blood stream in response to infection.
2. Eosinophils are found in increased number during allergic reactions
and parasitic diseases.
What are the features of Macrophages?
Macrophages are derived from monocytes in the bone marrow and circulate in the blood before migrating into the connective tissue where they transform into macrophages.
They can proliferate locally.
They are phagocytic cells
that have a body-wide
distribution and live for
several months. 10-30 μm in
diameter
What are the characteristics of mast cells?
Mast cells are the largest of the cells in the connective tissue (20-30um diameter) (except for adipose cells) and are widely dispered.
Mast cells are sensitive to foreign proteins and
rapidly release their contents when these are
detected.
They are the cells which react in hay fever and
asthma.
What do basophilic granules do?
Basophilic granules containing heparin (an
anticoagulant) fill the cytoplasm.
What does histamine do?
Histamine ncreases the
permeability of small blood vessels and, in airways,
causes increased mucous production and smooth
muscle contraction
What are lymphocytes
Lymphocytes are leukocytes that are widely scattered in
connective tissue where they are the smallest cells present,
often appearing as a small nucleus with almost no cytoplasm
surrounding it.
They are found in large numbers in some areas, for example
the gut.
There are several types of lymphocytes, and one type (B
lymphocytes) gives rise to plasma cells
What are the characteristics of plasma cells?
Rare in connective tissue but more numerous at sites of infection. They are
large oval cells rich in rER.
They have basophilic cytoplasm and are responsible for the synthesis of
antibodies found in the blood stream.
Therefore they neutralise harmful antigens, render toxins harmless,
promote phagocytosis and as a result protect the body from micro-
organisms.
What does the extracellular matrix consist of?
Extracellular matrix consists of
* Fibres: collagen, reticular and elastic fibres
* Ground substance: an amorphous, space
occupying material made of huge
unbranched polysaccharide molecules called
glycosaminoglycans (GAGs), most of which are bound to protein cores to form
glycoproteins
* Tissue fluid
What are the characteristics of collagen fibres?
They are the most abundant protein in the human body constituting 30-40% of the
protein in the body.
Collagen is synthesised in the fibroblasts and is formed from three
polypeptide chains. Collagen molecules are approximately 300nm long and
have striations every 68nm.
Collagen fibrils are inelastic and the most common form (type I) has a
tensile strength (on a weight for weight basis) similar to mild steel, giving a
tissue which is both flexible and strong.
What are the characteristics of Reticular Fibres?
Reticular fibres are thin fibres, made of a special
type of collagen (Type III), that forms a support
network in many organs (indeed, the word
‘reticular’ comes from
reticulum which is Latin
for a net).
Reticular fibres form the supporting scaffolding
in organs like the liver, lymph nodes, spleen and
bone marrow.
