connective tissue proper Flashcards
connective tissue is derived from which germ layer
mesoderm
connective tissue are ______ tissues, what are some functions
- supportive
- structural framework
- protect organs
- energy stores
- transport of nutrients
- defence from pathogens
connective tissue consist of
cells, protein fibres and fluid ground substance
fibres + ground substances=
matrix
the matrix
surrounds the cells, makes up majority of volume of connective tissue
(protein fibres and ground substance)
3 categories of connective tissue
- connective tissue proper (loose vs dense)
- supportive connective tissue (cartilage, bone)
- fluid connective tissue (blood, lymph)
for connective tissue proper, what is loose vs dense based on
proportions of cells, fibers and ground substances
loose connective tissue= packing materials
dense connective tissues= tendons, ligaments, capsules
constituents
cells that are fixed or migratory, fibres and ground substance
fixed cells
- local maintenance, repair and energy storage
- ex; fibroblasts, adipocytes, mesenchymal stromal cells, macrophages
migratory cells
- aggregate to defend against invading pathogens and to repair damaged tissue
- ex; macrophages, mast cells, lymphocytes, plasma cells
name the 3 main fiber types
collagen, reticular, elastic
what is the most common fibre in connective tissue
collagen
tendons and ligaments are almost entirely
collagen
describe collagen fibers
- long, straight flexible, strong
- 3 polypeptide chains twisted into a ‘rope’
- white/clear when fresh
- stain pink with eosin
what fibres are found in parenchyma of spleen, liver, lymph nodes, glands and bone marrow
reticular fibers
what are reticular fibres composed of
same protein as collagen
reticular fibers are _____ than collagen
thinner
describe reticular fibers and their function
- tough, flexible, branching and interwoven network; stroma
- stabilize position of cells, blood vessels and nerves
what protein is elastic fibers composed of
elastin
describe elastic fibers
- fibres are branched and wavy
- stretch and recoil to relaxed state
- yellowish when fresh
- difficult to see with H&E – specialised stains used
- organised into discontinuous sheets
in artery wall what layers of elastic fibers do we see
internal elastic lamina and external elastic lamina
describe ground substance
clear, viscous, surrounds cells and fibers
what is ground substance function
slows passage of pathogens and facilitates phagocytosis
what does ground substance contain
proteoglycans and glycoproteins
what is most abundant fixed cell in connective tissue proper
fibroblasts
what is the only cell that is ALWAYS present in connective tissue proper
fibroblasts
what do fibroblasts secrete
- components of ground substance and
- protein subunits that from the various fibers
what function are fibroblasts involved in
wound healing
fibroblasts are elongated with
processes lying along fibers
describe fibroblast nucleus
elliptical, centrally placed
mesenchymal stem cells
describe the shape and nucleus
- fixed cells of connective tissue
- star (stellate) or spindle shape
- oval nucleus, prominent nucleolus
what does the multipotency of MSCs mean
they are the precursor cells from which other connective tissue cells
become osteoblasts (bone), adipocytes or chondrocytes (cartilage)
where do MSCs lie
along capillaries, present in many types of connective tissue
how do MSCs respond to infection or injury
transform into other connective tissue cell types
adipose cells
- involved in lipid storage; dietary fat circulating in blood and triglycerides synthesized by liver and adipocytes
- fixed cells of connective tissue proper
what do adipose cells contain
- one or more lipid droplets
- Nucleus displaced peripherally, cytoplasm reduced to a narrow rim
- Main cell type in adipose tissue
- Also present in loose connective tissue - singly or in clumps of cells
white adipose tissue; what does it look like
- cells large, unilocular
- signet ring appearance
- peripheral nuclei
- look like large white bubbles
brown adipose tissue; what does it look like
- smaller multilocular cells
- nuclei round and more centrally place
where does brown adipose tissue get its colour
- colour due to cytochrome respiratory pigment (mitochondria)
- involved in heat production
- many capillaries and nerves
- young animals and hibernators
macrophages (histiocytes) shape and nucelus
- fixed cells of connective tissue
- stellate or fusiform, lie along fibers
- large, irregularly shaped nucleus
what are macrophages derived from
circulating monocytes
what do macrophages do
- phagocytose dead tissue and foreign materials
- when stimulated, release signal that activate the immune system
- store antigenic material to present to antibody producing cells
migratory cells; EXCEPT FOR MAST CELLS migratory cells of the connective tissue proper are
immigrants from the blood
name the migratory cells that are immigrants from blood
lymphocytes, monocytes (macrophages), eosinophils, neutrophils and plasma cells
lymphocytes, monocytes (macrophages), eosinophils, neutrophils are amoeboid (pass between endothelial cells of cells of vessels to enter tissue)
mast cells
- Immune system
- Large cells, shape varies between species
- Small, round nucleus
mast cells have basophilic granules that contain
heparin
& histamine
released in response to injury &
infection
mast cells are similar to ____ that circulate in blood
basophils
mast cells can form
tumours
what do plasma cells look like
- Ovoid, basophilic
cytoplasm - Eccentric ‘cart
wheel’ patterned
nucleus - Perinuclear halo –
Golgi apparatus
where do you see many plasma cells
- High numbers in
lymph nodes & in the
connective tissue of
digestive tract
plasma cells produce
antibodies
classify the types of connective tissue proper
- Loose (areolar) connective tissue
- Dense connective tissue: Regular + Irregular
- Elastic connective tissue
- Reticular connective tissue
- Adipose tissue: White + Brown
which is the least specialized of the connective tissues
loose (areolar) connective tissue
describe loose (areolar) connective tissue
- Binds cells & structures, but permits movement
- Most of volume consists of ground substance
- absorbs shock
- inhibits passage of micro-organisms
- Fibres very loosely arranged
- Cells resist infection & assist wound healing
- Fixed & migratory cells common
- Very vascular
where do you find loose (areolar) connective tissue
- Forms packing around organs, supports epithelial
tissue (e.g. layer of tissue under skin)
dense connective tissue ; what type of fibers dominate
Collagen fibres dominate & fewer cells than in loose
connective tissue
* sometimes called collagenous tissue
describe dense connective tissue’s activity and strength
- Less physiologically active – fewer nerves & blood vessels
- High strength, low to moderate elasticity
regular dense connective tissue vs irregular dense
- collagen fibers parallel
look wavy, can see all fibers going in same direction - vs collagen fibers randomly arranged
where do you find regular dense connective tissue
- tendons (muscle to bone)
- ligaments (bone to bone)
- joint capsules
where do you find irregular dense connective tissue
- dermis
- organ capsules
elastic connective tissue; what type of fibres dominate and how are they arranged
*Elastic fibres dominate
*Irregularly or regularly arranged
describe the elastic connective tissue strength/ elasticity
Moderate mechanical strength & high elasticity
where do you find elastic connective tissue
Airways of respiratory tree, arteries, ligaments of
abdominal cavity & vertebral column
Reticular Connective Tissue forms the fibrous framework of softer tissues such
as
spleen, liver, lymph nodes & bone marrow
adipose tissue
- Mostly fat cells (adipocytes)
- Reserve of energy & water
- Provides padding, packaging & insulation
- White & brown adipose tissues - differ in colour,
vascularity & metabolic activity
lipomas are composed of
adiopocytes
what are lipomas
Benign neoplasms
what animals are lipomas common in
Very common in dogs especially old labradors
and Common in budgies & gallahs
rare in cats
