LOOSE CONNECTIVE TISSUE

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LOOSE CONNECTIVE TISSUE Loose vs. Dense
arbitrary Loose arrangement of fibers or Dense
arrangement of fibers Loose C.T. includes
Areolar, Adipose, Reticular
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RETICULAR TISSUE Framework of lymphoid organs,
bone marrow, liver, alimentary and respiratory
mucous membranes Includes reticular fibers and
reticular cells Other regions reticular fibers
and fibroblasts fat cells, smooth muscle,
capillaries, stroma of non-lymphoid,
parenchymatous organs not reticular tissue in
strictest sense
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Cells of Reticular Tissue Reticular
cells stellate resemble mesenchymal
cells considerable cytoplasm nucleus large and
pale cytoplasmic extensions appear to touch
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Primitive Reticular Cells resemble
mesenchyme can differentiate (diverse) some
specialize to produce reticular fibers Phagocytic
Reticular Cells larger cells lose some
developmental potential fixed macrophages
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Reticular Fibers Arrangement ? fine lattice-work
of branching threads Cell processes related to
these fibers wrap around / extend along
fibers Lymphocytes/other cells in interstices of
meshwork
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Functional Considerations Fibers long
delicate connecting and supporting
framework Under epithelia enter into basement
membrane Primitive reticular cells produce
lymphocytes and macrophages Phagocytic reticular
cells scavengers / defense against bacteria
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AREOLAR TISSUE A loosely arranged, fibro-elastic
connective tissue Most widespread C.T. Gross
anatomy dissection freeing areolar from
other things
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Encounter in every microscopical part of
body Fastens down skin and other
membranes Conducts blood
vessels/nerves Binds muscles and
parts Bedding-substance (stroma) inside
many organs Mobile body parts ? areolar
surrounds stretchy, anchoring, embedding
medium
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Gross Whitish to translucent Soft, pliable,
slippery, stretchy (handlens
cobwebby Structure Ground substance amorphous
jelly containing coagulable tissue fluid Cells
fibroblast and macrophages most
numerous Fibers Collagenous (greatest bulk)
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Elastic fibers continuous branching
network Reticular fibers where areolar
borders other structures. FUNCTIONAL
CONSIDERATIONS Mechanical Transport of
metabolites Defense Repair
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ADIPOSE TISSUE Areolar contains scattered fat
cells areas dominated by aggregations Adipose
Tissue A storage tissue ? amount varies with
nutritional state
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OCCURRENCE under skin (panniculus
adiposus) around kidneys and suprarenals mesente
ries groove of heart bone marrow cervical,
axillary,inguinal regions Different distibutions
in men and women genetic and endocrine reflect
influences Absent nervous system, lungs,
eyelids, penis
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Development and Involution embryonic
mesenchyme, lipoblasts, fibroblasts collect
along small blood vessels (adult) enlarge,
withdraw processes, round up lipid droplets
coalesce Loose lipid may remain round watery
filled vacuoles Some adipose pads retain fat
tenaciouly long starvation orbit, joints,
palm, sole
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STRUCTURE Atypical connective tissue specialized
for particular purpose cells, not interstitial
substance, dominates cells bulk of the
tissue Fresh cell highly refractive, bright,
glistening yellow color (lipochrome
pigments) cytoplasm thin rim around
vacuole Fine reticular meshwork around each cell
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Fat mixture of glycerides and fatty
acids Staining agents Sudan III and IV
(freeze-dried sections) Osmic acid blackens fat
and myelin BROWN FAT peculiar, only in a few
mammals light brown color glandular
appearance cells polyhedral fat in numerous
droplets (not single vacuole)
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DENSE CONNECTIVE TISSUE Abundant, compact
fibers Limited space left for ground
substance Subdivisions fiber direction and
dominant fiber type
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INTERLACED ARRANGEMENT OF FIBERS Dense
Irregular Connective Tissue Predomoninantly
collagenous (whitish) Most facias and dermis of
skin Organ capusles (liver, testis) Sheaths
(periosteum, epimysium, dura mater) Septa and
Trabeculae (partitions in organs) Predominantly
elastic (yellow) tubular sheaths in wall of
blood vessels consolidates into elastic
membranes of largest arteries
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Dense Irregular Connective Tissue, Predominantly
Collagenous Dermis large red fibers collagen
small black fibers elastic
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Wall of Elastic Artery
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PARALLEL ARRANGEMENT OF FIBERS Dense Regular
Connective Tissue Predominantly
collagenous Tendon (most common/obvious Ligame
nts Aponeuroses
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TENDON Unit Primary tendon bundle A very
large collangenous fiber clasped by
fibroblasts Primary bundles run parallel to each
other Fine elastic networks may be present
between primary bundles Only cell type ?
FIBROBLAST Primary bundles group together into a
tendon fascicle Fascicles separated by areolar
C.T.
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Predominantly elastic less common than
collagenous type Examples ligamentum flava
(of vertebrae) suspensory ligament of
penis stylo-hyoid ligament true vocal
cords ligamentum nuchae (of quadrupeds) distinc
tly yellow dues to large number of elastic fibers
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