Connective Tissue
(CT)
Diversity of Connective Tissue
Types and Functions:
• Loose Connective Tissue: Areolar and fat
– insulation, protection (padding), loosely connecting
structures
• Dense Connective Tissue: Ligaments and tendons
– binding and support
• Cartilage
– protection, support
• Bone
– support
• Blood
– transportation
Common Characteristics of all CT
3.
Composed
of
different
types
of
cells
within
5.
All
support
epithelium
1.
Embryonic
origin:
(mesenchyme)
theVariation
tissue. in amount of blood supply
4.
(vascularization)
2. Has an extracellular matrix of fibers and ground
substance.
Ground substance
Loose Connective Tissue
Ex. 1: Areolar – most widely distributed type.
– Gelatinous
– Loosely packed; lots of liquid held in ground
substance
– “packing material” cushioning organs,
subcutaneous, attaches skin to muscle.
– Has all three fibers
– Cells: fibroblasts, macrophages, mast cells, and
white blood cells
– Swells during inflammation (edema)
Areolar (Prototype)
collagen
Ground substance
Mast cell
Elastin
Fibroblast
Loose Connective Tissue
• Ex. 2: Adipose = Fat!
– Loosely packed with sparse matrix
– 90% of tissue is mature adipocyte cell
– Most of each cell is a fat droplet, so nuclei is
displaced to the side
– Richly vascularized
– Nutrient storage, cushioning in areas like abs,
hips, around kidneys
– High concentrations subcutaneous (under skin) –
shock absorber, insulation
– Fat deposits act as local nutrient sources around
active organs (heart, muscles)
Adipose
Adipose
Loose Connective Tissue
• Ex. 3 Reticular
– Only contains reticular fibers.
– VERY DELICATE – a fine net of fibers that
act as a “soft” skeleton
– Supports lympho nodes, bone marrow,
spleen, free blood cells.
Dense Connective Tissue
• Ex. 1: Dense Regular – Tendons and
Ligaments
– Fibers predominate.
– Abundant and crowded fibroblasts make
fibers
– Little ground substance
– Regular, parallel bundles of collagen fibers
– Resist tension: pull and stretching.
– Ligaments connect bone to bone
– Tendons connect muscle to bone.
– Poorly vascularized
Regularly aligned collagen
Fibroblast nuclei
Dense Connective Tissue
• Ex. 2: Dense Irregular
– Thicker, irregularly arranged collagen.
– Found where tension is applied in different
directions
– Example: Dermis of skin, organs, joints
Dense Regular
Dense Irregular
Cartilage
Characteristics
– Resists tension AND compression
– Lots of collagen (strong) AND elastic fibers
(flexible)
– No nerves or blood vessels
– High content of proteoglycans 80%
water
– Chondroblasts make matrix until end of
human adolescence
– Mature Chondrocytes found in cavities
called lacunae (pit)
Hyaline Cartilage
• Looks glassy (hyalin = glass)
• Few chondrocytes, all found in lacunae
• Mostly matrix – lots of collagen
• Reduces friction, absorbs pressure
• Covers ends of long bones, connects ribs
to sternum, forms rings in trachea and
bronchi
Elastic Cartilage
• Looks almost identical to hyaline BUT
more elastic fibers  more flexible!
• Matrix appears more fibrous
• More lacunae, closely spaced.
• Found in ear and epiglottis
Hyaline Cartilage
Elastic Cartilage
Fibrocartilage
• Intermediate between dense regular CT
and hyaline
• Consists of rows of chondrocytes and
collagen fibers
• Compressible AND resists tension
• Found in intervertebral discs.
Bone (Osseous Tissue)
• Most supportive tissue in body.
• Matrix is similar to cartilage, but with morer
collagen (strong) surrounded by calcium salts
• Osteoblasts make collagen fibers and calcium
salts deposited between fibers.
• Well vascularized
• Osteocytes stored in lacunae
• Bone marrow stores fat and makes blood cells.
Blood
• Atypical connective tissue
• Only classified as such because it arises
from same embryonic tissue
• Blood cells are within a matrix of blood
plasma.
• Fibers apparent only when blood clots.
How do damaged tissues repair?
Injured cells release hormones and
proteins to signal need for healthy cells
to divide and migrate.
Steps to Tissue Repair
1) Regeneration
2)
3)
Restore
Inflammation
Bloodor
Supply
below
scab
• Fibrosis
Inflammatory
Granulation
tissue
chemicals
•
•
•
•
released
clot,
by injured
digested by
a)replaces
Regeneration:
cells,
macrophages
macrophages,
replacement
w/ same
mast
cells
New
capillaries
tissue
type form.
dilate,
allowing
Fibroblast
inreplacement
granulation
b)Vessels
Fibrosis:
clotting
andcollagen
plasma
tissue
and
w/ make
fibrous
connective
proteins
and
growth
tissuefactors.
(scar)wbc to
invade injured site.
Clotting proteins begin
clotting.
Fibrosis replaces tissue in nonregenerative tissues
Regeneration Capacity
•Mostly collagen
•STRONG but lacks
Varies
by
tissues
flexibility/elasticity
•Cannot perform function of
tissue that was replaced
High capacity
•Epithelial
•Bone
•Areolar CT
•Dense I. CT
•Blood forming
tissue
•Dense R. CT
•Cartilage
No capacity
•Cardiac Muscle
•Nervous Tissue
Extracellular Matrix
• Embeds cells of connective tissue
• Medium for nutrients and other dissolved substances
that nourish cells
• Made up of ground substance and fibers.
• Ground substance
– Texture varies
•Can be liquid, gel-like, semi-solid or hard.
•depends on amount of cell adhesion proteins
that trap water called proteoglycans
– More proteins, more solid ground substance.
• Fibers provide strength and/or flexibility
– Allows for weight bearing, withstanding of
mechanical abuse, tension – protects!!
Dense
connective
tissue, lots
of fibers,
little open
space.
Loose
connective
tissue:
Lots of
ground
substance –
fewer fibers
Fibers
• Embedded in ground substance
• Adds strength/flexibility.
• Created by undifferentiated “blast” cells
of extracellular matrix
• 3 Kinds
1. Collagen: Strong
2. Elastic: Flexible
3. Reticular: Delicate
Collagen (white fibers)
• Rope-like bundles
• Tough, stronger then
steel!
• Tension resistant
Return to fibers
Elastic (yellow fibers)
• Long, thin
• Branching networks
• Stretch and recoil
ability for elasticity
• Highly concentrated in
areas like skin, lungs,
vessels where elasticity
is needed
Back to common characteristics of CT
Reticular “network” fibers
• Short, fine, delicate
• Collagenous, but with
more give due to
branching network
• Support soft tissue
organs, blood vessels
• abundant in boundaries
where connective tissue
lines other tissues (ex.
basement membrane)
Blood vessel
Collagen
Reticular
fibers
Cells in Matrix
• Cells of CT make and maintain the ground substance
and fibers of extracellular matrix (ECM).
• Each type of CT have immature and mature forms of
these cells.
• Immature cells have suffix “-blast” – are actively
mitotic and produce ECM.
–
–
–
–
Fibroblasts – make loose and dense CT proper
Chondroblasts – make cartilage
Osteoblasts – make bone
Hematopoeitic stem cells – make blood
• Mature cells have suffix “-cyte” – maintain health of
matrix
– Ex. Fibrocyte
• Mature “cyte” cells can reverting to “blasts” to
regenerate matrix after injury.
What other cells are in CT?
• Accessory Cells:
– White blood cells (macrophages, plasma
cells)– responsible for immune response
– Mast cells – responsible for inflammation
following injury or infection.
– Fat cells – store nutrients
Back to common characteristics of CT