BIOB33H3 Lecture Notes - Lecture 4: Synovial Joint, Chondrocyte, Haversian Canal
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Lecture 4
Foundations: Connective Tissues
(Chapter 3)
Connective Tissues
Tissues that connect or form structures
Most diverse, abundant, widely distributed and microscopically variable
All derived from mesoderm
Examples: bone, cartilage, blood, connective tissue proper – ligament, tendon, fibrous tissue, loose
connective tissue, dense connective tissue, fat
Functions of Connective Tissue
•Physical protection – bones of cranium, sternum, vertebral column, thoracic cavity,
fat surrounding organs
•Support and structural framework of the body – bones provide framework and support soft
tissues; cartilage supports body structures such as trachea, bronchi, nose and ears; sheets
of connective tissue form capsules to support such organs as spleen and kidneys
•Transporting fluid and dissolved materials – blood carries nutrients, gases, hormones, wastes
and blood cells between different regions of the body
•Connecting other tissues – ligaments bind bone to bone; tendons bind muscle to bone; dense
irregular tissue (fascia) binds skin to underlying muscle and bone
•Storing energy – fat is major energy reserve in the body, bones are a large reservoir for
calcium and phosphorus
•Immune protection – much connective tissue contains white blood cells (leukocytes) which
protect the body against disease and mount an immune response against foreign material;
the viscous nature of the extracellular matrix interferes with the movement and spread
of disease causing organisms
Elements of Connective Tissues
•Cells spaced far apart (unlike epithelium where we don’t want things to move between
the cells; no extracellular space)
•Lots of extracellular matrix (ECM) between cells
§Matrix is the collective term for the extracellular component of any
connective tissue that is made of protein fibers and the ground substance
(ground substance is not made out of any cells)
§ECM is secreted from cells of connective tissue by proteins in fibrous
tissues called fibroblasts
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TERMINOLOGY - ______cyte – a generic cell type (eg. osteocyte in bone, adipocyte in fat)
-_______blast – produces something,lays down some foundation (eg. osteoblast is a cell
that lays down (makes) bone matrix, fibroblasts in connective tissue proper; EG.
BLAST = SOMETHING THAT MAKES SOMETHING ELSE)
-______clast – reabsorbs/breaks down something (eg. osteoclast breaks down bone)
§ECM composed of:
o Ground substances – sugary water and protein and
carbohydrate molecules (gelatin-like), proteins help to keep
water in
o Fibers:
§COLLAGEN – for tensile strength and stretch resistant (largest
and strongest)
§ELASTIC (not as strong/large, but allow tissues to stretch,
have elasticity) –which are flexible and resistant
§RETICULAR – which form an interwoven network
Classification of Connective Tissues: based on
type of extracellular matrix:
•Connective tissue proper - has a
matrix of fibers (loose and dense) in a
syrupy ground substance (kind of like
“jello” with fruit in it
•Different types have different
numbers of cell types and
different relative proportions of
fibers and ground substance
(examples include: adipose
(fat), ligaments, tendons)
•Fluid connective tissue - has a matrix
of watery liquid than contains dissolved
proteins (examples are: blood and lymph)
•Supporting connective tissue - has a matrix consisting of a gel (densely packed fibers),
cartilage or a solid (matrix is calcified of mineral deposits of predominantly calcium), bone
Connective Tissue Proper
•Types with Loose fibers: Areolar tissue, Adipose tissue, Reticular tissue
•Types with Dense fibers: Dense regular, Dense irregular, Elastic
Different Types of Connective Tissue Proper contain various types of FIXED and WANDERING cells
Fixed Cells:
Fibroblasts – produce connective tissue fibers
Fibrocytes – maintain connective tissue fibers and matrix
Fixed macrophages – phagocytize pathogens and damaged cells
Adipocytes – store lipid reserves
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Mesenchymal cells – connective tissue stem cells that can differentiate into other cell types
Melanocytes – synthesize melanin
Wandering Cells:
Free Macrophages – mobile/travelling phagocytic cells (derived from monocytes of the blood)
Mast Cells – stimulate local inflammation
Lymphocytes – participate in immune response – can develop into plasmocytes which
produce antibodies (proteins involved in defending the body against disease)
Neutrophils and Eosinophils (white blood cells) – small phagocytic blood cells that
mobilize during infection or tissue injury
Loose Connective Tissue (fibers are far
apart)
•Areolar Tissue
•Location - deep to the
dermis, covered by
epithelial lining, between
muscles, around blood
vessels, nerves and
around joints
•Function - connects skin
to muscle, cushions
organs, provides support
but with movement
•– abundant collagen fibers,
thin irregularly arranged
elastic fibers, small fibroblast cells, adipocyte (fat) cells and abundant gel-like ground
substance
•Adipose Tissue
•Location – hypodermis,
buttocks, breasts, around
eyes, surrounds organs
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Document Summary
Most diverse, abundant, widely distributed and microscopically variable. Examples: bone, cartilage, blood, connective tissue proper ligament, tendon, fibrous tissue, loose connective tissue, dense connective tissue, fat. Physical protection bones of cranium, sternum, vertebral column, thoracic cavity, fat surrounding organs. Transporting fluid and dissolved materials blood carries nutrients, gases, hormones, wastes and blood cells between different regions of the body. Connecting other tissues ligaments bind bone to bone; tendons bind muscle to bone; dense irregular tissue (fascia) binds skin to underlying muscle and bone. Storing energy fat is major energy reserve in the body, bones are a large reservoir for calcium and phosphorus. Elements of connective tissues: cells spaced far apart (unlike epithelium where we don"t want things to move between the cells; no extracellular space) Matrix is the collective term for the extracellular component of any connective tissue that is made of protein fibers and the ground substance (ground substance is not made out of any cells)
