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Lecture 4

BIOC33H3 Lecture Notes - Lecture 4: Muscle Fascicle, Triceps Brachii Muscle, Endomysium


Department
Biological Sciences
Course Code
BIOC33H3
Professor
Connie Potroff
Lecture
4

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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 of connective tissue: 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)
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
ECM is secreted from cells of connective tissue by proteins in fibrous tissues
called fibroblasts
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)
© 2012 Pearson Education, Inc.

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-______clast – reabsorbs/breaks down something (eg. osteoclast breaks down bone)
ECM composed of:
oGround substances – sugary water and protein and carbohydrate
molecules (gelatin-like), proteins help to keep water in
oFibers:
COLLAGEN – for tensile strength and stretch resistant
ELASTIC –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 (LAAR)
Types with Dense fibers: Dense regular, Dense irregular, Elastic
Cells of Connective Tissue Proper contain various types of FIXED (stationary cells involved primarily with
local maintenance/energy storage) and WANDERING cells (cells that require movement for defense and
repair of damaged tissues)
Fixed Cells:
Fibroblasts – produce connective tissue fibers (collagen, elastic, reticular)
Fibrocytes – maintain connective tissue fibers and matrix
Fixed macrophages – phagocytize pathogens and damaged cells
Adipocytes – store lipid reserves
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)
© 2012 Pearson Education, Inc.
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