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Collin College
BIOL. 2401Chapter 4
Tissue Levels
CONNECTIVE TISSUE
• Depending on the stimuli, mesenchyme develops into specific cells that give rise to the different C.T. types
• The cells of each C.T. type secrete a surrounding matrix
• The majority of connective tissue is the matrix; it is made out of• ground substance• extra-cellular protein fibers
• Depending on the type of C.T., the matrix will be • fluid and flexible with few or many cells• solid and rigid with few or many cells
• C.T. derives from Mesenchyme embryonic tissue.
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CONNECTIVE TISSUE
• Establishes structural frameworks• Transport fluids and dissolved materials• Protect delicate organs• Support, surround and interconnect tissues• Store energy reserves and minerals• Defend the body from microorganisms
Functions
CLASSIFICATIONS
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CLASSIFICATIONS
COMPOSITION AND ORGANIZATION
Contains largest variety of cells, has viscous ground substance and different fibers
Connective tissue proper
• Fibroblasts – produce the fibers•Macrophage – engulf pathogens• Adipocytes – fat-storing cells•Mesenchymal cells – stem cells
• Melanocytes – pigment producers•Mast cells – trigger inflammation• Lymphocytes – attack foreign antigens•Microphages – engulf cell remnants
Types of Cells
Types of Fibers• Collagen fibers – flexible , high strength• Elastic Fibers – coiled fibers with elastic properties•Reticular – supporting network fibers
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• Fibroblasts– The most abundant cell type:
• Found in all connective tissue proper• Secrete proteins and hyaluronan (cellular cement)
• Fibrocytes– The second most abundant cell type
• Found in all connective tissue proper• Maintain the fibers of connective tissue proper
• Adipocytes– Fat cells : each cell stores a single, large fat droplet
• Mesenchymal Cells– Stem cells that respond to injury or infection
• Differentiate into fibroblasts, macrophages, etc.
Cells of Connective Tissue Proper
• Macrophages– Large, amoeba-like cells of the immune system
• Eat pathogens and damaged cells. Fixed macrophages stay in tissue, Free macrophages migrate
• Mast Cells– Stimulate inflammation after injury or infection
• Release histamine and heparin• Lymphocytes
– Specialized immune cells in lymphatic (lymphoid) system• For example, lymphocytes may develop into plasma cells
(plasmocytes) that produce antibodies
Cells of Connective Tissue Proper
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• Collagen Fibers– Most common fibers in connective
tissue proper– Made from three amino acid chain
helices, bundled together into fibrils. In turn, many such fibrils from a collagen fiber.
– They are long, straight, and unbranched
Fibers of Connective Tissue
– Strong and flexible ; resist force in one direction – For example, tendons and ligaments– In skin for example, 90% of dermis is collagen. It can retain 8x its
weight in water…major moisterizing agent in your skin
• Reticular Fibers– Network of interwoven fibers (stroma)– Strong and flexible as well ; resist force in many directions– Stabilize functional cells (parenchyma) and structures– For example, sheaths around organs
Fibers of Connective Tissue
• Elastic Fibers– Contain elastin– Branched and wavy; return to
original length after stretching– Found where function requires
elasticity and strenght ( Ex: elastic arteries)
Elastic fibers in 6 years old and 90 year old individual
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Ground Substance Connective Tissue Proper
• Ground Substance– Is clear, colorless, and viscous– Fills spaces between cells and slows pathogen
movement
• Important note : fibers and ground substance are found in all connective tissues. Connective tissue proper just has a lot more variety of cells
Reticularfibers
Melanocyte
Fixedmacrophage
Plasma cell
Bloodin vessel
Adipocytes(fat cells)
Groundsubstance
Mast cell
Elasticfibers
Freemacrophage
Collagenfibers
Fibroblast
Mesenchymalcell
Lymphocyte
CELLS AND FIBERS OF C.T. PROPER
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Mesenchyme
• Mesenchyme Tissue is Embryonic Connective Tissues
LM ×136
Blood vessel
Mesenchymalcells
This is the first connective tissue toappear in an embryo.
• Is not found in adults, but mesenchyme cells remain in many connective tissue proper
• It can differentiate into new connective tissues when properly stimulated
Areolar Connective Tissue
• Areolar Tissue• Least specialized• Open framework with Viscous ground substance• Elastic and collagen fibers • Found under many simple epithelial tissues (in lamina
propria)- holds blood vessels and capillary beds
LOCATIONS: Within and deep to thedermis of skin, and covered by theepithelial lining of the digestive,respiratory, and ur inary tracts;between muscles; around joints,blood vessels, and nerves
FUNCTIONS: Cushions organs; providessupport but permits independe ntmovement; phagocyt ic cellsprovide defense againstpathogens
Fibrocytes or fibroblasts
Macrophage
Collagenfibers
Mast cell
Elastic fibers
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ADIPOSE AND RETICULAR C.T.
Adipose Tissue• Contains many adipocytes (fat cells)• Two types of adipose tissue
1. White fat• Most common and Stores fat• Absorbs shocks/Slows heat loss (insulation)
2. Brown fat• More vascularized tissue • Adipocytes have many mitochondria• When stimulated by nervous system, fat breakdown accelerates,
releasing energy • Absorbs energy from surrounding tissues
Reticular Tissue• Provides support via complex, three-dimensional network• Supportive fibers (stroma) support functional cells (parenchyma)• The form structural Reticular organs such as spleen, liver, lymph
nodes, and bone marrow
ADIPOSE AND RETICULAR C.T.
LM × 300
Adipose Tissue
LOCATIONS: Deep to the skin,especially at sides, buttocks,and breasts; padding aroundeyes and kidneys
FUNCTIONS: Providespadding and cushionsshocks; insulates(reduces heat loss);stores energy
Adipocytes(white adipose
cells)
Adipose tissue
LM × 375Reticular tissue
Reticular Tissue
LOCATIONS: Liver , kidney, spleen,lymph nodes, and bone marrow
FUNCTIONS: Provides supportingframework
Reticular tissuefrom liver
Reticularfibers
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• Dense Regular Connective Tissue– Tightly packed, parallel collagen fibers
• Tendons attach muscles to bones• Ligaments connect bone to bone and stabilize organs• Aponeuroses attach in sheets to large, flat muscles
• Dense Irregular Connective Tissue– Interwoven networks of collagen fibers
• Typical in the dermis of the skin• Around cartilages (perichondrium) and bones
(periosteum)• Form capsules around some organs (e.g., liver, kidneys)
DENSE C.T.
DENSE C.T.
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DENSE ELASTIC TISSUE
Made mostly of elastic fibersFor example, elastic ligaments between spinal vertebrae
FLUID CONNECTIVE TISSUE
– Blood and lymph = a watery matrix of dissolved proteins– Carry specific cell types (formed elements)
• Formed elements of blood– RBC’s(erythrocytes), WBC’s(leukocytes), Platelets
• Lymphatic system returns extra interstitial fluid back to blood –fluid it monitored by immune system
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SUPPORTING CONNECTIVE TISSUE
Cartilage and bone support soft tissues and the rest of the body
Cartilages :
Matrix is a firm gel containing chondroitin sulfate and protein fibers• Cells are called chondrocytes• Cells are found in lacunae ( “living areas” )• Perichondrium separates cartilage from surrounding tissues• Chondrocytes produce an anti-angiogenesis factor …… prevents the
development of blood vessels into cartilage ( they are thus avascular)• Cannot get too thick – nutrients passage and healing factors are
dependent on diffusion• Three types: hyaline, elastic and fibrocartilage
SUPPORTING CONNECTIVE TISSUE
Hyaline Cartilage
• Stiff, flexible support – most common cartilage• Reduces friction between bones and protects• Found in synovial joints, rib tips, sternum, • Keeps the trachea open• Usually, lacunae are large and not touching, fibers not visible
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SUPPORTING CONNECTIVE TISSUE
Elastic cartilge
• Supportive but bends easily• Found in external ear and epiglottis• Lacunae very close to each other with visible thin elastic
fibers between
Fibrocartilage (Fibrous Cartilage) • Limits movement - Prevents bone-to-bone contact• Found between pubic bones and intervertebral discs• Lacunae are tiny and occur in small groups far apart• Fibers sometimes visible as “smears”
Fibrocartilage
LOCATIONS: Pads within knee joint;between pubic bones of pelvis;intervertebral discs
FUNCTIONS: Resists compression ;prevents bone-to- bonecontact; limitsmovement
Fibrocartilage
Chondrocyt esin lacunae
Fibrousmatr ix
LM × 400
LOCATIONS: Auricle of external ear;epiglottis ; auditory canal; cuneiformcartilages of larynx
FUNCTIONS: Provides support, buttolerates distortion withoutdamage and returnsto or iginal shape
Elastic cartilage
Chondrocyt esin lacunae
Elastic fibersin matr ix
LM × 358
Elastic Cartilage
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SUPPORTING CONNECTIVE TISSUE
BONE• Has osteocytes located in lacunae• In compact bone, they are located in concentric circles around
a central canal containing blood vessels• Cells depend on diffusion through canaliculi for nutrients• Little ground substance but dominating collagen protein fibers
provide limited flexibility within a dense mineralized matrix –hard to break unless changes occur within matrix
• Surrounded by periosteum
Canaliculi
Osteocytesin lacunae
Matr ix
Central canal
Blood vessels
LM × 375Osteon
Osteon
Fibrouslayer
Cellularlayer
Periosteum
BONE CONNECTIVE TISSUE
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MUSCLE TISSUE
• Specialized for contraction• Three types• Skeletal muscle : Striated and voluntary• Cardiac muscle : Striated and involuntary• Smooth muscle : not striated and involuntary
Striations in muscle are due to a very organized arrangement of the two contractile protein strands : actin and myosin
MUSCLE TISSUE
• Very long/thin cells that are multinucleate• They have a striated appearance• They are our voluntary muscle• Divide/regenerate via satellite cells
Str iations
Nuclei
Musclefiber
LM × 180Skeletal muscle
Skeletal Muscle Tissue
Cells are long, cylindrical,str iated, and multinuclea te.
LOCATIONS: Combinedwith connectiv e tissuesand neural tissue inskeletal muscles
FUNCTIONS: Moves orstabilizes the position ofthe skeleton; guardsentrances and exits to thedigestive, respiratory, andurinary tracts; generatesheat; protects internalorgans
a
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MUSCLE TISSUE
• Cardiocytes occur only in the heart• Microscopic short cells that are branched and connect
via intercalated discs • They are striated involuntary muscle• Rely on pacemaker cells for regular contraction
MUSCLE TISSUE
• They are not striated and short, tapered cells ----involuntary muscle
• Found everywhere motion is needed inside the body
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NEURAL TISSUE
• Conducts electrical impulses• Conveys information from one area to another• CONTAINS TWO MAIN TYPES OF CELLS
• Neurons• Transmit electrochemical signals• Organized into a cell body, axon, and dendrites• Dendrites receive the information and electrical
information is guided down the axon to other neurons
• Neuroglia : Support neural tissue and help supply nutrients to neurons
NEURAL Tissue
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BODY SYSTEM MEMBRANES
• They Form barriers to protect organs• They are Composed of epithelium and
connective tissue
• Four types• Cutaneous• Synovial• Serous• Mucous
Body membranes
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Cutaneous Membranes
• Cutaneous membrane = skin– A dry membrane– Outermost protective boundary
• Superficial epidermis– Keratinized stratified
squamous epithelium• Underlying dermis
– Mostly dense irregular connective tissue
Mucous Membranes• Lines passage ways that
communicate with the exterior
• Must be kept moist to reduce friction
• The epithelial layer is lubricated by mucus from goblet cells or via multi-cellular glands
• The epithelial layer can be simple (ex : lining of intestine) or stratified (ex: lining of mouth)
• The connective tissue layer under these membranes is called the lamina propria and is mostly areolar C.T.
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• Line the sealed internal subdivisions of the ventral body cavity ( cavities that DO NOT open to the exterior)
• 3 main types of serous membranes are• The pericardium• The pleura• The peritoneum
• Each serous membrane has two layers to it• The parietal portion : attaches to the inner surface of the body
cavity ( body wall)• The visceral portion or serosa : covers the outer surface of
the organ involved. The epithelial layer is lubricated by mucus from goblet cells or via multicellular glands
Serous Membranes
Serous MembranesSerous layers are separated by serous fluid
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• Composed out of only Connective tissue only
• Lines fibrous capsules surrounding joints
Synovial Membranes
CONNECTIVE TISSUE FRAMEWORK
• Layers of CT connect the organs within the dorsal and ventral body cavities
• The layers provide strength, maintain position of organs and provide routing areas for bloodvessesl and nerves
• Fasciae are connective tissue layers that support and surround organs• Superficial Fascia or Subcutaneous layer
• also called the Hypo dermis ( located under the dermis layer)• areolar CT and fat
• Deep fascia• dense irregular CT
• Subserous fascia• layer of areolar CT between deep fascia and serous membranes
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CONNECTIVE TISSUE FRAMEWORK