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Tissues5.3-5.6

August 31, 2012

5.3 Connective Tissues• Objectives

• List the types of connective tissue in thebody

• Describe the general cellular components,structures, fibers, and matrix of eachconnective tissue

• Describe the major functions of each type ofconnective tissue

General Features of ConnectiveTissues• Connective Tissues are the most abundant and

widely distributed tissues in the body – they are alsothe most heterogeneous of the tissue groups• They perform numerous functions:• Bind tissues together• Support and strengthen tissue• Protect and insulate internal organs• Compartmentalize and transport• Energy reserves and immune responses

• Collagen is the main protein of CT and the mostabundant protein in the body, making up about25% of total protein content

• Connective tissue is usually highly vascular andsupplied with many nerves

• The exception is cartilage and tendon - bothhave little or no blood supply and no nerves

• Although they are a varied group, all CT share acommon “theme”

• Sparse cells

• Surrounded by an extracellular matrix

• The extracellular matrix is a non-cellular materiallocated between and around the cells

• It consists of protein fibers and groundsubstance (the ground substance may be fluid,semifluid, gelatinous, or calcified)

Connective Tissue Cells• Fibroblasts are the most numerous cell of connective

tissues• These cells secrete protein fibers (collagen, elastin,

& reticular fibers) and a“ground sub stance” whichvaries from one CT to another

• Chondrocytes make the various cartilaginous C.T.

• Adipocytes store triglycerides

• Osteocytes make bone

• White blood cells migrate from the blood inresponse to infections

• Macrophages are the “big eaters” that swallowand destroy invaders or debris via phagocytosis

• They can be fixed or wandering

• Neutrophils are also macrophages (“smalleaters”) that are numerous in the blood

• Mast cells and Eosinophils play an importantrole in inflammation by producine histamine

• Plasma cells (lymphocytes) secrete antibodyproteins and attack invaders

Connective Tissue of ExtracellularMatrix• CT cells secrete 3 common fibers which provide strength

and support• Collagen fibers composed of collagen• Found in bone, tendons, ligaments

• Elastin fibers composed of elastin, fibrillin, and otherglycoproteins• Found in skin, blood vessel walls, and lungs

• Reticular fibers composed of collagen and glycoprotein• Found around fat cells, nerve fibers, and skeletal

and smooth muscle tissue

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Classification of Connective Tissues• Embryonic connective tissue• Mesenchyme• Mucous connective tissue

• Mature connective tissue

• Loose connective tissue• Dense connective tissue• Cartilage• Bone• Liquid

Embryonic Connective Tissues• Primarily present in the embryo, the developing

human from fertilization through the first twomonths of pregnancy, and in the fetus, thedeveloping human from the third month ofpregnancy to birth

• Mesenchyme gives rise to all other connectivetissues

• Mucous CT (Wharton's Jelly) is a gelatinoussubstance within the umbilical cord and is a richsource of stem cells

Mature Connective Tissues• Mature Connective Tissues are present in the

newborn

• Cells arise primarily from the mesenchyme

• Loose Connective Tissues

• Dense Connective Tissues

• Cartilage

• Bone Tissue

• Liquid Connective Tissue

• Areolar Connective Tissue is the most widely distributed in thebody

• It contains several types of cells, all three fiber types(collagen, elastic, and reticular), and a semifluid groundsubstance

• It is found in the subcutaneous layer, mucus membranes,and around blood vessels, nerves, and body organs

• It is used to attach skin and underlying tissues, and as apacking between glands, muscles, and nerves

• Adipose Tissue consists of adipocytes, which storetriglycerides• It is located in the subcutaneous layer, around

organs and joints, and yellow bone marrow• It reduces heat loss and serves as padding and

as an energy source• Brown Adipose tissue generates heat

• Reticular Connective Tissue is a network ofinterlacing reticular fibers and cells

• It forms a scaffolding used by cells oflymphoid tissues such as the spleen andlymph nodes

• Found in the liver, spleen, and lymph nodes

• Dense Irregular Connective Tissue consistspredominantly of fibroblasts and collagen fibersrandomly arranged

• It provides strength when forces are pulling frommany different directions

• It is found in fasciae, the dermis of the skin, andmembrane capsules around organs

• Dense Regular Connective Tissue consists ofparallel bundles of collagen fibers and fibroblasts– It forms tendons, ligaments, and other strong

attachments where the need for strength along oneaxis is mandatory (a muscle pulling on a bone)

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• Elastic Connective Tissue consists of fibroblasts

and freely branching elastic fibers

• It allows stretching of certain tissues like the

elastic arteries (the aorta)

• Is found in the walls of large arteries, lungs,

trachea, and bronchial tubes

• Cartilage contains chondrocytes and has a rubberyextracellular matrix containing collagen and elastic fibers• It is a tissue with poor blood supply that grows slowly and

when injured or inflamed, repair is slow• Hyaline cartilage is the most abundant type of cartilage and is

found in embryonic skeletons, the ends of long bones, andparts of the ribs, nose, trachea, bronchi, and larynx• Consists of a gel-like ground substance and appears bluish-

white in the body• It provides a smooth surface for joint movement, is flexible,

allows movement, provides support, and is usuallysurrounded by the perichondrium

• Fibrocartilage, with its thick bundles of collagen fibers, is avery strong, tough cartilage

• It contains chondrocytes scattered among bundles ofcollagen fibers

• It is found in the pubic symphysis, invertebral discs, andmenisci of the knee joint

• Fibrocartilage discs in the intervertebral spaces andthe knee joints support the huge loads up anddown the long axis of the body

• Elastic cartilage consists of chondrocytes located in athreadlike network of elastic fibers and also has aperichondrium

• Maintains the shape of organs

• Makes up the malleable part of the external ear,auditory tubes, and the epiglottis

• Bone consists of an extracellular matrix of mineralsalts and collagen fibers, and osteocytes that arelocated in the lacunae

• Bone supports and protects the body, provides asurface for muscle attachment, helps the bodymove, stores minerals, and houses blood formingtissue

• Blood and lymph are two types of liquid CT• Blood tissue consists of blood plasma, RBC, WBC, and

platelets– Transport oxygen and carbon dioxide, carry on

phagocytosis, participate in allergic reactions, provideimmunity, and bring about blood clotting

• Lymph is the extracellular fluid that flows in lymphaticvessels– Is a clear fluid similar to blood plasma but with less

protein

5.4 Muscular Tissues• Objectives

• Distinguish among the three types ofmuscle tissues

• Consists of muscle fibers or myocytes that are specializedfor contraction– Provide motion, maintenance of posture, heat

production, and protection• Skeletal muscle tissue is attached to bones and is striated

and voluntary• Cardiac muscle tissue, which forms most of the heart wall

is striated and involuntary• Smooth muscle tissue is found in walls of hollow internal

structures and is nonstriated and involuntary

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5.5 Nervous Tissue• Objectives

• Describe the general characteristics andfunctions of nervous tissues

• The nervous system is composed of neurons andneuroglia

• Neurons respond to stimuli by converting thestimuli into electrical signals called nerve actionpotentials and conducting nerve impulses to othercells

• Most neurons consist of a cell body and two typesof processes, dendrites and axons

5.6 Membranes• Objectives

• Describe the four major types ofmembranes

Epithelial Membranes• Combining two tissues creates an organ

• Epithelial membranes are the simplest organs inthe body, constructed of only epithelium and alittle bit of connective tissue

• Epithelial membranes consist of an epithelial layeroverlying a connective tissue layer• Mucous membranes• Serous membranes• Cutaneous membrane

• Mucous membranes line “interior” body surfaces open tothe outside:

• Digestive tract

• Respiratory tract

• Reproductive tract

• Serous membranes line closed cavities and covers organsin those cavities

• Consist of parietal and visceral layers

• Parietal layer next to body wall

• Serous fluid between layers

• Visceral layer next to organ

• Pleura, pericardium, peritoneum

Synovial Membranes• Synovial membranes line joint cavities and consist

of areolar connective tissue

– They do not have an epithelial layer