Connective tissue

§ Connective Tissue (CT) Overview Most abundant and variable tissue type 3 structural elements – Consists mostly of (a) G________; (b) F_______ (c) with widely spaced cells Functions of CT: Binding of organs --Ex. a tendon connects muscle to bone Support, protection, movement -- Ex. bones Storage – (energy, electrolytes) Ex. Fats/bones Transport -- Ex. Blood

§ 1. Ground Substance of C.T. Gelatinous or rubbery material found in between cells – Function? Consists of 3 classes of large molecules Glycosaminoglycans (GAGs) – Polysacharides that attract sodium & hold water Ex.-- Proteoglycan is bottlebrush-shaped molecule Forms thick gel that slows the spread of pathogens Cell adhesive glycoproteins Allow themselves bind to matrix elements 3

§ 2. Fibers of C.T. Collagen fibers--called white fibers (Fig. 5.13) Most abundant protein of the body Thick, tough, resist stretch yet flexible Ex. tendons, ligaments & dermis Elastic fibers--called yellow fibers made of E______; recoil like rubberband (elasticity) Ex. skin, lungs & arteries; ability to recoil Reticular fibers Thin collagen fibers coated with glycoprotein Ex. form framework for spleen & lymph nodes 4

Figure 5.13 Collagen Tendons (collagen)

§ 3. Cells of C.T. Fibroblasts -- produce fibers & ground substance WBCs -- wander (mostly in CT) in search of bacteria Macrophages – large phagocytic cells-- arise from monocytes (WBC); function? phagocytosis Plasma cells -- arise from lymphocytes; antibody-producing cells Mast cells – oval shaped; clustered along blood vessels; secrete heparin and histamine Adipocytes or fat cells --store triglycerides

Connective tissue A. Fibrous CT

§ Five Types of Fibrous C.T. Divided into 2 broad categories: Loose CT (3 slides followed) contains MORE gel-like ground substance between cells 3 types: A--areolar, B--reticular, C--adipose tissue Dense CT (2 slides followed) FIBERS fill the spaces between cells 2 types varying in fiber orientation: D--dense regular, E--dense irregular 8

§ A-- Areolar Tissue Fig. Mesentery Loose arrangement of collagenous and elastic fibers; scattered cell types; abundant ground substance Locations-- Underlying all epithelia; surrounding nerves, blood vessels, esophagus, trachea

§ B-- Reticular Tissue Fig. Spleen Loose network of R_________ and cells Forms structural supportive stroma for lymphatic organs Locations-- lymph nodes, spleen, thymus & bone marrow Fig. Spleen

§ C-- Adipose Tissue (Fat) Large, empty-looking cells dominate with thin margins; nucleus pressed against cell membrane; often very pale Functions-- Energy storage, insulation, space filled as cushioning Locations-- Subcutaneous fat beneath skin, breast, heart surface, surrounding organs

Figure 5.16b Fig. Adipose tissue

§ D-- Dense Regular CT Structure-- Mainly densely, PACKED, PARALLEL C__________FIBERS; compressed fibroblast nuclei; scanty open space and blood vessels Locations-- Tendons & ligaments 13

D-- Dense Regular CT Fig. Tendon

§ E-- Dense Irregular CT Densely packed collagen fibers running in ________ directions; scanty open space; few visible cells and blood vessels Function-- Withstands stresses applied in MANY DIFFERENT DIRECTIONS Locations-- Deeper portion of skin; capsules around organs (ex. Liver, kidney etc); sheaths around cartilages and bones.

E-- Dense Irregular CT Fig. Dermis of the skin 16

Connective tissue B. Cartilage, Bone, Blood

§ Cartilage Supportive CT with rubbery matrix Chondroblasts produce matrix, surround themselves, and become Chondrocytes No blood vessels; so diffusion must bring in nutrients & remove wastes; healing . . . 3 types of cartilage depend upon FIBER TYPES A--hyaline, B--elastic, and C--fibrocartilage

§ A-- Hyaline Cartilage Clear, glassy matrix; invisible fine dispersed collagen fibers; chondrocytes in small clusters enclosed in lacunae Supports airway, eases joint movements Locations-- Over ends of bones at movable joints; sternal ends of ribs; supportive material in larynx, trachea, bronchi and fetal skeleton

Figure 5.19b Fig. Fetal skeleton

§ B-- Elastic Cartilage Hyaline cartilage with weblike mesh of elastic fibers amid the lacunae; always has perichondrium (a sheath of C.T.) Provides flexible, elastic support Locations— Ear + Epiglottis

Figure 5.20b Fig. External ear

§ C-- Fibrocartilage Cartilage containing extensive parallel Collagen fibers; never has perichondrium; row of chondrocytes in lacunae Resists compression and absorbs shock in some joints Locations-- Pubic symphysis, menisci (pads) in knee joint, & intervertebral discs

Fig. Intervertebral disc Figure 5.21b Fig. Intervertebral disc

§ Bone (osseous tissue) Spongy bone looks spongy in appearance fills heads of long bones delicate struts of bone ALWAYS COVERED BY COMPACT BONE Compact (dense) bone looks solid No space visible to the naked eye External surfaces of ALL bones

§ Compact bone Calcified matrix in concentric lamellae around central (haversian) canal containing blood vessels osteocytes in lacunae between lamellae connected by canaliculi— delicate narrowing canals . . . Physical support; leverage for muscles; mineral storage Locations-- in skeleton

Canaliculi ? Fig. Compact bone 27

§ Blood Variety of cells and cell fragments; some with nuclei & some without RBC, WBC, platelets Found in heart and blood vessels

Fig. Blood smear 29