Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Connective Tissue

A.General Characteristics – bind, support, protect, serve as frameworks, fill spaces, store fat, produce blood cells, protect against infection, and help repair tissue damage. – Unlike epithelial tissues, connective tissues have an abundance of extracellular matrix, or intercellular material composed of protein fibers and ground substance; consistency varies. – Connective tissue can divide and most have a good blood supply (except cartilage). 2

Fig 5.11 Fibroblast cells 3 The fibroblast is the most common cell type, and is a fixed, star-shaped cell that secretes fibers and is large in size. 3 major Cell Types

Macrophage 4 Wandering macrophages function as scavenger cells and defend against infection and foreign particles by phagocytosis.

Mast cell 5 Fig 5.13 Mast cells are large, fixed, and are located near blood vessels where they release heparin (anticoagulant) and histamine (promotes inflammation).

– Connective Tissue Fibers a.Strong bundles of collagenous fibers (white fibers), made of the protein collagen, add strength for holding body parts together. b.Elastic fibers (yellow fibers), made of the protein elastin, are stretchy and add flexibility to certain types of connective tissues. c.Reticular fibers are thin collagenous fibers that form supportive networks in a variety of tissues. – Classified as connective tissue proper (loose and dense) and specialized connective tissue (supportive and fluid). 6

CONNECTIVE TISSUE FIBERS Collagenous Fibers Reticular Fibers Elastic Fibers

Types of Connective Tissues 1.True (proper) Connective Tissue a.Loose Connective Tissue b.Dense Connective Tissue 2.Supportive Connective Tissue a.Cartilage b.Bone 3.Fluid Connective Tissue a.Blood

1. True (Proper) Connective Tissue A.Loose Connective Tissue – fibers are smaller and arranged in loose, random arrays 1.Areolar 2.Adipose 3.Reticular

Copyright © 2010 Pearson Education, Inc. Figure 4.8a Connective tissues. (a) Connective tissue proper: loose connective tissue, areolar Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells. Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid. Location: Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries. Photomicrograph: Areolar connective tissue, a soft packaging tissue of the body (300x). Epithelium Lamina propria Fibroblast nuclei Elastic fibers Collagen fibers

Areolar

Copyright © 2010 Pearson Education, Inc. Figure 4.7 Areolar connective tissue: A prototype (model) connective tissue. Macrophage Fibroblast Lymphocyte Fat cell Mast cell Neutrophil Capillary Cell typesExtracellular matrix Fibers Collagen fiber Elastic fiber Reticular fiber Ground substance

Areolar

Copyright © 2010 Pearson Education, Inc. Adipose Tissue (b) Connective tissue proper: loose connective tissue, adipose Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet. Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs. Location: Under skin in the hypodermis; around kidneys and eyeballs; within abdomen; in breasts. Photomicrograph: Adipose tissue from the subcutaneous layer under the skin (350x). Nucleus of fat cell Vacuole containing fat droplet Adipose tissue Mammary glands

Adipose Tissue

Copyright © 2010 Pearson Education, Inc. Reticular Tissue (c) Connective tissue proper: loose connective tissue, reticular Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network. Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages. Location: Lymphoid organs (lymph nodes, bone marrow, and spleen). Photomicrograph: Dark-staining network of reticular connective tissue fibers forming the internal skeleton of the spleen (350x). Spleen White blood cell (lymphocyte) Reticular fibers

RETICULAR CONNECTIVE TISSUE reticular fibers (argyrophilic)

1. True (Proper) Connective Tissue B. Dense Connective Tissue 1.Dense regular: Tendons and ligaments 2.Dense irregular: Dermis of skin, submucosa of digestive tract * contains more numerous and thicker fibers and far fewer cells than loose connective tissue

Copyright © 2010 Pearson Education, Inc. Dense regular (d) Connective tissue proper: dense connective tissue, dense regular Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast. Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction. Location: Tendons, most ligaments, aponeuroses. Photomicrograph: Dense regular connective tissue from a tendon (500x). Shoulder joint Ligament Tendon Collagen fibers Nuclei of fibroblasts

Dense Regular

Copyright © 2010 Pearson Education, Inc. Dense Irregular (e) Connective tissue proper: dense connective tissue, dense irregular Description: Primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast. Function: Able to withstand tension exerted in many directions; provides structural strength. Location: Fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract. Photomicrograph: Dense irregular connective tissue from the dermis of the skin (400x). Collagen fibers Nuclei of fibroblasts Fibrous joint capsule

Dense Irregular

SCANNING EM OF COLLAGEN FIBER BUNDLES

2. Supportive Connective Tissue A.Cartilage: Jelly-like matrix (chondroitin sulfate) containing collagen and elastic fibers and chondrocytes surrounded by a membrane called the perichondrium. unlike other tissue, has NO blood vessels or nerves except in perichondrium strength of cartilage due to collagen fibers and the resilience is due to the presence of chondroitin sulfate. Chondrocytes occur within spaces in the matrix called lacunae. Types –Hyaline –Elastic –Fibrocartilage

Types of Cartilage

Copyright © 2010 Pearson Education, Inc. Hyaline Cartilage (g) Cartilage: hyaline Description: Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae. Function: Supports and reinforces; has resilient cushioning properties; resists compressive stress. Location: Forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx. Photomicrograph: Hyaline cartilage from the trachea (750x). Costal cartilages Chondrocyte in lacuna Matrix

Copyright © 2010 Pearson Education, Inc. Elastic Cartilage (h) Cartilage: elastic Description: Similar to hyaline cartilage, but more elastic fibers in matrix. Function: Maintains the shape of a structure while allowing great flexibility. Location: Supports the external ear (pinna); epiglottis. Photomicrograph: Elastic cartilage from the human ear pinna; forms the flexible skeleton of the ear (800x). Chondrocyte in lacuna Matrix

Copyright © 2010 Pearson Education, Inc. Fibrocartilage (i) Cartilage: fibrocartilage Description: Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate. Function: Tensile strength with the ability to absorb compressive shock. Location: Intervertebral discs; pubic symphysis; discs of knee joint. Photomicrograph: Fibrocartilage of an intervertebral disc (125x). Special staining produced the blue color seen. Intervertebral discs Chondrocytes in lacunae Collagen fiber

Copyright © 2010 Pearson Education, Inc. 2. Supportive Connective Tissue B. BoneCompact Description: Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized. Function: Bone supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis). Location: Bones Photomicrograph: Cross-sectional view of bone (125x). Lacunae Lamella Central canal

Copyright © 2010 Pearson Education, Inc. 2. Supportive Connective Tissue B. BoneCompact & Spongy

Bone Compact Dense, strong, support, protects all bones Stores calcium Found in long bones and forms external wall of all bones Spongy Porous (holes) Provides structural support and flexibility without added weight Where bone marrow develops Fills inner layer of bones

Copyright © 2010 Pearson Education, Inc. 3. Fluid Connective Tissue-Blood (k) Others: blood Description: Red and white blood cells in a fluid matrix (plasma). Function: Transport of respiratory gases, nutrients, wastes, and other substances. Location: Contained within blood vessels. Photomicrograph: Smear of human blood (1860x); two white blood cells (neutrophil in upper left and lymphocyte in lower right) are seen surrounded by red blood cells. Neutrophil Red blood cells Lymphocyte Plasma