Section 2, Chapter 5

Connective Tissues

Characteristics of Connective Tissues (CT)

Cells are separated by non-cellular material, called the extracellular matrix

Most connective tissues have good blood supply

Most cells divide (to recover from injury)

nucleus of cell

Extracellular matrix

Elastic Cartilage

FibroblastsSecretes protein fibers into matrix

Mast CellsSecretes histamine & heparin into blood

Mast CellFibroblast

Cell Types

Examples of fixed cells

Cells of CT may either be fixed in place (resident cells) or they may be wandering cells

Wandering cells move throughout the tissues.

Example of a wandering cell: Macrophages

Macrophages actively move about during infection phagocytizing bacteria & debris.

macrophages

The matrix of most CT contains protein fibers & a non-protein ground substance

extracellular matrix of connective tissues

Protein FibersProtein fibers are secreted by fibroblasts.

3 types of protein fibers include elastic fibers, collagen fibers, and reticular fibers

1. Collagenous fibersThick bands of protein

Collagen fibers are flexible, but only slightly elastic

They exhibit great tensile strength that resists pulling

Collagenous fibers forms the bulk of ligaments & tendons

Most abundant protein in mammals

Protein Fibers

Ligaments connect bone to bone

Tendons connect muscle to bone

2. Elastic FibersComposed of a spring-like protein, called elastin.

Elastic fibers are weaker than collagen, but exhibit elastic recoil

Elastic fibers can be easily stretched or deformed and they retain their shape.

Locations: vocal cords, respiratory tract, blood vessels

Protein Fibers

Figure 5.17 Scanning electron micrograph of collagenous fibers and elastic fibers

3. Reticular FibersConsist of thin strands of collagen fibers

Reticular fibers form an interwoven matrix, called a reticulum.

Reticular fibers fill the spleen, liver, and lymph nodes

Reticular fiber

Protein Fibers

Types of connective tissue

Loose Connective Tissue Dense Connective TissueAreolar Dense Regular C.T.Adipose Dense Irregular C.T.Reticular Elastic C.T.

Connective Tissue Proper

Specialized Connective TissueCartilageBoneBlood

Connective tissue is often divided into two categories 1. CT proper 2. Specialized CT

Areolar tissue consist of a loose network of collagen and elastic fibers produced by fibroblasts.

Areolar tissue forms delicate membranes that loosely bind organs together

Locations subcutaneous layer of skin between muscles surrounds organs

Areolar Tissue

Functions anchors skin to underlying organs holds organs in place

LocationsBeneath the skin – subcutaneous fatWithin abdominal cavity – visceral fatSurrounds kidneys & eyeballsSurface of heart

Adipose Tissue (fat)

StructurePrecursor cells resemble fibroblasts, but as they accumulate fat droplets in the cytoplasm they become adipocytes.

Functions of adipose stores energy insulation cushions organs secretes estrogens

StructureReticular CT contains fibroblasts along with a network of thin collagenous fibers arranged into a reticulum.

Locations include the framework of Spleen LiverLymph nodes

Reticular Connective Tissue

Functions of reticular CT forms the framework of some organs

reduces the flow of fluid through an organ

Dense Regular Connective Tissue

Structure:Dense Regular CT contains relatively few fibroblasts with densely packed collagenous fibers in parallel arrangement.

Functions: Great tensile strength that withstands pulling forces especially in one direction

Locations:Tendons & Ligaments

Dense CT has a poor blood supply so they are slow to heal following an injury.

Dense Irregular Connective Tissue

StructureDense Irregular CT contains fibroblasts with a dense network of interwoven collagenous fibers

FunctionsDense Irregular CT withstands pulling forces in all directions

LocationDermis of skin

Dermis (deep layer) of skin

Elastic Connective Tissue

StructureElastic CT contains fibroblasts along with a dense arrangement of elastic fibers, with a few collagen fibers.

Functions Elastic recoil

Locations Walls of larger arteries and the respiratory tract

Cartilage Overview

Functions of cartilagesProvides attachmentsProtects tissue Structural model for developing bone

General structure of cartilagesMature cartilage cells are called chondrocytes

The extracellular matrix of cartilage consists of 1. An abundance of collagen fibers 2. a gel-like ground substance 3. Lacunae = cavities containing chondrocytes

In addition, each of the three types of cartilages have unique characteristics.

Hyaline Cartilage

StructureHyaline cartilage contains very fine collagenous fibers and the ground substance gives hyaline cartilage a glossy appearance.

FunctionsHyaline cartilage provides durable protection and supports movable joints

Locations end of bones embryonic skeleton costal cartilages of the ribs end of the nose

Elastic Cartilage

StructureElastic cartilage contains a dense network of elastic fibers in its extracellular matrix in addition to the gel-like ground substance and collagen proteins.

FunctionElastic cartilage provides flexible support that helps maintain the shape of the organs.

Locations framework of external ear and portions of the larynx

Fibrocartilage

Locations within intervertebral discs meniscus of the knees pubic symphysis

FunctionFibrocartilage acts like a shock absorber

StructureHyaline cartilage contains very fine collagenous fibers and the ground substance gives hyaline cartilage a glossy appearance.

Bone

Structure Bone is composed of 1. Cells called osteocytes within lacunae (cavities) 2. Collagen fibers that offer pliability to bone 3. Mineral Salts that provide hardness

Functions 1. support and protection 2. movement 3. blood cell production

Locations skeleton of the body

BloodStructureBlood is composed of red blood cells, white blood cells, and platelets suspended in a fluid matrix, called plasma.

Functions 1. RBCs – transport gasses 2. WBCs – fight infection and remove debris 3. Platelets – blood coagulation (clotting) 4. Plasma – transports nutrients, wastes, hormones, etc.

Location Within blood vessels

Overview of Connective Tissues

End Section 2, Chapter 5