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Objectives• What is connective tissue• Types of connective tissues• Functions of connective tissues– Relation of structure and function
Tissues • Four fundamental tissues are recognized:– Epithelial tissue– Connective tissue– Muscular tissue– Nervous tissue
Connective Tissue• Consists of two basic
elements:– Cells, and– Extra-cellular matrix (abundant)
(dominant part)• Fibers, and• Ground substance
– liquid, gel, or solid
• Function– Binds and/or supports other
tissue
Connective Tissue Cells• Fibroblasts:– Secrete both fibers and ground substance of the
matrix (wandering)
Connective Tissue Cells• Plasma Cells:– Antibody secreting cells that develop from B-
Lymphocytes (wandering)
Connective Tissue Cells• Mast Cells– Produce histamine that help dilate small blood
vessels in reaction to injury (wandering)
Connective Tissue Cells• Adipocytes:– Fat cells that store triglycerides, support, protect
and insulate (fixed)
Fibroblasts• Active fibroblasts have extensions
Extensions of fibroblasts (arrow-heads) are seen with the cell or alone, depending on section plane
Fibroblasts• Active fibroblasts have extensions
Electrom micrograph of fibrocyte with cytoplasmic extensions interdigitating among collagen fibers, X 26,000
Matrix Fibers• Collagen Fibers:– Large fibers made of the protein collagen– The most abundant fibers– Promote tissue flexibility
Matrix Fibers• Elastic Fibers:– Intermediate fibers made of the protein Elastin– Branching fibers that allow for stretch and recoil
Polarizing microscopypicrosirius-stained collagen,elastic fibers are stained by Orcein
Matrix Fibers• Reticular Fibers:– Small delicate, branched fibers– Have same chemical composition of Collagen– Forms structural framework for organs such as
spleen and lymph nodes.
Matrix Ground Substance • Hyaluronic Acid:– Complex combination of polysaccharides and
proteins found in “true” or proper connective tissue
• Chondroitin sulfate:– Jellylike ground substance of cartilage, bone, skin
and blood vessels• Other ground Substances:– Dermatin sulfate, keratin sulfate, and
adhesion proteins
Types of Connective Tissue1. True (Proper) Connective Tissue– Loose Connective Tissue• Aereolar, Adipose, Reticular
– Dense Connective Tissue
2. Supportive Connective Tissue– Cartilage– Bone
3. Liquid Connective Tissue– Blood
Loose Connective Tissue• Areolar tissue–Widely distributed under epithelia
• Adipose tissue–Hypodermis, within abdomen, breasts
• Reticular connective tissue– Lymphoid organs such as lymph nodes
Areolar Connective Tissue• Structure:
– all 3 types of fibers– several types of cells– semi-fluid ground substance
• Present in:– subcutaneous layer– mucous membranes– around blood vessels, nerves
and organs• Function:
– strength, support and elasticity
Adipose Connective Tissue:• Structure:
– adipocytes; "signet ring" appearing fat cells. They store energy in the form of triglycerides (lipids)
• Present in:– subcutaneous layer– around organs– yellow marrow of long bones
• Function:– supports, protects and
insulates– serves as an energy reserve
Reticular Connective Tissue• Structure:
– fine interlacing reticular fibers
– reticular cells• Present in:
– liver, spleen and lymph nodes
• Function:– forms the framework
(stroma) of organs– binds together smooth
muscle tissue cells
Reticular Connective Tissue• Structure:
– fine interlacing reticular fibers
– reticular cells• Present in:
– liver, spleen and lymph nodes
• Function:– forms the framework
(stroma) of organs– binds together smooth
muscle tissue cells
Reticular Connective Tissue
Reticular Fibers
Collagen Fibers
Thyroid gland, Scanning electron microscopy, X 2500Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy
Types of Connective Tissue1. True (Proper) Connective Tissue– Loose Connective Tissue• Aereolar, Adipose, Reticular
– Dense Connective Tissue
2. Supportive Connective Tissue– Cartilage– Bone
3. Liquid Connective Tissue– Blood
Dense Connective Tissue• Contains more numerous and thicker fibers
and far fewer cells than loose CT
• Types:– Dense regular connective tissue• Tendons and ligaments
– Dense irregular connective tissue• Dermis of skin, submucosa of digestive tract
Dense Regular Connective Tissue• Structure:– bundles of collagen fibers
and fibroblasts• Present in:– Tendons,– Ligaments– aponeuroses
• Function:– provides strong
attachment between various structures Tendon
Dense Irregular Connective Tissue• Structure:– randomly-arranged collagen
fibers and– few fibroblasts
• Present in:– fasciae,– dermis of skin– joint capsules– heart valves
• Function:– provides strength
Dense Irregular Connective Tissue• Structure:– randomly-arranged collagen
fibers and– few fibroblasts
• Present in:– fasciae,– dermis of skin– joint capsules– heart valves
• Function:– provides strength Eyelid, Azan stain
Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy
Dense Irregular Connective Tissue• Structure:– randomly-arranged collagen
fibers and– few fibroblasts
• Present in:– fasciae,– dermis of skin– joint capsules– heart valves
• Function:– provides strength
Renal capsule, Scanning electron microscopy, X 5000
Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy
Types of Connective Tissue1. True (Proper) Connective Tissue– Loose Connective Tissue• Aereolar, Adipose, Reticular
– Dense Connective Tissue
2. Supportive Connective Tissue– Cartilage– Bone
3. Liquid Connective Tissue– Blood
Cartilage• Structure:
– Jelly-like matrix (chondroitin sulfate)
– collagen and elastic fibers– Chondrocytes (within spaces in
the matrix called lacunae)– surrounded by a membrane
(perichondrium)– has NO blood vessels or nerves
except in the perichondrium• Function:
– Collagen fibers provide strength– chondroitin sulfate provides
resilience
Perichondrium Perichondrium
Hayaline Cartilage
Hyaline Cartilage• Most abundant type• Structure:
– Fine collagen fibers embedded in a gel-type matrix
– Occasional chondrocytes inside lacunae
• Present in:– embryonic skeleton– at the ends of long bones (joints)– in the nose and in respiratory
structures• Function:
– flexible, provides support– allows movement at joints
Fibrocartilage• Structure
– bundles of collagen in the matrix that are usually more visible under microscopy
• Present in:– Intervertebral discs,– Menisci of the knee,– Pubic Symphysis,– Tendon insertion on apophyseal
hayaline cartilage• Function:
– Support and fusion– shock absorption
Elastic Cartilage• Structure– Threadlike network of
elastic fibers within the matrix
• Present in:– external ear– auditory tubes– epiglottis
• Function:– gives support,– maintains shape– allows flexibility
Elastic Cartilage
Resorcin stain selectively staining the elastic fibers of elastic cartilage tissueCells are not stained
Elastic Cartilage
1 Elastic fibers, 2 Cartilage Cells, 3 perichondrium
Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy
Types of Connective Tissue1. True (Proper) Connective Tissue– Loose Connective Tissue• Aereolar, Adipose, Reticular
– Dense Connective Tissue
2. Supportive Connective Tissue– Cartilage– Bone
3. Liquid Connective Tissue– Blood
Bone• Structure– The hardest CT– Osteocytes in small cavities- lacunae– Impregnated with calcium salts
• Types:– Spongy (cancellous)– Compact (cortical)
Bone Types• Spongy (cancellous)– Loose rods of bones– Found inside body
of bones, and ends of arms and legs
• Compact (cortical)– Tightly organized– Found in shafts of
long bones
Bone Cells• Osteoblasts:– build bone – Bone deposition
• Osteocytes:– Osteoblasts: surrounded
by the matrix they formed
• Osteoclasts:– resorb (eat) bone– Bone resorption
Types of Connective Tissue1. True (Proper) Connective Tissue– Loose Connective Tissue• Aereolar, Adipose, Reticular
– Dense Connective Tissue
2. Supportive Connective Tissue– Cartilage– Bone
3. Liquid Connective Tissue– Blood– Lymph
Summary• What is connective tissue• Structure: Consists of two basic elements:– Cells, and– Extra-cellular matrix (abundant) (dominant part)• Fibers, and• Ground substance (liquid, gel, or solid)
• Function– Binds and/or supports other tissue