Connective Tissue
Mamoun Kremli
Al-Maarefa College
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
• Connective tissue is clearly different from
neighboring tissues
Connective Tissue
• Connective tissue is clearly different from
neighboring tissues
Connective Tissue
• Connective tissue is clearly different from
neighboring tissues
Connective Tissue Cells
• Fibroblasts:
– Secrete both fibers and ground substance of the
matrix (wandering)
Connective Tissue Cells
• Macrophages:
– Phagocytes that develop from Monocytes
(wandering or fixed)
Connective Tissue Cells
• Plasma Cells:
– Antibody secreting cells that develop from BLymphocytes (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)
Connective Tissue Cells
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
• Elastic Fibers
• Reticular Fibers
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
picrosirius-stained collagen,
elastic fibers are stained by Orcein
Polarizing microscopy
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 Fibers
Collagen
Elastin
Elastic and Collagen Fibers
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 Tissue
1. 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
Adipose Connective Tissue
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 Connective Tissue
Reticular Fibers
Collagen Fibers
Thyroid gland, Scanning electron microscopy, X 2500
Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy
Types of Connective Tissue
1. 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 Regular Connective Tissue
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 Tissue
1. 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
Hayaline Cartilage
Perichondrium
Perichondrium
Cartilage
• Types:
– Hyaline cartilage
– Fibro-cartilage
– Elastic 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
Hyaline Cartilage
Hyaline Cartilage
• Covers articular surfaces
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
Fibrocartilage
Fibrocartilage
Picrosirius-Hematoxilin stain of fibrocartilage, with abundant collagen fibers
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 tissue
Cells 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 Tissue
1. 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 Structure
Cancellous Bone
Cortical Bone
Bone Structure
Bone Structure
Bone Structure
Bone Structure
Section of a Haversian system (Osteone)
Bone Cells
• Osteoblasts:
– build bone
– Bone deposition
• Osteocytes:
– Osteoblasts:
surrounded by the
matrix they formed
• Osteoclasts:
– resorb (eat) bone
– Bone resorption
Bone Cells
• Osteoblasts:
– build bone
• Osteocytes:
– osteoblasts surrounded by matrix they formed
Bone Cells
• Osteoclasts:
– Resorb (eat) bone
Bone Cells
• Osteoclasts:
– Resorb (eat) bone
Types of Connective Tissue
1. 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
Blood
•
•
•
•
•
RBC
Neutrophils
Lymphocytes
Monocytes
Platelets
Blood
•
•
•
•
•
RBC
Neutrophils
Lymphocytes
Monocytes
Platelets
www.lab.anhb.uwa.edu.au
Blood
•
•
•
•
•
RBC
Neutrophils
Lymphocytes
Monocytes
Platelets
www.lab.anhb.uwa.edu.au
Blood
•
•
•
•
•
RBC
Neutrophils
Lymphocytes
Monocytes
Platelets
www.lab.anhb.uwa.edu.au
Blood
•
•
•
•
•
RBC
Neutrophils
Lymphocytes
Monocytes
Platelets
www.lab.anhb.uwa.edu.au
Lymph
Contains lymphatic fluid and WBC
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
Summary
Types of Connective Tissue:
1. True (Proper) Connective Tissue
– Loose CT (areolar, adipose, reticular)
– Dense CT (regular, irregular)
2. Supportive Connective Tissue
– Cartilage
– Bone
3. Liquid Connective Tissue
– Blood
– Lymph