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 Consists of two basic elements: – Cells, and – Extra-cellular matrix (abundant) (dominant part) Fibers, and Ground substance – liquid, gel, or solid Function – Bind and/or support 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 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)

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 Polarizing microscopy picrosirius-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 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 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 Perichondrium Hayaline Cartilage

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

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

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

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

Blood RBC Neutrophils Lymphocytes Monocytes Platelets

Blood RBC Neutrophils Lymphocytes Monocytes Platelets

Blood RBC Neutrophils Lymphocytes Monocytes Platelets

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 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 Types of Connective Tissue: