connective tissues
Page 1:
Overview of Connective Tissue
Types, components, functions, locations, disorders
Prof.Dr.Cengiz Bayçu
Dept.of Histology & Embryology
2023
Page 2:
Embryonic Connective Tissue
Mesenchyme tissue
Mucous tissue
Common Connective Tissue types
Loose -areolar- connective tissue
Dense connective tissue
Irregular dense connective tissue
Regular dense connective tissue
Special Connective Tissue
Cartilage tissue
Bone tissue
Blood tissue
Adipose tissue
Lymphatic tissue
Hematopoietic (bone marrow) tissue
Adipose tissue Types
Page 3:
Connective tissue is widespread and diverse in the body
Differences in composition and amount of cells, fibers, and ground substance contribute to the diversity
Functions of connective tissue:
Repair (Fibroblast)
Support and packaging (fibers)
Transport (Blood vessels)
Defense (White blood cells, T-B Lymphocytes)
Storage (Lipid)
Page 4:
General Features of Connective Tissue
Extracellular matrix (ECM) is the major component
Main parts of the tissue:
Matrix
Cells
ECM composed of:
Protein fibers
Organic ground substance
Fluid
Page 5:
Extracellular matrix (ECM) is a three-dimensional network of extracellular macromolecules
Components of ECM:
Collagen fiber
Elastic fiber
Reticular fiber
Resident cells:
Mesenchymal cell
Macrophage
Adipocyte
Fibroblast
Page 6:
Ground substance is an amorphous gel-like substance
Components of ground substance:
Glycosaminoglycans (gAGS)
Proteoglycans
Glycoproteins
Ground substance supports cells, binds them together, and provides a medium for metabolic substance exchange
Three types of ground substance: Fluid, Semifluid, or Solid
Page 7:
Summary of connective tissue:
Highly vascular (except cartilage and tendons)
Has a nerve supply (except cartilage)
Binds together, supports, and strengthens other body tissues
Major transport system within the body
Protects and insulates internal organs (bones)
Main site of immune responses
Site of stored energy reserves (lipid-fat)
Page 8:
Connective Tissue Fibers:
Collagen fibers
Reticular fibers
Elastic fibers
Page 9:
Reticular fibers are composed of type III collagen secreted by reticular cells
Delicate reticular networks serve as the supportive stroma for various tissues and organs
Used to filter out worn-out blood cells and bacteria
Page 10:
Elastic fibers are smaller in diameter than collagen fibers and form a network
Composed of elastin and fibrillin proteins
Provide elastic properties to connective tissues
Found in organs subject to regular stretching or bending
Page 11:
Types of Connective Tissue:
Loose
Dense CT
Loose Connective Tissue:
Areolar Connective Tissue
Reticular Connective Tissue
Mucoid Tissue
Loose connective tissue is common, flexible, and facilitates transport of cells and materials
Contains fibroblasts, macrophages, plasma cells, mast cells, adipocytes, and white blood cells
Page 12:
Dense Connective Tissue:
Contains more numerous, thicker, and denser fibers than loose connective tissue
Two types: Dense regular connective tissue, Dense irregular connective tissue
Page 13:
Dense Regular Connective Tissue:
Consists of parallel arrayed bundles of type I collagen and fibroblasts
Found in tendons and ligaments
Page 14:
Dense Regular Connective Tissue (elastic):
Found in the wall of the aorta
Contains smooth muscle cells, endothelium, tunica externa, tunica media, tunica intima
Page 15:
Dense Irregular Connective Tissue:
Densely packed collagen fibers in perpendicular bundles
Resists tension in many directions and provides mechanical support
Found in the dermis of the skin, heart valves, perichondrium, and periosteum
Page 16:
Mucoid Tissue:
Principal component of the fetal umbilical cord (Wharton's jelly)
Gelatinous with sparse collagen fibers and scattered fibroblasts
Examples of connective tissue:
Blood tissue
Bone and Cartilage
Bone Marrow
Page 17:
Cells in Connective Tissue:
Fibroblasts
Adipose (fat) cells
Tissue Macrophages
Mast cells
Lymphocytes & Plasma Cells
Leukocytes
Fixed cells (permanent residents) derived from hematopoietic stem cells
Free cells (transient cells)
Page 18:
Connective Tissue Cells named according to their function:
-blast: produce matrix
-cyte: maintain matrix; mature cells
-clast: destroy matrix
Examples of connective tissue cells:
Fibroblast, Fibrocyte, Fibroclast
Osteoblast, Osteocyte, Osteoclast
Chondroblast, Chondrocyte, Chondroclast
Page 19:
Connective Tissue Cells
Fibroblasts
Most common cells in connective tissue proper
Produce and maintain extracellular components
Large flat cells with branching processes
Macrophages
Develop from white blood cells (monocytes)
Surround and engulf material by phagocytosis
Mast Cells
Originate from bone marrow
Release bioactive substances important in inflammatory response, immunity, and tissue repair
Produce histamine, heparin, and chemotactic factors
Adipocytes
Store triglycerides
Plasma cells
Lymphocyte-derived, antibody-producing cells
Play a role in immune response
Leukocytes
White blood cells located in connective tissue
Derived from circulating blood cells
Enter connective tissue during inflammation
Page 20:
Fibroblasts
Most common cells in connective tissue proper
Synthesize extracellular matrix, collagen, elastin fibers, and growth factors
Play a major role in wound healing and fiber formation
Secrete collagenase enzymes
Page 21:
Macrophages
Highly developed phagocytic ability
Specialize in turnover of protein fibers and removal of debris
Abundant at sites of inflammation
Derived from bone marrow precursor cells called monocytes
Important in repair and inflammation after tissue damage
Page 22:
T-Lymphocytes
Responsible for cellular immunity
Distinguished by the presence of a T-cell receptor on the cell surface
Two main types: helper T-cells and killer T-cells
Helper T-cells stimulate B-cells to produce antibodies
Killer T-cells directly attack and kill invading pathogens and infected/cancerous cells
Page 23:
B-Lymphocytes
Responsible for humoral immunity
Produce and secrete antibodies
Stimulated B-lymphocytes transform into plasma cells
Humoral immunity mediated by macromolecules in extracellular fluids
Page 24:
Plasma Cells
Derived from B-lymphocytes
Responsible for specific antibody production
Nucleus is generally spherical but eccentrically placed
Antibody molecules bind to target antigens and neutralize or destroy them
Page 25:
Mast Cells
Release bioactive substances important in inflammatory response, immunity, and tissue repair
Secretions include heparin, histamine, serine proteases, chemotactic factors, and cytokines
Found in skin, peritoneal cavity, and mucosa of digestive and respiratory tracts
Page 26:
Adipocytes
Fat cells found in connective tissue of many organs
Specialized for storage of lipid or production of heat
Adipose connective tissue cushions and insulates organs
Page 27:
B-Lymphocytes
Antibody production
Mast Cells
Secretion and dilation
Cell types and their function in allergy
Allergen taken up by antigen-presenting cells (APC) and presented to T-cells
T-cells activate B-cells to release antibodies (IgE)
IgE binds to mast cell receptors
Second exposure to allergen causes release of IgE, histamine, etc. from mast cells
Results in edema, itching, sneezing
Page 28:
Biochemistry of Mast Cell Secretion
Mast cell secretion triggered by reexposure to antigens/allergens
IgE antibodies bind to mast cell surface receptors
Cross-linking of IgE receptors activates adenylate cyclase and leads to exocytosis of granules
Page 29:
Semisolid Cartilage
Dense network of collagen and elastic fibers embedded in chondroitin sulfate
Can withstand more stress than dense and loose connective tissue
Collagen fibers make the tissue strong, chondroitin sulfate makes it resilient
Page 30:
Cartilage types:
Hyaline cartilage:
Description: Amorphous but firm matrix with collagen fibers forming an imperceptible network; chondroblasts produce the matrix and mature into chondrocytes in lacunae.
Function: Supports and reinforces, serves as a resilient cushion, 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.
Elastic cartilage:
Description: Similar to hyaline cartilage, but with more elastic fibers in the matrix.
Function: Maintains the shape of a structure while allowing great flexibility.
Location: Supports the external ear (pinna), epiglottis.
Fibrocartilage:
Description: Matrix similar to hyaline cartilage but less firm, with thick collagen fibers.
Function: Tensile strength allows it to absorb compressive shock.
Location: Intervertebral discs, pubic symphysis, discs of knee joint.
Page 31:
Compact bone:
Components: Osteons, osteonic canals, blood vessels, periosteum.
Spongy bone:
Components: Trabeculae, canaliculi, lacunae (space), osteocytes.
Yellow marrow, red marrow, blood vessels, nerves, endosteum, periosteum.
Page 32:
Gingival abscess: Inflammation with fibrous capsulation by connective tissue.
Skin abscess: Inflammation.
Inflammation: Complex biological response of body tissues to harmful stimuli, involving immune cells, blood vessels, and molecular mediators.
Leukocytes: Wandering cells in connective tissue, derived from circulating blood cells, increase greatly during inflammation.
Page 33:
Steps in tissue injury repair:
Hemostasis: Formation of a scab, red blood cells, platelets, clot.
Inflammation: Macrophages, neutrophils, granulation tissue.
Proliferation: Fibroblasts, collagen fibers, myofibroblasts.
Remodeling.
Page 34:
Regenerative capacity of connective tissue observed in organs damaged by ischemia, inflammation, or traumatic injury.
Dense irregular scar tissue fills spaces left after injuries in tissues with poor or no cell division.
Healing of surgical incisions and wounds depends on activity and growth of fibroblasts.
Page 35:
Connective tissue disorders:
Causes: Genetics (heritable disorders), non-hereditary autoimmune causes (exposure to toxic chemicals, ultraviolet light, inadequate nutrition, infections).
Ehlers Danlos Syndrome: Genetic disease with faulty assembly of collagens, hyperextensible skin, hypermobile joints, weakness in blood vessels.
Page 36:
Marfan Syndrome:
Description: Variable, autosomal dominant disorder of connective tissue affecting the cardiovascular system, eyes, and skeleton.
Features: Reduced elasticity in skin and lungs, skeletal defects, cardiovascular complications (aneurysm, valve prolapse).
Symptoms: Tall stature, long limbs, blurred vision, weakened aortic walls.
Page 37:
Cardiovascular complications of Marfan Syndrome:
Cardiomyopathy: Enlarged and weakened heart muscle, may progress to heart failure.
Aneurysm at aortic root: Bulging or dilation in the wall of the blood vessel, at risk of rupturing and causing fatal bleeding.
Page 38:
Treatment of aneurysm:
Medical treatment and/or surgery to lower blood pressure and reduce tension.
Endovascular grafting as a minimally invasive method to treat aortic aneurysm.
Page 39:
Cerebral aneurysm: Weakening in the vascular layers of the brain, risk factors include high blood pressure, smoking, stress, and excess weight.
Diagnosis of a brain aneurysm: Computed tomography (CT) and MRI, subarachnoid hemorrhage on CT, aneurysm on MRI angiography.
Page 40:
References provided.
Page 41:
Thank you for attention.