Connective Tissue PDF

Raparin University College o Science MLS department Histology 2nd Stage Connective tissues Prepared by Dr. Shahla M. Abdullah 3rd lecture Connective Tissue Connective Tissue, an essential and diverse tissue type in the h...

Raparin University College o Science MLS department Histology 2nd Stage Connective tissues Prepared by Dr. Shahla M. Abdullah 3rd lecture Connective Tissue Connective Tissue, an essential and diverse tissue type in the human body that supports, connects, or separates different types of tissues and organs in the body. Unlike other tissues, connective tissue is characterized by an abundant extracellular matrix (ECM), which surrounds its cells. The ECM is rich in fibers and ground substance, giving connective tissue its unique structural properties Main characteristics of CT Highly Vascularized: Most connective tissues, except for cartilage, have a rich blood supply, enabling them to repair and regenerate well. Variety in Composition: Connective tissue varies widely in consistency, ranging from fluid (blood) to firm (bone) to elastic (tendons and ligaments). Diverse Functions: Depending on its type, connective tissue can be involved in mechanical support, nutrient transport, storage, and immune responses. Components of Connective Tissue: Connective tissue is composed of three main components that work together to form a functional tissue: A. Cells: Various cells are found in different types of connective tissues. Each type of cell serves a specific role, depending on the function of the tissue: 1.Fibroblast 2. Mesenchymal cells 3. Adipocytes 4. Chondrocytes 5. Osteocytes and Osteoblasts 6. Immune cells (Macrophage, Mast cell, plasma cells)  1. Fibroblast cell Fibroblasts: The most abundant cells in connective tissue. These cells are responsible for producing and secreting the fibers (collagen, elastin) and the ground substance of the ECM. Fibroblasts are particularly active during tissue repair and wound healing due to their ability to produce structural proteins, regulate the inflammatory response, and promote tissue regeneration 2. Mesenchymal cells Mesenchymal cells are multipotent stem cells found primarily in the bone marrow, but also in adipose tissue, umbilical cord blood, and placenta. They can differentiate into various cell types, including bone, cartilage, and fat cells. Mesenchymal cells play a key role in tissue repair, regeneration, and immunomodulation, helping to control inflammation. Their ability to regenerate damaged tissues makes them important in regenerative medicine and potential therapies for autoimmune diseases. They also produce components of the extracellular matrix, contributing to tissue structure and integrity. 3. Adipocytes Adipocytes, or fat cells, are specialized cells that store lipids as triglycerides, serving as a significant energy reservoir. They also secrete hormones like leptin and adiponectin, which regulate metabolism and immune responses. Dysregulation of adipocyte function is linked to obesity, metabolic syndrome, and cardiovascular disease, making their study crucial for understanding and addressing metabolic disorders. Type of Adipocytes White Adipocytes: store and hormone secretion. Found in subcutaneous fat (beneath the skin) and Visceral fat (around internal organs). Brown Adipocytes: Generate heat through thermogenesis. Deposits in the neck, shoulders, and along the spine (especially in infants). Beige Adipocytes: have properties of both white and brown fat and can switch functions depending on physiological condition. Found in Intermixed within white adipose tissue, particularly in the abdominal area. 4. Chondrocytes Chondrocytes: Cells found in cartilage. They produce and maintain the cartilaginous matrix composed of collagen and proteoglycans. These cells exist in small spaces called lacunae. Chondrocyte dysfunction is associated with diseases like osteoarthritis, where cartilage degradation exceeds repair.  5. Osteocytes and Osteoblasts Osteocytes and Osteoblasts: Bone Remodeling and Mineralization Osteocytes: Mature bone cells housed in lacunae that maintain bone homeostasis by regulating the mineral content. Osteoblasts: Bone-forming cells responsible for osteoid production and mineral deposition, critical for bone growth and repair. Clinical Relevance: Dysregulated osteocyte and osteoblast activity is implicated in disorders like osteoporosis and osteopetrosis, where bone turnover is abnormal Osteocytes and Osteoblasts 6. Immune Cells: Immune Cells: These include Macrophages (which engulf pathogens and debris), Mast cells (which release histamine during allergic reactions), and Plasma cells (which produce antibodies). Oher Leukocytes Macrophages Macrophages originate from monocytes and are irregularly shaped cells with branching projections, capable of phagocytosing bacteria and debris. Fixed Macrophages: Located in specific tissues (e.g., alveolar macrophages in the lungs, splenic macrophages in the spleen). They release chemicals that activate the immune response and attract wandering immune cells upon encountering foreign materials. Wandering Macrophages: Move throughout tissues to sites of infection or inflammation, where they engulf bacteria, foreign particles, and damaged cells.  Mast cells These small, mobile cells have granule-filled cytoplasm and are typically located near blood vessels. They secrete heparin to inhibit blood clotting and histamine to dilate blood vessels, increasing blood flow Plasma cells Plasma cells are small cells that develop from B lymphocytes. They secrete antibodies that attack or neutralize foreign substances in the body. Plasma cells are typically found in the intestinal walls, spleen, and lymph nodes  Leukocytes in Connective Tissues 1.Neutrophils: The most abundant white blood cells that phagocytize bacteria and fungi, serving as first responders to infections. 2.Dendritic Cells: Capture and present antigens to T cells, linking innate and adaptive immunity. 3.Natural Killer (NK) Cells: Recognize and kill virus-infected and tumor cells without prior sensitization. 4.T Lymphocytes (T cells): 1. Helper T Cells: Assist other immune cells. 2. Cytotoxic T Cells: Kill infected cells B. Fibers: The extracellular matrix of connective tissue contains three main types of protein fibers that give it structural integrity and functional specialization: 1. Collagen Fibers 2. Elastic Fibers 3. Reticular Fibers C. Ground Substance: The ground substance is a gel-like material that fills the space between cells and fibers. It plays several critical roles: Support: Provides structural integrity and helps resist compression. Medium for Exchange: Facilitates the diffusion of nutrients and waste between blood vessels and cells. Composition: It is composed of proteoglycans, glycoproteins, and water, which help retain moisture and provide resilience  Raparin University College o Science MLS department Histology 2nd Stage Classification of Connective tissues Prepared by Dr. Shahla M. Abdullah 4th lecture Classification of Connective tissue ▪ Connective Tissue Proper Connective tissue proper includes a variety of connective tissues characterized by a mixture of different cell types and extracellular protein fibers suspended in a viscous ground substance. Characteristics: Typically contains a higher content of protein fibers. Varies in the number and types of cells, as well as the properties and proportions of fibers and ground substance. Main Function: The primary role of connective tissue proper is to bind cells and tissues together, forming organs and organ systems.  Loose connective tissue Loose connective tissue is a fundamental type of connective tissue that provides structural support and flexibility throughout the body. It serves as a filler material between organs and tissues, playing a crucial role in maintaining the integrity of the body Characteristics: Structure: Loose connective tissue has a loosely organized structure, with abundant ground substance and fewer collagen fibers compared to dense connective tissue. This arrangement allows for greater flexibility and movement. Components: Composed of: Fibroblasts: The main cells that produce fibers and ground substance. Macrophages: Immune cells that help in defense and tissue repair. Mast Cells: Involved in inflammatory responses. Adipocytes: Fat cells that store energy and provide Thermal insulation  Types of Connective Tissue Proper A. Loose Connective Tissue: 1.Areolar Tissue: A flexible, gel-like matrix with various cell types and all three fiber types (collagen, elastic, and reticular). Provides support and elasticity; fills spaces between organ. Seen beneath the skin and surrounding organs.  2. Adipose C T Adipose Tissue: Composed primarily of adipocytes (fat cells) with a minimal matrix. Stores energy, provides insulation, and cushions organs. Seen under the skin, around organs, and in bone marrow  3. Reticular CT: Reticular Tissue: Composed of a network of reticular fibers and cells. Supports the framework of organs, especially those involved in immune responses. Found in lymph nodes, spleen, and bone marrow.  Types of Connective Tissue Proper B. Dense Connective Tissue Dense connective tissue is characterized by a high concentration of collagen fibers, which provide strength and resistance to stretching 1. Dense Regular Connective Tissue: Composed of closely packed collagen fibers arranged in parallel. Provides high tensile strength in one direction. Found in tendons (connecting muscles to bones) and ligaments (connecting bones to each other). 2. Dense Irregular CT Dense Irregular Connective Tissue: Contains collagen fibers arranged irregularly. Provides strength and support in multiple directions. Found in dermis of the skin and protective coverings of organs.  3. Elastic Connective Tissue Elastic Connective Tissue: Contains a high proportion of elastic fibers. Provides elasticity and allows tissues to recoil after stretching. found in the walls of large arteries, bronchial tubes, and some ligaments. Raparin University College o Science MLS department Histology 2nd Stage Supporting Connective Tissue Prepared by Dr. Shahla M. Abdullah 5th lecture ▪ Supporting Connective Tissue Supporting connective tissue provides a strong and durable framework that protects and supports soft body tissues. Characteristics: Contains many protein fibers. The ground substance ranges from semisolid to solid. Types: Cartilage: Has a semisolid extracellular matrix. Bone: Contains a solid extracellular matrix. Types of Supporting Connective Tissue 1. Cartilage Cartilage is a specialized, resilient and flexible connective tissue that can withstand compression and tension. It has a gel-like extracellular matrix, rich in collagen and elastin fibers, and contains specialized cells known as chondrocytes Chondrocytes housed in lacunae, which secrete a gel-like extracellular matrix containing collagen fibers for tensile strength. Chondrocytes produce chemicals that inhibit blood vessel formation, making cartilage avascular. Nutrient and waste exchange occurs via diffusion. Cartilage withstands mechanical stress without distortion and is found in areas requiring support and flexibility, like the nose tip and outer ear (auricle).  Cartilage is usually covered by the perichondrium, which has two layers: 1.Outer Fibrous Layer (fibrous perichondrium): Dense irregular connective tissue providing protection and mechanical support. 2.Inner Cellular Layer (chondrogenic perichondrium): Contains chondroblasts and stem cells essential for cartilage growth and maintenance.  Cartilage makes most of the embryonic skeleton. It is gradually replaced by bones during embryonic development and after birth. It persist in growth plates of the bones and allows bone to increase in length. I. Hyaline Cartilage: Most abundant type, provides a smooth, glassy appearance. It contains usually invisible fine collagen fibers chondrocytes are found in lacunae, within the firm but flexible matrix Function: Reduces friction between bony surfaces, provides support while allowing flexibility. Location: Articular surfaces of joints, costal cartilage (ribs), nose, larynx, and trachea. II. ELASTIC CARTILAGE Elastic cartilage contains a dense network of highly branched elastic fibers, making it more flexible than hyaline cartilage. Chondrocytes are embedded in a web-like mesh of elastic fibers within the extracellular matrix, particularly dense around the lacunae. The perichondrium is present. Function Provides rigidity with even more flexibility than hyaline cartilage maintains shape of certain structures Location External ears, epiglottis, auditory tubes  III. FIBROCARTILAGE Structure Have collagen fibers similar to those in hyaline cartilage which are arranged in thick bundles between large chondrocytes. intermediate between dense connective tissue and hyaline cartilage. Lack perichondrium Function flexible and capable of withstanding considerable pressure (strongest of all cartilage) connects structures subjected to great pressure Act as shock absorber Location Intervertebral disks, symphysis pubis, articular disks (e g knee and temporomandibular joints) Growth Patterns of Cartilage Cartilage grows in two ways: Interstitial Growth and Appositional Growth. A. Interstitial Growth: a) Chondrocytes housed in lacunae undergo mitotic cell division. b) The two new cells occupy a single lacuna c) Cells synthesize and secrete new cartilage matrix; they are pushed apart and now reside in their own lacunae d) The new individual cells within their own lacunae are called chondrocytes. e) new matrix has been produced internally, and thus interstitial growth has occurred. B. Appositional Growth: A growth that occurs later in life after full maturity due to injury or healing. This growth occurs only at the periphery of the tissue. a) chondroblasts, located at the periphery of the old cartilage, begin to produce and secrete new cartilage matrix, they are pushed apart and become chondrocytes, each occupying its own lacuna. b) The new matrix has been produced peripherally, and thus appositional growth has occurred. During early embryonic development, both interstitial and appositional cartilage growth occur simultaneously. The interstitial growth declines rapidly as the cartilage matures because the cartilage becomes semi- rigid, and it is no longer able to expand. Functions of Cartilage: Provides a smooth surface for joint movement. Supports soft tissues and shapes structures. Absorbs shock and distributes loads B. Bone Bone is a specialized connective tissue composed of intercellular calcified material, the bone matrix, and three cell types: osteocytes, osteoblasts and osteoclasts. Because metabolites are unable to diffuse through the calcified matrix of bone, the exchanges between osteocytes with one another and with blood capillaries depend on communication through minute passageways in the matrix called canaliculi which are defined as thin, cylindrical spaces that perforate the matrix.  The matrix of bone has organic and inorganic component. The organic portion (collagen fibers and different protein, carbohydrate molecules), makes about one third of the dry weight of bone. The inorganic portion make up two third of its dry weight. It is a mixture of calcium and phosphorus. (hydroxyapatite). The strength and rigidity of the mineralized matrix enable bones to support and protect other tissues and organs of the body.  The organic portion of the matrix imparts tensile strength while the inorganic portion imparts compressional strength. All bones (except surfaces of joints of long bones) are covered by dense irregular connective tissue called periosteum. Periosteum serve as a site for attachment of ligaments and tendons. And an inner cellular layer, composed of fibroblast-like cells called osteoprogenitor cells, and endosteum which lines all internal cavities within the bone. Bone has rich vascular supply and is site for active metabolic activity Bone serves many functions including support, protection, storage ( triglyceride), hemopoiesis Cell Types of Bone 1. Osteoprogenitor cells: Stem cells derived from mesenchyme. When they divide, they produce another stem cell and a "committed cell" that matures to become an osteoblast. These stem cells are located in both the periosteum and the endosteum. 2. Osteoblasts: Formed from osteoprogenitor stem cells, Often, osteoblasts are positioned side by side on bone surfaces. Active osteoblasts exhibit a somewhat cuboidal shape and have abundant rough endoplasmic reticulum and Golgi apparatus, reflecting the activity of these cells. Osteoblasts perform the important function of synthesizing and secreting the initial semisolid organic form of bone matrix called osteoid Osteoid later calcifies as a result of salt crystal deposition. As a consequence of this mineral deposition on osteoid, osteoblasts become entrapped within the matrix they produce and secrete, and thereafter they differentiate into osteocytes. 3. Osteocytes Mature bone cells derived from osteoblasts that have become entrapped in the matrix they secreted. They reside in small spaces within the matrix called lacunae Osteocytes maintain the bone matrix and detect mechanical stress on a bone. If stress is detected, osteoblasts are signaled, and it may result in the deposition of new bone matrix at the surface. 4. Osteoclasts Large, multinuclear, phagocytic cells. They appear to be derived from fused bone marrow cells similar to those that produce monocytes. These cells exhibit a ruffled border where they contact the bone, which increases their surface area exposure to the bone. An osteoclast is often located within or adjacent to a depression or pit on the bone surface called a resorption lacuna (Howship’s lacuna). Osteoclasts are involved in an important process called bone resorption that takes place as follows: 1. Osteoclasts secrete hydrochloric acid, which dissolves the mineral parts (calcium and phosphate) of the bone matrix, while lysosomes within the osteoclasts secrete enzymes that dissolve the organic part of the matrix. 2. The release of the stored calcium and phosphate from the bone matrix is called osteolysis. 3. The liberated calcium and phosphate ions enter the tissue fluid and then the blood. 4. Osteoclasts remove matrix and osteoblasts add to it, maintaining a delicate balance. 5. If osteoclasts resorb the bone to remove calcium salts at a faster rate than osteoblasts produce matrix to stimulate deposition, bones lose mass and become weaker; in contrast, when osteoblast activity outpaces osteoclast activity, bones have a greater mass. Compact bone The compact bone forms the dense outer shell of bones and is characterized by having a high ratio of matrix to space. Its fundamental structural unit is the osteon (or Haversian system), which is organized into the following components: 1. Lamellae: Concentric rings of mineral-rich extracellular matrix, mainly composed of calcium and phosphates, providing the bone with its rigidity. 2. Lacunae: Small spaces nestled between the lamellae, each containing an osteocyte (mature bone cell). 3. Canaliculi: Minute canals branching from each lacuna, allowing for nutrient and waste exchange between osteocytes. 4. Perforating Canals (Volkmann’s canals): Channels that contain blood vessels and nerves, connecting to the central canals. Additional structural elements include: Circumferential Lamellae: These rings line the outer (periosteum) and inner (endosteum) surfaces of the bone, forming during bone development. Interstitial Lamellae: Remnants of old osteons partially absorbed during bone remodeling, often appearing incomplete without a central canal. Spongy bone Also called cancellous or trabecular bone). appears more porous, like a sponge, forms an open lattice of narrow plates of bone, called trabeculae. spongy bone is located internally, primarily within the epiphyses. Contain more space than matrix Instead of being completely solid, spongy bone contains spaces, and the bone connective tissue forms a latticework structure called trabeculae which contain lamellae, osteocytes, lacunae, and canaliculi Spaces between trabeculae are filled with red bone marrow which is site for hemopoiesis Although lighter than compact bone, spongy bone is still designed for strength Like braces used for support in buildings, the solid portions of spongy bone follow lines of stress Ossification: Refers to the formation and development of bone connective tissue. Ossification begins in the embryo and continues as the skeleton grows during childhood and adolescence. Endochondral and intramembranous are the two methods of ossification in the fetus and young children. A. Endochondral Ossification: the most common bone formation process, which involves the replacement of hyaline cartilage with bone. B. Intramembranous Ossification: the process of bone formation in the flat bones of the skull, where bone forms directly within mesenchyme arranged in sheet-like layers that resemble membranes. Functions of Bone: 1.Provides structural support and shape to the body. 2.Protects vital organs (e.g., skull protects the brain; rib cage protects the heart and lungs). 3.Stores essential minerals (calcium and phosphorus) and facilitates the production of blood cells (hematopoiesis) in the bone marrow. Raparin University College o Science MLS department Histology 2nd Stage Fluid Connective Tissue Prepared by Dr. Shahla M. Abdullah 6th lecture ▪ Fluid connective proper Fluid connective tissue is a specialized type of connective tissue characterized by a liquid matrix, allowing for the transport of nutrients, gases, hormones, and waste products throughout the body. The two main types are blood and lymph. ❖ Blood is a fluid connective tissue Blood: is about 8% body weight in adult (5.5L in man), pH is slightly basic (7.35-7.45), Temperature is (38 C). Blood is 5 times thicker than water and more resistant to flow. In the arteries blood is a brighter red than in the veins. The science that deals with blood is called Hematology. Composition of blood A. Plasma: liquid extracellular matrix, composed of water, dissolved & suspended molecules, that flow within the closed circulatory system. B. Formed elements: consist of blood cells and platelets (tiny fragments of bone marrow cells) and both have a definite structure and shape Functions of blood Blood has three main functions: transport, protection and regulation. 1. Blood transport gases (O2 and CO2), nutrients, waste products, and hormones 2. Blood contains leukocytes, plasma proteins, and various molecules that help protect the body against harmful substances. 3. Blood participated in the regulation of the temperature, pH and Fluid balance in the body. Types of Fluid Connective Tissue: Blood Blood is classified as a specialized type of connective tissue due to its composition and functions. Composition 1.Cells: 1. Erythrocytes (Red Blood Cells): Carry oxygen from the lungs to tissues and return carbon dioxide from tissues to the lungs. They make up about 45% of blood volume. 2. Leukocytes (White Blood Cells): Part of the immune system, they help protect the body against infections and foreign invaders. They are larger than red blood cells and maintain their organelles. 3. Platelets: Cell fragments involved in blood clotting, helping to seal wounds and prevent blood loss. 2.Extracellular Matrix: Plasma  Extracellular Plasma The fluid portion of blood, making up about 55% of its volume. Plasma consists of about 92% water, along with plasma proteins (such as albumin, globulins, and fibrinogen), electrolytes, hormones, nutrients, and waste products.  Cells: Erythrocytes Erythrocytes, or red blood cells, are typically found in counts of 3.9–5.5 million per microliter in women and 4.1–6 million per microliter in men. Their biconcave shape enhances oxygen (O2) and carbon dioxide (CO2) exchange between tissues and the lungs. These cells lose their nucleus during maturation and have a lifespan of approximately 120 days. Erythrocytes contain hemoglobin. Cells: Leukocytes (white blood cells): They are 5,000 to 10,000 WBCs/microliter of blood. Very motile and flexible, most of them migrate to the tissues to perform multiple functions. Help initiate an immune response and defend against pathogens. leukocytes are larger than erythrocytes and don’t lose their organelles during maturation. According to the type of granules in their cytoplasm and the shape of their nuclei, leukocytes are divided into two groups: A. Granulocytes (polymorphonuclear leukocytes) and B. Agranulocytes (mononuclear leukocytes). Both are spherical, but some become amoeboid after leaving the blood vessels and invading the tissues. Cells:Leukocytes/ A. Granulocytes Granulocytes: have various types of specific granules that are distinguished from each others by staining, include: neutrophils, eosinophils and basophils. Neutrophils constituting 60%-70% of the circulating WBCs. contain 3-5 lobes nucleus and fine reddish to violet specific granules in cytoplasm which contain lysozyme and other antimicrobial agents. Their numbers rise, a condition called neutrophilia, in response to bacterial infections. Cells:Leukocytes/ A. Granulocytes Eosinophils Harder to find in a blood film. Percentage of WBCs 2-4%. The eosinophil has bilobed nucleus, and the cytoplasm has an abundance of coarse rosy to orange-colored (pink/red) specific granules. They secrete chemicals that weaken or destroy parasites, they also phagocytize antigen-antibody complexes, and allergens. Basophils: Percentage of WBCs