Histology: Bone and Connective Tissue PDF - August 30, 2024

HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024...

HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024 - Hemocytoblasts - occur in the bone marrow and produce CONNECTIVE TISSUES erythrocytes (RBCs), leukocytes (WBCs), and platelets Connective tissues are the major supporting tissue of the (formerly called thrombocytes) body. - Leukocytes - migrate from the bone marrow to connective It is composed of variety of cells, fiber (non-living products tissues and provide various body defense activities of the cell), and sei-solid matrix between cells. - Macrophages - engulf foreign and dead cells Mast cells - Characteristics of connective tissue: ranges from avascular secrete histamine, which stimulates immune responses to highly vascular - Plasma cells – produce antibodies Composition: Composed mainly of nonliving extracellular FIBER matrix that separates the cells of the tissue Matrix fibers are proteins that provide support for the connective Location: It is present in between different tissue and tissue. There are three types organs. It can be found in and around the body organs. skeletal tissue present in the form of bone and cartilage, Collagen fibers, made of the protein collagen, are both and fluid connective tissue as blood and lymph are tough and flexible. connective tissue. Elastic fibers, made of the protein clastin, are strong and 7 stretchable. Reticular fibers, made of thin collagen fibers with a glycoprotein coating, branch frequently to form a netlike (reticulate) pattern. GROUND SUBSTANCE Ground substance may be fluid. gel, or solid, and, except for blood, is secreted by the cells of the connective tissue: Cell adhesion proteins - hold the connective tissue together Proteoglycans - provide the firmness of the ground substance. Hyaluronic sulfate and chondroitin sulfate are two examples. CLASSIFICATION OF CONNECTIVE TISSUES Five general categories of mature connective tissue: FUNCTIONS OF THE CONNECTING TISSUE Loose connective tissue - has abundant cells among few or It binds various tissue together like skin with the muscles loosely arranged fibers and a sparse to abundant gelatinous and muscles with bones ground substance. It forms inter cellular substance between cells of different Dense connective tissue - has few cells among a dense types of tissue, so that help in friction less movement of the network of fibers with little ground substance body organ Cartilage - has cells distributed among fibers in a firm gel It forms sheaths around the body organs and make a kind like ground substance. Cartilage is tough but flexible, of packaging tissue avascular, and without nerves. The areolar tissue protects the body against wound and Bone - has cells distributed among abundant fibers in a solid infection ground substance containing minerals, mostly calcium The adipose tissue stores fats and insulates the body phosphate. Bone is organized in units, called osteons against heat loss (formerly known as the Haversian system). Each osteon consists of a central canal, which contains blood vessels and The supportive tissue forms shape and the frame work of nerves, surrounded by concentric rings (lamellae) of hard the body matrix and collagen fibers. Branching off the central canal The haemopoietic tissue produce blood at right angles are perforating canals. These canals consist The lymphatic tissue helps in body immunity of blood vessels that branch off the central vessels. CELL TYPES Between the lamellae are cavities (lacunae) that contain Fundamental cell types, characteristic of each kind of bone cells (osteocytes). Canals (canaliculi) radiate from the connective tissue, are responsible for producing the matrix central canal and allow nutrient and waste exchange with Immature forms of these cells (whose names end in -blast) the osteocytes secrete the fibers and ground substance of the matrix. Blood - composed of various blood cells and cell fragments Cells that have matured, or differentiated (whose names (platelets) distributed in a fluid matrix called blood plasma. often end in -cyte). function mostly to maintain the matrix TISSUE ORIGINS - Fibroblast – both loose and dense connective tissue All mature connective tissues originate from embryonic connective - Adipocyte – contains molecules of fat; found in loose tissue. here are two kinds of embryonic connective tissues: connective tissue and adipose - Mesenchyme is the origin of all mature connective tissues. - Reticular cells – resembles fibroblasts but with long cellular - Mucous connective tissue is a temporary tissue formed processes (extensions); found in loose connective tissue during embryonic development - Chondroblasts and chondrocytes – found in cartilage An epithelial membrane is a combination of epithelial and connective - Osteoblast and osteocytes – found in bone tissues working together to perform a specific function. As such, it HISTOLOGY 3 Prepared by: KCC Date: August 30, 2024 HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024 acts as an organ. There are four principle types of epithelial membranes: - Serous membranes line interior organs and cavities. The serous membranes that line the heart, lungs, and abdominal cavities and organs are called the pericardium, pleura, and peritoneum, respectively. - Mucous membranes line body cavities that open to the outside of the body. These include the nasal cavity and the digestive, respiratory, and urogenital tracts. - Synovial membranes line the cavities at bone joints. - The cutaneous membrane is the skin. TYPES OF CONNECTIVE TISSUE b. Adipose Connective Tissue - It consists of adipocytes which stores fat - Location: It is present in subcutaneous layer deep in the skin around the heart and kidneys - Functions: o Prevents heat loose from body. o Act as reservoir of energy o It gives shape to the limbs and body. o It protects underlying organ from injury. c. Reticular Connective Tissue - It contains reticular fibers and reticular cells. - Locations: It is present in the supporting framework of liver, spleen lymph nodes, red bone marrow and it is also found around blood vessels and muscles. A. PROPER CONNECTIVE TISSUES - Functions: It binds together smooth muscle tissue cells, i. Loose Connective Tissues filters and removes microbes in the lymph node ii. Dense Connective Tissue a. Fibrous Tissue - In this tissue, fibers are densely packed. - The fiber content is higher. - Cell content is lower as compared to loose connective tissue - It is of two types, Dense regular connective tissue and dense irregular connective tissue 1. Dense Regular Connective Tissue - Bundles of collagen fibers are arranged in parallel patterns to provide strength to a. Areolar Connective Tissue tissue - They form a loose network in intracellular material - Fibroblast are appeared in rows between - It consists of collagen, elastic fibers. reticular fibers and the fibers. several kinds of cells - It is tough in nature. - Location: Below the skin, fill space between muscles, - Location: It forms tendons (attach supports blood vessels and nerves in alimentary canal muscle bone) and ligaments (attach bone - Functions: It gives strength, elasticity and support to to bone) tissue. HISTOLOGY 3 Prepared by: KCC Date: August 30, 2024 HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024 - Functions: It provides strong attachment - Location: It is present at the end of long to structure. bones, anterior ends of ribs, nose and parts 2. Dense Irregular Connective Tissue of larynx, trachea, bronchi, bronchial tubes. - It contains collagen fibers which are - Function: It provides small surface for irregular arranged and a few fibroblasts movement at joints, flexibility and support are appear in rows between the fibers. 2. Fibrocartilage - Location: It present in dermis layer of - It is strongest form of cartilage The skin, membrane capsules around chondrocytes are scattered among the kidneys, liver, testes and lymph node, bundle collagen fibers within the heart valves extracellular matrix. - Functions: It provides strength to - Location: It is present in inter-vertebral disc. different organs - Functions: It covers and protects bony structures of body. 3. Elastic Cartilage - The chondrocytes are located within a threadlike network of elastic fibers within extracellular matrix. - The chondrocytes are located within a threadlike network of elastic fibers within extracellular matrix. - Functions: It provides strength and elasticity and maintain the shape of certain organs like the external ear. b. Elastic Tissue - It consists of freely branching elastic fibers - Fibroblast are present in space between fibers. - It is yellowish in color. - Location: It is present in tissues, walls of elastic arteries, trachea, bronchial tubes and vocal cords. - Functions: It allows stretching of various organs. B. SUPPORTING CONNECTIVE TISSUE TYPES i. Cartilage Connective Tissue - "It consists of network of closely packed collagen fibers and elastic fibers - The cells of mature cartilage called as chondrocytes 1. Hyaline Cartilage - It is bluish white in color. - It consists of fine collagen fibers and many chondrocytes. HISTOLOGY 3 Prepared by: KCC Date: August 30, 2024 HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024 BONE ii. Bone Connective Tissue Structure of Long Bone Compact Diaphysis - consists of thick walled hollow cylinder of compact bone with central marrow cavity (medullary - Osteon - basic unit of compact bone cavity) occupied by the bone marrow - Lamellae-concentric circles of matrix Epiphysis - ends of long bones arising from separate - Lacunae- spaces in the matrix that house cells ossification centers and separated from the diaphysis by - Osteocytes - mature bone cells the cartilaginous epiphyseal plates. Has 2 ends: Spongy - proximal - Trabeculae - columns of bone with spaces filled - distal with red bone marrow Metaphysis - From the epiphyseal plate there is a transition growth bone which we call the metaphysis wherein the growth of the bone occurs. Epiphyseal line - a cartilaginous plate separates the Epiphysis and Diaphysis. Articular cartilage Medullary cavity C. FLUID / LIQUID CONNECTIVE TISSUE TYPES I. Blood connective tissue - Connective Tissue with a liquid matrix - Red Blood Cells (erythrocytes) - transport oxygen - White Blood Cells - function in immunity (Neutrophils, Eosinophils, Basophils, T and B leukocytes, natural killer cells and Monocytes) - Platelets (participate in blood clotting) HISTOLOGY 3 Prepared by: KCC Date: August 30, 2024 HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024 Osteoclasts: not derived from osteoprogenitors ‣ Related to macrophages ‣ Formed from multiple cells; are multinucleated ‣ are involved in bone resorption Endosteum: lines marrow cavity, incomplete - Osteoprogenitor cells - Osteoblasts OSTEOCLAST - Osteoclasts Located in Howship's lacuna Ruffled edge contacts bone Periosteum: covers bone everywhere but articular surfaces Secrete hydrochloric acid - Two layers - Dissolves minerals o Fibrous layer: outermost, dense irregular CT - osteolysis ❖ Site of tendon attachment Lysosomes o Inner layer: next to compact bone Secrete enzymes that dissolve matrix ❖ Osteoblasts present in young bone - Anchored to bone by perforating fibers (collagen) FLAT BONES OF THE SKULL Two layers of compact bone - Inner table - Outer table Region of spongy bone sandwiched between them - Called the diploe Both layers of compact bone are covered by periosteum COMPOSITION OF BONE MATRIX FOUR TYPES OF BONE CELLS Organic components: one third Osteoprogenitor cells ‣ stem cells derived from - Cells mesenchyme which produce other stem cells and - Collagen fibers osteoblasts - Ground substance Osteoblasts ‣ produce new bone, and once osteoblasts Inorganic components: two thirds become entrapped in the matrix they produce and secrete, - Calcium phosphate they differentiate into osteocytes - Hydroxyapatite crystals: calcium phosphate and calcium Osteocytes ‣ mature bone cells hydroxide TYPES OF OSSEOUS TISSUE HISTOLOGY 3 Prepared by: KCC Date: August 30, 2024 HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024 Compact - Dense, cortlcal - ‣ canaliculi Spongy - Cancellous, trabecular COMPACT BONE MICROANATOMY Osteon (Haversian) system: basic unit - ‣ Central (Haversian) canal - ‣ Concentric lamellae - Contain collagen fibers - ‣ Osteocytes - ‣ Lacunae - ‣ Canaliculi: permit intercellular communication Cylinder that runs with long axis of long bone Perforating canals (Volkmann canals) - ‣ Contain blood vessels, nerve - ‣ Run perpendicular to central canals, connect them Circumferential lamellae - ‣ Internal to periosteum‣ External circumferential lamellae - ‣ Internal to endosteum ‣ Internal circumferential lamellae - ‣ Run the entire circumference Interstitial lamellae - ‣ Remains of osteons *couldn’t find separate pics so here’s the whole illustration OSSIFICATION Osteogenesis: bone formation and development SPONGY BONE MICROANATOMY Begins in the embryo: By the eighth through twelfth weeks: - ‣ the skeleton begins forming: No osteons In trabeculae - ‣ from mesenchyme - ‣ Parallel lamellae - ‣ or from a hyaline cartilage model of bone - ‣ Osteocytes in lacunae - ‣ These models are replaced by hard bone HISTOLOGY 3 Prepared by: KCC Date: August 30, 2024 HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024 Continues during childhood and adolescence In the adult, ossification continues. INTRAMEMBRANOUS OSSIFICATION Also called dermal ossification Produces: - the flat bones of the skull (cranial vault) - some of the facial bones (zygomatic bone, maxilla), the mandible (lower jaw) - the central part of the clavicle (collarbone). It begins when mesenchyme becomes thickened and condensed with a dense supply of blood capillaries. 1. Ossification centers form in thickened mesenchyme ‣Osteoprogenitors develop become osteoblasts 2. Osteoid (bone matrix) calcifies ‣ Trapped osteoblasts become osteocytes 3. Woven bone (primary bone) forms, periosteum forms (from mesenchyme) 4. Lamellar bone (secondary bone) replaces woven bone; compact and spongy bone form ENDOCHONDRAL OSSIFICATION Begins with a hyaline cartilage model Produces most of the other bones of the skeleton EPIPHYSIAL PLATE MORPHOLOGY Long bone will be used as an example. Hyaline cartilage 1. Cartilage model develops: 5 zones: from epiphysis to diaphysis Zone of resting cartilage - Chondroblasts become chondrocytes - Perichondrium develops - Small chondrocytes in cartilage matrix 2. Cartilage calcification, bone collar develops in shaft - Looks like healthy cartilage - Chondrocytes hypertrophy, then die - Secures epiphyseal plate to epiphysis Zone of proliferating cartilage - Blood vessels grow toward cartilage - Osteoblasts under perichondrium form bone - Chondrocytes here are undergoing rapid mitosis 3. Primary Ossification center forms: - Stack up in columns - Periosteal bud: osteoblasts and blood vessels Zone of hypertrophic cartilage - 12th week: most have formed - Chondrocytes stop dividing 4. Secondary Ossification centers: - Start hypertrophy - In epiphysis - Absorb matrix - Some form post-natally Zone of calcified cartilage 5. Cartilage replaced by bone - Few cells thick - Except articular cartilage, epiphyseal plate - Calcification of matrix 6. Epiphyseal plate ossifies: - Kills the chondrocytes - Forms epiphyseal line Zone of ossification - Between 10 and 25 - Invasion by capillaries and osteoprogenitor cells - Last... clavicle HISTOLOGY 3 Prepared by: KCC Date: August 30, 2024 HISTOLOGY LECTURE 3: BONE AND CONNECTIVE TISSUE Prepared by: Kayla Clarisse Cabilin Lecturer: DR BASTERO Date: August 30, 2024 HISTOLOGY 3 Prepared by: KCC Date: August 30, 2024