HLSC 120 W2025 Ch 6 Bone Notes PDF

CHAPTER 6 Bone Tissue  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of Bones 4. Anatomy of A Bone 5. Histology of Bone Tissue 6. Bone Formation  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of B...

CHAPTER 6 Bone Tissue  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of Bones 4. Anatomy of A Bone 5. Histology of Bone Tissue 6. Bone Formation  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of Bones 4. Anatomy of A Bone 5. Histology of Bone Tissue 6. Bone Formation Introduction Bone = more purposes than just support and attachments for muscles Continuously remodelling. Building new bone Breaking down old bone Skeletal System: entire framework of bones and their cartilages Osteology: study of bone structure and treatment of bone disorders  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of Bones 4. Anatomy of A Bone 5. Histology of Bone Tissue 6. Bone Formation Functions of Bones Bone (osseous): composed of various tissues working together Skeleton Basic Function 1. Support Skeleton is structural framework for body 2. Protection Skeleton protects important organs from injury 3. Assistance in Movement Skeletal muscles attach to bones and when they contract, result in movement Functions of Bones 4. Mineral storage and release Minerals: calcium and phosphorus 99% of total body calcium Bone releases minerals for use in body 5. Blood cell production Red bone marrow (a connective tissue) produces RBC, WBC, and platelets Process called hemopoiesis = blood making RBM produces two (2) million RBC every second 6. Triglyceride storage Yellow bone marrow consists of adipose cells storing triglycerides (energy source)  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of Bones 4. Anatomy of A Bone 5. Histology of Bone Tissue 6. Bone Formation Types of Bones Form follows function 206 individual bones in adult skeleton Five types of bones: 1. Long bones 2. Short bones 3. Flat bones 1 4. Irregular bones 3 5. Sesamoid bones 4 2 5  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of Bones 4. Anatomy of A Bone 5. Histology of Bone Tissue 6. Bone Formation Anatomy of Bone Example: humerus 2 3 Typical long bone consists of: 1. Diaphysis Bone shaft, or body 2. Epiphysis Proximal and Distal ends of bone 3. Metaphysis 1 Regions between diaphysis and epiphysis In growing bone, it contains epiphyseal (growth) plate 3 2 Anatomy of Bone 4 4. Articular Cartilage Thin layer of hyaline cartilage covering part of epiphysis Occurs where bone articulates with another bone Reduces friction / absorbs shock 5. Periosteum Tough connective tissue Associated with blood supply Assists in fracture repair 5 Helps nourish bone Attachment for ligaments / tendons Anatomy of Bone 6. Medullary Cavity Marrow cavity Contains yellow bone marrow Contains blood vessels 7. Endosteum Thin membrane that lines 7 medullary cavity 6  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of Bones 4. Anatomy of A Bone 5. Histology of Bone Tissue 6. Bone Formation Histology of Bone: Four types of Bone Cells Osteoprogenitor Osteoblasts Osteocytes Osteoclasts Progenitor: Bone-building cells Osteoblasts become Break down bone means embedded in (bone resorption) “originates” Immature cells extracellular matrix = become osteocytes Hugh cells made from Only bone cells Secrete collagen fibers fusion of 50 to undergo cell and other organic Mature bone cells monocytes (WBC) division compounds to form extracellular matrix Maintain daily Release acids and Develop into metabolism of bones lysosomal enzymes osteoblasts They initiate calcification that break down bone Histology of Bone: Two types of Bone Tissue Two types of bone tissue 1. Compact bone tissue 2. Spongy bone tissue 1. Compact bone tissue Referred to as dense bone Observed on bone surfaces, but can extend deeper into bone Compose bulk of long bone diaphysis Protection/support and resists stresses produced by weight and movement. Histology of Bone: Two types of Bone Tissue 1. Compact bone Tissue (continued) Composed of repeated structural units called osteons (1). Osteons = concentric lamellae (2) arranged around osteonic (central) canal of blood vessels and nerves (3) Between lamellae rings are spaces called lacuna (4) (dark brown lining). 2 4 3 1 Histology of Bone: Two types of Bone Tissue 1. Compact bone Tissue (continued) Lacunae contain osteocytes (1) (light brown with central nucleus) Radiating from lacunae are small channels called canaliculi (2) which are filled with extracellular fluid Osteocyte fingerlike projections extend from osteocytes within canaliculi Allows osteocytes to communicate with other osteocytes 2 1 Osteocyte Histology of Bone: Two types of Bone Tissue 2. Spongy bone tissue Referred as trabecular bone tissue (1) Located in bone interior and protected by a covering of compact bone (2) Histology of Bone: Two types of Bone Tissue 2. Spongy bone tissue (continued) Spongy bone tissue consists of trabeculae (thin columns) (1) Trabeculae composed of lamellae (2) Red and Yellow bone marrow (3) are spaces between trabeculae. https://biologydictionary.net/spongy-bone/  Bone Tissue 1. Introduction 2. Functions of Bone and Skeletal System 3. Types of Bones 4. Anatomy of A Bone 5. Bone surface Marking 6. Histology of Bone Tissue 7. Bone Formation Bone Formation Osteogenesis: involves ossification Ossification: process of bone formation Bone formation follows one of two patterns. Both lead to same structure but just use different methods A. Intramembranous ossification Bone forms directly with mesenchyme (simple method) Related bones: Flat bones B. Endochondral ossification (EO) (chondral = “of or related to cartilage”) Mesenchyme cells form hyaline cartilage Bone forms within hyaline cartilage Related bones: all other bones of body We will focus only on Endochondral Ossification Bone Formation: Endochondral Ossification (EQ) P Step 1: Development of Cartilage model During pregnancy, Mesenchymal cells (stem cells) crowd together into the general 3-D shape of future bones. A mesenchymal covering called the Perichondrium develops around the model (P) Mesenchymal cells then differentiate into Chondroblasts Chondroblasts secrete a cartilage extracellular matrix producing a cartilage model of hyaline cartilage (1) Bone Formation: Endochondral Ossification (EQ) Step 2: Growth of Cartilage model P Once chondroblasts become embedded in cartilage extracellular matrix, they are called chondrocytes Cartilage model grows in length (interstitial growth) Growth in thickness (appositional growth) is due to deposition of more extracellular matrix on the model surface by new chondroblasts from the pericardium (P) “apposition”: means things being side by side As the model grows, the inner matrix begins to calcify causing chondrocytes to die due to lack of nutrition. As they die empty space is left behind Bone Formation: Endochondral Ossification (EQ) Step 3: Primary Ossification Center (POC) Nutrient artery penetrates the pericardium Increased nutrition stimulates the osteoprogenitor cells to differentiate into osteoblasts This starts the formation of bone on the diaphysis. Once the pericardium begin to form bone it is known as the periosteum. Primary ossification center: bone tissue replaces most of the cartilage Osteoblasts secrete extracellular matrix over the calcified cartilage which forms spongy bone. Bone Formation: Endochondral Ossification (EQ) Step 4: Medullary Cavity (MC) (marrow) Osteoclasts are generated by the fusion of numerous macrophages Osteoclasts break down spongy bone creating the Medullary cavity Bone Formation: Endochondral Ossification (EQ) Step 5: Secondary Ossification Centers (SOC) Near the time of birth, branches of the epiphyseal artery enters the two epiphyses Process similar to primary ossification center development, however spongy bone remains and there is no development of medullary cavity Bone Formation: Endochondral Ossification (EQ) Step 6: Formation of Articular Cartilage and Epiphyseal (growth) plate Hyaline cartilage that covers epiphyses becomes the Articular cartilage Hyaline cartilage between diaphysis and epiphysis (Epiphyseal plate) remains until puberty Bone Formation: Endochondral Ossification (EQ) Key Points: Mesenchymal cells form future bones Mesenchymal cells differentiate into chondroblasts that produces hyaline cartilage model (extracellular matrix) Chondroblasts embedded in extracellular matrix become chondrocytes Calcification causes chondrocytes to die Nutrient artery increases nutrition and stimulate osteoprogenitor cells to differentiate into osteoblasts (build bone) Osteoblasts result in formation of periosteum and spongy bone Osteoclasts (numerous macrophages) break down bone and create medullary cavity Bone Formation: Bone Growth in Length Growth in Length (Interstitial) Growth in length involves: 1. Growth in cartilage on the epiphyseal side of the epiphyseal plate, and 2. Replacement of cartilage with bone on the diaphyseal side Epiphyseal plate = layer of hyaline cartilage consists of four zones 1. Zone of resting cartilage 2. Zone of proliferating cartilage 3. Zone of hypertrophic cartilage 4. Zone of calcified cartilage Bone Formation: Bone Growth in Length Bone Formation: Bone Growth in Length 1. Zone of resting cartilage Zone nearest epiphysis Small scattered chondrocytes near epiphysis Resting because they don’t function in bone growth Rather they anchor epiphyseal plate to epiphysis of bone 2. Zone of proliferating cartilage Larger chondrocytes arrange like stacks of coins 2 Undergo interstitial growth as they divide Chondrocytes are responsible for cartilage formation 1 https://pedsinreview.aappublications.org/content/39/9/454/tab-figures-data Bone Formation: Bone Growth in Length 3. Zone of hypertrophic cartilage Large maturing chondrocytes arranged in columns Columns increase in length 4. Zone of calcified cartilage Chondrocytes are dead and matrix is calcified 4 Osteoclasts and osteoblasts move in 3 Osteoclasts dissolve calcified cartilage Osteoblasts replace cartilage with bone extracellular matrix = now bone Result: diaphysis now longer = bone has increased in length https://pedsinreview.aappublications.org/content/39/9/454/tab-figures-data Bone Formation: Bone Growth in Thickness Growth in thickness (appositional) Process 1. Ridges in periosteum create grooves for blood vessels 2. Periosteum ridges fuse to form tunnels 3. Osteoblasts build new lamellae 4. Bone grows outward from tunnel = new osteon  Bone Phonological Visuospatial chunks chunks Function Blood cells / mineral and triglyceride storage 206 bones Long, short, flat, irregular, sesamoid Cells M diff into OP diff into OB / OB (build bone) / OClasts (break down bone), OB mature into osteocytes (mature, maintain ECM) Endochondral M diff to CB and OP / CB create cartilage / OP diff to ossification OB create bone. (1) CB change bone shape into hyaline cartilage (2) CB mature into CC / CC undergo rapid interstitial growth (3) POC, no nutrients = CC die = cartilage disintegrates / artery enters = OP diff to OB = Spongy bone replaces disintegrating cartilage (4) OC break down spongy bone = MC (5) SOC, artery enters epiphyses = OB replaces cartilage with spongy bone (5) hyaline cartilage remaining now called Articular cartilage Interstitial Resting (CC anchor plate) / proliferation (CC undergo growth intestinal growth) / hypertrophic (Large CC arrange in (length) columns = more length) / calcification (OC break down cartilage, OB replace with ECM)