BIO11.01 Module 2 Skeletal System - Cartilage and Bone (9-12-2024) PDF

Skeletal System (Part 1: Cartilage and Bone – Tissue Level) BIO11.01 Human Biology, Health and Disease, Lecture First Semester 2024-2025 September 16, 2024 Page References Tortora 16th edition Chapter 4 (pp. 134-137) Cartilage...

Skeletal System (Part 1: Cartilage and Bone – Tissue Level) BIO11.01 Human Biology, Health and Disease, Lecture First Semester 2024-2025 September 16, 2024 Page References Tortora 16th edition Chapter 4 (pp. 134-137) Cartilage Microscopic features of bone Chapter 6 Bone (Overview) Chapter 9 (pp. 270-274) Classification of Joints Skeletal System Recall: Types of connective tissue, What are its functions? Made up of cartilage and bone Bones articulate with each other through joints. Both cartilage and bone are specialized type of connective tissue Supports the structural framework of the body. Bone and Cartilage Bone and cartilage serve distinct functions within the skeletal system. At the tissue level, bone and cartilage both consist of cells that are surrounded by an extracellular matrix (ECM). The ECM sustains and supports the cells Many protein and mineral components The appearance of the extracellular matrix depends on the type and function of the tissue. Imagine a milk tea drink… If the pearls/boba are the cells, the milk tea itself will be the ECM… :) How much boba do you want? “Yesss.” GEL-LIKE AND FLEXBILE ECM IN CARTILAGE. Its cells (chondrocytes) are surrounded by an ECM that is predominantly made of collagen and elastic fibers. HIGHLY MINERALIZED AND SOLID ECM IN BONE. Osteocytes are present within the dark spaces within the mineralized matrix.  Presence of Ground Substance Tissue Function Organization Vascularity Covering calcification (ECM) Component Seen in areas of the None Chondroitin sulfate Chondrocytes are Avascular Perichondrium body that needs to + Fibers (e.g., randomly arranged (Blood vessels endure more strain collagen, elastic within the ECM. Cartilage are limited to Cartilage (e.g., body weight); fibers) does not the Elasticity (e.g., Cells appear to be have a blood perichondrium; Cell Type: expansion of the floating within the supply. nutrients are Chondrocyte ribcage); Provides a extracellular matrix. carried to smooth surface for chondrocytes via articulation (e.g., the ECM.) joints) Rigid tissue that Yes Calcium phosphate Regular arrangement Vascular Periosteum provides a Developing bone + Fibers (e.g., of osteocytes within framework for the undergoes a collagen) the mineralized ECM. Blood vessels body as well as process known as are present Bone locomotion; Protects ossification Compact bone appears within vital organs (e.g., associated with a to be organized into designated Cell Type: cranium and ribcage); marked deposition osteons. spaces of the Osteocyte Provides attachment of calcium bone. for skeletal muscles. phosphate In spongy bone, they (hydroxyapatite) are organized to form within the ECM. trabeculae. Cartilage Flexible yet firm type of connective tissue that serve different functios in the body. This type of tissue is composed of cells called chondrocytes which are housed in structures called lacunae. The matrix is composed of chondroitin sulfate which may be admixed with collagen and elastic fibers. Chondroitin provides cartilage resilience (ability to assume its original shape after deformation). Collagen provides strength and stability to the cartilage. The Three Types of Cartilage Hyaline Cartilage Fibrocartilage Elastic Cartilage There are three types of cartilage seen in the human body, each serving a very specific function: 1. Hyaline cartilage 2. Elastic cartilage 3. Fibrocartilage Hyaline Cartilage This is the most common type of cartilage. Hyaline = “glassy” Extracellular matrix appears like frosted glass. This cartilage is seen on the ends of long bones (articular surface), tips of ribs, airways (tracheal cartilage) and in some portions of the skull (e.g., nasal cartilage) Hyaline cartilage also provides the necessary framework for later bone formation (endochondral ossification). Expansion of the ribcage The articular cartilage provides a gliding surface for the smooth movement of joints.  The nose is made up of hyaline cartilage. Trachea and bronchi are surrounded by rings of hyaline cartilage. Elastic Cartilage Recall: The role of elastic fibers in the skin (dermis). This a flexible and springy cartilage due to the abundance of elastic fibers in its matrix. This can be seen in the cartilage supporting the ear (pinna) as well as in the epiglottis. The ECM in elastic cartilage is densely packed with elastic fibers. This gives elastic cartilage its characteristic properties. A special stain was used in this photomicrograph of elastic cartilage. The dense black fibers indicate that the ECM surrounding the chondrocytes is filled with elastic fibers. The epiglottis directs air to the lungs and food to the esophagus. This structure is made up of elastic cartilage. When the food has already gone down the esophagus, the epiglottis immediately bounced back to its original form, hence the need for elastic cartilage. Note: The food needs gravity to go down to the esophagus. Eating in a supine position might lead the food to the trachea causing blockage of the airway, a phenomenon known as aspiration. Fibrocartilage This type of cartilage has been reinforced with more collagen fibers making it resistant to tensile and warping forces. Some examples include the intervertebral discs (annulus fibrosus), symphysis pubis, and the meniscus of the knee. These are weight bearing and bending regions of the body FIBROCARTILAGE DENSELY PACKED COLLAGEN FIBERS ARE SEEN IN THE ECM The spine bears the weight of the upper body. The intervertebral discs between the vertebrae are made up of fibrocartilage. Fibrocartilage in the symphysis pubis Cushions the pelvis from shearing movements from normal physical activities (e.g. while walking or running) Becomes more flexible in pregnant women to accommodate the baby passing through during childbirth. The meniscus bears the weight of the upper body at the level of the knee joint. It is made up of fibrocartilage to cushion the knee when standing still and while walking. Cartilage Distinctively, cartilage does not have a blood or nerve supply. Blood vessels are confined to the surrounding perichondrium. Nutrients and gases go into the chondrocytes via the extracellular matrix. Clinical Correlation: Cauliflower Ear Commonly associated with combat sports athletes, mixed marital artists, boxers and wrestlers Deformity of the ear that is commonly associated with blunt trauma Blood pooling on the ear could lead to improper regeneration of elastic cartilage and could lead to permanent deformities. Functions of Bone Support Bone serves as the structural framework of the body. Attachment for soft tissues (connective tissue, fat, etc.) Serves a points of attachment for muscle (via tendons) Protection Protects vital organs from potential injury (e.g., the cranium protects the brain while the ribcage protects the heart and lungs) Aids in movement Skeletal muscles produce movement by acting on bones Muscle contractions move a bone by its joint creating movement Functions of Bone Blood cell production Within bones lies red bone marrow. Red bone marrow produce red blood cells, white blood cells and platelets through a process known as hemopoiesis. In adults, this is localized to the sternum (breast bone), hip bones, vertebrae (back bone), skull and humerus (arm bone). In newborns, all bone marrow is red (and is involved in hemopoiesis) but with increasing age, a proportion becomes yellow bone marrow. Functions of Bone Mineral homeostasis Bone serves as reservoirs for calcium and phosphorous. 99% of calcium is stored in the bone On demand, bone may release calcium into the body Storage of fats In contrast to red bone marrow, yellow bone marrow is made up of fat cells. Fat serve as reservoirs of energy and can be used on demand. Bone Bone is a specialized type of connective tissue wherein calcium phosphate is deposited within the matrix. Bone is produced by cells called osteoblasts. When it is surrounded by the bone matrix, the osteoblast transforms to become an osteocyte. Osteoclasts are responsible for reabsorbing bone (e.g., removing existing bone). Increase concentration of calcium in the body Bone remodeling (e.g., gradual change in the shape of the bone) Compact and Spongy (Cancellous) Bone Bone can be classified depending on how the ECM and the cells are organized. Compact bone appears dense and solid. Cancellous bone appears porous with spaces in between. The bony structures within spongy bone are called trabeculae. The spaces are filled with bone marrow elements. COMPACT BONE OSTEON OR HAVERSIAN SYSTEM Osteonic Bone Lamellae (Haversian) Canal (Orange Rings) (White Arrow) Concentric rings of Center of the ECM that consists of osteon that mineral salts (mostly contain blood calcium and vessels and nerves. phosphates) which Remember that give bone hardness bone is and compressive vascularized. strength + collagen for tensile strength The dark spaces (blue arrows) within the lamellae are called lacuna (similar to the term used in cartilage). These structures contain osteocytes. Canaliculi (red arrows) are small spaces originating from the lacuna. These structures house the processes emanating from osteocytes. These would provide ways for nutrients to reach osteocytes and eliminate wastes. These also allow the cells to communicate with each other. COMPACT BONE FORMS OSTEONS CANCELLOUS BONE (TRABECULAE) WITH BONE MARROW Note the structure of spongy bone. Unlike compact bone, the haversian canal is absent. Lamellae, lacunae (with osteocytes) and canaliculi are present. Cortical and Medullary Bone A bone can be divided into an outer cortex and an inner medulla. Cortical bone - forms the cortex (outer boundary) of the bone. Compact bone Medullary bone is seen at the core of the bone producing a space that will be filled up with bone marrow elements. Spongy bone Lamellar Bone and Non-lamellar (Woven) Bone Compact bone and spongy bone are examples of lamellar bone. Lamellar bone is characterized with a more organized arrangement of collagen fibers within the matrix. Consists of a layer of bone matrix with closely packed collagen fibers During bone development, immature bone tissue will organize to form lamellar bone. Regular arrangement of fibers within lamellar bone provides additional strength Non-lamellar (Woven) and Lamellar Bone Non-lamellar bone (woven bone) is described to be a fast-growing bone. Has irregularly arranged (disorganized) collagen fibers within the matrix. Given its faster rate of formation, woven bone plays an important role in the creation of new bone as well as the healing of fractures Where would you see lamellar bone in the human body? Woven bone needs to be reinforced to withstand physical stress. It will develop to be lamellar bone (either spongy or compact) later on. COMPACT BONE SPONGY BONE Chipboard / Particle Board (Irregularly arranged wood chips) -VS- Plywood (Laminated wood) Regions of Long Bones Epiphysis – This refers to the ends of long bones. Diaphysis – This area refers to the middle shaft of the bone. Metaphysis (epiphyseal plate) – Area between the diaphysis and the epiphyses. This area is made up of cartilage and indicates ongoing growth of the long bone. The epiphyseal plate is only present in young, growing individuals. In adulthood the epiphyseal plate will ossify forming an epiphyseal line. Primary ossification center – diaphysis Hyaline cartilage in the metaphysis (epiphyseal plate) Milk and Bone Growth Would someone still grow tall by drinking milk? Drinking milk would provide an additional source of calcium and would make bones stronger. If the epiphyseal plate has disappeared, one would not grow tall anymore. Throughout life, bone still has to grow. However, drinking milk as part of one’s diet will increase the girth of bone. Dwarfism and Gigantism He Pingping (74 cm [2 ft. 5 in.]) Sultan Kösen (251 cm [8 ft. 2 in.]) These conditions are associated with over or underproduction of growth hormone (GH) that is produced by the pituitary gland in the brain. Joints “Articulations” or “Arthroses” Refers to the point where two bones meet Joints can be classified based on the following criteria: Structural Classification Based on the tissues that hold the bones together Presence of a synovial cavity Functional Classification Range of Motion Note: A joint will have its own structural and functional classification. These terms would overlap. Structural Classification When referring to the structural classification, consider the tissue that bind the bones together. Fibrous joints – This joint is held by connective tissue with dense collections of collagen fibers Cartilaginous joints – Bones are held together by cartilage Synovial joints – This type of joint is joined by ligaments and has a fluid filled space known as the synovial cavity. This cavity is then surrounded by a tough capsule of connective tissue. Functional Classification When referring to the functional classification, this refers to the range of motion. Diarthroses – permits movement Amphiarthroses – permits movement to a certain degree Synarthroses – restrictive, do NOT permit any movement Synarthroses are classified further based on the type of tissue joining the bones together Examples of Fibrous Joints Sutures – joints that connect the bones of the skull together The interlocking edges of the suture would give the cranium additional strength and decrease the chances of fracturing Syndesmoses – bones are joined together by dense connective tissue Dentoalveolar joints – the connective tissue holds the tooth to the socket of the jaw Interosseous Membranes – bones are held together by sheets of connective tissue Binds long bones together while permitting movement Radius + ulna, Tibia + fibula Skull (superior view) In this view, the anterior portion of the skull (frontal bone) is joined to the parietal bone by sutures. Note the interlocking pattern present on the sutures. Skull (posterior view) In this view, the interlocking pattern of the suture. Take note that some sutures are completely made up of bone and thus classified as a synostosis. These joints are classified as synarthrosis because they are immovable. These bones are completely fused by age 6. In infants (neonates), the sutures in the skull have not completely closed, these openings are referred to as fontanelles.  Interosseous Dentoalveolar Joints Membrane (Syndesmosis) Sutures Synostosis “Bone-to-bone” Bones are articulated directly to each other (e.g., sacrum) Cartilaginous Joints a.) Synchondroses Bones are joined together exclusively by hyaline cartilage (These could also be classified as synarthroses.) b.) Symphyses Bones are held together by fibrocartilage (These could also be classified as amphiarthroses.) Recall: Where can you locate fibrocartilage? ☺ Synovial Joint Synovial joint are diarthroses - Joints that permit movement Structure: Synovial capsule - dense fibrosus tissue that covers the joint. This has the consistency of uncooked egg white. Synovial membrane - produces synovial fluid that lubricates the joint. Articular cartilage is also observed at the ends of the involved bones. Gout is a form of (painful) arthritis that develops over specific joints due to the accumulation of uric acid (as an effect of a purine-rich diet). Initial signs and symptoms involve pain and redness on the affected joint (e.g., big toe). Tophi (crystalline deposits of uric acid) developing on the joints in uncontrolled cases of gout. As uric acid crystals accumulate, gross deformities over the affected joint eventually appear. Purine-rich foods ”Popping Joints” ”Popping joints” can occur when air is released from the synovial fluid. After a joint has been “popped,” it might take a few minutes before air builds up again in the joint. Fractures Refers to any break in the bone Breaks in the bone may not have to be visible by x-rays or by the naked eye Stress fractures are microscopic fissures in the bone with no evidence of injury to other tissues Due to repeated strenuous activities (e.g., running and jumping) and may be observed in professional athletes. Stress fractures on the metatarsal bone of the right foot is due to repeated stress over a period of time (e.g., running). In some cases, this may cause pain and swelling. Types of Fractures Open (compound) The broken ends of the bone protrude through the skin Closed The bone does not break through the skin ULNA Open Fracture X-ray was taken on two RADIUS different views. Note the ulna is protruding from the skin. Classify the fracture encountered on the radius. ULNA RADIUS Stages of Fracture Repair Reactive Phase Reparative Phase [Initial] Fibrous cartilage callous formation [Late] Bony callus formation Bone Remodeling Phase Stages of Fracture Repair Bone heals more rapidly than cartilage because of its blood supply. Reactive Phase Early inflammatory phase that occurs after the traumatic injury Ruptured blood vessels within the bone leads to the formation of a mass of clotted blood around the site of injury (fracture hematoma) 6-8 hours after the injury Bone cells adjacent to the fracture hematoma dies Macrophages and osteoclasts remove the damaged tissue and bone Stages of Fracture Repair Reparative Phase (Fibrous cartilage callous formation) Blood vessels grow into the fracture hematoma and clean up dead cells and debris Fibroblasts and chondroblasts from the periosteum would now produce collagen fibers creating a fibrous cartilage (soft) callus to bridge the broken ends of bone. Formation of the soft callus takes about 3 weeks. Stages of Fracture Repair Reparative Phase (Bony callus formation) In areas of the callus that is closer to a developed blood supply, bone would now develop. Woven bone (non-lamellar) initially develops over the bone Eventually, these would now form spongy bone trabeculae. The bony callus forms when fibrous cartilage is gradually converted to spongy bone. This process may last up to 3-4 months. LAMELLAR BONE WOVEN BONE Stages of Fracture Repair Bone Remodeling Phase The callus now undergoes remodeling or reshaping This phase is the longest any may last for years Dead portions of the original bone fragments are reabsorbed by osteoclasts Compact bone replaces spongy bone around the area of the fracture In some cases, repair has been so thorough that the fracture line is undetectable. Fracture of the humerus (diaphysis) of an infant at birth. Given their young age, bone repair and remodeling is successful as seen in subsequent radiographs. Fracture Repair Although bone has an adequate blood supply, healing may still take months. Calcium and phosphorus is only deposited gradually and bone cells tend to reproduce slowly. Reduction refers to the process of setting a fracture (closed vs. open). The use of plaster clasts would fall under closed reduction. In some situations, metal implants might be used to align bones together. Summary When studying bone at the tissue level, compare the to what was observed in cartilage. Similarities Both are types of connective tissue (cells are suspended within an extracellular matrix. Cells are housed in lacunae Differences The cells are different (chondrocytes vs osteocytes) Cartilage is designed for flexibility and elasticity, Bone is meant to serve as a rigid structure serving as the body’s framework and protection What are the components within the ECM? Chondroitin sulfate in cartilage, Calcium phosphate in bone Blood supply: absent in cartilage, present in bone Summary Bone can be classified in different ways. Cortical vs. Medullary Bone Non-lamellar (woven bone) vs. Lamellar bone (compact and spongy bone) Remember: ”Lamellar” → It has lamellae. Classification of joints can overlap Structural classification (What holds the joint together?) Functional classification (Range of motion?) Thank you!