Bone Tissues, Axial, Appendicular & Joints PDF

BONE TISSUE PHC411 Gurmeet Kaur Surindar Singh (L7,FF1) Learning Outcomes Discuss the structure and functions of the skeletal system, including its histology, the ossification process, and its role in maintaining calcium homeostasis. Describe the different types...

BONE TISSUE PHC411 Gurmeet Kaur Surindar Singh (L7,FF1) Learning Outcomes Discuss the structure and functions of the skeletal system, including its histology, the ossification process, and its role in maintaining calcium homeostasis. Describe the different types of bone cells and bone tissues. Explain the process of bone growth & repair of bone fractures. Describe the bones of axial and appendicular skeletons  Introduction The skeletal system has 6 important functions: Provide support by acting as a structural framework and a point of attachment for tendons and ligaments Protect the internal organs (brain, chest, etc.) Assist body movements (in conjunction with muscles) Store and release salts of calcium and phosphorus Participate in blood cell production (hematopoiesis) Store triglycerides in adipose cells of yellow marrow Tissues of the Skeletal System Bone is a dynamic tissue – it is always remodeling (building up and breaking down). The skeletal system is made of several different tissues. The two major tissues are bone (osseous tissue) and cartilage. Tissues of the Skeletal System Bone is a highly vascularized C.T. with a hard, mineralized extracellular matrix. It is found in the body in two different arrangements: Compact bone – most of the bone in this graphic is compact bone. Spongy bone is seen as the less organized tissue along the left margin (with the spicules).  Tissues of the Skeletal System Compact bone is good at providing protection and support – reduces stress produce by weight & movement. It forms the diaphysis of long bones, and the external layer of all bones. Spongy bone is lightweight and Compact bone provides tissue support - Trabeculae of spongy bone support and protect the red bone marrow and are oriented along lines of stress (helps bones resist stresses without breaking). - Hematopoiesis (blood cell production) occurs in spongy bone. It forms much of the epiphysis and the internal cavity of long bones. Spongy bone  Bone Structure The diaphysis is the shaft or body of a long bone. The epiphyses form the distal and proximal ends of a long bone. The metaphyses are the areas where the epiphyses and diaphysis join.  Tissues of the Skeletal System Cartilage is a poorly vascularized C.T. with a matrix composed of chondroitin sulfate and various fibers. Hyaline cartilage - fine collagen fiber (end of long bones) perichondrium Fibrocartilage – thick collagen fiber (intervertebral discs) Elastic cartilage – elastic fiber (external ear) chondrocytes The cell of mature cartilage is called chondrocytes Hyaline cartilage Tissues of the Skeletal System The perichondrium is a dense irregular connective tissue membrane that surrounds cartilage. Perichondrium Contains blood and nerves Source of new cartilage cells. Periosteum Tissues of the Skeletal System Articular cartilage is the thin layer of hyaline cartilage covering the epiphysis of long bones. Articular cartilage is found where the bone forms an articular (joint) surface - where one bone moves against another bone. Hyaline cartilage is the articular cartilage of this long bone Tissues of the Skeletal System The periosteum is a tough sheath of dense, irregular connective tissue on the outside of the bone. It contains osteoblasts that help the bone grow in thickness, but not in length. It also assists with fracture repair and serves as an attachment point for tendons and ligaments. Structure of Bone The medullary cavity is a space within the diaphysis of long bones that contains fatty yellow bone marrow in adults. The endosteum is a membrane that lines the medullary cavity. The endosteum is composed of osteoclasts, osteoblasts, and connective tissue.  Tissues of the Skeletal System The various cells in osseous tissues are shown in the bottom graphic: Fusion of many monocytes Release lysosomal enzyme and acids that digest the protein and breakdown minerals Unspecified stem cell derived from mesenchyme that divides and develops into osteoblast Tissues of the Skeletal System Osteoblasts are bone building cells: They synthesize and secrete collagen fibers and other organic components. Osteocytes are mature osteoblasts (maintain bones daily metabolism such as exchange of nutrients and waste with the blood). Osteoclasts are large bone breakdown cells. As white blood cells, osteoclasts migrated from the bone marrow to become “fixed macrophages” in the substance of the bone.  Tissues of the Skeletal System Besides bone and cartilage, the skeletal system contains other important tissues: Epithelium (endothelium) form the capillary walls Nerves (the periosteum is especially tender) Red marrow – hematopoiesis Yellow marrow – fat storage Chemical Constituents of Bone Bone is 25% water, 25% organic proteins, 50% mineral salts (hydroxyapatite crystals). Organic constituents Collagen fibers provide flexibility and tensile strength. Inorganic mineral salts Calcium Phosphate (Ca3PO4)2 Calcium Carbonate (CaCO3 – marble) Other trace elements: magnesium, fluoride, sulfate Bone Structure The humerus in the arm is a typical long bone. Histology of Bone Tissue Compact Bone contains units called osteons or Haversian systems formed from concentric lamellae (rings of calcified matrix). Interstitial lamellae between osteons are left over fragments of older osteons. Histology of Bone Tissue Outer circumferential lamellae encircle the bone beneath the periosteum. Inner circumferential lamellae encircle the medullary cavity.  Histology of Bone Tissue Lacunae are small spaces between the lamellae which house osteocytes. Canaliculi are small channels filled with extracellular fluid connecting the lacunae.  Histology of Bone Tissue Blood and lymphatic vessels are found in the osteon’s Central canal. Perforating (Volkmann’s) canals allow transit of these vessels to the outer cortex of the bone. Histology of Bone Tissue Spongy bone lacks osteons. Instead, lamellae are arranged in a lattice of thin columns called trabeculae.  Histology of Bone Tissue The interior of long bones is made up primarily of spongy bone. The use of spongy bone lessens overall bone weight.  Histology of Bone Tissue Within each trabecula of spongy bone are lacunae. As in compact bone, lacunae contain osteocytes that nourish the mature bone tissue from the blood circulating through the trabeculae. Bone Formation Ossification or osteogenesis is the process of forming new bone. Bone formation occurs in four situations: Formation of bone in an embryo Growth of bones until adulthood Remodeling of bone Repair of fractures Bone Formation Osteogenesis occurs by two different methods, beginning about the 6th week of embryonic development. Intra-membranous ossification produces spongy bone. This bone may subsequently be remodeled to form compact bone. Endochondral ossification is a process whereby cartilage is replaced by bone. Forms both compact and spongy bone. Bone Formation Intra-membranous ossification is the simpler of the two methods. It is used in forming the flat bones of the skull, mandible, and clavicle. Bone forms from mesenchymal cells that develop within a membrane – without going through a cartilage stage. Many ossification centers.  Intra-membranous ossification Mesenchymal cell differentiate into osteoblast. Blood and lymphatic vessels grows Osteoblast → osteocytes in the surfaces (surrounded by ECM) of newly formed bones and develops Outer layer replaced by red bone compact bone and the marrow center remains spongy Bone Formation Endochondral ossification is the method used in the formation of most bones, especially long bones. It involves replacement of cartilage by bone. There are one primary and two secondary centers of growth. Endochondral ossification  Bone Structure Epiphyseal growth plate is a layer of hyaline cartilage in the metaphysis of a growing bone The growth plate is always actively dividing and causing the bone to elongate (only way to increase length from each end). As bone grows – chondrocytes proliferate on the epiphyseal side. Growth hormone stimulate liver New chondrocytes replaces the old ones to secrete insulin like growth factor (IGF-1) that stimulate which is destroyed and calcified – cartilage proliferation of chondrocytes, resulting in bone growth is replaced by bone on diaphysis end. During puberty, oestrogen increases, increasing chondrocytes apoptosis leading to ossification and EP closure (18-female; 21 years in males).  Bone Formation Ossification contributing to bone length is usually complete by 18-21 years of age. Bones can still continue to thicken and are capable of repair even after the epiphyseal growth plates have closed. Bone Structure In adults, the epiphyseal cartilage is no longer present and elongation of bones has stopped. The epiphyseal growth plate becomes an “epiphyseal line”, as growing cartilage is replaced by calcified bone. The epiphyseal line is visible externally and on X-rays. Factors Affecting Bone Growth and Remodeling A balance must exist between the actions of osteoclasts and osteoblasts. If too much new tissue is formed, the bones become abnormally thick and heavy (acromegaly): Growth hormone hypersecretion; in kids will result in gigantism (increase in length). Excessive loss of calcium weakens the bones, as occurs in osteoporosis (bone breakdown outpace bone formation). They may also become too “soft”, as seen in the bone diseases rickets (in children) and osteomalacia (in adult) (prolonged vitamin D deficiency – disrupts calcium absorption – lead to inadequate calcification of ECM).  Factors Affecting Bone Growth and Remodeling Normal bone metabolism depends on several factors: Minerals are an essential component. Large amounts of calcium and phosphorus and smaller amounts of magnesium, fluoride, and manganese are required for bone growth and remodeling. Factors Affecting Bone Growth and Remodeling Vitamins are also necessary for normal bone metabolism: Vitamin A stimulates activity of osteoblasts. Vitamin C is needed for synthesis of collagen. Vitamin D is essential to healthy bones because it promotes the absorption of calcium from foods in the gastrointestinal tract into the blood. Vitamins K and B12 are needed for synthesis of bone proteins.  Factors Affecting Bone Growth and Remodeling Hormones are key contributors to normal bone metabolism. During childhood, the hormones most important to bone growth are human growth hormone (hGH) and growth factors called IGFs (produced by the liver). Both stimulate osteoblasts, promote cell division at the epiphyseal plate, and enhance protein synthesis. Thyroid hormones and insulin also promote bone growth by stimulating osteoblasts and protein synthesis. Factors Affecting Bone Growth and Remodeling Hormones continued… The sex hormones (estrogen and testosterone) cause a dramatic effect on bone growth, such as the sudden “growth spurt” that occurs during the teenage years. The sex hormones also promote widening of the pelvis in the female skeleton. They are also responsible for closing the epiphyseal plates at the end of puberty. Factors Affecting Bone Growth and Remodeling Hormones continued… Parathyroid hormone (PTH) and calcitonin are critical for balancing the levels of calcium and phosphorus between blood and bone. Calcium Homeostasis Fracture and Repair Fracture is any break in bone The naming of fractures can be confusing because of the many different criteria that are used. Some schemes describe the anatomical appearance of the fracture: Partial, complete (fx is all the way through the bone), closed (simple), open (fx punctures the skin), “Green stick” (a small linear break in the bone cortex), impacted, comminuted, spiral, transverse, displaced Fracture and Repair Once a bone is fractured, repair proceeds in a predictable pattern: The first step, which occurs 6-8 hours after injury, is the formation of a fracture hematoma as a result of blood vessels breaking in the periosteum and in osteons.  Fracture and Repair The second and third steps involve the formation of a callus (takes a few weeks, to as many as six months). Phagocytes remove cellular debris and fibroblasts deposit collagen to form a fibro- cartilaginous callus... Fracture and Repair... which is followed by osteoblasts forming a bony callus of spongy bone. Fracture and Repair The final step takes several months and is called remodeling : Spongy bone is replaced by compact bone. The fracture line disappears, but evidence of the break remains. AXIAL SKELETON Divisions of the Skeletal System The human skeleton consists of 206 named bones grouped into two principal divisions: Axial skeleton Appendicular skeleton Divisions of the Skeletal System The axial skeleton consists of the bones that lie around the longitudinal axis of the human body: Skull bones, auditory ossicles (ear bones), hyoid bone (U-shaped bone below the skull), ribs, sternum (breastbone), and bones of the vertebral column The appendicular skeleton consists of the bones of the upper and lower limbs (extremities) and the bones forming the girdles that connect the limbs to the axial skeleton. Bones of the Axial Skeleton There are 80 bones in the central (axial) skeleton, comprising: Skull Vertebral column (including the sacrum) Ribs Sternum Bones of the Skull The skull protects and supports the brain and special sense organs. Besides forming the large cranial cavity, the skull also forms several smaller cavities. Nasal cavity Orbits (eye sockets) Paranasal sinuses Small cavities which house organs involved in hearing and equilibrium Bones of the Skull The bones of the skull are grouped into two categories: Cranial bones Facial bones Cranial bones Facial bones Bones of the Skull 8 Cranial Bones 14 Facial Bones (Bones of the Braincase) Mandible (1) Frontal bone (1) Maxilla (2) Parietal bone (2) Zygomatic bone (2) Temporal bone (2) Nasal bones (2) Occipital bone (1) Sphenoid bone (1) Lacrimal bones (2) Ethmoid bone (1) Palatine bones (2) Inferior Nasal conchae (2) Vomer (1)  Cranial bones The braincase (neurocranium) has 8 bones: Frontal bone (1) Parietal bone (2) Temporal bone (2) Occipital bone (1) –Not shown Sphenoid bone (1) Ethmoid bone (1)  Cranial bones Frontal bone (1) Parietal bone Sphenoid bone (2) (1) Temporal bone (2) Ethmoid bone (1) Occipital bone (1) Cranial bones A suture is a “seam” – an immovable joint between bones of the skull. Coronal Suture Squamous Suture Lambdoidal Suture Saggital suture that unites the 2 parietal bones Cranial bones Fontanels (“little fountains”) are soft, mesenchyme-filled spaces between cranial bones in babies. They will become suture joints in adults. Cranial bones Of the 8 cranial bones that fit together to form the braincase, the sphenoid bone is the “keystone”. Like the keystone of a Roman arch, the sphenoid is the “center brick” that balances the outward thrust of the other bones. Representation of a Roman Arch The Sphenoid bone The rest of the braincase bones are dependent for support on the sphenoid bone (with its greater and lesser wings).  Bones of the Skull - 14 Facial Bones Perpendicular plate of the ethmoid Nasal bones (2) bone Lacrimal bone (2) Zygomatic bone Middle nasal concha (2) Vomer (1) Inferior nasal concha (2) Maxilla (fused) (2) Mandible (1) Palatine bones (2) (Not shown) Bones of the Skull Besides protecting the brain, the skull provides a framework for: Attachment of muscles that move various parts of the head Attachment for muscles that produce facial expressions The facial bones form the framework of the face and provide support for the entrances to the digestive and respiratory systems.  The Vertebral Column The spine is composed of a series of bones called vertebrae. Vertebrae typically consist of: A body (weight bearing) A pedicle and lamina forming the vertebral arch (surrounds the spinal cord) Several processes (points of attachment for muscles) The Vertebral Column There are 7 cervical vertebrae in the neck region labeled C1-C7. There are 12 thoracic vertebrae that articulate with the ribs (T1-T12). There are 5 lumbar vertebrae that support the lower back labeled L1-L5. The sacrum and coccyx are single bones that result from the fusion of several vertebrae. The Vertebral Column From the cervical region to the sacrum, each vertebra has a large central hole, or vertebral foramen in which the spinal cord can travel. At each segmental level, on both the right and left sides, an intervertebral foramen is formed for the exiting spinal nerves. The Vertebral Column A tough fibrocartilage intervertebral disc is found between the bodies of adjacent vertebrae. It functions to absorb vertical shock and form joints which are strong yet still permit movement of the spine. The Vertebral Column When viewed from the front, a normal adult vertebral column appears straight. When viewed from the side, it has four slight bends which constitute the normal spinal curvatures. Vertebral Column Relative to the front of the body, the cervical and lumbar curves are convex (bulging out), The thoracic and sacral curves are concave (cupping in). The Vertebral Column Various conditions may exaggerate the normal spinal curves, sometimes causing severe disability. Lateral bending - congenital Hunchback look – in Hollow back – deformities, paralysis of elderly due to increase weight of one side of muscle degeneration of the abdomen intervertebral disc, poor posture  The Thorax The thoracic cage is the final part of the axial skeleton. It is formed from: Thoracic vertebrae (T1-T12) Sternum (breastbone) Ribs (12) Costal cartilages (bars of hyaline cartilage connecting the sternum to the ribs – provide elasticity) The Thorax The upper 7 rib pairs are called true ribs because they attach “directly” to the sternum (with just a small piece of costal cartilage). The bottom 5 pairs of ribs (and this number can vary from one individual to another) are called false ribs. They attach indirectly to the sternum with an elongated piece of costal cartilage… … or not at all (ribs 11 and 12 are called floating ribs.) APPENDICULAR SKELETON PHC411 Gurmeet Kaur Surindar Singh (L7,FF1)  The Appendicular Skeleton The 126 bones of the appendicular skeleton are primarily concerned with movement. As “appendages” to the central skeleton, these bones include those of the upper and lower limbs (including the girdles that attach them to the axial skeleton). The Upper Limb Based on the position of its major joints and component bones, the upper limb is divided into the shoulder, arm, forearm, and hand: The shoulder - attachment to the trunk. The arm - between the shoulder and the elbow joint. The forearm - between the elbow and the wrist. The hand - distal to the wrist.  The Shoulder/Pectoral Girdle The bones of the shoulder (pectoral) girdle include the scapula and the clavicle. The shoulder joint also incorporates the upper part of the humerus. The Shoulder/Pectoral Girdle The Shoulder/Pectoral Girdle spine acromion coracoid glenoid Right scapula (shoulder blade), posterior and lateral view Spine - a large process on the posterior of the scapula Acromion - the flattened lateral portion of the spine that join the clavicle Coracoid process - a protruding projection on the anterior surface just inferior to the lateral aspect of the clavicle Glenoid cavity - shallow concavity that articulates with the head of the humerus The Shoulder/Pectoral Girdle The clavicle is “S” shaped: The medial end articulates with the manubrium of the sternum forming the sternoclavicular joint. The lateral end articulates with the acromion of the scapula forming the acromioclavicular joint. Join the scapula Join the sternum  The Arm The only bone in the arm is the humerus. The head of the humerus has two projections: Greater tubercle (lateral) Lesser tubercle (anterior) intertubercular groove or sulcus groove Proximally: The glenoid cavity of the scapula articulates with the head of the Humerus Distally: articulate with the radius and ulna  The Forearm The two bones of the forearm are the radius and ulna: The radius is lateral (in anatomic position) and widens distally. The more medial ulna widens proximally into the Olecranon process, a large prominence we feel as the tip of the elbow. olecranon The radius head articulate with the ulna The Hand The hand is composed of the wrist, the palm, and the fingers. The wrist, or carpus, is made up of 8 carpal bones arranged in two rows. The palm of the hand has 5 metacarpal bones. Each finger, with the exception of the thumb or 1st digit, is composed of 3 phalanges proximal phalanx middle phalanx distal phalanx The Hand The Lower Limb is divided into Pelvic girdle The thigh is between the hip and the knee joint. The leg is between the knee and the ankle. The foot is distal to the ankle.  The Pelvic Girdle os coxae (hip bone) In the gluteal region, the pelvic girdle is made up of two os coxae, or hip bones. Each coxal (hip) bone consists of 3 bones that fuse together: Ilium Ischium Pubis The Male/Female Pelvis Compared to the female pelvis, the male pelvis: Is larger, heavier, and more narrow Has a smaller inlet and outlet Has a pubic arch angle of < 90o Male Pelvis  The Male/Female Pelvis Compared to the male pelvis, the female pelvis: Is rounder, has a flared iliac crest, and a wider pelvic opening to assist childbirth. It also has a pubic arch angle of > 90o and a more moveable pubic symphysis. Has a more flexible coccyx Female Pelvis  The Thigh Common site of fracture The femur is the longest, heaviest, and strongest bone of the thigh, and in the entire body. Proximally, the head articulates with the acetabulum of the hip bone forming the hip (coxal) joint. femoral condyles Distally, the medial and lateral femoral condyles articulate with the tibia to form the knee joint. The femur also articulates with patella. The Thigh The patella (knee cap) is the largest and only named sesamoid bone in the body. A thick articular cartilage lines the posterior surface.  The Leg The tibia/shin bone (always medial) is the largest and bears all the weight. Proximal end articulate with the femur. Distally articulate with the talus of the ankle and the fibula. The fibula is the smaller, laterally placed bone of the leg: It is non-weight bearing (but stabilize ankle joint) The head forms the proximal tibiofibular joint (does not articulate with femur). At the distal end, articulates with the tibia and the talus at the ankle. The Foot The tibia and fibula articulate with the talus bone of the ankle to form the ankle “mortise” (ankle joint). The Foot The ankle, or tarsus, is made up of 7 tarsal bones arranged to form the ankle mortise, heel, and arches. The largest and strongest tarsal bone, the calcaneus, forms the heel.  The Foot Like the palm of the hand, the sole of the foot has 5 bones – in this case called metatarsals. The metatarsals also participate in forming the arches of the foot. The Foot Each toe with the exception of the hallux (big toe) is composed of 3 phalanges: proximal phalanx middle phalanx distal phalanx The Lower Limb The longitudinal and transverse foot arches support the weight of the body while providing spring and leverage to the foot when walking. Flatfeet occur when the arches decrease or “fall”. JOINTS Joint Classification Structural classification subcategories include: Fibrous joints (bones held together by dense collagen fibers) Cartilaginous joints (bones held together by cartilage) Synovial joints (bones held together by ligaments) Functional classification subcategories include: Synarthrosis (an immovable joint- like the fibrous joints of the skull) Amphiarthrosis (a slightly movable joint - cartilaginous pubic symphysis) Diarthrosis (a freely movable joint - joints of the shoulder and hip) FIBROUS JOINTS In fibrous joints the bones are united by dense connective tissue consisting of collagen fibers which run between the bones. There is no joint cavity. most of the fibrous joints are immovable - a few are slightly movable. FIBROUS JOINTS 3 subtypes of fibrous joints: A. Suture: Bones are held together by a thin layer of dense fibrous tissue and also by interlocking projections of the bones. The connecting fibers holding bones together are short. This type of joint occurs only in the skull: cranial sutures. FIBROUS JOINTS B. Syndesmosis: Bones are held together by a cord (ligament) or sheet of dense fibrous connective tissue (interosseous membrane). The connecting fibers holding bones together are long. Examples:- radius and ulna (interosseous membrane) tibia/fibula joint (Ligament) FIBROUS JOINTS C. Gomphosis: It is a peg-in-socket fibrous joint. The only examples are the articulations of teeth (the peg) with their alveolar sockets in the mandible or the maxillae. The thin fibrous membrane that hold teeth inside their alveolar sockets is called the periodontal ligament. CARTILAGINOUS JOINTS In cartilaginous joints the bones are united with each other by cartilage. No joint cavity. 2 subtypes of cartilaginous joints: Synovial joints The majority of articulations between bones are synovial joints. All synovial joints are freely moveable joints. They are characterized by the presence of a closed space or CAVITY between the bones: the joint cavity (= synovial cavity). A two layered capsule encloses the synovial cavity: An outer fibrous capsule An inner synovial membrane (secretes the synovial fluid) Synovial joints Synovial fluid which functions to reduce friction by lubricating the joint and absorbing shocks. The synovial membrane supplies oxygen and nutrients to the cartilage, while removing carbon dioxide and metabolic wastes. The major joints of the arms, hips, and legs Types of Synovial Joints There are 6 types of synovial joints based on the shapes of the articulating bone surfaces. plane joint pivot joint saddle joint hinge joint condyloid joint ball-and-socket joint Aging and Arthroplasty The effect of aging on joints varies considerably from person to person. By age 80, almost everyone develops some type of degeneration in the knees, elbows, hips, and shoulders. Osteoarthritis is at least partially age-related. Aging results in thinning of the articular cartilage and decreased production of synovial fluid in joints. Ligaments shorten and lose elasticity. Aging and Arthroplasty Joint arthroplasty is the surgical implantation of an artificial joint. The most commonly replaced are the hips, knees, and shoulders. Partial hip replacements involve only the femur, while total hip replacements involve both the acetabulum and head of the femur. Aging and Arthroplasty Aging and Arthroplasty Potential complications of arthroplasty include infection, blood clots and nerve injury. Aging and Arthroplasty Components of an artificial knee End of Chapter 9 Copyright 2012 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. 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