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PreClinEazy X Cardiff Medsoc The Human Skeleton Shivraj Paneer SelvamThe Human Skeleton Skeleton Organisation Types of Bones Bone Joints Bone Cells Microanatomy of Bone Dense connective tissue with specialised cells & ground substance Similar to cartilage but the ECM is calcified. Its rigid & inflexible. Involved in weight bearing & Bones mechanical support. The Bony matrix is 35% organic & 65% inorganic components Examples of organic components include type 1 collagen and inorganic include calcium phosphateSkeleton Organisation A) Long Adam was playing rugby when he fell on an outstretched hand. Upon getting an x-ray done, he was B) Flat told that he had fractured a very common bone associated with that kind of fall. C) Irregular What type of bone is the bone that was fractured? D) Short E) Sesamoid A) Long Adam was playing rugby when he fell on an outstretched hand. Upon getting an x-ray done, he was B) Flat told that he had fractured a very common bone associated with that kind of fall. C) Irregular What type of bone is the bone that was fractured? D) Short Scaphoid bone is fractured and it’s a short bone. E) Sesamoid Long Bones Short Bones Flat Bones Type of Bones Irregular Bones Sesamoid BonesLong Bones • They are tubular structures. • Involved in supporting movement & body weight. INSERT IMAGE HERE • Found mainly in the appendicular skeleton. • Examples include bones in the upper limb like the humerus & bones in the lower limb like the femur and phalangesShort Bones • They are cuboidal in shape. • They provide stability and offer some movement. INSERT IMAGE HERE • They are only found in the ankle (tarsus) and wrist (carpus).Flat Bones • They are shield-like. • Hence, they offer protection for internal organs such as the heart. INSERT IMAGE HERE • They are found in the skull, pelvis and help form the thorax. • They can also provide large attachment points for muscles. • Source of red blood cells (hematopoiesis).Irregular Bones • They vary in shape and structure. • It helps aid in protecting organs. • Examples include bones of the INSERT IMAGE HERE vertebrae, pelvis and face.Sesamoid Bones • They develop in certain tendons. • They protect tendons from stress and wear. INSERT IMAGE HERE • They also change the angle of the tendons as they pass to their attachments. • Examples include the patella. It’s also found in the hands and feet. Joints ● Place of union between 2 or more rigid structures. Fibrous Cartilaginous Synovial • Bones are united by • Hyaline cartilage • Most common joint. fibrous tissue. (synchondroses). Allows • Freely movable. • No/limited movement. growth & slight bending • Cavity filled with • Movement is dependent in early life. synovial fluid. on length of fibres. • Fibrocartilage • Nourishes articular • Syndesmosis vs (symphysis). Slightly cartilage & lubricates Gomphosis strong & mobile. joint. A) Synovial ⇒ interphalangeal Felix was gaming on his console when he began to notice his thumb was getting increasingly painful, B) Hinge ⇒ carpometacarpal especially at the joint in his thumb, nearest to his nail. C) Hinge ⇒ interphalangeal What type of joint is that? D) Saddle ⇒ carpometacarpal E) Synovial ⇒ carpometacarpal A) Synovial ⇒ interphalangeal Felix was gaming on his console when he began to notice his thumb was getting increasingly painful, B) Hinge ⇒ carpometacarpal especially at the joint in his thumb, nearest to his nail. C) Hinge ⇒ interphalangeal What type of joint is that? D) Saddle ⇒ carpometacarpal E) Synovial ⇒ carpometacarpal Saddle Joint Hinge Joint Plane Joint ● They only allow flexion & ● Allow gliding or sliding. ● Permits head movement in 2 different planes. extension ● Example: Acromioclavicular Joint ● Example: Elbow Joint ● Example: Carpometacarpal Joint Types of Synovial Joints Ball & Socket Joint Condyloid Joint Pivot Joint ● Allows for flexion, extension, ● Round head fits into concave ● A rounded part of bone fits into structure. abduction, adduction & a ligamentous socket. circumduction ● Enables movement in 3 planes ● Allows rotation ● Example: Hip Joint ● Example: Metacarpophalangeal ● Example: Atlantoaxial Joint JointBone Cells Osteoblasts Osteoclasts Osteocytes • Builds Bone • Crushes bone by • Monitor bone. • Secretes collagen and secreting H+ & • Formed from catalyses collagenases. trapped osteoblasts mineralisation in an • Differentiates from • Same origin as alkaline environment macrophage/monocyte osteoblasts. via ALP lineage precursors • Differentiates from • Osteoporosis = too mesenchymal stem many osteoclasts. cells in periosteum. Osteoprogenitor Cells Originates from mesenchymal stem cells. ● Found in marrow & deep layers of periosteum. ● Eventually develops into osteoblasts under low strain & high O2. ● Develops into cartilage under opposite conditions. ● Cstrainelop into fibrous tissue too under high A) Periosteum Eliza, a 1st year medical student, was reading about bones. She came across a structure that that lines the B) Concentric Lamellae inner lumen of bones. C) Interstitial lamellae What is the name of that structure? D) Endosteum E) Cement Line A) Periosteum Eliza, a 1st year medical student, was reading about bones. She came across a structure that that lines the B) Concentric Lamellae inner lumen of bones. C) Interstitial lamellae What is the name of that structure? D) Endosteum E) Cement LineMicroanatomy of Bone Microanatomy of Bone • Bony tissue is formed by a inner layer of spongy bone & an outer layer of compact bone. • Compact bone is formed by units called osteons. • Osteons are made of layers of calcified bony matrix called lamellae. • Between lamellae lies fluid filled spaces called lacunae, which contain osteocytes • Osteocytes communicate with Haversian Canal and each other through cytoplasmic processes called canaliculi. Concentric Lamellae • Concentric layers of collagen that is calcified that surround osteon lumen that give bone strength. • • Remains of old osteons that exist between current ones. Interstitial Lamellae Cement Line Endosteum Perichondrium ● Covers cartilage on the end of • Outermost region of a • Inner lining of lumen in bones. single osteon. bone ● Like periosteum, it helps new • Made of progenitor cells. cartilage to grow Spongy Bone (20%) Compact Bone (80%) Periosteum • More Dense • Less dense • It’s a sheath outside of bones. • Consists of trabeculae • Forms cortex/ hard • Supplies blood, nerves & cells • Produces RBCs and regulates shell of most bones in that aid in growth & repair. repair. body ⇒ strength Hematoma Inflammation Granulation Bone Healing Callus Consolidation & Remodelling R eferences First AID for the USMLE STEP 1 2020 edition https://www.visiblebody.com/learn/skeleton/types-of-bones https://www.orthobullets.com/basic-science/9002/bone-cells https://biologydictionary.net/compact-bone/ https://my.clevelandclinic.org/health/body/22740-periosteum#:~:text=The%20periosteum%20i https://www.scientistcindy.com/the-appendicular-skeleton.html https://eu1.kuracloud.com/i/23dac560/student/courses/63/runs/18137/preview/page/3PLEASE FILL OUT THE FEEDBACK FORM PLEASE TUNE IN TO OUR REMAINING SESSIONS THIS WEEK