Skeletal System: Structure and Function PDF

8/27/24, 6:12 PM Platform | Study Fetch The Skeletal System: Structure and Function Types of Skeletons and Bone (00:00:37 - 00:00:58) Exoskeleton vs. Endoskeleton: Exoskeleton: Skeleton on the outside of the body, made of ch...

8/27/24, 6:12 PM Platform | Study Fetch The Skeletal System: Structure and Function Types of Skeletons and Bone (00:00:37 - 00:00:58) Exoskeleton vs. Endoskeleton: Exoskeleton: Skeleton on the outside of the body, made of chitin or calcium (e.g., beetles, spiders, shrimp, snails, scallops) Endoskeleton: Skeleton inside the body, found in mammals like us Axial and Appendicular Skeletons: Axial Skeleton: Includes the hyoid bone, auditory ossicles, rib cage, skull, and vertebral column Appendicular Skeleton: Includes the limbs and girdles (shoulder and pelvic) Types of Bones: Flat Bones: e.g., skull, scapula, sternum Long Bones: e.g., femur, tibia, humerus, radius, ulna Irregular Bones: e.g., vertebrae, carpals, tarsals Sesamoid Bones: e.g., patella Short Bones: e.g., carpals, tarsals Bone Structure and Remodeling (00:01:47 - 00:03:51) Long Bone Anatomy: Epiphysis: Ends of the long bone, covered in articular cartilage Diaphysis: Shaft of the long bone, composed of dense cortical bone Medullary Cavity: Hollow center of the diaphysis, contains yellow bone marrow Metaphysis: Region between the medullary cavity and epiphyseal plate Epiphyseal Plate: Cartilage plate where bone growth occurs, fuses at the end of puberty Bone Composition: Cortical (compact) bone forms the dense outer layer Cancellous (trabecular) bone is the spongy, porous inner bone Bone Remodeling: Cartilage bones form first in utero, then ossify (turn to bone) Ossification centers form at the middle and ends of the bones Epiphyseal plate allows for longitudinal bone growth during childhood and adolescence Epiphyseal plate fuses at the end of puberty, ending bone growth Connective Tissue and Joints (00:03:51 - 00:04:16) Connective Tissue: https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc9f069b6d6b89c5eb4/document?go=note 1/7 8/27/24, 6:12 PM Platform | Study Fetch Ligaments connect bones to bones Tendons connect muscles to bones Joints: Synovial joints have a synovial membrane and fluid, allowing for smooth movement Examples include ball-and-socket, hinge, pivot, and gliding joints Types of Bones in the Endoskeleton (00:04:16 - 00:04:31) Short Bones: Cuboidal in shape Support the body Tend to be in close-knit groups Examples include carpals in the wrist and tarsals in the ankles (00:04:31 - 00:04:42) Flat Bones: Consist of a cancerous bone layer sandwiched between two compact or cortical bone layers Examples include bones of the skull, sternum, and some in the hip Provide protection to softer internal structures like the heart, lungs, and brain (00:04:42 - 00:04:54) Sesamoid Bones: Embedded within tendons Help to amplify the muscle's power A good example is the patella in the knee (00:04:54 - 00:05:22) Irregular Bones: Bones that don't fit well into the other classification schemes Examples include the spine and some parts of the pelvis Have specialized functions that don't fit neatly into other categories (00:05:22 - 00:06:00) Mnemonic for Types of Bones: Long Bones: Long and allow for mobility and structural support (e.g., humerus, femur) Short Bones: Short and fat, cuboidal, found in groups (e.g., wrist, ankle) Flat Bones: Have a cortical bone layer sandwiching a cancerous bone layer (e.g., skull, sternum) Sesamoid Bones: Embedded in tendons (e.g., patella) Irregular Bones: Don't fit into other categories (e.g., spine) Cortical vs. Cancerous Bone (00:06:15 - 00:06:42) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc9f069b6d6b89c5eb4/document?go=note 2/7 8/27/24, 6:12 PM Platform | Study Fetch Cortical Bone: The outer, harder layer of bone Cancerous Bone: The inner, spongy layer of bone (00:06:42 - 00:07:18) Cortical Bone Structure: Osteons: The individual functional units Haversian Canals: Run through the osteons, contain blood supply Lamellae: The layers that wrap around the osteons Lacunae: Spaces where the osteocytes (bone cells) are embedded Canaliculi: Tiny canals that connect the lacunae (00:07:18 - 00:08:10) Haversian System: Osteons are arranged with their Haversian canals running parallel to the long axis of the bone Perforating (Volkmann's) Canals: Connect the Haversian canals, allowing blood vessels to penetrate the bone Cortical Bone Structure Description Osteons Individual functional units Haversian Canals Run through osteons, contain blood supply Lamellae Layers wrapping around osteons Lacunae Spaces where osteocytes are embedded Canaliculi Tiny canals connecting lacunae The Haversian system, with its parallel Haversian canals and connecting Volkmann's canals, allows for efficient vascularization and nutrient delivery throughout the cortical bone. Bone Structure and Remodeling Cancerous Bone Structure (00:08:10 - 00:08:32) Cancerous bone contains a web of trabecula Trabecula are scaffolding structures that still have osteocytes and canaliculi like cortical bone They are arranged in a spongiform manner to support the structure This makes room for the red bone marrow that needs to fill the space https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc9f069b6d6b89c5eb4/document?go=note 3/7 8/27/24, 6:12 PM Platform | Study Fetch Bone Anatomy (00:08:32 - 00:08:56) Long bones have: Spongy bone at the epiphysis (ends) Compact bone on the outer sides Medullary cavity filled with yellow marrow Bone Layers (00:09:09 - 00:09:31) Periosteum: Membrane covering the bone, supplies blood flow Cortical (compact) bone: Hard outer layer Trabecular (spongy) bone: Internal scaffolding structure Cartilage: Smooth surface for articulation at the epiphysis Growth plate (epiphyseal plate) in adolescence Cortical Bone Structure (00:09:43 - 00:10:22) Cortical Bone Mnemonic: Cortical bone is the hard outer layer Lamellae are the layers of an osteon, like the layers of an onion Lacunae connect to each other and the central Haversian canal via canaliculi Lamellae resemble canals Osteons are the basic structural units of cortical bone Haversian canals run through the center of osteons Perforating (Volkmann's) canals connect the Haversian canals Bone Remodeling (00:10:32 - 00:12:09) Stages of Bone Remodeling Osteoclasts: Derived from monocytes, dissolve bone Monocytes: Circulating cells that differentiate into osteoclasts Pre-osteoblasts: Derived from mesenchymal stem cells, differentiate into osteoblasts Osteoblasts: Build new bone, become embedded as osteocytes Osteocytes: Mature bone cells embedded in the matrix Bone Modeling and Remodeling Mnemonic Osteoblasts build bone Osteoclasts chew (or cleave) bone https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc9f069b6d6b89c5eb4/document?go=note 4/7 8/27/24, 6:12 PM Platform | Study Fetch Endochondral vs. Intramembranous Ossification Endochondral Ossification: Bone forms by replacement of cartilage template Intramembranous Ossification: Bone forms directly from mesenchymal tissue without a cartilage intermediate Parathyroid Hormone, Calcitonin, and Vitamin D (00:12:21 - 00:13:45) Parathyroid Hormone (PTH): Released by the parathyroid gland Increases calcium levels in the blood Stimulates osteoclasts to break down bone, releasing calcium into the blood Vitamin D: Increases calcium levels in the blood Does this by: Increasing calcium absorption from the gut Stimulating osteoclasts to break down bone Calcitonin: Decreases calcium levels in the blood Does this by depressing osteoclasts However, PTH is the main regulator of calcium balance Endochondral Ossification (00:13:45 - 00:15:21) Process: 1. Chondrocytes lay down hyaline cartilage 2. Ossification centers form within the cartilage 3. Osteoblasts lay down new bone, replacing the cartilage 4. Leads to the formation of the epiphyseal plate Intramembranous Ossification (00:14:24 - 00:15:21) Process: 1. Osteoblasts secrete osteoid (collagen-rich matrix) 2. Osteoid is then calcified into woven bone 3. Woven bone is remodeled into compact bone 4. Bone is created directly within a membrane, without the cartilage scaffold https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc9f069b6d6b89c5eb4/document?go=note 5/7 8/27/24, 6:12 PM Platform | Study Fetch Connective Tissue and Joints (00:15:37 - 00:16:14) Types of Connective Tissue: Fibrous connective tissue Cartilage Joints Ligaments and Tendons: Ligaments connect bone to bone Tendons connect muscle to bone Periosteum and Endosteum (00:16:14 - 00:16:31) Periosteum: Covers the cortical bone Endosteum: Lies between the cortical bone and the cancellous bone layer Both the periosteum and endosteum contribute to bone growth Cartilage and Bone Formation (00:16:31 - 00:16:42) Both the periosteum and endosteum are important structures that contribute to the formation of new bone. These layers provide nutrients and a supportive structure for the bone, and can also contribute to the healing process if a bone is fractured. (00:16:42 - 00:16:58)Types of Cartilage: Hyaline Cartilage: The main type of cartilage found in joints. It is a clear, flexible, and less dense cartilage compared to fibrocartilage. (00:16:58 - 00:17:12) Fibrocartilage: Found in intervertebral discs, menisci of the knee, and other areas. It is made up of dense layers of collagen, making it very tough and strong. (00:17:12 - 00:17:24) Elastic Cartilage: Contains visible elastic fibers that make it very stretchy and flexible. This allows for deformation and quick recoil, as seen in the ears and epiglottis. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc9f069b6d6b89c5eb4/document?go=note 6/7 8/27/24, 6:12 PM Platform | Study Fetch (00:17:24 - 00:17:38) Chondroblasts secrete collagen and elastin, which are the main structural components of the skin and other tissues. (00:17:38 - 00:17:55) Collagen acts like steel cables, providing resistance to tension and keeping the skin from pulling apart. Elastin gives the skin elastic properties, allowing it to deform and spring back into shape. (00:17:55 - 00:18:06) Both collagen and elastin break down with age, leading to wrinkles as the skin loses its ability to deform and recoil. Structure of Synovial Joints (00:18:21 - 00:18:38)Key structures of a synovial joint: Bones Articular cartilage Ligaments Fibrous joint capsule Synovial fluid (lubricant) (00:18:38 - 00:18:52) The synovial membrane lines the joint cavity, which is filled with synovial fluid. The fluid and cartilage provide lubrication for the joint. (00:18:52 - 00:19:04) Osteoarthritis can occur if the cartilage wears out, leading to bone-on-bone friction, pain, and breakdown of the bone. Joint replacement surgery may be the only solution in severe cases. (00:19:04 - 00:19:18)Types of Synovial Joints: Pivot joints Hinge joints Saddle joints Plane joints Condyloid joints Ball and socket joints (00:19:18 - 00:19:39) Understanding the type of synovial joint can help you analyze the function and movement of a joint. Knowing the joint type can also aid in answering questions about the skeletal system. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc9f069b6d6b89c5eb4/document?go=note 7/7