19_Skeletal+System+Bone+and+Cartilage+Tissue.pptx

Bone Tissue and Skeletal System Chapter 5, Human Anatomy (LibreTexts) "Skeleton Sitting Smiling " by Clker-Free-Vector-Images is in the Public Domain, CC0 Components of the Skeletal System • The skeletal system is the body system composed of • Bone (osseous tissue): solid supportive connective ti...

Bone Tissue and Skeletal System Chapter 5, Human Anatomy (LibreTexts) "Skeleton Sitting Smiling " by Clker-Free-Vector-Images is in the Public Domain, CC0 Components of the Skeletal System • The skeletal system is the body system composed of • Bone (osseous tissue): solid supportive connective tissue • Cartilage: semi-rigid supportive connective tissue • Ligaments: dense regular connective tissue • Skeleton is composed of two major divisions: • Axial skeleton is the vertical, central axis of the body and includes all bones of the head, neck, chest, and back. • Appendicular skeleton includes all bones of the upper and lower limbs, plus the bones that attach each limb to the axial skeleton. Functions of the Skeletal System • Functions • • • • • supports the body facilitates movement protects internal organs produces blood cells stores and releases minerals and fat "Bones Protect Brain" by OpenStax is licensed under CC BY 3.0 Supportive Connective Tissues • Allow the body to maintain its posture and protect internal organs • Two major forms • Cartilage: semisolid extracellular matrix; cells are called chondrocytes; avascular. • Bone: solid extracellular matrix; cells are called osteocytes; vascular. Growth of Cartilage • Two types of growth but very similar: within the cartilage (interstitial) or along the outside edge (appositional) • Chondrocytes produce extracellular matrix which is semi-solid. This process locks chondrocytes inside spaces called lacunae. • Subsequent mitotic division of a chondrocyte in one lacuna produces two daughter chondrocytes that are pushed apart. Each new chondrocytes will produce new extracellular matrix. Functions of Cartilage • Semi-solid connective tissue that is weaker than bone but flexible and resilient. • Support soft tissues i.e. tracheal cartilage • Lines gliding surface of articulations (where bones meet) • Precursor model for bone growth i.e. in embryo Types of Cartilage • 3 types: • Hyaline cartilage • Fibrocartilage • Elastic cartilage Hyaline Cartilage Hyalos = glass Most common type of cartilage, but also the weakest Glassy matrix; chondrocytes in lacunae Forms fetal skeleton (model for bone growth), smooths joint surfaces • Example: articular ends of long bones (epiphyseal plate), costal (ribs) cartilage, trachea, nose • • • • "Types of Cartilage" by OpenStax is licensed under CC BY 3.0 Fibrocartilage • Parallel collagen fibers in matrix • Chondrocytes in lacunae in parallel rows • Absorbs shock, extremely durable • Example: intervertebral discs, pubic symphysis, menisci of knee joint "Types of Cartilage" by OpenStax is licensed under CC BY 3.0 Elastic Cartilage • Chondrocytes in lacunae, similar to hyaline cartilage • Small amount of extracellular matrix organized in a weblike mesh around lacunae • Extremely resilient and flexible • Example: epiglottis, ear "Types of Cartilage" by OpenStax is licensed under CC BY 3.0 Functions of Bone • More solid and greater support compared to cartilage • Support and protection of more delicate organs • Movement: attachment site for muscles • Hemopoiesis: blood cell production in red bone marrow • Storage of mineral and energy reserves i.e. yellow bone marrow Bone Cells and Tissue • Bone tissue is solid with a relatively small number of cells • Cells • Osteogenic cells – develop into osteoblasts • Osteoblasts – responsible for formation of bone extracellular matrix • Osteocytes - maintain mineral concentration of extracellular matrix. Osteocytes are housed in a lacunae and nourished via canaliculi • Osteoclasts – responsible for bone resorption which is the breakdown of bone tissue to release minerals Bone Cells "Bone Cells" by OpenStax is licensed under CC BY 3.0 Bone Matrix and Tissues • Extracellular matrix of collagen fibers produced by osteocytes • Provides a surface for inorganic salt crystals to adhere. Salts crystals are made by the combination of calcium phosphate and calcium carbonate to form hydroxyapatite, which incorporates other inorganic salts. • Salt crystals give bones their hardness and strength, while the collagen fibers give them flexibility so that they are not brittle. • Two forms of bone tissues: compact bone and spongy bone. Both found in all bones. Compact Bone • Dense and strong to withstand compressive forces • Structural unit is cylindrical osteon • Osteon is composed of concentric rings of calcified matrix called lamellae • Central canal at the center contains blood and lymphatic vessels • Osteocytes in lacunae are found in the borders of adjacent lamellae and are nourished through canaliculi Compact Bone Under the Microscope “Compact Bone" by Jennifer MacDonald, Histotechnology Program, Mt. San Antonio College is licensed under CC BY-NC 4.0 Compact Bone (Image) "Diagram of Compact Bone" by OpenStax is licensed under CC BY 3.0 Osteon "Osteon" by Whitney Menefee is a derivative from the original work of Daniel Donnelly and is licensed under CC BY 4.0 Spongy Bone • Also known as cancellous bone • Strong but light in weight • Arranged in a lattice-like network of matrix spikes called trabeculae • Trabeculae host parallel lamellae, canaliculi and osteocytes • Osteocytes in lacunae Spongy Bone Under the Microscope “Bone Tissue" by Jennifer MacDonald, Histotechnology Program, Mt. San Antonio College is licensed under CC BY-NC 4.0 Spongy Bone (Image) "Spongy Bone" by OpenStax is licensed under CC BY 3.0 Activities • Take pictures of 6 histological slides • Classify them based on muscle/cartilage tissue: o o o o o o Skeletal muscle Cardiac muscle Smooth muscle Hyaline cartilage Fibrocartilage Elastic cartilage • Draw pictures on manual: page 4 and 7 • Take a model of muscle or bone and identify the lab terms in it Categories of Bones • The adult skeleton is composed of 206 bones • Divided into five categories based on their shapes • Long Bones – longer than it is wide. Function as levers. • Short Bones – cube-like. Provide stability and support • Flat Bones – thin. Serve as points of attachment for muscles and often protect internal organs • Irregular Bones – no easily characterized shape. Protect internal organs • Sesamoid Bones – small, round (sesame seed shape). Protect tendons from compressive forces Classifications of Bones "Bone Classification" by OpenStax is licensed under CC BY 3.0 Gross Anatomy of Bone I • Parts of a long bone 1. Epiphysis • Proximal and distal ends of the bone • Contains spongy bone • Covered by articular cartilage which is composed of hyaline cartilage 2. Metaphysis • Narrow space between epiphysis and diaphysis • Contains epiphyseal plate 3. Diaphysis • Contains medullary cavity that contains blood vessels and yellow bone marrow Anatomy of a Long Bone "Anatomy of a Long Bone" by OpenStax is licensed under CC BY 3.0 Gross Anatomy of Bone II • Two connective tissues line the outside and inside of long bones • Periosteum • • • • Dense irregular connective tissue Covers the outer surface of bone Contains blood vessels, nerves, and lymphatic vessels Point of attachment for tendons and ligaments • Endosteum • Reticular connective tissue • Lines the medullary cavity • Where bone growth, repair, and remodeling occur Periosteum and Endosteum "Periosteum and Endosteum" by OpenStax is licensed under CC BY 3.0 Ossification • Ossification = formation of new bone • Bone forms using a cartilage template • Process starts in embryo at –12 weeks and continue into adulthood • There are two patterns: • Intramembranous Ossification: develops from mesenchyme (an embryonic connective tissue). Produces flat bones of the face, most of the cranial bones, and the clavicles • Endochondral Ossification: begins with hyaline cartilage model. Produces bones at the base of the skull and long bones. Cartilage remains at epiphyseal (growth) plate until final ossification which leaves epiphyseal line. Intramembranous Ossification "Intramembraneous Ossification" by OpenStax is licensed under CC BY 3.0 Endochondral Ossification "Endochondral Ossification" by OpenStax is licensed under CC BY 3.0 Endochondral Ossification "Endochondral Ossification" by OpenStax is licensed under CC BY 3.0 Growth of Bones in Adulthood • When epiphyseal plate has ossified, bones can not grow in length anymore. • However, bones can still grow in width (diameter): osteocytes in periosteum lay down bone matrix in parallel layers. Osteoclasts expand medullary cavity. How Bones Grow in Diameter “Appositional Growth" by Daniel Donnelly is licensed under CC BY 4.0 Bone Remodeling • Bone continues to grow and renew itself throughout life. 20% of the adult human skeleton is replaced every year. • Bone remodeling: continual deposition of new bone (bone formation) and removal of old bone (resorption). • Prior and throughout puberty, bone formation is higher than resorption • After puberty, bone formation is equal to resorption • In older adults, bone formation is lower than resorption (osteoporosis) • Helps maintain calcium and phosphate levels in the body • Can be stimulated by stress on a bone i.e. exercise • Nutrients and hormones help regulate bone remodeling Bone Fracture Repair • Breaks in bones, called fractures, can be classified in many ways • Healing takes a few months or more and occurs in a series of steps: 1. A fracture hematoma forms 2. A fibrocartilaginous (soft) callus forms 3. A bony (hard) callus forms 4. The bone is remodeled Types of Fractures "Types of Fractures" by OpenStax is licensed under CC BY 3.0 Stages in Fracture Repair "Stages of Fracture Repair" by OpenStax is licensed under CC BY 3.0 Clinical Anatomy: Achondroplasia • Abnormal endochondral ossification due to mutation. • Long bones of the limbs stop growing in childhood, whereas the other bones usually continues to grow normally (head is normal size) • Short-limbed dwarfism "Peter Dinklage" by Gage Skidmore is licensed under CC BY-SA 2.0 Clinical Anatomy: Acromegaly • Acromegaly is a rare condition where the body produces too much growth hormone in adulthood, usually due to a tumor of the pituitary gland. • This causes the flat bones of the body to grow. Over time, this leads to abnormally large head, hands and feet, and a wide range of other symptoms. • Acromegaly is usually diagnosed in adults aged 30 to 50, but it can affect people of any age. "Andre the Giant" by Ethan is licensed under CC BY-SA 2.0 Clinical Anatomy: Rickets • Condition of weak or soft bones in children. • The most common cause of rickets is a vitamin D deficiency. • Symptoms include bowed legs, stunted growth, bone pain, large forehead, and trouble sleeping. Complications may include bone fractures, muscle spasms, an abnormally curved spine, or intellectual disability. "Photograph; three children with rickets” by Wellcome Images is licensed under CC BY 4.0 Clinical Anatomy: Osteoporosis • Osteoporosis is a bone disease that occurs when the body loses too much bone, makes too little bone, or both. When the osteoclasts activity is higher than the osteoblasts activity, then bone tissue will be progressively lost. As a result, bones become weak and may break from a fall or, in serious cases, from sneezing or minor bumps. • When osteoporosis occurs, the holes and spaces between the trabeculae of spongy bone are much larger than in healthy bone. Osteoporotic bones have lost density or mass and contain abnormal tissue structure. As bones become less dense, they weaken and are more likely to break. Osteoporosis Image "Photograph; three children with rickets” by Wellcome Images is licensed under CC BY 4.0 Bone Markings - I • Surface features of bones vary considerably, depending on the function and location in the body. • Four general classes of bone markings 1. Articulating surfaces: these bone markings are smooth areas where a bone meets another bone to form a joint (articulation). There are different types of articulating surfaces: • Head: big rounded surface e.g. head of femur • Condyle: rounded surface e.g. occipital condyles of occipital bone • Trochlea: pully-like surface, with an indent in the middle e.g. trochlea of humerus • Facet: flat surface (not rounded) e.g. articular facets of vertebrae Bone Markings - II • Four general classes of bone markings (continued) 2. Elevations: these bone markings project outward from the bone. They usually mark the point where tendons and ligaments attach. They can be further classified as: • Process: prominence feature e.g. transverse process of vertebrae • Protuberance: protruding part out e.g. external occipital protuberance of occipital bone • Crest: a ridge e.g. iliac crest of os coxae • Line: slight, elongated ridge e.g. temporal lines of parietal bones • Spine: sharp process e.g. ischial spine • Ramus: curved part e.g. ramus of mandible • Tuberosity: rough surface e.g. deltoid tuberosity • Tubercle: small, rounded process e.g. tubercle of humerus • Trochanter: big, rounded process e.g. trochanter of femur • Epicondyle: rounded surface above a condyle e.g. epicondyle of femur Bone Markings - III • Four general classes of bone markings (continued) 3. Depressions: these bone markings form an indent into the bone, opposite as processes. They are usually where blood vessels and nerves pass. • Sulcus: groove e.g. intertubercular sulcus of humerus • Fossa: elongated basin e.g. mandibular fossa of mandible 4. Openings: these bone markings are holes in the bone. They are places for blood vessels and nerves to pass through or for air pockets within bones. • • • • • Canal: perfectly round and small opening e.g. optic canal Meatus: large opening e.g. external auditory meatus of temporal bone Sinus: air-filled space within a bone e.g. nasal sinus Fissure: slit through bone e.g. superior orbital fissure Foramen: common hole through a bone e.g. foramen magnum of occipital bone Examples of Bone Markings "Bone Markings" by OpenStax is licensed under CC BY 3.0