Bone Tissue and Skeletal System PDF

LESSON 6: BONE TISSUE AND THE MARY FRANCES BAUDIN TOLEDO, RN, MAN SKELETAL SYSTEM Clinical Instructor FUNCTIONS OF THE SKELETAL SYSTEM The skeletal system is made of bone and cartilage Functions include: Providing rigid support framework of t...

LESSON 6: BONE TISSUE AND THE MARY FRANCES BAUDIN TOLEDO, RN, MAN SKELETAL SYSTEM Clinical Instructor FUNCTIONS OF THE SKELETAL SYSTEM The skeletal system is made of bone and cartilage Functions include: Providing rigid support framework of the human body Allowing movement as muscles pull on bones Providing protection for soft internal organs Storing minerals in the bone extracellular matrix Storing energy in the form of adipose in yellow bone marrow Production of blood cells BONE FUNCTIONS Attachment sites for muscles Protection of internal organs Storage of calcium and other minerals Production of blood cells Storage of adipose tissue CARTILAGE Cartilage contributes to skeletal system Elastic cartilage is not found in the skeletal system Hyaline cartilage is found at the ends of bones where they form joints Helps bones glide past one another Loss of hyaline cartilage leads to osteoarthritis Fibrocartilage is found between vertebrae, within the knee, and the pubic symphysis ANATOMY OF A TYPICAL BONE Periosteum covers the surface of the bone Outer shell of compact bone protects entire bone Spongy bone contains red bone marrow Medullary cavity contains yellow bone marrow Articular cartilage made of hyaline cartilage is found at the joints Ligaments attach bones to each other BONE CLASSIFICATION CLASSES OF BONES Bones are classified primarily according to shape Long bones Short bones Flat bones Irregular bones Sesamoid bones LONG BONES Bones that are longer than they are wide Function as levers Examples: Humerus Femur Ulna Tibia COMMON STRUCTURES OF A LONG BONE Epiphysis—end of long bone Diaphysis—shaft of long bone Metaphysis—between epiphysis and diaphysis Location of epiphyseal plate/line Medullary cavity—hollow space in diaphysis Houses yellow bone marrow Articular cartilage—layer of hyaline cartilage that reduces friction in joint COMMON STRUCTURES OF A LONG BONE Periosteum—dense irregular connective tissue lining surface Contains blood vessels, nerves, and lymphatic vessels Tendons and ligaments attach to periosteum by perforating fibers Endosteum—dense irregular connective tissue lining medullary cavity Periosteum and endosteum contain cells that allow bone growth PERIOSTEUM Periosteum is attachment site for tendons and ligaments Collagen fibers of tendon weave into those of periosteum to anchor muscle to bone ARTICULAR CARTILAGE Found at ends of long bones where joints form Made of hyaline cartilage Reduce friction and act as shock absorber SHORT AND FLAT BONES Short bones Flat bones Cube-like in shape Usually thin, but can be curved Approximately equal length, Protect internal organs width, and thickness Provide stability and support Examples: Cranial bones (skull) Examples: Sternum Carpal bones of the wrist Ribs Tarsal bones of the ankle Scapula FLAT BONES Composed of a layer of spongy bone between two layers of compact bone Help protect internal organs (e.g., skull, ribs) Spongy bone houses red bone marrow  IRREGULAR AND SESAMOID BONES Irregular bones Sesamoid bones Do not have an easily Small, round bones suspended characterized shape in a tendon or ligament Does not fit any other Protect tendons from classification compressive force Complex shapes Example: Examples: Patella Vertebrae Only common sesamoid bone Facial bones SESAMOID BONES Small, round bones suspended within a tendon or ligament Develop over time due to friction Help protect tendons Typically seen in tendons of feet, hands, and knees Patella is the only common sesamoid bone in every person BONE MARKINGS The surface features of bones Articulating surfaces – where two bones meet Depressions—sunken portion of a bone Projections—projects above surface of bone Holes and spaces—an opening or a groove in the bone ARTICULATING SURFACES Articulating surfaces Condyle—rounded surface Facet—flat surface Head—prominent rounded surface Trochlea—rounded articulating surface DEPRESSIONS Depressions Fossa—elongated basin Sulcus—groove  PROJECTIONS Crest—ridge Epicondyle—projection off a condyle Line—slight, elongated ridge Process—prominent feature Ramus —long projection (branch) PROJECTIONS Spine—sharp process Trochanter—rough round projection Tubercle—small, rounded process Tuberosity—rough surface HOLES AND SPACES Canal—passage in bone Fissure—slit through bone Foramen—hole through bone Meatus—opening into canal Sinus—air-filled space in bone  THE MICROSCOPIC STRUCTURE OF CARTILAGE AND BONE THREE TYPES OF CARTILAGE Hyaline, elastic, and fibrocartilage Chondroblasts – cells of cartilage that secrete matrix Chondrocytes – cells that are completely surrounded by matrix Found in lacunae CARTILAGE TISSUE Semi-solid connective tissue Avascular Covered by perichondrium Dense irregular connective tissue Contains blood vessels Provides nutrients to cartilage BONE TISSUE Solid connective tissue Compact bone More dense Provides support and protection Spongy bone Provide strength to bone Spaces house red bone marrow COMPACT BONE Osteon—structural unit of compact bone Made of rings of matrix called concentric lamellae Concentric lamellae surround central canal and provide support Blood vessels in central canal connected to periosteum by perforating canals Nutrients and wastes move through canaliculi SPONGY BONE Contain osteocytes within trabeculae Trabeculae—beams of bone that form lattice-like network within spongy bone Form along stress lines to provide strength Spaces house red bone marrow where hematopoiesis occurs CELLS OF BONE Osteogenic cells—stem cells that replicate Develop into osteoblasts Communicate via canaliculi Osteoblasts—cells that form new bone matrix Osteocytes—mature osteoblast that are completely surrounded by matrix Located in lacunae Osteoclasts—cells that breakdown bone Aid in bone remodeling FORMATION AND GROWTH OF BONE AND CARTILAGE FORMATION OF BONE Ossification—the process of forming bone A cartilage or membranous model is required New bone tissue is built on the model Intramembranous ossification—connective tissue membrane is used to make bone Endochondral ossification—hyaline cartilage is used to make bone INTRAMEMBRANOUS OSSIFICATION Forms flat bones of cranium and face Mesenchymal cells group together and differentiate into osteoblasts forming ossification center Osteoblasts begin to secret osteoid Trabeculae and periosteum form Compact bone surrounds trabecular bone  ENDOCHONDRAL OSSIFICATION Forms most long bones Cells in cartilage differentiate into osteoblasts Minerals are deposited on collagen fibers in cartilage starting at diaphysis Perichondrium becomes periosteum Blood vessels penetrate periosteum forming primary ossification center Mineralization increases Cartilage remains at epiphyseal plate to allow bone to grow in length Epiphyses ossify after birth at secondary ossification centers OSSIFICATION OF EMBRYONIC AND FETAL SKELETONS Embryonic and fetal skeletons form by combination of intramembranous and endochondral ossification Long bones are formed via endochondral ossification Flat bones are formed via intramembranous ossification Mineralization increases during development GROWTH, REPAIR, AND REMODELING CARTILAGE GROWTH Interstitial cartilage growth—cartilage grows longer Due to mitotic replication of chondrocytes Allows bone to increase in length Appositional cartilage growth—cartilage grows wider Occurs as cells in perichondrium become chondroblasts and secrete matrix Allows bone to increase in width INTERSTITIAL CARTILAGE GROWTH Chondrocytes divide by mitosis which allows cartilage to grow in length Initially share same lacuna Chondrocytes move apart as they secrete matrix HOW BONES GROW IN LENGTH Epiphyseal plate grows The increase in size increases the distance between the epiphysis and diaphysis Cartilage on the diaphysis side of the plate is replaced with bone Bone is longer as a result ANATOMY OF EPIPHYSEAL PLATE Epiphyseal plates exhibit four zones of activity Reserve zone – anchors epiphyseal plate to epiphysis Proliferative zone – chondrocytes that recently underwent mitosis Zone of mature cartilage – older, more mature chondrocytes Zone of calcified matrix – dead chondrocytes surrounded by bone matrix Anchors epiphyseal plate to diaphysis APPOSITIONAL CARTILAGE GROWTH Allows cartilage to increase in width Cell in perichondrium differentiate into chondroblasts Chondroblasts secrete matrix allowing increase in width HOW BONES GROW IN DIAMETER Occurs by appositional growth Osteoblasts in periosteum form new matrix on surface of bone Osteoclasts break down older bone that lines medullary cavity BONE REMODELING The changes bones go through on a daily basis Bone is constantly broken down and new bone is formed Aids homeostasis by making minerals available Caused by injury, exercise, and other activities Bone remodels to increase strength along line of resistance BLOOD CALCIUM REGULATION Bones store calcium and other minerals Hormones influence bone: Calcitonin causes bones to take up calcium Lowers blood calcium levels Parathyroid hormone causes bones to release calcium Increases blood calcium levels HORMONES THAT INFLUENCE THE SKELETAL SYSTEM Growth hormone (GH) – promotes bone growth T3 and T4 – promotes bone growth Estrogen and testosterone – increase osteoblast activity Calcitriol – increases absorption of calcium and phosphate from intestine PTH – increases osteoclast activity Calcitonin – increases osteoblast and decreases osteoclast activity BONE REPAIR Fracture—break of a bone Steps in bone repair: 1. Hematoma prevents blood loss 2. Cartilage callus forms new bone template 3. Callus is replaced by bone 4. Compact bone is built around the outer surface of bone ASSISTING BONE REPAIR Reduction = aligning of bones for optimal healing Should be done as soon as possible Cylinders and screws can be added surgically for stabilization Can you identify reasons for a physician to splint a bone when it’s fractured? TYPES OF FRACTURES Fractures classified based on complexity, location, and other features Closed Open Transverse Spiral Comminuted Impacted Greenstick Oblique BONES AND HOMEOSTASIS NUTRITION AND BONE TISSUE Calcium is stored in the extracellular matrix of bone Hypocalcemia – low blood levels of calcium Hypercalcemia – high blood levels of calcium Parathyroid hormone (PTH) – stimulates osteoclasts The breakdown of bone increases blood calcium Calcitonin (CT) – inhibits osteoclasts Increased formation of bone decreases blood calcium CALCIUM HOMEOSTASIS Bones store calcium Calcitonin and parathyroid hormones aid in calcium homeostasis Calcium is absorbed by small intestine Requires vitamin D for absorption DIETARY CALCIUM Good sources of dietary calcium include: Cheese Milk Nuts Leafy greens Fish IMPORTANCE OF VITAMIN D Vitamin D is synthesized by the body Not found in many foods Can be added to foods like milk and cereal for supplementation VITAMIN D SYNTHESIS Human body can produce vitamin D Requires exposure to sunlight/UV radiation Activated by kidneys Active forms = calcitriol and calcidiol Travels through blood to small intestine Facilitates calcium absorption by small intestine EXERCISE AND BONE TISSUE Exercise and physical stress strengthen bones Increased exercise leads to thicker, denser bones Lack of exercise leads to weaker, lighter bones Increases risk of fracture OSTEOPOROSIS Characterized by a decrease in bone mass with age Rate of bone resorption exceeds rate of bone formation Osteoclasts more active than osteoblasts Rapidly declining levels of estradiol in females increases risk THANK YOU