The Skeletal System Vertebral column Sacrum. Osseous tissue For the body and soft organs. Magnesium, sodium, fluoride Levers for muscle action

Transcription

1 10/1/2016 Cranium Facial s Skull Clavicle Scapula Sternum Rib Humerus Vertebra Radius Ulna Carpals Thoracic cage (ribs and sternum) The Skeletal System Vertebral column Sacrum Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (a) Anterior view Functions 1. Bone Support Osseous tissue For the body and soft organs 2. Protection 3. Movement Hydroxyapatite (85%) Calcium carbonate (10%) Inorganic minerals For brain, spinal cord and vital organs Magnesium, sodium, fluoride Levers for muscle action 4. Organic material Mineral reservoir Collagen Chondroitin sulfate Calcium and phosphorus 5. Hematopoiesis Marrow cavities Bone consists of multiple tissues Endosteum Articular A single may be considered an organ Proximal Yellow marrow Spongy line Medullary cavity (lined by endosteum) (b) Diaphysis Perforating (Sharpey s) fibers Bones are organs comprised of more than just osseous tissue Nutrient arteries Distal (a) (c) Figure 6.3c Figure 6.3a-b 1

2 10/1/2016 Bone Classification General Bone Features Long anatomy (Humerus) Diaphysis Epiphysis Metaphysis growth plate or line Articular Medullary cavity Endosteum Figure 6.2 Articular Proximal Endosteum Outer layer of periosteum = dense irregular fibrous sheath Spongy line Medullary cavity (lined by endosteum) Yellow marrow (b) Diaphysis Perforating (Sharpey s) fibers Nutrient arteries Anatomy of a long Distal (a) (c) Figure 6.3a-b Figure 6.3c A Closer Look Osteoblasts (OB) Osteoclasts (OC) (PO) Sharpey s Fibers (SF) Articular Proximal Metaphysis Spongy line Medullary cavity (lined by endosteum) (b) Diaphysis line is a remnant of the epiphyseal plate Distal (a) 2

3 (Growth) Plate Bone Histology Components Cells Fibers Ground substance Bone Histology Cells Osteogenic (osteoprogenitor) cells Stem cells in periosteum and endosteum osteoblasts Osteoblasts Bone forming cells (a) Osteogenic cell Stem cell (b) Osteoblast Matrix-synthesizing cell responsible for growth Figure 6.4a-b Bone Histology Cells Osteocytes Mature cells Maintain matrix Bone Histology Cells Osteoclasts Break down (resorb) matrix Related to macrophages 3

4 10/1/2016 (c) Osteocyte (d) Osteoclast Mature cell that maintains the matrix Bone-resorbing cell Figure 6.4c-d Bone Histology Primary types Compact Spongy Spongy (diploë) Compact covers all spongy and the shafts of long s Trabeculae Figure 6.5 Articular Proximal Spongy Compact Spongy line Medullary cavity (lined by endosteum) Central (Haversian) canal Perforating (Volkmann s) canal Endosteum lining bony canals and covering trabeculae Osteon (Haversian system) Circumferential lamellae (b) Diaphysis (a) Perforating (Sharpey s) fibers Lamellae Nerve Vein Artery Canaliculi Osteocyte in a lacuna (b) Distal (a) Figure 6.3a-b Periosteal blood vessel Lamellae Central canal Lacunae Lacuna (with osteocyte) (c) Interstitial lamellae Figure 6.7a-c 4

5 Structures in the central canal Artery with capillaries Vein Nerve fiber Collagen fibers run in different directions Lamellae Nerve Vein Artery Canaliculus Osteocyte in a lacuna Lamellae Central canal Lacunae Twisting force (b) Figure 6.6 Figure 6.3b Spongy (diploë) Compact Bone Histology Bone marrow Location Medullary cavity and spaces between trabeculae Trabeculae Figure 6.5 Bone Histology Bone marrow Types Red Red blood cells Hematopoiesis Yellow Replaces red with age Fat storage Gelatinous Mostly water, fat, and protein 1 - Proximal 2 - Distal 3 - line 4 - Articular 5 - Spongy Medullary canal Skeletal System 17 Label the following Turn in Endosteum 10 - Diaphysis 11 - Nutrient artery 12 -Marrow 13 -Perforating (Sharpey s) fibers 5

6 Bone Formation & Maintenance Ossification (osteogenesis) Stages Bone formation Begins in the 2nd month of development Postnatal growth Until early adulthood Bone remodeling and repair Lifelong Types of Ossification 1. Endochondral ossification Bone forms by replacing hyaline Forms most of the skeleton 2. Intramembranous ossification Bone develops from fibrous membrane Forms flat s Endochondral Ossification Uses hyaline models Requires breakdown of hyaline prior to ossification Week 9 Hyaline Bone collar Primary ossification center 1 Bone collar forms around hyaline model. Figure 6.9, step 1 Area of deteriorating matrix Month 3 Spongy formation Blood vessel of periosteal bud 2 Cartilage in the center of the diaphysis calcifies and then develops cavities. 3 The periosteal bud invades the internal cavities and spongy begins to form. Figure 6.9, step 2 Figure 6.9, step 3 6

7 blood vessel Birth Secondary ossification center Medullary cavity Childhood to adolescence Articular Spongy plate 4 The diaphysis elongates and a medullary cavity forms as ossification continues. Secondary ossification centers appear in the epiphyses in preparation for stage 5. Figure 6.9, step 4 5 The epiphyses ossify. When completed, hyaline remains only in the epiphyseal plates and articular s. Figure 6.9, step 5 Week 9 Month 3 Birth Childhood to adolescence Articular Secondary ossification Spongy center Area of blood vessel deteriorating matrix plate Hyaline Spongy Medullary cavity formation Bone Blood collar vessel of Primary periosteal ossification bud center 1 Bone collar 2 Cartilage in the 3 The periosteal 4 The diaphysis elongates 5 The epiphyses forms around center of the bud inavades the and a medullary cavity ossify. When hyaline diaphysis calcifies internal cavities forms as ossification completed, hyaline model. and then develops and spongy continues. Secondary remains only cavities. begins to form. ossification centers appear in the epiphyseal in the epiphyses in plates and articular preparation for stage 5. s. Figure 6.9 growth plates continue to produce cartilaginous elongation as long as s are increasing in length Calcified spicule Osteoblast depositing matrix Osseous tissue () covering spicules Resting zone 1 Proliferation zone Cartilage cells undergo mitosis. 2 Hypertrophic zone Older cells enlarge. 3 Calcification zone Matrix becomes calcified; cells die; matrix begins deteriorating. 4 Ossification zone New formation is occurring. Figure 6.10 Intramembranous Ossification Forms flat s Skull roof, lower jaw, clavicles Uses a fibrous membrane model formed from mesenchymal cells Mesenchymal cell Collagen fiber Ossification center Osteoid Osteoblast 1 Ossification centers appear in the fibrous connective tissue membrane. Selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center. Figure 6.8, (1 of 4) 7

8 Osteoblast Osteoid Osteocyte Newly calcified matrix 2 Bone matrix (osteoid) is secreted within the fibrous membrane and calcifies. Osteoblasts begin to secrete osteoid, which is calcified within a few days. Trapped osteoblasts become osteocytes. Figure 6.8, (2 of 4) Mesenchyme condensing to form the periosteum Trabeculae of woven Blood vessel 3 Woven and periosteum form. Accumulating osteoid is laid down between embryonic blood vessels in a random manner. The result is a network (instead of lamellae) of trabeculae called woven. Vascularized mesenchyme condenses on the external face of the woven and becomes the periosteum. Figure 6.8, (3 of 4) Fibrous periosteum Osteoblast Plate of compact Diploë (spongy ) cavities contain red marrow Bone Maintenance Bone is dynamic throughout human lifespan Remodeling has several functions Replacement and repair Release of calcium Response to stress (modification of density) 4 Lamellar replaces woven, just deep to the periosteum. Red marrow appears. Trabeculae just deep to the periosteum thicken, and are later replaced with mature lamellar, forming compact plates. Spongy (diploë), consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow. Figure 6.8, (4 of 4) Bone Remodeling Deposit Where is injured or added strength is required Osteoblasts Resorption Releases minerals from Osteoclasts Control of Remodeling Hormones Growth Hormone Calcitonin Parathyroid Hormone (PTH) Sex hormones 8

9 Hormonal Control of Blood Ca 2+ Blood Ca 2+ levels Parathyroid glands release PTH PTH stimulates osteoclasts to degrade matrix and release Ca 2+ Blood Ca 2+ levels Calcium homeostasis of blood: 9 11 mg/100 ml BALANCE BALANCE Stimulus Falling blood Ca 2+ levels Osteoclasts degrade matrix and release Ca 2+ into blood. Thyroid gland Parathyroid glands PTH Parathyroid glands release parathyroid hormone (PTH). Figure 6.12 Hormonal Control of Blood Ca 2+ Blood Ca 2+ levels Parafollicular cells of thyroid gland release calcitonin Osteoblasts deposit calcium salts Blood Ca 2+ levels Bone Maintenance Bone deposition Occurs where is injured or added strength is needed Development requires proper nutrition Vitamins C, D, and A Calcium and phosphorus Bone Disorders Poor nutrition Hormonal changes/imbalances Trauma Developmental errors Infection Tumors Nutritional Disorders Rickets 9

10 Nutritional Disorders Osteomalacia Hormonal Disorders Osteoporosis Loss of mass Bone resorption deposit Vertebral bodies and neck of femur Hormonal Disorders Osteoporosis Risk factors Lack of estrogen Low calcium or vitamin D Petite body form Immobility Low levels of TSH Diabetes mellitus Figure 6.16 Hormonal Disorders Osteoporosis Treatment and prevention Calcium, vitamin D, and fluoride supplements Weight bearing exercise throughout life Hormone (estrogen) replacement therapy Controversial because of increased cardiovascular disease, cancer Drugs to increase mineral density Fosamax, selective estrogen receptor modulators (SERMs), statins (don t work) Infections Osteomyelitis Inflammation of due to infection (Not normal) 10

11 Bone Fractures Incomplete Does not cross entire Complete Bone is broken into two pieces Comminuted Three or more pieces Displaced Bone ends don t line up Open versus closed Bone Fractures Transverse Spiral Impacted Depressed Greenstick Fractures Pathological Secondary to coexisting disease Osteoporosis Cancer Malnutrition Cushing s syndrome Osteogenesis imperfecta Fracture Repair Local periosteum and surrounding blood vessels are torn Inflammation Open vs. closed Swelling Hemorrhage (bleeding) Blood clots fracture hematoma Fracture Repair 1. Fracture hematoma forms within 6-8 hrs Torn blood vessels hemorrhage Clot (hematoma) forms Swollen, painful and inflamed Hematoma 1 A hematoma forms. Figure 6.15, step 1 11

12 Fracture Repair 2. Fibrocartilaginous callus forms Capillaries grow into area Osteoblasts begin forming spongy within 1 week Fibroblasts secrete collagen fibers to connect ends Internal callus (soft granulation tissue) 2 Fibrocartilaginous callus forms. External callus New blood vessels Spongy trabecula Figure 6.15, step 2 Fracture Repair 3. Bony callus formation New trabeculae form a bony (hard) callus Continues until firm union is formed in ~2 months Bony callus of spongy 3 Bony callus forms. Figure 6.15, step 3 Fracture Repair 4. Bone remodeling In response to mechanical stressors over several months Final structure resembles original Healed fracture 4 Bone remodeling occurs. Figure 6.15, step 4 12

13 Treatment of Fractures Hematoma Internal callus (fibrous tissue and ) External callus New blood vessels Spongy trabecula Bony callus of spongy Healed fracture 1 A hematoma forms. 2 Fibrocartilaginous 3 Bony callus forms. 4 Bone callus forms. remodeling occurs. Reduction Realignment Immobilization Traction Pathological fractures Address underlying problem Figure 6.15 Traction Uses gravity and/or tension Immobilizes Reduces pain Maintains length Does not realign facture Developmental Errors Skull Microcephalus Anterior fontanel closes early Developmental Errors Skull Hydrocephalus Excess CSF causes pressure Developmental Errors Skull Cleft palate 13

14 C 1 Cervical curvature (concave) 7 vertebrae, C 1 C 7 Scoliosis Disorders of the Spinal Column Spinous process Transverse processes Thoracic curvature (convex) 12 vertebrae, T 1 T 12 Intervertebral discs Intervertebral foramen Lumbar curvature (concave) 5 vertebrae, L 1 L 5 Sacral curvature (convex) 5 fused vertebrae sacrum Coccyx 4 fused vertebrae Anterior view Right lateral view Figure 7.16 Lordosis Kyphosis Spina Bifida Disorders of the Spinal Column Herniated disc Causes and risk factors Location Treatment Vertebral defect 14

15 Vertebral spinous process (posterior aspect of vertebra) Spinal nerve root Spinal cord Transverse process Herniated portion of disc Anulus fibrosus of disc (c) Superior view of a herniated intervertebral disc Nucleus pulposus of disc Figure 7.17c 15