Skeletal System Part 1 PDF

Bones and Skeletal Tissues Part 1 BY: Dr. Pamela Paynter- Armour  OBJECTIVES Describe the Classification Bone Discuss the Functions of the Skeletal System Identify the four types of bones Identify the various Bone Cells ...

Bones and Skeletal Tissues Part 1 BY: Dr. Pamela Paynter- Armour  OBJECTIVES Describe the Classification Bone Discuss the Functions of the Skeletal System Identify the four types of bones Identify the various Bone Cells  3 INTRODUCTION  Human skeleton initially cartilages and fibrous membranes  Hyaline cartilage is the most abundant cartilage  By age 25 the skeleton is completely hardened growth ceases  206 bones make up the adult skeleton (20% of body mass)  80 bones of the axial skeleton  126 bones of the appendicular skeleton3  SKELETAL SYSTEM Interconnected system of bones, ligaments and tendons Provide support and protection for body Composed of 206 bones²  SKELETAL CARTILAGES Contain no blood vessels or nerves Dense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage ¹  SKELETAL CARTILAGES 1. Hyaline cartilages  Provide support, flexibility, and resilience  Most abundant type 2. Elastic cartilages  Similar to hyaline cartilages, but contain elastic fibers 3. Fibrocartilages  Epiglottis Thyroid Larynx Cartilage in Cartilages in cartilage external ear nose Cricoid Trachea Articular Lung cartilage Cartilage of a joint Cartilage in Costal Intervertebral cartilage disc Respiratory tube cartilages in neck and thorax Pubic Bones of skeleton symphysis Axial skeleton Meniscus (padlike cartilage in knee joint) Appendicular skeleton Cartilages Articular cartilage of a joint Hyaline cartilages Elastic cartilages Fibrocartilages Figure 6.1  GROWTH OF CARTILAGE Appositional Cells secrete matrix against the external face of existing cartilage Interstitial Chondrocytes divide and secrete new matrix, expanding cartilage from within Calcification of cartilage occurs during Normal bone growth Old age ¹  BONES OF THE SKELETON Two main groups, by location Axial skeleton (blue) Appendicular skeleton (pink)  DIVISIONS OF THE SKELETAL SYSTEM Skeletal system is divided into two main division Axial – central skeleton that protects and supports vital organs Appendicular – skeleton of the extremities²  AXIAL SKELETON Composed of skull and vertabrae Mainly flat and irregular bones Serve to protect organs such as brain, heart, and lungs Also helps to support body along central axis (backbone) ²  PARTS OF THE AXIAL SKELETON Skull – protects brain Vertebrae – protect spinal chord ;also serves to keep skeleton upright Ribs – protect lungs and heart ; gives intercostal muscles a hard surface to move against for breathing²  APPENDICULAR SKELETON So called because they are appendages of the axial skeleton. Comprises the bones of the shoulder girdle, the upper limbs, the pelvic girdle, and the lower limbs. Essential for mechanical load transfer.  CLASSIFICATION OF BONES BY SHAPE Long bones Longer than they are wide Short bones Cube-shaped bones (in wrist and ankle) Sesamoid bones (within tendons, e.g., patella) ¹  CLASSIFICATION OF BONES BY SHAPE Flat bones Thin, flat, slightly curved Irregular bones Complicated shapes  LONG BONES Found in the limbs and clavicle Each bone is made of a body (diaphysis) and two extremities (epiphyses) Wall consists of dense tissue Central canal called medullary canal is filled with marrow ²  SHORT BONES Found in skeleton where strength, compactness, and limited movement are desired 2 main examples Tarsus – 7 Bones Carpus – 8 bones  FLAT BONES Used in spots where protection or muscular attachment is desired Main locations are skull and scapula ² Also found in the ribs IRREGULAR BONES Bones which don’t fit into other categories due to irregular shapes Examples: vertebrae;sphenoid; hyoid ²  FUNCTIONS OF BONES Support For the body and soft organs Protection For brain, spinal cord, and vital organs Movement Levers for muscle action  FUNCTIONS OF BONES Storage Minerals (calcium and phosphorus) and growth factors Blood cell formation (hematopoiesis) in marrow cavities Triglyceride (energy) storage in bone cavities ¹  BONE MARKINGS Bulges, depressions, and holes serve as Sites of attachment for muscles, ligaments, and tendons Joint surfaces Conduits for blood vessels and nerves  BONE MARKINGS: PROJECTIONS Sites of muscle and ligament attachment Tuberosity—rounded projection Crest—narrow, prominent ridge Trochanter—large, blunt, irregular surface Line—narrow ridge of bone Tubercle—small rounded projection Epicondyle—raised area above a condyle Spine—sharp, slender projection Process—any bony prominence ¹  BONE MARKINGS: PROJECTIONS Projections that help to form joints Head Bony expansion carried on a narrow neck Facet Smooth, nearly flat articular surface Condyle Rounded articular projection Ramus Armlike bar Table 6.1  BONE MARKINGS: DEPRESSIONS AND OPENINGS Meatus Groove Canal-like passageway Furrow Sinus Fissure Cavity within a bone Narrow, slitlike opening Fossa Foramen Shallow, basinlike Round or oval opening depression through a bone ¹  BONE TEXTURES Compact bone Spongy (cancellous) Dense outer layer bone Honeycomb of trabeculae ¹  STRUCTURE OF A LONG BONE Diaphysis (shaft) Compact bone collar surrounds medullary (marrow) cavity Medullary cavity in adults contains fat (yellow marrow) ¹  STRUCTURE OF A LONG BONE Epiphyses Expanded ends Spongy bone interior Epiphyseal line (remnant of growth plate) Articular (hyaline) cartilage on joint surfaces  Articular cartilage Compact bone Proximal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined (b) by endosteum) Diaphysis Distal epiphysis (a)  MEMBRANES OF BONE Periosteum – double layer Outer fibrous layer Inner osteogenic layer Osteoblasts (bone-forming cells) Osteoclasts (bone-destroying cells) Osteogenic cells (stem cells) Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina Secured to underlying bone by Sharpey’s fibers ¹  MEMBRANES OF BONE Endosteum Delicate membrane on internal surfaces of bone Also contains osteogenic, osteoblasts and osteoclasts cells.¹  Endosteum Yellow bone marrow Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries  STRUCTURE OF SHORT, IRREGULAR, AND FLAT BONES Periosteum-covered compact bone on the outside Endosteum-covered spongy bone within Spongy bone called diploë in flat bones Bone marrow between the trabeculae ¹ Spongy bone (diploë) Compact bone Trabeculae  LOCATION OF HEMATOPOIETIC TISSUE (RED MARROW) Red marrow cavities of adults Trabecular cavities of the heads of the femur and humerus Trabecular cavities of the diploë of flat bones Red marrow of newborn infants Medullary cavities and all spaces in spongy bone ¹  MICROSCOPIC ANATOMY OF BONE Cells of bones Osteogenic (osteoprogenitor) cells Stem cells in periosteum and endosteum that give rise to osteoblasts Osteoblasts Bone-forming cells ¹ (a) Osteogenic cell (b) Osteoblast Stem cell Matrix-synthesizing cell responsible for bone growth  MICROSCOPIC ANATOMY OF BONE Cells of bone Osteocytes Mature bone cells Osteoclasts Cells that break down (resorb) bone matrix ¹ (c) Osteocyte (d) Osteoclast Mature bone cell Bone-resorbing cell that maintains the bone matrix  MICROSCOPIC ANATOMY OF BONE: COMPACT BONE Haversian system, or osteon—structural unit Lamellae Weight-bearing Column-like matrix tubes Central (Haversian) canal Contains blood vessels and nerves ¹  Artery with capillaries Structures in the Vein central Nerve fiber canal Lamellae Collagen fibers run in different directions Twisting force  MICROSCOPIC ANATOMY OF BONE: COMPACT BONE Perforating (Volkmann’s) canals At right angles to the central canal Connects blood vessels and nerves of the periosteum and central canal Lacunae—small cavities that contain osteocytes Canaliculi—hairlike canals that connect lacunae to each other and the central canal ¹  Compact Spongy bone bone Central Perforating (Haversian) canal (Volkmann’s) canal Endosteum lining bony canals Osteon and covering trabeculae (Haversian system) Circumferential lamellae (a) Perforating (Sharpey’s) fibers Lamellae Periosteal blood vessel Periosteum Nerve Vein Artery Lamellae Central Lacuna (with Canaliculi canal osteocyte) Osteocyte Lacunae in a lacuna (b) (c) Interstitial lamellae  MICROSCOPIC ANATOMY OF BONE: SPONGY BONE Trabeculae Align along lines of stress No osteons Contain irregularly arranged lamellae, osteocytes, and canaliculi Capillaries in endosteum supply nutrients  CHEMICAL COMPOSITION OF BONE: ORGANIC Osteogenic cells, osteoblasts, osteocytes, osteoclasts Osteoid—organic bone matrix secreted by osteoblasts Ground substance (proteoglycans, glycoproteins) Collagen fibers  CHEMICAL COMPOSITION OF BONE: INORGANIC Hydroxyapatites (mineral salts) 65% of bone by mass Mainly calcium phosphate crystals Responsible for hardness and resistance to compression ¹  FACTORS WHICH CONTRIBUTE TO BONE GROWTH Nutrition Exposure to sunlight Hormonal Secretion Physical Exercise ²  NUTRITION Mainly calcium consumption Increased blood calcium triggers release of calcitonin Causes uptake of calcium by osteoblasts (bone builders) ²  NUTRITION (CONTD) Decrease in calcium triggers release of Parathyroid hormone Triggers osteoclasts to break down bone, releasing calcium into blood²  EXPOSURE TO SUNLIGHT UV light on the skin causes Vitamin D production Promotes proper absorption of calcium in the SI²  HORMONAL SECRETION Human growth hormone Aka - Somatotropin Hormones stimulate activity in the epiphyseal plate ²  PHYSICAL ACTIVITY Increase in physical exertion on bone tissue actually increases bone density and strength ²  REFERENCES 1. Meeking J. Bones and Skeletal Tissues. [PowerPoint Slides]. 2010. 2. Laurens County School. Introduction to the Skeletal System. [PowerPoint Slides]. Available from: https://www.lcboe.net/userfiles/103/Classes/675/The%20Skeletal %20System%20(whole)2.ppt?id=443699 3. Shier, Butler & Lewis. Skeletal System. [PowerPoint Slides].