Chapter 6 Bones and Bone Tissue - Human Anatomy & Physiology PDF

Human Anatomy & Physiology Second Edition Chapter 06 Bones and Bone Tissue Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Module 6.1 Introduction to Bones as Orga...

Human Anatomy & Physiology Second Edition Chapter 06 Bones and Bone Tissue Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Module 6.1 Introduction to Bones as Organs Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Learning Outcomes 1.Describe the functions of the skeletal system. 2.Describe how bones are classified by shape. 3.Describe the gross structure of long, short, flat, irregular, and sesamoid bones. 4.Explain the differences between red and yellow bone marrow. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Skeletal System Skeletal system includes: – Bones, joints, and associated supporting tissues – Bones – main organs of system: ▪ Like any organ, composed of more than osseous tissue ▪ Also dense regular, irregular collagenous connective tissue and bone marrow Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Functions of the Skeletal System Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Structure Bone structure can be organized into 5 classes despite diversity of bone appearance; all 206 bones fit into categories based on shape: – Long bones – longer than they are wide; include most bones in arms and legs – Short bones –roughly cube-shaped or about as long as they are wide; include bones of wrist or carpals and ankle or tarsals – Flat bones – thin and broad bones; include ribs, pelvis, sternum (breastbone), and most skull bones – Irregular bones – include vertebrae and certain skull bones; do not fit into other classes because of irregular shapes – Sesamoid bones – specialized bones located within tendons; usually small, flat, and oval-shaped; give tendons mechanical advantage; give muscles better leverage; patella (kneecap) is example Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Structure Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Bone Structure Structure of a long bone: – Periosteum – membrane composed of dense irregular collagenous connective tissue; rich with blood vessels and nerves; surrounds outer surface of long bones – Perforating fibers (Sharpey’s fibers) – made of collagen; anchors periosteum firmly to underlying bone surface by penetrating deep into bone matrix – Diaphysis – shaft of long bone; each end is epiphysis; covered with thin layer of hyaline cartilage (articular cartilage) found within joints (articulations) between bones – Medullary cavity (marrow cavity) within diaphysis contains either red or yellow bone marrow, depending on bone and age of individual Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Structure – Compact bone – one of two bone textures; hard, dense outer region; allows bone to resist linear compression and twisting forces among other stresses – Spongy bone (cancellous bone) – second bone texture; inside cortical bone; honeycomb-like framework of bony struts; allows long bones to resist forces from many directions; provides cavity for bone marrow – Endosteum- Bony struts of spongy bone and all inner surfaces Figure 6.9 Structure of of bone are covered by thin membrane; contain different compact bone. populations of bone cells involved in maintenance of bone homeostasis – Epiphyseal lines – separate both proximal and distal epiphyses from diaphysis; remnant of epiphyseal plates (growth plates); line of hyaline cartilage found in developing bones of children Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Structure Structure of short, flat, irregular, and sesamoid bones: do not have diaphyses, epiphyses, medullary cavities, epiphyseal lines, or epiphyseal plates Covered by periosteum, with associated perforating fibers, blood vessels, and nerves – Two outer layers of thin compact bone with middle layer of spongy bone (diploë) and associated bone marrow – Sinuses: some flat and irregular bones of skull contain hollow, air-filled spaces, which reduce bone weight Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Supply Blood and nerve supply to bone – bones are well supplied with blood vessels and sensory nerve fibers: – Blood supply to short, flat, irregular, and sesamoid bones is provided mostly by vessels in periosteum that penetrate bone – Long bones get third of their blood supply from periosteum; mostly supplies compact bone – Remaining two-thirds supplied by one or two nutrient arteries; enter bone through small hole in diaphysis (nutrient foramen) – Epiphyses receive some blood supply from nutrient arteries; majority comes from small blood vessels that enter and exit through small holes in compact bone Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Marrow Red bone marrow – loose connective tissue; supports islands of blood-forming hematopoietic cells – Amount of red marrow decreases with age – Red marrow in adult is only in pelvis, proximal femur and humerus, vertebrae, ribs, sternum, clavicles, scapulae, and some bones of skull – Children need more red marrow to assist in growth and development Yellow bone marrow –triglycerides, blood vessels, and adipocytes Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Marrow Transplantation Blood diseases (leukemia, sickle-cell anemia, aplastic anemia) have improperly functioning hematopoietic cells; benefit from bone marrow transplantation Needle inserted into pelvic bone of matching donor and red marrow withdrawn; repeated until up to 2 quarts (about 2% of total) is removed Recipient’s marrow is destroyed; donor marrow given intravenously; cells travel to recipient’s marrow cavities; produce new blood cells in 2–4 weeks if successful Complications – flu-like symptoms (first 2–4 weeks), infection, or transplant rejection Many recipients can return to healthy life if transplant “takes” Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Module 6.2 Microscopic Structure of Bone Tissue Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Learning Outcomes 1. Describe the inorganic and organic components of the extracellular matrix of bone tissue. 2. Explain the functions of the 3 main cell types in bone tissues 3. Describe the microscopic structure of compact bone and components of the osteon. 4. Describe the microscopic structure of spongy bone. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone/ Osseous Tissue Osseous tissue – primary tissue found in bone; composed mostly of extracellular matrix with a small population of cells scattered throughout Extracellular matrix of bone is unique: – Inorganic matrix – minerals make up about 65% of bone’s total weight – Organic matrix – makes up remaining 35%; consists of collagen fibers and usual ECM components Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Extracellular Matrix Inorganic matrix – predominantly calcium salts; bone stores around 85% of total calcium ions as well as large amount of phosphorus: – Calcium and phosphorus salts exist as large molecules of hydroxyapatite crystal [Ca10 (PO4 )6 (OH)2 ] – Crystalline structure makes bone one of hardest substances in body; strong and resistant to compression – Allows bone to be both protective and supportive. – Bicarbonate, potassium, magnesium, and sodium are also in inorganic matrix Organic matrix – known as osteoid Collagen – predominant protein fiber; forms cross-links with one another; helps bone resist torsion (twisting) and tensile (pulling or stretching) forces Collagen fibers align themselves with hydroxyapatite crystals; enhances hardness of bone Glycosaminoglycans and proteoglycans create an osmotic gradient; draw water into osteoid; help tissue resist compression Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Extracellular Matrix Figure 6.5 The importance of bone matrices. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Cells Bone is a dynamic tissue; continually changing as older bone is broken down for raw materials to build new bone; Three types of bone cells are responsible for bone’s dynamic nature – Osteoblasts – Osteocytes – Osteoclasts Figure 6.6 Types of bone cells. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Bone Cells Osteocytes Osteoblasts eventually surround Osteoclasts Osteoblasts – metabolically active in - Responsible for bone resorption; themselves with matrix in small periosteum and endosteum: cell secretes hydrogen ions and cavities (lacunae); become osteocytes that no longer actively enzymes; break down bone matrix - Bone-building cells; perform bone - Large multinucleated cells; deposition, form matrix synthesize bone matrix resemble jellyfish; derived from – Osteogenic cells – flattened cells; – No longer metabolically active fusion of cells from bone differentiate into osteoblasts when except for maintaining bone marrow – stimulated by specific chemical extracellular matrix - Eventually located in shallow signals – Appear to have ability to recruit depressions on internal and – Bone deposition – osteoblasts osteoblasts to build up or external surfaces of bone secrete organic matrix materials; reinforce bone under tension assist in formation of inorganic Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Cells Osteoclasts Hydrogen ions dissolve components of inorganic matrix; enzymes break down organic matrix – Liberated substances from breakdown of bone absorbed by various transport methods into osteoclast cytosol – Substances can be released into blood; might be reused or excreted from body as waste products Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Structure of compact bone: Built to withstand lots of stress Osteon (Haversian system) - Structural unit – Made of rings (4 to 20) of thin layers of bone called lamellae ▪Greatly enhance compact bone’s strength – Central canal: blood vessels & nerves supply osteon – Lacunae with osteocytes: for bone maintenance – Canaliculi: canals that connect lacunae to help with sharing resources (oxygen, nutrients) & communicate ▪cytoplasmic extensions of osteocytes extend through networks Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Figure 6.9 Structure of compact bone.  Osteons are not permanent structures: regularly resorbed and rebuilt Interstitial lamellae – Lamellae outside of the osteon – Remnants of resorbed osteons – Fill gaps between forming osteons Circumferential lamellae – Extend around the entire circumference of the diaphysis – Just deep to the periosteum – Resist twisting of the entire bone Perforating canals (Volkmann’s canals) – originate from blood vessels in periosteum – travel at right angles (perpendicular) to central canals of neighboring osteons; – connect them to one another Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Structure of spongy bone Usually not weight-bearing like compact bone Much less densely packed Network of struts reinforces compact bone – resists forces from variety of directions Protects bone marrow tissue Composed of Trabeculae – struts of bone; covered with endosteum ▪Usually not arranged into osteons ▪Composed of concentric lamellae with osteocytes in lacunae ▪communicate through canaliculi No central or perforating canals supplying blood to trabeculae; obtain blood from vessels in bone marrow Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Figure 6.10 Structure of spongy bone. Module 6.3 Bone Formation: Ossification Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Learning Outcomes 1. Explain the differences between primary and secondary bone 2. Describe the process of intramembranous ossification 3. Describe the process of endochondral ossification Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Ossification (or osteogenesis): Process of bone formation Begins in the embryonic period Continues through childhood with most bones completing process by age 7. Two different mechanisms for ossification: ▪First bone formed is immature primary (woven) bone –Irregularly arranged collagen bundles, osteocytes, and sparse inorganic matrix –Eventually, broken down by osteoclasts ▪Mature secondary bone –more inorganic matrix and increased strength Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Types of Ossification Intramembranous ossification are built on model (starting material) made of membrane of embryonic connective tissue – Forms many flat bones skull and clavicles during fetal development – Forms primary bone (which will become secondary bone) Endochondral ossification are built on model of hyaline cartilage – Most bones (except skull and clavicles) – Hyaline cartilage model – chondrocytes, collagen, and ECM all surrounded by connective tissue membrane (perichondrium) and immature cartilage cells (chondroblasts) – Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Intramembranous Ossification Embryonic skull Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Endochondral Ossification Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Endochondral Ossification Figure 6.12 The process of endochondral ossification. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Endochondral Ossification Cartilage only remains in epiphyseal plates and on articular surfaces where bones interact at joint (articular cartilage) Articular cartilage persists into adulthood; – epiphyseal plates are eventually replaced with bone, once growth in length ceases Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Osteoporosis and Healthy Bones Most common bone disease in United States Bones become weak and brittle due to inadequate inorganic matrix Increases risk of fractures with decreased rate of healing Causes – dietary (calcium and/or vitamin D deficiency), female gender, advanced age, lack of exercise, hormonal (lack of estrogen in postmenopausal women), genetic factors, and other diseases Prevention – balanced diet, with supplementation as needed, weight-bearing exercise, and estrogen replacement if appropriate Treatment – drugs that inhibit osteoclasts or stimulate osteoblasts Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Module 6.4 Bone Growth in Length and Width Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Learning Outcomes 1. Describe how long bones grow in length 2. Compare longitudinal and appositional bone growth 3. Describe the hormones that play a role in bone growth Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Long Bones length by longitudinal growth Involves division of chondrocytes (not Diaphysis=shaft osteocytes or osteoblasts) in epiphyseal plate Bone growth takes place at epiphysis on side closest to diaphysis Epiphyseal plate – composed of hyaline cartilage that did not ossify – 5 different zones of cells Figure 6.14 Growth at the epiphyseal plate. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Structure of the epiphyseal plate: 5 zones 1. Zone of ossification – calcified chondrocytes and osteoblasts 2. Zone of calcification – dead chondrocytes; some calcified 3. Zone of hypertrophy and maturation – mature chondrocytes 4. Zone of proliferation – actively dividing chondrocytes in lacunae 5. Zone of reserve cartilage –cells that are not directly involved in bone growth but can be recruited for cell division if needed Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Growth at the epiphyseal plate Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Figure 6.14 Growth at the epiphyseal plate. Appositional Growth-bone widening  Appositional growth involves osteoblasts between the periosteum and bone surface laying down new bone  First forms circumferential lamellae  Eventually deeper circumferential lamellae are removed or incorporated into osteons Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Role of Hormones in Bone Growth Growth hormone – secreted by anterior pituitary gland; enhances protein synthesis and cell division in nearly all tissues, including bone Testosterone has pronounced effect on bone growth: – Increases appositional growth; bones in males become thicker with more calcium salt deposition than females – Increases rate of mitosis in epiphyseal plate; leads to “growth spurts” in teenage years – Accelerates closure of epiphyseal plate Estrogen also plays a role in bone growth: – Increases rate of longitudinal bone growth; inhibits osteoclast activity – When estrogen levels spike in teen years an accompanying “growth spurt” occurs in females – Accelerates closure of epiphyseal plate at much faster rate than testosterone; leads to average height differences between genders Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Module 6.5 Bone Remodeling and Repair Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved  Learning Outcomes 1. Describe the processes of bone resorption and bone deposition 2. Describe the physical, hormonal, and dietary factors that influence bone remodeling 3. Explain the role of calcitonin, parathyroid hormone, and vitamin D in bone remodeling and calcium ion homeostasis 4. Describe the general process of bone repair Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Remodeling Continuous process of bone formation and loss after growth in length is finished This cycle occurs for: – Maintenance of calcium ion homeostasis – Replacement of primary bone with secondary bone – Bone repair New bone Old bone deposition resorption – Replacement of old brittle bone with newer bone – Adaptation to tension and stress breakdown by osteoclasts = bone formation by osteoblasts Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Remodeling: Bone deposition by osteoblasts Found in both periosteum and endosteum Make organic matrix and facilitate formation of inorganic matrix Secrete proteoglycans and glycoproteins that bind to calcium ions Secrete vesicles containing calcium ions, ATP, and enzymes – bind to collagen fibers – calcium ions eventually crystallize, rupturing vesicle and beginning calcification process Figure 6.7 Functions of osteoblasts and osteocytes. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Remodeling: Resorption by Osteoclasts Osteoclasts secrete hydrogen ions on bone ECM – Hydroxyapatite crystals in inorganic matrix are pH-sensitive and break down – Calcium ions and other liberated minerals can be reused elsewhere in body Osteoclasts secrete enzymes – Degrade organic matrix (proteoglycans, glycosaminoglycans, and glycoproteins) – Then, they reused by osteoclasts Figure 6.8b Functions of osteoclasts. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Factors influencing bone remodeling bone formation by osteoblasts = breakdown by osteoclasts Figure 6.16 Factors that influence bone remodeling. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone remodeling and calcium ion homeostasis Calcium ions mostly stored in bones Calcium ions are used for: – bone deposition and remodeling – muscle contraction – Transmission of nerve impulses Parathyroid hormone – Blood clotting Figure 6.15 Maintaining homeostasis: response to low blood calcium ion level by a negative feedback loop. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone remodeling and calcium ion homeostasis Increased Blood calcium levels Decrease in Decrease in blood calcium PTH secretion levels Decrease in Increase in Osteoclast Calcitonin by activity = more thyroid gland bone deposition Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Bone Repair: Fractures Simple fractures – skin and tissue around fracture remain intact Compound fractures – skin and tissues around fracture are damaged Table 6.1 Types of Fractures Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Process of Fracture Repair Fibroblasts-secrete collagen fibers forming dense irregular collagenous CT Osteogenic cells from endosteum become chondroblasts that secrete hyaline cartilage (primary bone) Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Figure 6.17 The process of fracture repair.