Human Anatomy and Physiology Eleventh Edition - Chapter 6 - Bones and Skeletal Tissues LECTURESLIDES PDF

Human Anatomy and Physiology Eleventh Edition Chapter 06 Part A Bones and Skeletal Tissues PowerPoint® Lectures Slides...

Human Anatomy and Physiology Eleventh Edition Chapter 06 Part A Bones and Skeletal Tissues PowerPoint® Lectures Slides prepared by Karen Dunbar Kareiva, Ivy Tech Community College Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.1 Skeletal Cartilages The human skeleton initially consists of just cartilage, which is replaced by bone, except in areas requiring flexibility Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Basic Structure, Types, and Locations Skeletal cartilage: made of highly resilient, molded cartilage tissue that consists primarily of water – Contains no blood vessels or nerves Perichondrium: layer of dense connective tissue surrounding cartilage like a girdle – Helps cartilage resist outward expansion – Contains blood vessels for nutrient delivery to cartilage Cartilage is made up of chondrocytes, cells encased in small cavities (lacunae) within jelly-like extracellular matrix Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Basic Structure, Types, and Locations Three types of cartilage: – Hyaline cartilage  Provides support, flexibility, and resilience  Most abundant type; matrix contains collagen fibers only  Articular (joints), costal (ribs), respiratory (larynx), nasal cartilage (nose tip) – Elastic cartilage  Similar to hyaline cartilage, but contains elastic fibers  Only two locations - external ear and epiglottis (flap that covers larynx) – Fibrocartilage  Thick collagen fibers: has great tensile strength  Menisci of knee; vertebral discs Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved The Bones and Cartilages of the Human Skeleton Epiglottis Thyroid Larynx Cartilage in cartilage Cartilages in Cricoid external ear nose cartilage Trachea Lung Articular cartilage of a joint Costal Cartilage in cartilage Intervertebral disc Respiratory tube cartilages in neck and thorax Bones of skeleton Axial skeleton Pubic symphysis Appendicular skeleton Meniscus (padlike Cartilages cartilage in Hyaline cartilages knee joint) Elastic cartilages Articular cartilage Fibrocartilages of a joint Figure 6.1 The bones and cartilages of the human skeleton. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth of Cartilage Cartilage grows in two ways: – Appositional growth  Cartilage-forming cells in perichondrium secrete matrix against external face of existing cartilage – New matrix laid down on surface of cartilage – Interstitial growth  Chondrocytes within lacunae divide and secrete new matrix, expanding cartilage from within – New matrix made within cartilage Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.2 Functions of Bones There are seven important functions of bones: 1. Support  For body and soft organs 2. Protection  Protect brain, spinal cord, and vital organs 3. Movement/Anchorage  Levers for muscle action 4. Mineral and growth factor storage  Calcium and phosphorus, and growth factors reservoir Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.2 Functions of Bones 5. Blood cell formation  Hematopoiesis occurs in red marrow cavities of certain bones 6. Triglyceride (fat) storage  Fat, used for an energy source, is stored in bone cavities 7. Hormone production  Osteocalcin secreted by bones helps to regulate insulin secretion, glucose levels, and metabolism Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.3 Classification of Bones 206 named bones in human skeleton Divided into two groups based on location – Axial skeleton  Long axis of body  Skull, vertebral column, rib cage – Appendicular skeleton  Bones of upper and lower limbs  Girdles (shoulder and hip bones) attaching limbs to axial skeleton Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved The Bones and Cartilages of the Human Skeleton Epiglottis Thyroid Larynx Cartilage in cartilage Cartilages in Cricoid external ear nose cartilage Trachea Lung Articular cartilage of a joint Costal Cartilage in cartilage Intervertebral disc Respiratory tube cartilages in neck and thorax Bones of skeleton Axial skeleton Pubic symphysis Appendicular skeleton Meniscus (padlike Cartilages cartilage in Hyaline cartilages knee joint) Elastic cartilages Articular cartilage Fibrocartilages of a joint Figure 6.1 The bones and cartilages of the human skeleton. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.3 Classification of Bones Bones are also classified according to one of four shapes: 1. Long bones  Longer than they are wide  Limb bones 2. Short bones  Cube-shaped bones (in wrist and ankle)  Sesamoid bones form within tendons (example: patella)  Vary in size and number in different individuals Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.3 Classification of Bones 3. Flat bones  Thin, flat, slightly curved  Sternum, scapulae, ribs, most skull bones 4. Irregular bones  Complicated shapes  Vertebrae and hip bones Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Classification of Bones on the Basis of Shape (c) Flat bone (sternum) (a) Long bone (humerus) (b) Irregular bone (vertebra), (d) Short bone (talus) right lateral view Figure 6.2 Classification of bones on the basis of shape. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.4 Bone Structure Bones are organs because they contain different types of tissues  Bone (osseous) tissue predominates, but a bone also has nervous tissue, cartilage, fibrous connective tissue, muscle cells, and epithelial cells in its blood vessels Three levels of structure – Gross – Microscopic – Chemical Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Gross Anatomy Compact and spongy bone – Compact bone: dense outer layer on every bone that appears smooth and solid – Spongy bone: made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae  Open spaces between trabeculae are filled with red or yellow bone marrow Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Compact and Spongy Bone Spongy bone has a mesh of bony spines called trabeculae. Compact bone looks smooth and solid. Figure 6.3 Compact and spongy bone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Gross Anatomy Structure of short, irregular, and flat bones – Consist of thin plates of spongy bone (diploe) covered by compact bone – Compact bone sandwiched between connective tissue membranes  Periosteum covers outside of compact bone, and endosteum covers inside portion of compact bone – Bone marrow is scattered throughout spongy bone; no defined marrow cavity – Hyaline cartilage covers area of bone that is part of a movable joint Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Flat Bones Consist of a Layer of Spongy Bone Sandwiched between Two Thin Layers of Compact Bone (1 of 2) Spongy bone (diploë) Compact bone Trabeculae of spongy bone Figure 6.4 Structure of a flat bone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Gross Anatomy Structure of typical long bone – All long bones have a shaft (diaphysis), bone ends (epiphyses), and membranes  Diaphysis: tubular shaft that forms long axis of bone – Consists of compact bone surrounding central medullary cavity that is filled with yellow marrow in adults  Epiphyses: ends of long bones that consist of compact bone externally and spongy bone internally – Articular cartilage covers articular (joint) surfaces  Between diaphysis and epiphysis is epiphyseal line – Remnant of childhood epiphyseal plate where bone growth occurs Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved The Structure of a Long Bone (Humerus of Arm) Articular cartilage Proximal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) Diaphysis Figure 6.5a The structure of a Distal long bone (humerus of arm). epiphysis (a) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved The Structure of a Long Bone (Humerus of Arm) Articular cartilage Compact bone Spongy bone Endosteum (b) Figure 6.5b The structure of a long bone (humerus of arm). Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Gross Anatomy  Membranes: two types (periosteum and Endosteum endosteum) – Periosteum: white, double-layered membrane that covers external surfaces except joints Fibrous layer: outer layer consisting of dense irregular connective tissue Yellow consisting of Sharpey’s fibers bone marrow (perforating fibers) that secure to Compact bone bone matrix Osteogenic layer: inner layer Nutrient foramen abutting bone and contains primitive Periosteum osteogenic stem cells that gives rise Perforating to most all bone cells fibers Contains many nerve fibers and Nutrient artery blood vessels that continue on to the shaft through nutrient foramen openings Anchoring points for tendons and ligaments (c) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Gross Anatomy  Membranes (cont.) – Endosteum Delicate connective tissue membrane covering internal bone surface Covers trabeculae of spongy bone Lines canals that pass through compact bone Like periosteum, contains osteogenic cells that can differentiate into other bone cells Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Gross Anatomy Hematopoietic tissue in bones – Red marrow is found within trabecular cavities of spongy bone and diploë of flat bones, such as sternum  In newborns, medullary cavities and all spongy bone contain red marrow  In adults, red marrow is located in heads of femur and humerus, but most active areas of hematopoiesis are flat bone diploë and some irregular bones (such as the hip bone)  Yellow marrow can convert to red, if person becomes anemic Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Gross Anatomy Bone markings – Sites of muscle, ligament, and tendon attachment on external surfaces – Areas involved in joint formation or conduits for blood vessels and nerves Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Gross Anatomy Bone markings (cont.) – Three types of markings:  Projection: outward bulge of bone – May be due to increased stress from muscle pull or is a modification for joints  Depression: bowl- or groove-like cut-out that can serve as passageways for vessels and nerves, or plays a role in joints  Opening: hole or canal in bone that serves as passageways for blood vessels and nerves Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 6.2-1 Bone Markings Table 6.2 Bone Markings. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 6.2-2 Bone Markings Table 6.2 Bone Markings. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone Cells of bone tissue – Five major cell types, each of which is a specialized form of the same basic cell type 1. Osteogenic cells 2. Osteoblasts 3. Osteocytes 4. Bone-lining cells 5. Osteoclasts Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone 1. Osteogenic cells – Also called osteoprogenitor cells – Mitotically active stem cells in periosteum and endosteum – When stimulated, they differentiate into osteoblasts or bone-lining cells – Some remain as osteogenic stem cells Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone 2. Osteoblasts – Bone-forming cells that secrete unmineralized bone matrix called osteoid  Osteoid is made up of collagen and calcium-binding proteins  Collagen makes up 90% of bone protein – Osteoblasts are actively mitotic Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Comparison of Different Types of Bone Cells From bone cell lineage Some osteoprogenitor cells become (a) Osteoprogenitor cell (b) Osteoblast Stem cell Matrix-synthesizing cell Responsible for bone growth Figure 6.6a, b Types of bone cells and their derivation. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone 3. Osteocytes – Mature bone cells in lacunae that no longer divide – Maintain bone matrix and act as stress or strain sensors  Respond to mechanical stimuli such as increased force on bone or weightlessness  Communicate information to osteoblasts and osteoclasts (cells that destroy bone) so bone remodeling can occur Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone 4. Bone-lining cells – Flat cells on bone surfaces believed to also help maintain matrix (along with osteocytes) – On external bone surface, lining cells are called periosteal cells – On internal surfaces, they are called endosteal cells Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone 5. Osteoclasts – Derived from same hematopoietic stem cells that become macrophages – Giant, multinucleate cells function in bone resorption (breakdown of bone) – When active, cells are located in depressions called resorption bays – Cells have ruffled borders that serve to increase surface area for enzyme degradation of bone  Also helps seal off area from surrounding matrix Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Comparison of Different Types of Bone Cells From bone cell lineage From white blood cell lineage Some osteoblasts become (b) Osteoblast (c) Osteocyte (d) Osteoclast Matrix-synthesizing cell Mature bone cell Bone-resorbing cell Responsible for bone growth Monitors and maintains the mineralized bone matrix Figure 6.6b,c,d Types of bone cells and their derivation. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved An Osteoclast Bone matrix Osteocyte within a lacuna Ruffled border of osteoclast Nuclei Figure 6.7 An osteoclast. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone Compact bone – Also called lamellar bone – Consists of:  Osteon (Haversian system)  Canals and canaliculi  Interstitial and circumferential lamellae Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone Osteon (Haversian system) – An osteon is the structural unit of compact bone – Consists of an elongated cylinder that runs parallel to long axis of bone  Acts as tiny weight-bearing pillars – An osteon cylinder consists of several rings of bone matrix called lamellae  Lamellae contain collagen fibers that run in different directions in adjacent rings  Withstands stress and resist twisting  Bone salts are found between collagen fibers Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved A Single Osteon Artery with capillaries Structures in the Vein central Nerve fiber canal Lamellae Collagen fibers run in different directions Twisting Figure 6.8 A single osteon. force Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Microscopic Anatomy of Compact Bone Compact bone Spongy bone Canals and canaliculi – Central (Haversian) canal runs through core of osteon  Contains blood Central Perforating canal canal vessels and nerve Endosteum lining bony canals fibers Osteon and covering trabeculae Circumferential – Perforating (Volkmann’s) lamellae canals: canals lined with endosteum that occur at right angles to central canal Perforating fibers (a)  Connect blood Lamellae Periosteal blood vessel vessels and nerves Periosteum of periosteum, medullary cavity, and Nerve central canal Vein Lamellae Artery Central Canaliculi canal Osteocyte Lacunae in a lacuna Interstitial Lacuna (with osteocyte) (b) (c) lamella Figure 6.9 Microscopic anatomy of compact bone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone Canals and canaliculi (cont.) – Lacunae: small cavities that contain osteocytes – Canaliculi: hairlike canals that connect lacunae to each other and to central canal – Osteoblasts that secrete bone matrix maintain contact with each other and osteocytes via cell projections with gap junctions – When matrix hardens and cells are trapped the canaliculi form  Allow communication between all osteocytes of osteon and permit nutrients and wastes to be relayed from one cell to another Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone Interstitial and circumferential lamellae – Interstitial lamellae  Lamellae that are not part of osteon  Some fill gaps between forming osteons; others are remnants of osteons cut by bone remodeling – Circumferential lamellae  Just deep to periosteum, but superficial to endosteum, these layers of lamellae extend around entire surface of diaphysis  Help long bone to resist twisting Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Compact Bone Compact bone Spongy bone Central Perforating canal canal Endosteum lining bony canals Osteon and covering trabeculae Circumferential lamellae Perforating fibers (a) Lamellae Periosteal blood vessel Periosteum Nerve Vein Lamellae Artery Central Canaliculi canal Osteocyte Lacunae in a lacuna Interstitial Lacuna (with osteocyte) (b) (c) lamella Figure 6.9 Microscopic anatomy of compact bone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Bone Spongy bone – Appears poorly organized but is actually organized along lines of stress to help bone resist any stress – Trabeculae, like cables on a suspension bridge, confer strength to bone  No osteons are present, but trabeculae do contain irregularly arranged lamellae and osteocytes interconnected by canaliculi  Capillaries in endosteum supply nutrients Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Flat Bones Consist of a Layer of Spongy Bone Sandwiched between Two Thin Layers of Compact Bone (2 of 2) Spongy bone (diploë) Compact bone Trabeculae of spongy bone Figure 6.4 Structure of a flat bone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Chemical Composition of Bone Bone is made up of both organic and inorganic components – Organic components  Includes osteogenic cells, osteoblasts, osteocytes, bone-lining cells, osteoclasts, and osteoid – Osteoid, which makes up one-third of organic bone matrix, is secreted by osteoblasts Consists of ground substance and collagen fibers, which contribute to high tensile strength and flexibility of bone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Chemical Composition of Bone Organic components (cont.) – Resilience of bone is due to sacrificial bonds in or between collagen molecules that stretch and break to dissipate energy and prevent fractures – If no additional trauma, bonds re-form Inorganic components – Hydroxyapatites (mineral salts)  Makeup 65% of bone by mass  Consist mainly of tiny calcium phosphate crystals in and around collagen fibers  Responsible for hardness and resistance to compression Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Chemical Composition of Bone Inorganic components (cont.) – Bone is half as strong as steel in resisting compression and as strong as steel in resisting tension – Lasts long after death because of mineral composition – Can reveal information about ancient people Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Human Anatomy and Physiology Eleventh Edition Chapter 06 Part B Bones and Skeletal Tissues PowerPoint® Lecture Slides prepared by Karen Dunbar Kareiva, Ivy Tech Community College Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.5 Bone Development Ossification (osteogenesis) is the process of bone tissue formation – Formation of bony skeleton begins in month 2 of development – Postnatal bone growth occurs until early adulthood – Bone remodeling and repair are lifelong Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Formation of the Bony Skeleton Up to about week 8, fibrous membranes and hyaline cartilage of fetal skeleton are replaced with bone tissue Endochondral ossification – Bone forms by replacing hyaline cartilage – Bones are called cartilage (endochondral) bones – Form most of skeleton Intramembranous ossification – Bone develops from fibrous membrane – Bones are called membrane bones Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Formation of the Bony Skeleton Endochondral ossification – Forms essentially all bones inferior to base of skull, except clavicles – Begins late in month 2 of development – Uses previously formed hyaline cartilage models – Requires breakdown of hyaline cartilage prior to ossification – Begins at primary ossification center in center of shaft  Blood vessels infiltrate perichondrium, converting it to periosteum  Mesenchymal cells specialize into osteoblasts Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Formation of the Bony Skeleton Five main steps in the process of ossification: – Bone collar forms around diaphysis of cartilage model – Central cartilage in diaphysis calcifies, then develops cavities – Periosteal bud invades cavities, leading to formation of spongy bone  Bud is made up of blood vessels, nerves, red marrow, osteogenic cells, and osteoclasts Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Formation of the Bony Skeleton Five main steps in the process of ossification (cont.): – Diaphysis elongates, and medullary cavity forms  Secondary ossification centers appear in epiphyses – Epiphyses ossify  Hyaline cartilage remains only in epiphyseal plates and articular cartilages Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Endochondral Ossification in a Long Bone (1 of 5) Week 9 Hyaline cartilage Bone collar Primary ossification center 1 Bone collar forms around the diaphysis of the hyaline cartilage model. Figure 6.10 Endochondral ossification in a long bone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Endochondral Ossification in a Long Bone (2 of 5) Week 9 Area of deteriorating cartilage matrix Hyaline cartilage Bone collar Primary ossification center 1 Bone collar 2 Cartilage forms calcifies around the diaphysis in the center of the of the hyaline diaphysis and then cartilage model. develops cavities. Figure 6.10 Endochondral ossification in a long bone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Endochondral Ossification in a Long Bone (3 of 5) Week 9 Month 3 Area of deteriorating cartilage matrix Hyaline cartilage Spongy bone formation Bone Blood collar vessel of Primary periosteal ossification bud center 1 Bone collar 2 Cartilage 3 The periosteal forms calcifies bud invades the around the diaphysis in the center of the internal cavities and of the hyaline diaphysis and then spongy bone forms. cartilage model. develops cavities. Figure 6.10 Endochondral ossification in a long bone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Endochondral Ossification in a Long Bone (4 of 5) Week 9 Month 3 Birth Secondary ossification center Epiphyseal Area of blood vessel deteriorating cartilage matrix Hyaline cartilage Medullary Spongy bone cavity formation Bone Blood collar vessel of Primary periosteal ossification bud center 1 Bone collar 2 Cartilage 3 The periosteal 4 The diaphysis forms calcifies bud invades the elongates and a around the diaphysis in the center of the internal cavities and medullary cavity forms. of the hyaline diaphysis and then spongy bone forms. Secondary ossification cartilage model. develops cavities. centers appear in the Figure 6.10 Endochondral ossification in a long bone. epiphyses. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Endochondral Ossification in a Long Bone (5 of 5) Week 9 Month 3 Birth Childhood to adolescence Articular cartilage Secondary Spongy ossification bone center Epiphyseal Area of blood vessel deteriorating Epiphyseal cartilage matrix plate cartilage Hyaline cartilage Medullary Spongy bone cavity formation Bone Blood collar vessel of Primary periosteal ossification bud center 1 Bone collar 2 Cartilage 3 The periosteal 4 The diaphysis 5 The epiphyses forms calcifies bud invades the elongates and a ossify. around the diaphysis in the center of the internal cavities and medullary cavity forms. When ossification is of the hyaline diaphysis and then spongy bone forms. Secondary ossification complete, hyaline cartilage model. develops cavities. centers appear in the cartilage remains only in Figure 6.10 Endochondral ossification in a long bone. epiphyses. the epiphyseal plates and articular cartilages. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Endochondral Ossification Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Formation of the Bony Skeleton Intramembranous ossification: begins within fibrous connective tissue membranes formed by mesenchymal cells – Forms cranial bonds of the skull - frontal, parietal, occipital, temporal – clavicle bones Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Formation of the Bony Skeleton Four major steps are involved: – Ossification centers are formed when mesenchymal cells cluster and become osteoblasts – Osteoid is secreted, then calcified – Woven bone is formed when osteoid is laid down around blood vessels, resulting in trabeculae  Outer layer of woven bone forms periosteum – Lamellar bone replaces woven bone, and red marrow appears Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Intramembranous Ossification (1 of 4) Mesenchymal cell Collagen fiber Ossification center Osteoid Osteoblast 1 Ossification centers develop in the fibrous connective Mesenchymal cells cluster and differentiate into osteoblasts, tissue membrane. forming an ossification center. Figure 6.11 Intramembranous ossification. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Intramembranous Ossification (2 of 4) Mesenchymal Osteoblast cell Collagen Osteoid fiber Ossification Osteocyte center Newly calcified Osteoid bone matrix Osteoblast 1 Ossification centers develop in the fibrous 2 Osteoid is secreted and connective calcifies. Osteoblasts continue to secrete osteoid, which calcifies in a Mesenchymal cells cluster and differentiate into osteoblasts, tissue membrane. few days. forming an ossification center. Trapped osteoblasts become osteocytes. Figure 6.11 Intramembranous ossification. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Intramembranous Ossification (3 of 4) Mesenchymal Osteoblast cell Collagen Osteoid fiber Ossification Osteocyte center Newly calcified Osteoid bone matrix Osteoblast 1 Ossification centers develop in the fibrous 2 Osteoid is secreted and connective calcifies. Osteoblasts continue to secrete osteoid, which calcifies in a Mesenchymal cells cluster and differentiate into osteoblasts, tissue membrane. few days. forming an ossification center. Trapped osteoblasts become osteocytes. Mesenchyme condensing to form the periosteum Trabeculae of immature spongy bone Blood vessel 3 Immature spongy bone and periosteum form. Accumulating osteoid is laid down between embryonic blood vessels, forming a honeycomb of immature spongy bone. Vascularized mesenchyme condenses on the external face of the bone and becomes the periosteum. Figure 6.11 Intramembranous ossification. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Intramembranous Ossification (4 of 4) Mesenchymal Osteoblast cell Collagen Osteoid fiber Ossification Osteocyte center Newly calcified Osteoid bone matrix Osteoblast 1 Ossification centers develop in the fibrous 2 Osteoid is secreted and connective calcifies. Osteoblasts continue to secrete osteoid, which calcifies in a Mesenchymal cells cluster and differentiate into osteoblasts, tissue membrane. few days. forming an ossification center. Trapped osteoblasts become osteocytes. Mesenchyme Fibrous condensing periosteum to form the Osteoblast periosteum Plate of Trabeculae of compact bone immature spongy bone Diploë (spongy Blood vessel bone) cavities contain red marrow 3 Immature spongy bone and periosteum form. 4 Compact bone replaces immature spongy bone, just Accumulating osteoid is laid down between embryonic blood deep to vessels, forming a honeycomb of immature spongy bone. Trabeculae justRed the periosteum. deep to the periosteum marrow develops.are remodeled and replaced with compact bone. Vascularized mesenchyme condenses on the external face of the bone and becomes the periosteum. The immature spongy bone in the center is remodeled into mature spongy bone that is eventually filled with red marrow. Figure 6.11 Intramembranous ossification. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Postnatal Bone Growth Long bones grow lengthwise by interstitial (longitudinal) growth of epiphyseal plate Bones increase thickness through appositional growth Bones stop growing during adolescence – Some facial bones continue to grow slowly through life Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth in Length of Long Bones Interstitial growth requires presence of epiphyseal cartilage in the epiphyseal plate Epiphyseal plate maintains constant thickness – Rate of cartilage growth on one side balanced by bone replacement on other Epiphyseal plate consists of five zones: 1. Resting (quiescent) zone 2. Proliferation (growth) zone 3. Hypertrophic zone 4. Calcification zone 5. Ossification (osteogenic) zone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth in Length of Long Bones Resting (quiescent) zone – Area of cartilage on epiphyseal side of epiphyseal plate that is relatively inactive Proliferation (growth) zone – Area of cartilage on diaphysis side of epiphyseal plate that is rapidly dividing – New cells formed move upward, pushing epiphysis away from diaphysis, causing lengthening Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth in Length of Long Bones Hypertrophic zone – Area with older chondrocytes closer to diaphysis – Cartilage lacunae enlarge and erode, forming interconnecting spaces Calcification zone – Surrounding cartilage matrix calcifies; chondrocytes die and deteriorate Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth in Length of Long Bones Ossification zone – Chondrocyte deterioration leaves long spicules of calcified cartilage at epiphysis-diaphysis junction – Spicules are then eroded by osteoclasts and are covered with new bone by osteoblasts – Ultimately replaced with spongy bone – Medullary cavity enlarges as spicules are eroded Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth in Length of a Long Bone Occurs at the Epiphyseal Plate Resting zone 1 Proliferation zone Cartilage cells undergo mitosis. 2 Hypertrophic zone Older cartilage cells enlarge. (a) X-ray image of right knee, anterior 3 Calcification zone view. Proximal epiphyseal plate of Matrix becomes the tibia enlarged in part (b). calcified; cartilage cells die; matrix Calcified begins deteriorating. cartilage spicule Osseous 4 Ossification tissue zone New bone is forming. (b) Photomicrograph of (c) Diagram of the zones cartilage in the epiphyseal within the epiphyseal plate (125x). plate. Figure 6.12 Growth in length of a long bone occurs at the epiphyseal plate. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth in Length of Long Bones Near end of adolescence, chondroblasts divide less often Epiphyseal plate thins, then is replaced by bone Epiphyseal plate closure occurs when epiphysis and diaphysis fuse Bone lengthening ceases – Females: occurs around 18 years of age – Males: occurs around 21 years of age Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth in Width (Thickness) Growing bones widen as they lengthen through appositional growth – Can occur throughout life Bones thicken in response to increased stress from muscle activity or added weight Osteoblasts beneath periosteum secrete bone matrix on external bone Osteoclasts remove bone on endosteal surface Usually more building up than breaking down which leads to thicker, stronger bone that is not too heavy Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Long Bone Growth and Remodeling During Youth Before growth After growth and remodeling and remodeling As the bone grows in length, remodeling (resorption and deposition) maintains the bone’s shape. Articular and epiphyseal plate cartilage grows and is replaced by bone (endochondral Outline of bone ossification). before growth and remodeling. Articular cartilage Epiphyseal Bone that was plate here has been resorbed. Bone was added here by appositional growth. Figure 6.13 Long bone growth and remodeling during youth. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Hormonal Regulation of Bone Growth Growth hormone: most important hormone in stimulating epiphyseal plate activity in infancy and childhood Thyroid hormone: modulates activity of growth hormone, ensuring proper proportions Testosterone (males) and estrogens (females) at puberty: promote adolescent growth spurts – End growth by inducing epiphyseal plate closure Excesses or deficits of any hormones cause abnormal skeletal growth Robert Wadlow, Hypertrophy of his pituitary gland, excessive growth hormone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.6 Bone Remodeling About 5–10% of our skeleton is replaced every year – Spongy bone entirely replaced ~ every 3-4 years – Compact bone entirely replaced ~ every 10 years Bone remodeling consists of both bone deposit and bone resorption – Occurs at surfaces of both periosteum and endosteum – Remodeling units: packets of adjacent osteoblasts and osteoclasts coordinate remodeling process Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Bone Resorption Resorption is function of osteoclasts – Dig depressions or grooves as they break down matrix – Secrete lysosomal enzymes and protons (H+) that digest matrix – Acidity converts calcium salts to soluble forms Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Bone Resorption Osteoclasts also phagocytize demineralized matrix and dead osteocytes – Digested products are transcytosed across cell and released into interstitial fluid and then into blood – Once resorption is complete, osteoclasts undergo apoptosis Osteoclast activation involves PTH (parathyroid hormone) and immune T cell proteins Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Bone Deposit New bone matrix is deposited by osteoblasts Osteoid seam: band of unmineralized bone matrix that marks area of new matrix Calcification front: abrupt transition zone between osteoid seam and older mineralized bone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Control of Remodeling Remodeling occurs continuously but is regulated by genetic factors and two control loops – Hormonal controls  Negative feedback loop that controls blood Ca2+levels  Calcium functions in many processes, such as nerve transmission, muscle contraction, blood coagulation, gland and nerve secretions, as well as cell division  99% of 1200–1400 gms of calcium are found in bone  Intestinal absorption of Ca2+requires vitamin D – Response to mechanical stress Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Control of Remodeling Hormonal controls – Parathyroid hormone (PTH): produced by parathyroid glands in response to low blood calcium levels  Stimulates osteoclasts to resorb bone  Calcium is released into blood, raising levels  PTH secretion stops when homeostatic calcium levels are reached – Calcitonin: produced by parafollicular cells of thyroid gland in response to high levels of blood calcium levels  Effects are negligible, but at high pharmacological doses it can lower blood calcium levels temporarily Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Parathyroid Hormone (PTH) Control of Blood Calcium Levels I MB AL AN CE Calcium homeostasis of blood: 9–11 mg/100 ml BALANCE BALANCE Stimulus: Falling blood I MB Ca2+ levels AL AN CE Thyroid gland Osteoclasts degrade bone Parathyroid matrix and release Parathyroid glands Ca2+ into blood. glands release parathyroid hormone (PTH). PTH Figure 6.14 Parathyroid hormone (PTH) control of blood calcium levels. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Control of Remodeling Response to mechanical stress – Bones reflect stresses they encounter  Bones are stressed when weight bears on them or muscles pull on them – Wolf’s law states that bones grow or remodel in response to demands placed on them  Stress is usually off center, so bones tend to bend  Bending compresses one side, stretches other side – Diaphysis is thickest where bending stresses are greatest – Bone can be hollow because compression and tension cancel each other out in center of bone Astronaut treadmill Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Bone Anatomy Load here (body weight) threatens to bend this and Bending bone along this arc. Stress Head of femur (thigh bone) Tension Compression here here Point of no stress. The tension (pull) and compression Figure 6.15 Bone anatomy and on opposite sides cancel each other. As a result, much less bending stress. bone material is needed internally than superficially. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Control of Remodeling – Wolf’s law also explains:  Handedness (right- or left-handed) results in thicker and stronger bone of the corresponding upper limb  Curved bones are thickest where most likely to buckle  Trabeculae form trusses along lines of stress  Large, bony projections occur where heavy, active muscles attach – Weight lifters have enormous thickenings at muscle attachment sites of most used muscles  Bones of fetus and bedridden people are featureless because of lack of stress on bones Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.7 Bone Repair Fractures are breaks – During youth, most fractures result from trauma – In old age, most result from weakness of bone due to bone thinning Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Fracture Classification Three “either/or” fracture classifications – Position of bone ends after fracture  Nondisplaced: ends retain normal position  Displaced: ends are out of normal alignment – Completeness of break  Complete: broken all the way through  Incomplete: not broken all the way through – Whether skin is penetrated  Open (compound): skin is penetrated  Closed (simple): skin is not penetrated Can also be described by location of fracture, external appearance, and nature of break Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 6.3-1 Common Types of Fractures (1 of 3) Table 6.3 Common Types of Fractures. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 6.3-2 Common Types of Fractures (2 of 3) Table 6.3 Common Types of Fractures. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 6.3-3 Common Types of Fractures (3 of 3) Table 6.3 Common Types of Fractures. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Fracture Treatment and Repair Treatment involves reduction, the realignment of broken bone ends – Closed reduction: physician manipulates to correct position – Open reduction: surgical pins or wires secure ends – Immobilization of bone by cast or traction is needed for healing  Time needed for repair depends on break severity, bone broken, and age of patient Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Fracture Treatment and Repair Repair involves four major stages: 1. Hematoma formation 2. Fibrocartilaginous callus formation 3. Bony callus formation 4. Bone remodeling Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Fracture Treatment and Repair Hematoma formation – Torn blood vessels hemorrhage, forming mass of clotted blood called a hematoma – Site is swollen, painful, and inflamed Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Stages in the Healing of a Bone Fracture (1 of 5) Hematoma 1 A hematoma forms. Figure 6.16 Stages in the healing of a bone fracture. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Fracture Treatment and Repair Fibrocartilaginous callus formation – Capillaries grow into hematoma – Phagocytic cells clear debris – Fibroblasts secrete collagen fibers to span break and connect broken ends – Fibroblasts, cartilage, and osteogenic cells begin reconstruction of bone  Create cartilage matrix of repair tissue  Osteoblasts form spongy bone within matrix – This mass of repair tissue is called fibrocartilaginous callus Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Stages in the Healing of a Bone Fracture Fibro- cartilaginous (soft) callus New blood vessels 2 Fibrocartilagi nous callus forms. Figure 6.16 Stages in the healing of a bone fracture. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Fracture Treatment and Repair Bony callus formation – Within one week, new trabeculae appear in fibrocartilaginous callus – Callus is converted to bony (hard) callus of spongy bone – Bony callus formation continues for about 2 months until firm union forms Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Stages in the Healing of a Bone Fracture Bony callus of spongy bone 3 Bony callus forms. Figure 6.16 Stages in the healing of a bone fracture. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Fracture Treatment and Repair Bone remodeling – Begins during bony callus formation and continues for several months – Excess material on diaphysis exterior and within medullary cavity is removed – Compact bone is laid down to reconstruct shaft walls – Final structure resembles original structure  Responds to same mechanical stressors Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Stages in the Healing of a Bone Fracture Healed fracture 4 Bone remodeling occurs. Figure 6.16 Stages in the healing of a bone fracture. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Stages in the Healing of a Bone Fracture Hematoma Fibro- Bony Cartilaginous callus of (Soft) callus spongy bone New Healed blood fracture vessels 1 A hematoma forms. 2 Fibrocartilagi 3 Bony callus forms. 4 Bone nous remodeling callus forms. occurs. Figure 6.16 Stages in the healing of a bone fracture. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 6.8 Bone Disorders Imbalances between bone deposit and bone resorption underlie nearly every disease that affects the human skeleton. Three major bone diseases: – Osteomalacia and rickets – Osteoporosis Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Osteomalacia and Rickets Osteomalacia – Bones are poorly mineralized – Osteoid is produced, but calcium salts not adequately deposited – Results in soft, weak bones – Pain upon bearing weight Rickets (osteomalacia of children) – Results in bowed legs and other bone deformities because bones ends are enlarged and abnormally long – Cause: vitamin D deficiency or insufficient dietary calcium Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Osteoporosis Osteoporosis is a group of diseases in which bone resorption exceeds deposit Matrix remains normal, but bone mass declines – Spongy bone of spine and neck of femur most susceptible  Vertebral and hip fractures common Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved The Contrasting Architecture of Normal Versus Osteoporotic Bone (a) Normal bone Figure 6.17 The contrasting architecture of normal versus osteoporotic bone. (b) Osteoporotic bone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Osteoporosis Risk factors for osteoporosis – Most often aged, postmenopausal women  Affects 30% of women aged 60–70 years and 70% by age 80  Estrogen plays a role in bone density, so when levels drop at menopause, women run higher risk – Men are less prone due to protection by the effects of testosterone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Osteoporosis Additional risk factors for osteoporosis: – Insufficient exercise to stress bones – Diet poor in calcium and protein – Smoking – Genetics – Hormone-related conditions  Hyperthyroidism  Diabetes mellitus – Consumption of alcohol or certain medications Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Osteoporosis Treating osteoporosis – Traditional treatments  Calcium  Vitamin D supplements  Weight-bearing exercise  Hormone replacement therapy – Slows bone loss but does not reverse it – Controversial because of increased risk of heart attack, stroke, and breast cancer Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Osteoporosis Preventing osteoporosis – Plenty of calcium in diet in early adulthood – Reduce consumption of carbonated beverages and alcohol  Leach minerals from bone, so decrease bone density – Plenty of weight-bearing exercise  Increases bone mass above normal for buffer against age-related bone loss Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Copyright Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved