Bio 201 Lecture 3: Bone Tissue PDF

Chapter 6 Bone Tissue  Introduction In this chapter we will cover: – Bone tissue composition – How bone functions, develops, and grows – How bone metabolism is regulated and some of its disorders 7-2  Introd...

Chapter 6 Bone Tissue  Introduction In this chapter we will cover: – Bone tissue composition – How bone functions, develops, and grows – How bone metabolism is regulated and some of its disorders 7-2  Introduction When you look at art bones symbolized death and bones and teeth are the most durable remains of a once-living body Dry bones we see in the laboratory may wrongly suggests that skeleton is non living scaffold of thebody But skeleton is living and it is made out of dynamic tissues, full of cells, permeated with nerves and blood vessels Continually remodels itself and interacts with other organ systems of the body Osteology is the study of bone, that is what we are going to do next couple weeks.  Tissues and Organs of the Skeletal System Expected Learning Outcomes – Name the tissues and organs that compose the skeletal system. – State several functions of the skeletal system. – Distinguish between bones as a tissue and as an organ. – Describe the four types of bones classified by shape. – Describe the general features of a long bone and a flat bone. 7-5  Tissues and Organs of the Skeletal System Skeletal system—composed of bones, cartilages, and ligaments – Form strong, flexible framework of the body – Cartilage—forerunner of most bones Covers many joint surfaces of mature bone Ligaments—hold bones together at the joints Tendons—attach muscle to bone 7-6 Skeletal System Bones Cartilage Ligaments  Functions of the Skeleton Support—holds up the body, supports muscles, mandible and maxilla support teeth Protection—brain, spinal cord, heart, lungs Movement—limb movements, breathing, action of muscle on bone Electrolyte balance—calcium and phosphate ions Acid–base balance—buffers blood against excessive pH changes by releasing or absorbing salts Blood formation—red bone marrow is the chief producer of blood cells 7-8  Bones and Osseous Tissue Bone (osseous tissue)—connective tissue with the matrix hardened by calcium phosphate and other minerals the hardening process of bone is called mineralization or calcification (is bone the hardest substance in the body?) Osseous tissue is only one of the many tissues that make up the bone Individual bones as an organ consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue The word bone donate an organ composed of all these tissues – Continually remodels itself and interacts physiologically with all of the other organ systems of the body – Permeated with nerves and blood vessels, which attests to its sensitivity and metabolic activity 7-9 General Features of Bones Based on their shape: Flat bones – Protect soft organs – Curved but wide and thin, example parietal bone Long bones – Longer than wide – Rigid levers, skeletal muscles act on them to provide movement, example femur Short bones – Equal in length and width – Glide across one another in multiple directions, example bones in wrist and ankle Irregular bones – Elaborate shapes that do not fit into other categories, ethmoid bone 7-10  General Features of Bones Long bone: Outer shell of long bone consist of Compact (dense) bone. In a long bone we can observe: – Diaphysis (shaft)—cylinder of compact bone to provide leverage – Medullary cavity (marrow cavity)—space in the diaphysis of a long bone that contains bone marrow – Epiphyses—enlarged ends of a long bone Enlarged to strengthen joint and attach ligaments and tendons Spongy (cancellous) bone—covered by more durable compact bone – Skeleton three-fourths compact and one-fourth spongy bone by weight – Spongy bone in ends of long bones, and in the middle of most flat, irregular and short bones 7-11  General Features of Bones Long bone: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Articular cartilage Compact (dense) bone— Red bone Epiphysis outer shell of long bone marrow Epiphyseal – Diaphysis (shaft)—cylinder of line Marrow cavity compact bone to provide leverage Yellow bone marrow Periosteum – Medullary cavity (marrow Nutrient foramen Diaphysis cavity)—space in the diaphysis of a long bone that contains bone marrow Site of endosteum Compact bone – Epiphyses—enlarged ends of Spongy bone a long bone Epiphyseal line Enlarged to strengthen joint Epiphyseal plate in kids and attach ligaments and Articular Epiphysis tendons cartilage (a) Living (b) Dried 7-12 Figure 7.1  General Features of Bones Long bone: Articular cartilage Epiphysis Articular cartilage—layer of hyaline cartilage that covers Red bone marrow Epiphyseal line Marrow cavity the joint surface where one Yellow bone marrow bone meets another; allows Periosteum joint to move more freely and Nutrient foramen relatively friction free Diaphysis Nutrient foramina—minute Site of endosteum Compact bone holes in the bone surface that Spongy bone allows blood vessels to Epiphyseal line Epiphyseal plate in kids penetrate Epiphysis Articular cartilage (a) Living (b) Dried 7-13 Figure 7.1  General Features of Bones Long bone: Periosteum—external sheath Articular cartilage that covers bone except where there is articular cartilage Epiphysis – Outer fibrous layer of collagen Red bone marrow Epiphyseal line Some outer fibers continuous Marrow cavity with the tendons that attach Yellow bone marrow muscle to bone Periosteum Perforating (Sharpey) fibers— Nutrient foramen Diaphysis outer collagen fibers that penetrate into the bone matrix, continuous with the tendons. Strong attachment and continuity Site of endosteum Compact bone from muscle to tendon to bone Spongy bone – Inner osteogenic layer of bone- Epiphyseal line Epiphyseal plate in kids forming cells Articular Epiphysis Important to growth of the bone cartilage (a) Living (b) Dried and healing of fractures 7-14 Figure 7.1  General Features of Bones Long bone: Endosteum—thin layer of Articular cartilage Epiphysis Red bone marrow reticular connective tissue Epiphyseal line lining marrow cavity. Has cells Marrow cavity Yellow bone marrow Periosteum – that dissolve osseous tissue Nutrient foramen – and others that deposit it Diaphysis Site of endosteum Compact bone Spongy bone Epiphyseal line Epiphyseal plate Epiphysis in kids Articular cartilage (a) Living (b) Dried 7-15 Figure 7.1  General Features of Bones Long bone: Articular cartilage Epiphysis Epiphyseal plate (growth Red bone marrow plate)—area of hyaline cartilage that separates the Epiphyseal line Marrow cavity Yellow bone marrow marrow spaces of the Periosteum epiphysis and diaphysis Nutrient foramen Diaphysis – Enables growth in length Site of endosteum Compact bone – Epiphyseal line—in adults, a Spongy bone bony scar that marks where Epiphyseal line Epiphyseal plate growth plate used to be Epiphysis in kids Articular cartilage (a) Living (b) Dried 7-16 Figure 7.1  General Features of Bones Long bone: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Articular Epiphyses and cartilage Epiphysis diaphysis Red bone marrow Epiphyseal line Compact and Marrow cavity Yellow bone marrow spongy bone Periosteum Periosteum Nutrient foramen Diaphysis Endosteum Marrow cavity Site of endosteum Compact bone Articular cartilage Spongy bone Epiphyseal line Epiphyseal plate in kids Epiphyseal line Epiphysis Articular cartilage (plate in children) (a) Living (b) Dried 7-17 Figure 7.1 General Features of Bones Flat bone of the cranium: Sandwich-like construction Two layers of compact bone Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. enclosing a middle layer of spongy bone – Both surfaces of flat bone covered with periosteum Suture Diploe—spongy layer in the cranium Outer compact bone – Absorbs shock, some Spongy bone (diploe) trauma can fracture the outer layer of the compact Trabeculae bone but diploe may absorb Inner compact the impact and leave inner bone bone unharmed Figure 7.2 – As in long bone, marrow spaces lined with endosteum  Histology of Osseous Tissue Expected Learning Outcomes – List and describe the cells, fibers, and ground substance of bone tissue. – State the importance of each component of bone tissue. – Compare the histology of the two types of bone tissue. – Distinguish between the two types of bone marrow. 7-19  Bone Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Osteogenic cell Osteoblast Osteocyte Rough Secretory endoplasmic vesicles reticulum Nucleus Mitochondrion (a) Osteocyte development Figure 7.3a Bone is connective tissue that consists of – cells, – fibers, and – ground substance Four principal types of bone cells – Osteogenic cells; – osteoblasts; – osteocytes; – osteoclasts 7-20  Bone Cells Osteogenic cell Osteoblast Osteocyte Rough Secretory endoplasmic vesicles reticulum Nucleus Mitochondrion Figure 7.3a (a) Osteocyte development Osteogenic (osteoprogenitor) cells—stem cells found in endosteum, periosteum, and in central canals – Arise from embryonic mesenchymal cells; multiply continuously to produce new osteoblasts 7-21  Bone Cells Osteogenic cell Osteoblast Osteocyte Rough Secretory endoplasmic vesicles reticulum Nucleus Mitochondrion Figure 7.3a (a) Osteocyte development Osteoblasts—bone-forming cells – Line up as single layer of cells under endosteum and periosteum – Nonmitotic – Synthesize soft organic matter of matrix which then hardens by mineral deposition 7-22  Bone Cells Cont. – Stress and fractures stimulate osteogenic cells to multiply more rapidly and increase number of osteoblasts to reinforce or rebuild bone – Osteoblast secrete hormone osteocalcin—thought to be the only structural protein of bone. Osteocalcin; Stimulates insulin secretion of pancreas Increases insulin sensitivity in adipocytes which limit the growth of adipose tissue Osteogenic cell Osteoblast Osteocyte Rough Secretory endoplasmic vesicles reticulum Nucleus Mitochondrion (a) Osteocyte development 7-23  Bone Cells Osteogenic cell Osteoblast Osteocyte Rough Secretory endoplasmic vesicles reticulum Nucleus Mitochondrion (a) Osteocyte development Figure 7.3a Osteocytes—former osteoblasts that have become trapped in the matrix they have deposited – Lacunae—tiny cavities where osteocytes reside – Canaliculi—little channels that connect lacunae – Cytoplasmic processes reach into canaliculi – Some osteocytes resorb bone matrix while others deposit it – Contribute to homeostatic mechanism of bone density and calcium and phosphate ions – When stressed, produce biochemical signals that regulate bone remodeling 7-24 Osteocyte in Lacuna  Bone Cells Osteocyte Osteoclast Osseous tissue Stem cells Periosteum Resorption bay Nuclei Osteoclast Fusion Ruffled Lysosomes border (b) Osteoclast development Figure 7.3b Osteoclasts—bone-dissolving cells found on the bone surface – Osteoclasts develop from same bone marrow stem cells that give rise to blood cells – Different origin from rest of bone cells – Unusually large cells formed from the fusion of several stem cells Typically have 3 to 4 nuclei, may have up to 50 7-26  Bone Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Osteocyte Osteoclast Osseous tissue Stem cells Periosteum Resorption bay Nuclei Osteoclast Fusion Ruffled Lysosomes border (b) Osteoclast development – Ruffled border—side facing bone surface Several deep infoldings of the plasma membrane which increases surface area and resorption (breaking down) efficiency – Resorption bays (Howship lacunae)—pits on surface of bone where osteoclasts reside – Remodeling—results from combined action of the bone- dissolving osteoclasts and the bone-depositing osteoblasts 7-27  The Matrix Matrix of osseous tissue is, by dry weight, about – one-third (1/3) organic and – two-thirds (2/3) inorganic matter Organic matter—synthesized by osteoblasts – Collagen, carbohydrate–protein complexes, such as glycosaminoglycans, proteoglycans, and glycoproteins Inorganic matter – 85% hydroxyapatite (crystallized calcium phosphate salt) – 10% calcium carbonate – Other minerals (fluoride, sodium, potassium, magnesium) 7-28  The Matrix Lack or organic or inorganic material might cause problems: Example Rickets—soft bones due to deficiency of calcium salts (in childhood), or vitamin D deficiency. Osteomalicia (in adults) Osteogenesis imperfecta or brittle bone disease— excessively brittle bones due to lack of protein, collagen 7-29  Histology of Osseous Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Histology of compact bone reveals osteons (haversian systems) Nerve – Concentric lamellae Blood vessel Spicules surround a central (haversian) canal running Trabeculae Spongy bone Endosteum longitudinally Periosteum – Perforating canals (Volkmann)—transverse or Perforating fibers passages – Circumferential lamellae fill Central outer region of dense bone canal Osteon Lacuna Collagen fibers – Interstitial lamellae fill Concentric lamellae irregular regions between Circumferential lamellae osteons (b) Figure 7.4b,c,d 7-30  Histology of Osseous Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Bone marrow Trabecula Pelvic bone Head of femur Spongy bone Compact bone (a) Figure 7.4a (c) Figure 7.4c Lamella Lacunae Canaliculi Central canal (d) Figure 7.4d 7-31 20 m a,c: © Dr. Don W. Fawcett/Visuals Unlimited; d: Visuals Unlimited  Osteon Interstitial lamellae Compact Bone Cement line Central Canal Osteocytes in lacuna  Compact Bone Low Magnification Osteon Interstitial lamellae Central canal Perforating canals  Compact Bone High Magnification Osteon Interstitial lamella Central canal Lamella Osteocytes Lacunae Canaliculi Cement line  Spongy Bone Sponge-like appearance Spongy bone consists of: – Delicate slivers of bone called spicules – Thin plates of bone called trabeculae – Spaces filled with red bone marrow Few osteons and no central canals – All osteocytes close to bone marrow Provides strength with minimal weight – Trabeculae develop along bone’s lines of stress 7-35  Spongy Bone Low Magnification Periosteum Marrow cavity Trabeculae Trabeculae of Spongy Bone  Bone Marrow Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Bone marrow—general term for soft tissue that occupies the marrow cavity of a long bone and trabeculae of spongy bone 7-38  Bone Marrow Red marrow (myeloid tissue) – In nearly every bone in a child – Hemopoietic tissue—produces blood cells – In adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur Yellow marrow found in adults – Most red marrow turns into fatty yellow marrow – No longer produces blood 7-39  Bone Development Expected Learning Outcomes – Describe two mechanisms of bone formation. – Explain how mature bone continues to grow and remodel itself. 7-40  Bone Development Formation of bone is called ossification or osteogenesis. Before the week 8, embryonic skeleton is constructed entirely from fibrous membranes and hyaline cartilage. In the human fetus and infant, bone develops by two methods – Intramembranous ossification – Endochondral ossification 7-41  Intramembranous Ossification Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mesenchymal cell Osteocyte Osteoblasts Sheet of condensing Trabecula mesenchyme Calcified bone Osteoid tissue Blood capillary Fibrous periosteum 1 Condensation of mesenchyme into soft sheet 2 Deposition of osteoid tissue by osteoblasts permeated with blood capillaries. on mesenchymal surface; entrapment of first Mesenchymal cells become osteoblast osteocytes; formation of periosteum Osteoblasts Fibrous periosteum Trabeculae Osteoblasts Osteocytes Spongy bone Marrow cavity Compact bone 3 Honeycomb of bony trabeculae formed by 4 Surface bone filled in by bone deposition, continued mineral deposition; creation of converting spongy bone to compact bone. spongy bone Persistence of spongy bone in the middle layer. Produces flat bones of skull and most of the clavicle  Intramembranous Ossification Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mesenchymal cell Osteocyte Osteoblasts Sheet of condensing Trabecula mesenchyme Calcified bone Osteoid tissue Blood capillary Fibrous periosteum 1 Condensation of mesenchyme into soft sheet 2 permeated with blood capillaries Mesenchymal cells differentiate into osteogenic cells and osteogenic cells differentiate into osteoblast Osteoblasts Fibrous periosteum Osteoblasts deposit osteoid tissue Trabeculae Osteoblasts Osteoid tissue resemblesOsteocytes the bone but it is not calcified Spongy bone Osteoblast trap into matrix and become mature osteocyte Marrow cavity Uncalcified but dense and fibrous Mesenchyme which is close toCompact surface bone forms periosteum 3 Honeycomb of bony trabeculae formed by continued mineral deposition; creation of 4 Surface bone filled in by bone deposition, converting spongy bone to compact bone. Figure 7.7 spongy bone Persistence of spongy bone in the middle layer. 7-43  Intramembranous Ossification Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mesenchymal cell Osteocyte Osteoblast beneath the periosteum deposit layers of bone and Osteoblasts creating sandwich like structure: spongy layer between two compact Trabecula Sheet of condensing bone layers mesenchyme Calcified bone Osteoid tissue Blood capillary Fibrous periosteum 1 2 Osteoblasts Fibrous periosteum Trabeculae Osteoblasts Osteocytes Spongy bone Marrow cavity Compact bone 3 4 Figure 7.7 7-44  Intramembranous Ossification Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Periosteum: Fibrous layer Osteogenic layer Osteoid tissue Osseous tissue (bone) Osteoblasts Osteocytes Figure 7.8 © Ken Saladin Note the periosteum and osteoblasts 7-45  Endochondral Ossification Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Articular Spongy bone cartilage Epiphyseal line Perichondrium Hyaline Secondary Periosteum marrow cavity Epiphyseal cartilage plate 1 Early cartilage model Nutrient Epiphysis Secondary foramen Marrow cavity ossification Metaphysis center Compact bone Enlarging Blood chondrocytes vessel Diaphysis Bony collar Primary Primary marrow ossification cavity center Metaphysis Secondary Periosteum Cartilage ossification center 2 Formation of 3 Vascular invasion, 4 Bone at birth, with 5 Bone of child, with 6 Adult bone with a primary formation of primary enlarged primary epiphyseal plate at single marrow ossification center, marrow cavity, and marrow cavity and distal end cavity and closed bony collar, and appearance of appearance of epiphyseal plate periosteum secondary secondary marrow ossification center cavity in one epiphysis Figure 7.9 7-46  Endochondral Ossification Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Begins around the 6 weeks of fetal development Articular cartilage continues Spongy bone into persons 20s Epiphyseal Early cartilage model: line Perichondrium Mesenchyme (embryonic connective tissue) develops into Hyaline Secondary Periosteum cartilage hyaline cartilage marrow cavity Epiphyseal plate 1 Perichondrium produces Epiphysis chondrocytes Nutrientso cartilage gets Secondary foramen Marrow cavity thicker ossification Metaphysis center Compact bone Enlarging In thevessel primary ossification center chondrocyte begin to die, Blood chondrocytes Bony collar while the thin walls between Diaphysis them calcify Primary Primary Perichondriummarrow starts producing osteoblast ossification cavity center These osteoblasts deposit bone in the middle: primary Metaphysis Secondary ossification center ossification Periosteum Cartilage center 2 Perichondrium 3 Vascular invasion, 4 Bonebecomes at birth, with periosteum 5 Bone of child, with 6 Adult bone with a formation of primary enlarged primary epiphyseal plate at single marrow Walls marrow of matrix cavity, and b/w marrow lacuna cavity and calcify distal end and block cavity nutrients and closed from appearance of appearance of epiphyseal plate reaching chondrocytes secondary secondary marrow cell die and cavity appears ossification center cavity in one epiphysis Figure 7.9 7-47  Endochondral Ossification Vascular invasion, blood brings the osteoclast and they digest calcified tissue forming the hallow primary marrow cavity secondary ossification center Stem cells make osteoblast and osteoclast Articular cartilage Spongy bone Cartilage replaced by bone Epiphyseal line Perichondrium Hyaline Secondary Periosteum marrow cavity Epiphyseal cartilage plate 1 Early cartilage model Nutrient Epiphysis Secondary foramen Marrow cavity ossification Metaphysis: region of transition from cartilage to bone center Compact bone Enlarging Blood chondrocytes vessel Diaphysis Bony collar Primary Primary marrow ossification cavity center Metaphysis Secondary Periosteum Cartilage ossification center 2 Formation of 3 4 5 Bone of child, with 6 Adult bone with a primary Secondary epiphyseal marrowplate cavity at single marrow ossification center, distal end cavity and closed bony collar, and Bone at birth, epiphyseal plate periosteum with enlarged primary marrow cavity and appearance of secondary marrow cavity in one epiphysis Figure 7.9 7-48  Endochondral Ossification Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Articular Spongy bone cartilage Epiphyseal line Perichondrium Hyaline Secondary Periosteum marrow cavity Epiphyseal cartilage plate 1 Early cartilage model Nutrient Epiphysis Secondary foramen Marrow cavity ossification Metaphysis center Compact bone Blood Bone of child, with Enlarging chondrocytes epiphyseal vessel plate at Diaphysis Bony collar distal Primary end Primary marrow ossification cavity center Metaphysis Secondary Periosteum Cartilage ossification center 2 Formation of 3 Vascular invasion, 4 Bone at birth, with 5 6 primary formation of primary enlarged primary By late teens to early 20s all the ossification center, marrow cavity, and marrow cavity and bony collar, and appearance of appearance of cartilage in epiphysial plate is periosteum secondary secondary marrow consumed ossification center cavity in one epiphysis Adult bone with a single marrow cavity and closed epiphyseal plate  Endochondral Ossification During infancy and childhood, the epiphyses fill with spongy bone Cartilage limited to the articular cartilage covering each joint surface, and to the epiphyseal plate – A thin wall of cartilage separating the primary and secondary marrow cavities – Epiphyseal plate persists through childhood and adolescence – Serves as a growth zone for bone elongation 7-50  Endochondral Ossification By late teens to early 20s, all remaining cartilage in the epiphyseal plate is generally consumed – Gap between epiphyses and diaphysis closes – Primary and secondary marrow cavities unite into a single cavity – Bone can no longer grow in length 7-51