Chapter 6 Bone and Bone Tissue PDF

SKELETAL SYSTEM CHAPTER 6 FOUR COMPONENTS OF SKELETAL SYSTEM 1. Bone (spongy and compact) 2. Cartilage (hyaline, fibrocartilage, elastic) 3. Tendons (dense regular CT) 4. Ligaments (dense regular CT) FUNCTIONS OF THE SKELETAL SYSTEM: FUNCTIONS OF BONE AND SKELETAL SYSTEM Support  Stru...

SKELETAL SYSTEM CHAPTER 6 FOUR COMPONENTS OF SKELETAL SYSTEM 1. Bone (spongy and compact) 2. Cartilage (hyaline, fibrocartilage, elastic) 3. Tendons (dense regular CT) 4. Ligaments (dense regular CT) FUNCTIONS OF THE SKELETAL SYSTEM: FUNCTIONS OF BONE AND SKELETAL SYSTEM Support  Structural framework of the body Supports the body’s weight Supports soft tissues Provides attachment points for tendons of skeletal muscle Protection  Protects important internal organs Cranium protects brain Vertebrae protects spinal cord Ribs protect lungs and heart FUNCTIONS OF BONE AND SKELETAL SYSTEM CONT. Assistance in Movement  Skeletal muscle attaches to bone Skeletal muscle contraction pulls on bone producing movement Mineral Homeostasis  Bone tissue stores several minerals Acts to serve as a reservoir of critical minerals  Calcium (99% of body’s content)  Phosphorus FUNCTIONS OF BONE AND SKELETAL SYSTEM CONT. Blood Cell Production  Red bone marrow produces (Hemopoiesis) Red blood cells White blood cells Platelets Triglyceride Storage  Yellow bone marrow Triglycerides stored in adipose cells  Serves as a potential chemical energy reserve CLASSIFICATION OF BONES STRUCTURE OF LONG BONES MATCH THE FOLLOWING TERMS WITH THE CORRECT DEFINITION A. line of hyaline cartilage found in developing bones of children ___ 1. Articular cartilage B. provides cavity for bone marrow ___ 2. Compact bone C. Hollow cavity within diaphysis that contains either red or yellow bone marrow ___ 3. Diaphysis D. Shaft of long bone ___ 4. Endosteum E. membrane composed of dense irregular ___ 5. Epiphysis connective tissue; rich with blood vessels and nerves; surrounds outer surface of long bones ___ 6. Epiphyseal plate F. anchors periosteum to underlying bone ___ 7. Medullary cavity G. lines inner surface of bone, contain different ___ 8. Periosteum types of bone cells ___ 9. Perforating fibers H. ends of long bones ___ 10. Spongy bone I. covers epiphysis preventing friction at joints J. External layer, completely solid MATCH THE FOLLOWING TERMS WITH THE CORRECT DEFINITION CONT. A. line of hyaline cartilage found in developing I. 1. Articular cartilage bones of children B. provides cavity for bone marrow J. 2. Compact bone C. Hollow cavity within diaphysis that contains D. 3. Diaphysis either red or yellow bone marrow D. Shaft of long bone G. 4. Endosteum E. membrane composed of dense irregular H. 5. Epiphysis connective tissue; rich with blood vessels and A. 6. Epiphyseal plate nerves; surrounds outer surface of long bones C. 7. Medullary cavity F. anchors periosteum to underlying bone E. 8. Periosteum G. lines inner surface of bone, contain different types of bone cells F. 9. Perforating fibers H. ends of long bones B. 10. Spongy bone I. covers epiphysis preventing friction at joints J. External layer, completely solid BLOOD AND NERVES SUPPLY OF BONE TISSUE Periosteal arteries accompanied by nerves supply the periosteum and compact bone Epiphyseal veins carry blood away from long bones The periosteum is rich in sensory nerves sensitive to tearing or tension Short, Irregular, and Flat Bone Structure contain bone marrow but no marrow cavity  BONE MARROW RED BONE MARROW YELLOW BONE MARROW forms hematopoietic triglycerides, blood cells vessels, and adipocytes 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 BONE MARROW TRANSPLANTATION Blood diseases such as: Leukemia sickle-cell anemia aplastic anemia Needle inserted into pelvic bone of matching donor red marrow withdrawn recipient’s marrow is destroyed donor marrow given intravenously cells travel to recipient’s marrow cavities production of new blood cells in 24 weeks if successful Complications flu-like symptoms (first 24 weeks) Infection transplant rejection PERIPHERAL BLOOD STEM CELL (P B S C) DONATION possible alternative to bone marrow transplant a donor is given an injection of a drug that stimulates release of hematopoietic cells from the bone marrow into the blood blood is removed from the donor and the hematopoietic cells are filtered out, removed, and blood is returned to the donor process is similar to plasma donation INORGANIC COMPOSITION OF BONE TISSUE makes ups 65% consist of hydroxyapatite (salt containing Ca2+ phosphate) bone stores around 85% of total calcium ions as well as large amount of phosphorus crystalline structure makes bone one of hardest substances in body; strong and resistant to compression allows bone to be both protective and supportive ORGANIC COMPOSITION OF BONE TISSUE makes up 35% composed mostly of cells collagenous fibers proteoglycans glycoproteins IMPORTANCE OF BONE MATRICES TWO FORMS OF BONE TISSUE: Compact bone (lamella bone) external layer, completely solid resist a great amount of stress that would typically strain or deform an object Functional unit called osteons or Haversian system Osteons consist of a central (Haversian) canal with concentrically arranged lamellae, lacunae, osteocytes, and canaliculi Spongy bone (trabecular) internal to compact bone resists forces from many directions and forms a protective framework for the bone marrow although not weight bearing contains spaces like honeycomb open spaces contain red or yellow bone marrow In compact bone, the basic functional unit is the osteon  OSTEON STRUCTURE Lamellae (Concentric Lamellae) —Rings of very thin layers of bone; Osteons contain 4 to 20 lamellae; Collagen fibers of adjacent lamellae run in opposite directions which resists twisting and bending forces Central (Haversian) Canal—Contains blood vessels and nerves; lined by endosteum Lacunae—Small cavities between lamellae filled with E C F; About 20,000–30,000 osteocytes and lacunae are found in each cubic millimeter of bone  OSTEON STRUCTURE CONT. Canaliculi—Tiny canals that connect lacunae; Filled with thin cytoplasmic extensions of osteocytes that contact each other through gap junctions Compact bone is composed of multiple osteons connected by Interstitial Lamellae internally, and Circumferential Lamellae in the inner and outer rings that strengthen bone Perforating (Volkmann) Canals connect central canals of neighboring osteons and carry blood vessels from the periosteum to the central canals FILL IN THE BLANKS The functional unit of compact bone is called an __________. It consists of rings of bone matrix called _______that surround a structure called the ____________ that contains blood vessels and nerves. Other structures called _________________ also contain blood vessels and nerves. Osteocytes are housed in _____________ and communicate via __________________. FILL IN THE BLANKS CONT. The functional unit of compact bone is called an osteon. It consists of rings of bone matrix called lamellae that surround a structure called the central canal that contains blood vessels and nerves. Other structures called perforating canals also contain blood vessels and nerves. Osteocytes are housed in lacunae and communicate via canaliculi. STRUCTURE OF SPONGY BONE HISTOLOGY OF SPONGY BONE lacks osteons lamellae are arranged in a lattice of thin columns called trabeculae spaces between the trabeculae make bones lighter trabeculae of spongy bone support and protect the red bone marrow hemopoiesis (blood cell production) occurs in spongy bone HISTOLOGY OF SPONGY TISSUE interior bone tissue is made up primarily of spongy bone (trabeculae) within each trabecula are lacunae that contain osteocytes osteocytes are nourished from the blood circulating through the trabeculae trabeculae of spongy bone are oriented along lines of stress helps bones resist stresses without breaking BONE CELLS CELLS INVOLVED IN BONE GROWTH AND MAINTENANCE. Osteoprogenitor (osteogenic) cells stem cells from embryonic mesenchyme divide and become osteoblast Osteoblasts metabolically active bone cells in periosteum and endosteum bone forming cells secrete bone matrix inactive cells (flat) active cells (cube shaped) collagen calcium-binding proteins CELLS INVOLVED IN BONE GROWTH AND MAINTENANCE CONT. Osteocytes spidery shaped mature bone cells in lacunae maintain structure and density of normal bone Osteoclasts giant multicellular cells Ruffled borders release enzymes that break down bone mineral salts collagen fibers calcium  OSSIFICATION (OSTEOGENESIS) Ossification occurs in steps: Primary (Woven) Bone mature bone consisting of irregularly arranged collagen bundles, abundant osteocytes, and little inorganic matrix in most locations of the body, primary bone is resorbed by osteoclasts and replaced by secondary bone Secondary (Lamellar) Bone strong, mature bone with fully formed lamellae and organized, parallel collagen bundles and a higher percentage of inorganic matrix PROCESS BY WHICH BONE FORMS IS CALLED OSSIFICATION Bone formation occurs in four situations: 1. bone formation in embryo and fetus 2. growth of bones during infancy, childhood and adolescence 3. remodeling of bone throughout life 4. repair of fractures in bone  INTRAMEMBRANOUS OSSIFICATION Forms bones of skull, most facial bones, medial part of clavicle and fontanels Mesenchymal cells differentiate into osteogenic cells and then into osteoblasts Osteoblasts secrete organic matrix, which calcifies, and trapped osteoblasts become osteocytes Calcification is the process in which calcium salts and other components of the inorganic matrix are deposited in the primary ossification center Osteoblasts lay down trabeculae of early spongy bone, and some of the surrounding mesenchyme differentiates into the periosteum Osteoblasts in the periosteum lay down early compact bone INTRAMEMBRANOUS OSSIFICATION  ENDOCHONDRAL OSSIFICATION begins during the fetal period for most bones, but some, such as those in the wrist and ankle, ossify later The hyaline cartilage model consists of chondrocytes and cartilage EC M surrounded by a perichondrium immature cartilage cells called chondroblasts endochondral ossification begins at primary ossification centers long bones also contain secondary ossification centers within their epiphyses chondroblasts in the perichondrium differentiate into osteoblasts chemical signals trigger the change from chondroblasts to osteogenic cells to osteoblasts Endochondral Ossification ENDOCHONDRAL OSSIFICATION CONT. Growth of bone in length and width Interstitial growth Appositional growth lengthens long bones all bones increase in width occurs at epiphyseal plate bones increase in thickness chondrocytes within cartilage chondroblasts in surrounding divide and secrete new perichondrium produce new matrix cartilage cartilage growth ends with adolescence epiphyseal line is calcified remnant of epiphyseal plate Growth of long bone at epiphyseal plate CORRECTLY ORDER THE FOLLOWING STEPS OF BONE GROWTH IN LENGTH _______Calcified cartilage is replaced with bone in the zone of ossification. _______ Chondrocytes in the zone of proliferation divide by mitosis. _______ Chrondrocytes enter the zone of calcification and dies as their matrix calcifies. _______ Chondrocytes enlarge and cease dividing. CORRECTLY ORDER THE FOLLOWING STEPS OF BONE GROWTH IN LENGTH CONT. 4. Calcified cartilage is replaced with bone in the zone of ossification. 1. Chondrocytes in the zone of proliferation divide by mitosis. 3. Chrondrocytes enter the zone of calcification and dies as their matrix calcifies. 2. Chondrocytes enlarge and cease dividing. FACTORS AFFECTING BONE GROWTH 1. Genetics determine bone shape and size 2. Hormones 3. Nutrition HORMONES Growth factors (IGFs) produced by the liver IGFs stimulate osteoblasts promote cell division at the epiphyseal plate enhance protein synthesis stimulates muscle development in adults Thyroid hormones required for normal growth of all tissues promote bone growth by stimulating osteoblasts Insulin promotes bone growth by increasing the synthesis of bone proteins Sex hormones (estrogen and testosterone) cause of the sudden “growth spurt” that occurs during the teenage year promote changes in females, such as widening of the pelvis shut down growth at epiphyseal plates Effects of Growth Hormone on Body Tissues EXCESS GROWTH HORMONE Childhood – Gigantism usually caused by pituitary tumor epiphyseal growth plates have not closed individuals get very tall due to excessive longitudinal and appositional bone growth (~7 feet) individuals can die at early age Adulthood – Acromegaly epiphyseal growth plates have closed no increase in height, but enlargement of bone, cartilage, and soft tissue skull, bones of face, hands, feet, and tongue affected can cause heart and kidney malfunction; associated with development of diabetes PITUITARY DWARFISM Pituitary Dwarfism hyposecretion of G H prior to closure of the epiphyseal plates individuals are short in stature, but their limbs and trunk are proportional Achondroplasia (Dwarfism) most common type of dwarfism caused by a genetic disorder (abnormal growth factor that affects cartilage) short stature ~ 4 feet BONE REMODELING – continuous process of bone formation and loss after growth in length is finished new bone formed by bone deposition old bone removed by bone resorption Bone remodeling occurs for following reasons: Maintenance of calcium ion homeostasis Replacement of primary bone with secondary bone Bone repair Replacement of old brittle bone with newer bone Adaptation to tension and stress FACTORS AFFECTING BONE GROWTH Nutrition Minerals large amounts of Ca2+, and P smaller amounts of Mn, Mg, and F are required for bone growth and remodeling Vitamins Vitamin D helps build bone by increasing the absorption of calcium from foods in the gastrointestinal tract into the blood Vitamin A stimulates activity of osteoblasts Vitamin C is needed for synthesis of collagen Vitamins K and B12 are also needed for synthesis of bone proteins ROLE OF Ca2+ IN THE BODY transmission of nerve impulses muscle contraction blood coagulation cell division secretion by glands and nerve cells  HORMONAL CONTROL PARATHYROID CALCITONIN HORMONE (PTH) when Ca2+ concentration produced by thyroid decreases in the blood gland PTH is released from the temporally lowers blood parathyroid gland Ca2+ if given in high osteoclast resorb bone doses releasing calcium into the functions in the blood homeostasis of blood when PTH decreases the calcium levels not bone strength or well-being reverse effect takes place decreasing blood Ca2+ levels Maintaining homeostasis: response to low blood calcium ion level by a negative feedback loop. HOW DOES BONE ADJUST TO MECHANICAL STRESS? INCREASE BONE MASS DECREASE BONE MASS Weight bearing activities remove mechanical walking stress running reduce collagen formation lifting weights decrease in Ca2+ levels increases osteoblast activity in bone tissue decreases osteoblast activity THERE ARE TWO PRINCIPAL EFFECTS OF AGING ON BONE TISSUE 1. Loss of bone mass results from the loss of calcium from bone matrix the loss of calcium from bones is one of the symptoms in osteoporosis 2. Brittleness decrease in collagen production causes the bone to become very brittle and susceptible to fracture EFFECTS OF AGING ON BONE TISSUE The level of sex hormones diminishes during middle age, especially in women after menopause A decrease in bone mass occurs Bone resorption by osteoclasts outpaces bone deposition by osteoblasts Female bones generally are smaller and less massive than males Loss of bone mass in old age has a greater adverse effect in females  DISORDERS OF BONES Osteoporosis Characterized by low bone mass Bone reabsorption outpaces bone deposition Occurs most often in women after menopause Osteomalacia Occurs in adults—bones are inadequately mineralized due to the inability to absorb fats in which vitamin D is soluble Rickets Occurs in children - analogous to osteomalacia, insufficient vitamin D Paget’s disease Characterized by excessive rate of bone deposition Osteosarcoma A form of bone cancer FRACTURE AND REPAIR OF BONE Open (compound) fracture The broken ends of the bone protrude through the skin Closed (simple) fracture Does not break the skin Comminuted fracture The bone is splintered, crushed, or broken into pieces Greenstick fracture A partial fracture in which one side of the bone is broken and the other side bends Impacted fracture One end of the fractured bone is forcefully driven into another Pott’s fracture Fracture of the fibula, with injury of the tibial articulation Colles’ fracture A fracture of the radius in which the distal fragment is displaced Stress fracture A series of microscopic fissures in bone Avulsion small piece of bone becomes detached from the main part of a bone BONE FRACTURES Compression Avulsion Spiral Comminuted Avulsion Greenstick HEALING OF A BONE FRACTURE GENERAL PROCESS OF FRACTURE HEALING INVOLVES: 1. Hematoma (blood clot) fills in gap between bone fragments 2. Fibroblasts and chondroblasts (from periosteum) infiltrate hematoma and form soft callus (mixture of hyaline cartilage and collagenous connective tissue); bridges gap between fragments Fibroblasts form dense irregular collagenous connective tissue Osteogenic cells become chondroblasts; secrete hyaline cartilage 3. Osteoblasts build a bone callus 4. The bone callus is remodeled and primary bone is replaced with secondary bone Over several months, the primary bone is resorbed and replaced with secondary bone; The bone callus often remains visible following full healing of the injury CORRECTLY ORDER THE FOLLOWING STEPS OF FRACTURE REPAIR _____Osteoblast in the periosteum lay down a bone callus of primary bone. _____Damaged blood vessels bleed and fill the gap between the bone fragments with a hematoma. _____ The bone callus is remodeled and replaced with secondary bone. _____ Fibroblast, chondroblast, and blood vessels enter the clot and the soft callus begins to bridge the gap between bone fragments. CORRECTLY ORDER THE FOLLOWING STEPS OF FRACTURE REPAIR 3. Osteoblast in the periosteum lay down a bone callus of primary bone. 1. Damaged blood vessels bleed and fill the gap between the bone fragments with a hematoma. 4. The bone callus is remodeled and replaced with secondary bone. 2. Fibroblast, chondroblast, and blood vessels enter the clot and the soft callus begins to bridge the gap between bone fragments. BONE DENSITY Henry is a 65-year old man who was admitted to the emergency room after a fall. A radiograph confirmed that he had fractured the proximal part of his arm bone (surgical neck of the humerus). The radiograph also revealed that his bone matrix was not as dense as it should be for a man his age. A test for blood Ca2+ was normal. Henry confessed that he is a junk food addict who eats few vegetables and never consumes dairy products. In addition, Henry never exercises and seldom goes outdoors except at night. BONE DENSITY 1. Why is Henry more likely than most men his age to break a bone? 2. How have Henry’s eating habits contributed to his low bone density? 3. Would Henry’s PTH levels be lower than normal, normal or higher than normal? 4. What effect has Henry’s nocturnal lifestyle had on his bone density? 5. How has lack of exercise affected his bone density?  REFERENCES Amerman, E. C., 2019., Human Anatomy & Physiology, 2nd edition, Pearson Education, Inc. Marieb, E. N., et al., 2010. Human Anatomy. 5th Edition. Pearson Education, Inc., Pearson Benjamin Cummings. McKinley, M. and O’Loughlin, V. D., 2008. Human Anatomy. 1st edition. McGraw-Hill. Tortora and Derrickson, 2014. Principles of Anatomy & Physiology (14th edition), John Wiley & Sons, Inc. Wise, E., 2008. Laboratory Manual Human Anatomy. 2nd edition McGraw-Hill.