Unit 4_ The Skeletal System.pdf

PRAYER BEFORE CLASS Holy Spirit, Divine Creator, true source of light and fountain of wisdom! Pour forth your brilliance upon my dense intellect, dissipate the darkness which covers me, that of sin and of ignorance. Grant me a penetrating mind to understand, a retentive memory, method and ease of le...

PRAYER BEFORE CLASS Holy Spirit, Divine Creator, true source of light and fountain of wisdom! Pour forth your brilliance upon my dense intellect, dissipate the darkness which covers me, that of sin and of ignorance. Grant me a penetrating mind to understand, a retentive memory, method and ease of learning, the lucidity to comprehend, and abundant grace in expressing myself. Guide the beginning of my work, direct its progress and bring it to successful completion. This I ask through Jesus Christ, true God, and true man, living and reigning with You and the Father, forever and ever. Amen. ANATOMY AND PHYSIOLOGY WITH PATHOPHYSIOLOGY THE SKELETAL SYSTEM Formative Assessment 1. What are the main minerals stored in bones? a. Calcium and phosphorus b. Calcium and zinc c. Magnesium and Phosphorus d. Calcium and magnesium Formative Assessment 2. Which component of the bone imparts flexible strength to the bone matrix? a. Collagen b. Hydroxyapatite c. Proteoglycan d. Elastic fibers Formative Assessment 3. Intramembranous ossification is the mode of development in these bones, except : a. Diaphysis of clavicle b. Mandible c. Frontal bones of the skull d. Humerus bone Formative Assessment 4. Active bone resorption is a function of which of the following bone cells? a. Osteogenic cells b. Osteoblast c. Osteoclast d. Osteocytes Formative Assessment 5. Blood calcium levels depend on the movement of this mineral in and out of the bone. Levels of calcium in the blood is controlled by? a. Reproductive hormones b. Growth hormones c. Parathyroid hormone d. Adrenal gland hormones Learning Outcome 1. Describe the normal physiology of the skeletal system, its role in calcium homeostasis, and how disruptions in these processes can lead to various skeletal disorders. Outline Introduction Skeletal System Physiology Diseases of the Skeletal System Diagnostic Tests for Skeletal System Disorders I. INTRODUCTION THE SKELETAL SYSTEM  FUNCTIONS of the Skeletal System 1. Support SUPPORT 2. Protection - Bone: bearing weight, major 3. Movement supporting tissue of the body 4. Storage - Cartilage: firm yet flexible 5. Blood cell production support - Ligaments: holds bone together  FUNCTIONS of the Skeletal System 1. Support PROTECTION 2. Protection - Skull protects the brain 3. Movement - Vertebrae surround the 4. Storage spinal cord 5. Blood cell production - Rib cage protect the heart, lungs, other organs of the thorax  FUNCTIONS of the Skeletal System 1. Support MOVEMENT 2. Protection - Produced by muscles attached to 3. Movement bones via tendons. 4. Storage - Joints allow movement between 5. Blood cell production bones - Smooth cartilage reduce friction - Ligaments allow some movement between bones but prevent excessive movement.  FUNCTIONS of the Skeletal System 1. Support STORAGE 2. Protection - Calcium and phosphorus 3. Movement stored and released as 4. Storage needed. 5. Blood cell production - Adipose tissue stored in marrow cavities.  FUNCTIONS of the Skeletal System 1. Support BLOOD CELL PRODUCTION 2. Protection 3. Movement - Bone marrow that gives rise 4. Storage to blood cells and platelets. 5. Blood cell production  MNEMONIC Some Prefer Mcdo coffee over StarBucks 1. Support 2. Protection 3. Movement 4. Storage 5. Blood cell production  COMPONENTS of the Skeletal System FOUR COMPONENTS 1. Bone 2. Cartilage 3. Tendons 4. Ligaments CARTILAGE TYPES OF CARTILAGE: Hyaline cartilage Fibrocartilage Elastic cartilage CELL TYPES: Chondroblasts: form the matrix, usually found in the perichondrium Chondrocytes: maintains the matrix, are within lacunae CARTILAGE TYPES OF CARTILAGE: Hyaline cartilage Fibrocartilage Elastic cartilage CELL TYPES: Chondroblasts: form the matrix, usually found in the perichondrium Chondrocytes: maintains the matrix, are within lacunae CARTILAGE CARTILAGE MATRIX - Contains collagen for strength, proteoglycans provide resiliency PERICHONDRIUM - Covers the cartilage - Double-layered connective tissue sheath Inner layer: more delicate, fewer fibers, contains chondroblasts Outer layer: blood vessels and nerves penetrate - Nutrient diffuse through the matrix CARTILAGE CARTILAGE GROWTH 1. APPOSITIONAL GROWTH - New matrix is added by the chondroblasts to the surface of the cartilage from the inner layer of perichondrium 2. INTERSTITIAL GROWTH - Chondrocytes divide and produce additional matrix within the cartilage BONE HISTOLOGY BONE MATRIX Organic (35%): collagen and proteoglycans Inorganic (65%): hydroxyapatite (calcium phosphate crystals) Collagen & Minerals = Characteristics of Bone BONE HISTOLOGY BONE CELLS Osteochondral Progenitor Cells - Bone stem cells - from mesenchymal cells - Inner portion of periosteum, endosteum and perichondrium - Undergo cell division Osteoprogenitor cells Osteoblast Osteocyte Osteoclast Osteoblasts (bone building cells) - From osteochondral progenitor cells - Connect to one another thru cell extensions - Produce collagen and proteoglycans - Secrete matrix vesicles - With high concentration of calcium and phosphate BONE HISTOLOGY OSSIFICATION - Formation of new bone by osteoblast - Process carried out by osteoblasts which communicate through gap junctions. - Cells surround themselves by matrix. BONE HISTOLOGY BONE CELLS Osteocytes - Mature bone cells - Relatively inactive but still able to produce Osteoprogenitor cells Osteoblast Osteocyte Osteoclast small amounts of matrix - Connect to one another thru canaliculi - Get nutrients through canaliculi, lacunae or gap junctions Associated Structures: Lacunae ○ Spaces occupied by osteocytes cell body Canaliculi ○ Spaces occupied by osteocytes cell processes BONE HISTOLOGY BONE CELLS Osteoclasts (bone destroying cells) - Massive, multinucleated cells - Derived from monocyte/macrophage lineage stem cells - Macrophages in the tissues Osteoprogenitor cells Osteoblast Osteocyte Osteoclast Associated Structures: Ruffled border ○ Specialized reabsorption-specific area of the membrane ○ Acidic vesicles fuse with the membrane of ruffled border ○ ATP-powered H+ pumps and protein digesting enzymes are inserted into the membrane of ruffled border BONE HISTOLOGY BONE REABSORPTION 1. Osteoblasts recruit osteoclasts to the bone remodelling site 2. Osteoclasts attach to the bone surface Osteoprogenitor cells Osteoblast Osteocyte Osteoclast using integrins and form podosomes 3. Osteoclast plasma membrane differentiates into ruffled border, preparing for bone resorption BONE HISTOLOGY TYPES OF BONE ACCORDING TO COLLAGEN PATTERN Woven bone ○ Collagen fibers are randomly oriented ○ Weak bone ○ Remodelled to form lamellar bone Lamellar bone ○ Stronger “Lakas” bone ○ Organized into thin concentric sheets (lamellae) ○ Collagen fibers arranged parallel to one another ○ Osteocytes are arranged in layers sandwiched between lamellae BONE HISTOLOGY TYPES OF BONE ACCORDING TO AMOUNT OF MATRIX AND SPACE SPONGY BONE - Less bone matrix, more space Associated Structure: Trabeculae ○ Consist of lamellae with osteocytes located in lacunae between lamellae ○ Covered with single layer of osteoblasts and osteoclasts ○ Oriented along stress lines Spaces filled with blood vessels and bone marrow Canaliculi ○ Facilitate exchange of nutrients BONE HISTOLOGY TYPES OF BONE ACCORDING TO AMOUNT OF MATRIX AND SPACE COMPACT BONE - More bone matrix, less space Associated Structure: Osteon or haversian system ○ Functional unit of long bone ○ Composed of central canal, concentric lamellae and osteocytes Perforating or volkmann canals ○ Perpendicular to long axis ○ Connection between osteons ○ Deliver blood to central canals of the osteon ○ Contain blood vessels BONE HISTOLOGY TYPES OF BONE ACCORDING TO AMOUNT OF MATRIX AND SPACE COMPACT BONE - More bone matrix, less space Associated Structure: Central or haversian canal ○ Parallel to long axis ○ Surrounded by concentric lamellae ○ Contains blood vessels, nerves, and loose connective tissue Lamellae ○ Concentric, circumferential, interstitial ○ Oriented around blood vessels BONE HISTOLOGY TYPES OF BONE ACCORDING TO AMOUNT OF MATRIX AND SPACE COMPACT BONE - More bone matrix, less space Associated Structure: Concentric lamellae ○ Surrounds central canal Circumferential lamellae ○ Form outer surfaces of compact bone Interstitial lamellae ○ Remnants of concentric or circumferential lamellae II. PHYSIOLOGY THE SKELETAL SYSTEM BONE DEVELOPMENT INTRAMEMBRANOUS OSSIFICATION - Starts within embryonic connective tissue membranes ENDOCHONDRAL OSSIFICATION - Starts with a cartilage model BONE DEVELOPMENT INTRAMEMBRANOUS OSSIFICATION - Begins 8th week of embryonic development - Completed by approx 2 years of age - Forms many skull bones, part of mandible, diaphyses of clavicles - Centers of ossification: location where ossification begins BONE DEVELOPMENT INTRAMEMBRANOUS OSSIFICATION - Begins 8th week of embryonic development - Completed by approx 2 years of age - Forms many skull bones, part of mandible, diaphyses of clavicles - Centers of ossification: location where ossification begins BONE DEVELOPMENT ENDOCHONDRAL OSSIFICATION - Begins approx 8th week of embryonic development, some does not begin until 18-20 years of age - Forms base of the skull, part of mandible, epiphyses of clavicle and most remaining skeletal system  BONE GROWTH GROWTH IN LENGTH - Long bones and bony projections increase in length d/t growth at epiphyseal plate - Length of diaphysis increases - Involves endochondral ossification - Interstitial cartilage growth followed by appositional bone growth - Closure of epiphyseal plate: ossified becoming epiphyseal line (12-25 years of age) BONE GROWTH GROWTH IN LENGTH - Occurs at the epiphyseal plate, organized into five zones BONE GROWTH GROWTH AT ARTICULAR CARTILAGE - Increases size of epiphyses and bones without epiphyses (short bones) - Growth of cartilage and replacement by bone cease when epiphyses reach their full size - Articular cartilage persists throughout life does not become ossified as epiphyseal plate does BONE GROWTH GROWTH IN BONE WIDTH - Long bones increase in width and other bones increase in size or thickness - Occurs at the periosteum BONE GROWTH FACTORS AFFECTING BONE GROWTH NUTRITION Metabolic disorder that affects cell proliferation, production of collagen and minerals affect bone growth Vitamin D ○ For absorption of calcium from intestines ○ Can be eaten or manufactured in the body ○ Rickets: lack of vitamin D during childhood ○ Osteomalacia: lack of vitamin D during adulthood Vitamin C ○ For collagen synthesis by osteoblasts ○ Scurvy: deficiency of vitamin C ○ Lack of vitamin C causes wounds not to heal, teeth to fall out BONE GROWTH FACTORS AFFECTING BONE GROWTH HORMONES Growth hormone - anterior pituitary ○ General tissue and bone growth ○ Stimulates interstitial cartilage growth and appositional bone growth ○ Dwarfism: insufficient growth hormone secretion ○ Gigantism: excessive growth hormone secretion Thyroid hormone ○ Required for growth of all tissues including cartilage Reproductive hormones ○ Estrogen and testosterone ○ Cause growth at puberty ○ Closure of epiphyseal plates and cessation of growth CALCIUM HOMEOSTASIS Bone is major storage site for calcium Level of calcium in the blood depends upon movement of calcium into or out of bone ○ Calcium enters bone when osteoblasts create new bone ○ Calcium leaves bone when osteoclasts break down bone Hormones control blood calcium levels ○ Parathyroid hormone ○ Calcitriol ○ Calcitonin CALCIUM HOMEOSTASIS PARATHYROID HORMONE - Reduced level of blood calcium stimulates release of PTH CALCIUM HOMEOSTASIS PARATHYROID HORMONE - Reduced level of blood calcium stimulates release of PTH DIRECT EFFECTS (Bone Cells and Kidney Tubules) Activates osteoclasts, increases number of osteoclasts, and prevents inhibition of osteoclast formation Stimulates reabsorption of calcium from urine in the kidney tubules INDIRECT EFFECTS (Small Intestine) Promotes activation of calcitriol, a hormone that increases calcium absorption in the small intestine CALCIUM HOMEOSTASIS CALCITRIOL Increases blood calcium by stimulating intestinal absorption of calcium Derived from vitamin D3 CALCITONIN Lowers blood calcium by inhibiting osteoclast activity CALCIUM HOMEOSTASIS BONE __________ Process wherein old bone replaced with new bone BONE REMODELING Converts woven bone into lamellar bone Involves in bone growth, changes in bone shape, adjustment of bone to stress, bone repair and calcium ion regulation in the body BMU (basic multicellular unit) ○ Group of osteoclasts and osteoblasts that remodel bones ○ Ave life span: 6 months ○ Renews the entire skeleton every 10 years Formation of new osteons in compact bone ○ Osteoclasts enter the osteon from blood in the central canal and internally remove lamellae. Osteoblasts replace bone ○ Osteoclasts remove bone from the exterior and the bone is rebuilt BONE REPAIR III. DISEASES OF THE SKELETAL SYSTEM ABNORMAL SPINAL CURVATURES SCOLIOSIS - Abnormal rotation of the spine resulting in a lateral curvature KYPHOSIS - Dorsally exaggerated thoracic curvature LORDOSIS - Accentuated lumbar curvature BONE DISORDERS RICKETS - Disease in children; epiphyseal plate cannot calcify OSTEOMALACIA - Bones are poorly mineralized - Osteoid is produced but calcium salts are not adequately deposited OSTEOMYELITIS - Bone infection OSTEOPOROSIS - Severe lack of bone density - Bone reabsorption >> bone deposit - Matrix composition is normal but bone mass declines IV. DIAGNOSTIC TESTS FOR SKELETAL SYSTEM DISORDER BONE DISORDERS BLOOD TESTS Serum calcium Alkaline Phosphatase ○ Isoenzyme that indicates enhanced osteoblastic activity ○ Major regulator of bone mineralization ○ Diseases: rickets (markedly elevated) C-telopeptide ○ Marker for bone resorption ○ Used to monitor antiresorptive therapies P1NP (Procollagen type 1 N-terminal Propeptide) ○ Marker for bone formation ○ Monitoring bone formation therapies and antiresorptive therapies BONE DISORDERS BLOOD TESTS Serum 25 hydroxyvitamin D level ○ Disease: rickets (markedly decreased) Serum vitamin C level ○ Not widely available ○ Disease: scurvy (markedly decreased) Formative Assessment 1. What are the main minerals stored in bones? a. Calcium and phosphorus b. Calcium and zinc c. Magnesium and Phosphorus d. Calcium and magnesium Formative Assessment 1. What are the main minerals stored in bones? a. Calcium and phosphorus b. Calcium and zinc c. Magnesium and Phosphorus d. Calcium and magnesium Formative Assessment 2. Which component of the bone imparts flexible strength to the bone matrix? a. Collagen b. Hydroxyapatite c. Proteoglycan d. Elastic fibers Formative Assessment 2. Which component of the bone imparts flexible strength to the bone matrix? a. Collagen b. Hydroxyapatite c. Proteoglycan d. Elastic fibers Formative Assessment 3. Intramembranous ossification is the mode of development in these bones, except : a. Diaphysis of clavicle b. Mandible c. Frontal bones of the skull d. Humerus bone Formative Assessment 3. Intramembranous ossification is the mode of development in these bones, except : a. Diaphysis of clavicle b. Mandible c. Frontal bones of the skull d. Humerus bone Formative Assessment 4. Active bone resorption is a function of which of the following bone cells? a. Osteogenic cells b. Osteoblast c. Osteoclast d. Osteocytes Formative Assessment 4. Active bone resorption is a function of which of the following bone cells? a. Osteogenic cells b. Osteoblast c. Osteoclast d. Osteocytes Formative Assessment 5. Blood calcium levels depend on the movement of this mineral in and out of the bone. Levels of calcium in the blood is controlled by? a. Reproductive hormones b. Growth hormones c. Parathyroid hormone d. Adrenal gland hormones Formative Assessment 5. Blood calcium levels depend on the movement of this mineral in and out of the bone. Levels of calcium in the blood is controlled by? a. Reproductive hormones b. Growth hormones c. Parathyroid hormone d. Adrenal gland hormones References VanPutte, C. L., & Seeley, R. R. (2020). Seeley's anatomy & physiology. (12th ed.). New York, NY: McGraw-Hill