Bones and Skeletal Tissue PDF

Bones and Skeletal Tissue Chapter 6 Prof. Dmitriy Chernov, Anatomy and 1 Physiology 1, Bones and Skeletal Tissue The Skeleton 2 The Skeleton 3  Anterior and Posterior Body Regions Prof. Dmitriy Chernov, Anatomy and Physiology 1,...

Bones and Skeletal Tissue Chapter 6 Prof. Dmitriy Chernov, Anatomy and 1 Physiology 1, Bones and Skeletal Tissue The Skeleton 2 The Skeleton 3  Anterior and Posterior Body Regions Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 4 Directional Terms Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and 5 5 Skeletal Tissue  The Skeleton The skeletal system support and protect all the body structures. Act as a framework for body. made up of joints bones supporting connective tissue. Bones work with muscles to produce movement at the joints. Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 6 Basic Structure, Types, and Locations v Skeletal cartilage: made of highly resilient, molded cartilage tissue that consists primarily of water Contains no blood vessels or nerves v Perichondrium: layer of dense connective tissue surrounding cartilage like a girdle Helps cartilage resist outward expansion Contains blood vessels for nutrient delivery to cartilage v Cartilage is made up of chondrocytes, cells encased in small cavities (lacunae) within jelly-like extracellular matrix Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 7 Basic Structure, Types, and Locations Three types of cartilage: v Elastic cartilage Similar to hyaline cartilage, but contains elastic fibers. Most Flexible Ø External ear and epiglottis v Hyaline cartilage Provides support, flexibility, and resilience ü Most abundant type; contains collagen fibers only Ø Articular (joints), costal (ribs), respiratory (larynx), nasal cartilage (nose tip) v Fibrocartilage Thick collagen fibers: Least Flexible. Has great tensile strength Ø Menisci of knee; vertebral discs 8 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 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 Levers for muscle action 4. Mineral and growth factor storage Calcium and phosphorus, and growth factors reservoir 5. Blood cell formation Ø 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 Ø Osteocalcin secreted by bones helps to regulate insulin secretion, glucose levels, and metabolism Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 9 Classification of Bones 206 bones in human skeleton Divided into two groups based on location v Axial skeleton (80 bones) Long axis of body Skull, vertebral column, rib cage v Appendicular skeleton (126 bones) Bones of upper and lower limbs Girdles attaching limbs to axial skeleton Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 10  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 - patella Vary in size and number in different individuals 3. Flat bones Thin, flat, slightly curved Sternum, scapulae, ribs, most skull bones 4. Irregular bones Complicated shapes Vertebrae and hip bones Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 11 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 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 12 v Compact bone: dense outer layer Compact and spongy bone on every bone that appears smooth and solid v Spongy bone: made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae v Open spaces between trabeculae are filled with red or yellow bone marrow Trabeculae, like cables on a suspension bridge, confer strength to bone contain irregularly arranged lamellae and osteocytes interconnected by canaliculi Capillaries in endosteum supply nutrients Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 13  Structure of Compact Bone Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 14  Bone Structure Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 15 Periosteum and Endosteum Compact bone sandwiched between connective tissue membranes v Periosteum covers outside of compact bone, v Endosteum covers inside of compact bone v Bone marrow is scattered throughout spongy bone; no defined marrow cavity v Hyaline cartilage covers area of bone that is part of a movable joint v Osteogenic stem cells: gives rise to most all bone cells Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 16 Bone Structure v Diaphysis: the long narrow shaft of long bones (yellow marrow) v Epiphyses: ends of long bones that consist of compact bone externally and spongy bone internally v Epiphyseal line is a remnant of childhood epiphyseal plate where bone growth occurs v Medullary cavity: contains yellow bone marrow Ø Red marrow: located in spongy bone Ø Red marrow produces: blood cells platelets most white blood cells arise in red marrow, some in yellow marrow Ø Yellow marrow and mesenchymal stem cells produces: Fat (adipocytes TG-energy) cartilage bone v Articular cartilage covers articular (joint) surfaces 17 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue  The Marrow Hematopoietic tissue in bones v Red marrow is found within trabecular cavities of spongy bone and diploë of flat bones, such as sternum ü In newborns, medullary cavities and all spongy bone contain red marrow ü 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) v Yellow marrow can convert to red, if person becomes anemic Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 18  Sites of muscle, ligament, and tendon attachment on external surfaces Bone Markings Areas involved in joint formation or conduits for blood vessels and nerves Three types of markings: Projection Depression Opening Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 19 Bone Markings Projections Depressions or Holes Head Foramen knoblike end separated from the Hole allows a vessel or a nerve to fissure rest of the bone by a slender pass through or between bones region, the neck Process Sinus Large projection of any bone Cavity or hollow space in bone Condyle Fossa Round prominence at the end of Depression on bone surface bone Shallow basin-like depression Epicondyle (articular surface) Projection near condyle Crest Meatus or Canal Boarder or ridge. Raised or Tube like opening prominent part of the edge of a short channel or passageway, bone external opening of a canal Spine Fissure Sharp Elongate hole or crack Pointed process (for muscle attachment) Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 20  Microscopic Anatomy of Bone 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 21 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue Microscopic Anatomy of Bone 22 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue  Microscopic Anatomy of Bone Osteoblasts v 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 v Osteoblasts are actively mitotic 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 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 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 23 Bone Structure 24 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue Compact bone also called lamellar bone Compact Bone v Consists of: Osteon (Haversian system) Canals and canaliculi Interstitial and circumferential lamellae Perforating (Volkmann’s) canals: canals lined with endosteum that occur at right angles to central canal Connect blood vessels and nerves of periosteum, medullary cavity, and central canal Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 25 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 26  27 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue  Organic and Inorganic matter of the bone Organic components includes: Osteoblasts and osteoclasts osteocytes, collagen fibers which contribute to high tensile strength and flexibility of bone 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 Bone is half as strong as steel in resisting compression (squeezing) and as strong as steel in resisting tension (stretching) Lasts long after death because of mineral composition Can reveal information about ancient people Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 28 Osteogenesis Formation of Bony skeleton 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 New cartilage grows at epiphyseal plates. Ossification replaces cartilage with bone. ü When all cartilage is ossified, bones stop growing. Epiphyseal plate becomes the epiphyseal line. Epiphyseal plate consists of five zones: Bone lengthening ceases 1. Resting (quiescent) zone Females: occurs around 18 y.o. 2. Proliferation (growth) zone Males: occurs around 21 y.o. 3. Hypertrophic zone 4. Calcification zone 5. Ossification (osteogenic) zone Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 29 Formation of Bony Skeleton Up to about week 8, fibrous membranes and hyaline cartilage of fetal skeleton are replaced with bone tissue Endochondral ossification Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 30  Cartilage to bone The human skeleton initially consists of just cartilage, which is replaced by bone, except in areas requiring flexibility Long bones grow lengthwise by interstitial (longitudinal) growth of epiphyseal plate Bones increase thickness through appositional growth NOTE: Bones stop growing during adolescence. Some facial bones continue to grow slowly through life 31 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue Intramembranous Ossification 32 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue Bone Remodeling 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 ü Excesses or deficits of any hormones cause abnormal skeletal growth Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 33  Bone Remodeling v About 5–7% of bone mass is recycled each week Spongy bone replaced ~ every 3-4 years Compact bone replaced ~ every 10 years v 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 Osteoclast activation involves PTH (parathyroid hormone) and immune T cell proteins NOTE: PTH → ⇡ blood calcium Calcitonin → ⇣ blood calcium Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 34  Calcium Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 35 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 36  Control of Remodeling v Remodeling occurs continuously but is regulated by genetic factors and two control loops Ø Hormonal controls Negative feedback loop that controls blood Ca2+ levels ü 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 ü Intestinal absorption of Ca2+ requires vitamin D o Response to mechanical stress o 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 o 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 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 37  Control of Remodeling Other hormones play a role in bone density and turnover v Leptin Hormone released by adipose tissue May play role in bone density regulation by inhibiting osteoblasts v Serotonin Neurotransmitter regulates mood and sleep; also interferes with osteoblast activity Most serotonin made in gut Secreted into blood after a meal ü May inhibit bone turnover after a meal, so bone calcium is locked in when new calcium is flooding into bloodstream Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 38  Homeostatic Imbalance Even minute changes in blood calcium levels can cause severe neuromuscular problems v Hypocalcemia: low levels of calcium cause hyperexcitablility by decreasing the threshold needed for the activation of neurons. As a result, neurons become unstable and fire spontaneous action potentials that trigger the involuntary contraction of the muscles, which eventually leads to tetany. v Hypercalcemia: high levels of calcium cause nonresponsiveness Sustained high blood calcium levels can lead to deposits of calcium salts in blood vessels or kidneys and formation of kidney stones Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 39 Bending Stress and Mechanical Stress Large, bony projections occur where heavy, active muscles attach Weightlifters 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 Mechanical stress causes remodeling by producing electrical signals when bone is deformed Compressed and stretched regions are oppositely charged Compression/tension changes fluid flows within canaliculi, which may also stimulate remodeling Hormonal controls determine whether and when remodeling occurs in response to changing blood calcium levels, but mechanical stress determines where it occurs Fractures and Remodeling Repair involves four major stages: 1. Hematoma formation 2. Fibrocartilaginous callus formation 3. Bony callus formation 4. Bone remodeling Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 41 Types of Bone Fractures Closed fracture—a simple bone fracture with no open wound. Open fracture—a broken bone protrudes through the skin or an external wound leads to a broken bone. Greenstick fracture—one side of the bone is broken and the other is bent; most common in children. Impacted fracture—the broken ends of the bone are jammed into each other. Comminuted fracture—there is more than one fracture line, and the bone is splintered or crushed. Spiral fracture—the bone has been twisted apart; relatively common in skiing accidents. Transverse fracture—the fracture goes straight across the bone. Oblique fracture—the break occurs at an angle across the bone. Prof. Dmitriy Chernov, Ch 9, MusculoSkeletal 42  Classification of Fractures Complete: bone broken, forming separate pieces Incomplete: bone only partially broken Open (compound): skin broken Closed: skin not broken Simple: single break, maintaining alignment and position Comminuted: multiple fractures and bone fragments Compression: bone crushed or collapsed into small pieces Prof. Dmitriy Chernov, Ch 9, MusculoSkeletal 43 Fractures Xray Prof. Dmitriy Chernov, Ch 9, MusculoSkeletal 44  Pathophysiology of Bone Fracture v Fractures initiate an inflammatory response and hemostasis (prevent and stop bleeding) Bleeding from the blood vessels and the periosteum Edema causes stretching of periosteum (if it is intact) and swelling of soft tissues → severe pain. Release of bradykinin and other chemical mediators also contributes to pain. Hematoma forms in medullary canal under the periosteum Necrosis occurs at the ends of the broken bones because of torn blood vessels Clot forms at fracture site. Systemic signs of inflammation may occur. Prof. Dmitriy Chernov, Ch 9, MusculoSkeletal 45  Fracture Repair Blood clot forms around fracture. Blood vessels grow into clot, pulling connective tissue with them. Fibroblasts and chondroblasts convert clot into a soft callus. (collagen and cartilage, respectively) Macrophages remove remains of blood clot, and osteoclasts resorb dead bone tissue. Osteoblasts convert soft callus into a hard callus of spongy bone. Osteoclasts and osteoblasts remodel hard callus into compact bone. Prof. Dmitriy Chernov, Skeletal System 46 Healing of Bone Fracture Hematoma ⇢ granulation ⇢ tissue procallus ⇢ bony callus ⇢ remodeling Hematoma—basis for fibrin (blood clots) network is formed. New capillaries extend into this tissue Phagocytic cells remove debris. Fibroblasts lay down new collagen fibers. Chondroblasts form new cartilage. Formation of procallus (fibrocartilaginous callus – collar) ü This structure is not strong enough – preliminary bridge Osteoblasts generate new bone (spongy) – peri and endosteum Procallus is replaced by bony callus through osteogenic activity This mass of repair tissue is called fibrocartilaginous callus Prof. Dmitriy Chernov, Ch 9, MusculoSkeletal 47 Bone Disorders Estrogen plays a role in bone v Osteomalacia density, so when levels drop at Bones are poorly mineralized menopause, women run higher risk Osteoid is produced, but calcium salts not adequately deposited Men are less prone due to Results in soft, weak bones protection by the effects of Pain upon bearing weight testosterone v 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 v 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 Insufficient exercise to stress bones Diet poor in calcium and protein Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 48 Metabolic Bone Diseases Osteogenesis Paget disease Rickets Imperfecta Defective collagen 49 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue production Osteoporosis Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 50 Developmental Aspects of Bone Embryonic skeleton ossifies predictably, so fetal age is easily determined from X rays or sonograms Most long bones begin ossifying by 8 weeks, with primary ossification centers developed by week 12 Birth to Young Adulthood At birth, most long bones ossified, except at epiphyses Epiphyseal plates persist through childhood and adolescence At ~ age 25, all bones are completely ossified, and skeletal growth ceases Bone density changes over lifetime. Gene for vitamin D’s cellular docking determines mass early in life and osteoporosis risk at old age. Bone mass, mineralization, and healing ability decrease with age beginning in fourth decades except bones of skull. Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue 51  Structural Disorders of Bone Spinal curve abnormalities Ø Kyphosis (hunchback) an exaggeration of the thoracic curve Ø Lordosis (swayback) an excessive lumbar curve Ø Scoliosis - lateral curvature of the vertebral column. May cause compression of internal organs. Occurs in the rapid growth period of the teens, more often in girls than in boys.  Word Anatomy Word Part Meaning Example Bones -clast break An osteoclast breaks down bone in the process of resorption. through, between dia- The diaphysis, or shaft, of a long bone is between the two ends, or epiphyses. Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue oss, osse/o bone, bone tissue Osseous tissue is another name for bone tissue. oste/o bone, bone tissue The periosteum is the fibrous membrane around a bone. Bones of the Axial Skeleton cost/o rib Intercostal spaces are located between the ribs. para- near The paranasal sinuses are near the nose. pariet/o wall The parietal bones are the side walls of the skull. Bones of the Appendicular Skeleton infra- below, inferior The infraspinous fossa is a depression inferior to the spine of the scapula. The metacarpal bones of the palm are near and distal to the carpal bones of meta- near, beyond the wrist. supra- above, superior The supraspinous fossa is a depression superior to the spine of the scapula. 53  Word Anatomy Word Part Meaning Example Disorders of Bone -malacia softening Osteomalacia is a softening of bone tissue. -penia lack of In osteopenia, there is a lack of bone tissue. The Joints ab- away from Abduction is movement away from the midline of the body. toward, added ad- Adduction is movement toward the midline of the body. to on both sides, amphi- An amphiarthrosis is a slightly movable joint. around, double joint, arthr/o A synarthrosis is an immovable joint, such as a suture. articulation circum- around Circumduction is movement around a joint in a circle. 54 Prof. Dmitriy Chernov, Anatomy and Physiology 1, Bones and Skeletal Tissue Prof. Dmitriy Chernov, Anatomy and Physiology 1, LAB, Skeletal Tissue 55 Prof. Dmitriy Chernov, Anatomy and Physiology 1, LAB, Skeletal Tissue 56