A&P 1 Chapter 6
Costal Cartilage
Connects the rib to the sternum (breastbone)
Four Major Steps of Bone Repair
1. Hematoma Forms 2. Fibrocartilageinous Callus Forms 3. Bony Callus Forms 4. Bone Remodeling Occurs
Inorganic Components
65% of bone consists of inorganic hydroxyapatites, or mineral salts, largely calcium phosphates present as tiny, tightly packed, needle-like crystals in and around collagen fibers in the extracellular matrix. Half as srtong as steel in resisting compression and as strong as steel in resisting tension. Last long after death because of mineral composition. It will reveal info about ancient people and it can display growth arrest lines.
Endosteum
A delicate connective tissue membrane that covers internal bone surfaces. Covers trabeculae of spongy bone and line the canal that pass through the compact bone. It contains osteogenic cells that can differentiate into other bone cells.
Diaphysis
A tubular shaft forms long axis. Compact bone surrounded a medullary cavity
Perichondrium
Acts like a girdle to resist outward expansion when the cartilage is compressed. Contains blood vessels from which nutrients diffuse through the matrix to reach the cartilage cells internally
Osteogenic Cells
Also called osteoprogenitor cells, which are mitotically active stem cells found in the membranous periosteum and endosteum. When stimulated, these cells differentiate into osteoblasts or bone lining cells.
Classification of Bone Fractures
Also described by location of fracture External appearance Nature of break
Spongy Bone
Appears poorly organized. Trabeculae in the bone align along lines of stress and help the bone resist stress. Contains irregularly arranged lamella and osteocytes interconnected by canaliculi. No osteons present. Capillaries in the endosteum supply nutrients.
10 years
Compact bone replaced ever?
Bone remodeling occurs
Beginning during bony callus formation and continuing for several months after. The excess material on the diaphysis exterior and within the medullary cavity is removed, and compact bone is laid down to reconstruct the shaft wall. The final structure of the remodeled area resembles the original unbroken bony region becuase its responds to the same set of mechanical stressors.
New Drugs for Osteoporosis Treatment
Bisphosphonates -Decrease Osteoclast activity & number -Partially reverse in spine Selective estrogen receptor modulators -Mimic estrogen without targeting breast and uterus Statins -Cholesterol also increase bone mineral density Denosumab -Monocional antibodies -Reduces fractures in men with prostate cancer -Improve bone density in elderly
Hematoma
Blood vessels in the bone and periosteum, and perhaps in surrounding tissues, are torn and hemorrhage. A mass of clotted blood. Site becomes swollen, painful, and inflamed.
Intramembranous Ossification
Bone develops from fibrous membrane and they form flat bones, clavicle and cranial bones. 8 weeks of development, ossification begins within fibrous connective tissue membranes formed by mesenchymal cells. Ossification centers appear and osteoid is secreted. Woven bone and periosteum form. Lamellar bone replaced woven bone and red marrow appears.
Epiphyses
Bone ends. Bone forms external compact bone and the internal spongy bone. Articular cartilage covers articular surfaces. Between the diaphysis and each epiphysis of an adult lone bone is epiphyseal line. Remnant of childhood bone growth at epiphyseal plate.
Osteoblasts
Bone forming cells that secrete bone matrix. Includes collagen (90% of bone protein) and calcium-binding proteins.
Endochondral Ossification
Bone forms by replacing hyaline cartilage. Froms most all bones inferior to base of skull except clavicles. Begins 2nd month of development. Requires breakdown of hyaline cartilage prior to ossification
Mineral and Growth Factor Storage
Bone is a reservoir for minerals, most importantly calcium and phosphate
Epiphyseal Plate Closure
Bone lengthening ends when the bone of the epiphysis and diaphysis fuses. This happens in females about 18 years of age and males about 21 years of age.
Osteomalacia
Bones poorly mineralized. Calcium salts not adequate. Soft, weak bone. Pain upod bearing weight.
Support
Bones provide a framework that supports the body and cradles its soft organs
Response to Mechanical Stress
Bones reflect stresses they encounter. A bone is loaded (stressed) whenever weight bears down on it or muscles pull on it. Usually off center and tends to bend the bone. Bending compresses the bone on one side and subjects it to tension (stretching) on the other.
Rickets
Bowed legs and other bone deformities. Bones ends enlarged and abnormally long. Causes: Vitamin D deficiency or insufficient dietary calcium.
Immobilization
By cast or traction for healing. Depends on break severity, bone broken, and age of patient.
Perforating (volkmann's) Canal
Canals lined with endosteum at right angles to central canal. It connects blood vessels and nerves of periosteum, medullary cavity, and central canal.
Fibrocartilageinous Callus
Capillaries grow into the hematoma and phagocytic cells invade the area and begin cleaning up the 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. Mass of repair tissue called fibrocartilaginous callus.
Skeletal Cartilage
Cartilage that consists primarily of water, which accounts for its resilience. Contains NO nerves or blood vessels
Appositional Growth
Cells secrete matrix against external face of existing cartilage
Ossification Zone
Chondrocyte deterioration leaves long spicules of calcified cartilage at epiphyseal-diaphysis junction. Osteoclasts partly erode the cartilage spicules, then osteoblasts quickly cover them with new bone. Ultimately spongy bone replaces them.
Interstitial Growth
Chondrocytes divide and secrete new natrix, expanding cartilage from within
Bone Homeostasis: Bone Remodeling
Consists of both bone deposit (osteoblast) and bone resorption (osteoclasts). Occurs at surface of both periosteum and endosteum.
Appendicular Skeleton
Consists of the bones of the upper and lower limbs and the girdles that attach the limbs to the axial skeleton
Articular Cartilage
Covers the ends of most bones at movable joints
Gross Anatomy
Dense outer layer that looks smooth and solid to the naked eye. External layer is compact bone and the spongy bone is a honeycomb of small needle-like or flat pieces called trabeculae
Growth in Length of Long Bones
Depends on the presence of epiphyseal cartilage. Epiphyseal plate maintains constant thickness. Rate of cartilage growth on one side balanced by bone replacement on other. Concurrent remodeling of epiphyseal ends to maintain proportion between diaphysis and epiphyses.
Osteoclasts
Derived from the same hematopoietic stem cells that become macrophages, and are giant, multinucleate cells for the bone resorption. When active, display a ruffled border that increase surface area for enzyme degrading of bone and seals off area from surrounding matrix
Proliferation Zone
Divide pushing the epiphysis side away from diaphysis and lengthening the entire long bone. Cartilage on diaphysis side of the epiphyseal plate.
How Mechanical Stress Causes Remodeling
Electrical signals produced by deforming bone may cause remodeling. Compressed and stretched regions oppositely charged. Fluid flows within canaliculi appear to provide remodeling stimulus.
Paget's Disease
Excessive and haphazard bone deposit and resorption -bone made fasat and poorly--- called pagetic bone ---Very high ratio of spongy to compact bone and reduced mineralization -Usually in spine, pelvis, femur, and skull Rarely occurs before age 40 Cause Unknown- Possible viral Treatment includes calcitonin and biphosphonate
Respiratory Cartilage
Form the skeleton of the larynx (voice box) and reinforce other respiratory passageways
Axial Skelton
Forms the skull, vertebral column, and rib cage (long)
Calcium
Functions include: Nerve impulse transmission, Muscle contraction, Blood coagulation, Secretion by glands and nerve cells, and Cell division. There are 1200-1400 grams of calcium in the body. 99% as bone minerals. Amount in the blood is tightly regulated 9-11mg per dl. It is absorbed from the intestine under the control of vitamin D metabolites
Osteoporosis
Group of diseases. Bone resorption outpaces deposit. Spongy bone of spine and neck of femur most susceptible. Vertebral and hip fractures common
Growth in Width (Appositional)
Growing bones widen as they lengthen. Osteoblasts beneath the periosteum secrete bone matrix on the external bone surface as osteoclasts on the endosteal surface of the diaphysis remove bone. Usually more building up than breaking down. It produces thicker, stronger bone but not too heavy. Occurs throughout life.
Canaliculi
Hairlike canals that connect lacunae to each other and to the central canal
Results of hormonal and Mechanical Influences
Hormonal controls determine whether and when remodeling occurs to changing blood calcium levels. Mechanical stress determines where remodeling occurs.
Leptin
Hormone released by adipose tissue. Role in bone density regulation. Inhibits osteoblasts in animals.
Compound (Whether the bone ends penetrate the skin)
If fracture is open
Complete Fracture (Completeness of the break)
If the bone is broken through
Incomplete Fracture (Completeness of the break)
If the bone is not broken though
Simple Fracture
If the fracture is closed
Organic Components
Include cells and osteoid. Osteoid makes up 1/3 of the matrix, includes ground substances and collagen fibers, both of which are secreted by osteoblasts. They contribute both to a bone's structure and to the flexibility and tensile strength that allow it to resist stretch and twisting. Resilience of bone due to sacrificial bonds in or between collagen molecules. Stretch and break easily on impact to dissipate energy and prevent fracture. If no additional trauma, bonds re-form.
Bone Resorption
Is function of osteoclasts. Digging depressions or grooves as they break down the bone matrix. Secrete lysosomal enzymes that digest matrix and protons. Acidity converts calcium salts to soluble forms. Osteoclasts may also phagocytize the demineralized matrix and dead osteocytes. Transytosis allow release into interstitial fluid and then into blood. When resorption of a given area bone is completed, the osteoclasts undergo apoptosis. Osteoclasts activation involves PTH and proteins secreted by T cells of the immune system.
Red Marrow
It is found within trabecular cavities of spongy bone and dipoë of flat bones. In medullary cavities and spongy bone of newborns. Occurs only in the heads of the femur and humerus. Yellow marrow can convert to red if necessary
Results of Mechanical Stressors
Long bones are thickest midway along the diaphysis, exactly where the bending stresses are greatest. Handedness: Right or Left hand Curved bones thickest where most likely to buckle Trabeculae form trusses along lines of stress Largely, bone projections occur where heavy, active muscles attach Bones of fetus and bedridden are featureless.
Postnatal Bone Growth
Long bones lengthen entirely by interstitial growth of the epiphyseal plate cartilage and its replacement by bone, and all bones grow in thickness by appositional growth.
Osteocytes
Mature bone cells in lucunae. They monitor and maintain bone matrix and also acts as stress or strain "sensors" and respond to mechanical stimuli to osteoblasts and osteoclasts so bone remodeling can occur.
Calcium Homeostasis
Minute changes from the homeostatic range for blood calcium can lead to severe neuromuscular problems. Hyper-excitability (levels too low) and non-responsiveness (Levels too high).
Hormonal Regulation of Bone Growth (Thyroid Hormone)
Modulates activity of growth hormone. Ensures proper proportions
Blood Cell Formation
Most blood cell formation, or hematopoiesis, occurs in the red marrow cavities of certain bones.
Hormonal Regulation of Bone Growth (Growth Hormone)
Most important in stimulating epiphyseal plate activity in infancy and childhood.
Hyaline cartilage
Provides support with flexibility and resilience. They are the most abundant skeletal cartilage and the only fiber type in their matrix is fine collagen fibers.
Risk Factors for Osteoporosis
Most often aged, postmenopausal women. 30% 60-70 years of age: 70% by age 80. 30% caucasian women will fracture bone because of it. Men lesser degree. Sex hormones maintain normal bone health and density. As secretion wanes with age osteoporosis can develop.
Growth in Length of Long Bones
Near end of adolescence chondroblasts divide less often and plate thins until entire epiphyseal plate is replaced by bone tissue.
Serotonin
Neurotransmitter regulating mood and sleep. Most made in gut. Secreted into blood after eating. Interfere with osteoblast activity. When we eat, ____ is secreted and circulated via the blood to the bones where it interferes with osteoblast activity.
Calcification of Cartilage
Occurs during normal bone growth (youth and old age) that hardens, but calcified cartilage is not bone
Bone Homeostasis
Older bone becomes more brittle. Calcium salts crystallize. Fractures more easily.
Hypertrophic Zone
Older chondrocytes closer to diaphysis and their lacunae enlarge and erods, leaving large interconnecting spaces.
Canaliculi Formation
Osteoblasts secreting bone matrix surround blood vessels and maintain contact with one another and local osteocytes by tentacle-like projections containing gap junctions. Matrix hardens and the maturing cells become trapped within it
Additional Risk Factors for Osteoporosis
Petite body form. Insufficient exercise to stress bones. Diet poor in calcium and protein. Smoking. Hormone-related conditions -Hyperthyroidism -Low blood levels of thyroid-stimulating hormone -Diabetes mellitus Immobility Males with prostate cancer taking androgen-suppressing drugs
Preventing Osteoporosis
Plenty of calcium in diet in early adulthood Reduce carbonated beverage and alcohol consumption -Leaches minerals from bone so decreases bone density Plenty of weight-bearing exercise -Increases bone mass above normal for buffer against age-related bone loss
Ossification (Osteogenesis)
Process of bone tissue formation and the formation of bony skeleton. It goes on until early adulthood as the body increases in size. Begins 2nd month of development. Bone repair and remodeling.
Hormone Production
Produce osteocalcin, a hormone that helps to regulate insulin secretion, glucose homeostasis, and energy expenditure
Calcitonin (Hormonal Control of Blood Ca2+)
Produced by parafollicular cells of thyroid glands may be involved.
Parathyroid Hormone (Hormonal Control of Blood Ca2+)
Produced by parathyroid glands. Removes calcium from bone regardless of bone integrity (Osteoclasts)
Hormonal Regulation of Bone Growth (Testosterone in males and Estrogen in female)
Promote the growth spurt typical of adolescence. Also end growth by inducing epiphyseal plate closure.
Reduction
Realignment of broke bone ends. Closed reduction-Physician manipulates to correct position Open Reduction- Surgical pins or wires secure ends
5-7%
Recycle ___ of bone mass each week.
Resting Zone
Relatively inactive on the side of the epiphyseal plate facing the epiphysis.
Control of Remodeling
Remodeling goes on continuously in the skeleton, regulated by genetic factors and two control loops. Negative feedback hormonal loop that maintains Ca2+ homeostasis. Controls blood Ca2+ levels (Not bone density). Responses to mechanical and gravitational forces--weight bearing exercise.
Elastic Cartilages
Resembles hyaline cartilage but they contain more stretchy elastic fibers and so are better able to stand up to repeated bending. (external ear and the epiglottis)
Central (haversian) Canal
Runs through the core of the osteon and it contains blood vessels and nerve fibers
Periosteum
Sharpey's fiber tufts of collagen fibers that extend from its fibrous layer into the bone matrix--Secure the underlying bone. Also provides anchoring points for tendons and ligaments
Lacunae
Small cavities that contains osteocytes
Triglycerides
Source of energy in the body is stored in bone cavities
3-4 years
Spongy bone replaced every?
Nasal Cartilages
Support the external nose
Calcification Zone
Surrounding cartilage matrix calcifies and these chondrocytes die and deteriorate
Hypercalcemia
Sustained high blood calcium levels. Deposits of calcium salts in blood vessels. (Kidney Stones)
Axial and Appendicular
The 206 named bones of the human skeleton are divided into two groups called
Displaced Fractures (Position of the bone ends after fracture)
The bone ends are out of normal alignment.
Nondisplaced Fractures (Position of the bone ends after fracture)
The bone ends retain their normal position
Protection
The fused bones of the skull protect the brain. Brain, spinal cord, and vital organs
Osteon
The structural unit of compact bone. Elongated cylinder parallel to long axis of bone. Hollow tubes of bone matrix called lumellae. Collagen fibers in adjacent rings run in different directions that withstand stress-resist twisting.
Osteogenic Cells, Osteoblasts, Osteoclasts, Osteocytes, Bone Lining Cells
There are five cell types of bone tissue
Resting Zone, Proliferation Zone, Hypertrophic Zone, Calcification Zone, and Ossification Zone
There are five zones within cartilage
Gross Anatomy, Microscopic, and Chemical
There are three bone structures
Fibrocartilage
Thick collagen fibers which has great tensile strength. (menisci of the knee and the disc between vertebrae)
Structure of Short, Irregular, and Flat bones
Thin plates of spongy bone covered by compact bone. The compact bone is convered outside (periosteum) and inside (endosteum)by connective tissue membranes. They have no shape or expanded ends. They contain bone marrow but no well-defined marrow cavity. Hyaline cartilage covers their surface
Hyaline cartilage, Elastic cartilage, anad Fibrocartilage
Three types of cartilage
Treating Osteoporosis
Traditional treatments -Calcium -Vitamin D Supplements -Weight-bearing exercise -Hormone replacement therapy Slows bone loss but does not reserve it Controversial due to increased risk of heart-attack, stroke, and breast cancer Some take estrogenic compounds in soy as substitute
Movement (Anchorage)
Use bones as levers to move the body and its parts
Periosteum
White, double-layered membrane that covers external surfaces except joint surfaces. The outer fibrous layer is dense irregular connective tissue. Consists primarily of primitive stem cells, Osteogenic cells. Richly supplied with nerve fibers and blood vessels.
Bony Callus Forms
Within a week, new bone trabeculae appear in the fibrocartilaginous callus and gradually convert it to a bony (hard) callus of spongy bone. Firm union forms about two months later.