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.