Anatomy & Physiology Ch.7 Bone
collagen fibers
"corkscrew" down the matrix of the lamella giving it a helical arrangement; helices coil in one direction in one lamella and in the opposite direction in the next lamella for added strength
Suffixes of cell types
-Blasts: immature but metabolically active cells -Cytes: Less active cells that typically occupy the matrix of mature connective tissues -Clasts: Type of cell involved in remodeling or breakdown of matrix
4 stages of healing a fracture
1. formation of hematoma & granulation tissue 2. Soft callus formation 3. Hard callus formation 4. remodeling of bone
Composite
A combination of 2 basic structural materials. In bone it is a ceramic and a polymer. The polymer is collagen and the ceramic is hydroxyapatite and other minerals. The ceramic components enables a bone to support the weight of the body without sagging. The polymer protein part give the bone some degree of flexibility.
hypocalcemia
A deficiency in calcium in the blood and causes excessive excitability of the nervous system and leads to muscle tremors, spasms or tetany. When there is little calcium, the cell membrane becomes more permeable to sodium and the Na+channels are opened and activated allowing Na+ to enter the cell. this increases depolarization and the cell becomes very excitable
calcitriol
A hormone produced from vitamin D that acts to increase calcium levels in the blood. It does this by: -increasing reabsorption of calcium from small intestine -increasing reabsorption from the skeleton by promoting production of osteoclasts that breakdown bone -promotes the reabsorption of calcium ions by the kidneys to prevent loss in urine.
long bones
A type of bone that is longer than it is wide; serve as levers; Shaft is called the diaphysis and the ends are knows as epiphysis; Examples include the Humerus, Radius, Ulna, Femur, Fibula and Tibia
resorption bays
AKA Howship lacunae; pits on surface of bone where osteoclasts reside
Mineral deposition
AKA mineralization is a crystallization process where calcium, phosphate and other ions are taken from the blood plasma and deposited in bone tissue, mainly as crystals of hydroxyapatite. deposition begins in fetal ossification and continues throughout life.
matrix of osseous tissue
About ⅓ organic and ⅔ inorganic matter. Organic is made by osteoblast and include collagen, glycosaminolglycans, glycoproteins etc. Inorganic include hydroxyapatite, calcium carbonate, sulfate etc. Minerals and collagen form a composite two phase substance (like fiberglass or reinforced concrete) giving it both flexibility and strength. Collagen is what gives bones their flexibility, so they can bend slightly without snapping. Hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂ is the major inorganic matter found in bones and it along with minerals give bones their strength and allow them to resist compression.
Bone Cells
Bone consists of cells, fibers and ground substance. There are 4 main types of bone cells: 1. Osteogenic (osteoprogenitor) cells; 2. Osteoblasts; 3. Osteocytes; 4.Osteoclasts
orthopedics
Branch of medicine treating disorders of the skeletal system and tissues related to movement (muscles, joints)
osteogenesis imperfecta
Brittle bone disease. Result when the bone is excessively brittle b/c of little protein (the polymer component of ceramic)
achondroplastic dwarfism
Congenital skeletal malformation caused by a genetic disorder in converting cartilage to bone.
osteogenic cell
Develop from embryonic mesenchymal cells and found in the endosteum (inner layer of periosteum) and in the central canals; an unspecialized stem cell that is the only bone cell that can undergo cell division; Can develop into osteoblasts.
rickets
Disease due to vitamin D deficiency characterized by deficient calcification and soft bones associated with skeletal deformities. Bone is deficient in calcium salts (the ceramic part of the composite). As a result the soft bones of lower limb bend under the body's weight and become permanently deformed.
flat bones
Enclose and protect soft organs and provide broad surfaces for muscle attachment; thin, flattened, and usually curved, two thin layers of compact sandwiching spongey bone (skull, ribs, sternum)
secondary marrow cavity
Endochondral ossification Picture 1: Bone at birth Picture 2: Bone of child Picture 3: Bone of adult
interstitial lamellae
Found between osteons and are remains of old osteons that broke down as bone grew and remodeled itself
compact bone
Hard, dense bone tissue that is beneath the periosteum (outer membrane of a bone)
osteoporosis
Most common bone disease. abnormal loss of bone density resulting in fragile porous bones attributable to a lack of calcium
short bones
Nearly equal in length and width; cube-shaped, contain mostly spongey bone (bones of wrist and ankles- sesamoid)
Formation of bone
Ossification or osteogenesis. In the human fetus and infant, bone develops by 2 methods called intramembranous and endochondral ossification
parathyroid hormone
PTH synthesized and released into the blood stream by the parathyroid glands and used to increase calcium levels in the blood. Does this by: -bind to osteoblasts that release RANKL which promotes production of osteoclasts that breakdown bone -promote calcium reabsorption by the kidneys so less clcium is lost in the urine -increase effects of calcitrol -inhibit collagen synthesis by osteoblasts which inhibits bone deposition
PTH
Parathyroid hormone; secreted by the parathyroid gland; PTH regulates uptake of calcium (Ca) from the bones into the blood; PTH also causes excess phosphorous (P) to be shed from the kidney
intramembranous ossification
Produces the flat bones of the skull and most of the clavicle. Method of bone formation in which the bone is formed directly in a membrane 1. Some of the embryonic connective tissue (mesenchyme) condenses into a layer of soft tissue permeated with blood capillaries. Mesenchymal cells differentiate into osteogenic cells. 2. Osteogenic cells gather and differentiate into osteoblasts and deposit osteoid tissue. Some osteoblasts get trapped in matrix as calcium phosphate is added and become osteocytes. 3.Osteblasts continue to deposit minerals producing bony trabeculae. 4. Trabeculae at the surface continue to calcify converting spongy to compact bone
closed reduction
Realignment of broken bone ends WITHOUT surgery
where is hemopoietic tissue found in adults?
Red marrow found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur of adults
Zones of the metaphysis
Show how cartilage is converted to bone allowing us to grow in length. Has 5 zones starting from farthest to marrow cavity 1.zone of reserve cartilage, 2.zone of cell proliferation, 3.zone of cell hypertrophy, 4.zone of calcification, 5.zone of bone deposition
Effects of Stress and Fracture on bone cells
Stress and fractures stimulate osteogenic cells to multiply more rapidly and quickly generate increased numbers of osteoblasts, which reinforce or rebuild the bone
osteocyte
These are osteoblasts that become trapped in the matrix they deposit [osteogenic->osteoblast-> osteocyte]. Osteocyte reside in lacunae which are interconnected by slender channels called canaliculi. Function: -homeostasis of bone density and blood concentration of calcium and phosphate ions by reabsorbing or depositing bone matrix -Strain stressors to regulate bone remodeling-adjustments in bone shape and density to adapt to stress. mature bone cell
ruffled border
Where the plasma membrane of osteoclasts contacts bone matrix, it forms many projections that increase surface area and enhance efficiency of bone resorption
stress fracture
a break caused by abnormal trauma to a bone
periosteum
a fibrous, vascular membrane that covers the bone
osseous tissue
a hard connective tissue containing an abundant mineralized extracellular matrix that surrounds widely separated cells
calculus
a hard lump produced by the concretion of mineral salts in an otherwise soft organ such as the lungs.
articular cartilage
a layer of hyaline cartilage that covers the joint surface where one bone meets another bone (epiphyses of bones in synovial joints) allows joint to move more freely and relatively friction free
fracture hematoma
a mass of clotted blood that forms around the site of a bone fracture within 48 hours after the injury
ectopic ossification
abnormal calcification; Bone formation eyes, brain, arteries, muscles, tendons, lungs. ex.arteriosclerosis- hardening of arteries due to calcification of arterial walls
kyphosis
an abnormal backward curve to the vertebral column
Wolff's law of bone
architecture of bone determined by mechanical stresses placed on it and bones adapt to withstand those stresses
epiphyseal plate (growth plate)
area of hyaline cartilage that separates the marrow spaces of the epiphysis and diaphysis; enables growth in length; found in children and adolescents; It is a region of transition from cartilage to bone and functions as a growth zone where the bones elongate. Growth here is responsible for a persons increase in height.
other factors affecting bone
at least 20 or more hormones, vitamins, and growth factors affect osseous tissue bone growth especially rapid in puberty and adolescence. Surges of growth hormone, estrogen, and testosterone occur and promote ossification; these hormones stimulate multiplication of osteogenic cells, matrix deposition by osteoblasts, and chondrocyte multiplication and hypertrophy in metaphyses girls grow faster than boys and reach full height earlier estrogen stronger effect than testosterone on bone growth; males grow for a longer time and taller anabolic steroids cause growth to stop, epiphyseal plate "closes" prematurely & results in abnormally short adult stature
osteoblast
bone forming cell; non mitotic so they are only created by differentiation of osteoprogenitor( osteogenic) cells. they form the soft matter of the bone matrix which can harden through mineral deposition. Also secrete osteocalcin (hormone) that stimulates insulin secretion by the pancreas etc
6 components of bone
bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue
irregular bones
bones that have complex shapes with short, flat, notched or ridged surfaces; examples are vertebrae that form the spinal column and several bones in the skull (sphenoid, ethmoid)
calcium homeostasis (1)
calcium and phosphate are used for much more than bone structure. minerals are deposited in the skeleton and withdrawn when they are needed for other purposes; depends on a balance btwn dietary intake, urinary and fecal loses, and exchanges btwn osseous tissue: phosphate is a component of DNA, RNA, ATP, phospholipids, and pH buffers; calcium needed in neuron communication, muscle contraction, blood clotting, and exocytosis; minerals are deposited in the skeleton and withdrawn when they are needed for other purposes; about 1100g of calcium in adult body - 99% in the skeleton as easily exchangeable calcium ions and more stable hydroxyapatite reserve; 18% of calcium in adult skeleton exchanged with blood each year; normal calcium concentration in blood plasma is normally 9.2 to 10.4 mg/dl - 45% as Ca2+ can diffuse across capillary walls and affect other tissues - rest in reserve, bound to plasma proteins
calcium homeostasis
calcium homeostasis depends on a balance between dietary intake, urinary and fecal loss and exchange with osseous tissue. it is regulated by 3 hormones: Parathyroid Hormone/Calcitriol raise levels; Calcitonin oppose PTH and Calcitriol
chondro
cartilage
interstitial growth
cartilage/bone that grows from within itself, causes bones to lengthen and allows us to grow tall
osteoclast
cell that functions in the breakdown and resorption of bone tissue; come from different cell line that gives rise to blood cells and are formed by the fusion of several stem cells
zone of cell hypertrophy
chondrocyte stop dividing and enlarge; matrix between lacunae become very thin
zone of bone deposition
chondrocytes die, longitudinal columns fill with osteoblasts and blood vessels, osteoclasts dissolve the calcified cartilage osteons and spongy bone; are created by osteoblasts
zone of cell proliferation
chondrocytes multiply forming columns of flat lacunae
pituitary dwarfism
condition of congenital hyposecretion of growth hormone slowing growth and causing short yet proportionate stature (not affecting intelligence), often treated during childhood with growth hormone; other forms of dwarfism are most often caused by gene defects
canaliculi
connect the lacunae to each other and the central canal. Each osteocyte has tiny fingerlike projections that reach into the canaliculi to contact the processes from neighboring osteocytes
interaction of skeletal system with rest of body
continually remodels itself and interacts physiologically with all of the other organ systems of the body permeated with nerves and blood vessels, which attests to its sensitivity and metabolic activity
spongy (cancellous) bone
covered by more durable compact bone; skeleton about three-fourths compact and one-fourth spongy bone by weight; spongy bone found in ends of long bones, and the middle of nearly all others
diaphysis (shaft)
cylinder of compact bone to provide leverage. The shaft of bone
Fosamax/Actonel
drugs that destroy osteoclasts favored over ERT(estrogen replacement) bc ERT increases risk for stroke, breast cancer and coronary artery disease
bone remodeling
dynamic tissue undergoing constant remodeling due to internal and external forces, weight bearing and muscle contraction encourages stronger bone, limited or non-weight bearing and bed rest decrease bone strength
epiphyses
enlarged ends of a long bone; enlarged to strengthen joint and provide added surface area for the attachment of ligaments and tendons
periosteum
external vascular sheath that covers bone except where there is articular cartilage and provides strong attachment and continuity from muscle to tendon to bone
secondary ossification center
formation of secondary ossification center: all the same of primary except spongy bone is kept in the center and no medullary cavity forms in endochondrial ossification
primary marrow cavity
forms from blood and stem cells filling hollow cavity in endochondrial ossification
yellow marrow
found in adults; most red marrow turns into fatty yellow marrow; no longer produces blood but can transform back into red marrow in the event of severe or chronic anemia
mesenchymal cell
from mesoderm; become muscle, bone, adipose&cartilage
bone marrow
general term for soft tissue that occupies the marrow cavity of a long bone and small spaces amid the trabeculae of spongy bone. 2 types: yellow and red
Forteo
generic= teriparatide; osteoporosis, {parathyroid hormone to help reduce bone density loss}
appositional growth
growth at the outer surface of a bone during endochondral ossification, resulting in an increase in the bone's thickness, causes bone to widen and thicken
epiphyseal line
in adults, a bony scar that marks where growth plate used to be
cytoplasmic processes
in canaliculi- facilitate nutrient transfer from cell to cell, has gap junctions with each other
estrogen replacement therapy
in pre meno women, estrogen naturally maintains bone density by inhibiting osteoclasts. regimen often recommended to menopausal women by physicians to slow bone loss
marrow cavity
is a hollow, cylindrical space within the diaphysis that contain fatty yellow bone marrow in adults.
soft callus formation
is the second stage of bone repair. The cartilage fills in the space between the bones, and blood vessels begin to grow into the area.
red bone marrow
located within the spongy bone, is hemopoietic tissue that manufactures red blood cells, hemoglobin, white blood cells, and thrombocytes
a mature bone remains a _____________________ organ
metabolically active involved in its own maintenance of growth and remodeling
zone of calcification
mineral deposited in the matrix between columns of lacunae; temporary support for cartilage
red marrow
myeloid tissue or red bone marrow is found in nearly every bone in a child
diploe
name for the layer of spongy bone sandwiched between compact bone layers in flat bones
granulation tissue
new connective tissue and tiny blood vessels that form around a fracture during the healing process
circumferential lamellae
not all of the matrix is organized into osteons (concentric lamellae). The inner and outer boundaries of dense bone are arranged in circumferential lamellae that runs parallel to bone surface;
perichondrium
occurs in endochondral ossification (around the cartilage) acts like a girdle to resist outward expansion when the cartilage is compressed. Contains blood vessels from which nutrients diffuse through matrix to reach the cartilage cells
nutrient foramina
on the surface of bone tissue that allow blood vessels and nerves to enter the bone; open into the perforating canals that cross the matrix and feed into the central canals; innermost osteocytes near central canal receive nutrients and pass them along through their gap junction to neighboring osteocytes; they also receive wastes from their neighbors and transfer them to the central canal maintaining a two-way flow of nutrients and waste
Concentric lamellae
onion like layers of matrix of compact bone that are arranged around a central (haversian/osteonic) canal and connected with each other by canaliculi
open reduction
open surgery to set fractured bones using pins, plates and screws
skeletal system
organ system that provides protection and support for body parts and is made of bones, cartilage, ligaments joined together to form a framework for the body.
perforating (Sharpey's) fibers
other outer fibers of the periosteum that penetrate into the bone matrix allowing for continuity between tendon, bone and muscle
compact (dense) bone
outer shell of long bone
inner osteogenic layer of bone forming cells
part of the periosteum; important to growth of bone and healing of fractures
phosphate homeostasis
phosphate levels are not as closely regulated as calcium. Calcitriol raises phosphate levels by promoting its absorption from the diet in the small intestine. Vitamin D causes reabsorption of phosphorus in the intestines. PTH causes excretion of phosphate from the kidneys. Excess vitamin D causes high phosphate and Ca levels Excess PTH causes low phosphate and high Ca
hemopoietic tissue
produces blood cells and is composed of multiple tissues in a delicate, but intricate arrangement that is an organ to itself
primary ossification center
region of formation of long bone begins in center of hyaline cartilage shaft in endochondrial ossification
blood flow in compact bone
skeleton receives about half a liter of blood per minute. Blood vessels along with nerves enter the bone tissue through nutrient foramina on the bone surface.
spicules
slivers of spongy bone
lacunae
small cavities in bone that contain osteocytes
outer fibrous layer of collagen (periosteum)
some outer fibers continuous with the tendons that attach muscle to bone; strong attachment and continuity from muscle to tendon to bone
medullary cavity (marrow cavity)
space in the diaphysis of a long bone that contains bone marrow
spongy bone
spongy bone consists of spicules (slivers of bone in rod or spine shapes), tribeculae, red bone marrow. Although calcified and hard it is named for its sponge like appearance. It is permeated with spaces filled with bone marrow and arranged in lamellae. -Has few osteons and no central canals. all osteocytes close to bone marrow. mesh-like bone tissue containing marrow and fine branching canals through which blood vessels run -provides strength with minimal weight trabeculae develop along bone's lines of stress
6 functions of skeleton
support - hold the body up, supports muscles, mandible and maxilla support teeth protection - brain, spinal cord, heart, lungs movement - limb movements, breathing, action of muscle on bone electrolyte balance - skeleton stores calcium and phosphate ions and releases them when needed acid-base balance - buffers blood against excessive pH changes by absorbing or releasing alkaline salts such as Calcium phosphate blood formation - red bone marrow is the chief producer of blood cells
osteon (haversian system)
the basic structural unit of compact bone formed by a central canal and its concentric lamella; connected to each other by canaliculi; a cylinder of tissue around a central canal
metaphysis
the growing part of a long bone between the diaphysis and the epiphysis
Tetany
the inability of the muscle to relax. Happens when plasma Ca2+ concentration falls to 6mg/dL.
calcium and phosphate
the major minerals that are used in bones homeostasis.
fracture
the manner in which a mineral breaks along either curved or irregular surfaces
endochondral ossification
the most common bone formation process, which involves the replacement of hyaline cartilage (developed by mesenchyme) with bone. Begins around 6th week to age 20. 1.mesenchyme develops into hyaline cartilage sovered by fibrous perichondrium that produces chondrocytes. 2. perichondrium stops making chondrocytes and begins making osteoblasts. A primary ossification center is made in the middle of the bone by chondrocytes and turns into a cavity. 3. Blood vessels invade the primary ossification center and it becomes the primary marrow cavity. blood vessels introduce osteoblasts and osteoclasts. Osteoblasts begin depositing oteoid tissue. At the epiphysis a secondary ossification center is formed 4. Second ossification center becomes hollowed and a 2nd marrow cavity forms in the epiphysis 5. in infancy and childhood, the epiphysis fills with spongy bone and cartilage is limited to articular cartilage and epiphyseal plate, which serves a s a growth zone for bone elongation. 6. by late teens early 20's all remaining cartilage in epiphyseal plate is consumed and the gap between epiphysis and diaphysis closes. bone can no longer grow
hypercalcemia
the presence of abnormally high levels of calcium in the blood. When there is too much calcium in the blood/outside the cell, that keeps Na+ gates closed and Na+ cannot enter the cell. this prevents depolarization and the cell is less excitable.
mineralization
the process in which organic material is changed into inorganic material such as a fossil or bone
mineral resorption
the process of dissolving bone and releasing minerals into the blood performed by osteoclasts at the "ruffled border"; hydrogen pumps in membrane secrete hydrogen into space between the osteoclast and bone surface; chloride ions follow by electrical attraction; hydrochloric acid (pH 4) dissolves bone minerals acid phosphatase enzyme digests the collagen
calcification
the process where mineral salts are deposited in the collagen fiber framework, hardening the bone matrix
osteology
the study of the bones and the disorders and diseases of the skeletal system
endosteum
thin layer of reticular connective tissue lining marrow cavity; has cells that dissolve osseous tissue and others that deposit it
trabeculae
thin plates of spongy bone that develop along a bone's lines of stress
calcitonin
thyroid hormone that tends to lower the level of calcium in the blood plasma and inhibit resorption of bone. It does this by: -inhibiting osteoclasts so they stop breaking bone down and releasing Ca2+ into the blood -Stimulate osteoblasts which take calcium from blood and put in the skeleton
ligaments
tissue that connects bone to bone at joints
tendons
tough connective tissue that joins skeletal muscles to bones
cartilage
tough, flexible tissue that covers the ends of bones and decreases friction; chondro; not vascular; forerunner of most bones
perforating (Volkmann) canals
transverse or diagonal passages along the length of the osteon that connect different central canals in compact bone.
pathological fracture
type of fracture that occurs because of weakened or diseased bone
zone of reserve cartilage
typical hyaline cartilage farthest from marrow cavity; shows no sign of transforming into bone
