Chapter 7 Test review

Functions of the skeletal system

Support, Protection, Movement, electrolyte balance, acid-base balance, blood formation

Support

holds up the body, supports muscles, mandible and maxilla support teeth

protection

brain, spinal cord, heart, lungs

Movement

limb movements, breathing, action of muschle on bone

electrolyte balance

calcium and phosohate ions

Acid-Base balance

buffers against excessive pH changes

Blood Formation

Red bone marrow is the chief producer of blood cells

Flat Bones

protect soft organs, curved but wide and thin

Long bones

longer than wide, rigid levers acted upon by muscles

Short bones

equal in length and width, glide across one another in multpile directions

irregular bones

elaborate shapes that do not fit into other categories

Compact (dense) bone

outer shell of long bone

Diaphysis (shaft)

cylinder of compact bone to provide leverage

medullary cavity

space in the diaphysis of a long bone that contains bone marrow

epiphysis

enlarged ends of a long bone
enlarged to strengthen join and attach ligaments and tendons

spongy (cancellous) bone

covered by more durable compact bone. skeleton three-fourths compact and one-fourth spongy bone by weight

articular cartilage

layer of hyaline cartilage that cover the joint surface where one bone meets another; allows joint to move more freeely and realtively friction free

Nutrient formina

minute holes in the bone surface that allows blood vessels to penetrate

Periosteum

external sheath that covers bone except where there is articular cartilage

Outer layer of Periosteum

fibrous layer of collagen. some outer fibers continuous with the tendons that attach muscles to bone, perforating fibers, strong attachment and continuity from muscle to tendon to bone

Inner layer of Periosteum

inner osteogenic layer of bone forming cells, important to growth of bone and healing of fractures

Osteogenic (osteoprogenitor) cells

stem cells found in endosteum, periosteum, and in central canals.
-arise from embyonic

Osteoblast

bone-forming cells
-line up as asingle layer of cells under endosteum and periosteum
-nonmitotic
-synthesize soft organic matter of matrix which then hardens by mineral deposition
-stress and fractures stimulate osteogenic cells to multiply more rapidly a

Osteocalcin

structural protien of the bone
stimulates insulin secretion of pancrease
increases insulin sensitivity in adipocytes which limit the growth of adipose tissue

Osteocytes

former osteoblast that have become trapped in the matrix they have deposited
-some osteocytes reabsorb bone matrix while other deposit it
-contribute to homeostatic mechanism of bone density and calcium and phosphate ions

Lacunae

tiny cavities where osteocytes reside

canaliculi

little channels that connect lacunae

osteoclast

bone-dissolving cells found on the bone surface
-develop from same bone marrow stem cells that give rise to bloood cells
-different origin from rest of bone cells
-unusually large cells fromed from the fusion of severla stem cells
- Typically have 3 to 4

Ruffled border

side facing bone surface
-several deep infoldings of the plasma membrane which increases surface area and resorption efficiency

Resorption bays

pits on surface of bone where osteoclasts reside

remodeling

results from combined action of the bone-dissolving osteoclasts and the bone-deposting osteoblasts

Matrix

by dry weight 1/3 organic and two thirds inorganic matter

Organic matter of Matrix of Osseous tissue

collagen, carbohydrate-protien complexes, such as glycosaminoglycans, proteoglycans, and glycoprotiens

Inorganinc matter of Matrix of osseous tissue

85% dydroxyapatite, 10% cacium carbonate, other minerals (flouride, sodium, potassium, magnesium)

Bone is a composite

combination of two basic structural materials, a combination of two basic structural materials, a cermaic and a polymer.
-combines optimal mechanical properties of each component
-bone combines the polymer, collagen, with cermic, hydroxyapatite and other

Rickets

soft bones due to deficiency of calcium salts

Osteogenesis imperfecta/ brittle bone disease

excessively brittle bones due to lack of protien, collagen

Spongy bone

-spongy like appearance

Spongy bone

slivers of bone called spicules, thin plates of bone called trabeculae, spaces filled with red bone marrow

Spongy bone

few osteons and no central canals, all osteocytes close to bone marrow

Spongy bone

gives strength with minimal weight
-trabeculae develop along bones lines of stress

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

Red marrow (myeloid tissue)

in nearly every bone in a child, hemopoietic tissue, in adults, found in skull, vertebrae, ribs, sternum, part of pelvic griddle, and proximal heads of humerus and femur

Yellow Marrow

-most red marrow turns into fatty yellow marrow
-no longer produces blood
-found in older adults and infants

Ossification or osteogenesis

the formation of bone

fetus and infant bone

intramembraneous ossification, endochondral ossification

Intramembranous ossification steps

1. condensation of mesenchyme into soft sheet permeated with blood capillaries
2. depostion of osteiod tissue by osteoblasts on mesenchymal surface; entrapement of first osteocytes; formation of periosteum
3. honeycomb of bony trabeculae formed by continu

Endochondral Ossification steps

1. Early cartilage model
2. Formation of primary ossification center, bony collar, and perioseteum.
3. Vascular invasion, formulation of primary marrow cavity, appearance of secondary ossification center
4. Bone at birth, with enlarged cavity and appearan

Intramembranous Ossification

produces the flat bones of the skull and ,most of the clavicle. Such bones develop within a fibrous sheet similar to the dermis of the skin. aka dermal bones

Endochondral Ossification

a process in which bone is preceded by hyaline cartilage "model" that becomes replaced by osseous tissue. Begins in

Wolff's law of bone

architecture of bone determined by mechanical stresses placed on it and bones adapt to withstand those stresses
-Remodeling is a collaborative and precise action of osteoblasts and osteoclasts
-Bony processes grow larger in response to mechanical stress

Calcium Homeostasis

-Calcium and phosphate are used for much more than bone structure
-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

Hypocalcemia

Calcium deficiency

Hypocalcemia

causes:
Vitamin D deficiency
Diarrhea
Thyroid tumors
Underactive parathyroids
Pregnancy and lactation
Accidental removal of parathyroid glands during thyroid surgery

Calcium Homeostasis Hormones

Calcitriol, calcitonin, and parathyroid hormone

Calcitrol

a form of vitamin D produced by the sequential action of the skin, liver, and kidneys

Calcitrol

produced by
-Epidermal keratinocytes use UV radiation to convert a steroid, 7-dehydrocholesterol to previtamin D3
-Liver adds a hydroxyl group converting it to calcidiol
-Kidneys add another hydroxyl group, converting that to calcitriol
(most active form

Calcitrol

effects
Calcitriol behaves as a hormone that raises blood calcium concentration
-Increases calcium absorption by small intestine
-Increases calcium resorption from the skeleton
-Promotes kidney reabsorption of calcium ions, so less lost in urine
-Necessar

Rickets

abnormal softness in bones in children without adequate vitamin D

Osteomalcia

abnormal softness in bones in adults without adequate vitamin D

Calcitonin

secreted by C cells (clear cells) of the thyroid gland when calcium concentration rises too high

Calcitonin

Lowers blood calcium concentration in two ways
-Osteoclast inhibition
Reduces osteoclast activity as much as 70%
Less calcium liberated from bones
-Osteoblast stimulation
Increases the number and activity of osteoblasts
Deposits calcium into the skeleton

Parathyroid Hormone (PTH)

secreted by the parathyroid glands which adhere to the posterior surface of thyroid gland

stress fracture

break caused by abnormal trauma to a bone

Pathalogical Fracture

break in a bone weakened by some other disease
ex bone cancer, osteoporosis

Fractures classified by structural characteristics

-direction of fraction line
-break in skin
-multiple pieces

Fracture repair process

1.formation of hematoma and granulation tissue
2.Soft callus formation. Deposition of collagen and fibrocartilage converts granulation tissue to a soft callus.
3.Hard callus formation Osteoblasts deposit a temporary
bony collar around the fracture to unit

Hypocalcemia

-causes excessive excitability of the nervous system and leads to muscle tremors, spasms, or tetany

tetany

the inability of the muscle to relax

Hypercalcemia

causes depression of the nervous system, emotional disturbances, muscle weakness, sluggish reflexes, and sometimes cardiac arrest.

insterstitial growth

growth in height for children and adolescents
Cartilage growth from within, by multipilcation of chondrocytes and deposition of new matrix in the interior.
dwarfism is a result of lack of interstitial growth in childhood and adolescence

appositional growth

bone growth in adulthood.
Growth by forming new layers on the surface of pre-existing layers; process of increasing in thickness rather than length.
In bones, this method of growth is accomplished by the addition of newly formed cartilage on the surface o

parathyroid function

removes phosphate, promotes calcium absorption, inhibits collagen, raising effects of calciferol

nondisplaced fracture

is one in which the bone pieces remain in proper anatomical alignment

displaced fracture

at least one piece is shifted out of alignment with the other

comminuted fracture

bone is broken into thre or more pieces

greenstick fracture

the bone is incompletely broken on one side but the other side is bent