Chapter 6 Bones and Skeletal Tissues

Facet

Projection that helps form joints Smooth, nearly flat articular surface

Meatus

Canal like passageway

greenstick fracture

bone breaks incompletely where only one side breaks and the other bends, and this is common in children where bones are more flexible having more organic matrix than adults

Trabeculae

Carefully positioned along stress lines to reduce bone stress

How long does it take for a bone to heal?

- 6-8 weeks for a simple fracture -6-8 weeks for small to medium sized bones in young adults -Weight bearing bones and fracturs in elderly take longer

Treatment of osteoporosis

-Calcium and Vitamin D supplements -Weight bearing exercise -Medication such as HRT, Biphosphonates (alendronate), SERMS (raloxifene)

step 4 of Endochondral ossification

-Diaphysis enlongates and a medullary cavity is formed -secondary ossification occurs in the epiphysis

Step 5 of Endochondral ossification

-Epiphysis ossifies -Hyaline cartilage remains in the epiphyseal plate and in articular cartilage

Consequences of abnormal blood calcium

-Increase, hyperexcitability -Decrease, nonresponsiveness; inability to function - Sustained hypercalcemia leads to inhibiting organ functioning

What causes osteomalacia and rickets?

-Insufficient dietary calcium -insufficient dietary vitamin D

Step 2 of Intramembranous ossification

-Osteoblasts begin to secrete osteoid, which calcifies in a few days -Trapped osteoblasts become osteocytes

Risk factors for osteoporosis

-Petite stature -insufficient exercise -poor dietary calcium -abnormal vitamin d receptors -smoking -endocrine disorders such as diabetes mellitus -immobility -steroid use

What are the negative effects of HRT?

-Slows bone deteriation but does not reverse it -Increase risk of heart attack, stroke, and breast cancer

Step 4 of Intramembranous ossification

-Trabeculae thickens below the periosteum -Mature lamellar bone replaces wovem bone forming compact bone plates -Spongy bone consisting of distinct trabeculae exists internally where its vascular tissue becomes red marrow

Step 3 of Intramembranous ossification

-Woven bone forms: Network of trabeculae due to accumulating osteoid between embryonic blood vessels -Periosteum forms: vascularized mesenchyme condenses on the external face of woven bone

How much bone mass is recycled each week?

5-7%

Inorganic components

65% of bone mass consisting of hydroxyapatites or mineral salts/calcium phosphates Crystalize around collagen which accounts for hardness of bone resisting compression

Blood calcium level must be maintained within ________-.

9-11 mg/dL blood

The bone stores ______ of body calcium.

99%

fracture

A break in a bone

Rickets

A disorder similar to osteomalacia that occurs in growing bones of children -more severe than osteomalacia due to growth -bowed legs, deformity of pelvis, skull, and ribs

Osteoporosis

A medical condition in which the bones become brittle and fragile from loss of tissue due to more bone resorption than bone deposit

Step 2 of Endochondral ossification

Cartilage in the center of diaphysis calcifies and develops cavities

Perforating canals

Also known as Volkmann's canals; run perpindicular to the central canal and connects the blood and nerve supply of the periosteum to those in the central canal and the medullary cavity.

Osteon

Also known as the Haversian system; structural unit of compact bone which consists of a group of hollow tubes one inside the other

Spongy Bone

Appears poorly organized compared to compact bone; No Osteons, Contains irregularly arranged lamellae; Canaliculi connect osteocytes; nutrients reach osteocytes from capillaries in endosteum covering trabeculae

Why is bone considered an organ?

Because it contains multiple tissue types

Hematopoiesis

Blood cell formation

Sacrificial bonds

Bonds located in or between collagen molecules which break on impact dissipating energy to resist fracture

Step 1 of Endochondral ossification

Bone collar forms around the diaphysis of the hyaline cartilage model

Osteogenesis

Bone formation

Comminuted fracture

Bone fragments into three or more pieces and is common in the aged where bones are more brittle

Endochondral ossification

Bone from hyaline cartilage

Ossification

Bone remodeling or replacing tissue with bone

Osteoclast

Bone resorbing cell or bone destroying cells

What is the endosteum made of?

CT, osteoblast, osteoclasts

Sinus

Cavity within a bone, filled with air and lined with mucous membrane

medullary cavity

Cavity within the shaft of the long bones filled with bone marrow

Endosteum

Connective tissue membrane covering internal bone surfaces specifically trabeculae and canals through compact bone

What two processes constitute bone remodeling?

Deposit and resorption

Periostium

Double-layered connective tissue that covers and nourishes the bone except on joints; provides anchor for ligaments and tendons

Why is bone durable and strong but not brittle?

Due to its precise combination of organic and inorganic matrix elements

Bone lining cells

Flat cells found on bone surfaces where bone remodeling is not going on which are believed to help maintain the bone matrix

Groove

For passage of blood vessels and nerves Furrow

Notch

For passage of blood vessels and nerves Indentation at the edge of a structure

Fissure

For passage of blood vessels and nerves Narrow, slitlike opening

Foramen

For passage of blood vessels and nerves Round or oval opening through a bone

Compact bone

Hard, dense bone tissue that is beneath the outer membrane of a bone

Haversian (central) canal

Hollow tube through the middle of an osteon containing blood vessels and nerves

Remodeling and repair of bone is part of ________.

Homeostasis

What regulates bone growth?

Hormones

Red bone marrow

Includes stem cells that can produce red blood cells, white blood cells, or platelets

Interstitial lamellae

Incomplete lamellae between osteons; either fill the gaps between forming osteons or are remnants of osteons that have been cut through by bone remodeling.

Lamella

Individual tubes that make up the osteon

What does the skeleton in the human embyro consist of before week 8?

It consists of fibrous membrane and hyaline cartilage. After week 8, bone tissue develops

Why is the role of calcium in blood important for homeostasis?

It is needed: - to transmit nerve impulses - in muscle contraction - in blood coagulation - in cell division

What makes up the organic components of bone?

Its cells and osteoid (35% bone mass) Reservoir for caclium and phosphate which is deposited and withdrawn as need; Growth factors

What is the periosteum made of?

Its outer fibrous layer consists of dense irregular CT and its inner layer consists of osteoblasts and osteoclasts

Circumferential lamellae

Lamellae adjacent to periosteum and endosteum

Osteoblast

Matrix-synthesizing cell responsible for bone growth or bone forming cells

Osteocytes

Mature bone cell that monitors and maintains the mineralized bone matrix

How does bones respond to stress?

Mechanical stress and gravity maintains bone strength -Thickens bones -Bones develop heavier prominences -Rearranges trabeculae

Osteogenic cell

Mitotic stem cells in the periostium and endosteum which can develop into osteoblasts or bone lining cells, or persist as osteogenic cells.

Osteoid

Organic part of the bone matrix which makes up 1/3 of matrix; includes ground substance and collagen fibers which both are made and secreted by osteoblasts. Contributes to bone strength, structure, and its flexibility to resist stretch and twisting

What are the 5 major cell types that make up bone tissue?

Osteogenic cells, osteoblasts, osteocytes, bone lining cells, osteoclasts

Describe homeostatic imbalance in blood calcium

Parathyroid gland releases PTH (parathyroid hormone) which stimulates osteoclasts to resorb bone releasing calcium into the blood stream. When calcium levels in the blood rises, the stimulus for PTH release ends.

Step 3 of Endochondral ossification

Periosteal bud invades the internal cavities and spongy bone forms

What are the three membranes in a bone structure?

Periosteum, Endosteum, collagen fibers

Condyle

Projection that helps form joints Rounded articular projection

Osteoporosis is most common in which group of people?

Postmenopausel women because estrogen restrains osteoclasts and promotes bone deposition

Ramus

Projection that helps form joints Armlike bar of bone

Head

Projection that helps form joints Bony expansion carried on a narrow neck

Ground subtance

Proteoglycans and glycoproteins

Epiphyseal line

Remnant of epiphyseal plate between the diaphysis and epiphysis Contains hyaline cartilage disc that grows in children to increase bone length and overal height

Step 1 of Intramembranous ossification

Selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center that produces the first trabeculae of spongy bone

Fossa

Shallow, basinlike depression in a bone, often serving as an articular surface

Process

Site of muscle/ligament attachement Any bony prominence

Tuberosity

Site of muscle/ligament attachement Large rounded projection; may be roughened

Crest

Site of muscle/ligament attachement Narrow ridge of bone; usually prominent

Epicondyle

Site of muscle/ligament attachement Raised area on or above a condyle

Spine

Site of muscle/ligament attachement Sharp, slender, often pointed projection

Tubercle

Site of muscle/ligament attachement Small rounded projection or process

Trochanter

Site of muscle/ligament attachement Very large, irregularly shaped process found on the femur

Lacunae

Small cavities in bone that contain osteocytes

What hormones contribute to bone growth in puberty?

Testerone and estrogen

bone resorption

The process whereby osteoclasts breakdown bone matrix

How do long bones increase in length?

Through interstitial growth of the epiphyseal plate cartilage and its replacement by bone

What hormone regulates bone growth in infants and children?

Thyroid hormone

Canaliculi

Tiny canals that connect lacunae and the central canal by linking all osteocytes in the osteon.

Paget's disease

Treatments include calcotonin and biphosphonates such as alendronate

Paget's disease

abnormally high ratio of spongy tissue to compact bone

How does long bone increase in width?

appositional growth and remodeling

why is bone dynamic?

because it continually being formed and resorbed influence by hormonal changes, physical activity, diet, etc.

The addition of minerals and collagen fibers to bone by osteoblast is called ________.

bone deposit

Paget's disease

bone deposit and bone resorption are not occuring at the same rate and reduced mineralization of bone

epiphysis

bone ends -outer compact bone/inner spony bone -joint surface covered with articular cartilage

Compression fracture

bone is crushed and is common in porous bones subjected to extreme trauma such as a fall

The process whereby osteoclasts breakdown bone matrix is called ____________.

bone resorption

Closed reduction

bones manipulated into position with surgery usually using hand

Depressed fracture

broken bone portion is pressed inward and is a typical skull fracture

Periosteal bud

contains a nutrient artery and vein, lymphatic vessels, nerve fibers, red marrow elements, osteogenic cells, and osteoclasts

Collagen fibers

contribute to flexibility and tensile strength

dwarfism

deficit of growth or thyroid hormone leading the short stature

Paget's disease

deformity and pain increase with time

Epiphyseal fracture

epiphysis separates from the diaphysis along the epiphyseal plate and tends to occur where cartilage cells are dying and calcification of the matrix is occuring

In young healthy adults bone mass is constant but not static because the rate of deposit and resorption are essentially __________.

equal

gigantism

excessive growth hormone in children leading to excessive height

Intramembranous ossification

formation of flat bones such as the cranial bones and the clavicles from fibrous membrane

Epiphyseal plate closure

fushion of epiphysis and diaphysis ending growth in bone length induced by testerone/estrogen

Interstitial growth

growth from inside

appositional growth

growth from outside

Bone remodeling is controlled by ______ and ________.

mechanical force, hormones

Paget's disease

often found first on x-rays done for unrelated reasons

Paget's disease

often localized to spine, pelvis, femur, or skull

Paget's disease

patchy weakness of bone

immobilization

preventing movement of fracture to allow healing by cast or traction

Spiral fracture

ragged break occurs when excessive twisting forces are applied to the bone and is a common sports fracture

Reduction

realignment of broken bones

Bone Remodeling

simultaneous bone depostion and resorption which maintains appropriate proportions between diaphysis and epiphysis

Osteomalacia

softening of the bone due to: -bones are inadequately mineralized -calcium salts not deposited -symptom includes pain with weight bearing

open reduction

surgical realignment of bones with pins or wires

Paget's disease

the cause is unknown

Diaphysis

tubular shaft of long bone containing a thick outer layer (compact bone) and medullary cavity where yellow marrow exists in adults

Metaphysis

where the diaphysis and epiphysis meet