Chapter 6

Bone Matrix

Organic and non organic components. Organic components include cells, collagen fibers and ground substance. Collagen Fibers give tensile <-----(capable of being drawn out or stretched) strength by resisting stretching and twisting & contribute to over all flexibility. Ground Substance is semisolid material that suspends and support the collagen fibers. Inorganic components of the bone provide its compressional strength.

Cancellous Cavities

Spaces around trabeculae (stores bone narrow)

Chondrocytes

When chondroblasts mature they becomes this cell. occupy small spaces called Lacune

Perichondrium

Two distinct layers form the perichondrium: an outer, Fibrous region of dense irregular connective tissue and inner, cellular layer. Fibrous Layer: provides protein and mechanical support, and secures the perichondrium to the cartilage and to other sources. Cellular Layer: contains stem cells (chondroblasts) necessary for the growth and maintenance of cartilage.

Articular Capsule

Two layers Outer fibrous layer made of dense regular connective tissue strengthens joint Inner synovial membrane secretes synovial fluid lubricates and nourishes articular cartilages absorbs shock during compression of the joint

Tendon sheath

elongated bursae around tendons, particularly in confined areas (wrist and ankle) where tendons rub each other

Matrix of cartilage

this is in between the lacunae, has fibers and ground substance. has proteogycans molecules and grycosaminoglycans molecules that attract water into the matrix

Interstitial Lamellae

this is the left over parts of osteons that have been partially resorbed. They often look like a 'bite" has been taken out of them. this lamellae is incomplete and typically no central canal.

Intramembranous Ossification

-bone growth within a membrane. -Bone forms from mesenchyme -Occurs in portions of skull and clavicles 1. Ossification centers form within thickened regions of mesenchyme. some mesenchyme cells (stem cells) differentiate into osteoblasts 2.Osteoid (precursor to solid bone matrix) undergoes calcification. secrete osteoid at primary ossification center ( later mineralize) 3. Woven/ immature (primary) bone and surrounding periosteum form. 4.Lamellar (secondary) /mature bone replaces woven bone as compact and spongy bone form.

Epiphyseal Disc/ growth plate

...

Synovial Cavity/ Joints space

...

Gliding/plane joints

1 flat surface fits together. called a plane. found between joints. allow movement in 1 plane. uniaxial. intercarples, intertarsals, articular facets of vertebra.

Articular Cartilage

All articulating bone surfaces in a synovial joint are covered by a hayline cartilage called ______. This cartilage reduces friction in the joints during movement, acts as s spongy cushion to absorb compression placed in the joint, and prevents damages to the articulating ends of the bone. Articular surfaces in synovial joints are covered by hyaline cartilage prevents bone-on-bone contact

Proteoglycans

Attract water into the matrix

Glycosaminoglycans

Attracts water into the matrix

Osteoblasts

Bone forming cells; produce new bone, and once ______ become entrapped in the matrix they produce and secrete, they differentiate in to osteocytes. osteoprogenitor stem cells become ______. They secrete a semisolid , organic form of bone matrix called OSTEOID- later calcifies and harden as a result of calcium salt deposition.

Meniscus

C- shaped fibrocartilage in the knee that resist compression and absorbs shock Pad like cartilage in the knee joint

Periosteum

Cover the outer surface of the bone, expect parts that are covered by articular cartilage. made up of dense irregular connective tissue and consists of an outer fibrous layer and inner cellular layer. Periosteum is anchored to the bone by numerous strong collagen fibers called perforating fibers. protects bone from surrounding structures, anchors blood vessels and nerves to the surface of the bone and provides stem cells (osteoprogenitor cells and osteoblasts for bone width growth and fracture repair. One location : Outside the bone

Cancellous/Spongy bone

Doesn't have haversian systems. these bone appears more porous, like a sponge have trabeculae.

uniaxial

If the bone moves in just one plane or axis

Multiaxial /triaxial

If the bone moves in multiple planes or axes

Biaxial

If the bone moves in two planes or axes

Epiphysis

Is enlarged to strengthen the joint and provide added surface area for bone-to-bone articulation as well as tendon and ligament attachment. It is composed of an outer layer of compacted bone and inner layer of spongy bone.

Accessory Liagments

Ligaments: connect bone to bone, dense regular connective tissue, job to provide stability. strengthen and reinforce capsule Nerves: signal (pain) when a joint is over stretched Blood vessels: nourish tissues in the joint

Diarthrosis

Mobile joint. Freely movable. ( most common Joint) Location: Shoulder

Fibrous Joints

Occurs where bones are held together by dense regular (fibrous) connective tissue. Collagen fibers between bones (or between bone and tooth) Three types Gomphoses: teeth to maxilla and mandible Sutures: between skull bones Syndesmoses: between parallel bones (radius and ulna, tibia and fibula) Immobile or only slightly mobile

Cartilaginous Joints

Occurs where bones are joined by cartilage. Bones attached by cartilage Two types Synchondroses: bones joined by hyaline cartilage (usually immobile) Symphyses: bones joined by pad of fibrocartilage (slight mobility)

Trabeculae

Pieces of spongy bone

Short Bone

Structure: have a length nearly equal to their width. External surfaces of ____ bone are covered by compact bone, and their interior is composed of spongy bone. Location: carpales, tarsals, sesamoid bone ( tiny, seed-shaped bones along the tendons of some muscles, are also classified as short bone. patella ( Kneecap) is the largest sesamoid bone. (sesamoid bone reduce stress)

Diaphysis

The elongated, usually cylindrical _______ provides for the leverage and major weight support of a long bone.

Hemopoiesis/hematopoiesis

The process of Blood cell production. Blood cells are produce in a connective tissue called red bone barrow.

Epiphyseal line

in adults, the remnant of the epiphyseal plate is a thin layer of compacted bone called _________.

Endochondral Ossification

-Bone forms from hyaline cartilage -Occurs in all other bones of skeleton (except portions of skull and clavicles) 1. Fetal hyaline cartilage model develops/ bone collar forms 2.Cartilage matrix calcifies and a periosteal bone collar forms around diaphysis. chondrocytes elongate and die and disintegrate because nutrients can't diffuse to them through this calcification matrix. 3. Primary ossification center forms in the diaphysis, a growth of capillaries and osteoblasts, called periosteal buds extend from the peripsteum into the core of the cartilage shaft. ( blood vessels, osteoblasts, osteoclasts), bone development extends in both directions towards the epiphyses from primary ossification center. healthy bone tissue quickly replaces the calcified , degenerating cartilage in the shaft. (most formed by 12th week of development.) 4. Secondary ossification centers form in the epiphysis/ same basic process and primary ossification center. not all secondary ossification centers form at birth; some form later in childhood. as secondary ossification centers form osteoclasts resorb some bone matrix within the diaphysis, creating a hollow medullary cavity. 5.Bone replaces cartilage, except the articular cartilage and epiphyseal plates 6.Epiphyseal plates ossify and form epiphyseal lines. as bone reaches adult size , each epiphyseal plate ossifies. only remnant of each epiphyseal plate is an internal thin line of compact bone called epiphyseal line.

Synchondrosis

Articulation in which bones are joined by hayline cartilage. Functionally, all synchondroses are immobile and thus classified as synarthroses. Location: Epiphyseal plate, costochondral joints- the joints between each bony rib and its respective costal cartilage.

Chondroblasts

Cartilage forming cells; Cells that produce the matrix of cartilage.

Syndesmosis

Fibrous joints in which articulating bones are joined by long strands of dense regular connective tissue only. syndesmoses allow for slight mobility, they are classified as amphiarthroses. (radius and ulna, tibia and fibula)

Collagen Fibers

Gives bone its tensile strength by resisting stretching and twisting & contribute to over all flexibility.

Symphysis

Growing together- has a pad of fibrocartilage between the articulating bone. These fibrocartilage resists compression and tension stresses and acts as a resilient shock absorber. All symphyses are amphiarthroses, meaning that they allow slight movement. Locations; Body of vertebra, pubic symphysis.

Cartilage

Has a firm, gel-like extracellular matrix composed of both protein fibers and ground substance. Connective tissue.

Synovial joints

Has a fluid-filled joint cavity that separates the cartilage-covered articulating surfaces of the bone. The articulating surfaces are enclosed within a capsule, and the bones are also joined by various ligaments.

Fibrocartilage

Has numerous coarse, readily visible fibers in its extracellular matrix. The fibers are arranged as irregular bundles between large chondrocytes. There is only a sparse amount of ground substance, and often the chondrocytes are arranged in parallel rows. The densely interwoven collagen fibers contribute to the extreme durability of this type of cartilage. It has no perichondrium because stress applies at the surface of the ________ would destory this tissue layer. Location: interverrebral discs, The pubic symphysis, menisci, C-shaped cartilage in the knee. Function: acts as a shock absorber and resists compression.

Osteocytes

Mature cells located in lacunae: derived from osteoblasts that have become entrapped in the matrix they secreted. maintain the bone matrix and detect mechanical stress on a bone.

Hyaline Cartilage

Most common type of cartilage and also the weakest. Named for its clear , glassy appearance under the microscope. The chondrocytes within their lacunae are irregularly scattered throughout the extracellular matrix. However the collagen within the matrix is not readily observant by light microscopy because it is primarily in the form of submicroscopic fibrils. It provides support through the flexibility and resilience. ____ cartilage is surrounded by perichondrium. Looks like carbonated grape soda. lacunae represent the bubbles in the soda. Function: _____ cartilage has many functions in addition to its primary one of supporting soft tissue. form most of the fetal skeleton and is a model for most future bone growth. The cartilages at he articulating ends of a long bone allow the bones in a joint to move freely and easily. Location: _____ cartilage is found in many places in he body , including the nose, trachea, most of the larynx, costal cartilage, and articulating ends of bones.

Osteoclasts

Remove and resorption of bone cells. resorbs bone matrix ( they come from a different cell in the bone marrow) Osteoclasts remove matrix and Osteoblasts add to it, maintaining a delicate balance.

Volkmann's canal/perforating Canal

Resemble central canal -they also contain blood vessels and nerves. However these canals run perpendicular to the central canal and help connect multiple central canals.

Osteoid

Secreted by osteoblasts (immature matrix)

Irregular Bone

Structure: complex shapes, don't fit into any other category. Location: facial bones, vertebrae,pelvic bone, bones in the skull.

Long Bone

Structure: have a greater length than width. have a elongated , cylindrical shaft (diaphysis)MOST COMMON BONE SHAPE. Location: Bones of the extremities, metacarpals, metatarsals, phalanges,

Osteon/Haversian System

The basic functional and structural unit of mature compact bone. An ______ is a three dimensional structure that has several components. Haversian systems contribute to the strength of compact bone, which is the really hard protective bone (compared to spongy). They are designed to help the bone resist stress and fractures.

Medullary Cavity ( marrow Cavity)

The hollow cylindrical space within the diaphysis is call Marrow cavity. in adults, it contains yellow bone barrow

Metaphysis

The region in a mature bone sandwiched between the diaphysis and the epiphysis. In a growing bone , this region contains the epiphyseal (growth) plate , thin layers of hyaline cartilage that provide for the continued lengthwise growth of the diaphysis.

Circumferential Lamellae

These are the rings of bone immediately internal to the periosteum of the bone (external circumferential lamellae & internal circumferential lamellae- appear during the original formation of the bone and run the entire circumference of the bone itself.

Flat bone

These bones are named so because they have flat, thin surfaces. Structure: These bones are composed of roughly parallel surfaces of compact bone with a layer of internally placed spongy bone. Function: provide extensive surfaces for muscle attachment and protects underlying soft tissue. Location: Cranial bone, mandible, sternum, ribs, clavicles,scapula,

Hydroxyapatite Crystals

These crystals deposit around the collagen fibers in the extracellular matrix , leading to hardening of the matrix. These crystals also incorporate other salts, such as calcium, carbonate and ions such as sodium, Magnesium, sulfate and fluoride in the process of calcification.

Lacune

With in the extracellular matrix. Little Lakes, Cavities that happen to be there.

Red bone marrow

____ bone barrow contains stem cells that form all of the formed elements in the blood. Location: Children: spongy bone and medullary cavity of most of the bones of the body. Location: Adults: selected portions of the axial skeleton, Flat bone of the skull, the vertebrae, the ribs, the sternum (breastbone) and the ossa coae ( hip bone) Adults also have red bone marrow in the proximal epiphyses of each humerus and femur.

Sutures

are immobile fibrous joints that are found only between certain bones of the skull. They have distinct interlocking, usually irregular edges that both increase their strength and decrease the number of fractures at the articulation. In addition to joining bones sutures permit the skull to grow as the brain increases in size. during childhood.

Condyloid/ellipsoid joints

biaxial joints with oval convex surfaces on the bone that articulates with convave articular surface on the second bone. biaxial joints can move in 2 axis such a back and forth and side-to-side. Wrist, metacarpophalangeal, ( knuckles) , metatarsophalangeal ( Foot)

Ossification/osteogenesis

formation and development of bone connective tissue. Bone formation begins in the embryo and continues as the skeleton grows during childhood and adolescence. Formation of bone (also known as osteogenesis) begins by 8th week of gestation and continues into adulthood Two types of ossification Intramembranous Endochondral

Endosteum

incomplete layer of cells that covers the internal surface of the bone, such as the madullary cavity. The _______ contains osteoprogenitor cells, osteoblasts, and osteoclasts and is active during bone growth, repair and remodeling. 2 Locations: 1. Lines medullary cavity 2. Covers trabeculae

Haversian canal/Central canal

is a cylindrical channel that lies in the center of the osteon. Traveling within the central canal are the blood and nerves that supply the bone.

Amphiarthrosis

is a slightly mobile joint. Slightly moveable Location: pubic bone

Pivot joints

is a unaxial joint in which one articulating bone with a rounded surface fits into a ring formed by ligaments and another bone. C1 - C2 ( attached axial joints)

Synathrosis

is an immobile joint. non-movable joints. Location: sutures on cranial bone.

Synovial Fluid

is composed of secretions from synovial membrane cells and filtrate from blood plasma, Synovial fluid has 3 function: 1. Lubricates the articular cartilage on the articulating bones (same way that oil in a car engine lubricates the moving engine parts) 2. nourishes the articular cartilage's chondrocytes. The relatively small volume of synovial fluid must be circulated continually to provide nutrients and remove wastes to these cells. Whenever movement occurs at a synovial joint, the combined compression and re-expansion of the articular cartilage circulate the synovial fluid into and out of the cartilage matrix. 3. Also acts as a shock absorber, distributing stresses and force evenly across the articular surfaces when the pressure in the joint suddenly increases.

Elastic Cartilage

is so named because it contains numerous ____fibers in its matrix. the higher ___ of fibers in this cartilage causes it to appear yellow in fresh secretion. The chondrocytes of ____ cartilage are almost indistinguishable from those of hyaline cartilage. they are typically closely packed and surrounded by only small amounts of extracellular matrix. these ____ fibers are both dense and more highly branched in central region of the extracellular matrix. where they from a weblike mesh around chondrocytes within the lacunae These fibers ensures that ____ cartilage is extremely resilient and flexible Elastic cartilage is surrounded by perichondrium. Location: epiglottis ( structure in the larynx that prevents swallowed food and fluids from entering the trachea, and external ear. FLEXIBLE.

Saddle Joints

is so names because the articular surfaces of the bone have convex and concave regions that resemble the shape of a saddle. it allows a greater range of movement than either a condylar joint or hinge joint. Only one saddle joint ( 1 metacarpal joint) biaxial joint.

Synovial Membrane

membrane is composed primarily of areolar connective tissue, covers all the internal joints surfaces not covered by cartilage, and lines the articular capsule.

Ball & socket joints

move in three planes- Multiaxial joint in which spherical articulating head of one bone fits into the rounded, cup-like socket of the second bone, considered free moving synovial joint. Hip , shoulder

Fibrous Capsule

out layer is formed from dense connective tissue and it strengthens the joint to prevent the bone from being pulled apart.

Yellow bone marrow

red bone barrow degenerates and turns into fatty tissue called ______.

Resorption/resorbed

removal of bone

Gomphosis

resemble a "peg in a socket" The immobile joint between a tooth and the jaw.

Concentric Lamellae (plate)

ring of bone connective tissue that surround the central canal and form the bulk of the osteon. The number of this plate vary among osteons. Structure: Each plate contains collagen fibers oriented in one direction;adjacent lamellae contain collagen finers oriented in alternating directions. If one lamellae has collagen fibers directed superiorly and to the right, the next lamellae will have collagen fibers directed superiorly and to the left. THE ALTERNATING COLLAGEN FIBER DIRECTION GIVES BONES PART OF ITS STRENGTH AND RESILIENCE.

Bursae

sacs outside most synovial joints where ligaments, muscles, tendons, and/or bones rub. found around most synovial joints and also where bone, ligament, muscles, skin, or tendons overlie each other and rub together. These sacs may either be connected to the joint cavity or completely separate from it.

ossifies

turn into bone or bony tissue

Hinge joints

unaxial joints which the convex surface of the articulating bone hits into a concave depression the other bone. allows movement in 1 plane ( like the hinge of a door) Elbow, knee, ankle, between the phallenges.