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Skeletal System: Bones and Joints

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keith peterson

on 12 July 2014

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Transcript of Skeletal System: Bones and Joints

Skeletal System: Bones and Joints
Bone growth, Maintenance, and Repair
Bone formation begins in the earliest weeks of embryonic life and continues until young adulthood (18-24 y.o.a). Even after growth is complete, bone cells actively maintain & repair bone tissue. pg. 133
Fractures
is a break in a bone, usually caused by some sort of trauma.

Let's look at some classifications of fractures
Joints
articulations
/
joints
:
is an area of junction b/t two or more bones.

Joints are classified into three main types on the basis of their material between the adjoining bones. They may also be classified according to the degree of movement permitted.
Types of Synovial Joints
Synovial joints are classified according to the types of movement they allow. It is always helpful to locate each type of joint on your body and perform the different movements that each joint allows when studying.
Disorders of joints
Joints are subjected to certain mechanical disorders.
Dislocations
: a derangement of the joint parts. Ball – and – socket joints, which have the widest range of motion, also have the greatest tendency to dislocate. The shoulder joint is the most frequently dislocated joint in the body.
Sprain
: is it the wrenching of a joint with rupture or tearing of the ligaments. There may also be injuries to the cartilage within the joint, most commonly in the knee joint.
Effects of aging on the skeletal system
A look back: remember we had looked at tissues and discussed bone tissue as the densest form of connective tissues.
Bones have a number of functions:
1) forms sturdy framework for body (support).
2) protect delicate structures, ex. brain, lungs.
3) acted as levers with muscles to produce movement.
4) mineral homeostasis: storing calcium salts and phosphates,
5) produce blood cells (in spongy/red marrow)
The term skeleton is used to describe the 1) bones, 2) ligaments, and 3) cartilage around the bones.

The skeleton consists of 206 bones, and is divided into a central or
axial skeleton.
and the extremity portion or
appendicular skeleton.
pg. 132, fig. 7-1

Bones of the skeleton have several different shapes.
1) flat= ribs, skull(cranium).
2) short= carpals of wrist, tarsals of ankle.
3) irregular= spine/vertebrae, facial bones.
4) sesmoid= patella/knee cap.
5) long= bones of the arms and legs (humerus, femur), these make up a major portion of the skeleton.


Which brings us to our first main topic
Anatomy of a long bone.
pg.133, fig. 7-2
1) diaphysis(body): is the long portion of the long bone.
2) Medullary cavity: the center of the diaphysis, which contains bone marrow.
3) metaphysis: enlargement of the long bone b/t diaphysis and epiphysis.
4) epiphysis: the ends of the long bone both proximal and distal ends. This is the area of articulation for the long bones.
Bone Marrow: bones contain 2 kinds of marrow.
Red Marrow:
found in spongy bone at the ends of long bones, and center of other bones. Red marrow manufactures blood cells.
Yellow Marrow:
found primarily in the central cavities of the long bones. yellow marrow is composed mostly of fat.
pg. 133, fig. 7-2


Bone Membranes: bones are covered on the outside by a membrane called
periosteum:
membrane with an inner layer that contains cells (osteoblasts) that are essential in bone formation during growth and bone repair from injury. The periosteum also contains important blood vessels for nourishment to bones, and nerves that are responsible for pain sensations when we injure ourselves.
endosteum:
a thinner membrane that lines the bone marrow cavity, and contains cells that aids in bone growth and repairs of bone tissue.
pg. 133, fig.7-2
Bone Tissues: known as osseous tissue is comprised by
osteocytes
= mature bone cells, as well as mineral deposits b/t the cells. Deposits are calcium(Ca++) salts. Osseous tissue also has a vast network of nerves, blood vessels, and lymphatic vessels.
We have 2 different types of bone tissue.
1) compact bone
2) spongy bone
pg. 133, fig. 7-2
Compact Bone:
is hard & dense. Makes up the diaphysis of long bones and the outer layer (capsule) of other bones. The cells in compact bone are arranged in a system called a
Haversian system/osteon
. Starting at the center of the haversian system is a
central/haversian canal:
containing nerves and blood vessels. Around the canal are multiple layers of rings known as
lamellae
. Locacted within each lamellae layer are
lacunae spaces
, which hold the bone cells (osteocytes). Between each layer of lamellae are little canals that connect each layer are
canaliculi.
Another canal crossing from one side of the shaft to the other are
perforating(Volkmann's) canals
. That allows for communication of blood vessels b/t haversian/osteons. pg.133,134, fig.7-3B
Spongy Bone: aka cancellous bone,
has a lot more spaces than compact bone. Made of a meshwork of small, bony plates filled with red marrow. Spongy bone is found in the epiphysis (ends), metaphysis, and center of other bones. pg. 134, fig. 7-3C
Fetal Ossification:
at first the fetal skeleton is primarily cartilage. Then around the 2-3 months of embryonic life ossification begins.
Ossification:
the conversion process of cartilage to bone.

this is when
osteoblasts
become active and manufacture the bone
matrix:
material b/t bone cells,

which contains large amouts of
collagen:
fibrous protein that gives tissue strength & resilience.


?
Later in life if a fracture occurs which cell does the bone resorption?
A) osteogenic B) osteoblast
C) osteocyte D) osteoclast
Formation of long bone:
transformation of cartilage into bone begins at the center of the shaft during fetal development. About the time of birth secondary bone-forming centers/
epiphyseal plates
develope at the ends of the bones. These epiphyseal plates allow for extra length in long bones. Once growth ends the epiphyseal plate hardens and becomes the
epiphyseal line.
Bone Resorption:
osteocyte:
is a cell that develops from the white blood cell(monocyte) and are multinucleated. These cells are responsible for bone resorption.
Resorption= breakdown of bone tissue.
Also an important step for bone remodeling. If you add new bone tissue, you will need to remove old, injured tissue. Resorption also occurs when the body needs bones stored minerals.

Peak bone mass is maintained until about age 40 on average.
Bone Markings: In addition to general shape, bones have other distinguishing features/
bone markings.
Bone markings are classified as
1) projections 2) depressions or holes
1) projections:
-head:
rounded, knob-like end separated from the rest of the bone by a slender region/neck. Articulation occurs here.
-process:
large projection of bone. ex= spinous process.
-condyle:
rounded projection for articulations that pivot. ex=knee, elbow, jaw.
-epicondyle:
a small projection above the condyle. For ligament attachment (colateral ligaments)
-crest:
a distinct border/ridge, usually rough. ex=iliac crest.
-spine:
a sharp projection from the bones surface. ex= spine of scapula/vertebrae.
2) depressions/holes:
-foramen:
hole that allows a vessel or a nerve to pass through or b/t bones (
foramina
=plural).
-sinus:
a cavity or hollow space, most commonly an air-filled chamber in the skull bones. Usually named by the bones they are located in.
-fossa:
a depression on a bone surface

(fossae=plural).
-meatus:
a short channel/passageway, usually the external opening of a canal. ex=external auditory meatus.
Let's talk cell classifications for a moment.
-genic:
are embryological cells.
-blast:
are building cells.
-cytes:
are mature functioning cells of a given tissue.
-clast:
are cells that consume or resorption cells.

Axial Skeleton:

consists of 80 bones and includes the bony framework of the head, spine, ribs, sternum, coccyx, and hyoid bone (think trunk).

Appendicular Skeleton: consists of 126 bones and forms the framework for the extremities (limbs) and for the shoulders and hips (think appendages).

-closed fractures:
simple break in bone with no open wound.
- open fracture:
broken bone protrudes through the skin or an external wound leads to a broken bone.
-greenstick fracture:
one side of a bone is broken & the other side is bent (most common in children).
-impacted fracture:
broken ends of the bone are jammed into each other.
-comminuted fracture:
more than one fracture line and the bone is splintered or crushed.
-spiral fracture:
bone has been twisted apart (common in skiing accidents).
-transverse fracture:
fracture goes straight across the bone.
-oblique fracture:
break that occurs at an angle across the bone.
Functional Classifications:
1) synarthrosis:
immovable, ex=sutures, syndesmosis.
Fibrous joints.



2) amphiarthrosis:
slightly movable, ex= intervertebral disc, costosternal, pubic symphysis.
Cartilaginous joints.


3) diarthrosis:
freely movable, ex= knee, elbow, facet joints, shoulder.
Synovial joints.

Remember, structure dictates function!
Fibrous joints
Cartilaginous joints
Synovial joints
pg. 151, table 7-2
pg. 151, table 7-2
pg. 152, fig.7-24 & 7-25
Movement of synovial joints:
chief function of freely moveable joints is to allow for motion.
pg. 153, fig. 7-26.
All movements describe changes in body position away from anatomical position. As you go through and learn these movements experiment with the movements on your body.
Angular movements:
-flexion:
decreasing the angle of a joint. ex= flexing the biceps.
-extension:
increasing the angle of a joint.
-abduction:
movement away from the midline.
-adduction:
movement towards the midline.
abduction & adduction= jumping jacks.
When we put all of our angular movements together we get special movements.
-circumduction:
draw an imaginary circle with an out stretched arm.
-rotation:
is a twisting/turning of a bone on it's axis. ex=turning the head from side-side.

Special movements of the forearm & ankle:
pg. 152, 153, fig.7-26.
-supination:
turning the palm up/forward.
-pronation:
turning the palm down/backward.
-inversion:
turning the sole of the foot inward.
-eversion:
turning the sole outward.
-dorsiflexion:
bending the foot upward at the ankle towards body.
-plantarflexion:
bending the foot away from the body at the ankle.
Bursae:
small sacs filled with synovial fluid, that are located near synovial joint. pg. 152, fig. 7-25. These bursae help ease movement over and around joints. Inflammation of a bursae is called
bursitis.
Gliding

joint
: two relatively flat bone services gliding over each other with little change in joint angle. Example: the joints between the tarsal and carpal bones.

Hinge

joint
: a convex surface of one bone fits into the concave surface of another bone, allowing movement in one direction. Hinge joints allow flexion and extension only, examples: the knee, elbow, and the joints between the phalanges.

Pivot

joint
: a rounded or pointed portion of one bone fits into a ring in another bone. This joint allows rotation only, as in the joints between the atlas and axis of the cervical spine or the proximal joint between the radius and all met that allows rotation (pronation/supination) of the forearm.
Condyloid

joint
: an oval–shaped projection of one bone fits into an oval–shaped depression on another bone. This joint allows movement in two directions – 1) flexion and extension 2) abduction and adduction. Examples: are the joints between the metacarpal bones and the proximal phalanges of the fingers.


Saddle

joint
: similar to the condyloid joint, but deeper and allowing greater range of motion. One bone fits into a saddle – like depression on another bone. To allow for movement in three directions: 1) flexion and extension, 2) abduction and adduction, 3) rotation. Examples: the joint between the wrist and the metacarpal of the thumb.
Ball – and – socket joint
: a ball – like surface of one bone fits into a deep cuplike depression in another bone. It allows the greatest range of motion in three directions,
circumduction
. Examples: the shoulder and hip joints.
Herniated

disc
: the discs between the vertebrae of the spine consist of an outer ring of fibrocartilage and a central mass known as the nucleus pulposus. In the case of a herniated disc, the nucleus pulposus protrudes through a weekend outer cartilaginous ring into the spinal canal. This puts pressure on the spinal cord or spinal nerves, often causing back spasms or pain along the sciatic nerve that travels through the leg, a pain known as
sciatica
.
Arthritis
: the most common type of joint disorder is termed arthritis, which means "inflammation of the joints." There are different kinds of arthritis:
Osteoarthritis
: also known as degenerative joint disease (DJD) usually occurs in elderly people. As a result of normal wear and tear. Although it appears to be a natural result of aging, such factors as obesity and repeated trauma can contribute. Osteoarthritis occurs mostly in joints used in weight bearing, such as the hips, knees, and spinal column. It involves degeneration of the joint cartilage, with growth of new bone at the edges of the joints. Degenerative changes include bone spur formation at the edge of articular surfaces, thickening of the synovial membrane, atrophy of the cartilage, and calcification of the ligaments.
Rheumatoid

arthritis
: is a crippling condition characterized by joint swelling in the hands, the feet, and elsewhere as result of inflammation in overgrowth of the synovial membranes and other joint tissues. The articular cartilage is gradually destroyed, and the joint cavity develops adhesions – that is, the services tend to stick together – so that the joints stiffen and ultimately become useless. The exact cause of rheumatoid arthritis is uncertain. However, the disease shares many characteristics of autoimmune disorders, in which the immune system attacks the body's own tissues. The role of inherited susceptibility is clear. Successful treatment includes rest, appropriate exercise, medications to reduce pain and swelling, and suppression of the immune response.
Septic
(
infectious
)
arthritis
: arises when bacteria spread to involved joint tissue, usually by way of the bloodstream. Bacteria introduced during invasive medical procedures, illegal drug injections, or by other means can settle in joints. A variety of organisms are commonly involved, including
Streptococcus
,
Staphylococcus
, and
Neisseria
species. The joints and the bones themselves are subject to attack by the tuberculosis organism, and the result may be gradual bone destruction near the joint.
Gout
: is a kind of arthritis caused by a metabolic disturbance. One waste product of metabolism is
uric

acid
, which normally is excreted in the urine. If there happens to be an overproduction of uric acid, or for some reason not enough is excreted; the accumulated uric acid forms crystals that are deposited as masses around the joints and in other areas. As a result, the joints become inflamed and extremely painful. Any joint can be involved, but the most commonly affected is the
big

toe
. Most gout sufferers are older
men
.
The aging process includes significant changes in all I do is use, including bone. There is a loss of calcium salts in the decreased ability to form the protein framework on which calcium salts are deposited. Cellular metabolism slows, so bones are weaker, less dense, and more fragile; fractures another bone injuries heal more slowly. Muscle tissue is also lost throughout adult life. Loss of balance and diminished reflexes may lead to false. Thus, there is a tendency to decrease the exercise that is so important to the maintenance of bone tissue.
Changes in the vertebral column with age lead to a loss in height. Approximately 1.2 cm (roughly a half-inch) is lost each 20 years beginning at age 40, owing primarily to a thinning of the inter-vertebral discs that are located between the bodies of the vertebrae. Even the vertebral bodies themselves may lose height and later years. The costal (rib) cartilages become calcified and less flexible, and the chest may decrease in diameter by 2 to 3 cm (1 inch), mostly in the lower portion of the chest.
At the joints, reduction of collagen and bone, tendons, and ligaments contributes to the diminished flexibility so often experienced by older people. Thinning of articular cartilage and loss of synovial fluid may contribute to joint damage. By the process of calcification, minerals may be deposited in and around the joints, especially at the shoulder, causing pain and limited mobility.


Remember, structure dictates function!
Bursae
: small sacs filled with synovial fluid that is located near synovial joint. These bursae help ease movement over and around joints. Inflammation of bursae is called bursitis.
Fibrous

joint
: the bones in this type of joint are held together by fibrous connective tissue. An example is a
suture
between bones of the skull. This type of joint is immovable and is termed a
synarthrosis
.
Cartilaginous

joints
: the bones of this type of joint are connected by cartilage. Examples are the joint between the pubic bones of the pelvis – the pubic synthesis – and the joints between the bodies of the vertebrae. This type of joint is slightly movable and is termed an
amphiarthrosis
.
Synovial

joint
: the bones in this type of joint have a potential space between them, called the
joint

cavity
, which contains a small amount of thick, colorless fluid. This lubricant,
synovial

fluid
, resembles uncooked egg white and is secreted by the membrane that lines the joint cavity,
synovial

membrane
. The synovial joint is freely movable and is termed a
diarthrosis
. Most of the body’s joints are synovial joints; they are described in more detail next.
More about synovial joints

The bones in freely movable joints are held together by
ligaments
, bands of fibrous connective tissue. Additional ligaments reinforce and help stabilize the joints at various points. Also, for strength and protection, there is a
joint

capsule
of connective tissue that encloses each joint and is continuous with the periosteum of the bones. The bone surfaces in freely movable joints are protected by a smooth layer of hyaline cartilage called
articular

cartilage
. Some complex joints may have additional cushioning cartilage between the bones, such as the Crescent – shaped medial meniscus and lateral meniscus in the knee joint. That may also appear as padding around the joint.


Near some joints are small sacs called
bursae
.

THE END
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