The Skeletal System

Objectivesunderstand the functions of the human skeleton and why bones are so important for health

classify human bones and provide examples

understand the composition of bone and that they are dynamic structures

give examples of bone diseases and preventative measures

know the difference between osteoblasts and osteoclasts

Adult humans have on average 206 bones

They can be broken into 2 categories:

Axial Skeleton (80 Bones)

Appendicular Skeleton (126 Bones)

The Human Skeletonhttps://www.youtube.com/watch?v=UPrxQkjjExI

Axial Skeleton

Upper body includes:

skull

vertebrae (spine)

ribs

sternum (breastbone)

bones that form the longitudinal axis of the body

Appendicular Skeleton

Lower body includes:

arms

legs

pectoral girdle (shoulder blades and collar bone)

pelvic girdle (hip bones)

Functionssupport - form the internal framework that supports and anchors the body trunk

protection - protect soft body organs

movement - muscles use the bones as levers to move

storage - fat is stored in the internal cavities of bones, store minerals like calcium

blood cell formation - hematopoiesis occurs within the marrow cavities of bones

Classification

Long: Provide strength and support

example: arm and leg bones

Flat: Protect soft tissues and serve as points for muscle attachment

example: skull bones

Short: Provide flexibility and allow for movement

example: hand bones

Irregular: Protect nerves and spinal cord

example: Vertebrae

long bones

flat bones

short bones

irregular bones

Bone FormationIn womb development:

made of soft, flexible material called hyaline cartilage

By birth:

much cartilage has hardened and turned to bone this process is called ossification

new bone tissue can still be made

bones come from minerals from food eaten like calcium which turns bones rock hard

collagen: strong, stringy material runs through most bones to toughen them

Bone Formationhyaline carriage is completely covered in bone-forming cells (osteoblasts)

hyaline cartilage is digested and opens the medullary cavity

as bones grow in length, they also widen

after birth, the only two regions not converted to bone are the articular cartilages (persist for life) and epiphyseal plates (persist during childhood)

Ossification

Compositionbones are made up of living bone cells, connective tissue fibers, and inorganic compounds

There are 3 main tissue layers:

1. Periosteum

2. Compact bone

3. Spongy bone (Cancellous)

Periosteum

Double layer of connective tissue that surrounds bones except at its ends where it connects to other bones

Also serves as a point of attachment for muscles to bones and other bones

Includes: cartilage, ligaments, tendons

Function: Production of new bone for growth and repair (lower layer has bone forming cells called osteoblasts)

Compact Bone

Dense, strong layer that forms the outer shell of all bones

Hardness is due to spider-like mature bone cells called osteocytes

Contains canals called canaliculi which are filled with blood vessels and join to larger canals called the Haversian Canal

Rich in nerves

Function: Protection

Spongy Bones

also referred to as cancellous bone

Makes up the interior of bones

Less dense than compact bone and is very porous (full of “holes”)

Contains two types of marrow in separate areas

yellow and red

Bone Marrow

A) Yellow bone marrow

Function: fat storage area that the body uses for energy during starvation

Begins to form during adolescence

Red bone marrow

Function: A blood-cell factory producing white and red blood cells along with platelets to replace those routinely lost daily

major issues from eating disorders anorexia and bulimia

https://www.youtube.com/watch?v=XbRLMbDtiaA

Homeostasis when blood calcium levels drop below regular levels the parathyroid glands (in the throat) release PTH (parathyroid hormone)

this activates osteoclasts (bone destroying cells) which break down the bone matrix releasing calcium into the blood

when blood calcium levels are too high calcium is deposited in the bone matrix as calcium salts

Types of Joints•A joint is a point in the skeleton where bones meet

There are 3 categories of joints:

Fibrous (immovable)

example: skull

Cartilagenous (slightly moveable)

example: ribs

Synovial (highly moveable)

example: knee

Synovial JointsGliding (Plane/Ellipsoidal) - example: ankle and spine

Allow side-to-side and back-to-forth movement

Hinge - example: finger

Allows up and down movement in one plane

Pivot - example: ulna and radius in arm

Permits rotation

Saddle - example: thumb

permits side-to-side of back-and-forth movement but does not permit rotation

Condyloid Joint - example: wrist

permits side-to-side and back-and-forth movement but no rotation

Ball and Socket - example Hips and Shoulders

Permits movement in all directions plus rotation

https://www.youtube.com/watch?v=0cYal_hitz4

Osteoporosis

is a bone thinning disease that overwhelmingly effects older women (50% of women 65+ compared to 20% of men 70+)

bones need to be physically stressed to remain healthy

estrogen is important in maintaining density of the skeleton in women, in menopause estrogen levels drop leaving women susceptible

other factors: diet lacking calcium and protein, lack of vitamin D, smoking, insufficient weight bearing exercises

loss of density can be so severe a hug or a sneeze can cause fractures

https://www.youtube.com/watch?v=jUQ_tt_zJDo

Arthritis

describes over 100 different inflammatory or degenerative diseases of the joints

most widely spread crippling disease in the US (1 in Americans)

symptoms: pain, stiffness, and swelling of the joint

depending on the type, following symptoms, different joint structure changes occur

rheumatoid arthritis (inflammation)

osteoarthritis (degenerative)

gouty arthritis aka gout (uric acid accumulation deposited in joints as needle shaped crystals)

https://www.youtube.com/watch?v=0vlLiPT_Otw

Osteoarthritisthe most common form of arthritis

chronic degenerative condition typically affecting the aged

softening fraying and eventual breakdown of the cartilage exposing the bone which thickens and and extra bone tissue is produced (bone spurs) reducing joint movement

symptoms: stiffness that lessens with activity, crunching noise (crepitus) with movement

commonly effects: fingers, cervical and lumbar joints in the spine, knees, and hips.

Additional Resources

The Human Bones Song: https://www.youtube.com/watch?v=h5dYvPruBFY

Interactive Skeleton: http://www.klbict.co.uk/interactive/science/skeleton_function.htm

Bones Structure: http://www.youtube.com/watch?v=c5zcGv8MvMc&feature=related

Types of Synovial Joints: http://www.youtube.com/watch?v=zWo9-3GJpr8&feature=related