1. Human Biology
The Skeletal System

2. The Skeletal System…
The skeletal system is the body’s living framework
It consists of living material embedded in a matrix of nonliving material

3. The Skeletal System…
Made up of bones, cartilage, ligaments, and tendons
Cartilage-dense, fibrous, flexible connective tissue
Ligaments-connective tissue that holds bones together
Tendons- connective tissue that attaches bones to muscle
Consists of approximately 206 bones

4. The Skeletal System…Functions
Provides shape and support
Allows movement
Almost all bones are attached to muscles
As muscles contract, or shorten, they pull on bones causing them to move
Protects tissues and organs
Ex: vertebral column protects spinal cord
Rib cage protects internal organs

5. The Skeletal System… Functions
Stores certain materials
Some of these materials give bones their stiffness, others play roles in blood clotting, nerve functions and muscle activity
If the level of these substances in the blood falls below the normal range, the body will begin to remove them from where they are stored within the bones

6. The Skeletal System… Functions
Produces blood cells
Red cells – carry oxygen
White cells – destroy harmful bacteria

7. Development of Bones...
Many bones are formed from a type of connective tissue called cartilage
Cartilage is a stiff, jellylike material
Strong enough to provide support, flexible enough to bend and twist

8. Development of Bones… In newborns, many bones are almost all cartilage
The process of replacing cartilage with bone begins about 7 months before birth
The process continues until the age of 25 or so
Some forming and reforming of bones still occurs in adulthood, particularly where bone is under a great deal of stress

9. Development of Bones… In some places, the cartilage remains unchanged
Places where bone meets bone
Ex: knee, ankle, elbow
Two jobs in these places
Cushion bones against sudden jolts (jumping or running)
Provides a slippery surface for bones to move without rubbing against each other

10. Development of Bones… Bone growth
Growth takes place at both ends of long bones
Growth region is called Epiphyseal plate
Layer of cartilage in which mitosis takes place
Ossification
Process of cartilage being replaced by bone

11. Structure of Bones…
Bones are one of the toughest yet lightest materials in your body
Bones make up barely 14% of your body’s mass

12. Structure of Bones…
Bones = living material embedded in a matrix of non-living material
Osteocytes- living cells embedded in a network of tough protein fibers called collagen
Non-living part of bone- compounds containing calcium and phosphorous that surround the osteocytes and make bone hard

13. Structure of Bones… Periosteum Shaft
Covers all bones and helps to connect them to muscles
Provides a rich blood supply to nourish the bone
Shaft
Middle portion of a typical long bone
Central cavity surrounded by a hard bony material called compact bone

14. Structure of Bones… Haversian canals
Small channels that run through compact bone and contain the blood vessels that nourish the osteocytes

15. Structure of Bones… Central cavity of long bones Epiphyseal line
Filled with yellow marrow
Stores fat
Epiphyseal line
The shaft is separated from the ends by this line
Marks the area where growth formerly took place

16. Structure of Bones…
In flat bones and the ends of long bones, the hard material is very thin
Underneath hard material = spongy bone
Spongy bone mitigates shock, reduces the potential for injury during periods of physical exertion or as a result of a blow to the body
In some bones, the spongy material contains red marrow in which red and white blood cells are produced

17. Classification of Bones…
Bones are classified according to their shape
Long bones (arms and legs) – support weight and are involved in movement
Flat bones (skull, sternum) – protect underlying organs
Short bones (wrist, ankles) – provide great flexibility and precise movements
Irregular bones (ribs, scapula) – adaptations that provide for specific needs involving support, protection, and/or articulation

18. Structure of Skeleton…
The skeleton consists of approximately 206 bones
Two main divisions
Axial skeleton
Appendicular skeleton

19. Structure of Skeleton…
Axial skeleton
Central framework of support and protection
Consists of 80 bones including the skull, facial bones, vertebral column, and rib cage

20. Structure of Skeleton…
Function of axial skeleton
Skull – protects brain
26 bones of vertebral column – holds body upright and protects spinal cord
Vertebral column – consists of 5 regions: cervical, thoracic, lumbar, sacral, and coccygeal
Rib cage – twelve pairs of ribs plus sternum
Each rib is attached to the vertebral column
Only 7 pair of “true” ribs that are attached to the sternum by cartilage
The other 5 pair “false” ribs do no attach to sternum
Function of rib cage is to protect organs of thoracic cavity

21. Structure of Skeleton…
Appendicular skeleton
126 bones in the pectoral girdle, the pelvic girdle, arms, and legs

22. Structure of Skeleton…
Function of appendicular skeleton
Pectoral girdle – provides support for arms and provides for their broad range of movement
Muscles attach the pectoral girdle to the axial skeleton
Pelvic girdle attaches directly to the lower part of the vertebral column

23. Structure of Skeleton…
Skeletal joints
Joint – any place where two bones come close together
Keeps bones far enough apart so they don’t rub against each other
Holds the bones in place
Six kinds of joints
Pivot, ball-and-socket, hinge, saddle, gliding, and Ellipsoid

24. Structure of Skeleton…
Skeletal Joints
Focus on three
Pivot joint- allows for rotation of one bone around another
Ex: joint of head on neck
Allows head to move up and down as well as side to side

25. Structure of Skeleton…
Skeletal joints, cont.
Ball-and-socket joint- provides for circular motion
Ex: shoulder
Hinge joint – allows movement forward and backward with little side to side
Ex: elbow, knee

26. Structure of Skeleton…
Bones to know
Cranium

27. Structure of Skeleton…
Vertebral column
5 parts
Cervical
Thoracic
Lumbar
Sacral
coccygeal

28. Structure of Skeleton…
Clavicle
Scapula
Humerus
Ulna
Radius
Carpals
Metacarpals
phalanges

29. Structure of Skeleton…
Ribs
Sternum
Femur
Patella
Fibula
Tibia
Tarsals
Metatarsals
phalanges

30. Injuries to Skeleton… Sprain Fracture Dislocation
Ligaments or tendons get torn or pulled beyond their normal stretching range
Painful, yet still able to function
Fracture
A break in a bone
Bone is a living tissue; begins to heal almost immediately
Dislocation
When a bone is forced out of its joint
Can be serious
Bone can usually be pushed back into place by a doctor

31. Review of Skeletal System…
Bones are fastened together by connective tissues called ligaments
Tendons are connective tissues that connect muscles to bone
The skeletal system has 5 important functions: provides shape and support, allows movement, protects tissues and organs, produces blood cells, stores certain materials

32. Review of Skeletal System…
The human skeleton is divided into 2 main parts: the axial skeleton and the appendicular skeleton
Axial skeleton: skull, ribs, breastbone, vertebral column
Appendicular skeleton: pectoral girdle, pelvic girdle, arms and legs

33. Review of Skeletal System…
Cartilage: a flexible connective tissue that supports, acts as a shock absorber, and cushions other skeletal parts
Joint: a place where two bones come close together
Most common injuries to skeletal system
Sprains, fractures, dislocations