Skeletal System: Bones, Classification, and Functions

1. The Skeletal System

2. Classification of Bones • 206 bones in the adult skeleton • composed of two basic kinds of osseous tissue that differ in their texture: • Compact bone • looks smooth and homogeneous • Spongy bone • Composed of small trabeculae of bone and lots of open space

3. Bones are further classified on the basis of their relative gross anatomy into four groups • Long bones • Femur • Are much longer then they are wide • Short bones • Carpals and tarsals • Are typically cube-shaped • Flat bones • Bones of the skull • Many are curved • Irregular bones • vertebrae • Bones that do not fall into one of the preceding categories.

4. Two other subcategories of bones (these two types do NOT count in the total 206 adult skeletal bones): • Sesamoid bones • Kneecap • Are small bones formed in tendons • Wormian bones • Tiny bones between cranial bones

5. Five Major Functions • Support -structural framework • Protection -protects soft tissue/organs • Assistance in movement -provides surface for muscles to contract against • Storage of Mineral Salts -calcium and phosphate • Formation of blood cells -blood cell production

6. Long Bone Anatomy • Diaphysis = shaft • Thick collar of compact bone • Center = medullarycavity= bone marrow • Red bone marrow- produces blood cells, is found in the cavities of most bones. • Yellow bone marrow-fat storage.

7. Long Bone Anatomy • Epiphysis = distal and proximal end • Compact bone outside of spongy bone • Articular Cartilage covers the joint surface

8. Long Bone Anatomy • Metaphysis = where diaphysis and epiphysis meet • Contains epiphyseal plate (region of bone growth)

9. Long Bone • Articular Cartilage • Covers joint surface • Hyaline Cartilage • Reduces friction and absorbs shock

10. Long Bone Anatomy • Periosteum • Tough outer covering • (dense irregular connective tissue) surrounding bone.

11. Long Bone Anatomy • PeriosteumContains: • Lymph Vessels • Blood Vessels • Nerves • Provides site for tendon and ligament attachment • Allows for growth in Diameter NOT length • Assists in Fracture repair • Nourishment

12. Long Bone Anatomy • Endosteum • Lines the medullary cavity • Covers trabeculae-meshwork of spaces filled with bone marrow.

13. Basic terms used to identify bone landmarks or surface features: • Process: A broad designation for any prominence or prolongation • Eminence: A raised area • Spine: An abrupt or pointed projection • Trochanter: A large, usually blunt process • Tubercle: A smaller, rounded eminence • Tuberosity: A large, often rough eminence • Crest: A prominent ridge • Head: A large, rounded, articular end of a bone; often set off from the shaft by a neck • Condyle: An oval articular prominence of a bone • Facet: A smooth, flat, or nearly flat articulating surface • Fossa: A deeper depression • Sulcus: A groove • Foramen: A hole • Meatus: A canal or opening to a canal

14. The Axial Skeleton • Divided into three parts: • Skull • Vertebral column • Bony thorax

15. SKULL • The skull is composed of two sets of bones: • Cranium • Encloses and protects the fragile brain • Facial bones • Present the eyes in an anterior position; and • Form the base for the facial muscles

16. Skull cont. • All but one of the bones of the skull are joined by interlocking joints termed sutures • The mandible (lower jawbone) is attached to the rest of the skull by a freely movable joint • Other random bones- • Hyoid bone-”U” shaped; not attached between lower jaw & larynx • Ossicles -”ear bones”- mallus (hammer); incus (anvil); stapes(stirrup)

17. THE CRANIUMPORTION OF THE SKULL • Frontal bone: • Forms the forehead • Parietal bone: • Forms the sides and the major top portion of the cranium, (basically the top of your head) • Temporal bone: • Located above you ears • Occipital bone: • Located at the back of the cranium (the back of you head) • Houses the foramen magnum (your spinal cord starts here) • Ethmoid bone: • Located just inside the eye socket at the top portion of the nasal bone.

18. Facial Bones • SUPERFICIAL FACIAL BONES – Provides areas for the attachment of muscles • DEEPER FACIAL BONES – Separates oral and nasal cavities. Help to form the Nasal septum • CONSISTS OF THIRTEEN BONES FUSED TOGETHER, AND A MOVABLE MANDIBLE. • ONLY ONE BONE, THE VOMER, IS NOT PAIRED-divides the nasal cavity • THE NASAL BONES ARE SMALL BONES THAT FORM THE BRIDGE OF THE NOSE, LATERAL TO THE NASALS ARE THE MAXILLARY BONES. • BELOW THE EYE ORBITS ARE THE ZYGOMATIC BONES (cheek bones). • AT THE BRIDGE OF THE NOSE, LATERAL TO EACH MAXILLA ARE THE SMALL LACRIMAL BONES • THE LOWER JAW BONE IS THE MANDIBLE

22. Vertebral Column • Consists of 24 single bones called vertebrae. • two composite (fused) bones the sacrum and coccyx • connected extending from the skull to the pelvis • Forms the body’s major axial support • Surrounds and protects the spinal cord- allowing the spinal nerves to extend

23. Number of Vertebrae • The 24 single vertebrae are groups as follows: • Cervical Vertebrae • 7 bones • Forms a concave shape • Commonly termed “NECK” • Thoracic Vertebrae • 12 bones • Forms a convex shape • Connected to the ribs • Lumbar Vertebrae • 5 bones • Forms a concave shape • Supports the lower back

24. LETS NOT FORGET THE SACRUM AND COCCYX • Sacrum • 5 FUSED bones • Forms a convex shape • Coccyx • 3-5 FUSED bones • Termed the tailbone. • It is attached to the sacrum by ligaments

25. Cervical Vertebrae • Seven bones • Referred to as C1-C7 • The first two cervical vertebrae termed • Atlas (C1) • Lacks a body • Allows you to nod ‘YES’ • Axis (C2) • Acts as a pivot for the rotation of the atlas and skull • Allows you to rotate your head to indicate “NO”

26. Cervical C3-C7 • Distinguished from the thoracic and lumbar vertebrae by several features: • They are the smallest; • Lightest; and • Triangular • They have foramina (holes) to allow blood vessels to go through.

27. Thoracic Vertebrae • 12 bones • Referred to as T1-T12 • Have larger body • Spinous process are long with a sharp downward hook

28. Lumbar Vertebrae • Five bones • Termed L1-L5 • Have massive block like bodies and short thick hatchet-shaped spinous processes

29. Intervertebral Disk • Vertebrae are separated by pads termed “fibrocartilage’ • Cushion the vertebrae and absorb shocks • Aging causes the water content of the discs to decrease and become thinner and less compressible. • Herniated disc- common back injury.

30. Vertebral Column Abnormalities:

31. Thoracic Cage • AKA- “RIBCAGE” or “BONY THORAX” • Forms a protective cone-shaped enclosure around the organs of the thoracic cavity • Heart; lungs; and major arteries/veins • Composed of the following: • The sternum • Ribs • Thoracic vertebrae

32. Sternum • AKA-“BREASTBONE”-flat • Is a fusion of three bones: • Manubrium • Top • Looks like a knot of a tie • Connects to the clavicle (collarbone) • Body • Middle • Forms the bulk of the sternum • Xiphoid process • Pointed tip • Can easily break with a strike or during CPR and can penetrate the heart or liver • Is attached to the first seven pairs of ribs

33. The sternum has three important bony landmarks • Jugular notch • Located on the manubrium • Is concave, you can feel it TRY TO FIND YOURS! • Sternal angle • Is where the manubrium and body join • You can also feel this too!! • It starts at the second rib • (DO NOT WRITE)so doctors use this to count ribs before placing needles into the body or to listen to heart valve

34. Rib Cage

35. Individual Rib • 12 pairs of ribs • All the ribs connect to the thoracic vertebrae • TRUE RIBS • First 7 ribs • Attached directly to the sternum • FALSE RIBS • Next five ribs • Attach indirectly to the sternum or lack a sternal attachment via cartilage) • Ribs 8-10 connect via cartilage to sternum • FLOATING RIBS • Last two pair of ribs • no sternal attachment