Skeletal System: 206 Bones- Bones Composed of Osseous Tissue (A Type of Connective Tissue)

Skeletal System: 206 bones- bones composed of osseous tissue (a type of connective tissue)

joints- where 2 bones meet

ligaments - connects bone to bone (strong, tough connective tissue)

cartilage- strong, flexible connective tissue

locations 1. articulations- movable joints (provides smooth surface on jt.)

2. need of flexibility: tip of nose

external ear

larynx (voice box)

rib attachment

2 subdivisions: Axial Skeleton: bones that form the longitudinal axis of the body

Appendicular Skeleton: bones of the limbs and girdles

I. Bones: An Overview

A. Functions of Bones

1. Supportive internal framework

bones form internal framework that supports and anchors all soft organs

bones of legs support body torso when standing erect

rib cage supports the thoracic wall

2. Protection of soft body organs

fused bones of skull protect brain

vertebrae protect the spinal cord

rib cage protects the thoracic organs (heart & lungs)

3. Movement using bones as levers

skeletal muscles attached to bones by tendons

bones used as levers to move body and its parts

4. Storage of calcium and phosphorus, etc

fat is stored in the internal cavities of bones

minerals stored in bones......

calcium - needed for 1. neural transmission

2. muscle contraction

3. blood clot formation

hormones control mvmt of Ca to & from bones and blood

phosphorus- part of ATP, nucleic acids, and proteins

5. Hematopoiesis- blood cell formation in red marrow cavities of certain bones

location: usually spongy bone

Red Bone Marrow

Mature and Immature RBC’s, WBC’s, and stem cells

Blood cell formation

Found mainly in flat bones, hips, sternum, skull, ribs, vertebrae, scapula

Yellow Bone Marrow

Fat cells

Energy reserves

Found in the diaphysis of long bones

Classification of Bones

1. Long Bones

Length of the bone exceeds its width

- Humerus, femur

2. Short Bones

Cubelike with roughly equal lengths and widths

- Carpals, tarsals

3. Flat Bones

Thin, flattened, with slight curvature

Compact bones with spongy layer

- Sternum, ribs

4. Irregular Bones

Variety of shapes

Usually connected to other bones

- Vertebrae, pelvis

5. Sesamoid Bones

Short bones that form within tendons

- Patella (the only named sesamoid bone in the body)

- 2 bones under the 1st MP joint

Composition of Bone

-  Specialized cells

-  Matrix consisting of extracellular protein fibers and a ground substance

-  Specialized Connective Tissue

Bone Composition:

2/3 the weight of bone is Calcium Phosphate - Ca3(PO4)2

Calcium Phosphate interacts with calcium hydroxide to form Hydroxyapatite

-  Makes bone hard and resistant to crushing

Mineral amount in bone as a % of the total amount in the body:

Calcium 99% Potassium 4% Sodium 35%

Magnesium 50% Carbonate 80% Phosphate 88%

1/3 is collagen fibers – gives bone strength and resilience

-  Dense fibrous connective tissue

2% is cells

Collagen fibers form an organic framework on which hydroxyapatite crystals form

Bone Cells

Osteoblasts: make the proteins that form the organic matrix of bone and control the mineralization

-  Become surrounded with matrix à osteocytes

Osteocytes: live inside the bone, have long branches which allow communication with each other

Osteoclasts: Resorb bone by secreting acids and enzymes

-  Undergo apoptosis (programmed cell death)

-  Are found in shallow depressions (Howship’s Lacunae) that they have eroded into the matrix

Bone constantly undergoes remodeling (reshaping) to adapt to changing biochemical forces and to remove old, microdamaged bone

Structure of a Long Bone

Epiphysis – the two ends of the bone that are covered by articular cartilage

Diaphysis – the shaft of the bone

Metaphysis – lies between the diaphysis and epiphysis, and is a conical region adjacent to the area where active bone growth occurs

Medullary Cavity (Marrow Cavity) – the central portion of the shaft of many bones, it contains stem cells that produce blood cells

Periosteum – a thin fibrous connective tissue sheath that surrounds the shaft of a bone

Articular Cartilage – hyaline cartilage found on the articular surface of bones

Endosteum - a thin vascular membrane of connective tissue that lines the surface of the bony tissue that forms the medullary cavity of long bone

Compact Bone – dense bone that forms the outer layer of a bone

Spongy Bone – cancellous bone that contains a meshwork of thin trabeculae or spicules of bone tissue, and is found in the epiphysis of long bones

The Osteon

The Osteon: the functional unit of cortical bone

Aka: Haversian System

- Consists of concentric layers of bony matrix surrounding a central

Haversian Canal

-  1691 by English anatomist Clopton Havers

Haversian Canal: contains the blood vessels and nerve supply to the bone

Volkman’s Canals: (Perforating Canals) Lateral branches that carry blood

vessels from one osteon to another

Osteocytes: bone cells

Lucanae: tiny, bony chambers

Canaliculi: cellular processes used to transport nutrients and waste to and

from nearby cells

·  Many osteons cemented together from compact bone

·  The ECM of bone tissue is largely collagen and inorganic salts

Nutrient Foramen: The external opening for the entrance of blood vessels in a bone

*Spongy bone is not arranged in Osteons

Spongy Bone

- Composed of osteocytes and

layers of extracellular matrix but

not arranged around a central canal

trabeculae – small needle-like pieces

of bone

Feedback Control for Blood Calcium

Refer to diagram and textbook page 204-205

*** STUDY THE POWERPOINT NOTES ON BONE GROWTH AND DEVELOPMENT

Bones of the Adult Skeleton

Bones of the Skull

1. Frontal - anterior portion above eyes
2. Parietal - one on each side of the skull, just behind frontal bone
3. Occipital - forms the back of the skull and base of the cranium
4. Temporal - forms parts of the sides and base of cranium
5. Sphenoid - wedged between several other bones in anterior portion of the cranium
6. Maxilla - forms upper jaws
7. Mandible - lower jaws, only moveable bone of the skull

Sutures

1. Coronal - between frontal and parietal bones
2. Lambdoidal - between occipital and parietal bones
3. Squamosal - between temporal and parietal bones
4. Sagittal - between parietal bones

Fontanels - "soft spots" of an infant's skull,
- anterior fontanel, posterior fontanel, sphenoid fontanel, mastoid fontanel

Vertebral Column (strong, flexible rod )

26vertebrae (5 sections)

7 cervical vertebrae Atlas C1 Axis C2

12 thoracic vertebrae

5 lumbar vertebrae

sacrum(fusion of5 sacral vertebrae)

Coccyx(fusion of4 coccygeal vertebra

The Rest of the Bones

Ribs - Thoracic Cage, 12 pairs
- True Ribs - first seven pairs, attach directly to STERNUM by costal cartilage
(Vertebralsternal)
- False Ribs - last five pairs (Vertebralchondral)
- Floating ribs - last two pairs (Vertebral)

Pectoral Girdle: Shoulder. Two clavicles (collar bones) and two scapula (shoulder blade)

Arms: Upper arm - humerus. Lower arm - radius and ulna.
Wrist - 8 small bones called carpals
Fingers - Metacarpals, Phalanges

Pelvic Girdle: Hips. Two large bones called COXAL BONES

Ileum, Ischium, Pubis

Acetabulum

Legs: Upper leg (thigh) - FEMUR. Lower leg - tibia & fibula.
Ankle and Upper foot - 7 bones called TARSALS, `- Talus, Calcaneous, Navicular, 3 Cuneiforms, Cuboid
Largest is the heel bone called the CALCANEOUS
Toes - Metatarsals, Phalanges