Skeletal System (cont.) # of bones: Adults 206Adults 206 Babies 300Babies 300
Function of Bones 1.Support for body and organs 2.Protection for the brain, spinal cord, and vital organs 3.Movement levers for muscles 4.Mineral storage – Ca, P 5.Blood cell formation occurs in the marrow of bones
Classification of Bones: Long bones:Long bones: Arm and leg bones Short bones:Short bones: Wrist bones Flat bones:Flat bones: The bones of the skull Irregular bones:Irregular bones: Facial bones or vertebrae
Structure of Bones: Bones are solid networks of living cells and protein fibers that are surrounded by deposits of calcium salts.Bones are solid networks of living cells and protein fibers that are surrounded by deposits of calcium salts.
Compact & Spongy Bone
Dense & strongDense & strong Provides strength & protectionProvides strength & protection Outermost part of the boneOutermost part of the bone Compact Bone:
Less dense & contains bone marrowLess dense & contains bone marrow Found in short, flat, and long bonesFound in short, flat, and long bones Surrounded by compact boneSurrounded by compact bone Spongy Bone:
Structure of Long Bone Figure 6.3a,b
Structure of Long Bone Periosteum- tough layer of connective tissuePeriosteum- tough layer of connective tissue Compact bone- found beneath periosteumCompact bone- found beneath periosteum Haversian canals- network of tubes that run through compact bone & contain blood vessels and nerves.Haversian canals- network of tubes that run through compact bone & contain blood vessels and nerves.
Structure of Long Bone: Spongy bone- ends of long bones & middle of short, flat bones.Spongy bone- ends of long bones & middle of short, flat bones. Adds strength w/o mass! Within bones are cavities that contain a soft tissue called bone marrow.
Structure of Long Bone: Two types of bone marrow:Two types of bone marrow: Yellow bone marrow- made up of fat cells Red bone marrow- produces red blood cells, white blood cells, & platelets
Structure of Long Bone
Bone Cells: Osteocytes- mature bone cells that are embedded in the matrixOsteocytes- mature bone cells that are embedded in the matrix Osteoclasts- break down boneOsteoclasts- break down bone Osteoblasts- produce boneOsteoblasts- produce bone Stop growing- late teens! Our Bones are continuously remodel throughout our lives.
Osteoporosis Osteoclast activity is faster than osteoblast activity!
Development of Bones: Skeleton of embryo almost entirely cartilage:Skeleton of embryo almost entirely cartilage: Cartilage is a type of connective tissue that is made up of a network of protein fibers (both tough collagen & flexible elastin).
Development of Bone Cont’d: Cartilage does not contain blood vessels!Cartilage does not contain blood vessels! Cartilage is replaced by bone during the process called ossification:Cartilage is replaced by bone during the process called ossification: Osteoblasts secrete mineral deposits that replace cartilage with bone. Osteoblasts surrounded by bone tissue – now osteocytes
Growth: Long bones contain growth plates called epiphyseal lines at either endsLong bones contain growth plates called epiphyseal lines at either ends
Growth: Growth of cartilage at these plates causes the bones to lengthen. Gradually cartilage replaced by bone- a.k.a. ossification Late adolescence/ early adulthood growth plates replaced by bone- stop growing! Cartilage in adults found: - nose, external ears, attach ribs to sternum
Bone Connections Joints- place where one bone attaches to anotherJoints- place where one bone attaches to another Classified by movement: Immovable Slightly movable Freely movable Ligaments hold bone to boneLigaments hold bone to bone
Immovable Joints: Allow no movementAllow no movement Bones are interlocked and held together by connective tissue or fusedBones are interlocked and held together by connective tissue or fused Example: skull bones
Slightly Movable Joints: Permit a small amount of restricted movementPermit a small amount of restricted movement Bones are separated from each otherBones are separated from each other Example:Example: Joints between lower leg Joints between adjacent vertebrae
inter- vertebral joints
Freely Movable Joints: Permit movement in one or more directionsPermit movement in one or more directions Grouped according to shapes of the surfaces of the adjacent bones.Grouped according to shapes of the surfaces of the adjacent bones. Ball- and- Socket Joint Hinge Joint Pivot Joint Saddle Joint
Ball-and-Socket Joint: Permits movement in many directionsPermits movement in many directions Allows for widest range of motionAllows for widest range of motion Example:Example: Humerus bone and scapula
ball & socket
Hinge Joint: Permits back and forth motionPermits back and forth motion Example:Example: Femur and tibia/fibula Like open and closing a door!
Pivot Joint: Allow one bone to rotate around another.Allow one bone to rotate around another. Example:Example: Humerus and radius/ulna
Saddle Joints: Permits one bone to slide in two directions.Permits one bone to slide in two directions. Example:Example: Metacarpals with your carpals
Structure of Joints: Cartilage covers the surfaces where two bones come together (protects bones)Cartilage covers the surfaces where two bones come together (protects bones) Joint capsule helps hold bones together & consists of two layers:Joint capsule helps hold bones together & consists of two layers: Ligaments Synovial fluid
Structure of Joints Cont’d: Ligaments- hold bones together in a jointLigaments- hold bones together in a joint Synovial fluid- produced by cells enables surfaces of the joint to slide over each other smoothly.Synovial fluid- produced by cells enables surfaces of the joint to slide over each other smoothly.
Bursitis Inflammation of the bursa (sac)Inflammation of the bursa (sac)
Curvature of the spineCurvature of the spine Scoliosis
Osteoporosis Inefficient bone replacementInefficient bone replacement 5-10% of bone mass lost every 10 years past age of % of bone mass lost every 10 years past age of 40 Rate of bone eating cells exceeds bone building cells!