1. THE SKELETAL SYSTEM• A skeleton has many functions: – Supports body – Protects soft body parts – Produces blood cells – Stores mineral and fat – Along with muscles, permits flexible body movement• The human endoskeleton is composed of cartilage and bones
– The axial skeleton • Supports the axis of the body and includes the skull, vertebral column, and rib cage.– The appendicular skeleton • Is made up of the bones of the limbs, shoulders, and pelvis.
JOINTS There are 3 types of joints:1. FIBROUS– immovable – Sutures between bones of skull2. CARTILOGENOUS– slightly movable – Connected by hyaline cartilage – Ribs / sternum – Connected by fibrocartilage – Intervertebral discs3. SYNOVIAL – freely movable
TYPES OF SYNOVIAL JOINTS Synovial which means they are freely movable – Bones are separated by a cavity – Tendons help to stabilize the joint – Synovial membrane produces synovial fluid 3 types:permit movement in permit movement in permit onlyall planes one direction only rotationalEx: shoulder joint Ex: elbow movement
Bone StructureBones are complex organs consisting of several kinds oftissues.Bones – Are covered with a connective tissue membrane. – Have cartilage at the ends that cushions the joints. – Are served by blood vessels and nerves.
– The central cavity of a long bone (or diaphysis) • Contains yellow bone marrow, which is mostly stored fat.– The end of a long bone (or epiphysis) • Contains red bone marrow, a specialized tissue that produces blood cells.
Compact Vs Spongy Bones• COMPACT BONE – HARD MATERIAL of the bone – Highly organized• SPONGY BONE – Unorganized appearance (but plates follow lines of stress so spongy bone is strong) – Spaces filled with red bone marrow
Skeletal Diseases and InjuriesThe human skeleton is quite strong andprovides reliable support, but it is susceptible todisease and injury, such as: A. Fracture B. Osteoporosis C. Arthritis
A. Fracture• If a force applied to a bone exceeds its capacity to bend, the result is a broken bone or fracture.• The treatment of a fracture involves 2 steps: 1. Putting the bone back into its natural shape 2. Immobilizing it until the body can repair the fracture – In severe cases, a fracture can be repaired surgically by inserting plates, rods, and/or screws to hold the broken pieces together.
SOME TYPICAL BONE FRACTURES LINEAR SPIRAL COMMINUTED TRANSVERSE COMPOUNDThe fracture is At least one The bone has The fractured is or OPENparallel to the part of the fractured into a at a right angle The skin isbone long axis bone is twisted number of pieces with the bone broken, the axis bone sticks out
B. Osteoporosis• Bones lose mass and mineral content• Leads to an increase risk of fractures
C. Arthritis• Osteoarthritis – Degenerative joint disease (cartilage)• Rheumatoid arthritis – Autoimmune disease – Joints and other tissues are attacked
2. THE MUSCULAR SYSTEM
2. THE MUSCULAR SYSTEM• Pull on bones to produce movements• Skeletal muscles = voluntary movements• Attached to the bone by tendons• 650 human skeletal muscles
Antagonistic pairs of muscles bring aboutmovement in opposite directions
MUSCLE FIBER• One muscle fiber has many myofibrils• Is called striated, because the myofibrils exhibit alternating light and dark bands when viewed with a light microscope.• A sarcomere is the region between two dark, narrow lines called Z lines. It is the unit of contraction
How does a muscle contract?• A myofibril is composed of 2 kinds of filaments: – Thin filaments, made mostly of the protein actin – Thick filaments, made mostly of the protein myosin• A sarcomere contracts – When its thin filaments slide across its thick filaments.
The sliding-filament modelMyosin heads in the thick filaments binds to specificsites on actin molecules in the thin filaments.
Whole Muscle Contraction• In the Body – A motor unit is a nerve fiber together with all the muscle fibers it innervates – As the intensity of nervous stimulation increases, more motor units are activated – Some muscle fibers are contracting while others are relaxing – Even when muscles appear to be at rest, some fibers are always contracting (muscle tone)
Athletics and Muscle Contraction• Exercise and Size of Muscles – Muscles that are not used decrease in size (atrophy) – If stimulation is not restored, muscle fibers are gradually replaced by fat and fibrous tissue – Forceful activity over prolonged period causes muscle to increase in size • Hypertrophy occurs only if muscle contracts to at least 75% of maximum tension • Increase in number of myofibrils within fibers causes hypertrophy
Are all your muscle fibers the same?• What types of exercises can you do? • Aerobic such as running • Anaerobic such as lifting weight• Are their requirements in oxygen the same? NO • Aerobic such as running needs lots of oxygen • Anaerobic doesn’t• They will need different amount of : – mitochondria (remember turns oxygen into energy) – myoglobin (protein that binds oxygen and iron)