The Skeletal System: Functions and Bones

• The skeletal system supports the body and facilitates movement

Functions of the Skeletal System

• Protects internal organs, produces blood cells, and stores/releases minerals and fat
• Cranium protects the brain
• Bones store minerals like potassium that aid muscle contraction, keep skin healthy, and help with normal blood pressure
• Some bones produce red blood cells to carry oxygen to the muscles during physical activity
• Good posture ensures movement efficiency and prevents backache
• The skeleton supports the body in any position, like a crouch when defending

Main Bones of the Skeleton

• Bones include the Cranium, Clavicle, Scapula, Humerus, Ribs, Vertebrae, Radius, Pelvis, Ulna, Carpals, Metacarpals, Phalanges, Femur, Patella, Tibia, Fibula, Tarsals, and Metatarsals

Vertebral Column

• This is known as the spinal column or spine
• It consists of a sequence of vertebrae separated and united by an intervertebral disc
• Together, vertebrae and intervertebral discs form the vertebral column
• It is flexible, supports the head, neck, and body and permits movement
• It also protects the spinal cord, which passes through openings in the vertebrae
• Includes 7 cervical vertebrae (C1-C7) that form the cervical curve, 12 thoracic vertebrae (T1-T12) that form the thoracic curve, and 5 lumbar vertebrae (L1-L5) that form the lumbar curve
• The fused vertebrae of the sacrum and coccyx form the sacrococcygeal curve

Typical Vertebra

• The vertebral column has five regions, with vertebrae in each area named for that region and numbered in descending order
• Vertebrae vary in size and shape within the different regions
• A typical vertebra consists of a body, a vertebral arch, and seven processes

Cervical Vertebrae

• In the neck, there are seven cervical vertebrae designated with the letter "C" followed by its number
• Typical cervical vertebrae differ from thoracic or lumbar vertebrae
• Cervical vertebrae have a small centrum and carry the least weight
• Each transverse process has an opening for arteries that supply the brain with blood

Thoracic Vertebrae

• The 12 thoracic vertebrae are designated T1-T12

Lumbar Vertebrae

• The lower back contains the L1-L5 lumbar vertebrae
• These vertebrae consist of five individual bones forming the spine in the lower back
• These vertebrae carry all the upper body's weight while providing flexibility and movement to the trunk
• They also protect the spinal cord and nerves within their vertebral canal

Sacrum

• It is part of the pelvis, formed by the fusion of five sacral vertebrae

Bone Types

• Long bones like the femur are cylindrical and found in the limbs; used as a lever
• Short bones like carpals are small, compact, equal in length and width, and designed for strength and weight bearing
• Flat bones like ribs have flat surfaces, protect internal organs
• Irregular bones like vertebrae have complex shapes and perform varied functions including protection and muscle attachment

Bone and Cartilage

• The skeleton is made of bone and cartilage
• Both tissues contain material within a matrix of collagen fibers
• The bone matrix consists of collagen fibers hardened by calcium salts
• Bone tissue contains many blood vessels that provide cells with oxygen, nutrients, glucose, and hormones
• Cartilage's material between cells is more flexible and contains no blood vessels

Ligaments and Tendons

• The area where two bones meet is called a joint
• Ligaments and tendons are both connective tissues
• Ligaments have yellow elastin fibers, making them elastic but tough, and connect bone to bone for free movement
• Tendons are made from tough, non-elastic white fibrous protein and connects muscle to bones

Muscles

• Muscles are considered connective tissues containing cells that contract to allow movement
• There are two muscle types: voluntary and involuntary
• Voluntary muscles are also called skeletal or striated muscles, which move when movement is desired and consist of dark bands of fibers that slide over each other during muscle contraction
• Involuntary muscles are also called smooth muscles that are under automatic control because they lack striations