The Skeletal System

Introduction The skeletal system is composed largely of a type of connective tissue called BONE Approximately 206 bones make up the adult skeletal system Approximately 275 bones (fetal skeleton – 12 weeks) Cartilage and fibrous connective tissues are also present

Introduction The skeletal system is composed of: Bone: strong, rigid, mineralized (calcium, phosphate) connective tissue Cartilage: strong, flexible, protein (elastic / collagen fibres) connective tissue Fibrous Connective Tissue: strong, flexible, protein (collagen fibres) connective tissue, forms tendons and ligaments

Functions of the Skeletal System Support -Provides a structural framework and points of attachment for tissues / organs (eg.muscles via tendons) Protection - Protects vital organs like the brain and spinal cord Movement – some bones act as levers; results in movement together with skeletal muscles and articulations (joints) Mineral Storage – storage of calcium (Ca) and phosphorus (P) Blood cell production – blood cell production occurs in the red bone marrow (hematopoiesis) Storage of Energy – fats a source of energy

The Skeletal System Parts of the Skeletal System Bone (skeleton) Joints

Bones of the Human Body The skeleton has 206 bones 2 basic types of bone tissue COMPACT BONE - outer structure (solid bone, does not bend easily) SPONGY BONE – inner structure (covers the space where the marrow is stored)

Classification of Bones on the Basis of Shape

Classification of Bones LONG BONES Examples: femur (thing), humerus (arm) SHORT BONES Small cube shaped bones Examples: wrist, ankle, toe bones FLAT BONES Large flat surfaces that cover organs or provide surface for large areas of muscles Examples: skull, shoulder blades, pelvis IRREGULAR BONES Irregular specialized shapes Examples: vertebrae, face SESAMOID BONES Formed in a tendon near a joint Examples: patella (knee cap)

Anatomy of a Bone

Structure of Long Bones A) Epiphysis – end of long bone consisting of outer compact and inner spongy bone filled with red bone marrow B) Articular cartilage – covers epiphysis and facilitates joint movement C) Diaphysis – length of long bone excluding epiphysis (shaft) D) Medullary Cavity – inner hollow cavity along diaphysis containing bone marrow E) Endosteum – inner connective tissue surrounding medullary cavity F) Periosteum – outer connective tissue layer G) Epiphyseal plate – cartilage between diaphysis and epiphysis (growth plate)

Bones of the Skeletal System DIVISIONS OF THE SKELETAL SYSTEM Axial Skeleton (green) – skull, spinal column, sternum, rib Appendicular Skeleton (orange) – hips (pelvic girdle), shoulders (pectoral girdle), limbs

Skull – includes cranial bones, facial bones and mandible

The Spinal Column Consists of 5 sets of vertebrae Cervical : neck (7) Thoracic: midback (12) Lumbar low back (5) Sacrum: (5 fused) Coccyx: tailbone (4 fused) Vertebrae separated by thick disks (cushion the vertebrae and help in movement and flexibility)

Rib Cage: Chest Bones (sternum, ribs) Sternum – aka breastbone 12 pairs of ribs True ribs (7) – joined to spinal column and sternum False ribs (3) – attached to spinal column and 7th rib Floating ribs (2) – do not attach to sternum or other ribs

Shoulder (Pectoral Girdle) Composed of the clavicle (collar bone) and scapula (shoulder blade) These bones allow the upper limb to have free movement

Bones of the Arm Upper Arm Lower Arm Humerus – attaches to scapula Forearm has 2 bones (Ulna and Radius) which attach to the bones at the wrist

Bones of the Hand Carpals (8) Metacarpals (5) Phalanges – finger bones

Hips (Pelvic Girdle) Hip bones (os coxae) Composed of 3 fused bones (ilium, ischium, pubic) Point of attachment for the legs Pubic symphysis – connects both halves of the pelvis in the middle

Bones of the Leg Femur (thigh bone) – longest bone in the body Meets the tibia and fibula at the knee cap (patella)

Bones of the Feet Tarsals Metatarsals – sole Phalanges - toes Ankle bones Largest tarsal is the calcaneus or heel Metatarsals – sole Phalanges - toes