Skeletal System: Day One Function, Bone Classification, and Bones of the Axial & Appendicular Skeleton

Function of Bones Support Protection Movement ◦ Skeletal muscles attach to bones by tendons Storage ◦ Fat and Minerals (calcium and phosphorus) Blood Cell Formation

Bones give shape to the head, thorax, and limbs. Bones such as the pelvis and lower limbs provide support for the body. Bones of the skull protect the brain, ears, and eyes. 3 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Support and Protection

Body Movement Bones can act as levers. 4 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Blood Cell Formation Blood cells begin to form through hematopoiesis in the yolk sac; they are later manufactured in bone marrow. Two kinds of marrow occupy the medullary cavities of bone. 1. Red marrow functions in the formation of red blood cells, white blood cells, and platelets, and is found in the spongy bone of the skull, ribs, sternum, clavicles, vertebrae, and pelvis. 2. Yellow marrow, occupying the cavities of most bones, stores fat. 5 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Storage of Inorganic Salts The inorganic matrix of bone stores inorganic mineral salts in the form of calcium phosphate that is important in many metabolic processes. Calcium in bone is a reservoir for body calcium; when blood levels are low, osteoclasts release calcium from bone. Calcium is stored in bone under the influence of calcitonin when blood levels of calcium are high. Bone also stores magnesium, sodium, potassium, and carbonate ions. Bones can also accumulate harmful elements, such as lead, radium, and strontium 6 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Classification of Bones 206 bones in adult skeleton Classified by shape ◦ Long ◦ Short ◦ Flat ◦ Irregular Two Basic Types: ◦ Compact ◦ Spongy

Classification by Shape Long ◦ Longer than wide ◦ Shaft with head at both ends ◦ Made mostly of compact bone ◦ All of the bones of the limbs are long bones except the wrist and ankle bones

Classification by Shape Short ◦ Cube-shaped ◦ Made mostly of spongy bone ◦ Bones of the wrist and ankles

Classification by Shape Flat Bones ◦ Thin, flattened, and curved ◦ Two thin layers of compact bone, sandwiching a layer of spongy bone ◦ Most of the bones in the skull, the ribs, and sternum

Classification by Shape Irregular ◦ All bones that are not long, short, or flat ◦ Includes the vertebral and coxal (hip) bones

Two Types of Bone Spongy Bone ◦ Small, needlelike pieces of bone with lots of open space. Compact Bone ◦ Dense; smooth and homogenous

Axial Skeleton Skull ◦ Cranium  Frontal, Parietal, Temporal, Occipital, Sphenoid, and Ethmoid Bones ◦ Facial Bones ◦ Hyoid Bone Vertebral Column (spine) ◦ Cervical Vertebrae (7) ◦ Throacic Vertebrae (12) ◦ Lumbar Vertebrae (5) ◦ Sacrum ◦ Coccyx Bony Thorax ◦ Sternum ◦ Ribs  12 pair ( True Ribs – 7; False Ribs – 5 (2 floating ribs) )

Fetal Skull Different from adult skull ◦ Infant’s face is very small compared to the size of its cranium ◦ Skull as a whole is large compared to the infant’s total body length  Adult skull – 1/8 of total body length  Fetal skull – ¼ of total body length ◦ Some areas of hyaline cartilage still present  Membranes connecting cranial bones are called fontanels  Soft spot  Allow brain to continue to grow  No longer felt after months

Appendicular Skeleton Shoulder Girdle ◦ Clavicle (long bone) ◦ Scapula (flat bone) Upper Limb ◦ Humerus ◦ Radius (thumb side) ◦ Ulna (pinky side) ◦ Carpals ◦ Metacarpals ◦ Phalanges Pelvic Girdle ◦ Coxal bones: ilium, ischium, pubis Lower Limb ◦ Femur ◦ Tibia ◦ Fibula ◦ Tarsal ◦ Metatarsal ◦ Phalanges

Male and Female Pelvis Differences in male and female pelvis aid in childbirth ◦ Female inlet is larger and more circular ◦ Female pelvis as a whole is shallower and the bones are lighter and thinner ◦ Female ilia flare more laterally ◦ Female sacrum is shorter and less curved ◦ Female ischial spines are shorter and further apart ◦ Female pubic arch is more rounded because the angle of the pubic arch is greater