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

Function of BonesSupportProtectionMovement

◦Skeletal muscles attach to bones by tendons

Storage◦Fat and Minerals (calcium and

phosphorus)Blood Cell Formation

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•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.

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Support and Protection

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Body Movement

Bones can act as levers.

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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.

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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

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Classification of Bones206 bones in adult skeletonClassified by shape

◦Long◦Short◦Flat◦Irregular

Two Basic Types:◦Compact◦Spongy

Classification by ShapeLong

◦ 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 SkeletonSkull

◦ 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 SkullDifferent 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 22-24 months

Appendicular SkeletonShoulder 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, pubisLower 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