8th Grade BYOD. Skeletal System

The Human Skeleton

Learning Outcomes

Content: to be able to classify bones according to their shapes

Language: to be able tp describe the function of each category of bones

1 (individual work). Fill in the blanks in the table after reading the paragraph.

The 206 bones that compose the adult skeleton are divided into five categories based on their shapes. A long bone is one that is cylindrical in shape, being longer than it is wide. The term describesthe shape of a bone, not its size. Long bones are found in the arms (humerus (upper arm bone), ulna (arm bone), radius) and legs (femur (thigh bone), tibia (lower-leg bone), fibula (leg bone), as well as in the fingers (hand bones, phalanges) and toes (foot bone, phalanges). Long bones function as levers; they move when muscles contract.A short bone is one that is cube-like in shape, being about equal in length, width, and thickness. The only short bones in the human skeleton are in the bones of the wrists and the bones of the tarsus. Short bones provide stability and support as well as some limited motion.A flat bone is typically thin, it is also often curved. Examples include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones serve as points of joining for muscles and often protect internal organs.An irregular bone does not fit any other classification. These bones have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces. Many facial bones, especially the ones containing channels which contain blood, are classified as irregular bones.A sesamoid bone is a small, round bone that, as the name suggests, is shaped like a sesame seed. These bones form in tendons (the sheaths of tissue that connect bones to muscles) where a great deal of pressure is generated in a joint. The sesamoid bones protect tendons by helping them overcome compressive forces. Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees. The patellae (singular = patella) are the only sesamoid bones found in common with every person.

Bone classification	Features	Function(s)	Examples

2 (individual work). Fill in the blanks by using words and phrases below.

sesamoid

irregular

short

flat

long

ribs

femur

carpals

patellae

face

Bones can be classified according to their shapes. (A)_______ bones, such as the (B)_______, are longer than they are wide. (C)_______ bones, such as the (D)_______, are approximately equal in length, width, and thickness. (E)_______ bones are thin, but are often curved, such as the (F)_______. (G)_______ bones such as those of the (H)_______ have no characteristic shape. (I)_______ bones, such as the (J)_______, are small and round, and are located in tendons.

3 (pair work). Think out of the box!

What are the structural and functional differences between the femur and the patella?