# The Human Skeleton **The human skeleton** serves as the supporting structure of our body and as a protection for our organs. The skeleton of an adult consists of ==206 bones== (this can actually vary to up to 212 bones). At birth we have more bones, about 270-300, which fuse together during growth. After the age of ~45 years the size of bones begins to decrease, due to wear and tear. In relation to its weight the human bone is among the most resilient of all known materials. It can withstand double the compressive force of granite and fourth times the tensile force of concrete, due to its unique composition of 66% inorganic and 33% organic materials. "Lively" bones have a pinkish-whitish color. The whole human skeleton (except for joint ends) is covered in "Periosteum" *(dt. Knochenhaut/Periost)*. The human skeleton is formed by two segments: - **==Axial Skeleton==** (80 bones) <font color="grey">*dt. Achsenskelett*</font> - Head - Spine - Rib Cage - **==Appendicular Skeleton==**(125 bones) <font color="grey">*dt. Extremitätenskelett, Gliedmaßenskelett*</font> - Upper Limbs - Lower Limbs - Girdles (Shoulder Girdle / Pectoral Girdle and Pelvic Girdle*) <font color="grey" style="font-size: 13px;">**dt. Schultergürtel und Beckengürtel*</font> The girdles are the connections between appendicular and axial skeletons. > [!info] > **The largest bone** in the body is the femur *("thigh bone", dt. Oberschenkelknochen)* in the leg, which is nearly 50cm long in adults. > > **The smallest bone** in the body is the stapes/stirrup *(dt. Steigbügel, Gehörknöchelchen im Mittelohr)* in the middle ear. It measures roughly 2-3mm. Damage to this bone may cause partial or complete hearing loss. Bones are made up of two types of bone tissue, the **compact** bone tissue and **spongy** bone tissue. Compact bone is the dense outer portion of all bones (everything seen on the outside). It can get quite thick at the shaft of a long bone. Deep in the compact bone is the *"spongy bone"*. The *"spongy beams"* are called *"Trabeculae"*, thus spongy bone is also called *Trabecular bone*.