Talus

Talus may refer to:

See also

Talus bone

The talus bone (/ˈteɪləs/; Latin for ankle), astragalus /əˈstræɡələs/, or ankle bone is one of the group of foot bones known as the tarsus. The tarsus forms the lower part of the ankle joint through its articulations with the lateral and medial malleoli of the two bones of the lower leg, the tibia and fibula. Within the tarsus, it articulates with the calcaneus below and navicular in front within the talocalcaneonavicular joint. Through these articulations, it transmits the entire weight of the body to the foot.

The second largest of the tarsal bones, it is also one of the bones in the human body with the highest percentage of its surface area covered by articular cartilage. Additionally, it is also unusual in that it has a retrograde blood supply, i.e. arterial blood enters the bone at the distal end.

In humans, no muscles attach to the talus, unlike most bones, and its position therefore depends on the position of the neighbouring bones.

Structure

Though irregular in shape, the talus can be subdivided into three parts.

Talus (fortification)

The talus is an architectural feature of some late medieval castles, especially prevalent in crusader constructions. It consists of a battered (sloping) face at the base of a fortified wall. The slope acts as an effective defensive measure in two ways. First, conventional siege equipment is less effective against a wall with a talus. Scaling ladders may be unable to reach the top of the walls and are also more easily broken due to the bending stresses caused by the angle they are forced to adopt. Siege towers cannot approach closer than the base of the talus, and their gangplank may be unable to cover the horizontal span of the talus, rendering them useless. Furthermore, defenders are able to drop rocks over the walls, which will shatter on the talus, spraying a hail of shrapnel into any attackers massed at the base of the wall.

See also

References

Further reading

 Chisholm, Hugh, ed. (1911). "Talus". Encyclopædia Britannica 26 (11th ed.). Cambridge University Press. p. 386.