Question

Which of the following is the longest bone and also has a deltoid ridge.
a) Radius
b) Ulna
c) Humerus
d) Femur

Answer 1

The deltoid region is the region in the bone where the deltoid muscles attach to the bone. The deltoid and the pectoral ridges are the important points of the muscle attachment to the bones. Their function is to provide attachment of the muscles to the bones.

Complete answer:
The pectoral and the deltoid ridges can be seen on the anterior part of the humerus bone. The humerus is the longest bone present in the forelimb. It usually extends from the shoulder region to the elbow region of the hand. The shaft in the humerus is the location where the attachment of various muscles can be seen easily. If a cross section of this area is taken then one can notice that bone is circular proximally and is flattened distally. The deltoid muscles attach to the bone on the lateral side of the shaft and have a rough surface. This region is known as the deltoid tuberosity. The other muscles which attach themselves to the shaft area of the humerus are coracobrachialis, deltoid, brachialis, brachioradialis, and triceps. If the shaft regions get damaged or get fractured due to some reason then there is a risk of damage to the radial nerve. If the radial nerve gets damaged it may lead to the paralysis in the wrist and such a condition is known as wrist drop.

So, the answer is ‘humerus’.

Note:
The main function of the deltoid region is to provide attachment of the deltoid muscle to the humerus bone. The bone is located in the forelimb and connects the shoulder to the elbow. Damage in the shaft region can lead to loss of sensation in the palms as well as may lead to paralysis of the wrist region of the hand.