The lymph nodes draining the head and neck are classified into superficial and deep nodes. Superficial lymphatics follow superficial veins while deep lymphatics follow arteries. I. Superficial Nodes: Drain superficial tissues of head and neck. A. Circular Group: Arranged in the form of a circle round the neck called "Pericervical collar". It includes: (a) Submental Nodes: Lie in submental triangle. [...]
Ethmoid bone lies between two orbital cavities, cuboidal in shape. It takes part in the formation of orbit, anterior cranial fossa, roof, lateral wall and septum of nose. Parts: It has three parts: 1. Cribriform plate, 2. Perpendicular plate and 3. Labyrinthine part. At the time of birth bone has three pieces- median plate, right and left labyrinths. 1. Cribriform [...]
The human body has got several mechanisms to combat infections due to pathogenic organisms. It should be realised that many harmless organisms live in symbiosis in our body in the upper respiratory tract, in the lower bowels and in the skin. These may occasionally infect the tissues when the resistance is extremely low or viral infections have devitalised mucosal membrane. [...]