Which visceral arch is rudimentary in humans?

 # Which visceral arch is rudimentary in humans?

A. 4th 

B. 5th 

C. 6th

D. 7th

The correct answer is B. 5th.

The pharyngeal arches, also known as visceral arches, are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures.

In the human embryo, the arches are first seen during the fourth week of development. They appear as a series of outpouchings of mesoderm on both sides of the developing pharynx. The vasculature of the pharyngeal arches is known as the aortic arches.

During human, and all vertebrate development, a series of pharyngeal arch pairs form in the developing embryo. These project forward from the back of the embryo toward the front of the face and neck. Each arch develops its own artery, nerve that controls a distinct muscle group, and skeletal tissue. The arches are numbered from 1 to 6, with 1 being the arch closest to the head of the embryo, and arch 5 existing only transiently.

What is the most superior point of the external auditory canal?

 # What is the most superior point of the external auditory canal?

A. Sella

B. Porion

C. Basion

D. Orbitale

The correct answer is B. Porion.

The porion is the most superior point of the external auditory canal. The sella is the center of the hypophyseal fossa. The basion is the most anterior point of the foramen magnum. The orbitale is the most inferior point of the infraorbital rim. 

Which factor requires careful consideration, when taking measurements from an image?

 # Which factor requires careful consideration, when taking measurements from an image? 

A. Definition 

B. Magnification 

C. Reconstruction 

D. Superimposition

The correct answer is B. Magnification.

The magnification factor of any image must be carefully considered when taking measurements. Image definition is significant to the overall diagnosis; however, the magnification factor is of special concern when calculating bone dimensions.  Image reconstruction is largely a function of multiplanar reformatting (MPR).  Superimposition is a factor for some images (panoramic radiographs and conventional tomograms); however, the magnification factor must be carefully considered when calculating bone dimensions. 

The common organism implicated in dry socket is:

 # The common organism implicated in dry socket is:

A. Streptococcus

B. Staphylococcus

C. Treponema denticola

D. Pneumococcus

The correct answer is C. Treponema denticola.

A number of bacteria are known to possess fibrinolytic activity. It has been recently postulated

that Treponema denticola may have an etiological role in the genesis of dry socket.