Blogation Numero Dos

The Facial Nerve is the seventh of the twelve pairs of cranial nerves, and it has both motor and sensory roots. It exits the cranium through the stylomastoid foramen and runs anteriorly to the parotid gland where it splits into five terminal branches: temporal, zygomatic, buccal, mandibular, and cervical. The motor root of the facial nerve supplies the muscles of facial expression. The sensory root receives sensation of taste from the anterior two-thirds of the tongue. The facial nerve also supplies parasympathetic fibers to the submandibular and sublingual glands, which can help stimulate the release of more saliva from these two glands.

Injury to the facial nerve and its branches can cause paralysis to the facial muscles on the ipsilateral side. This condition is known as Bell's palsy. The patient will appear to have odd facial expression on one side, that is distorted because of a lack of muscle tone. This paralysis can have ramifications other than lack of muscle control. The loss of control of the orbicularis oris can cause the inferior eyelid to drop, and thus lacrimal fluid cannot inundate the cornea. These leads to a lack of proper hydration and lubrication of the cornea, which make it susceptible to laceration. Such an injury could lead to impaired or lost vision.







The parotid gland is the largest of the three salivary glands. Like the other two glands, the parotid secretes saliva through ducts into the oral cavity to aid in mastication and swallowing. As previously mentioned, the facial nerve travels into the parotid gland where it becomes the parotid plexus of facial nerves and branches to the face. The parotid duct travels from the the parotid gland anteriorly, pierces the buccinator, and enters the oral cavity in order to secrete saliva into the mouth.

The parotid gland may become infected and inflammed by a bloodstream pathogen. Most commonly, this pathogen is the viral agent of mumps. The swelling that results from the inflammation can cause severe pain because the glands expansion is limited by the parotid sheath. The pain is often the worst during chewing because of the increased compression by the mandible and mastoid process. The mumps virus can also lead to inflammation of the parotid duct, which can often be confused with a toothache. Since the parotid gland shares common sensory fibers with the auricular and temporal regions, patients often experience referred pain in those ares from inflammation of the parotid gland.



The cerebral arterial circle or Circle of Willis, is an anastomosis located at the base of the brain that supply blood to the brain. The circle of vessels include: the anterior communicating artery, the anterior cerebral arteries, the internal carotid arteries, the posterior communicating arteries, and the posterior cerebral arteries. Anatomic variation in commonplace in the Circle of Willis. Variation in the size of the vessels is most common, but sometimes certain vessels are absent or duplicated. The resultant size of the vessels from these variations, whether larger or smaller, can become significant if problems in vascular integrity and/or blood flow occur.

In an ischemic stroke, blood flow the certain areas of the brain is decreased (likely due to an embolism), which can lead to deficits in the affected areas. This results in the patient presenting with sudden onset of neurological symptoms. The Circle of Willis can act as a secondary source of circulation if there is an obstruction of a major artery within the circle. By diverting some of its normal flow to the areas not receiving blood because of the obstruction, it can help maintain the function of those tissues. The circle sometimes cannot compensate for the blockage due to the anatomical variation or to the inadequacy of the vasculature in elderly. The other type of stroke that can occur in this anastomoses is a hemorrhagic stroke, cause by the rupture of an artery (known as an aneurysm). This can ultimately lead to large amounts of bleeding into the subarachnoid space, which requires urgent medical attention.

References
Moore et al. "Clinically Oriented Anatomy" (2010) 6th ed
Jonas: Mosby's Dictionary of Complementary and Alternative Medicine. (c) 2005, Elsevier.
http://meded.ucsd.edu/clinicalimg/head_parotitis.htm
http://health.allrefer.com/health/stroke-circle-of-willis.html

Blogation numero uno

The clavicle is a long bone that serves as the connection between the scapula and the sternum. The acromial end of the clavicle articulates with the acromion of the scapula at the acromioclavicular joint, and the sternal end articulates with the sternum at the sternoclavicular joint. The clavicle functions as a movable support for the scapula and upper limb, and it allows a large range of motion of the arm. The clavicle also provides protection for the brachial plexus, as well as the subclavian and axillary arteries. Two aspects which separate it from the other long bones of the body are that it runs horizontally and that it has no medullary cavity.

Fractures of the clavicle are common. The mechanism of injury is usually from an athlete or child extending their arm while falling to the ground. In this case, the impact of the force travels up the bones of the arm and fractures the small long bone (clavicle). In other cases, subjects simply fall directly on their shoulder. Diagnosis of clavicular fracture can be aided by palpating the bone (a fracture should be apparent). An additional sign is the slumping or low-hanging of the upper limb attached to the clavicle. This results from the fracture disabling the trapezius muscle from being able to hold up the entire weight of the limb.



Just lateral to the clavicle lie the muscles of the rotator cuff (scapulohumeral muscles). It  consists of four muscles: the teres minor, subscapularis, infraspinatus, and supraspinatus; which form a muscular cuff around the glenohumeral joint. The rotator cuff acts to stabilize the shoulder, and aids in the rotation and abduction (along with the deltoid) of the humerus. During movements of the shoulder and arm, the contraction of the muscles of the rotator cuff helps hold the head of the humerus in the glenoid cavity of the scapula.

Tears in the tendons of the muscles of the rotator cuff can result from repetitive use of the upper limb above the horizontal (seen in serving a tennis ball or weight-lifting), a sudden strain on the muscles while lifting something heavy, or from blunt trauma to the shoulder. This tearing results in poor functionality of the glenohumeral joint. Overuse of these muscles can also result in degenerative tendonitis. The tendon of the supraspinatus is the most commonly torn, which limits the person's ability to abduct the humerus.






Traveling further distally from the rotator cuff, in the anterior compartment of the arm, lies the biceps brachii. This muscle is made up of two heads which attach to the scapula by their two different tendons. The biceps brachii is capable of action with three joints: the glenohumeral joint, the humeroulnar joint, and the radioulnar joint. With these three joints, the biceps brachii helps supinate or flex the forearm. The short head also helps the shoulder resist dislocation. A membranous sheath, the bicipital aponeurosis, extends from the distal end of the biceps brachii and helps protect the brachial artery and median nerve as they pass through the cubital fossa.

Dislocation or rupture of the tendon of the long head of the biceps brachii can occur from forceful lifting (as in weight-lifting flexion) or can result from prolonged biceps tendinitis. Biceps tendinitis is the result of repetitive use or trauma to the biceps during physical activity (throwing a baseball, swinging a tennis racquet). Anatomically, the rupture or tendonitis of the tendon can result from the wear and tear it can receive if it repeatedly moves through a narrowed intertubecular sulcus of the humerus during physical activity. The rupturing of the tendon of the long head of the biceps brachii is often associated with an audible popping noise.

References:
Moore et al. "Clinically Oriented Anatomy" (2010) 6th ed. 
www.aafp.org
www.myerssportsmedicine.com