General Organization of the Head and Neck PDF

General Organization of the Head and Neck  Major Muscle Groups in the Head Muscles of facial expression Muscle of the cheek (buccinators) Occipitofrontalis muscle Muscles of mastication. Attached to bone or fascia and move the skin and change facial expressions. Surround the or...

General Organization of the Head and Neck  Major Muscle Groups in the Head Muscles of facial expression Muscle of the cheek (buccinators) Occipitofrontalis muscle Muscles of mastication. Attached to bone or fascia and move the skin and change facial expressions. Surround the orifices of the mouth, eyes and nose and act as sphincters and dilators to open and close them. The buccinators keep the cheeks taut and aids in chewing. The muscles of mastication are supplied by the mandibular division of the trigeminal nerve (branch of CN V). The Facial nerve (CN VII) supplies the superficial muscle of the neck and chin (platysma), muscles of facial expression, buccinators, muscles of the ear and the occipitofrontalis muscle. Facial Paralysis (Bell’s palsy) Causes?? 1 >>> Idiopathic Injury in wounds, cuts and in child-birth. during surgery on the parotid gland or in disease of the gland. Cold sores and genital herpes (herpes simplex) Chickenpox and shingles (herpes zoster) Respiratory illnesses (adenovirus)  Arterial Supply of the Face Branches of the external carotid artery supply to the face but the facial artery is the major arterial. The pulse of the facial artery can be palpated as the artery winds around the inferior border of the mandible.  Venous Drainage of the Face The facial vein is the major venous drainage of the face and drains into the internal jugular vein. Superficial temporal vein, maxillary vein and other veins form the external jugular vein. Both internal and external jugular veins drain into the subclavian vein.  Fascia of the Neck Structures in the neck are surrounded by a layer of subcutaneous tissue (superficial fascia) and are compartmentalised by layers of deep cervical fascia. The fascial planes determine the direction in which an infection in the neck may spread.  Superficial Cervical Fascia Is a layer of fatty connective tissue that lies between the dermis of the skin and the investing layer of deep cervical fascia. It contains cutaneous nerves, blood and lymphatic vessels, superficial lymph nodes and variable amounts of fat. Anterolaterally, it contains the platysma.  Platysma Is a broad, thin sheet of muscle in the subcutaneous tissue of the neck. It develops from the 2nd pharyngeal arch and is supplied by branches of the facial nerve (CN VII). the platysma helps depress the mandible and draw the corners of the mouthinferiorly.  Anterior Triangle of the Neck Anterior – Mid line Posterior – The anterior border of SCM Superior – Inferior border of the mandible Apex – Jugular notch in the manubrium Roof – Superficial cervical fascia, containing the platysma Floor – Pharynx, larynx, thyroid gland. Subdivisions and Contents Posterior Triangle of the Neck  Blood and Lymph Blood Supply of the Head and Neck The head and neck region receives its blood supply through the Common Carotid Arteries and Vertebral Arteries. Venous Drainage of the Head and Neck region is largely via the Internal Jugular Vein, with the External Jugular Vein and Anterior Jugular Vein draining superficial structures. The Carotid Sheath  Carotid Sheath is a fascial envelope of areolar tissue, which encloses as well as separates the: Common Carotid Artery , Internal Jugular Vein and Vagus Nerve (CN X).  It is found deep to the sternocleidomastoid muscle and is derived from a fusion of: The Prevertebral layer of cervical fascia ▪ Posteriorly The Pretracheal layer of cervical fascia ▪ Anteromedially The Superficial layer of cervical fascia ▪ Anterolaterally  The Carotid Arteries The Right Common Carotid Artery originates from the bifurcation of the Brachiocephalic Trunk behind the right sternoclavicular joint. The Left Common Carotid Artery originates directly from the Arch of the Aorta. Consequently, the left common carotid artery is slightly longer as it courses for about 2cm in the superior mediastinum before entering the neck.  Carotid Sinus The Carotid Sinus is the location of Baroreceptors, which detect changes in blood pressure. The carotid sinus has further clinical relevance as it can be used to Alleviate Supra-Ventricular Tachycardia through gentle rubbing. This is known as a Carotid Massage.  Carotid Body The Carotid Body is the location of Peripheral Chemoreceptors, which detect arterial O2 concentrations. Blood Supply to the Scalp  Scalp supplied largely by branches of the External Carotid Arteries, with the exceptions of the Supratrochlear and Suborbital Arteries, which are branches of the Opthalmic Arteries, which arise from the Internal Carotid Arteries.  Deep lacerations involving the Epicranial Aponeurosis can also cause profuse bleeding, due to the opposing pull of Occiptofrontalis. Loss of blood supply to the scalp does not lead to underlying bone necrosis. The blood supply to the skull is mostly from the Middle Meningeal Artery. Venous Drainage of the Scalp Veins of the Scalp and Dural Venous Sinuse  Blood Supply to Dura and Skull Middle Meningeal Artery runs close to the Pterion of the skull and a fracture at this point can rupture the artery and cause Extradural Haemorrhage. Blood Supply to the Face Venous Drainage of the Face Venous Drainage of the Head External and Internal Jugular Veins Lymphatic Drainage of the Head and Neck  Terminal Group o A.k.a. Deep Cervical Nodes ▪ Receive all the afferent lymph vessels of the head and neck, either directly or indirectly, via one of the regional groups. ▪ Closely related to the Carotid Sheath (Internal Jugular Vein) o Jugulo-Digastric ▪ A.k.a. Tonsillar node ▪ Located just below and behind the angle of the mandible ▪ Lymphatic drainage of tonsil and tongue o Jugulo-Omohyoid ▪ A.k.a. Tongue node ▪ Lymphatic drainage of the tongue, oral cavity, trachea,oesophagus and the thyroid gland  o Deep Cervical Nodes in the Posterior Triangle of the neck ▪ Lie along the course of the Accessory Nerve. ▪ Accessory Nerve may have to be removed in malignancy of the neck o Supraclavicular nodes ▪ Root of the neck ▪ Enlarge in late stages of malignancies of the thorax and abdomen ▪ Virchow’s Node associated with Gastric Carcinoma Lymphadenopathy  Cortex Unstimulated B cells pass out rapidly from the node to return to circulation with the lymph. If activated by antigenic stimulation B cells proliferate and remain in the node.  Paracortex The paracortex contains lymphocytes, accessory cells and supporting cells. The Paracortex is the predominant site for T-Lymphocytes in the lymph node. Medulla The medulla is rich in macrophages and comprises: o Large blood vessels o Medullary cords ▪ Rich in plasma cells ▪ Produced Ab’s pass out of the node via the efferent lymphatic o Medullary sinuses