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The esophagus is a muscular and tubular organ and is specifically designed for rapid transport of ingested food and water. As Biological Unit  The six drawings above reflect the contractile and relaxation efforts of the esophagus in order to transport a food and or fluid bolus from the back of the mouth to the stomach. The resting phase in a, shows the UES and LES in basal state with both sphincters contracted. As the food enters the oropharynx from the mouth, the UES relaxes, and the receiving segment of the esophagus just distal to the UES reflexly relaxes as well. (b) In c, the UES contracts behind the bolus and a primary stripping wave are formed that rapidly advances the bolus. Simultaneously the LES relaxes (d). The bolus gets pushed through the LES which subsequently contracts behind the bolus and we are back to the basal state (f). Ashley Davidoff, M.D. TheCommonVein.net
The esophagus’ distinct structural entity allows for the transport of ingested food and water from the mouth to the stomach. Its distinct structural and functional components are essential for proper function. From its sqaumous mucosa, which acts as a protective layer, to its unique muscular anatomy, each separate biologic unit, comprises this important and interesting organ.  The mucosa of the esophagus is relatively thick and is made from a stratified, squamous epithelium. Stratified means that there are multiple layers of cells, and squamous refers to the flat shape of the cells. This is distinctly different to the remaining mucosa of the gastrointestinal tract which in general is made of a single layer of cells that are rectangular in shape. The image above demonstrates the stratified squamous layer and a small portion of the submucosa. Ashley Davidoff, M.D. TheCommonVein.net and Barbara Banner, M.D.  The esophagus is basically a tube as seen in the first image on left, which has the ability to initiate strong contractions (middle image) as well as actively relax. (right image). Ashley Davidoff, M.D. TheCommonVein.net
Links and Connections
The esophagus is connected to the posterior oropharynx at its proximal end and to the stomach on the distal side. It has a complex connection with the nervous system with localized nerve plexi as well as connections to the vagus and central nervous system. The vascular system and lymphatic system are also distinctly connected to the esophagus.  Act as A Valve to Prevent Reflux of Bolus up Nasopharynx teal = nasopharynx, pink = soft palate, maroon = superior constrictors The soft palate elevates, the superior constrictors converge on the soft palate, and food and fluid pass into the oropharynx. Ashley Davidoff, M.D. TheCommonVein.net  The barium swallow shows a normal GE junction. The position of the diaphragm is inferred (marron). Other structures include: salmon = thoracic esophagus light pink = epiphrenic ampulla orange = GE junction purple = region of stomach surrounded by diaphragm light purple = fundus and cardia of stomach Ashley Davidoff, M.D. TheCommonVein.net Units to Unity
The esophagus itself isn’t needed for life, but the organ provides unity to the intestinal system. It provides continuity such that food can enter one end, be processed, and be excreted, albeit in a different form, out the other. Surgery can remove the esophagus and a person can live, and eat, but the unity of the GI system is interrupted and dietary changes needed. Dependence and Independence The esophagus cannot function alone as it requires centrally based innervations and signaling in addition to the receptive relaxation of the muscles to transport food from the oropharynx to the stomach.  The nerve supply to the esophagus is complex from sympathetic and parasympathetic ganglia. Courtesy of: Lippincott Williams & Wilkins However, the esophagus does contain innate sensory neurons that can respond to stimuli, typically distension, that will induce what is referred to as a secondary peristalsis.
Time Growth and Aging At 4 weeks gestation the esophagus grows from endoderm that also gives rise to the respiratory tract. The dorsal component of this endodermal growth, known as the primitive foregut, ultimately yields the esophagus. The dorsal component of this endodermal growth, known as the primitive foregut, ultimately yields the esophagus. As the esophagus ages, coordination becomes lost tertiary waves become more apparent and uncoordinated contractions progress to an entity called presbyesophagus. The loss of coordination with the oropharynx can result in aspiration and aspiration pneumonia becomes a real threat in the elderly. Aspiration pneumonia is not uncommonly a terminal event in the elderly.  As the esophagus ages the primary stripping wave may become weaker and the secondary waves stronger. This leads in some patients to thickening of muscle and results in the corkscrew appearance of the esophagus. Diffuse esophageal spasm may have the same appearance. Ashley Davidoff, M.D. TheCommonVein.net
Space  The CT scan of the upper chest shows the esophagus (yellow) at the thoracic inlet (a) leftward of the trachea (black) and medial to the left subclavian artery (a and b). Lower down the trachea remains medial while the aortic arch becomes an anterior and lateral relation(c). Below the carina, (d) the left main stem bronchus is an anterior and leftward relation while the descending aorta lies lateral. Ashley Davidoff, M.D. TheCommonVein.net The esophagus traverses three spaces in the body. It starts in the neck, has its major position in the chest and has a small component in the abdomen. It is closely related to the spine, aorta, trachea left main bronchus, the left atrium and the diaphragm. Since it does not have a capsule aggressive esophageal disease easily spreads to neighboring structures in the mediastinum.
Forces  The drawing on the left demonstrates the primary stripping wave noted as a constriction above the food bolus. Both the upper and lower sphincters are closed. The primary stripping wave progresses from proximal to distal. The image on the right is from a double contrast barium swallow and it demonstrates the top of the primary stripping wave. Courtesy of: Ashley Davidoff, M.D. TheCommonVein.net Muscular contractions play a key role in the propulsion of a food bolus thru the esophagus. Another key principle that must be remembered is Laplace’s Law which states that the pressure is directly related to the wall tension and inversely related to the radius. The pressure on the wall of the esophagus induces the muscles in the esophagus to contract to help propel the food bolus.
Interactions While it may seem simple, the esophagus interacts with the orophayrnx and stomach at a complex level. The control mechanisms that enable the interaction are quite elegant. Failure of the coordinated mechanisms can be disastrous as seen in reflux esophagitis and aspiration. States of Being Health and Disease Complaints involving the esophagus are quite common. As discussed if other sections, there are a multitude of disorders that can involve the esophagus. Dysphagia, odynophagia, reflux, chest pain, asthma are just a few of the common manifestations of esophageal disorders.  In this barium swallow a stricture in the distal esophagus represents a focal narrowing of the esophagus caused by longstanding reflux esophagitis. The 13mm barium pill shown in the image on the right was not able to pass through this stricture. This finding explains the cause of dysphagia in this patient. Endoscopy is required to ensure the benignity of the stricture. Ashley Davidoff, M.D. TheCommonVein.net  The two images from a single contrast barium swallow show a normal esophagus and GE junction on the left and a dilated esophagus with a hypertonic LES on the right. The appearance of the image on the right is reminiscent of a condition called achalasia. Ashley Davidoff, M.D. TheCommonVein.net  Ashley Davidoff, M.D. TheCommonVein.net  Ashley Davidoff, M.D. TheCommonVein.net
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