Anatomy of the Salivary Glands, Pharynx, Esophagus, and Stomach
Salivary Glands
Submandibular Gland
This gland is located on the underside of the floor of the mouth, surrounding the rear edge of the mylohyoid muscle and resting on its upper surface. The excretory duct, or Wharton’s duct, runs forward under the tongue and empties on each side of the midline.
Sublingual Gland
The smallest of the salivary glands, the sublingual gland sits above the mylohyoid muscle, slightly lateralized. It has several excretory ducts, the most important being the duct of Rivinus. This duct drains in front of Wharton’s duct at the most anterior root of the tongue.
Pharynx
The pharynx is a musculo-membranous tube situated beneath the skull, behind the nasal cavity and mouth, and above the larynx. It lies anterior to the vertebral bodies of the neck. At the level of the sixth cervical vertebra, the pharynx becomes continuous with the esophagus.
As the pharynx is located behind the larynx and nose, it is common to both the digestive and respiratory systems. It opens anteriorly with three holes, communicating with the nostrils, mouth, and larynx. Posteriorly, it is a closed tube. These three holes are:
- Nasopharynx: Connects with the nasal cavity through the posterior nares (nostrils).
- Oropharynx: Connects with the mouth.
- Laryngopharynx: The most posterior part of the pharynx.
The pharynx is wider in its upper part than in its lower part. The transverse diameter decreases as it descends.
Lymphoid Tissue
At the ceiling level of the nasopharynx, we find lymphoid tissue:
- Pharyngeal tonsil: An odd, singular tonsil.
- Tubal tonsil: An even pair of tonsils located in the lateral walls of the nasopharynx, surrounding the opening of the eustachian tube.
The eustachian tube connects the nasopharynx to the middle ear.
Esophagus
The esophagus is a digestive organ located below the pharynx. It is a flattened, musculo-membranous tube, lying anterior to the vertebral bodies of the neck and the trachea. At the level of the sixth cervical vertebra, a small, narrow mouth called the Killiam marks the junction between the pharynx and esophagus. This point lies six inches from the incisors.
The esophagus measures 25 centimeters in length: 5 centimeters in the neck, 17 centimeters in the chest, and 3 centimeters in the abdomen.
Esophagus in the Neck
On each side of the esophagus in the neck lies the carotid sheath, consisting of the internal carotid artery, internal jugular vein, and vagus nerve (tenth cranial nerve). While cranial nerves typically innervate the head and neck, the vagus nerve reaches the abdomen, running close to the internal carotid artery and internal jugular vein.
Esophagus in the Thoracic Cavity
Behind the esophagus in the thoracic cavity, we find the trachea, which eventually divides into the two main bronchi. The vertebral bodies lie behind the esophagus. As the esophagus descends, it passes behind the left atrium of the heart. The esophagus is also related to the aorta, which originates from the heart and forms a curve known as the aortic arch before descending as the descending aorta. The ascending aorta lies to the left of the esophagus, while the descending aorta lies behind it. As the esophagus approaches the diaphragm, the descending aorta moves behind it. Both arteries penetrate the diaphragm: the aorta behind the esophagus. The descending aorta, upon passing through the diaphragm, divides into the thoracic descending aorta and, after traversing the esophagus, the abdominal descending aorta.
Esophagus in the Abdomen
The esophagus travels for about three inches in the abdomen before continuing into the stomach. The junction between the esophagus and stomach is called the cardia.
Stomach
The stomach is an organ found in the abdomen. To divide the anterior abdominal wall into nine regions, we use two vertical lines passing through the nipples, called the midclavicular lines. Another reference is to follow the lateral border of the rectus abdominis muscles.
Horizontal Lines
: a bicostal, joining the most decline the costal margin and the line joining the two biiliac anterosuperiores.La central iliac spines of the first three regions are called epigastrium, to the sides of izquierdo.En right hypochondria and the middle floor is the umbilical region or mesogastrium mesogastrium either side of the flanks or are empty. On the top floor, the central area is called Hypogastrium either side are the right and left iliac fossae.