No. 5 1. Pharynx 2. Esophagus 3. Stomach

Section 2 The Pharynx The pharynx is a musculomembranous tube which is used by the digestive system as well as the respiratory system. Location: The pharynx is placed behind the nasal cavities, the mouth and the larynx. It extends from the base of the skull to the level of the sixth cervical vertebra where it becomes the esophagus. The cricoid cartilage marks this change on the front of the neck.

Communications: The pharynx communicates: a. with the nasal cavity through the nares, b. with the oral cavity through the fauces, c. with the middle-ear cavity through the auditory tubes, d. with the larynx through the glottis, e. with the esophagus. Division: For descriptive purposes the pharynx is divided into three parts: nasopharynx, oropharynx, laryngopharynx.

Ⅰ. Nasopharynx (the Nasal Part of Pharynx) Location: The nasopharynx is located immediately behind the nasal cavity and is continuous with it through the two large choanae (nares, posterior nasal apertures). The morphology of the lateral walls of nasopharynx: On its lateral walls, there are pharyngeal openings of auditory tube, through which the nasopharynx receives the auditory tubes that connect the nasopharynx with the cavity of the middle ear.

The pharyngeal opening of auditory tube lies 10～12 The pharyngeal opening of auditory tube lies 10～12.5 mm behind and a little below the posterior end of the inferior nasal concha. The posterior lip of this opening is prominent, due to the underlying cartilage of the auditory tube, and is termed the tubal torus, behind which lies the slit-like pharyngeal recess.

Pharyngeal tonsil and tubal tonsil: A collection of lymphoid tissue, best developed in children, lies in the mucous membrane of the roof and posterior wall of the nasopharynx is known as the pharyngeal tonsil. The lateral prolongation of the pharyngeal tonsil behind the pharyngeal opening of the auditory tube is known as the tubal tonsil.

Ⅱ. Oropharynx (The Oral Part of Pharynx) The oropharynx is a continuation of the nasopharynx, extending from the soft palate to the beginning of the laryngopharynx. It communicates with the oral cavity through the fauces. The oropharynx therefore receives food from the oral cavity and air from the nasopharynx.

Palatine tonsils and lingual tonsils: On the side walls are two palatine tonsils. Embedded in the base of the tongue is an aggregate of lingual tonsils. Tonsilar ring: the palatine tonsil together with the pharyngeal tonsil of the nasopharynx and the lymphoid tissue on the back of the tongue (lingual tonsil) complete a tonsilar ring, but it does not form a strong defense system against the spread of infection from the oral and nasal cavities to the lower respiratory organs.

Ⅲ. Laryngopharynx (The Laryngeal Part of Pharynx) The laryngopharynx extends from the oropharynx above to the esophagus below. Anteriorly it communicates with the cavity of the larynx through the inlet of the larynx. Piriform recess: A small recess, termed the piriform recess, lies on each side of the laryngeal orifice. Foreign bodies may become lodged in this recess.

Section 3 The Esophagus The esophagus is a muscular tube, about 25 cm long, that connects the pharynx with the stomach. Location: it is located behind the trachea. It passes down through the lower part of the neck and the superior and posterior parts of the mediastinum, pierces the diaphragm at the level of the tenth thoracic vertebra, and ends at the cardiac orifice of the stomach. It is a narrowest portion of the alimentary canal except for the vermiform appendix.

Constrictions: The esophagus is constricted at: ① its commencement, 15 cm from the incisor teeth, ② where is crossed by the left bronchus, 25 cm from the incisor teeth, ③ where it passes through the diaphragm, 40 cm from the incisor teeth.

Section 4 The Stomach The stomach (or gaster) is the most dilated portion of the alimentary canal. Shortly after passing through the diaphragm, the esophagus empties into the stomach. Functions: Its function of stomach is to prepare ingested food by mechanical and chemical means for digestion.

Its shape and position are varied from person to person and modified by changes within itself and the surrounding viscera. Capacity: Its mean capacity varies with age, being about 30 ml at birth, increasing gradually to about 800 ml at puberty, and commonly reaching to about 1500 ml in the adult.

Ⅰ. The Morphology of Stomach The stomach presents: two openings, i.e. cardiac and pyloric openings. two curvatures, i.e. greater and lesser curvatures. two surfaces, i.e. anterior and posterior surfaces. four parts, i.e. a cardiac part, a fundus, a body, and a pyloric part.

Ⅰ) Two openings Cardiac orifice: The opening by which the esophagus communicates with the stomach is the cardiac orifice (cardia). It is situated to the left of the median plane, behind the seventh costal cartilage, 2.5 cm from its junction with the sternum, and at the level of the eleventh thoracic vertebra. It is placed about 10 cm from the anterior abdominal wall and 40 cm from the incisor teeth.

Pyloric orifice: The opening into the duodenum is the pyloric orifice (pylorus). Its position is usually indicated by a circular groove on the surface of the organ, which indicates the position of the pyloric sphincter. In the living subject, at operation, it can be identified by the prepyloric vein, which runs vertically across its anterior surface.

Ⅱ) Two curvatures 1. lesser curvature: The right border of the stomach, which is concave, is called the lesser curvature. It extends between the cardiac and pyloric orifices, and forms the right (or posterosuperior) border of the stomach. The most dependent part of the curve may form a notch, named the angular incisure, which separates the stomach into right and left parts.

2. greater curvature: The convex left border is called the greater curvature. It starts from the cardiac orifice at the cardiac incisure to the pyloric orifice. Directly opposite the angular incisure of the lesser curvature the greater curvature presents a bulge, which is the left extremity of the pyloric part of the stomach; this is limited on the right by a slight groove, which indicates the subdivision of the pyloric part into a pyloric antrum and a pyloric canal.

Ⅲ) Two surfaces 1. anterior surface 2. posterior surface

Ⅳ) Four parts Including: the cardiac part, the fundus, the body, the pyloric part.

1. fundus: The part of the stomach to the left of and above the cardiac orifice is called the fundus of the stomach. 2. cardiac part: The parts of the stomach near the cardiac orifice. 3. pyloric part: The part near the pyloric orifice. It includes pyloric antrum and pyloric canal. 4. body: The main portion of the stomach is called the body of stomach. The body of stomach is continuous above with the cardiac part and below with the pyloric part.

Ⅱ. Location and Relations The greater part of the stomach lies in the left hypochondriac, the smaller part of it lies in the epigastric of the abdomen. Ⅱ)Relations The stomach has many important relations.

1. The anterior surface The left part of the anterior surface is posterior to the left costal margin. It is contact with the diaphragm. The upper and left part of this surface becomes posterolateral and is in contact with the gastric surface of the spleen. The right half is in relation with the left and quadrate lobes of the liver and with the anterior abdominal wall. When the stomach is empty, the transverse colon may lie on the front of this surface.

2. The posterior surface The posterior surface is related to the diaphragm, the left suprarenal gland, the upper part of the front of the left kidney, the splenic artery, the anterior surface of the pancreas, the left colic flexure, and the upper layer of the transverse mesocolon. These structures form the shallow stomach bed, but the stomach is separable from them, and can slide over them, due to the intervening omental bursa.

Ⅲ. Musculature and Inner Surface Ⅰ) The musculature of the stomach There are three layers of smooth muscle. The outer longitudinal layer of muscle is best developed along the curvatures and is continuous with the longitudinal muscle of the esophagus and duodenum. The inner circular layer is uniform over the stomach but forms a thickened muscular ring at the pylorus; this is the pyloric sphincter. The stomach also possesses, between the longitudinal and circular layer, an incomplete layer of oblique muscle.

Ⅱ) The inner surface of the stomach The mucosa of the stomach is rather thick and velvety. When the stomach is empty it is thrown into characteristic ridges or rugae. These rugae are most prominent in the body and fundus of the stomach. The mucosa of the pyloric antrum and the canal is smooth. Gastric ulcers and neoplasms distort the mucous pattern and can be detected radiologically.