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The Digestive System ● The digestive system is divided into the digestive tract (Gastro-Intestinal Tract ~ GIT) and the associated digestive glands. ● The digestive tract include, mouth opening & oral cavity, pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), and large intestine (cecum & appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum , anal canal and anus). ● The associated digestive glands are; salivary glands, liver, gall bladder and pancreas ● The main functions of digestive system are; the digestion and absorption of food stuff required for normal body build and function, secretion of enzymes & hormones, and the excretion of waste undigested products. General Histological Structure of Digestive Tract ● The wall of digestive tract from inside outward consists of four layers; mucosa, submucosa, muscularis and adventitia or serosa with some regional variations. ● The mucosa or mucus membrane comprises; epithelial lining, lamina propria and muscularis mucosae. The epithelium from mouth cavity down to esophagogastric junction is non-keratinized stratified squamous, simple columnar from stomach to anal canal, and stratified squamous along the anal canal. The lamina propria is loose areolar connective tissue containing glands, blood vessels, lymphatic follicles & vessels and nerves. The muscularis mucosae consists of inner circular and outer longitudinal layers of smooth muscles and help to change the shape of lining epithelium. ● The submucosa is a connective tissue layer containing glands, blood vessels, lymphatic follicles and autonomic nerve plexuses called submucosal or Meissner’s plexuses which supply muscularis mucosae. ● The muscularis layer from oral cavity to about the middle of esophagus consists of skeletal muscles, while below, it consists usually of two smooth muscle layers; inner cirular and outer longitudinal ( in the stomach there is an innermost oblique layer), and contains autonomic nerve plexuses called myenteric or Auerbach’s plexuses. ● The fibrosa is a thin layer of dense connective tissue with blood & lymphatic vessels and nerves. In the abdominopelvic cavity, it is called serosa lined by an epithelial layer of simple squamous epithelium (mesothelium) which constitute visceral layer of peritoneum. The Mouth Opening & Mouth Cavity ● The mouth opening (labial or oral fissure) lies between the two lips & leads into the oral cavity. ● The mouth cavity is divided into a small vestibule and a larger mouth cavity proper which are continuous with each other behind the last molar teeth when the jaws are closed. The Vestibule ● The vestibule lies anterior to dental arch and bounded by the lips and cheeks. ● Each lip consists of skin, fascia, orbicularis oris muscle and the facial muscles at the angle of mouth. It is lined internally by moist mucuse membrane (non-keratinized stratified squamous epithelium). In the middle of upper lip skin there is a depression called philtrum. The inner epithelium of each lip is reflected on the gums, and in the middle there is upper & lower labial frenulum (if tight and thick, they interfere with speech during childhood). ● Each cheek is formed by the skin, fascia, buccal pad of fat, buccinator muscle and mucus membrane (non-keratinized stratified squamous epithelium). ● The parotid duct pierces buccinator muscle and opens into the vestibule by a small papilla opposite 2nd upper molar teeth. This area is the site where the first vesicular eruption of measles is found (Koplic spot). ● The sensory nerve supply of upper lip is by infraorbital nerve of maxillary division of trigeminal nerve (5th cranial nerve) and the buccal nerve of mandibular division of trigeminal nerve. The mucus membrane of upper gum is supplied by superior alveolar branch of maxillary nerve. ● The sensory nerve supply of lower lip is by the mental and buccal nerves from mandibular division of trigeminal nerve. The mucus membrane of lower gum is supplied by inferior alveolar branch of mandibular nerve. ● The muscles of both lips are supplied by branches of facial nerve. ● The sensory supply of the skin and mucus membrane of cheeks is by buccal nerve from mandibular nerve. The motor supply is by facial nerve. ● The blood supply of lips and cheeks is by branches of facial and maxillary vessels, and their lymphatic vessels are drained into submandibular lymph nodes. Mouth Cavity Proper ● Much larger than the vestibule, bounded anteriorly and laterally by dental arches of maxillae and mandible, superiorly (roof) by the palate, and inferiorly (floor) by the anterior two thirds of tongue. ● Continuous posteriorly with oropharynx at oropharyngeal isthmus or isthmus of Fauces bounded by the two palatoglossal arches. ● It contains: teeth, anterior two thirds of tongue, sublingual glands in its floor, and the openings of submandibular and sublingual glands. ● On the under surface of tongue there is a median mucosal fold called frenulum of tongue (if thick and short it interferes with normal speech and requires surgical excision). Lateral to frenulum, the lingual artery, lingual nerve and deep lingual vein are located under mucosa in order from medial to lateral. The deep lingual vein can be seen through the illuminated mouth cavity. Just lateral to the vein there is a fold of mucosa called plica fimbriata. ● Lateral to the root of the frenulum of tongue, there are two horizontal sublingual mucosal folds formed by the bulging of sublingual glands. The multiple openings of sublingual ducts are located along the sublingual folds. The openings of submandibular ducts lie on the sides of the root of lingual frenulum. ● The mucosa of mouth cavity is lined by non-keratinized stratified squamous epithelium. The submucosa contains small salivary glands which open directly into oral cavity. ● The sensory nerve supply of mucus membrane of hard palate is by greater palatine and nasopalatine nerves from maxillary division of trigeminal nerve. The sensory nerve supply of soft palate is by glossopharyngeal nerve. ● The sensory nerve supply of floor of mouth is by lingual & buccal branches of mandibular division of trigeminal nerve. ● The arterial supply of palate is by the branches of maxillary artery (greater palatine, lesser palatine & sphenopalatine arteries), ascending palatine branch of facial artery & palatine branch of ascending pharyngeal artery. The floor of mouth cavity is supplied by branches of lingual artery. ● The venous drainage is into corresponding veins ● The lymphatic drainage is into the deep cervical nodes via submandibular lymph nodes. The Teeth ● The deciduous teeth of childhood are 20; 4 incisors, 2 canines, and 4 molars in each jaw. The first eruption starts at 6 months usually in lower jaw and are all completed by the age of 2 years. ● The permanent teeth are 32: 4 incisors, 2 canines, 4 premolars and 6 molars in each jaw. The last molar teeth are usually erupted by the age 17-30. ● Each permanent tooth consists of root and crown which join together at the cervix of tooth. ● The root or roots are embedded in their sockets in alveolar part of mandible and maxilla covered by mucus membrane (gingiva or gum). The root centrally has the pulp connected below with the root canal for nerves and vessels and immediately surrounded by hard dentin. External to dentine is much harder cementum which is bounded to alveolar bone by strong periodontal ligament . ● The crown projects from the root into mouth cavity and consists of inner dentin and outer enamel. The Tongue ● A mass of skeletal muscles covered by mucus membrane, located in oral cavity and oropharynx, and attached by its muscles to the styloid process of the base of skull, mandible and hyoid bone. The right & left halves of tongue are connected together by a median fibrous septum. ● Divided by the V-shaped sulcus terminalis into the anterior 2/3 located in mouth cavity proper, and posterior 1/3 located in oropharynx. The apex of sulcus terminalis points posteriorly and has a pit representing the embryonic foramen cecum, the site where thyroglossal duct descends with thyroid gland from pharynx to the neck. ● The mucus membrane on the dorsum of anterior 2/3 of tongue is rough due to the projections of lamina propria under the epithelium forming many papillae. ● The mucous membrane on the dorsum of posterior 1/3 has many elevations produced by lymphatic follicles (lingual tonsil). The mucus membrane on the inferior surface of whole tongue is smooth and continuous with mucus membrane of lower gum and oropharynx. ● The epithelium covering the tongue is non-keratinized stratified squamous epithelium, below it lies the lamina propria. The lamina propria tightly binds the underlying muscles to the mucus membrane. The submucosa contains several small mucus and serous glands whose ducts open on the surface of tongue. ● The papillae of the dorsum of anterior 2/3 of tongue are of three types; filliform, fungiform and circumvallate. The foliate papillae are not present in human tongue. ● The filliform papillae are elongated conical-shaped widespread on the dorsolateral areas, and contain no taste buds. ● The fungiform papillae are large mushroom-shaped with narrow stalk and contain taste buds. ● The circumvallate papillae are large circular-shaped, 7-11 in number located anterior to sulcus terminalis and contain taste buds. They are surrounded by circular groove which has the openings of the ducts of small lingual serous glands (Von Ebner’s glands) whose secretion help to dissolve the tastants which stimulate the taste buds. Also the lingual glands secret lipase enzyme which prevents the formation of hydrophobic lipid substances on the surface of taste buds which interferes with action of taste buds, and it also helps to digest fat in the stomach. ● Each taste bud is onion-shaped collection of about 50-100 cells which rest on the basement membrane and emerge on the surface through the taste pore. It consists of taste cells, supporting cells and basal proliferative cells. The apices of taste cells have microvilli which have receptors for the tastants (sour and sweet tastants) or open ion channels (bitter and salt tastants) which eventually leads to depolarization of taste cells and the release of neurotransmitters. These events will stimulate special taste sensory nerve endings and the sensation is carried to special neurons in the brain. Muscles of Tongue: ● Are intrinsic and extrinsic skeletal muscles. ● The intrinsic muscles run in different directions and include; vertical, transverse and longitudinal. They originate from tongue connective tissue and median fibrous septum and insert into the mucosa. They are supplied by hypoglossal nerve (12th cranial nerve), and help in changing the shape of tongue. ● The extrinsic muscles include; genioglossus, hyoglossus, styloglossus and palatoglossus. Their origin, insertion and action is shown in the following table: Nerve Supply of Tongue: ● All intrinsic and extrinsic muscles of tongue except palatoglossus are supplied by hypoglossal nerve. The palatoglossus is supplied by pharyngeal plexus. ● The sensory nerve supply is as follow: Anterior 2/3: General sensations (touch, pressure, pain & temperature) by lingual nerve from V3 of trigeminal nerve. Special taste sensation excluding the taste sensations from the circumvallate papillae is by the chorda tympani branch of facial nerve. Posterior 1/3: General sensation is by glossopharyngeal nerve and a small posterior area near epiglottis is by internal laryngeal branch of vagus nerve. Special taste sensation including the circumvallate taste buds is by glossopharyngeal nerve. ● The lingual glands are supplied by autonomic nerves. The postganglionic parasympathetic nerves is from submandibular ganglion via lingual nerve (preganglionic are from chorda tympani of facial nerve. The postganglionic sympathetic nerves is from superior cervical sympathetic ganglion along the lingual artery (preganglionic is from upper thoracic sympathetic ganglia) . Movements of Tongue: ● The intrinsic muscles change the shape of tongue ● Protrusion of tongue out of mouth is by genioglossus and hyoglossus of both sides. ● Depression is by hyoglossus muscle ● Retraction and elevation is by styloglossus and palatoglossus muscles. Blood supply and Lymph Drainage of Tongue ● Arteries of tongue: lingual artery, tonsillar branch of facial artery, ascending pharyngeal artery. ● Veins of tongue: corresponding veins to internal jugular vein ● Lymph drainage: Anterior 2/3: from tip of tongue to submental lymph nodes from the rest to submandibular lymph nodes and upper deep cervical nodes (jugulodigastric) of both sides. Posterior 1/3: to upper deep cervical nodes on both sides. Salivary Glands Three pairs; parotid, submandibular and sublingual , located in the region of head & neck around oral cavity. They secret saliva into oral cavity via their ducts. Additional small salivary glands exist in the mucosa & submucosa of palate, mouth cavity and pharynx. The saliva contains water, electrolytes, mucus, amylase and IgA produced by the plasma cells of connective tissue. The IgA taken by secretory cells will be secreted combined to their product. Parotid Gland ● The largest one located anterior and below the auricle on the ramus of mandible. ● Extends from external auditory meatus above to the upper part of the side of neck on the sternomastoid muscle. ● Has a fibrous capsule and a fascial sheath derived from the investing layer of deep fascia of neck. ● Its shape is irregular, wedged between the ramus of mandible, masseter anteriorly and mastoid process and sternomastoid posteriorly. ● The facial nerve passes within the gland and divides it into superficial and deep parts. ● The parotid duct (Stensen’s duct) emerges from the superficial part, crosses over masseter, pierces buccinator muscle and overlying fat & fascia to open into mouth vestibule opposite the 2 nd upper molar tooth. ● The parotid gland has 4 extensions or processes which include; ♣ glenoid process behind the temporomandibular joint. ♣ pterygoid process between medial pterygoid muscle and mandible. ♣ facial process over the masseter muscle. ♣ accessory parotid gland (detached part of the gland over the masseter). ● Strucures passing within the gland from superficial to deep are: ♣ Facial nerve ♣ Retromandibular vein with its tributaries and divisions (maxillary and superficial temporal veins, anterior & posterior divisions) ♣ External carotid artery and its two terminal branches (maxillary & superficial temporal arteries). ♣ Also lying within the gland are the deep parotid lymph nodes. Relations of Parotid Gland: Superiorly: temporomandibular joint and external auditory meatus. Superficially: parotid fascia, parotid lymph nodes & great auricular nerve. Anteromedially: temporomandibular joint, ramus of mandible, masseter & medial pterygoid muscle Posteromedially: mastoid process, sternomastoid, posterior belly of digastric and stylohyoid muscles, carotid sheath containing internal carotid artery, internal jugular vein & vagus nerve, and the facial, glossopharyngeal, accessory and hypoglossal nerves. Nerve Supply of Parotid Gland: ● The skin & fascial sheath of parotid gland are supplied by great auricular nerve from cervical plexus. ● Postganglionic parasympathetic nerves are derived from the otic ganglion and reach the gland via auriculotemporal nerve. The preganglionic parasympathetic nerves to otic ganglion is from lesser petrosal nerve of glossopharyngeal nerve. ● Postganglionic secretomotor sympathetic nerves are from the superior cervical sympathetic ganglion via plexus on external carotid artery. Blood Supply & Lymphatic Drainage of Parotid Gland Arteries: branches from external carotid, maxillary & superficial temporal arteries. Veins: retromandibular vein. Lymph drainage: parotid lymph nodes & deep cervical lymph nodes. Histology of Parotid Gland ● Classified as compound acinar gland, purely serous secrets saliva rich in amylase for digestion of carbohydrates in oral cavity. ● The fibrous capsule sends septa which divides the gland into lobules. ● The acini are lined by pyramidal-shaped cells, the nucleus is located in the lower part of cells with all features of protein synthesizing cells (prominent Golgi complex, rich rER and many secretion granules at the apices ● The myoepithelial cells are contractile cells of epithelial origin located below the basal membrane of acinar cells and help in evacuating the content of acinar lumen (usually 2-3 cells in each acinus. ● The duct system begins at intercalated ducts which are tiny and lined by simple cuboidal epithelium with myoepithelial cells. ● The intercalated ducts join together and form the striated ducts lined by simple columnar cells which show basal striations due to the enfolding of basolateral cell membrane. Under EM, the cells have features of ion transporting cells with many elongated mitochondria. ● The striated ducts join together and form interlobular ducts. (The intercalated & striated ducts are intralobular ducts) ● The interlobular ducts are lined initially by stratified cuboidal then by stratified columnar epithelium with goblet cells. ● The main duct is lined with non-keratinized stratified squamous epithelium. Submandibular Gland ● The 2nd largest salivary gland located in the neck, deep to the body of mandible (in the submandibular fossa), and separated from parotid gland by the stylomandibular ligament. ● Has fibrous capsule and invested by a sheath of fascia from investing deep fascia of neck. ● It consists of a large superficial part and a smaller deep part which are continuous with each other at the posterior border of mylohyoid muscle. ● The submandibular duct (Wharton’s duct) emerges from the deep part and runs anteriorly on hyoglossus muscle and then between sublingual gland and genioglossus muscle to open in the floor of mouth cavity proper by a small papilla at the side of the frenulum of tongue. Relations of Superficial Part: Anteriorly: anterior belly of digastric muscle. Posteriorly: posterior belly of digastric and stylohyoud muscles. Laterally: superiorly is the medial surface of body of mandible, while inferiorly are the investing deep fascia of neck, submandibular lymph nodes, platysma muscle, cervical branch of facial nerve and the facial vein. The facial artery indents the posterosuperior part of gland. Medially: mylohyoid and hyoglossus muscles, deep part of submandibular gland, and the lingual and hypoglossal nerves. Relations of Deep Part: Anteriorly: sublingual gland. Posteriorly: posterior belly of digastric and stylohyoid muscles. Medially: hyoglossus and styloglossus muscles. Laterally: superiorly is the body of mandible (sublingual fossa), while inferiorly are the mylohyoid muscle & superficial part of gland. Superiorly: lingual nerve, submandibular ganglion and mucus membrane of mouth. Inferiorly: hypoglossal nerve. Nerve Supply of Submandibular Gland ● Sensory nerves are derived from lingual nerve ● Postganglionic parasympathetic nerves are from submandibular ganglion via branches of lingual nerve. The preganglionic parasympathetic of submandibular ganglion are derived from the facial nerve via chorda tympani ● Postganglionic sympathetic nerves are from superior cervical sympathetic ganglion from the plexus on facial & lingual arteries. Blood Supply & Lymph Drainage of Submandibular Gland ● Arteries: from facial & lingual arteries. ● Veins: into the corresponding veins. ● Lymph drainage: to submandibular and deep cervical lymph nodes. Histology of Submandibular Gland ● Classified as compound tubuloacinar and mucoserous (mixed gland). ● The gland is divided into lobules by fibrous septa extending from its fibrous capsule. ● The duct system resembles that of parotid gland but the intercalated ducts are short and not frequently seen in LM sections. ● The secretory part of the gland include serous acini, mucus tubules with serous demilunes. ● The serous acini resembles those of parotid gland, the mucus tubules are lined by cells full of mucin protein so appears pale under LM. ● The serous demilunes are located in the periphery of mucus tubules. The serous cells also secrets lysozymes which destroys bacterial wall. Sublingual Gland ● The smallest pair of salivary glands located in the floor of mouth cavity under the tongue. ● It raises a transverse sublingual fold of mucosa in the floor mouth, and its ducts are 8-20 in number and open on the summit of sublingual papilla. ● A major sublingual duct (Bartholin duct) also joins the submandibular duct. Relations of Sublingual Gland: Anteriorly: the opposite sublingual gland. Posteriorly: the deep part of submandibular gland Laterally: body of mandible (sublingual fossa of mandible). Medially: genioglossus, submandibular duct & lingual nerve Superiorly: mucus membrane of mouth. Inferiorly: mylohyoid muscle. Blood Supply of Sublingual Gland: Arteries: branches from facial & lingual arteries. Veins: into the corresponding veins. Lymph Drainage of Sublingual Gland: Into the submandibular & deep cervical lymph nodes. Nerve supply of Sublingual Gland: ● Sensory nerves are derived from lingual nerve. ● Postganglionic parasympathetic from submandibular ganglion via lingual nerve. The preganglionic to submansibular gaglion are from chorda tympani of facial nerve. ● Postganglionic sympathetic nerves are from superior cervical sympathetic ganglion via plexus on the arterial supply. Histology of Sublingual Gland: ● Classified as compound tubuloacinar gland formed exclusively of mucus cells with very few serous cells forming the demilunes. ● The serous cells secrets lysosomal enzymes which kills bacteria in oral cavity. ● The duct system is similar to other salivary glands but the intercalated and striated ducts are not well developed. The Palate ● It lies between nasal cavity and nasopharynx above and the oral cavity below. It consists of anterior hard palate and posterior soft palate. ● The hard palate is formed by palatine processes of maxillae and horizontal plates of palatine bones strictly covered by mucus membrane which has few small glands. The mucus membrane is respiratory one on its upper surface while of oral type inferiorly ● The soft palate is a soft mass arises from the posterior border of hard palate and has a free posterior border which projects into the oropharynx with a small muscular projection in its middle called uvula. ● The soft palate consists of; mucus membrane, palatine aponeurosis, mucus glands, muscles with nerves, blood and lymphatic vessels. ● The epithelium is respiratory on the upper surface while oral on lower surface. ● The mucosa and submucosa contains mucus and serous glands. ● The palatine aponeurosis is a sheet of dense fibrous tissue and is formed by the extension and union of the tendons of tensor palati muscles. ● The muscles of soft palate are; levator palati, tensor palati, palatoglossus, palatopharyngeus and musculus uvulae. Their attachment, nerve supply and action is shown in the following table: Muscles of Soft Palate Muscle Origin Insertion Action Nerve Supply Nerve to medial Spine of sphenoid & Form palatine Tensor Veli Palatini Tenses soft palate pterygoid from auditory tube aponeurosis mandibular nerve Petrous part of pharyngeal plexus Levator Veli Platini temporal bone & Palatine aponeurosis Raises soft palate auditory tube Pulls root of tongue upward Palatine Palatoglossus Side of tongue & backward, narrows pharyngeal plexus aponeurosis oropharyngeal isthmus Palatine Posterior border of Palatopharyngeus Elevates wall of pharynx pharyngeal plexus aponeurosis thyroid cartilage Posterior border of Mucus membrane of Musculus Uvulae Elevates uvula pharyngeal plexus hard palate uvula Nerve Supply of Palate: ● Sensory nerve supply of hard palate is by the lesser palatine, greater palatine and nasopalatine branches of maxillary nerve, while that of soft palate is by branches of glossopharyngeal nerve. ● The motor supply of all palatine muscles except tensor palati is by pharyngeal plexus (from cranial accessory nerve via vagus). The tensor palati is supplied by nerve to medial pterygoid from mandibular nerve. ● The pharyngeal plexus lies on posterior pharyngeal wall and formed by: pharyngeal branch of vagus (its motor content is derived from cranial accessory nerve) pharyngeal branch of glossopharyngeal nerve pharyngeal branches of superior cervical sympathetic ganglion Blood Supply of Palate: Arteries: branches of maxillary artery (greater palatine, lesser palatine & sphenopalatine) ascending palatine branch of facial artery palatine branch of ascending pharyngeal artery Veins: corresponding veins into maxillary, facial & pharyngeal veins Lymph Drainage: into deep cervical lymph nodes. The Pharynx ● Muscular tube lies behind oral, nasal and laryngeal cavities. ● 12-13 cm long extends from base of skull to the level of lower border of 6th cervical vertebra (lower border of cricoid cartilage) where it continues with esophagus. ● Its wall is formed by mucosa, submucosa, muscles and fibrous tissue. The mucosa epithelium is non-keratinized stratified squamous in oro- and laryngopharynx, while it is columnar ciliated in nasopharynx. The submucosa contains mucus glands and lymph follicles. ● The muscles of pharynx are skeletal muscles and include: superior, middle and inferior constrictors, cricopharyngeus, stylopharyngeus, palatopharyngeus and salpingopharyngeus. Their attachment, nerve supply and action is listed in the following table: Muscles of Pharynx Origin Insertion Action Nerve Supply Superior constrictor Medial pterygoid plate, Pharyngeal tubercle of Swallowing Pharyngeal plexus pterygoid hamulus, skull and pharyngeal pterygomandibular raphe, raphe posterior part of mylohyoid line of mandlble Middle constrictor Lower part of stylohyoid Pharyngeal raphe Swallowing Pharyngeal plexus ligament, greater and lesser cornu of hyoid bone Inferior constrictor Thyroid and cricoid cartilages Pharyngeal raphe Swallowing Pharyngeal plexus, branches from external laryngeal and recurrent laryngeal nerves Cricopharyngeus Lowest part of inferior Sphincter of the Pharyngeal plexus, constrictor end of pharynx recurrent laryngeal nerve Stylopharyngeus Styloid process of skull Posterior border of thyroid Elevates pharynx Glossopharyngeal cartilage nerve Palatopharyngeus Palatine aponeurosis Posterior border of thyroid Elevates pharynx Pharyngeal plexus cartilage Salpingopharyngeus Auditory tube Blends with musclesof Elevates pharynx Pharyngeal plexus pharynx Parts of Pharynx Nasopharynx: ● The upper part of pharynx lies behind the nasal cavity and below the body of sphenoid and basilar part of occipital bone. ● It extends from the posterior nasal openings (choanae) to palatopharyngeal isthmus. ● The pharyngeal tonsil is a collection of lymphoid tissue in its upper posterior part. ● The auditory tube opening lies in its lateral wall and its posterior margin is raised by the tubal tonsil forming tubal ridge or elevation. ● The salpingopharyngeal mucosal fold contains salpingopharyngeal muscle and descends behind the tubal ridge. The pharyngeal recess is a depressed area behind the tubal ridge. Oropharynx ● Lies behind the oral cavity and begins at the oropharyngeal isthmus bounded by the two palatoglossal arches. ● Its lateral wall has the palatglossal and palatopharyngeal arches which encircle the tonsillar fossa or sinus occupied by the tonsil. ● Its floor has three mucus folds between the tongue and epiglottis (one median glossoepiglottic fold and two lateral glossoepiglottic folds. Valeculla is the space between each lateral glossoepiglottic fold and median glossoepiglottic fold Laryngopharynx: ● Lies behind the larynx and it is connected anteriorly with the cavity of larynx through the inlet of larynx. ● Anteriorly and on each side of inlet of larynx, the laryngopharynx has a dead space called piriform recess or fossa which is the site for stagnation of food stuff & foreign bodies. ● Inferiorly, it is continuous with the esophagus. Nerve Supply of Pharynx Sensory supply: ● Nasopharynx by greater palatine branches of maxillary nerve ● Oropharynx and laryngopharynx by glossopharyngeal nerve ● A small areas around the inlet of larynx by internal laryngeal branch of vagus nerve. Motor supply ● Glossopharyngeal nerve (stylopharyngeus muscle) ● Cranial accessory nerve via vagus (all other muscles of pharynx) Autonomic supply: ● Postganglionic sympathetic fibers from superior cervical sympathetic ganglion along the arteries. ● Postganglionic parasympathetic from pterygopalatine ganglion via greater palatine nerve. Blood Supply & Lymph Drainage of Pharynx Arteries: ascending pharyngeal artery, ascending palatine branch of facial artery, branches of maxillary artery, branches of lingual artery Veins: into the corresponding veins Lymph Drainage: into deep cervical lymph nodes directly and via retropharyngeal and paratracheal lymph nodes. The Esophagus ● 25 cm long muscular tube continues from lower end of pharynx at the lower border of cricoid cartilage opposite the body of 6th cervical vertebra. ● Descends in the neck (cervical part), superior and posterior mediastinum (thoracic part), pierces the right crus of diaphragm at the level of 10th thoracic vertebra to enter the abdomen and joins the cardiac end of stomach (abdominal part ~ 1.25cm). Relations of Cervical Part Posteriorly: the 6th & 7th cervical vertebrae and pre-vertebral muscles & fascia. Anteriorly: the trachea & recurrent laryngeal nerve Laterally: the thyroid gland, carotid sheath and its contents, and the thoracic duct on the left. Relations of Thoracic Part: Posteriorly: thoracic vertebrae & prevertebral muscles, thoracic duct, posterior vagal trunk (right vagus), azygos vein, descending thoracic aorta, and the right posterior intercostal arteries. Anteriorly: trachea, left recurrent laryngeal nerve, left principle bronchus, left atrium and anterior vagal trunk (left vagus). Laterally to Right: mediastinal pleura, lung, & azygos vein. Laterally to Left: mediastinal pleura & lung, arch of aorta, left subclavian artery, and thoracic duct. Relations of Abdominal Part: Posteriorly: posterior vagal trunk & left crus of diaphragm. Anteriorly: anterior vagal trunk & left lobe of liver. Blood Supply of Esophagus Cervical part: inferior thyroid artery & vein. Thoracic part: arterial supply from descending thoracic aorta & left gastric artery. venous drainage into azygos, hemiazygos & left gastric vein. Abdominal part: left gastric artery & vein. Lymph Drainage of Esophagus Cervical part: deep cervical lymph node. Thoracic part: mediastinal, left gastric and celiac lymph nodes. Abdominal part: left gastric and celiac lymph nodes. Nerve Supply of Esophagus Cervical part: recurrent laryngeal nerves & branches of middle cervical sympathetic ganglion. Thoracic part: esophageal plexus formed by branches of anterior & posterior vagal trunks and branches of thoracic sympathetic ganglia. Abdominal part: anterior & posterior gastric nerves of vagal trunks, and branches of thoracic sympathetic ganglia. Histology of Esophagus ● The wall of esophagus consists of mucosa, submucosa, muscularis and adventitia. ● The epithelial lining of esophagus is non-keratinized stratified squamous epithelium ● The submucosa contains esophageal mucus glands. ● The esophageal cardiac mucus glands are present in the lamina propria of esophagus near cardiac opening of stomach. ● The muscles of muscularis are smooth type in lower 2/3 while skeletal type in upper 1/3. ● Only the abdominal part of esophagus has visceral peritoneal covering. The Anterior Abdominal Wall ● The anterior abdominal wall is formed by; skin, superficial fascia, deep fascia, muscles, transversalis fascia & extra peritoneal fat. It is lined internally by the serous peritoneal sac. ● The skin is loosely attached to superficial fascia except at the umbilicus which is tightly bound to the underlying fascia. The skin creases run horizontally outward inward, and surgical incisions made along them heal with little scar. ● The superficial fascia is of two layers; superficial fatty layer (Fascia of Camper) and deep membranous layer (Fascia of Scarpa). ● The Camper fascia is continuous with that of scrotum & lower limb. In the scrotum it is called dartos fascia which contains smooth muscle fibers. ● The Scarpa fascia makes a tubular sheath around the penis & scrotum. It descends in the upper part of thigh over the inguinal ligament and 1 cm below the ligament, it is fused with fascia lata (deep fascia of thigh). ● The deep fascia of anterior abdominal wall is replaced by thin fibrous layer which invests the muscles (Actually, there is No deep fascia). ● The muscles are; external oblique, internal oblique, transversus abdominis, rectus abdominis and pyramidalis. ● The fascia transversalis lies deep to transversus abdominis and is continuous with the psoas fascia, quadratus lumborum fascia, fascia under diaphragm and iliac fascia. In both sexes, it has a small natural opening (deep inguinal ring) 2 cm above the mid-inguinal point. ● The extraperitoneal loose areolar tissue with variable amount of fat lies between the transversalis fascia and parietal peritoneum. Nerve Supply of Skin of anterior abdominal wall ● The skin is supplied by the ventral rami of lower six thoracic ( lower five intercostal and subcostal nerves) and 1st lumbar nerves (ilio-hypogastric & ilio-inguinal nerves) . ● The skin is segmentally innervated: epigastric area by T6, region of umbilicus by T10, and the area above symphysis pubis and inguinal ligament by L1. Blood Supply anterior abdominal wall Arterial Supply: ♣ branches of superior & inferior epigastric arteries. ♣ deep circumflex iliac artery ♣ lower 5 intercostal, subcostal and lumbar arteries. ♣ superficial epigastric, superficial circumflex iliac and superficial external pudendal branches of femoral artery. Venous Drainage: ♣ above the umbilicus: into superior epigastric vein and axillary vein via lateral thoracic vein. Few paraumbilical veins around umbilicus pass through ligamentum teres to join veins of liver (Caput Medusae of portal hypertension). ♣ below the umbilicus: into external iliac vein by inferior epigastric vein, and into the femoral vein via the superficial epigastric, superficial circumflex iliac and superficial external pudendal tributaries of great saphenous vein. ♣ also into intercostal, subcostal & lumbar veins. Lymph Drainage of anterior abdominal wall ♣ From the area above the umbilicus into the axillary lymph nodes ♣ From the area below the umbilicus into the superficial inguinal lymph nodes Abdominal Regions, Lines & Planes ● The abdomen for descriptive & clinical purposes is divided into nine regions by two vertical lines ( right & left midclavicular or midinguinal ) and two transverse planes (transpyloric & intertubercular). ● The transpyloric plane lies at the level of pylorus of stomach and is drawn midway between sternal notch and symphysis pubis, or at the point where the linea semilunaris cuts the 9th costal cartilage. It is at the level of 1st lumbar vertebra. ● The intertubercular plane is drawn between the two iliac tubercles at the level of 5th lumbar vertebra. ● The transcristae plane is drawn between highest points on the two iliac crests at the level of 4th lumbar vertebra. ● The subcostal plane is drawn between the two most inferior points on the costal margins at the level of 3rd lumbar vertebra. Abdominal Quadrants The abdomen can be also divided into four quadrants (upper right, upper left, lower right & lower left) by two planes perpendicular to each other at the umbilicus. Muscles of Anterior Abdominal Wall
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