Internal Organs PDF - Oral Cavity Anatomy

Salva Garcia Noguera MU-Pleven 2016-2017 Topic 46: Oral cavity. Hard and soft palate Digestive system The digestive system consists of:  Digestive tract o Oral cavity o Oesophagus...

Salva Garcia Noguera MU-Pleven 2016-2017 Topic 46: Oral cavity. Hard and soft palate Digestive system The digestive system consists of:  Digestive tract o Oral cavity o Oesophagus o Stomach o Small intestine o Large intestine  Associated glands o Salivary glands o Liver o Pancreas The digestive system starts with the eating of food, which is followed by mechanical (mastication swallowing and propulsion) and chemical breakdown (enzymes) of the ingested material. After that, this material is digested, solubilized and absorbed by the intestinal mucosa. The digestive system also eliminates the waste products in form of fecal material. The alimentary mucosa is the surface across which all these processes happen, and it has the following functions:  Barrier function: prevents the entrance of noxious substances  Immunologic function: in the mucosa there is lymphoid tissue, known as MALT and GALT  Secretory function: secretes digestive enzymes, HCl, mucines, antibodies…  Absorptive function: absorb the nutrients Oral cavity The oral cavity is inferior to the nasal cavities and consists of the mouth and its content (tongue, teeth, salivary glands and tonsils). It is divided into:  Vestibule: located between the lips (oral fissure) and the cheeks, and the teeth. In it the canal of the parotid gland is opened at the internal surface at the level of the second upper molar  Oral cavity proper: enclosed by the following structures o Anteriorly and laterally: dental arches o Superiorly: soft and hard palate o Inferiorly: tongue and floor of the mouth (oral diaphragm) o Posteriorly: entrance to the oropharynx (oropharyngeal isthmus, isthmus faucium) and also soft palate In the oral cavity proper the ducts of the submandibular and sublingual glands empty their content Some of the functions of the oral cavity include:  Initial digestion of food (salivary amylase of ptyaline)  Manipulate sounds produced in the larynx  Breathing  Salva Garcia Noguera MU-Pleven 2016-2017 Important nerves for the oral cavity  Sensory information: predominantly from branches of the trigeminal nerve V o Upper part of oral cavity (teeth, palate): branches of maxillary nerve o Lower part of oral cavity (teeth, and oral part of tongue): branches of mandibular nerve  Taste o Anterior two thirds of the tongue: lingual nerve (branch of mandibular nerve), which contains fibers from the chorda tympani (facial nerve VII) o Posterior third: glossopharyngeal nerve IX and vagus nerve X  Parasympathetic fibers of the glands within the oral cavity (not the main salivary glands) o Branches of facial nerve V, distributed with branches of trigeminal nerve  Sympathetic innervation: comes from the spinal cord level T1, and synapses in the superior cervical sympathetic ganglia and are eventually distributed with branches of trigeminal nerve V or blood vessels  Muscles of the tongue: all innervated by hypoglossal nerve XII, except palatoglossus, which is innervated by the pharyngeal plexus (IX and X)  Muscles of the soft palate: all innervated by the vagus nerve X, except the tensor veli palatini, which is innervated by a branch of mandibular nerve Types of mucose In the oral cavity we can find three types of mucosae:  Lining epithelium: internal surface of the lip, internal surface of the cheeks, soft palate, floor of the mouth, ventral surface of the tongue and alveolar mucose o Stratified squamous non-keratinized  Masticatory epithelium: gums and hard palate o Stratified squamous keratinized (cells without nucleus in stratum cornum) or parakeratinized (some cells of stratum cornum maintain the nucleus)  Specialized epithelium: some regions of the dorsal and lateral surfaces of the tongue o Epithelium with taste buds Lips Constitute the anterior wall of the vestibule of the mouth and are made of a core of striated muscle (orbicularis oris) embedded in fibroelastic connective tissue. In the lip we can distinguish 3 surfaces:  Outer surface: covered with skin and a flat stratified squamous keratinized epithelium, where we can distinguish: o Hair follicles o Sebaceous glands o Sweat glands  Red transition zone: between outer skin and inner mucous membrane. Some of the characteristics of this part are: o High papillae of the basal lamina (contain many vessels and provide the red colour) o Stratified squamous keratinized epithelium, is the place of transition of the outer skin and mucosa. It is not as much keratinized as the outer surface o Sebaceous glands without follicles  Inner surface: composed of stratified squamous non-keratinized epithelium, we can find o Labial glands lying in the lamina propria o Papilla of the basal lamina are not very prominent, and are somehow flat The lips are mainly supplied by the superior and inferior labial branches of the facial artery. The upper lip is innervated by superior labial branches of the infraorbital nerve and the lower lip is innervated by the mental branch of the mandibular division of the trigeminal  Salva Garcia Noguera MU-Pleven 2016-2017 Cheeks Lateral wall of the oral cavity, they are composed of stratified squamous non-keratinized epithelium (lining epithelium), and inside the cheeks we can find the buccinators muscle. They contain the bucal fat pad tissue of Bichat, located between the masseter muscles and the buccinators muscle. The cheek receives its arterial blood supply principally from the buccal branch of the maxillary artery, and is innervated by cutaneous branches of the maxillary division of the trigeminal nerve, via the zygomaticofacial and infraorbital nerves, and by the buccal branch of the mandibular division of the trigeminal nerve. Gums Part of the masticatory epithelium, which is composed of both, keratinized and parakeratinized epithelium in order to avoid damage from the food we chew. Another main characteristic of the gums is that they lack submucose Vascular supply and lymphatic drainage of the oral mucosa  Arteries o Superior gingival tissues: branches of maxillary artery  Posterior superior alveolar artery  Anterior superior alveolar artery  Greater palatine artery o Inferior gingival tissue: branches of inferior alveolar artery (branch of maxillary artery)  Veins: some of the veins associated with the drainage of the maxilla are the buccal vein, greater palatine vein and nasopalatine vein, which drain into the pterygoid plexus, and later through the retromandibular vein to the internal carotid artery  Lymphatic drainage: lymph vessels from maxillar and mandibular gingivae drain mainly in the submandibular nodes and also in the submental nodes (anterior part) Floor The floor of the oral cavity proper is formed mainly by three structures:  Muscular diaphragm: composed of paired mylohyoid muscles, define the inferior limit of the floor of the oral cavity o Origin: mylohyoid line of the mandible o Insertion: median fibrous raphe and hyoid bone o Innervation: mylohyoid nerve o Function:  Supports and elevates the floor of the oral cavity  Depresses mandible when hyoid is fixed  Elevates and pulls hyoid forward when mandible is fixed  Genihyoid muscles: located superior to mylohyoid muscles and inferior to genioglossus muscles o Origin: inferior mental spine o Insertion: body of hyoid o Innervation: anterior rami of C1 o Function:  Elevates and pulls hyoid bone forward  Depresses mandible when hyoid is fixed  Salva Garcia Noguera MU-Pleven 2016-2017  Tongue: attached to the floor of the mouth by the lingual frenulum. On its sides we can see the sublingual caruncula, the duct through which the sublingual and submandibular gland excrete saliva Vascular supply and lymphatic drainage of the floor of the mouth  Arteries: the floor of the mouth is supplies by branches of the lingual artery, a branch of the external carotid artery  Veins: lingual and sublingual veins, which drain into the facial vein and later to the internal carotid artery  Lymphatic drainage: submandibular and submental nodes, which later drain to the superior deep cervical nodes and inferior deep cervical nodes Hard and soft palate The palate constitutes the roof of the oral cavity proper, and is divided into:  Hard palate  Soft palate Hard palate The hard palate is made of the following bones:  Palatine process of maxilla: are attached to each other in the intermaxillary suture  Horizontal plate of palatine bone: attaches with the palatine process of maxilla in the interpalatine suture The hard palate, as the gums, is composed of stratified squamous keratinized and parakeratinized epithelium in order to resist the contact with food. Characteristics of the epithelium:  Palatine rugae: located in the anterior part of the hard palate, increase the ease of grinding the food when it is compressed against the palate  Incisive papilla: located just below the incisive foramen, where the nasopalatine nerve (branch of maxillary nerve) emerges to innervate the anterior part of the mucosa of the hard palate  Palatine raphe: union of both palatine processes of maxillary bone  Anteriorly the hard palate contains fatty tissue in the submucosa  Posteriorly there are mucous glands within the submucosa  The palatine raphe of the gingival part do not contain submucosa and are firmly attached to the periosteum  In the posterior part of the soft palate there are: o Greater palatine foramen: for greater palatine artery and nerve (branch of maxillary nerve), which innervate the mucosa and glands of the palate except the anterior part o Lesser palatine foramen: for lesser palatine nerve (branch of maxillary nerve), which innervates the mucosa and glands of the soft palate Both nerves, come from the pterigopalatine ganglion, which contains the parasympathetic fibers from the greater petrosus nerve, a branch of facial nerve Soft palate The soft palate is a mobile fold attached to the posterior border of the hard palate, which is composed of the following five muscles:  Tensor veli palatine o Origin: scaphoid fossa of sphenoid and spine of sphenoid  Salva Garcia Noguera MU-Pleven 2016-2017 o Insertion: palatine aponeurosis o Innervation: mandibular nerve via the medial pterygoid nerve o Function: tenses the soft palate  Levator veli palatini o Origin: petrous part of temporal bone o Insertion: superior surface of palatine aponeurosis o Innervation: vagus nerve X o Function: elevates the soft palate  Palatopharyngeus o Origin: superior surface of palatine aponeurosis o Insertion: pharyngeal wall o Innervation: vagus nerve X o Function: depresses the soft palate  Palatoglossus o Origin: inferior surface of palatine aponeurosis o Insertion: lateral margin of tongue o Innervation: vagus nerve X o Function: depresses soft palate  Musculus uvulae o Origin: posterior nasal spine o Insertion: connective tissue of uvula o Innervation: vagus nerve X o Function: elevates and retracts uvula One of the main characterisitcs of the soft palate is that it is covered by two different epithelia depending on the surface:  Oral surface: stratified squamous no keratinized  Pharyngeal surface: columnar pseudostratified ciliated The soft palate also contains salivary glands, which are innervated by the lesser palatine nerve Embryology The oral cavity develops from the first pharyngeal arch, which is the first of 6 pharyngeal arches that develops during the fourth week of prenatal development. It is located between the stomodeum and the first pharyngeal groove. This arch divides into:  Maxillary process: becomes the maxilla and the palate  Mandibular process: becomes the mandible  Frontonasal prominence o Middle process o Lateral process The frontonasal prominence forms the nasal root.The two medial nasal prominences form the nasal dorsum and apex. The two lateral nasal prominences form the nasal sidewalls and alae The first pharyngeal arch also gives rise to the trigeminal nerve V and the maxillary artery.  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 47: Tongue The tongue is a highly muscular organ of deglutition, taste and speech located partially in the oral cavity and also in the pharynx. It is attached by its muscles to the following places:  Hyoid bone  Mandible  Styloid process  Soft palate  Pharyngeal wall External morphology and parts The tongue is divided into an oral and pharyngeal part by a sulcus terminalis:  Oral or presulcal part  Pharyngeal or postsulcal part At the same time, the tongue can be divided into several parts:  Root  Apex  Dorsum  Inferior surface Oral or presulcal part The presulcal part of the tongue is the part located anteriorly to the sulcus terminalis, a V-shaped sulcus that travels anterolaterally and divides the tongue into the oral part and the pharyngeal part. It is located in the floor of the oral cavity, with its apex touching the incisor teeth, and the superior surface in contact with the palate. The dorsal surface has a median longitudinal sulcus, and is covered by different types of papilla, some of which are involved in the perception of taste. The epithelium in the dorsal surface is squamous stratified non-keratinized, but in some specific areas can also be keratinized. The inferior surface is connected with the floor of the mouth with the lingual frenulum, and lateral to it we can see the sublingual caruncula, the duct through which sublingual and submandibular salivary glands provide saliva to the oral cavity. In this part of the tongue the epithelium is composed of simple squamous stratified non-keratinized. Pharyngeal or postsulcal part The postsulcal part of the tongue constitutes its base and lies posterior to the palatoglossal arches, where it constitutes the anterior wall of the oropharynx. This part of the tongue is closely associated with the palatine tonsillae, located in between the palatoglossal and palatopharyngeal arches. Posteriorly, the root of the tongue lacks papilla, and is closely associated with the epiglottis with the glossoepiglottic fold. At the same time, in this posterior region there is underlying lymphoid nodules in the submucosa, which is collectively called lingual tonsil. Muscles of the tongue The tongue is divided by a median fibrous septum, which is attached to the body of the hyoid bone. The muscles of the tongue can be classified as intrinsic muscles (with origin and insertion in the tongue and are used to change its shape) and extrinsic muscles (originate in distal places and move the tongue)  Salva Garcia Noguera MU-Pleven 2016-2017 Extrinsic muscles The extrinsic musculature consists of four pairs of muscles:  Genioglossus o Origin: superior mental spine o Insertion: entire length of the tongue o Innervation: hypoglossal nerve XII o Function: protrudes tongue  Hyoglossus o Origin: greater horn of hyoid o Insertion: lateral surface of the tongue o Innervation: hypoglossal nerve XII o Function: depresses tongue  Styloglossus o Origin: styloid process o Insertion: lateral surface of the tongue o Innervation: hypoglossal nerve XII o Function: elevates and retracts tongue  Palatoglossus o Origin: palatine aponeurosis o Insertion: lateral margin of tongue o Innervation: vagus nerve o Function: depresses the soft palate and elevates the back of the tongue Intrinsic muscles of the tongue Composed of 4 muscles:  Superior longitudinal: constitutes a thin layer located just below the mucosa of the dorsal surface. It extends forward from the submucous fibrous tissue near the epiglottis and from the median fibrous septum to the lingual margins. It shortens the tongue and is innervated by the hypoglossal nerve XII  Inferior longitudinal: located in the inferior surface of the tongue, it extends from the root of the tongue towards the apex. It shortens the tongue and is innervated by the hypoglossal nerve XII  Transverse: pass laterally from the median fibrous tissue to the lingual margins of the tongue. These fibers are innervated by the hypoglossal nerve XII and elongate and narrow the tongue  Vertical: extends from the dorsal to ventral surface of the tongue and flattens and widens the tongue. It is also innervated by the hypoglossal nerve XII  Salva Garcia Noguera MU-Pleven 2016-2017 Vascular supply and lymphatic drainage Vascular supply The tongue and the floor of the mouth are supplied chiefly by the lingual artery, which arises from the anterior surface of the external carotid artery. It enters in the tongue accompanied by the lingual vein and the glossopharyngeal nerve. Near the tip of the tongue it anastomoses with its contralateral fellow. Some of the branches of the lingual artery are:  Sublingual artery  Dorsal lingual arteries deep lingual artery The veins in charge of the drainage are the lingual veins, which accompany the lingual artery and are formed by:  Dorsal lingual veins  Deep lingual veins The lingual vein drains into the internal jugular vein Lymphatic drainage The lymphatic drainage of the tongue can be divided into three main regions:  Anterior: marginal vessels from the apex of the tongue and the lingual frenulum area drain the lymph to the submental or submandibular nodes. From the submental nodes the lymph usually reaches the jugulo-omohyoid node, and the submandibular nodes reach the upper deep cervical nodes  Central: the majority of lymph vessels of the central part of the tongue drain into the upperdeep cervical nodes, especially the jugulodigastric node  Dorsal: vessels draining the postsulcal region reach the upper deep cervical nodes and also the lower deep cervical nodes Papillae of the tongue In the tongue we have the taste buds, which are structures specialized in the recognition of flavours. They are located in papillae. We have the following types of papillae:  Filiform papillae: with a conic skape are the most numerous ones and the smallest. They are located in the dorsal surface of the tongue and covered by stratified squamous keratinized epithelium. These papillae are do not have taste buds and its main function is increase the friction between the food and the tongue  Fungiform papillae: mushroom-shaped and located in the anterior surface of the tongue. Are bigger that the filiform papillae, covered by stratified squamous non-keratinized epithelium and contain taste buds (epithelial localization) in the apical surface  Foliate papillae: located bilaterally in the margins of the tongue. Are covered by stratified squamous non-keratinized epithelium and contain taste buds  Circumvallate papillae: 8-12 papillae located in the anterior surface of the terminal sulcus. They are the largest ones and contain taste buds. The papillae are narrower at their base and are covered by a stratified squamous non-keratinized epithelium.  Salva Garcia Noguera MU-Pleven 2016-2017 In the tongue we can also distinguish salivary glands, and the most important ones are the serous Von Ebner glands, which are located in the base of foliate and circumvallate papillae and enable the taste buds to respond rapidly to the changes in flavours. Apart from these glands, there are also many minor mucous glands. Taste buds Located in the epithelium of several papillae, are important for the perception of taste. These barrel shaped epithelial structures contain chemosensory cells in synaptic contact with the terminals of gustatory nerves. Each taste bud is linked by synapses at its base to one of three cranial nerves which carry taste:  Facial VII: anterior 2/3 of the tongue through the lingual nerve with fibers coming from the chorda tympani VII  Glossopharyngeal XI: posterior 1/3 of the tongue  Vagus X: small part of the root of the tongue Each taste bud contains 50-150 fusiform cells with have contact with the external surface through the gustatory pore. Chemical substances dissolved in the oral saliva diffuse through the gustatory pores of the taste buds to reach the taste receptor cell membranes, where they cause membrane depolarization. In addition to the papillae, taste buds are also found on the glossopalatine arch, palate, epiglottis and pharynx Innervation of the tongue  Motor innervation o Hypoglossal nerve XII o Vagus nerve X  Sensitive innervation o Glossopharyngeal nerve IX o Vagus nerve X o Lingual nerve  Gustative innervation o Facial VII: anterior 2/3 of the tongue through the lingual nerve with fibers coming from the chorda tympani VII o Glossopharyngeal XI: posterior 1/3 of the tongue o Vagus X: small part of the root of the tongue  Autonomic innervation o Parasympathetic innervation: chorda tympani branch of the facial nerve which synapses in the submandibular ganglion: postganglionic branches are distributed to the lingual mucosa via the lingual nerve o Sympathetic innervation: arises from the carotid plexus and enters the tongue through plexuses around the lingual arteries Embryology of the tongue The tongue begins to form during the fourth week, at approximately the same time as the palates and has contributions of the first four pharyngeal arches:  First and second arch: oral part of the tongue  Third arch: pharyngeal part of the tongue  Fourth arch: epiglottis and adjacent regions One of the main characteristics of the tongue is that it is closely related to the development of the thyroid gland. The latter develops in the terminal sulcus. At the tip of the terminal sulcus is the foramen caecum, which is the point where the embryological thyroid begins to descend. We can say that the foramen caecum is a remnant of the upper end of the thyroglossal duct.  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 48: Isthmus faucium. Tonsils Isthmus faucium Isthmus faucium is the transition zone between the oral cavity and the oropharynx. It is the space situated between the palatoglossal and palatopharyngeal arches laterally, the soft palate superiorly and the tongue inferiorly. The fauces are regarded as the two pillars, formed by the palatoglossus and the palatopharyngeus muscle, respectively, and covered with mucous membrane. The anterior one is known as the palatoglossal arch, and the posterior one is known as the palatopharyngeal arch. Each palatoglossal arch runs downwards, laterally and forwards, from the soft palate to the side of the tongue. The approximation of the arches due to the contraction of the palatoglossal muscles constricts the isthmus, and is essential to swallowing (deglutition) These arches are important because regulate the entrance of food into the pharynx by the contraction of the muscles and also prevent the entrance of food in the nasal cavity.  Palatopharyngeus o Origin: superior surface of palatine aponeurosis o Insertion: pharyngeal wall o Innervation: vagus nerve X o Function: depresses the soft palate  Palatoglossus o Origin: inferior surface of palatine aponeurosis o Insertion: lateral margin of tongue o Innervation: vagus nerve X o Function: depresses soft palate The palatoglossal arch runs from the soft palate to the sides of the tongue, and the palatopharyngeus projects more medially than the palatoglossal arch and passes from the soft palate to blend with the lateral wall of the pharynx. Between both arches there is the tonsillar fossa, which contains the palatine tonsil in both sides Vascular supply  Arteries: the arterial supply of the soft palate and arches is usually derived from the ascending palatine branch of the facial artery. The ascending pharyngeal artery also provides part of the blood  Veins: the soft palate and the arches drain into the pterygoid venous plexus Tonsils The lymphoid tissue around the pharynx is collectively called the Waldeyer's tonsillar ring (MALT), and consists of:  Pharyngeal tonsil: are also called adenoids, and are located on the roof of the nasopharynx, under the sphenoid bone  Tubal tonsils: bilaterally, where each Eustachian tube opens into the nasopharynx  Palatine tonsils: located in the tonsillar fossa of the isthmus faucium  Lingual tonsil: located in the root of the tongue  Salva Garcia Noguera MU-Pleven 2016-2017 Pharyngeal tonsil The adenoid, or pharyngeal tonsil, is a median mass of mucosa-associated lymphoid tissue (MALT) situated in the roof and posterior wall of the nasopharynx. After birth it initially grows rapidly, but usually undergoes a degree of involution and atrophy from the age of 8–10 years. The adenoid is covered by a ciliated repiratory epithelium and contributes to the defence of the upper respiratory tract. The vascular supply of the pharyngeal tonsil is derived from:  Ascending pharyngeal artery  Ascending palatine arteries Numerous communicating veins drain the pharyngeal tonsil into the internal submucous and external pharyngeal venous plexuses that eventually leads to the internal jugular vein. Tubal tonsils The mucosa of the pharyngotympanic tube is continuous with the nasopharyngeal and tympanic mucosae. It is lined by a pseudostratified ciliated columnar epithelium. Near the pharyngeal orifice there is a variable, but sometimes considerable, lymphoid mass called the tubal tonsil. The arteries that supply the tubal tonsil are:  Ascending pharyngeal branch  Middle meningeal artery (branch of maxillary artery) The veins drain with the pterygoid venous plexus Palatine tonsil Each tonsil is an ovoid mass of lymphoid tissue situated in the lateral wall of the oropharynx between the palatoglossal and palatopharyngeal arches and medial to the superior constrictor of the pharynx. For the first 5 or 6 years of life the tonsils increase rapidly in size. They usually reach a maximum at puberty, after which starts the tonsillar involution. At the end of this latter period only a little tonsillar lymphoid tissue remains. Its medial, free, surface usually presents a pitted appearance with several crypts, which extend through the whole thickness of the tonsil and almost reach the connective tissue hemicapsule. Each tonsil is a mass of lymphoid tissue associated with the oropharyngeal mucosa and fixed in its position. It is covered by a by non-keratinized stratifi ed squamous epithelium and internally contains connective tissue made of collagen type III (reticulin). The vascular arterial supply of the palatine tonsils is derived from branches of the external carotid artery:  Tonsilar artery (branch of facial artery)  Ascending palatine artery  Dorsal lingual branches of lingual artery  Ascending pharyngeal artery The capillaries rejoin to form veins which reach the pharyngeal drainage. Unlike lymph nodes, the palatine tonsils do not possess afferent lymphatics sinuses, instead dense plexuses of fine lymphatic vessels surround each follicle and form efferent lymphatics. The innervation of the palatine tonsils is by tonsil branches of maxillary nerve and glossopharyngeal nerve. In the young fetus, the palatine tonsil forms on both sides in the tonsillar sinus as the remainder of the 2nd pharyngeal pouch. The epithelium thickens and under it a mesenchymal accumulation forms from material of the second pharyngeal arch.  Salva Garcia Noguera MU-Pleven 2016-2017 Lingual tonsil The lingual tonsils are two small mounds of lymphatic tissue located at the back of the base of the tongue, one on either side. They are composed of lymphatic tissue that functions to assist the immune system in the production of antibodies in response to invading pathogenic bacteria or viruses. Lingual tonsils are covered externally by stratified squamous nonkeratinized epithelium. This epithelium invaginates inwards to form cripts, beneath which there is lymphoid tissue. Mucous glands located at the root of tongue are drained through several ducts into the crypt of lingual tonsils. Secretions of these mucous glands keep the crypt clean and free of any debris. Therefore, the lingual tonsils are less prone to infection. The blood supply is related to:  Lingual artery, a branch of external carotid artery  Tonsil branch of facial artery  Ascending pharyngeal branch of external carotid artery The lingual tonsils are usually drained by the pterygoid venous plexus The innervation of the lingual tonsil is by branches of the glossopharyngeal nerve. The lingual tonsil arises from the second cleft recess (pharyngeal pouch) during the third month of foetal live. Beneath the epithelium of all tonsils there is a layer of lymphoid nodules containing lymphocytes. These tonsils are surrounded by thin capsule of connective tissue which separates them from adjacent structures. Inside the lymphoid tissue we can easily distinguish T and B cells, which are the one in charge of the production of mediators and antibodies in order to prevent infections.  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 49: Principal salivary glands The principal salivary glands are the following ones:  Parotid gland: pure serous  Submandibular gland: mixed but mainly serous  Sublingual gland: mixed but mainly mucous Parotid gland The parotid glands are the largest salivary glands and numerous structures pass through them. They are anterior to and below the lower half of the ear, superficial, posterior, and deep to the ramus of the mandible. They extend down to the lower border of the mandible and up to the zygomatic arch. Posteriorly they cover the anterior part of the sternocleidomastoid muscle and continue anteriorly to halfway across the masseter muscle. The parotid duct leaves the anterior edge of the parotid gland and migrates anteriorly, passing through the buccal fat pad and pierces the buccinators muscles to later reach the vestibule of the oral cavity at the level of the superior second molar. Several important structures pass through the parotid gland:  Facial nerve VII: exits the skull through the stylomastoid foramen and passes into the parotid gland, where it divides into five branches: o Temporal o Zigomatic o Buccal o Mandibular o Cervical  External carotid artery: as it enters in the inferior margin of the parotid gland it gives of the following branches: o Posterior auricular artery o Maxillary o Temporal superficial  Retromandibular vein: is formed when the superficial temporal and maxillary vein join together, after that in divides into anterior and posterior branches , just below the inferior margin of the parotid Histology The gland is surrounded by a fibrous capsule, and from the inner surface of the capsule the connective tissue forms fibrous septa, dividing the parotid gland into lobules. The parotid gland also contains large amounts of adipose tissue. The secretory part of the parotid gland is composed entirely of tubulo-alveolar serous acini, which cells are pyramidal in shape with a big round nucleus located in the basal zone. The cells contain a well-developed RER and Golgi apparatus, with zymogen granules located in the apical portion of the cell. The ducts of the parotid gland are formed first of intercalated ducts (simple cuboidal epithelium) that collect the saliva directly from the serous acini. After that some of these ducts unite and form the intercalated ducts (simple columnar cells) which cells absorb Na+ and Cl- and serete K+ and HCO3-. They are called striated ducts because in the basal membrane they have many infoldings. These striated ducts will unite to form intralobular ducts and later interlobular ducts. The latter ones will also unite to form the excretory ducts, which are lined with cuboidal epithelium.  Salva Garcia Noguera MU-Pleven 2016-2017 Lymphatic drainage The gland is mainly drained into the preauricular or parotid lymph nodes which ultimately drain to the deep cervical chain. Innervation The parotid gland receives both sensory and autonomic innervation:  Sensory innervation: supplied by the auriculotemporal nerve, a branch of the mandibular nerve  Autonomic innervation: controls the rate of saliva production o Sympathetic fibers: from superior cervical sympathetic ganglion the sympathetic fibers reach the gland as periarterial nerve plexuses around the external carotid artery o Parasympathetic fibers: reganglionic parasympathetic fibers leave the brain stem from inferior salivatory nucleus in the glossopharyngeal nerve and then through its tympanic and then the lesser petrosal branch pass into the otic ganglion. There, they synapse with postganglionic fibers which reach the gland by hitch-hiking via the auriculotemporal nerve Embryology The parotid salivary glands appear early in the sixth week of prenatal development and are the first major salivary glands formed. They derive from the first and second pharyngeal arches. The epithelial buds of these glands come from the ectoderm, and keep on growing until the formation of the ducts system. The capsule of the parody gland develops from the mesenchyme. Submandibular gland The paired submandibular glands are major salivary glands located beneath the floor of the mouth. Lying superior to the digastric muscles, each submandibular gland is divided into superficial (bigger) and deep lobes, which are separated by the mylohyoid muscle. This gland is located in the submandibular triangle, which boundaries are:  Inferior margin of mandible  Anterior belly of digastric  Posterior belly of digastric Secretions are delivered into the Wharton duct or submandibular duct, and then drains into the sublingual caruncula together with sublingual duct of Bartholin. Both submandibular glands are in intimate relationship with:  Lingual nerve: anteromedially to the submandibular gland  Hypoglossal nerve: deep to the digastric muscle  Mandibular branch of facial nerve: inferior to the submandibular gland Histology The submandibular gland is a mixed gland mainly serous surrounded by a fibrous capsule as the parotid gland that divides it into several septa and lobules. In contrast to the parotid gland, the submandibular gland does not have adipose tissue. The secretory portion of the submandibular gland is composed of tubulo-alveolar acini of mucous and serous type, but the majority of them are serous. The serous cells surround the mucous acini in form of serous demilunes, and empty their content in the same tubules. The duct system of the submandibular gland is similar to that of the parotid one:  Intercalated  Striated  Intralobular  Interlobular  Excretory duct  Salva Garcia Noguera MU-Pleven 2016-2017 The mucous cells are pyramidal in shape with a smaller and flatter nucleus than that of the serous cells, and its disposition is in the basal part of the cell. Another difference is that mucous cells do not stain well with HE dye, while serous cells highly basophilic (stain with hematoxylin). In the apical part of the cells we can find mucous granules. Vascularization and lymphatic drainage The gland receives its blood supply from the facial and lingual arteries and drained by common facial and lingual veins. The lymphatic drainage first drains into submandibular lymph nodes and subsequently into jugulodigastric lymph nodes. Innervation The secretion of the submandibular glands is regulated by the autonomic innervation:  Parasympathetic innervation: provided by the superior salivatory nucleus via the chorda tympani, a branch of the facial nerve, that becomes part of the trigeminal nerve's lingual nerve prior to synapsing on the submandibular ganglion. Postsynaptic fibers promote salivation  Sympathetic innervation: originates from the superior cervical ganglion, where post-synaptic vasoconstrictive fibres travel as a plexus on the internal and external carotid arteries, facial artery and finally the submental arteries to enter each gland. Inhibit salivation Embryology The submandibular gland develops from the hyoid arch (second brachial arch) during the 6 week. The main difference with the parotid gland is that the submandibular gland develops from the endoderm and not from the ectoderm. The mesenchyme forms the capsule of the gland Sublingual gland The sublingual glands are the smallest of the three paired salivary glands and the most deeply situated. They produce mixed secretion but mainly mucous. The sublingual glands are almond-shaped (ovoid) and lie on the floor of the oral cavity proper, situated under the tongue, bordered laterally by the mandible and medially by genioglossus muscle and the following structures:  Lingual nerve  Submandibular duct Histology One of the main differences of the sublingual gland is that it is not surrounded by a fibrous capsule. Conversely it has loose connective tissue septa that divide the gland into lobules The secretory portion of the sublingual gland is composed of tubuloacinar mucous and serous glands, but mainly mucous. The duct system is similar to the one found in the other glands. Secretions drain into the oral cavity by minor sublingual ducts (of Rivinus), of which there are 8-20 excretory ducts per gland, each opening out onto the sublingual folds. It is also possible to find an extra excretory duct that connects with the submandibular duct and empty the salivary content in the sublingual caruncula.  Salva Garcia Noguera MU-Pleven 2016-2017 Vascularization and lymphatic drainage Blood supply is via the following arteries:  Sublingual artery: branch of lingual artery  Submental artery: branch of facial artery Venous drainage is through the sublingual and submental veins which drain into the lingual and facial veins respectively; both then draining into the internal jugular vein. Lymph from the sublingual salivary gland drains into the submandibular lymph nodes and subsequently into jugulodigastric lymph nodes, just like the submandibular gland Innervation Supplied by:  Parasympathetic innervation: originates from the superior salivatory nucleus through pre-synaptic fibres via the chorda tympani branch of the facial nerve VII. The chorda tympani then unifies with the lingual branch of the mandibular nerve V before synapsing at the submandibular ganglion and suspending it by two nerve filaments. Post-ganglionic innervation consists of secretomotor fibres which directly induce the gland to produce secretions, and vasodilator fibres which accompany arteries to increase blood supply to the gland. Increased parasympathetic drive promotes saliva secretion.  Sympathetic innervation: Sympathetic innervation originates from the superior cervical ganglion, where post-synaptic vasoconstrictive fibres travel as a plexus on the internal and external carotid arteries, facial artery and finally the sublingual and submental arteries to enter each gland. Embryology The sublingual salivary glands appear in the eighth week of prenatal development, two weeks later than the other two major salivary glands. They develop from the same region as submandibular glands, from endoderm of the second brachial pouch.  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 50: Pharynx The pharynx is a musculofascial half-cylinder that links the oral and nasal cavities in the head to the larynx and oesophagus in the neck. As we can see is a common pathway for air and food. The pharynx is attached above to the base of the skull and is continuous below, approximately at the level of vertebra C6, with the top of the esophagus. The walls of the pharynx are attached anteriorly to the margins of the nasal cavities, oral cavity, and larynx. Based on these anterior relationships the pharynx is subdivided into three regions:  Nasopharynx: the posterior apertures of the nasal cavity (choanae) open into the nasopharynx  Oropharynx: the posterior aperture of the oral cavity (isthmus faucium) opens into the oropharynx  Laryngopharynx: the superior aperture of the larynx (laryngeal inlet) opens into the laryngopharynx In addition to these openings, the pharyngeal cavity is related anteriorly to the posterior one-third of the tongue and to the posterior aspect of the larynx. Also the pharyngotympanic tubes open into the lateral walls of the nasopharynx. The pharynx is separated from the posteriorly positioned vertebral column by a thin retropharyngeal space containing loose connective tissue. Skeletal framework of the pharynx The superior and anterior margins of the pharyngeal wall are attached to bone, cartilage, and to ligaments, while the posterior wall is formed by the fusion of the two sides of the pharynx in a ligamentous structure known as pharyngeal raphe. The latter one descends from the pharyngeal tubercle and reaches the level of C6 to blend with the connective tissue of the oesophagus. Superiorly the pharynx is attached to the base of the skull, starting in the medial plate of the pterygoid process and migrating posterolaterally towards the petrous part of the temporal bone. After that, it migrates anteromedially to reach the pharyngeal tubercle of the occipital bone. The anterior lines of attachment of the lateral walls are:  Superior part: pterygomadibular raphe  Middle part: stylohyoid ligament and posterior surface of hyoid  Inferior part: from the superior tubercle of the thyroid cartilage and migrating over the oblique line Muscles of the pharynx Constrictors  Superior constrictor: forms the palatopharyngeal sphincter o Origin: pharyngeal raphe o Insertion: pterygomandibular raphe o Innervation: vagus nerve X o Function: constrict the pharynx  Middle constrictor o Origin: pharyngeal raphe o Insertion: hyoid and stylohyoid ligament o Innervation: vagus nerve X o Function: constricts the pharynx  Salva Garcia Noguera MU-Pleven 2016-2017  Inferior constrictor o Origin: pharyngeal raphe o Insertion: superior tubercle of thyroid cartilage and oblique line o Innervation: vagus nerve X o Function: constricts the pharynx Longitudinal muscles  Stylopharyngeus o Origin: styloid process o Insertion: pharyngeal wall o Innervation: glossopharyngeal nerve IX o Function: elevates the pharynx  Salpingopharyngeus o Origin: pharyngotympanic tube o Insertion: pharyngeal wall o Innervation: vagus nerve X o Function: elevates the pharynx  Palatopharyngeus o Origin: upper surface of palatine aponeurosis o Insertion: pharyngeal wall o Innervation: vagus nerve o Function: elevation of the pharynx The pharyngeal fascia is separated into two layers which surround the muscles:  Buccopharyngeal fascia: part of the pretracheal fascia, covers the outer surface of the pharyngeal wall  Pharyngobasilar fascia: convers the inner surface Oropharyngeal triangle One of the largest and most important apertures in the pharyngeal wall is between the superior and middle constrictor muscles of the pharynx and the posterior border of the mylohyoid muscle. This gap is known as the oropharyngeal triangle, which allows the passage of vessels, muscles and nerves to pass in and out to the oral cavity. Another important space is between the middle and inferior constrictor, which allows the passage of the internal laryngeal nerve and vessels Nasopharynx The nasopharynx is behind the posterior apertures (choanae) of the nasal cavities and above the level of the soft palate. The cavity of the nasopharynx is continuous below with the cavity of the oropharynx at the pharyngeal isthmus. Elevation of the soft palate and constriction of the palatopharyngeal sphincter closes the pharyngeal isthmus during swallowing and separates the nasopharynx from the oropharynx. The most important structures in the nasopharynx are:  Opening of the pharyngotympanic tube (Eustachian tube)  Torus tubarius: just posterior to the opening of the pharyngotympanic tube Oropharynx The oropharynx is posterior to the oral cavity, inferior to the level of the soft palate, and superior to the upper margin of the epiglottis. The anterior wall of the oropharynx inferior to the oropharyngeal isthmus is the pharyngeal part of the tongue.  Salva Garcia Noguera MU-Pleven 2016-2017 When holding liquid or solids in the oral cavity, the oropharyngeal isthmus is closed by depression of the soft palate, elevation of the back of the tongue, and movement toward the midline of the palatoglossal and palatopharyngeal folds. This allows a person to breathe while chewing or manipulating material in the oral cavity. On swallowing, the oropharyngeal isthmus is opened, the palate is elevated, the laryngeal cavity is closed, and the food or liquid is directed into the esophagus. A person cannot breathe and swallow at the same time because the airway is closed at two sites, the pharyngeal isthmus and the larynx. Laryngopharynx The laryngopharynx extends from the superior margin of the epiglottis to the top of the oesophagus at the level of vertebra C6. The laryngeal inlet opens into the anterior wall of the laryngopharynx. Inferior to the laryngeal inlet, the anterior wall consists of the posterior aspect of the larynx. Vascular supply and lymphatic drainage The arteries that supply the upper part of the pharynx are (all come from the external carotid artery):  Ascending pharyngeal artery  Ascending palatine and tonsil branches of facial artery  Branches of maxillary and lingual arteries Veins of the pharynx form a plexus, which drains superiorly into the pterygoid plexus in the infratemporal fossa, and inferiorly into the facial and internal jugular veins Lymphatic vessels from the pharynx drain into the deep cervical nodes and include retropharyngeal, paratracheal, and infrahyoid nodes  Salva Garcia Noguera MU-Pleven 2016-2017 Innervation Motor and most sensory innervation (except for the nasal region) of the pharynx is mainly through branches of the vagus [X] and glossopharyngeal [IX] nerves, which form a plexus in the outer fascia of the pharyngeal wall. The pharyngeal plexus is formed by:  Pharyngeal branch of vagus nerve X  Pharyngeal branches of glossopharyngeal nerve IX Each subdivision of the pharynx has a different sensory innervation:  Nasopharynx: pharyngeal branch of maxillary nerve V  Oropharynx: glossopharyngeal nerve IX via the pharyngeal plexus  Laryngopharynx: vagus nerve X Embryology Major structures of the neck and oral cavity derive from the pharyngeal apparatus, which is composed of the following structures:  Pharyngeal arches: derived from the cells of the neural crest and start developing at week 4  Pharyngeal pouches: located in the endodermal part of the spaces between the pharyngeal arches  Pharyngeal grooves: located in the ectodermal part of the spaces between the pharyngeal arches  Salva Garcia Noguera MU-Pleven 2016-2017 Pharyngeal arches By end of 4th week, four pairs of arches are visible on the surface and a buccopharyngeal membrane ruptures forming communication between primitive oral cavity and foregut. The structure of the pharyngeal arches is a core of mesenchymal tissue covered by ectoderm on the outer surface and by endoderm in the inner surface. Each pharyngeal arch contains nerve, artery and vein to supply the future structures that will derive from each arch.  1st pharyngeal arch: o Maxillary process  Premaxilla, maxilla, zygomatic bone and part of temporal bone o Mandibular process  Meckel’s cartilage o Muscles of mastication, anterior belly of digastric, mylohyoid, tensor veli palatini o Trigeminal nerve V o Maxillary artery and external carotid artery  2nd pharyngeal arch o Reichert’s cartilage: dorsally forms the stirrup of middle ear and ventrally part of the hyoid bone o Posterior belly of digastric, facial expression muscles o Facial nerve VII o Hyoid artery and stapedial artery rd  3 pharyngeal arch o Greater horn and lower part of hyoid o Stylopharyngeus o Glossopharyngeal nerve IX o Common carotid artery and internal carotid artery th  4 pharyngeal arch o Intrinsic muscles soft palate except tensor veli palatini o Thyroid cartilage o Epiglottis o Vagus nerve X (superior laryngeal nerve) o Right aortic arch and subclavian artery  6th pharyngeal arch o Intrinsic muscles of larynx o Cricoid, arytenoid, corniculate and cuneiform cartilages o Vagus nerve X (recurrent laryngeal nerve) o Pulmonary artery and ductus arteriosus  Salva Garcia Noguera MU-Pleven 2016-2017 Pharyngeal pouches  1st pouch: Pharyngotympanic Eustachian tube, middle ear and tympanic membrane  2nd pouch: middle ear and palatine tonsils  3rd pouch: the dorsal part forms the superior parathyroid and the ventral part the thymus  4th pouch: superior parathyroid  5th pouch: C cells of thyroid gland (not the thyroid gland) Pharyngeal grooves  1st groove: external auditory meatus  2nd-4th: epicardial ridge and cervical sinus Histological structure The wall of the pharynx is composed of the following layers:  Mucous membrane: is the continuation of the nasal cavity, oral cavity and larynx. The nasopharynx is covered with pseudostratified ciliated columnar epithelium that contains goblet cells, which is the same epithelium that we can find in the respiratory tract. The oropharynx and laryngopharynx, as are susceptible to be affected by the abrasion of food, so are lined with stratified squamous non-keratinized epithelium. o Lamina propria: contains connective tissue and nerves and vessels. Also lymphatic tissue and mucous glands o Submucosa  Fibrous layer: lies between the mucous membrane and the muscle layer. It is thick above, where it is connected to the skull. Below it becomes continuous with the submucous layer of the oesophagus  Muscular layer: made of striated muscles, we can find the 3 constrictors and the 3 longitudinal muscles. All these muscles are voluntary  Adventitia: covers the pharynx outside  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 51: Oesophagus The oesophagus is a muscular tube, typically 25 cm long, which connects the pharynx to the stomach. It begins in the neck, at the level of C6 and descends largely anterior to the vertebral column through the superior and posterior mediastinum. It passes through the diaphragm at the level of T10 and ends at the gastric cardiac orifice level with the T11. The oesophagus has two shallow curves:  As it begins it inclines to the left at the root of the neck and returns to the median nerve in T5  It bends to the left at the level of T7 again Along the oesophagus there are 2 different types of constriction:  Anatomical constrictions o At its beginning in the junction with pharynx o When it is crossed by the left principal bronchus o When it passes through the diaphragm  Physiological constriction o Where it is crossed by the aortic arch o As it enters in the stomach Parts of the oesophagus It has three parts; cervical, thoracic and abdominal. Cervical The cervical oesophagus (C6-T1) is posterior to the trachea and attached to it by loose connective tissue. The recurrent laryngeal nerves (branch of vagus X) ascend on each side in or near the tracheo-oesophageal groove. Posteriorly we have the vertebral column and the paravertebral layer of the deep cervical fascia. Laterally on each side are the common carotid arteries and posterior part of the thyroid gland. Thoracic The thoracic oesophaguss situated a little to the left in the superior mediastinum between the trachea and the vertebral column. It passes behind and to the right of the aortic arch to descend in the posterior mediastinum along the right side of the descending thoracic aorta. Below, as it inclines left, it crosses anterior to the aorta and enters the abdomen through the diaphragm. During the whole course the following structures are anterior:  Trachea  Right pulmonary artery  Left main bronchus  Pericardium The following structures are posterior:  Vertebral column  Longus colli  Right posterior intercostal arteries  Thoracic duct  Azygos vein  Aorta (in the diaphragm)  Salva Garcia Noguera MU-Pleven 2016-2017 In the superior mediastinum, the terminal part of the aortic arch, the left subclavian artery, thoracic duct, the left pleura and the recurrent laryngeal nerve are left lateral relations. In the posterior mediastinum, the oesophagus is related to the descending thoracic aorta and left pleura. Low in the posterior mediastinum, the thoracic duct is behind and to the right of the oesophagus; at higher levels the duct is posterior, crossing to the left of the oesophagus at about the level of the T5 and then ascending on the left. Abdominal oesophagus The abdominal oesophagus is 1–2,5cm in length and lies to the left of the midline after entering through the oesophageal aperture (formed by the two diaphragmatic crura) at the level of T10. It runs obliquely to the left and slightly posteriorly, and ends at the gastro-oesophageal junction of the stomach. The abdominal oesophagus lies posterior to the left lobe of the liver and to the left of the left inferior phrenic vessels. The abdominal oesophagus is effectively related with the diaphragm through the phreno-oesophageal ligament. On the thoracic side of the diaphragm the superior phrenooesophgeal ligament is similarly formed from an extension of the subpleural endothoracic fascia. Vascular supply and lymphatic drainage Cervical and thoracic oesophagus  Arteries: the cervical oesophagus is supplied by the inferior thyroid artery. The thoracic part by bronchial and oesophageal branches of aorta  Veins: perioesophageal venous plexus from which oesophageal veins arise. Those from the thoracic oesophagus drain predominantly into the azygos and hemiazygos veins  Lymph: deep cervical nodes in the cervical part and posterior mediastinal nodes in the thoracic part  Salva Garcia Noguera MU-Pleven 2016-2017 Abdominal oesophagus  Arteries: The abdominal oesophagus is supplied by oesophageal branches of the left gastric artery. The posterior surface usually receives an additional supply via terminal branches of the oesophageal branches of the thoracic aorta  Veins: drain via plexuses to the left gastric and upper short gastric veins  Lymph: left gastric nodes and left and right paracardial nodes Innervation The upper oesophagus is supplied by the branches of the recurrent laryngeal nerve (branch of vagus X) and by postganglionic sympathetic fibres that reach it by travelling along the inferior thyroid arteries. The lower oesophagus is supplied by the oesophageal plexus, a widemeshed autonomic network that surrounds the oesophagus below the level of the lung roots, and which contains a mixture of parasympathetic and sympathetic fibres. Motor fi bres to the striated and smooth muscle of the oesophageal wall travel in the vagus X:  Fibers that travel with the recurrent laryngeal innervate the superior third  The oesophageal plexus innervates the inferior two thirds  The vagus nerve also carries sensory information Histological structure The wall of the oesophagus consists of the three layers that are characteristic of the alimentary tract:  Tunica mucosa: contains the following subdivision o Lamina epithelialis: consists of stratified squamous non-keratinized epithelium (protective) which is continuous with the pharynx above. Below, at the gastro-oesophageal junction it becomes simple columnar. o Lamina propria: contains diffuse lymphatic tissue and also in the lower parts we can distinguish oesophageal cardiac glands, which resemble the ones that we have in the cardiac of the stomach to neutralize the acid with mucous and bicarbonate o Muscularis mucosae: formed of smooth muscles, it is quite thick in the upper portion to help in the swallowing process o Submucosa: the main characteristic of this layer is that in the oesophagus we can find the proper oesophageal glands, which secrete mucous to help in the lubrication. Also contains the Meissner’s plexus  Tunica muscularis: differs from the rest of the digestive tract. The upper one third is striated muscle as a continuation of the muscles of the pharynx. In the middle part we can find striated fibers mixed with smooth fibers, and in the lower part we can only find smooth fibers. In between the circular and longitudinal fibers we can find the Myenteric plexus  Tunica adventitia or serous: is the outermost layer, and in the cervical and thoracic portions we can find the tunica adventitia, connective tissue that connects the oesophagus with the rest of the structures. In the abdominal part the serous (peritoneum) covers the lower portion Embryology The development of the oesophagus starts in the foregut (endoderm), which will develop anteriorly in the trachea and posteriorly in the oesophagus. This process starts during the 4th week, when the tracheoesophageal ridge separates the foregut into the trachea and bronchial buds ventrally and the oesophagus posteriorly. Once the separation has been accomplished, there is an elongation of the oesophagus due to de descent of the heart and lungs.  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 52: Stomach The stomach is a dilated portion of the alimentary canal and is concerned with the storage and digestion of food. It is an intraperitoneal organ mainly localized in the epigastric region (also umbilical and left hypochondrium), in the level of T11-L1 vertebrae. We can describe the stomach as having two surfaces, anterior and posterior, which meet in the lesser and greater curvature. Parts of the stomach The stomach is divided into four regions:  Cardia: surround the opening of the oesophagus into the stomach  Fundus: area above the level of the cardial orifice, close related to the left part of the diaphragm  Body: largest region of the stomach  Pyloric part: divided into o Pyloric antrum: extends from the insicura angularis to the proximal limit of pyloric canal o Pyloric canal: most tubular part of the stomach  Cardial notch: superior angle created when the esophagus enters the stomach  Angular incisures: bend on the lesser curvature  Greater curvature: extends from the left of the cardiac orifice, over the dome of fundus and sweeps around until the inferior part of pylorus  Lesser curvature: forms the right border of the stomach and extends from the cardiac orifice to the pylorus When empty and contracted the stomach is flattened anteroposteriorly and its interior has the characteristic rugae, longitudinal folds of the mucosa. When the stomach fills it expands and the rugae disappear. Between the rugae, we can distinguish the gastric areas, irregular shallow surfaces. Microscopic structure of the stomach At higher magnification numerous openings can be observed in the mucous surface. These are the gastric pits or foveolae, located in the gastric areas. These are the regions where the gastric glands empty their content. Histologically the stomach is composed of the following layers:  Mucous membrane  Muscular layer  Serosa layer Mucous membrane It is further divided into:  Mucous membrane: lined with simple columnar epithelium. The cells appear as having the apical surface empty because of the extraction of the mucous droplets during staining. The mucous secretion forms a gel-like coat that adheres to the epithelial surface and provides protection against the acid content secreted by the glands. As a result of that, these cells also contains high quantities of HCO3-, to neutralize H+  Lamina propria: composed of loose connective tissue, lymphatic nodules and the gastric glands  Salva Garcia Noguera MU-Pleven 2016-2017  Muscularis mucosae: composed of two relatively thin layers, the inner is circular and the outer one is longitudinal. They play a role in facilitating the gastric secretion  Submucosa: consists of dense connective tissue containing adipose tissue, lymph vessels and Meissner’s plexus, the part of the enteric nervous system that plays an important role controlling the secretion of the glands. Stomach glands Histologically the stomach can be divided into three parts according to the nature of the glands. It is necessary to remember that the glands are located in the lamina propria and secrete its content in the gastric pits:  Glands of fundus and body: simple tubular glands that possess 5 types of cells: o Chief of peptic cells: basophilic cells involved in the protein secretion. These cells are located in the lower half of the glands and have the characteristics of protein secreting cells, with a well-developed RER and Golgi complex. The main function of these cells is the secretion of pepsinogen, which in contact with HCl will convert into pepsin, the active proteolytic enzyme o Parietal or oxyntic cells: acidophilic cells found in the upper-middle portion of the glands and related to the HCl secretion. They are pyramidal cells that have intracellular branching canaliculus which open in the lumen of the gland through the apical membrane of the cell. These canaliculi also have microvilli, which increases the surface of the cells to facilitate the secretion of HCl. The partal cells are responsible for the secretion of HCl and intrinsic factor, a glycoprotein that complexes with vitamin B12, which is necessary for the absorption in ilium o Enteroendocrine or argentaffin cells: can be found at any level of the fundic glands, but mainly on the bottom part of the glands. These cells are easily stained with stains containing silver and contain secretory granules which contain hormones to regulate the activity of the GIT. They have also been called as gastroenteropancreatic endocrine cells because of this function. Instead of secreting in the lumen of the gland, they do so in the lamina propria, where hormones are collected by vessels o Mucous neck cells: located in the neck region, they are similar to the mucous glands located in the epithelial lining of the stomach but smaller  Glands of the cardiac: compound tubular glands that secrete mucus. They are located in the oesophageal orifice and their secretion contributes to the protection of the abdominal oesophagus from the gastric secretions. As a result of that they are composed of mucous cells and we can also find some enteroendocrine cells  Glands of the pylorus: compound tubular glands with similar composition as the glands of cardiac. The mucous glands prevent neutralize the acid when the stomach content is emptied in the duodenum.  Salva Garcia Noguera MU-Pleven 2016-2017 Muscular layer The gastric muscular layer is composed of:  Outer longitudinal layer  Middle circular layer  Inner oblique layer The arrangement of these layers is important as they are related to the role of mixing the chime during the digestive process. They are also related to the process of pushing the partially digested chime to the duodenum through the pyloric sphincter. The innervation of these muscle layers is by the myenteric plexus, which is present throughout the whole length of the GIT and innervates the muscular layer Serosa layer It is continuous with the peritoneum of the abdominal cavity via the omentum. The greater omentum is a large apron-like fold of visceral peritoneum that hangs down from the greater curvature of the stomach to the transverse colon. The gastrosplenic ligament is part of the greater omentum. The lesser omentum is the double layer of peritoneum that extends from the liver to the lesser curvature of the stomach (hepatogastric ligament) and the first part of the duodenum (hepatoduodenal ligament). Blood supply and lymphatic drainage The arterial blood supply for the stomach includes branches that come from the celiac trunk:  Left gastric artery from the celiac trunk  Right gastric artery from the common hepatic artery  Right gastro-omental artery from the gastroduodenal artery  Left gastro-omental artery from the splenic artery  Posterior gastric artery from the splenic artery The venous drainage is by veins that follow the arteries and have similar names. Ultimately empty into the portal vein, and the most important ones are:  Right and left gastric veins  Right and left gastro-omental veins  Short gastric vein  Salva Garcia Noguera MU-Pleven 2016-2017 The stomach has a rich network of lymphatics that connect with lymphatics draining the other visceral organs of the upper abdomen. At the gastro-oesophageal junction the lymphatics are continuous with those draining the lower oesophagus, and in the region of the pylorus they are continuous with those draining the duodenum. In general, they follow the course of the arteries supplying the stomach. Innervation The stomach is innervated by sympathetic and parasympathetic fibers:  Sympathetic: originate from T5-T12 spinal segments, and is mainly distributed to the stomach via the greater and lesser splanchnic nerves via the coeliac plexus. The gastric sympathetic nerves are vasoconstrictor to the gastric vasculature and inhibitory to gastric musculature  Parasympathetic: The parasympathetic supply to the stomach is from the anterior and posterior vagus nerves. The parasympathetic gastric supply is secretomotor to the gastric mucosa and motor to the gastric musculature. It is responsible for coordinated relaxation of the pyloric sphincter during gastric emptying. Embryology The stomach appears as a dilatation of the foregut caudal to the oesophagus during the fourth week of development. After that, it enlarges and rotates clockwise about 90 decrees, with the right side of the stomach lying posteriorly (right vagus nerve) and the left side oriented anteriorly (left vagus nerve).  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 53: Duodenum The small intestine is the longest part of the gastrointestinal tract and extends from the pyloric orifice of the stomach to the ileocecal fold. This hollow tube, which is approximately 6 to 7 m long with a narrowing diameter from beginning to end, consists of the duodenum, the jejunum, and the ileum. Parts of the duodenum The first part of the small intestine is the duodenum. This C-shaped structure, adj acent to the head of the pancreas, is 20-2gcm long and is above the level of L1-L3. It is retroperitoneal organ on all of its parts except for its beginning, which is connected to the liver by the hepatoduodenal ligament, a part of the lesser omentum. The duodenum is divided into 4 parts:  Superior part: extends from the pyloric orifice of the stomach to the neck of the gallbladder, is just to the right of the body of vertebra L1. It passes anteriorly to the bile duct, gastroduodenal artery, portal vein, and inferior vena cava. It is the only intraperitoneal part together with the stomach.  Descending part: it is located just to the right of midline and extends from the neck of the gallbladder to the lower border of vertebra L3. Its anterior surface is crossed by the transverse colon, posterior to it is the right kidney, and medial to it is the head of the pancreas. This part of the duodenum contains the major duodenal papilla, which is the common entrance for the bile and pancreatic ducts, and the minor duodenal papilla, which is the entrance for the accessory pancreatic duct  Inferior part: it is the longest section, crossing the inferior vena cava, the aorta, and the vertebral column. It is crossed anteriorly by the superior mesenteric artery and vein  Ascending part: passes upward and to the left side of the aorta at the level of L2 and terminates in the duodenojejunal flexure. This duodenoj ejunal flexure is surrounded by a fold of peritoneum containing muscle fibers called the suspensory muscle (ligament) of duodenum (ligament of Treitz).  Salva Garcia Noguera MU-Pleven 2016-2017 Microscopic structure of the duodenum Functionally the small intestine is the principal site for the digestion of food and absorption of products of digestion. The chyme from the stomach is received by the duodenum, where the enzymes from the pancreas and the bile from the liver are also delivered. Enzymes located in the glycocalyx and microvilli of the enterocytes (intestinal absorptive cells) also contribute to the digestion of the chyme. The layers of the intestine, as in the whole GIT are:  Tunica mucosa  Tunica muscularis  Tunica serosa Tunica mucosa In order to increase the absorptive surface are there are several specialization in the mucosa and submucosa, these are:  Plicae circulares: permanent transverse folds that contain a core of submucosa (so lamina propria and muscularis mucosae also take part on them). These folds appear 5-6cm after the pyloric sphincter and are more numerous in the distal part of the duodenum. Conversely, its number is reduced in the middle of ilium  Villi: from the plicae circulares emerge several projections with a core of lamina propria and muscularis mucosae. These projections are longer in the duodenum, while in the distal parts of the small intestine they reach a minimum size.  Microvilli: the tunica mucosa of the small intestine is covered by a simple columnar epithelium, made up of enterocytes and other cells. At the apical part of the enterocytes we can find a striated border, the microvilli. The organelles of enterocytes are distributed in a polar way, with the nucleus centrally located. Above the nucleus we can find the Golgi complex, smooth endoplasmic reticulum and several vacuoles. Below the nucleus we find the RER and several mitochondria. Together with the enterocytes we can find other kind of cells:  Goblet cells: their apical cytoplasm is full with mucous globules, so these cells are important for the secretion of mucous Lamina propria The lamina propria of the tunica mucosa consists of loose connective tissue with several common structures as in other regions of the GIT:  Lymph nodules: the biggest ones are Payer’s patches, and extend through the muscularis mucosae and can also reach the submucosa  Gut-associated lymphatic tissue (GALT):  Crypts of Lieberkühn: tubular glands, perpendicular to the lumen of the small intestine with the aperture at the vase of the villi. These glands can be found throughout the whole length of the small intestine and are composed of the following cells: o Mucous cells: similar to goblet cells, are located in the upper portion of the gland o Paneth cells: located in the deepest part of the glands, are related to the secretion of lysozyme, an antibacterial substance  Salva Garcia Noguera MU-Pleven 2016-2017 o Stem cells: these are the most numerous cells, they occur in the middle part of the crypts and provide the source of most of the cell types of the intestinal epithelium. These cells have can be distinguished from the rest because they have less microvilli and the nucleus is basal and poorly developed o Enteroendocrine cells: scattered among the walls of the intestinal glands. Some types of these cells are:  K cell: secretes gastric inhibitory peptide  L cells: secrete glucagon-like peptide (GLP)  Decreases glucagon secretion  Increase insulin secretion  Inhibits acid secretion  I cells: secrete cholecystokinin (CCK)  Inhibit gastric emptying  Stimulates bile secretion  N cell: secrete neurotensin, which promotes smooth muscle contraction  S cell: secrete secretin, which stimulates the exocrine pancreas Muscularis mucosae It forms the base of the mucosa with external longitudinal and internal circular layers of smooth muscle cells. It follows the surface of the profiles of the circular folds and sends strands into the core of villi. Lamina submucosa It is composed of loose connective tissue with the usual structures (vessels, lymph nodes…). It forms the core of plicae circulares and contains the Meissner plexus, which controls the secretion of the Lyeberkühn crypts. The main distinction between the duodenum and the other parts of the small intestine are the Brunner glands, which are acinar glands located in the submucosa. These glands composed of short columnar epithelial mucous cells secrete mucus and large quantities of HCO3- to neutralize the acid secreted from the stomach. These glands are only found in the duodenum and are also important because they secrete trypsinogen- activating factor, for the conversion of trypsinogen to trypsin. Tunica muscularis The tunica muscularis is thicker in the proximal intestine, consisting of thin external longitudinal layer and thick internal circular layers of smooth muscle cells. Between both layers of muscle we can find the Myenteric plexus, which regulates the contraction of the smooth muscle and causes the peristaltism and segmentation movements. Tunica serosa It is the visceral peritoneum consisting of loose connective tissue covered by mesothelium, a membrane composed of simple squamous epithelium. Where the duodenum becomes retroperitoneal, it is mainly covered by a connective tissue adventitia rather than serosa.  Salva Garcia Noguera MU-Pleven 2016-2017 Blood supply and lymphatic drainage The arterial supply of the duodenum consists of branches from both, the celiac trunk and the superior mesenteric artery:  From celiac trunk o Supraduodenal artery o Branches from the gastroduodenal artery  Branches from anterior superior pancreaticoduodenal artery  Branches from posterior superior pancreaticoduodenal artery  From superior mesenteric artery o Branches from the anterior inferior pancreaticoduodenal artery o Branches from the posterior inferior pancreaticoduodenal artery  Branches from first jejunal artery In the case of the veins, the blood is collected by veins that have the same name and reach directly the portal vein or the superior mesenteric vein, which will later carry the blood to the portal vein. Duodenal lymphatics run to anterior and posterior pancreatic nodes that lie in the anterior and posterior grooves between the head of the pancreas and the duodenum: these nodes drain widely into the suprapyloric, infrapyloric, hepatoduodenal, common hepatic and superior mesenteric nodes. Innervation The duodenum is innervated by both parasympathetic and sympathetic neurones:  Sympathetic neurons: sympathetic axons originate from neurones in the intermediolateral columns of the grey matter in the T5-T12 and travel through the greater and lesser splanchnic nerves to the celiac ganglioin. Postganglionic axons are distributed to the duodenal wall via periarterial plexuses on the branches of the coeliac axis and superior mesenteric artery. The sympathetic nerves are vasoconstrictor to the duodenal vasculature and inhibitory to duodenal musculature.  Parasympathetic neurons: preganglionic parasympathetic supply is carried by vagal axons that are distributed via the coeliac plexus and which synapse on neurones in the duodenal wall. The parasympathetic supply is secretomotor to the duodenal mucosa and motor to the duodenal musculature Embryology It evolves from the lower part of the foregut  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 54: Small intestine As stated in the previous topic, the small intestine is composed of:  Duodenum  Jejunum  Ilium Parts of jejunum and ilium Both parts of the intestine are intraperitoneally located. The jejunum represents the proximal two-fifths. It is mostly in the left upper quadrant of the abdomen and is larger in diameter. Additionally, the inner mucosal lining of the jejunum is characterized by numerous prominent folds that circle the lumen (plicae circulares). The less prominent arterial arcades and longer vasa recta (straight arteries) compared to those of the ileum are a unique characteristic of the jejunum. The ileum makes up the distal three-fifths of the small intestine and is mostly in the right lower quadrant. Compared to the jejunum, the ileum has thinner walls, fewer and less prominent mucosal folds (plicae circulares), shorter vasa recta, more mesenteric fat, and more arterial arcades. The ileum opens into the large intestine, where the cecum and ascending colon join together. Two flaps projecting into the lumen of the large intestine (the ileocecal fold) surround the opening. The flaps of the ileocecal fold come together at their end, forming ridges. Musculature from the ileum continues into each flap, forming a sphincter. Possible functions of the ileocecal fold include preventing reflux from the cecum to the ileum, and regulating the passage of contents from the ileum to the cecum. The jejunum begins at the duodenojejunal junction, and the ilium ends at the ileoceacal junction. The coils of the small intestine are attached to the posterior abdominal wall by a fan-shaped fold of peritoneum known as the mesentery of the small intestine. The root is narrow, about 15 cm long and is directed obliquely from the duodenojejunal flexure (left side of the L2) to the ileocaecal junction (right sacroiliac joint). This section of the small intestine is located centrally in the abdominal cavity and lies behind the transverse colon and the greater omentum. The long free edge of the fold encloses the mobile intestine and prevents friction between its course. The short root of the fold is continuous with the parietal peritoneum on the posterior abdominal wall. The root of the mesentery allows the entrance of the following structures into the space between the two layers of peritoneum:  Salva Garcia Noguera MU-Pleven 2016-2017  Branches of superior mesenteric artery  Branches of superior mesenteric vein lymph vessels  Nerves There are 3 mesenteries, and the function of all them is to hold the organs in place to the posterior abdominal wall. The mesenteries are:  Mesentery of the small intestine  Transverse mesocolon  Sigmoid mesocolon Microscopic structure of the small intestine Functionally the small intestine is the principal site for the digestion of food and absorption of products of digestion. The chyme from the stomach is received by the duodenum, where the enzymes from the pancreas and the bile from the liver are also delivered. Enzymes located in the glycocalyx and microvilli of the enterocytes (intestinal absorptive cells) also contribute to the digestion of the chyme. The layers of the intestine, as in the whole GIT are:  Tunica mucosa  Tunica muscularis  Tunica serosa Tunica mucosa In order to increase the absorptive surface are there are several specialization in the mucosa and submucosa, these are:  Plicae circulares: permanent transverse folds that contain a core of submucosa (so lamina propria and muscularis mucosae also take part on them). These folds appear 5-6cm after the pyloric sphincter and are more numerous in the distal part of the duodenum. Conversely, its number is reduced in the middle of ilium  Villi: from the plicae circulares emerge several projections with a core of lamina propria and muscularis mucosae. These projections are longer in the duodenum, while in the distal parts of the small intestine they reach a minimum size.  Microvilli: the tunica mucosa of the small intestine is covered by a simple columnar epithelium, made up of enterocytes and other cells. At the apical part of the enterocytes we can find a striated border, the microvilli. The organelles of enterocytes are distributed in a polar way, with the nucleus centrally located. Above the nucleus we can find the Golgi complex, smooth endoplasmic reticulum and several vacuoles. Below the nucleus we find the RER and several mitochondria. Together with the enterocytes we can find other kind of cells:  Goblet cells: their apical cytoplasm is full with mucous globules, so these cells are important for the secretion of mucous Lamina propria The lamina propria of the tunica mucosa consists of loose connective tissue with several common structures as in other regions of the GIT:  Lymph nodules: the biggest ones are Payer’s patches, and extend through the muscularis mucosae and can also reach the submucosa  Gut-associated lymphatic tissue (GALT):  Crypts of Lieberkühn: tubular glands, perpendicular to the lumen of the small intestine with the aperture at the vase of the villi. These glands can be found throughout the whole length of the small intestine and are composed of the following cells:  Salva Garcia Noguera MU-Pleven 2016-2017 o Mucous cells: similar to goblet cells, are located in the upper portion of the gland o Paneth cells: located in the deepest part of the glands, are related to the secretion of lysozyme, an antibacterial substance o Stem cells: these are the most numerous cells, they occur in the middle part of the crypts and provide the source of most of the cell types of the intestinal epithelium. These cells have can be distinguished from the rest because they have less microvilli and the nucleus is basal and poorly developed o Enteroendocrine cells: scattered among the walls of the intestinal glands. Some types of these cells are:  K cell: secretes gastric inhibitory peptide  L cells: secrete glucagon-like peptide (GLP)  Decreases glucagon secretion  Increase insulin secretion  Inhibits acid secretion  I cells: secrete cholecystokinin (CCK)  Inhibit gastric emptying  Stimulates bile secretion  N cell: secrete neurotensin, which promotes smooth muscle contraction  S cell: secrete secretin, which stimulates the exocrine pancreas Muscularis mucosae It forms the base of the mucosa with external longitudinal and internal circular layers of smooth muscle cells. It follows the surface of the profiles of the circular folds and sends strands into the core of villi. Lamina submucosa It is composed of loose connective tissue with the usual structures (vessels, lymph nodes…). It forms the core of plicae circulares and contains the Meissner plexus, which controls the secretion of the Lyeberkühn crypts. The main difference between the duodenum and the other parts of the small intestine is that the latter ones lack Brunner glans in the lamina submucosa. Tunica muscularis The tunica muscularis is thicker in the proximal intestine, consisting of thin external longitudinal layer and thick internal circular layers of smooth muscle cells. Between both layers of muscle we can find the Myenteric plexus, which regulates the contraction of the smooth muscle and causes the peristaltism and segmentation movements. Tunica serosa It is the visceral peritoneum consisting of loose connective tissue covered by mesothelium, a membrane composed of simple squamous epithelium. Where the duodenum becomes retroperitoneal, it is mainly covered by a connective tissue adventitia rather than serosa.  Salva Garcia Noguera MU-Pleven 2016-2017 Blood supply and lymphatic drainage The blood supply of the jejunum and ilium is by the superior mesenteric artery and its branches. The superior mesenteric artery arises from the abdominal aorta, and supplies arterial blood to the organs of the midgut – which spans from the major duodenal papilla (of the duodenum) to the proximal 2/3 of the transverse colon. It arises anteriorly from the abdominal aorta at the level of the L1 vertebrae, immediately inferior to the origin of the coeliac trunk. The main branches are:  Inferior pancreatoduodenal artery (does not irrigate the small intestine)  Middle colic artery  Right colic artery  Ileocolic artery  Jejunal arteries  Ileal arteries The venous drainage is by the superior mesenteric vein, which drains the small intestine, caecum, ascending and transverse parts of the colon. It receives the following veins and later unites with the splenic vein behind the neck of the pancreas to form the portal vein:  Jejuneal vein  Ileal vein  Ileocolic vein  Right colic vein  Middle colicvein  Right gastroepiploic vein  Pancreatoduodenal veins The lymphatic drainage is similar to the large intestine, through the superior and inferior mesenteric lymph nodes and cisterna chyli. Innervation The ileum and jejunum are innervated by parasympathetic and sympathetic fibres via the superior mesenteric plexus:  Preganglionic sympathetic: originate from neurones in the intermediolateral grey matter of the mid-thoracic spinal segments (T5-T9) and travel in the greater and lesser splanchnic nerves to the superior mesenteric ganglion. Postganglionic axons accompany the superior mesenteric artery into the mesentery and are distributed along branches of the artery. The sympathetic nerves are vasoconstrictor to the vasculature and inhibitory to the musculature of the jejunum and ileum.  Preganglionic parasympathetic axons travel in the anterior and right vagus nerve and are secretomotor to the mucosa and motor to the musculature of the jejunum and ileum Embryology The small intestine develops from the midgut during the 5th week of embryonic life.  Salva Garcia Noguera MU-Pleven 2016-2017 Topic 55: Large intestine – cecum, appendix and colon The large intestine extends from the distal end of the ileum to the anus, a distance of approximately 1,5m in adults. Its main functions are the absorption of fluids and solutes and also to provide an environment for a large population of bacteria, some of which are responsible for the metabolism and absorption of vitamin B12 and vitamin K. The large intestine is composed of the following parts:  Cecum: lies in the right iliac fossa. The ilium opens in the cecum in the posteromedial part through the iliocecal valve. The cecum leads to the vermiform appendix  Colon: is divided into o Ascending: in the right lumbar and hypochondriac region to the inferior portion of the liver, where it bends forming the right colic flexure or hepatic flexure o Transverse: from the hepatic flexure to the left hypochondriac region forming the left colic flexure or splenic flexure o Descending: from the left colic flexure descending through the left lumbar region and iliac region to the lesser pelvis o Sigmoid colon: loop of the colon that continues in the lower posterior pelvic cavity  Rectum: continuation of the sigmoid colon, and after that the anal canal Differences large intestine / small in