-Ibrahim Al-Naser. -Dr Al- Muhtaseb. 1 P a g e

Transcription

1 -1 -Ibrahim Al-Naser - -Dr Al- Muhtaseb 1 P a g e

2 The Digestive System The doctor started the lecture by talking about the class rules. The GI system is an organ system, it is divided into: The Alimentary tract (also known as GI tube): A tube that begins by an opening (the mouth) and ends in the anal canal. Accessory digestive organs: The tongue and teeth. The salivary glands. The liver. The gallbladder. The pancreas. Each one of these accessory organs has a duct which opens in the alimentary tract. The Mouth (oral) cavity The mouth is the first organ in the alimentary tract. The oral cavity is a cavity that has 2 openings: An anterior opening (The mouth). A posterior opening (Isthmus of the fauces also known as the Oropharyngeal Isthmus). Anterior opening: The mouth The mouth is a cavity which is bound superiorly and inferiorly by the lips. The lips: We have 2 lips; an upper and a lower lip. In the middle of the upper lip we have a depression (groove) known as The Philtrum. This groove is only found in the upper lip. Differences between the inside and the outside of the lip: - Outside: Each lip (both the upper and the lower) are covered by skin, the type of epithelium here is stratified squamous keratinized. In which we can find hair follicles, sebaceous glands and sweat glands. 2 P a g e

3 -The core is Orbicularis Oris: Orbicularis Oris is a striated muscle, it has a circular fibers, it is innervated by the facial nerve, it acts as a sphincter and it is important in the whistling action. (A sphincter muscle is a circular muscle which surrounds an opening). -Inside we have the mucosa (the place where there are glands): here the epithelium is stratified squamous non-keratinized, and it has a large number of minor(labial) glands. -Transitional zone (vermilion zone): It is called the red zone, it has epithelium That is modified squamous, so we can t find hair follicles, sebaceous glands or sweat glands. It contains a large number of vessels and nerve ends that make it red and very sensitive. Posterior opening: Oropharyngeal Isthmus (Isthmus of the Fauces): This opening leads to the pharynx (we can think of the mouth as a bridge), because it allows the passage of the food to the pharynx. It has a roof, floor and two sides: The roof: soft palate in the middle ends by the Uvula The floor: posterior third of the tongue (the lymphatic part of the tongue). And the upper part is composed of the Hard palate. On both sides of the opening we have the Palatine tonsils. Palatine tonsils Their function is to filter the foreign bodies, which makes it subjected to infections (tonsillitis, which is very common in children). Tonsillitis: is inflammation of the tonsils, common in Children (rare in adults). If tonsillitis is recurrent (3-4 times per year) or persistent, Tonsillectomy is done (Surgical removal of the tonsils) because the infection may spread and reach the heart, muscles, kidneys and other organs. 3 P a g e

4 Palatine tonsils are found between 2 folds: -The palatoglossal fold (anterior one): inside it we have the palatoglossal muscle. -The palatopharyngeal fold (posterior one): inside it we have the palatopharyngeal muscle. The mouth s parts: Mouth proper The vestibule Mouth proper: The cavity inside the closed teeth. The Boundaries: Roof: is formed by the hard palate in front and the soft palate behind. Floor: the anterior two thirds the tongue. Sides: the teeth and cheeks (remember: buccinator muscle). Posteriorly: the isthmus of the fauces (which leads to the pharynx). The vestibule: It is where you move the tooth brush to brush your teeth (the upper and lower jaw are closed. It is a space between the cheeks, lips and the closed teeth. Boundaries: Anteriorly by lips. On the sides by the cheeks. Its importance: The duct of the parotid gland opens in it, more specifically at the level of the upper second molar tooth in the vestibule. It also contains minor glands. The vestibule and the mouth proper are connected through an opening which is located behind the last molar tooth. 4 P a g e

5 Salivary Glands: In the GI tract we have 3 pairs of large salivary glands: 1. The parotid gland which is found in front of the ear: serous gland. 2. The submandibular gland: mixed (seromucous) gland. 3. The sublingual gland: mucous gland. All these glands have ducts, and their secretions reach the oral cavity. Also, we have hundreds of minor salivary glands (e.g. Labial, palatine, etc...). The mucosa of the oral cavity: The type of epithelium is stratified squamous non-keratinized epithelium. Two types: Soft (elastic): it makes the Frenulum. The fold of mucosa is called frenulum. We have three frenula (plural of frenulum) of the mucosa: -Superior labial frenulum: which connects the inner surface of upper lip to the mouth. -Inferior labial frenulum: which connects the inner surface of lower lip to the mouth. -Lingual frenulum: which connects the inferior surface of the tongue in the midline to the floor of the mouth. Hard (tough): The mucosa on the upper and lower jaws becomes hard. The mucous membrane of the gingiva, or gum, is strongly attached to the alveolar periosteum. There is an elevation of mucosa below the tongue which is covering the sublingual gland. The submandibular duct of the submandibular gland opens onto the floor of the mouth on the summit of a sublingual papilla (bunch) on either side of the lingual frenulum. 5 P a g e

6 The innervation of the mouth: Roof: The upper jaw is supplied by branches of the maxillary nerve (Greater palatine nerve and Nasopalatine nerve). Floor: The lower jaw is supplied by branches of the mandibular nerve (the lingual nerve). The lingual nerve is the general sensation for the oral cavity like pain, temperature and touch. The taste: You should know that the taste is a special sensation; we have lingual papillae (taste buds) found on the dorsum of the tongue, particularly on the anterior 2/3 of the tongue. The Chorda tympani (a branch from the facial nerve) originates from the taste buds, supplies them and send messages to the brain about the taste. Remember: The facial nerve and facial palsy (paralysis of the facial nerve, causing muscular weakness in one side of the face. Cheek: The buccal nerve, a branch of the mandibular division of the trigeminal nerve (the buccinator muscle is innervated by the buccal branch of the facial nerve (Motor branch)). The teeth: It is accessory digestive organs inside the oral cavity and embedded in the gingiva (the gum). Two types: Deciduous (milk) and permanent. 6 P a g e

7 Deciduous: There are 20 deciduous teeth: four incisors, two canines, and four molars in each jaw They begin to erupt about 6 months after birth, all of them will have erupted by the end of 2 years. The teeth of the lower jaw usually appear before those of the upper jaw, specifically the incisors of the lower jaw. Permanent: There are 32 permanent teeth: four incisors, two canines, four premolars, and six molars in each jaw. The last molar is called third molar or wisdom tooth, and it has complications associated with it, it causes pain and may require surgical removal. They begin to erupt at 6 years of age. The last tooth to erupt is the third molar, which may happen between the ages of 17 and 30 The teeth of the lower jaw appear before those of the upper jaw. The function of the teeth: Important in mastication (the process by which food is crushed by teeth). Muscles of mastication: There are four mastication muscles (very strong muscles). The temporalis muscle: -Origin: Temporal bone -Action: Elevation and retraction of mandible. The masseter muscle: -The strongest muscle in the body. -The most obvious muscle of mastication. -Action: It elevates the mandible causing a powerful jaw closure. The medial pterygoid and lateral pterygoid muscles. They are innervated by mandibular branch of the trigeminal nerve. They originate from the skull and insert in the mandible to supply the sufficient movement of the mandible during mastication. 7 P a g e

8 All of them elevate the mandible (close the jaw), EXCEPT lateral pterygoid muscle which depresses the mandible (open the jaw). The tongue: The tongue is a muscular organ, it has a dorsal surface and a lower surface (the lower is attached to the floor of the mouth). The tongue is divided into 2 halves: right and left by a midline groove. The muscles forming the mouth are symmetrical on both side, the nerve supply is paired (meaning that we have right and left nerve). It is also divided into (by foramen cecum and sulcus terminalis): Anterior two thirds. (It is where the taste buds are found). Posterior third. These 2 thirds are separated by: 1. Foramen cecum. - It is an embryologic remnant and marks the site of the upper end of the thyroglossal duct. 2. Sulcus terminalis (V-shaped sulcus). -In front of the sulcus terminalis we have circumvallate papillae: It is responsible for tasting bitterness. It is found in the anterior two thirds, but in the embryo it is a part of the posterior third, so it is innervated by glossopharyngeal nerve. Differences between posterior 1/3 and Anterior 2/3 Embryology Contents Innervation Posterior 1/3 Anterior 2/3 Develops from: The third pharyngeal arch in the embryo The lingual tonsil (lymphatic tissue) Glossopharyngeal nerve (posterior 1/3 + circumvallate) Develops from: The first pharyngeal arch in the embryo Taste buds (fungiform, filiform, circumvallate papillae) General sensation: the lingual nerve The taste: chorda tympani 8 P a g e

9 Taste buds: There are 2 types of taste buds: Circumvallate papillae: -Responsible for the tasting of bitter. Filiform papillae, fungiform papillae: -Found on the anterior third. -Responsible for tasting in general. Taste: Sweet: on the tip of the tongue. The sour and salt: the edges of the tongue. Bitter: circumvallate papillae (it is a common mistake that patients put medication directly on the bitter part). Mucous Membrane of the Tongue: On the lower surface: It is loose (it moves). Type: Stratified squamous non- keratinized epithelium. On the dorsum surface Has taste buds. Type: the Parakeratinized (modified) epithelium (it is not keratinized), this epithelium is subjected to injury and can regenerate; so, its type changes. The muscles of the tongue: Intrinsic muscles They are four muscles; their fibres go in different directions; they are named according to the direction of their fibres: 1. Longitudinal muscle: longitudinal fibres. 2. Transverse muscle: transverse fibres. 3. Oblique muscle: oblique fibres. 4. Vertical muscle: vertical fibres. These muscles are confined to the tongue and are not attached to bone. Action: Alter the shape of the tongue. Nerve supply: Hypoglossal nerve. 9 P a g e

10 Extrinsic muscles: Origin: Bones around the tongue. Insertion: The tongue. Four muscles (The name indicates the origin): 1. The genioglossus muscle: -Origin: Genial tubercle of the mandible. -Insertion: Posterior part and the base of tongue. -Action: it pushes the tongue outside of the mouth. 2. Styloglossus muscle -Origin: Styloid process of temporal bone. 3. Palatoglossus muscle -Origin: Palate bone 4. Hyoglossus muscle -Origin: Hyoid bone Action: Their main function is altering the tongue position allowing for protrusion, retraction, and side to side movement. All the intrinsic and extrinsic muscles are supplied by the hypoglossal nerve EXCEPT for the Palatoglossus muscle, it is supplied by the Pharyngeal plexus (Is a network of nerve fibers, it has sources from: glossopharyngeal nerve, Vagus nerve and the cranial part of the accessory nerve). Injury of the hypoglossal nerve: The Genioglossus muscle helps us in the diagnosis of the injury of the hypoglossal nerve. How? We said that the Genioglossus muscle is responsible for protrusion the tongue. When it contracts the tongue goes out straight (because the innervation is paired and the muscles are symmetrical on both sides). However, the injury of the hypoglossal nerve on either side will lead to the deviation of the tongue to the paralyzed side because the paralyzed side doesn t work and the innervation is no longer paired. To the test its function, you ask the patient to stick his/her tongue out. 10 P a g e

11 Movements of the Tongue: Protrusion: The genioglossus muscles on both sides acting together. Retraction: Styloglossus and hyoglossus muscles on both sides acting together. Depression: Hyoglossus muscles on both sides acting together. Retraction and elevation of the posterior third: Styloglossus and palatoglossus muscles on both sides acting together. Shape changes: Intrinsic muscles. Don t forget to refer to slides Best of luck 11 P a g e