11.29.11+-+Gastrointestinal+System+I+-+Oral+Cavity+Through+Esophagus

11.29.11 - Gastrointestinal System I - Oral Cavity Through Esophagus


 * 1. Name the organs comprising the gastrointestinal (GI) tract proper.**

Mouth, pharynx, esophagus, stomach, duodenum, jejunum, ileum, large intestine (colon), rectum, anus.


 * 2. Identify the major glands and organs with ducts that open into the GI tract.**

Submandibular, sublingual, and parotid plands. Liver, pancreas, gallbladder, and appendix.


 * 3. Name and define the four tissue layers forming the tubular GI tract. Describe the different types of specializations that can be associated with these layers.**

Mucosa: composed of 3 layers: epithelium, lamina propria, muscularis mucosa.
 * Specializes in different regions for secretion and absorption patterns.
 * In the region we're talking about in this lecture (mouth, esophagus), the epithelium is stratified squamous.
 * The lamina propria is loose connective tissue
 * The muscularis mucosa is a thin layer of inner circumferential and outer longitudinal smooth muscle.

Submucosa: Composed of loose connective tissue with glands and an enteric nervous system called Meissner's plexus.

Muscularis externa: Composed of 2 smooth muscle layers.
 * The inner layer is circumferential.
 * The outer layer is longitudinal for most of the GI tract.

Adventitia or serosa: If there is no simple squamous epithelium (a mesothelium) the 4th layer is classified as adventitia. If a serous mesentery is present, it is classified as serosa.


 * 4. Define the terms:**

Submucosal plexus (of Meissner): Myenteric plexus (of Aurbach): Mesothelium: Serosa: Adventitia:
 * enteric/parasympathetic nerve plexus w/in connective tissue of submucosal layer.
 * between inner circumferential layer of smooth muscle and outer longitudinal layer of smooth muscle of muscular. Part of enteric nervous system; consists of sensory, motor, and interfibers; also receives/sends information to CNS
 * simple squamous epithelium on internal baso-lateral surface of serosa layer.
 * the most outer layer of the GI tract. Composed of loose connective tissue and mesothelium. Present in abdominal esophagus.
 * the most outer layer of the GI tract. Composed of loose connective tissue. Present in thoracic esophagus.


 * 5. Describe the type of epithelium lining the oral cavity.**

Stratified squamous epithelium lines the oral cavity. It is keratinized on the gingiva and top of tongue and non-keratinized on the cheeks, inner lips, and base of tongue.


 * 6. Describe the basic structure of adult tooth:**

enamel dentin gingiva pulp cavity root canal periodontal ligaments


 * 7. Describe the histologic layers of the tongue:**

There are two layers: mucosa and muscular.

Muscular: 4 intrinsic muscles of the tongue (superior and inferior longitudinal, vertical, and transverse) form the muscular layer.

Mucosa: Stratified squamous epithelium forms the mucosa layer along with lamina propria. Four types of papillae are formed by epithelium and lamina propria pegs. Their names are: vallate, foliate, fungiform, fans filiform.


 * 8. Describe the structure and distribution of (circum) vallate papillae.**

They are 15-20 papillae surround by trenches lying in a v-shape directly anterior to the terminal sulcus. The inner wall of the trench is embedded with taste buds. At the base of the trench are some special minor salivary glands called the serous glands of von Ebner that secrete saliva that keep the taste buds clear of gunk and transduce taste chemicals.


 * 9. Describe the structure and function of taste buds.**

Taste buds are formed by three cell types: sensory, supporting and basal.
 * The sensory and supporting cells form the extended petals of the bud
 * The (stem) basal cells form the baso-lateral base of the bud
 * The center of the taste bud opens at the taste pore to the lumen of the oral cavity
 * Five types of taste buds: umami, salt, sweet, bitter, sour


 * 10. Name and locate the three pair of major salivary glands:**

parotid: submandibular: sublingual:
 * in the cheek
 * all serous cells
 * intralobular --> intercalated --> striated --> interlobular ducts
 * w/ adipocytes
 * between the angles of the mandible
 * 50/50 serous and mucous cells
 * between the body of the mandible
 * mostly mucous cells, some serous cells


 * 11. Describe the general structure of major salivary glands. Include:**

Parenchyma: Stroma: Capsule: Septa: Lobules:
 * the functional portion of the glands,
 * arranged into lobules.
 * Composed of compound tubuloalveolar exocrine glands (epithelial tissue)
 * the supportive portion of the glands,
 * forms capsule and septa.
 * Composed of CT (type 1 collagen and reticular fibers), blood vessels, and nerves.
 * the outer layer of the gland;
 * formed of CT
 * the extensions of the CT from the capsule that divide gland tissue into lobules.
 * the clumps of glandular tissue divided by septa

Hilum: the place where duct and vessels enter the gland via the septa.

Innervation:
 * the autonomic nervous system innervates the salivary glands.
 * Sympathetic make thick organic viscous saliva (activates mostly mucous glandular cells)
 * Parasympathetic make much watery saliva (activates mostly serous glandular cells)


 * 12. Describe structural features of myoepithelial, mucous and serous cells of major salivary glands. Identify their functions:**

Myoepithelial cells: Mucous cells: Serous cells:
 * have contractile fibers, eject fluid into the duct from lumens of alveoli. They have dendritic arms and flat nuclei.
 * cytoplasm stains pale.
 * nucleus stains basophilic.
 * Present in tubules of submandibular and sublingual gland (mostly in sublingual gland).
 * cytoplasm acidophilic.
 * Nucleus stains basophilic.
 * Present in all 3 glands. Parotid composed of only serous cells. Arranged in alveoli.


 * 13. Describe the structure and function of major salivary gland ducts:**

Intralobular ducts: general type, not surrounded by much CT. Within lobules.

Intercalated ducts: simple cuboidal exiting from alveoli/tubule glands.

Striated ducts: Intercalated ducts come together to form striated ducts.

Interlobular ducts: Several striated ducts come together to form interlobular ducts. They pass through stroma out of lobules. Epithelium ranges from simple columnar to stratified cuboidal to pseudo stratified columnar. With goblet cells or without. Once near oral cavity become standard nonkeratinized stratified squamous of oral cavity.