GI 1 Flashcards
Digestive System Composition
alimentary canal, tongue, teeth, salivary glands, pancreas, and liver.
Define Alimentary Canal
Hollow tube of varying diameter beginning at the oral cavity including esophagus, stomach, small and large intestine.
Name the 4 layers of the alimentary canal
Mucosa, Submucosa, Muscularis Externa, mesothelium (either serosa or adventitia)
Mucosa of alimentary canal
faces the lumen. Contains lining epithelium, lamina propria (loose CT), and muscularis mucosa
Submucosa of alimentary canal
dense CT. vascular plexus to mucosa. Nerve plexus called submucosal plexus or Meissner’s plexus.
Muscularis Externa of alimentary canal
mostly smooth muscle. Upper esophagus is skeletal muscle and middle esophagus is mixed muscle types. Organized into 2 layers with a nerve plexus in the middle.
Inner Circular layer
part of the muscularis externa circling the espophagus
Outer longitudinal layer
part of the muscularis running along the espophagus
Auerbach’s Plexus
aka myenteric plexus. Nerve layer of muscularis externa that lies between the inner circular and outer longitudinal layers
Serosa
thin layer of CT underlying mesothelium wihtin the peritoneal cavity.
Adventitia
Portion of the alimentary canal not within the peritoneal cavity is covered with this portion of mesothelium. It lacks simple squamous epithelium and has loose CT that blends into surrounding structures
Mesothelium
Simple squamous epithelium covering the alimentary canal within the peritoneal canal
Oral Cavity
differs from alimentary canal proper due to lack of muscularis externa or serous/advetnitia.
Oral Mucosa
non-keratinzed stratified squamous epithelium with the exception of adult hard palate, gingiva, and tongue keratinization.
Oral Submucosa
No clear distinction from lamina propria. Contains the minor salivary glands.
Minor Salivary Glands
mucous-secreting branched tubular or tubuloaveolar glands. They are intrinsic (within wall of oral cavity).
Tongue
muscular organ projecting into the oral cavity. Covered in SSE that is often keratinzed in adults. Contains both intrisic and extrinsic skeletal muscle fibers as well as 4 types of papillae.
Filiform papillae
most abundant type of lingual papillae. Small concical projections of highly keratinized epithelium and CT. NO TASTE BUDS just mechanical role. Cover whole anterior tongue with backwards projections/tips.
Fungiform Papillae
Mushroom shaped projections scattered amoung filiform papillae and more numerous at the tip of the tongue. Apical surface of these buds carry the taste buds.
Circumvallate papillae
Large circular dome-shaped structures on the back of the tongue and 8-12 in number. Each papillae is surrounded by a groove or moat containing taste buds. Lingual salivary glands (von ebners glands) empty into these grooves. The groove lining is of thinner epi.
Foliate Papillae
parallel low ridges on lateral sides of tongue with numerous taste buds in the grooves between adjacent papillae. Lingual salivary glands (von ebners) also empty into these grooves.
von Ebner’s glands
lingual salivary glands that empty their serous secretions into the grooves between circumvillate or foliate papillae. The serous secretion flushes material from the groove to allow taste buds to respond to changing stimuli.
Taste Buds
found in fungiform, circumvallate, and foliate papillae as well as within the oral cavity. They are oval pale-staining structures that extend the thickness of epi. They have small opening called a taste pore. Made up of several cells including sensory and support cells. Stimulation of these cells results in nerve impulse in postsynaptic sensory nerve.
Major Salivary Glands
Main role: produce saliva extrinsic glands with a secretory part, duct system, and stoma
Roles of saliva
- lubricate oral cavity and moisten food 2. begin digestion of carbs with digestive enzmes 3. antibacterial effect and control microbial growth within oral cavity and caries 4. immunoglobulin A 5. source of calcium and phosphate ions for tooth development
Stroma of Major salivary Gland
capsule of dense CT surrounding the gland as well as creating septa/lobules and fine network of CT support for acini and ducts of gland. Frequently contain adipocytes.
Secretory Part
contains 3 types of acini: serous, mucous, mixed as well as myoepithelial cells that help with secretion
Serous acini
protein secreting, euchromatic central nucleus, basophilic basal part of cell (RER), pyramidal in shape resulting in round acini
Mucous Acini
mucous-secreting cells, heterochromatic basally placed nuclei, apical part of cell stain pale, columnar cells resulting in tubular shaped acini
Mixed (seromucous) acini
tubular mucous component and a serous cap or demilune
Myoepithelial cells
non-secretory cells present within the acini with contractile function around basilar part of acinar secretory cells
Intralobular ducts
within a lobule with a striated duct segment and intercalated duct segment
Interlobular ducts
between lobules; stratified columanr epithelium
Main ducts
ducts running from the gland to the oral cavity, are very large, become SSE as it enters the oral cavity
Intercalated ducts (of intralobular)
begin at the secretory acini and lined with low cuboidal epithelium and containing basal nuclei.
Striated ducts (of intralobular)
connect intercalated ducts to interlobular ducts and are lined with SCE. They have infoldings of their plasma membrane lined with mitochondria. This structure is important for reabsorbing ions to alter pH of saliva, make it hypotonic. Striations/foldings in basal part of cell result in nucleus being pushed to middle or top of cell.
Parotid Salivary Gland
largest type, located below and in front of ear, contains long duct to oral cavity, completely serous
Submandibular Glands
relatively large and located in floor of oral cavity. Mixed glands with more serous acini than mucous acini. Serous demilunes are often seen.
Sublingual Glands
small glands in the floor of the oral cavity containing mixed glands with more mucous than secretory acini. Serous demilnes can also be seen here.
Tumors of Salivary Glands
usually in major glands. 80% tumors benign. Most common is pleomorphic adenoma, composed of ductal and myoepithelial cells.
Esophagus
fixed muscular tube that delivers food and liquid formthe oral cavity to the stomach
Esophageal Mucosa
non-keratinized SSE, less cellular lamina propria, entirely longitudinal muscularis mucosa.
Barrett’s Esophagus
metaplasia of the esophageal epithelium, resulting in displacent of the normal SSE with specialized intestinal columnar epi. Caucasian males over 50. often result of GERD. Most common precursor of esophageal adenocarcinoma.
Esophageal Glands
within mucosa and submucosa. Both secrete mucous to lubricate and protect luminal wall. Mucosal/cardiac glands and eso glands proper are the two types of eso glands
Mucosal Eso Glands (Eso Cardiac Glands)
only in terminal part of eso (sometimes the beginning)
Esophageal Glands Proper
located within submucosa. Small compound tubulaveolar glands scattered along the length of the esophagus.
Esophageal Submucosa
dense irregular CT, numerous blood vessels and lymph vessels. Nerve and ganglion within submucossa form the Meissner’s or submucosal plexus. Contains eso glands proper.
Muscularis Externa of Esophagus
2 layers of muscle: inner circular and outer longitudinal. Contains skeletal in certain regions. Skeletal>mixed>smooth. Covered with adventitia and loose CT belnding into surroundings. Distal portion is serosa. (Where it meets stomach)
Meissner’s Plexus
Nerve fibers and ganglion found in the submucosa of esophagus
