GI - Mouth through stomach

From Iusmhistology

• started here on 02/09/2011 at 1PM.

Contents 1 GI 1.1 Oral cavity 1.1.1 Lip 1.1.2 Hard palate 1.1.3 Tongue 1.1.4 Taste buds 1.1.5 Gingiva 1.1.5.1 Pulp cavity 1.1.5.2 Periodontal ligament 1.2 Gut tube 1.2.1 Mucosa 1.2.2 Submucosa 1.2.3 Muscularis 1.2.4 Serosa 1.3 Esophagus 1.4 Stomach 2 Lab 15: Digestive Tract I 2.1 A. ORAL CAVITY. 2.1.1 1. Lip, slide 47 2.1.2 2. Oral mucosa 2.1.3 3. Tongue 2.2 B. ESOPHAGUS 2.3 C. STOMACH 2.3.1 1. Body and Fundus 2.3.2 2. Pyloric Stomach

[edit] GI

• The duodenum is where the pancreatic duct terminates as well as the bile duct.
  • Bile salts are for emulsifying fats and foods.
• Jejunum and ilium are histo indistinguishable.
• Duodenum has some secretions that make it distinct
• LI:
  • Cecum, colon, rectum
  • Can't be visually discerned.

[edit] Oral cavity

• Lined with non-kera stratified epith.
  • Still have nucleus and organelles.
• The oral cavity between the epithelium are the lamina propria and submucosa.
• There are small salivary glands.

[edit] Lip

• There is a skin surface.
  • Red region is vermillion where the caps come to the surface.
  • Mucus membrane on the tooth side.
• Notice that the skin is much thinner than the mucus.
  • The epithelium against wet surfaces is usually thicker (mucus membrane).
• The vermillion is the hairless part of the epithelium.
• There are also glands.
• The transition from the keratinized part (outside skin) to non keratinized (musu membrane)
  • Vermillion

[edit] Hard palate

• Parakeratinized = for dealing with rough surfaces
• Hard palate and tongue deal with lots of tough material.
• In the mucus mebrane, there are nuclei at the surface but stain a little differently.
  • We call this parakeratinized.
  • They stain differently because they are toughed to deal with rough food.

[edit] Tongue

• Bumps are called papillae.
• Filiform papillae provide roughness.
  • Cats have very sharp, extended filiform papillae.
• Filiform are rod like and have a parakeratinized surface.
• Fungiform papillae have bulbous ends.
  • These are the red bumps on our tongues.
  • Fungiform DO NOT have parakeratinized.
• Circumvallate papillae
  • In the back.
  • Have a valley.
  • Valleys are flushed by serous glands called glands of Von Ebner.
• Filiform and fungiform in the front.
• Circumvallae in the back.
• Foliate papillae
  • Most humans have very few
  • Leaf shaped.
  • Not very useful.
• Geographic tongue
  • 2% of people have this
  • Comes with eating certain foods.
  • A kind of psoriasis of the tongue.
  • In the red area, the filiform papillae have retracted.
  • Edges of the ridges have enhanced thickness of the epithelium.

[edit] Taste buds

• Found especially around the circumvalae and in the middle of the fungiforms.
• 5 kinds of tastes: staly, sweet, sour, bitter, umami (glutamate, freshness).
• Taste cells with receptors on the tip; communicate with afferents.
• Basal cells are the stem cell.
• There is a pore in the epithelial cells for each taste bud (only by EM).

[edit] Gingiva

• Gingiva = gums of the mouth.
  • Very well connected to the tooth.
  • The epithelial attachment of gottlieb is where the gum epithelial cells attach to the mineral surface of the tooth.
• Sulcus is the space measured to see if there is some pathology.
  • Deeper = unhealthy (perhaps gingevitis).
• Enamel covers the crown.
  • Mostly appetite
  • 96% calcium salts
  • Has some proteins but no collagen.
  • Proteins are secreted by ameloblasts during tooth development deep in the gums.
  • And there's no replacing it!
  • Laid down in rod shapes, packed very tightly; makes it very hard.
• Cementum covers the root.
  • Cementocytes secrete this.
  • Cementum is very much like bone.
• Tooth sits in the alveolus (a bony cavity).
  • This bone goes through fast turn-over, making it a woven type of bone.
  • Alveolus just means something that is shaped like a cucumber.
• Dentin
  • Makes up the bulk of the tooth (into the root, up into the crown).
  • Harder than bone.
  • Matrix of Type I collagen
  • Odontoblasts make dentin
  • Odontoblasts reside in the pulp cavity and project through the dentinal tubules (dentinal processes).
    • These tubules are problably how we detect hot and cold with our teeth.

[edit] Pulp cavity

• Extends to the apical foramen (hole at the bottom of the tooth root).
• The pulp cavity is inside the root and crown.

[edit] Periodontal ligament

• Run between cementum and the alveolar bone.
• A set of bundles of collagen bound at one end on the tooth cementum (root of the tooth) and to the alveolar bone (supporting bone).
• The ligament distributes the force of the tooth throughout the whole alveolus.
  • Like a bicycle tire and spokes.
• This is a type I collagenous structure.
  • When the structure is rope-like it is generally Type I.
• It turns over pretty quickly.
• Scurvvy: teeth fall out because ligament doesn't get regnerated becuase new collagen can't be generated.

[edit] Gut tube

• Mucosa is the inner-most layer of the tubular gut
• Then connective tissue: sub-mucosa
  • Most nerves and blood vessels
• Muscularis externa
  • Main muscle layer
  • Thickest
• Serosa
  • CT with or without mesothelium

[edit] Mucosa

• Three layers: epithelium, lamina propria (CT), muscularis mucosae
• Lamina propria = nearby layer.
• Muscularis mucosae = muslce of the mucosa

[edit] Submucosa

• CT
• Some glands
  • Important for identifying some organs
• Arteries and nerves

[edit] Muscularis

• Missed this.

[edit] Serosa

• Technically means "CT with mesothelium".
• Without mesothelia, it is just an adventitia.

[edit] Esophagus

• Statified squamous non-ker epithelium (like oral cavity)
• Lamina propria:
  • Has no glands (for the most part)
  • Muscularis mucosae: has longitudinal muscle, not continuous
  • Know these three properties!
• The submucosa does have glands
  • Provide lubrication for the esophagus.
• Muscularis externus
  • Have inner circular and outer longitudinal muscle layers
  • In the upper 1/3 the muscle is skeletal
    • Makes sense because the first part of swallowing is voluntary.
  • in the middle third, mixed
  • Lower third is smooth muscle
• Serosa
  • Mostly just CT (adventitia)
  • Where it penetrates the diagragm (last part), has a mesothelia covering (so a true serosa).

[edit] Stomach

• Txn from esoph to stomach: squamous non-kera epith to simple columnar epithelium.
• Also, we start to see tubular glands.
• There are four parts: cardia (ring where esoph and stomach meet), fundus, body (fundus and body look same histologically), and pylorus (looks different).
• Lned with surface mucus cells.
• Surface invaginates into pits where glands empty.
• Diff between pit and gland:
  • Pit is an invagination, covered with surface mucous cells.
  • Glands empty contents into pits; not made of surface mucus cells.
• Rugae are longitudinal folds in the stomach for expansion.
  • A fold in the mucosa of the stomach.
  • The whole mucosa folds up, not the muscularis externae.
  • In the center is the submucosa.

• The cardia has pits with some mucusy glands.

• The fundus / body have glands with a neck and base (base stains more basophilically).
  • At the base, staining dark are chief cells that make pepsinogen so they have lots of protein production and packaging stuff that makes them dark.
  • Parietal cells of the fundus / body make acids.
    • Sometimes have two nuclei.
  • The neck region has parietal and undiffed cells.
  • Base has parietal and chief cells.
    • Recall that chief are much darker staining (basophilic).

• The pylorus has deep pits and shorter mucusy glands.

• Pylorus into the small intestine:
  • Pits and glands convert into villi.

[edit] Lab 15: Digestive Tract I

[edit] A. ORAL CAVITY.

[edit] 1. Lip, slide 47

• Note that the epidermis of skin on the outer surface is thinner than the epithelium on the mucosal surface.
• Contrast the appearance of the dermis and the connective tissue underlying the mucosa.
• Compare the epithelium and the accessory structures on each surface. The epithelium on the mucosal surface is non-keratinized.
• Glands beneath this epithelium are compound seromucous glands.
• The organization of the mucosa in the oral cavity is not as well defined (structurally) as the wall of the tubular gut. The oral mucosa has no muscularis mucosae, so that the lamina propria is continuous with the submucosa. This is difficult to see. We expect you to distinguish between lamina propria and submucosa in the tubular gut, but not in the oral cavity.
• The red margin of the lip may be difficult to detect. Dermal papillae are much taller here resulting in a thinner overlying epidermis. They also contain a prominent bed of capillaries.
  • How does this affect the color of this region in life?

[edit] 2. Oral mucosa

• Slide 43.
• uvula; and slide 46, soft palate. Both
• The oral surface is lined by non-keratinized stratified squamous epithelium
  • (What type lines the respiratory surface?).
• The oral surface also displays large mucous glands deep to the lamina propria.
  • What tissue type lies deep to the glands?
• Note that this portion of the tract lacks a muscularis mucosae and a muscularis extema.
• As with the lip, a submucosa will not be readily distinguishable from the lamina propria on these slides.
• What is the function of the mucosal glands of the labial, buccal and palatine surfaces?

[edit] 3. Tongue

• Study slide 41 for general features of the lingual mucous membrane and musculature.
• Filiform papillae are abundant on the dorsal surface.
• The epithelium is described as parakeratinized-the top several layers are pale (similar to the stratum corneum of skin) but all cell layers have nuclei (no anucleate squames).
• Some slides will show one or more fungiform papillae.
  • Do these have taste buds? Yes
  • If so, where are they located?
• What type of muscle is found in the tongue?
• How does organization of these muscle fibers relate to the function of the tongue?
• Slide 42 contains a circwnvallate papilla.
• Where are the taste buds located?
• The serous glands of von Ebner are associated with this papilla.
• Find the secretory cells of these glands and the duct that carries their product to the surface of the tongue.

[edit] B. ESOPHAGUS

• The upper region of the esophagus is on slide 48 (adjacent to trachea); the lower region is

on slide 52.

• The esophagus is the first of the tubular organs of the G.I. tract.
• Identify the various layers in the wall according to the generalized scheme for tubular digestive organs (see Lecture Notes, text and atlas).
• What specific type is it?
• What kind of muscle is present in the muscularis mucosae?
  • (This will be harder to see on slide 52.)
• Are there any mucosal glands?
• Are there any submucosal glands?
• Where do the ducts empty?
• Examine the muscularis extema.
  • How many layers?
  • What is the direction of the muscle fibers in each layer?
• Compare the muscle types in the upper and lower portions of this organ.
  • What type of muscle is present in each portion? Is the adventitia covered by a mesothelium?

[edit] C. STOMACH

[edit] 1. Body and Fundus

. Use slide 53 to initially study the various layers in the wall. What are rugae? What layers ofthe wall are involved? Note that various planes of section through the rugae can complicate the morphological appearance of the mucosa. Histology of the mucosa: Compare the epithelial cells lining the luminal surface, the gastric pits, and the gastric (fundic) glands. What are their respective secretions? Is a brush border present on any of the cells? (no) Note that the glands discharge their secretion into the base of the gastric pits, which carry it to the mucosal surface. Be able to distinguish between chief and parietal cells at the histologic and ultrastructural levels ( ftnd examples of TEM' s in your text and atlas- such as Basic Histology 15-22, 15-24). Know their typical location within the gland, and their function. Also know that mucous neck cells and enteroendocrine cells occur in the glands (identification not required). Gastric glands are found in the fundus and body of the stomach.

[edit] 2. Pyloric Stomach

. Slide 54 contains the distal portion ofthe body and the proximal portion of the pyloric stomach. Compare the histology of the two regions. Pay particular attention to the pyloric glands. What kind of cells make up this epithelium? Where is the muscularis mucosae in relation to the pyloric glands? Enteroendocrine cells are present, but not stained. Slide 40 is a section through the pylorus showi.llg both pyloric stomach and duodenum. (Note: The surface epithelium of the duodenum is missing in most of this specimen, but other structures are well preserved.) What type of muscle forms the pyloric sphincter? 69

• stopped here on 02/09/2011 at 2PM.