Oral Cavity and GI Track Flashcards

1
Q

Parts of the Oral Cavity

A
  • Oral cavity proper
    • hard and soft palates superiorly
    • tongue/floor of mouth inferiorly
    • entrance to oropharynx posteriorly
  • Vestibule
    • space sperating lips and cheeks from alveolar ridges and teeth
  • Tongue
  • Salivary glands
  • Tonsils
  • Teeth, periodontal ligament, and gingiva
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2
Q

Oral Cavity

Lining

A
  • Lining mucosa is non-keratinized
    • Vestibule
    • Floor of the mouth
    • Underside of the tongue
    • Cheeks
  • Masticatory mucosa either keratinized or parakeratinzied
    • gingiva
    • parts of the hard palate
  • Parakeratinized epithelium
    • similar to keratinized
    • surface cells have visible pyknotic nuclei
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3
Q

Tongue

A

Anterior portion is free.

  • Inferior surface covered by minimally keratinized stratified squamous
  • Superior surface has two seperate regions seperated by the sulcus terminalis
    • Anterior 2/3
      • covered by lingual papillae
        • Covered by varying stratified squamous epithelium
        • 4 types:
          • ​Filiform
          • Fungiform
          • Vallate
          • Foliate
    • Posterior 1/3
      • more irregular due to lingual tonsils

Posterior portion is anchored to the floor of the mouth and hyoid bone.

Bulk of the tongue is formed of interlaced bundles of skeletal muscles.

  • Some arise outside of the tongue → extrinsic muscles
  • Some completely contained within the tongue → intrinsic muscles
  • Bundles of adipose tissues seperates muscle bundles
    • Allows greater mobility
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4
Q

Lingual Papillae

Distribution

A
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5
Q

Filiform Papillae

A
  • Most numerous
  • Thin, conical shape curved posteriorly
  • Covered with maximally keratinized stratified squamous epithelium
  • No taste buds
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6
Q

Fungiform Papillae

A
  • Narrow bases and slightly rounded top
  • Covered with very thinly keratinized stratified squamous
  • Less numerous and slightly taller than filiform papillae
    • Scattered among them
  • Numerous underlying capillary loops gives redder tint
  • Taste buds on dorsal surface
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7
Q

Circumvallate Papillae

A
  • Located in V-shaped line just anterior to sulcus terminalis
  • Fewer in number (6-12)
  • Covered in stratified squamous which may be keratinized
  • Largest lingual papillae
  • Surrounded by a deep sulcus or valley
  • Ducts of serous von Ebner glands open into sulci
  • Have ~ 250 taste buds located on the sides of each papilla
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8
Q

Foliate Papillae

A
  • Located on posterolateral aspect of tongue
  • Covered in minimally keratinized stratified squamous
  • Appears as vertical ridges seperated by furrows
  • Few taste buds
  • Serous glands open into sulci between the papillae
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9
Q

Taste Buds

A
  • Most located on fungiform or vallate papillae
  • Clusters of 60-80 elogated cells
  • Large at bases forming ovoid body
  • Narrow superficial ends of cells converge around a taste pore
  • Cell types:
    • basal cells stem cells
    • neuroepithelial cells
    • supporting cells
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10
Q

Salivary Glands

A

Major salivary glands:

Parotid, Sublingual, Submandibular

Minor salivary glands:

Lingual, Labial, Buccal, Molar, Palatine

  • Compound tubuloacinar glands
  • Secretory cells organized into acini → lobules → lobes
    • Serous, Mucous, or Mixed
  • Intercalated duct → intralobular duct → striated duct → interlobular duct
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11
Q

Parotid Glands

A
  • Serous only
  • Produces 30% salivary volume

Inset → Serous acinar at higher magnification.

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12
Q

Submandibular Glands

A
  • Mixed glands
    • Mostly serous acini
    • Some mucous acini with serous demilunes
  • Producse 60% of salivary output
  • Short intercalated ducts
  • Long striated ducts

Left inset → mucous acini with serous demilune

Right inset → striated duct

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13
Q

Sublingual Glands

A
  • Mostly mucous
  • May have some serous demilunes
  • No pure serous acini
  • Intercalated & striated ducts short

Inset → serous demilune

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14
Q

Tonsils

General

A
  • Aggregates of lymphoid tissues
  • Encircles oral cavity and pharynx
  • Forms the tonsillar (Waldeyer’s) ring
  • Often has significant lymphocytic infiltration
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15
Q

Lingual Tonsils

A
  • Embedded in the dorsal surface of posterior 1/3 of tongue
  • Numerous
  • Luminal surface covered by minimally keratinized stratified squamous epithelium
  • Each tonsil has a single shallow crypt
  • Parenchyma composed of lymphoid tissue
    • Mostly secondary nodules with germinal centers
  • Thin capule seperates deep surface of each tonsil from CT of tongue mucosa
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16
Q

Palatine Tonsils

A
  • Paired tonsils, one on each side of opening from oral cavity to oropharynx
  • Minimally keratinized stratified squamous
  • Each tonsil has 10-20 deep, branching crypts
  • Parenchyma of mostly secondary nodules
  • Seperated from underlying tissue by dense CT capsule
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17
Q

Pharyngeal Tonsil

A
  • Unpaired pharyngeal tonsil
  • Located in roof of nasal pharynx
  • Called adenoids when enlarged or inflammed
  • Covered by pseudostratified columnar epithelium with patches of stratified squamous
  • Surface with folds or pleats
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18
Q

Dental Formula

A

The number and types of teeth in each quadrant of mouth.

(incisor, canine, premolar, molar)

Adult: 32 teeth with dental formula 2:1:2:3

Deciduous dentition: 20 teeth with dental formula 2:1:2

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19
Q

Parts of a Tooth

A
  • Crown
    • Projects above gum line
    • Dentin covered by enamel
    • Cusps - raised ridges at the occlusal surface
  • Root
    • Part below gum line
    • Holds tooth in alveolus
    • Dentin covered by cementum
  • Neck (Cervix)
    • Where crown and root meet at cemento-enamel junction (CEJ)
  • Pulp
    • Internal part of tooth
    • CT with blood vessels, lymphatics, and nerves
      • Enter at apical foramen
    • Houses odontoblasts
      • Important in formation of dentin
  • Periodontal Ligament
    • Extends from cementum to periosteum of alveolar bone
    • Holds tooth in body socket
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20
Q

Enamel

A
  • Dense calcified material
    • 95% inorganic material
    • NO collagen
    • Proteins involved in mineralization process
  • Covers crown of tooth
  • Avascular & acellular after eruption
    • Cannot be repaired
  • Deposited as elongated rods
    • Extends thickness of enamel layer from dentin-enamel junction to external surface
  • Formed by Ameloblasts
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21
Q

Dentin

A
  • Forms bulk of tooth
  • Covered by:
    • enamel in the crown
    • cementum in the root
  • Avascular
  • Maintains nerve suppy inside dentinal tubule
  • Similar composition to bone but more mineralized
  • Secreted by Odontoblasts
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22
Q

Cementum

A
  • Calcified external covering of tooth root
  • Derived from dental sac (dental follicle)
  • Similar but less mineralized than bone
  • Formed by cementoblastscementocytes
  • Cellular cementum
    • cementocytes housed in lacunae
    • communicate through canaliculi
  • Acellular cementum
    • found closest to junction with enamel or dentin
  • Continuous production of cementum throughout life
  • Reasorbed by odontoclasts
    • during exfoliation process
    • due to trauma
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23
Q

Pulp

A
  • Loose, mucoid CT
  • Forms innermost tissue of tooth
  • Supoortive function including continued formation of dentin
  • Sensory and immune functions
  • Lined by cell bodies of odentoblasts
  • Contains:
    • fibroblast-like cells
    • reticular fibers
    • collagenous fibers
    • GAGS
  • Highly innervated and vascularized
    • Nerve endings can enter dentinal tubules
24
Q

Periodontal Ligament

A
  • Fibrous CT
  • Collagen type I fibers arranged to exert tension on bone with chewing
  • Anchors tooth in alveolar socket
    • Connects cementum to alveolar bones via Sharpey’s fibers
  • Derived from dental sac
25
Gingiva
* **Dense irregular CT** * Covered by **keratinized or parakeratinized stratified squamous epithelium** * Very thick basement membrane * Surrounds teeth in alveoli * Covers the alveolar processes
26
Odontogenesis Overview
27
Odontogenesis Stage 1: Initiation
1. **Oral epithelium** _thickens_ through mitosis * Derived from **ectoderm** of stomodeum (primitive mouth) 2. Dividing cells _invaginate_ into underlying **ectomesenchyme** * neural crest derived 3. Forms _horseshoe shaped_ band of epithelial cells called **dental lamina** * Present in upper and lower jaw * Seperated from ectomesenchyme by **basal lamina**
28
Odontogenesis Stage 2: Bud Stage
* On each jaw: * 10 seperate areas of mitotic activity form knob like swellings called **tooth buds** * Each surrounded by **ectomesenchyme** * Develops **asynchronously** according to order of emergence
29
Odontogenesis Stage 3: Cap Stage
Deep surface of each tooth bud invaginates to form the **tooth germ**. Consists of: * **_Enamel organ_** (ectodermal origin) * **Outer enamel epithelium (OEE)** * Simple epithelium on _convex surface_ * Provides protective barrier during amelogenesis * **Inner enamel epithelium (IEE)** * Simple epithelium on _concave surface_ * Continueous with OEE at cervical loop * Cells differentiate into **ameloblasts** * **Stellate Reticulum** * Forms _core of enamel organ_ * Lies between OEE and IEE * Loosely woven tissue with layers of star-shaped cells * Helps support enamel production * **_Dental papilla_** * Formed by condensed **ectomesenchymal cells** in the _indentation of the enamel organ_ * Responsible for the formation of the pulp and dentin * **_Dental sac (dental follicle)_** * Formed by **ectomesenchymal cells** surrounding _tooth germ_ * Gives rise to cementum, peridontal ligament, gingiva, and alveolus
30
Odontogenesis Stage 4: Bell Stage
1. Cells of **tooth germ proliferate** * Increased size * Development of **bell shaped concavity** 2. **Stratum intermedium** layer develops * Lies between stellate reticulum and IEE of enamel organ * Produces **growth factors** that _regulate ameloblast and odontoblast differentiation_ 3. Cells of **IEE** differentiate _first_ into **ameloblasts** * Apical **Tome's process** will guide formation of enamel 4. This induces mesenchymal cells of **dental papilla** to differentiate into **odontoblasts** * Have extended **odontoblastic processes** that will extend through **dentinal tubules** as dentin forms
31
Odontogenesis Stage 5: Appositional Stage
1. **Dentin** production starts **first** * **Odontoblasts** secrete **predentin** * Includes organic components that will mineralize over time via matrix vesicles 2. This stimulates **ameloblasts** to secrete **enamel** 3. _Dentin and enamel_ meet at the **dentin-enamel junction (DEJ)** 4. Dentin _develops in layers_ moving odontoblasts away from DEJ 5. **Odontoblastic process** develops and elongates into the **dentinal tubule** 6. As enamel develops forming **enamel rods**, ameloblasts also move away from DEJ 7. Once _full thickness_ of enamel matrix formed in a particular area, ameloblasts **lose their Tome's process** → no longer actively secreting. 8. When **tooth erupts**, enamel can no longer regenerate because OEE and IEE (including ameloblasts) lost.
32
Odontogenesis Stage 6: Root Formation
* Root formation begins after completion of crown. * _Growth of tooth root_ **stimulates tooth eruption**. * **Cervical loop of Bell** (formed of fused OEE and IEE) grows down to form **Hertwig's root sheath.** * Peripheral cells of **root dental papilla** differentiate into **odontoblasts** * Begin producing **root** **dentin** * As Hertwig's root sheath elongates, more root is produced. * As dentin is formed, root sheath becomes _perforated_. * **Ectomesencymal cells** from **dental sac** migrate through openings in root sheath. * Cells differentiate into **cementoblasts** and begin forming **cementum**.
33
Development of Permanent Dentition
* On lateral side of each **deciduous dental germ**, ectodermal cells form **successional lamina** * Forms **precursors** of 20 of the 32 permanent teeth * Those without deciduous precursors form from **posterior extensions of dental lamina**
34
Digestive Tube General Structure
1. **_Mucosa:_** composed of 3 layers * **Epithelial layer** * _Simple columnar_ except in esophagus and anus * Glands extend from epithelium into lamina propria or submucosa * **Lamina Propria** * _Cellular loose CT_ * Houses lymphoid tissue * **Muscularis mucosae** * Smooth muscle * Thin and two layers in most locations * Inner circular layer * Outer longitudinal layer 2. **_Submucosa_** * _Dense fibroelastic CT_ * Houses arteries which send branches into mucosa and muscularis externa * Houses **Meissner's submucosal plexus** * Walls of gut may have folds with core of submucosa * **Rugae** in stomach * **Plicae circularis** in intestine 3. Muscularis externa * _Smooth muscle_ except in upper esophagus * Two layers: Inner circular & outter longitudinal * **Auerbach's myenteric plexus** located between layers 4. **_Serosa or Adventitia_** * **Adventitia** * _CT_ surrounding an organ * Outermost layer of **retroperitoneal parts** * **Serosa** * _Mesothelium_ (serous membrane) plus underlying _CT coat_ * Outermost layer of **intraperitoneal parts**
35
Enteric NS
* Innervates digestive tube, pancreas, and gallbladder * Can control GI function with or without CNS input * Includes both sensroy and motor neurons * Two plexuses: 1. **Submucosal plexus (Meissner's)** * Controls secretory, absorptive, and vascular functions 2. **Myenteric plexus (Auerbach's)** * Controls peristalsis * _Parasympathetic_ input increases gut mobility and glandular secretions; relaxes sphincters. * _Sympathetic_ input decreases gut mobility and glandular secretions; activates sphincters.
36
Esophagus Structure
* **_Mucosa_** * **Minimally keratinized stratified squamous** * Langerhans cells * **Muscularis mucosae** * absent in upper part * becomes thicker going down * only one layer of longitudinal cells * **Cardiac glands** * **​**Superior/inferior portions * Secrete **neutral mucus** * **_Submucosa_** * Lots of elastic fibers * **Esophageal glands proper** * Compond tubuloalveolar glands * Produce **acidic mucus** * **_Muscularis externa_** * Superior 1/3 → striated muscle * Middle 1/3 → mixed * Inferior 1/3 → mixed * _Thoracic portion_ covered by **adventitia** * _Short abdominal portion_ covered by **serosa**
37
Stomach Regions
* **Anatomical:** * Cardia * Fundus * Body * Pyloris * **Histological:** described based on types of glands * Cardiac * Fundic → fundus + body * Pyloric
38
Stomach Wall Structure
* **Mucosa** * Covered with **simple columnar surface mucus cells** * **​**secrete mucus which is _alkaline, viscous, PAS+_ * apices filled with secretory granules → **apical cup** * Invaginates forming **gastric pits** * **1-7 gastric glands** open into base of gastric pit * Length of pits and type of glands varies by region * Lamina propria surrounds glands * **Submucosa** * _dense irregular CT_ * many elastic fibers * many blood and lymphatic vessels * **Muscularis externa** * Contains _additional_ innermost layer of smooth muscle → **oblique layer** * Circular layer complete * Forms **pyloric sphincter** at distal end * Intraperitoneal → covered by **serosa** * Non-distended stomach thrown into temporary folds → **rugae** * Includes mucosa and submucosa
39
Fundic Glands
* **Oxyntic glands** are the most complicated * Glands are long and straight * _Three regions in each gland:_ 1. **Isthmus** * Opens into gastric pit * Lined mainly by surface mucous cells 2. **Neck** 3. **Base/body** * Deepest and longest part * _Five cell types:_ 1. **Mucous neck cells** * In neck ⋙ body * Similar to surface lining cells without apical cup * Secretes **soluble mucus** 2. **Regenerative (stem) cells** 3. **Parietal cells** * Eosinophilic * Produce **HCl** and **gastric intrinsic factor** * **Intracellular canaliculi** at apical end lined with short microvilli * **Tubulovesicular system** in cytoplasm surround canaliculi in inactive cells * During HCl secretion, tubulovesicular system _fuses_ with canaliculi 4. **Chief Cells** * Most common at bases * Basophilic * Produces: * **Pepsinogen** * **Rennin** * **Gastric lipase** 5. **DNES cells** * Scatters within glands * Called **enteroendocrine cells** in the gut * At least 15 types in the gut * **A → glucagon** * **D → somatostatin** * **ECL → histamine** * **G → gastrin** * Produce and secrete hormones into lamina propria
40
Cardiac Glands
* **Shallowest pits** * **Short, coiled glands** * Most cells are **mucous cells** * Resemble those in the esophagus * Secrete **neutral mucous** * There are some mucous neck cells, pareital cells, and DNES cells * **DNES cells** in this region mainly produce **gastrin**
41
Pyloric Glands
* **Gastric pits are the deepest** * **Glands are short, branched, and twiste**d * Similar cells to the cardiac glands * Most common are **mucous cells** * Neutral mucus * Also produces **lysozyme**
42
Small Intestine Wall Structure
* **_Mucosa_** * **Simple columnar epithelia** * Forms outer surface of villus * **Lamina Propria** * Forms core of the villi * Dense network of capillaries * One or two lacteals * Surrounds intestinal glands * **Muscularis mucosae** * Inner circular layer extends into villi * Contracts rhythmically * **_Submucosa_** * Dense irregular CT with many elastic fibers * Contains **Meissner's submucosal plexus** * Site of **Brunner's glands** in Duodenum * **_Muscularis externa_** * Responsible for **peristalsis** * **Auerbach's myenteric plexus** lies between two muscle layers * At the _distal ileum_, thickened to form the **ileocecal sphincter** * **Serosa** in most places * The retroperitoneal part of the duodenum with **adventitia**
43
Small Intestine Adaptations for Surface Area
1. **_Plicae circularis_** * circumferential folds of **mucosa and submucosa** * found in duodenum, jejunum, and proximal 1/2 of lieum * permanent 2. **_Villi_** * projections of the **mucosa** * finger-like to leaf-like * **simple columnar epithelial** * **core of lamina propria** * usually not found overlying aggregates of lymphoid tissue 3. **_Microvilli_** * surface projections on enterocytes * contain **actin and myosin** * coated with **thick glycocalyx**
44
Enterocytes Small Intestinal
* Intestinal absorptive cells * Closely packed microvilli * Thick glycocalyx * Functions: * Absorb proteins and carbs * Absorb fats * Secretion of enzymes * Peptidases & disaccharidas * Transcytosis of IgA
45
Goblet Cells Small Intestine
* Produce **mucinogens** → mucins after absorbing water * Density increases as you go along tract * Acidic mucus
46
DNES Small Intestine
47
M-Cells Small Intestine
* Scattered among enterocytes overlying areas of **lymphoid aggregation** * Peyer's patches * Appendix * Broad cells * Apical surface folded into interconnected ridges or **microfolds** * Basal surface with deep invagination between cell and basement membrane * Filled with lymphocytes and APCs * Transport Ag via **transcytosis** from lumen to APC in pockets
48
Crypts of Lieberkühn
* **Simple tubular glands** * Located in **lamina propria** & extends to **muscularis mucosae** * Open into **spaces between bases of villi** * Secrete **isotonic fluid** to lubricate digestive contents * Contains: * Enterocytes * Goblet cells * DNES cells * **Paneth cells** * Regenerative cells
49
Paneth Cells
* Found in crypts of Lieberkühn * Remain at the bottom of the crypt throughout 20 day life span * Contain **large strongly eosinophilic apical granules** * Structure of protein secreting cells * Synthesize _antibacterial substances_: * **lysozyme** * **𝛼-defensins** * Some also **transport IgA** from lamina propria to lumen via transcytosis
50
Brunner's Glands
* Found in the **submucosa of the duodenum** * **Branched coiled tubular mucous glands** * Ducts pierce the muscularis mucosae * Usually open into the crypts of Lieberkuhn * Produces **clear alkaline mucus high in bicarb** * Also secretes **human epidermal growth factor**
51
Peyer's Patches
* Found in the ileum ⋙ jejunum * 30-40 of them * each has 10-200 lymphatic nodules that often extend into submucosa * M-cells common in overlying epithelium → dome epithelium
52
Cecum and Colon Morphology
Cecum → Colon → Rectum → Anal Canal * **_Mucosa_** * Simple columnar epithelium * No villi * Many intestinal glands → Crypts of Lieberkühn * No Paneth cells * More goblet cells than found in the small intestine * Numerous surface absorptive cells * DNES rare * Lamina propria * No lymphatics * **_Submucosa_** * Form temporary folds which involve mucosa and submucosa * **_Muscularis externa_** * Inner circular layer complete * Outer longitudinal layer thin or absent * Except for three thick evenly spaced longitudinal bands call **taeniae coli** * All layers of the intestinal wall bulge out between bands forming **haustra** * Intraperitoneal parts have a **serosa** * cecum, transverse colon, sigmoid colon * small tags of fat called **appendices epiploicae** hang from serosa * Retroperitoneal parts covered by **adventitia** * ascending and decending colon
53
Rectum Morphology
Similar to the rest of the large intestine except for special features below: * Mucosa thrown into **two or three transverse rectal folds** * Located just distal to dilated region called the **rectal ampulla** * Muscularis externa has **two complete layers** * No taeniae coli
54
Anal Canal Morphology
Similar to the rest of the large intestine except for special features below: * **_Mucosa_** * In _upper portion_: * Forms **anal columns of Morgagni** * Lower ends of columns joined by folds called **anal valves** * Valves and lower ends of columns form the **pectinate line** where: * Endodermally derived superior canal ⇒ ectodermally derived lower canal * Simple columnar ⇒ minimally keratinized stratified squamous ⇒ maximally keratinized in lower portion * Intermediate region of **stratified cuboidal and/or stratified columnar** often present * In **lower portion**: * Minimally ⇒ maximally keratinized in lower portion * Contains **hair follicles** * **Mucous anal glands** extend into lamina propria * Large **apocrine circumanal glands** * **_Submucosa:_** * Upper canal contains the **internal rectal venous plexus** * **_Muscularis externa_** In the lower portion: * Circular layer ⇒ **internal anal sphincte**r ⇒ involuntary * Longitudinal layer replaced by **fibroelastic sheet** * _Skeletal muscles of pelvic floo_r ⇒ **external anal sphincter** ⇒ voluntary
55
Anus
* Perianal skin contains * Eccrine sweat glands * Apocrine sweat glands * Hair follicles with sebaceous glands
56
Vermiform Appendix
* Extends from the cecum * Often contains debris * Epithelial surface contains: * goblet cells * intestinal absorptive cells * DNES cells * M cells replace goblet cells near lymph nodules * Intestinal glands * **short and distorted** * Infrequent Paneth cells * Lamina propria almost **completely filled with lymph nodules** distributed around entire periphery * Has a serosa