Exam 3 - Gi tract pt 1

Question 1

What is the histology and functions of the lip?

Answer 1

• THe oral cavity is lined with mucous membrane lying on a vascular FECT layer
  
  • Stratified squamous epithelium
  • basement membrane
  • lamina propria
• THe lip is composed of a core skeletal muscle (obicularis oris) cells embedded into FECT and covered externally by skin
• An internal poorly keratinized, modified, stratified squamous epithelium lies on lamina propria with high papillae
• within the lamina propria are mixed and mucous glands
• Dermis has a rich plexus capillaries which are priminent at the free margin ofthe lip

Question 2

What is the historical structure of the cheek?

Answer 2

• Cheek
  
  • Structure similiar to the lip
  • one exception is the abdunant elastic fibers present in the submucosa
    
    • These are continuous with the fibers surrounding the striated muscle and the lamina propria
    • This arrangement gives a maxium of distensibility to the oral mucous membrane

Question 3

What three structure are derived from epithelial bud ?

Answer 3

• Epithelial bud becomes the…
  
  • enamel organ
    
    • forms enamel
    • caps the dental papilla
  • dental papillia
    
    • condensation of mesenchyme that gives rise to dentin and pulp
  • Dental sac (follicle)
    
    • CT sac surrounds the enamel organ and dental papilla and forms cementum and the peridontal membrane

Question 4

What is the different between the dental papilla and the enamel organ to their embroyonic origin and their derivatives ?

Answer 4

• Enamel organ forms enamel
  
  • enamel organ is formed from Ectoderm
• Dental papilla is the condensation of mesenchyme that gives rise to dentin and pulp
  
  • neural crest and mesoderm give rise to the dental papilla

Question 5

What is the dental lamina?

Answer 5

• The internal limb is the dental lamina that arises from the dental primordium
  
  • `dental primordium is formed from basal cells of oral ectoderm
• Cells proliferate to form the tooth buds (germs) in each half-jaw
• later a second set of tooth-buds develps on the lingual side of each d eveloping deciduous tooth three more posteriorly in each half-ajaw

Question 6

What is the histology and specfic functions of the odontoblasts?

Answer 6

• forms the dentin matrix throughout the life of the tooth
• forms single layer of cells lining pulp cavity
• tomes dentinal fibers (odontoblatic processes)
  
  • cytoplasmic extensions of odontoblasts continuing through the predentin and dentinal layers to the dentin enal junction
  • they occupy a space in the dentin matrix known as dentinal tubules
• Increment lines (of Ebner and Owen)

Question 7

What is the histology and specfic function of the ameloblasts?

Answer 7

• form enamel which covers only the tooth crown
• enamel is the hardest substance in the body
• enamel is 96% inorganic salts, about 90% of which is calcium phosphate in the form apatite crystals and 4% organic matter and water
• Enamel is laid down in prisms
• each prism is formed by one ameloblast
• secreting apical domains = tomes’ processes
• increment lines of retzius are periods of rhythmic growth

Question 8

WHat is the histology and specfic functions of the cementoblasts

Answer 8

Cememntum is formed from cells of dental sac differentiate into cementoblasts which despoit cementum on the dentin of the root from neck to apex. Cementum has coarse collagen fibers (sharpey’s) in bone-like calcified matrix.

Question 9

WHat is histology of the periodontal membrane?

Question 10

What is the function of the peridontal membrane ?

Answer 10

• CT formed from dental sac with fibroblasts, osteoblasts, cementoblasts, collagen fibers, blood vessels, and nerve fibers
• Highly metabolically active tissue
• binds cementum to bony socket
• sharpey’s fibers extend from cementum to alveolar wall via the membrane
• allows limited movement
• absorbs pressures of mastication and prevents this pressure from damaging alveolar bone
• affected by dieases such as diabetes and scurvy

Question 11

What is the sulcus terminalis ?

Answer 11

Seperates the anterior two-thirds of the upper oral portion of the tongue from the posterior one third of the tongue

Question 12

What are the four kinds of lingual papillae?

Answer 12

• Filiform papillae
  
  • most numerous of all the papillae with a conical appearance
  • evenly disturbed over the entire oral upper portion
  • lack taste buds
• Fungiform papillae
  
  • relatively few in number
  • interspersed singly among the parallel rows of filiform papillae
  • have a mushroom appearance
  • taste buds are present only the oral surface of the epithelium in contradistinction to the position of the taste buds on the circumvallate papillae whose taste buds are primarily located in the lateral walls
• Foliate Papillae
  
  • rudimentary in humans, but well developed in lower animals
  • the pharyngeal portion is free of papillae but contains the lingual tonsils
• Circumvallate papillae
  
  • located along the sulcus terminalis as projections surrounded by a moat (circular furrow)
  • Taste buds are present on the lateral walls
  • Ducts of Von Ebner glands (serous) open into the moat

Question 13

What is the structure of taste buds?

Answer 13

• Sustentacular Cells
  
  • Spindle cells
    
    • Spindle shaped support cells and arranged like barrel-to surround the inner taste pore at the base
  • Taste cells
    
    • Each cell is long and slender with an elongated central nucleus and terminates as short taste hair which projects into the external opening called the outer taste pore
    • process apical microvilli with taste receptors
    • basal part of cell reases neurotransmitters
    • Taste cells are distributed between the supporting

Question 14

What are the four layers of Digestive tube

Answer 14

• Mucosa (innermost)
  
  • Epithelium
    
    • stratified squamous transitioning to simple columnar
    • may have secretory, absorptive, and/or protectuve functions
  • Lamina Propria
    
    • loose areolar CT assocaiated with epithelium
    • Contains various glands and GALT (gut associated lympoid tissue)
  • Muscularis Mucosa
    
    • made up of one to three layers of smooth muscle
• Submucosa
  
  • dense, irregular connective tissue
  • vascularized
  • contains a nerve plexus: Meissner’s Plexus (submucosal Plexus)
• Muscularis externa
  
  • inner circular layer of smooth muscle
  • Outer longitudinal layer of smooth muscle
  • myenteric (aurerbach’s) nerve plexus lies between the two layers of muscle
  • Functions:
    
    • Regulates the size of the lumen (circular layer of smooth muscle)
    • REgulates rhythmic movement of the GI tract (longitudinal layer of smooth muscle )
• Outermost layer
  
  • Serosa
    
    • composed of dense irregular CT
    • Consists of a mesothelial lning and a layer of submesothelial
    • Forms visceral peritoneum
    • COvers intraperitoneal portions of abdominal organs
  • adventita
    
    • dense irregular ct with adipose tissue
    • covers retroperitoneal portions of digestive system

Question 15

what is the gut wall innervation?

Answer 15

• Sympathetic
  
  • Sympathetic postganglionic fibers pass through gut wall to gands and smooth muscle
• Parasympathetic
  
  • Preganglonic fibers synapse with postganglionic fibers in ganglia within the gut wall it self
  • Meissner’s plexus
    
    • regulates local secretions,blood flow, and absorption
  • Auerbac’sh plexus
    
    • coordinates muscular activity of gut wall

Question 16

What is GALT and what does it stand for?

Answer 16

• Gut Associated Lymphoid tissue
• IgA is the first line of defense and is found coating the luminal side of the muscosal epithelium
• Isolated lymph follicles are found in the lamina propria
  
  • Specialized squamous epithelial cells (M cells) in the gut lumen serve to transport food antigens to the lymph follicles
  • Antigen stimulated B cells in the follicle secrete IgA
• Diffuse lymphoid tissue in the lamina propria includes lymphocytes, macrophages, and IgA-secreting plasma cells
• Aggregated lymphoid follicles form the tonsils of the oropharynx (Waldeyer’s Ring) and Peyers PAtches in the submucosa of the ileum

Question 17

What is the function of the esophagus?

Answer 17

• Digestion (initated in the mouth)
• Addition of mucous to food bolus

Question 18

WHat is the strutural specializations of the esophagus

Answer 18

• Mucosa
  
  • stratfied squamous nonkeratinized epithelium
  • mucous glands are found in the lamina propria and submucosa
• Muscularis externa
  
  • undergoes transition from skeletal muscle in the upper third to a mixture of skeletal and smooth in the middle thrid to smooth muscle only in the lower third
• The Esophageal stomach and epithelial transition zone is frequent site of cancer
  
  • region b/w stratified squamous epithelium of the esophagus and simple columnar of the stomach
    *

Question 19

What is the structure of the stomach?

Answer 19

• Epithelial lining
  
  • gastric mucosa consists of a simple columnar epithelium with mucous coumnar cells
  • surface mucous cells secrete a protective insoluble mucous
  • Rugae
    
    • are longitudinal mucosal folds that are most priminat in an empty stomach
• Gastric Glands
  
  • open into gastric pits
• Muscularis externa
  
  • has three layers of smooth muscles
  • third layer is an innfer oblique layer

Question 20

What are the four regions of the stomach?

Answer 20

• Cardia
  
  • contains mostly mucous glands
  • close to the heart
• Fundus
  
  • contains gastric glands
    
    • long tubular gladns extending down to the muscularis mucosae
    • composed of mucous neck cells, parietal cells, chief cells, stem cells, and enteroendocrine cells
• Body
  
  • contains gastric glands
• Plyorus
  
  • contains mucous glands and hormone-secreting enteroendocrine cells

Question 21

What is the overall structure of the gastric glands?

Answer 21

• simple branched tubular glands
• narrow isthmus opens into bottom of a gastric pit
• Fundus (base) of the gland extends into lamina propria
• cells of the gastric glands
  
  • Mucous neck cells secrete soluble mucous
  • stem cells in neck replace other cells of the gastric pit
  • chief cell (zyomgenic cells)
    
    • secrete pepsinogen
  • Parietal cells (oxyntic cells)
    
    • manufacture HCL (creates an environment for pepsinogen)
    • Secretes intrinsic factor
  • Enterocrine cells (APUD cells)
    
    • amine precursose uptake and decarboxylation
    • diffuse neuroendocrine cells that secrete hormones

Question 22

What are parietal cells?

Answer 22

• Large pyramidal chaped, esinophillic cell
• produces HCL and gastric instrinsic factor
  
  • factor necessary for B12 absorption
• generates hydrogen ion from carbonic acid similiar to osteoclast
• prominent intracellular canaliculi lined with microvilli
• tubulovesicle pools are part of exocytosis -endocytosis function

Question 23

What is the chief cell?

Answer 23

Secretes pepsinogen (a protein digestive enzyme)

Question 24

What is an enteroendocrine cell

Answer 24

• Small cells with secretory vescles polarized toward basal surface in proximity to blood vessels
• produce peptide hormones and serotonin

Question 25

Question 26

Question 27