a) site of abrasion (grinding of food)
b) surface lined with stratified squamous epith.

c) lamina propria below epith. followed by dense irr. CT
d) associated salivary glands secrete into oral cavity a product that contains:

-enzymes (amylase) starting CHO digestion
-mucous:wet and lubricate food

e) initiation of digestion

a) sensory and mechanical structure (moves food about in oral cavity and tastes it)
b) epithelia: stat. sq. epithelia w/keratinization, sensory organs (taste buds)

i) Buds are sensory organs involved in taste

ii) contain 3 cell types:

-Neuroepithelial cells:sensory neurons

-Supporting cells: neuroglial function?

-Basal cells: stem cell for others

 

iii) 4 taste senses: (why you use different shaped wine glasses for different wines)

-sweet: buds at or near the tip (anterior) of tongue

-salty: buds posterolateral to the tip

-bitter: buds at the back (circumvallate papilla)

-acid: all over

c) epithelial has elevations on dorsal aspect called papillae (4 types):

i) filiform: cover entire surface, elongate, conical shape
ii) fungiform: interspersed over the anterior 2/3 surface, mushroom shape, some contain taste buds on upper surface
iii) foliate: along the lateral edges of the tongue, about in the middle (a to p), ridge like structures with taste buds on the sides of the ridge
iv) circumvallate: large, few in number (7 -12), at the posterior of the tongue, numerous taste buds along the sides of the papilla

d) skeletal muscle arranged in many directions, hydrostatic-like device
e) salivary glands within tongue which drain primarily near taste buds to continually “wash” away the food material

- mostly serous gland associated with circumvallate papillae call von Ebner’s glands

f) dispersed lymphoid tissue and the lingual tonsils

 

a) mechanical tools to increase surface area of ingested food
b) resilient material attached to bone
c) tooth structure: (out to in)

i) enamel:

-very hard constituents: 95% HAP, 4.5% water, 0.5% organic matrix
- organic matrix: amelogenin, tuftelin (enamelins), laminin, (no collagen)
- made of elongated rods of HAP crystals bounded by inter-rod enamel, each rod extends the entire thickness of enamel layer
- enamel matrix synthesized by ameloblasts primarily, cells stop matrix production and die prior to tooth eruption (do not renew enamel)

ii) dentin:

-harder than bone, 70% calcium
-organic matrix: mostly type I collagen, dentin sialophosphoprotein, osteocalcin,
-organic matrix made by cells called ondontoblasts
-ondontoblasts line the interior surface of dentin
-ondontoblasts send processes into the dentin that traverse the thickness of the dentin layer

iii) pulp:

- innermost layer of tooth
- contains ondontoblasts and fibroblasts
- loose CT
- highly innervated and vascularized (tooth pain)

iv) cementum:

-covers the dentin in the root of tooth
-similar to bone (composition and matrix components)
-synthesized and maintained by cementocytes (derived from cementoblasts that line the periodontal ligament side of cementum)
-Sharpey’s fibers and Oxytalin fibers of the periodontal ligament attach to it

v) periodontal ligament:

- collagen that links tooth (via cementum) to alveolar bone of jaw
- contains both collagen fibers and oxytalin fibers
- high turnover rate and site of vitamin C deficiency effects

vi) alveolar bone:

-links with periodontal ligament
-bone that forms tooth socket
-remodelled when continuous strain is place on the tooth (braces)

vii) gingiva:

-mucous membrane firmly bound to periostium of jaw bones
-epithelium binds tightly to enamal via hemidesmosomes
-site called epithelial attachment of Gottlieb

d) tooth development:

i) Bud stage: proliferation and invasion of oral epithelium into underlying mesenchyme

ii) Cap stage: epithelium differentiates into inner enamel organ, the basal lamina of the epithelium is contiguous and separates the epithelial cells from the mesenchyme

iii) Bell stage: dental papilla is formed from ectomesenchyme and cells adjacent to the inner enamel organ (neural crest derived cells) differentiate into ondontoblasts. The epthetelium further develops into the enamel organ containing outer and inner enamel organ and stellate reticulum. The cells forming the inner enamel epithelium differentiate further into ameloblasts

iv) Appositional or secretory phase: The first matrix deposited is that of ondontoblasts giving a thin predentin layer. The basement membrane between the ameloblasts and predentin is degraded and the ameloblasts are stimulated to secrete enamel matrix. Further growth occurs with the predentin maturing into dentin forming a trilaminar structure of enamel, dentin, and predentin

- requires a micro-environment for calcification
-ondontoblasts are columnar, polar cells with tight junctions on the pre-dentin (apex)
- as predentin grows, it grows around the apex forming a thin process of the cell called Tome’s (ondontoblasts) processes, this remains throughout the life of the tooth such that the processes extent the length of the dentin/predentin layer (dentinal tubules)
-ameloblasts are columnar, polar cells with tight junctions on both the predentin side and stellate reticulum side
- these cells secrete matrix proteins and calcium phosphate that becomes mineralized soon after secretion (no pre enamel observed).
-the enamel does not grow around the cells but the cells have a bulb-like process touching the enamel where vesicles contents are released, this structure is called Tome’s process

v) Tooth eruption: the cells of the enamel organ die thus synthesis of the enamel stops, continued growth of the dentin layer results in the tooth penetrating the oral cavity, further growth occurs by continued growth of dentin layer. How does the enamel change shape as the tooth continues to grow?

e) Grinder counts:

i) deciduous (baby) teeth: 10 in maxilla and 10 in mandible

-2 central incisors
-2 lateral incisors
-2 canines
-4 molars

ii) adult teeth: 16 in maxilla and 16 in mandible

-2 central incisors
-2 lateral inscisors
-2 canines
-4 premolars
-6 molars

IV. Organization of digestive tube:

a) 4 basic layers:

i) mucosa:

-epithelia lines lumen: stratified, sq. epithelia, simple col. epithelia, strat. sq. epithelia
- lamina propria: capillaires, lymphatics, lymphocytes, smooth muscle in some regions

- branched and simple tubular glands
- muscularis mucosae (between lamina prop. and submucosa), smooth muscle around the tube

ii) submucosa:

- generally dense irregular CT
- blood and lymph vessels, nerve plexus (ganglia)

- glands in some regions

iii) muscularis (externi):

-circular layer nearest lumen
-longitudinal furthest from lumen
-ganglia between layers

iv) adventicia/serosa:

- loose CT, blood and lymph vessels for adventicia (esophagus, duodenum, ascending and descending colon )
- mesothelium for serosa (other regions)

b) a contiguous tube that connects the oropharynx to the rectum

V. Esophagus:

a) tube connecting oropharynx to stomach

b) epiglottis dictates flow to larynx or esophagus
c ) first digestive structure showing all layers of digestive tube
d ) mucosa: nonkeratinized stratified squamous epith., incomplete muscularis mucosa

i) esophageal cardiac glands:

- near stomach
-branched tubular gland
-secrete slightly alkaline mucus

e) submucosa: loose CT, contains mucous-secreting glands

i) esophageal glands:

-upper half of esophagus
-compound tubuloalverolar glands
-secrete slightly acid mucus

f ) muscularis:

-upper portion is skeletal muscle
-middle is skeletal and smooth
-lower is smooth muscle

g) adventicia instead of serosa over most of the esophagus

VI. Stomach:

a) anatomy: cardia, fundus or body, pylorus
b) functions both as endocrine and exocrine organ
c) continues digestion of CHO, starts digestion of proteins and fats

d) mucosa:

i) surface epithelia invaginates forming gastric pits:
ii) branched tubular glands empty into pits:
iii) lamina propria is scant (most of the cells observed in the mucosa are epithelial cells)
iv) muscularis mucosa is contiguous around the lumen
iii) surface forms protruding folds called rugae: involves both submucosa and mucosa

e) exocrine and endocrine cells of mucosa:

i) surface mucous secreting cells: form pit and secrete thick, visible mucus
ii) mucous neck cells: in the neck of the gland and secrete a thin mucus
iii) parietal (oxytonic) cells:

-found in upper half of glands
-round or pyramidal cell with central nucleus
-intensely eosinophilic cytoplasm
-secrete HCl
-use carbonic anhydrase to produce H+
-active transport of H+ out of cell and Cl- into cell requires ATP
-abundant mitochondria for ATP synthesis (eosinophilia)
-apical membrane surface area increases during secretion by the formation of microvilli within intracellular caniculi
-cells also produce intrinsic factor (glycoprotein) which binds vitamin B12 and is important in B12 adsorption in the ileum

iv) cheif (zymogenic) cells:

-found in basal region of tube of glands
-cuboidal to round cells
-intense basophilic granules in cytoplasm
-granules contain pepsinogen (inactive)
-pepsinogen converted to pepsin (protease) by acid
-cells also secrete lipase

 

v) stem cells:

-found in neck of gland
-divide and differentiate into mucous, parietal, chief or enteroendocrine cells
-turnover time of 3 - 5 days for mucous cells and about 1 year for parietal, cheif, and enteroendocrine cells

vi ) endocrine cells of stomach

-called enteroendocrine cells
- found near base of glands predominantly in pyloric region
- several types that secrete their products into the lamina propria and affect other local (paracrine) cells and distant cells associated with digestion

 

f) submucosa:

i) dense irregular CT, blood and lymph vessels
ii) infiltrated with lymphoid cells, macrophages, mast cells
iii) between muscularis mucosa and muscularis

g) muscularis:

i) approximately 3 smooth muscle layers
ii ) middle layer is greatly thickened at pyloris forming the pyloric sphincter
iii) parasympathetic ganglia between layers

h ) serosa: thin and covered by mesothelium