What are the digestive systems accessory organs?
- teeth, tongue, salivary glands
- pancreas
- liver, gall bladder
What are the digestive processes in order?
- ingestion: food into oral cavity
- digestion: large molecule are broken down into smaller molecules, 2 types, mechanical (physical breakdown like chewing), and chemical (by enzymes and acid secretions)
- absorption: end products of digestion enter blood or lymph
- defecation: elimination of undigested material
What are the 4 basic layers of the GI tract? (from inside to outside)
- mucosa
- submucosa
- muscularis externa
- serosa
What are the layers of mucosa in the GI tract?
1) epithelium with goblet cells
- stratified squamous: mouth, pharynx, esophagus, anal canal
- simple columnar: stomach, small + large intestine, rectum
2) lamina propria (areolar CT)
- contains blood, lymph vessels, lymph nodules/tissues (immune)
3) muscularis mocosa
- smooth muscle that allows movement of mucosa
Describe the submucosa of the GI tract
- areolar CT
- contains: blood and lymphatic vessels, and submucosal nerve plexus
Describe the muscularis external of the GI tract
- smooth muscle
- inner circular layer
- outer longitudinal layer
- myenteric nerve plexus between layers
- contractions cause motility (mixing and movement)
Describe the serosa of the GI tract
- inner: areolar CT
- outer: epithelium
What is the cavity of the GI tract called
lumen
What are the structures of the digestive system?
oral cavity
salivary glands
dentition
oropharynx, laryngopharynx
esophagus
stomach
small intestine
small intestine accessory organs
large intestine
What does the oral cavity include?
- lips
- cheeks
- palate:
- hard: 2 maxillae + 2 palatine bones
- soft: skeletal muscle, posterior projection = uvula (rises to close nasopharynx when swallowing), soft if posterior to hard
- tongue:
- attached to hyoid bone, made of skeletal muscle, projections of mucosa = papillae (taste buds)
What are the salivary glands?
2 of each:
1) parotid:
- inferior + anterior to ears
- mumps: inflammation of 1 or both
2) submandibular:
- floor of mouth
3) sublingual
- below tongue on floor of mouth
What does saliva consist of?
- 99.5% water
- 0.5% solutes (enzymes)
What are primary dentition?
deciduous (“baby”) teeth (child dentition)
What are secondary dentition?
permanent teeth (adult dentition)
How many of each tooth type are in primary dentition? (in each quadrant)
central incisor: 1
lateral incisor: 1
canine: 1
premolars: 0
molars: 2
20 total in mouth
How many of each tooth type are in secondary dentition? (in each quadrant)
central incisor: 1
lateral incisor: 1
canine: 1
premolars: 2
molars: 3
32 total in mouth
Describe the crown of the tooth
- lies above the gum line
- outer layer: enamel
- acellular; highly calcified making it hard
- dentin = majority of tooth (lies deep to enamel)
Describe the neck of the tooth
- rests between crown and root
- connects the outermost layer of the crown (enamel) from the outermost layer of the root (cementum)
Describe the root of the tooth
dentin + cementum overlay
what is the difference between dentin, enamel, and cementum from bone?
bone is vascular, while dentin, enamel, and cementum is avascular
Describe the oropharynx and laryngopharynx
only muscularis external (skeletal muscle) and stratified squamous epithelium
Describe the esophagus
- passes through diaphragm to the abdominal cavity
- all 4 histo. layers in GI tract from this point on, exceptions in esophagus:
a) muscularis externa
- upper 1/3 = skeletal muscle
- middle 1/3 = skeletal + smooth muscle
- lower 1/3 = smooth muscle
b) has adventitia
- fibrous CT (no epithelium)
What are he 4 regions of the stomach?
- cardiac region (cardia): attached to esophagus
- fundus: above esophageal entrance
- body
- pyloric region (pylorus): has pyloric sphincter
What is different about the epithelial cells of the mucosa of the stomach?
epithelial cells extend down into the lamina propria, where they form columns of secretory cells called gastric glands
