42 Questions
What is the main function of the oral cavity?
Mechanical and chemical digestion
Which process involves breaking down ingested materials into smaller pieces?
Mastication
What type of epithelium lines the oral cavity?
Nonkeratinized stratified squamous epithelium
Which structure separates the space between the cheek or lips and gum?
Oral vestibule
What are the main components of saliva in the oral cavity?
Amylase, lipase, and protease
What is the function of buccinator muscles in the oral cavity?
Holding food against the teeth during chewing
Which part of the oral cavity is covered externally by skin?
Lips or labia
What is the primary role of the hard palate in the oral cavity?
Aiding in mechanical digestion
What is the function of the myenteric nerve plexus?
Mainly control GI tract motility
Which layer of the gastrointestinal (GI) tract consists of smooth muscle with circular and longitudinal fibers?
Muscularis externa
What is the composition of the serosa layer of the GI tract?
Simple squamous epithelium and connective tissue
Which nerve plexus is responsible for regulating movements of the mucosa and vasoconstriction of blood vessels?
Submucosal nerve plexus
What is the primary function of the esophagus?
Transport food into the stomach
Where is the superior esophageal sphincter located?
At the junction of the esophagus and pharynx
Which layer of the GI tract provides protection and support to the organs?
Adventitia
What is lubricated by mucus secreted by esophageal glands?
Bolus
What is the function of the lingual frenulum?
Connects the tongue to the floor of the mouth
Which salivary gland is located beneath the tongue?
Sublingual gland
What is the primary ingredient of saliva?
Water
Where are the transverse palatine folds located and what is their function?
In the oral cavity, manipulate ingested materials before swallowing
Which structure prevents ingested material from entering the nasal region?
Uvula
What is the function of superior labial frenulum?
Attaches internal surfaces of superior lips to gingivae
What is the role of intrinsic muscles of the tongue?
Move the tongue within the oral cavity
What is one of the functions of saliva?
Dissolve food for taste receptors stimulation
Which enzyme in the stomach is responsible for digesting proteins?
Pepsin
What is the main function of the lower esophageal sphincter (LES)?
Preventing stomach acid from flowing back into the esophagus
Which part of the stomach serves as a reservoir for food before releasing it into the small intestine?
Fundus
What is the primary role of intrinsic factors secreted by the stomach?
Facilitate Vitamin B12 absorption in the ileum
Apart from HCl and pepsin, what else is commonly found in gastric juice?
Gastrin
Which enzyme is responsible for digesting triglycerides in the stomach?
Gastric lipase
What is the shape of the stomach that aids in its function as a holding reservoir and mixing area?
'J'-shaped
Which region of the stomach serves as the entryway into the stomach lumen from the esophagus?
Cardia
What is the main function of the pyloric part of the stomach?
Food mixing
Which type of cells secrete mucin to prevent ulceration of the stomach lining?
Surface mucous cells
What is the function of neck mucous cells in the stomach?
Produce acidic mucin
Which cells in the stomach assist in B12 absorption?
Parietal cells
What is the role of the pyloric sphincter in the digestive system?
Regulate the entry of chyme into the small intestine
In what way does HCl acid secreted by parietal cells aid in digestion?
Denatures proteins
What is the main function of chief cells in the stomach?
Synthesize pepsinogen
Which part of the stomach is lined by simple columnar epithelium?
Body of the stomach
What is the function of enteroendocrine cells in the stomach?
Prevent ulceration of lining
Which part of the stomach allows it to expand greatly when filled and return to its normal shape when empty?
Rugae
Study Notes
Layers of the GI Tract
- The GI tract consists of four layers: mucosa, submucosa, muscularis, and adventitia/serosa
- Mucosa: lining of the GI tract, contains epithelium, lamina propria, and muscularis mucosae
- Submucosa: contains blood vessels, lymphatic vessels, and nerves
- Muscularis: consists of two types of smooth muscle: inner circular and outer longitudinal fibers
- Adventitia/Serosa: outermost layer, provides protection and support, composed of areolar connective tissue, elastic and collagen fibers, and simple squamous epithelium (mesothelium)
Functions of the Esophagus
- The esophagus is a 25 cm long, muscular tube that lies posterior to the trachea
- It extends from the pharynx to the stomach
- Purpose: secretes mucus and transports food into the stomach
- Superior esophageal sphincter (UES) and esophageal hiatus connect the esophagus to the stomach
- Peristalsis: forces materials to move further along the tract
Functions of the Digestive System
- 7 functions: secretion, digestion, absorption, circulation, elimination of wastes, peristalsis, and regulation
- Secretion: acids, bile, mucus, and digestive enzymes (7 L/day)
- Digestion: mechanical and chemical breakdown of food into smaller molecules
- Absorption: nutrients, ions, and fluids into the bloodstream
- Elimination of wastes: removal of metabolic wastes
Oral Cavity
- Initial site of mechanical and chemical digestion
- Formed by lips, cheeks, hard and soft palates, and tongue
- Covered externally by skin and internally by a mucous membrane
- Buccinator muscles and connective tissue lie between the skin and mucous membranes of the cheeks
Structures of the Mouth
- Vestibule: space between the cheeks (lips) and the gums
- Oral cavity proper: lies between the mandible and maxillae
- Uvula: together with the soft palate, they prevent ingested material from entering the nasal region
- Fauces: opening between the oral cavity and the oropharynx
- Transverse palatine folds: assist the tongue in manipulating ingested materials prior to swallowing
- Superior labial frenulum: attaches the internal surfaces of the superior lips to the gingivae
Tongue
- Accessory digestive organ composed of skeletal muscle covered with mucous membrane (stratified squamous epithelium)
- Functions: manipulation of food, mixing with saliva, converting food into a bolus, and assisting in swallowing
- Extrinsic and intrinsic skeletal muscles move the tongue
Salivary Glands
- Produce and secrete saliva into the oral cavity (1.0-1.5 liters/day)
- Functions: moistens ingested materials, cleanses and lubricates the oral cavity, begins chemical digestion of carbohydrates with amylase, and has antibacterial action with lysozyme
Stomach
- J-shaped, muscular sac that lies inferior to the diaphragm and occupies the left upper quadrant of the abdomen
- Connects the esophagus to the duodenum
- Functions: mechanical and chemical digestion of the bolus, converts semisolid bolus to a liquid (chyme), and absorbs certain substances
- Four main regions: cardia, fundus, body, and pyloric part
- Pyloric part consists of two regions: pyloric antrum and pyloric canal
- Rugae: mucosal folds that allow the stomach to expand greatly when it fills and then return to its normal J shape when it empties
Test your knowledge on the functions of the human digestive system, including secretion, digestion, absorption, and elimination of wastes. Learn about processes like peristalsis and mechanical digestion.
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