Alimentary Canal Flashcards
What is the digestive system?
The organs of nutrient and water absorption; food particle obliteration
What is included in the alimentary canal (GI tract)?
Mouth, pharynx, and esophagus
Stomach, small intestine, and large intestine
What is included in the accessory digestive organs?
Teeth, and tongue
Salivary glands, liver, gallbladder, and pancreas
What is included in the chewing apparatus (bones)?
Mandible: Lower jaw
Maxilla: Upper jaw, and hard palate
The muscles responsible for chewing and moving the mandible + processing for into small, digestible particles are innervated by what?
Mandibular branch of the trigeminal nerve (CN V3)
What is chewing?
Mechanically processing food into smaller and smaller particles. Bolus of food moves around in the mouth in a quasi-circular motion
What are the muscles involved in chewing?
Temporalis Muscle: Elevates and retracts mandible
Masseter Muscle: Elevates mandible; limited protrusion
Lateral Pterygold Muscle: Protracts mandible; produces lateral chewing motions
Medial Pterygoid Muscle: Elevates mandible (works with masseter); provides subtle grinding motions
What does the buccinator do? What is it innervated by?
Compresses the cheeks (important during cheeks)
Innervated by buccal branch of facial nerve, CN VII
What do molars do?
Provide large grinding surfaces for mechanical obliteration of food
What do salivary glands do?
Produce a clear, tasteless, and odorless fluid
What is the parotid?
It is the largest salivary gland that is located roughly in front of the ear
Where is the submandibular gland?
It lies along the body of the mandible
What is the sublingual gland?
It is the smallest salivary gland that sits deep to the tongue
What enzyme starts the digestion of starches from the salivary gland?
Amylase
Where does the tongue lay?
Partly in the oral cavity, and partly in the oropharynx
What are the functions of the tongue?
Important for taste and speech
Aids in chewing and swallowing
What are the muscles that promote tongue movements? What are their functions and innervation?
Genioglossus: Tongue protraction
Hyoglossus: Tongue depression
Styloglossus: Tongue retraction and elevation
All innervated by the Hypoglossal Nerve (motor) CN XII
What three portions is the pharynx divided into?
Nasopharynx: Posterior portion of nasal cavity and has a respiratory function
Oropharynx: Has a digestive function as is bounded by the base of the tongue, soft palate and muscles of the pharyngeal wall
Laryngo-pharynx: Inferior to the pro-pharynx, behind the larynx
Deglutition (swallowing)
Process that transfers the food bolus from the oral cavity through the oro-pharynx, into the pharynx, and eventually through the esophagus into the stomach
The bolus of food moves down the esophagus by what?
Peristaltic contractions
What muscle cause the soft palate to become tense, and open the pharyngotympanic tube during swallowing?
Tensor Veli Palatini
What muscle elevates the soft palate during swallowing?
Levator Veli Palatini
What muscle elevates the posterior part of the tongue?
Palatoglossus
What muscle tenses the soft palate and pulls the walls of the pharynx superiorly, anteriorly, and medially during swallowing?
Palatopharyngeus
Epiglottis
Composed of elastic cartilage and covered by mucous membrane
What is the function of the epiglottis?
Prevents a food bolus from entering the trachea during swallowing
Is the epiglottis open for closed during respiration? When does it close?
Open; it closes during the second and third swallowing phases
What do the superior, middle, and inferior pharyngeal constrictors do?
Constrict walls of the pharynx during swallowing, and propel the bolus of food into the esophagus
What is the motor innervation of the superior, middle, and inferior pharyngeal constrictors?
Vagus (CN X)
What do the Salatopharyngeus, Salpingopharyngeus, and Stylopharyngeus do? What is their innervation?
Elevate the pharynx during swallowing, and move the larynx during speaking; Vagus (CN X)
What muscle of the pharynx is the only one that is innervated by (CN IX)?
Stylopharyngeus
What is the esophagus?
A muscular tube that propels swallowed food to the stomach
What is the esophagus innervated by?
Vagus (CN X)
What are the common areas of constriction?
Arch of aorta, left main bronchus, and the diaphragm
Where does the esophagus terminate?
Esophago-gastric junction
What is the function of the stomach?
Mechanical breakdown of food churned into chyme by peristalsis; chemical breakdown of proteins via acids and enzymes
What enzymes break down proteins in the stomach?
Hydrochloric acid and pepsin
Cardiac region (stomach)
The junction with the esophagus
Fundus (stomach)
The stomach’s dome
Pylorus (stomach)
Termination of the stomach
Rugae (stomach)
Longitudinal folds that allow distention
What is the longest part of the alimentary canal?
Small intestine
Small intestine (3 divisions)
Site of all nutrient absorption
Duodenum
A complex organ that receives digestive enzymes from the pancreas (pancreatic duct), and bile from the liver and gallbladder (bile duct)
5% total length of small intestine, most fixed
Jejunum
Begins at duodenojejunal junction and is 40% of the small intestine’s length
- Thick and heavy
- Long
Ileum
Ends at ileocecal junction and is 55% of the total small intestine length
- Thin and light
- Short
Large intestine
Absorption of water and electrolytes
Teniae Coli
3 thickened bands of longitudinal smooth muscle fibers
Haustra
Pouches of the colon between the teniae
Mental appendices
Small, fatty appendices or projections of visceral peritoneum
Caliber
Much larger internal diameter compared to small intestine
Rectum
Fixed terminal part of large intestine
Anal canal contains what?
- Internal anal sphincter (involuntary)
- External anal sphincter (voluntary
- Anal columns (vessels)
- Pectinate line
What line separates the structures that have different innervations in the anal canal?
Pectinate line, superior are visceral motor and sensory fibers (veins drain into portal venous system); inferior are somatic motor and sensory fibers (veins drain into canal venous system)
What is not received first by the liver?
Lipids
How many lobes does the liver have?
4
- Right
- Left
- Caudate
- Quadrate
What is the “doorway to the liver”
Porta hepatis
Porta Hepatis
Passage of the hepatic portal vein, hepatic artery, hepatic ducts, hepatic nerve plexus, and lymphatics
Falciform ligament
Binds the liver to the anterior abdominal wall
Round ligament
Extends from the umbilicus to the liver, remnant of the umbilical vein (carried oxygenated blood from placenta to fetus)
Ligamentum venosum
Cord-like remnant of the ductus venosus (shunted blood from the umbilical vein to the IVC)
How many internal divisions is the liver divided into?
8
Each liver segment as its own what?
Vascular supply and bile drainage
Liver divisions are supplied by?
- Branch of the right and left hepatic artery
- Hepatic portal vein
- Drained by a branch of the right or left hepatic duct
Gallbladder
Stores and concentrates bile by absorbing water and salts, and expels bile into the duodenum
Pancreas
Elongated accessory digestive gland (C-shaped curvature of the duodenum)
What does the main pancreatic duct do?
Joints the bile duct from the gallbladder and both empty in to duodenum
