Digestive System Flashcards
Accessory digestive Organs
Other part of the digestive system. Includes things such as; teeth, tongue, gallbladder. Digestive glands; salivary glands, liver and pancreas
Six essential Activities of Digestion process
- Ingestion
- Propulsion
- Mechanical Breakdown (chewing-mouth, churning-stomach, segmentation-small intestine)
- Digestion
- Absorption
- Defecation
Peritalsis
adjacent segments of alimentary tract organs alternately contract and relax, moving food along the tract distally
segmentation
nonadjacent segments of alimentary tract organ alternately contract and relax moving food forward then backward. Food mixing in the small intestine.
Mechanoreceptors and chemoreceptors (within the GI tract)
respond to stretch, changes in osmolarity and pH, and presence of substrate and end products of digestion. Initiate reflexes that activate or inhibit digestive glands. Stimulate smooth muscle to mix.
Short Reflexes
enteric nerve plexuses (gut brain) respond to stimuli in GI tract.
Long Reflex
respond to stimuli inside or outside GI tract (juicy, nice smelling cheeseburger) involve CNS centers and autonomic nerves
Four Basic layers of tunics
- mucosa
- submucosa
- muscularis externa
- serosa=visceral peritoneum
Mucosa
Lines lumen.
Functions (different layer perform 1 or all three);
-secretes mucus, digetive enzymes and hormones
-absorb end products of digestion
-protects against infectious disease
Submucosa
areolar connective tissue. Blood and lymphatic vessels lymphoid follicles, and submucosal nerve plexus.
Muscularis Externa
Responsible for segmentation and peristalsis. Inner circular and outer longitudinal layers.
Sphincters
Circular layer that thickens in some areas
Tongue
made of skeletal muscle.
intrinsic muscles- change shape of tongue
extrinsic muscle-alter tongue’s position
Functions include;
repositioning and mixing food during chewing
Formation of bolus
Initiation of swallowing, speech and taste
Lingual Lipase
Secreted by serous cells
Fat-digesting enzyme
Salivary Glands
Produce saliva.
Parotid gland, submandibular gland, and sublingual gland
composition of saliva
97-99.5% water, slightly acidic.
Make 1500 ml/day
Stomach
Upper left quadrant of torso. It is where the bolus( food) is turned into CHYME. Autonomic Nerve Supply
Mucosa
Covered with gastric Pits. made up of simple columnar epithelium composed of mucous cells. Gastric glands produce the gastric juices.
Parietal cell secretions
Hydrochloric acid (HCL). pH 1.5-3.5denature protein, activates pepsin, breaks down plant cell walls, kills many bacteria. glycoprotien required for absorption of vitamin B12 (important for RBC production) in small intestine.
Chief Cell Secretions
Pepsinogen- inactive enzyme.
Activated to pepsin by HCL and by pepsin itself (a positive feedback mechanism). Lipase’s (digest~15% of lipids)
Enteroendocrine Cells
Secretes chemical messengers into lamina propria. Act as paracrine (respond to serotonin and histamine).
Mucosal Barrier
Thick layer of bicarbonate-rich mucus
Tight junctions between epithelial cells
Alimentary Canal
the digestive system. Mouth to anus. Digest food and absorbs fragments. Mouth, pharynx, esophagus, stomach, small intestine and large intestine.
a patient with a low RBC count recieves vitamin B12 injection every 2 weeks. Why?
Parietal cells in the patients stomach have ceased producing intrinsic factor.
Cephalic Phase (phases of gastric secretion)
conditioned reflex triggered by aroma, taste, sight and thought
Gastric Phase (phase of gastric secretion)
2/3 gastric juice released. Simulated by distention, peptide, low acidity, and gastrin (major stimulus).
Gastrin-> enzyme and HCL release
Intestinal Phase (phases of gastric secretion)
Stimulatory component. Partially digested food enters small intestine -> brief intestinal gastrin release.
Which of the following phases of gastric secretion is a conditioned reflex?
Cephalic Phase (when you see food, or smell something good, that is a conditioned reflex)
Bicarbonate
Most important buffer in the blood. Helps the blood from becoming too acidic
