233 Lecture 2 Flashcards
List the functions of the digestive system
Ingestion, mechanical processing and propulsion, chemical digestion, secretion, absorption, excretion, lining also functions in protection of surrounding tissue.
Identify organs of the digestive tract and the accessory organs
Major organs: oral cavity, pharynx, esophagus, stomach, small intestine, large intestine
Accessory organs: teeth, tongue, salivary glands, liver, gallbladder, pancreas
Identify the type of epithelium for the various regions of the digestive tract
- The mucosa is the inner lining of the digestive tract, is a mucous membrane (epithelium and lamina propria)
- The digestive epithelium is the either simple or stratified, depending on locations and common stresses.
- The lamina propria consists of a layer of areolar tissue that contains blood vessels, sensory nerve endings, lymphatic vessels, smooth muscle cells, and scattered lymphoid tissue.
- The submucosa is a layer of dense irregular CT that surounds the muscularis mucosae.
- The muscular layer (muscularis externa) is a region dominated by smooth muscle cells, found outside the submucosa.
- The serosa is a serous membrane that surrounds most portions of the digestive tract, it is basically the vesceral peritoneum.
Identify the four layers of the digestive tract and other structures associated with them.
- Mucosa
- Submucosa
- Muscular layer
- Serosa
Discuss peristalsis and segmentation, similarities and differences.
- Peristalsis - propulsion. Constricts; the circular layer constricts and longitudinal pushes it forward
- Segmentation - is the squeshing
Describe the anatomy of the oral cavity
Describe the anatomy of a tooth
- Dentin - a mineralized matrix that is similar to that of bone
- Pulp cavity - an interior chamber that receives blood vessels and nerves through the root canal
- Apical foramen - the whole that the blood vessels and nerves enter the root canal.
- Periodontal ligament - fibers that extend from the dentin of the root to the
- Occlusal surface - enaml forms on the occlusal surface of each tooth, which is the biting surface that grinds food against the opposing tooth surface.
- Cementum - the layer that covers the dentin of the root
- Enamel - the layer that covers the dentin of the crown. contains calcium phosphate in a crystalline form. (the hardest biologically manufactured substance).
Know the types of teeth
- Incisor teeth - blade-shaped teeth located at the front of the mouth
- Canine (cuspids) teeth - or cuspids, are conical with a single, pointed cusp.
- Premolar (bicuspids) teeth - or bicuspids, have flattened crowns with two prominent rounded cusps.
- Molar teeth - very large, flattened crowns with four to five prominent rounded cusps adapted for crushing and grinding.
Describe dental succession
Deciduous teeth also called primary teeth, milk teeht, or baby teeth, that are lost. 20 deciduous teeth lost between 7-12 years of age.
Review pharynx structure
A common passageway for food and air, composed of nasopharynx, oropharynx, and laryngopharynx.
Describe the anatomy of the esophagus
- The esophagus is a hollow muscular tube about 25 cm long, and a diameter of 2cm
- Its primary function is to cary food and liquids to the stomach. (the food tube)
- The esophagus enters the abdominopelvic cavity through the esophageal hiatus, an opening in the diaphragm.
- Histology the wall contains mucosal, submucosal, and muscularis layers.
Discuss the phases of swallowing (deglutition)
- Buccal phase - chewing, using tongue to push the bullus to the back of the throat, lifting the soft palate.
- Pharyngeal phase - larynx lifts up and epiglottis closes
- Esophageal phase - peristalsis (autonomic control) takes it down to the stomach
List the major functions of the stomach
- Bulk storage of ingested food
- Mechanical break down of food
- Chemically digest food through action of acid and enzymes
- Intrinsic factor, a glycoprotein that helps absorb vitamin B12 across the intestinal lining.
Describe the anatomy of the stomach
- The cardia
- the fundus
- the body
- the pyloric part (antrum, canal, orifice)
Discuss the gastric gland structure and function
- Gastric glands are dominated by parietal cells and cheif cells. Together they secrete about 1500 mL of gastric juice each day. They secrete intrinsic factor (a glycoprotein that helps absorb vitamin B12 across the intestinal lining.
- Parietal cells indirectly secret hydrochloric acid (HCl).
- Chief cells are most abundant near the base of the gastic gland and secrete pepsinogen (an inactive proenzyme). This is activated the acid of the gastric lumen to pepsin (protein-digesting enzyme)
The process of secretion of hydrochloric acid ions.
- The dissociation of carbonic acid releases bicarbonate and hydrogen ions.
- The bicarbonate ions are exchanged for Cl- from the interstitial fluid.
- When gastric glands are actively secreting, enough bicarbonate ions diffuse into the bloodstream from the interstitial fluidto increase the pH of the blood significantly. (the alkaline tide). the chloride ions diffuse across the parietal cell and into the lumen of the gastric gland.
- The H+ are actively transported there as well.
Discuss the pyloric gland structure and function
- The pyloric part produce primarily mucous secretions, rather than enzymes or acid.
- Cheif cells - secrete pepsinogen
- Parietal cells - Secrete HCl
- Mucous cells - Secrete mucus
- G cells produce gastrin (a hormone) that stimulates the secretion by both parietal and chief cells.
- Contain D cells, which release somatostatin (another hormone).
What are the phases of the regulation of gastric activity.
- Cephalic phase
- Gastric phase
- Intestinal phase
Describe and understand the cephalic phase
- Controled by the CNS with the thoughts of food. The neural output is by way of the parasympathetic division. Vagus nerves (X) innervate the submucosal plexus of the stomach.
- Emotions can exaggerate or inhibit the cephalic phase.
Describe and understand the gastric phase
Begins with the arrival of food in the stomach and builds off of the stimulation of the cephalic phase. The stimuli that initiate the gastric phase are:
1. distension of the stomach
2. an increase in the pH of the gastric contents, and
3. the presence of undigested materials in the stomach (especially proteins and peptides).
Describe and understand the intestinal phase of gastric activity
begins when chyme first enters the small intestine. the funtion of the intestinal phase is to control the rate of gastric emptying to ensure that secretory, digestive and absorptive functions of the small intestine can proceed with reasonable efficiency.
Discuss the digestion and absorption that takes place in the stomach
The stomach secretes HCl (hydrochloric acid) along with pepsin. This breaks down foods into smaller peices and the enzyme pepsin breaks down the proteins into smaller bits of the large polypetptides.
Identify the major parts of the small intestine
Discuss the histology of the small intestine
- Lined with transverse folds called circular folds.
- The intestinal villi is fingerlike projections on each circular fold. The villi are covered by simple columnar epithelium that carpted with microvilli (brush border).
- The villus have a central lymphatic vessel called a lacteal (milky)