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)
Discuss the structure and function of intestinal glands and their secretions
- The duodenum has numerous goblet cells, both in the epithelium and deep to it
Describe intestinal movements of the small intestine
- Contractions are myenteric reflexes that are not under CNS control. Motor neurons in the submucosal and myenteric plexuses control these short reflexes. Smooth muscles cells contract periodically even without stimulation.
- Stimulation of the parasympathetic system increases the sensitivity of the weak myenteric reflexes and speeds up local peristalsis and segmentation.
- Gastroenteric and gastroileal reflexes speed up moement.
Describe the anatomy of the pancreas
- It has a head, body, and tail. Looks lumpy with a thin transparent capsule of connective tissue.
- There is a large pancreatic duct that delivers the secreation of the pancreas to the duodenum, where it meets the bile duct from the liver and gallbladder, then empties into the duodenal ampulla (a chamber located about halfway along the length of the duodenum)
Identify the exocrine and endocrine structures within the pancreas
Identify the four main classes of pancreatic enzymes and their functions
- Pancreatic amylase - breaks startchs and disaccharides into oligosaccharides and disaccharides
- Pancreatic enzymes (trypsin, chymotrypsin, and carboxypeptidase) - breaks large polypeptides into small polypeptides and small peptides
- Pancreatic lipases - breaks fats into monoglycerides and fatty acids
- Pancreatic ribonuclease and deoxyribonuclease - breaks nucleic acids into nucleotides.
Describe the anatomy of the liver
Describe the anatomy of the bile duct system, including the hepatopancreatic ampulla and sphincter.
Describe the functions of the liver in regards to metabolic regulation, hematological regulation, and the production of bile.
- Metabolic regulation -the liver is the primary organ involved in regulating the composition of circulating blood
* Carbohydrate metabolism
* lipid metabolism
* amino acid metabolism
* removal of waste products
* vitamin storage
* mineral storage
* drug inactivation - Hematological regulation - the liver is the largest blood reservoir in the body. As blood passes through it, it preforms these functions:
* phagocytosis and antigen presentation
* synthesis of plasma proteins
* removal of circulating hormones
* removal of antibodies
* removal/storage of toxins - Production of bile - synthesis and secretion; the liver sythesizes bile and secretes it into the lumen of the duodenum. Bile is water, minor amounts of ions, bilirubin, cholestrol, and bile salts (an assortment of lipids)
* function of bile - is to emulsify the lipid droplets into the chyme.
Describe the anatomy and physiology of the gallbladder
A hollow organ that stores concentrated bile prior to excretion into the small intestine
* hepatopancreatic sphincter - is where the bile duct and pancreatic duct drains into the duodenum
* gall bladder has two functions:
1. stores bile
2. concentrates bile
Identify and discuss the intestinal hormones (stimulus for secretion, location of secretion, target organs/tissues, and effects)
Describe the anatomy of the large intestine
- Cecum - expanded pouch at the beginning of the large intestine
1. Ileocecal valve
2. the cecum collects and stores materials from the ileum and begins the process of compaction
3. appendix - slender hollow organ attached to the posteromedial surface of the cecum. - Colon - has a larger diameter and thinner wall than the small intestine. Features:
1. Wall forms haustra) pouches, allows for expansion
2. taeniae coli - three separate longitudinal bands of smooth muscles
3. omental appendices - numerous teardorp-shaped sacs of fat
4. the colon can be subdivided into four regions: ascending, transverse, descending, and sigmoid colon - Rectum - forms the last 15 cm of the digestive tract
1. expandable for the temporary storage of fecal material
2. the movement of fecal materials into the rectum triggers the urge to defecate
3. anal canal - the distal portion of these coumns is where the columnar epithelium changes to keratinized stratified squamous epithlium
4. anus: internal and external sphincter. - Lacks villi, but has an abundance of goblet cells and distinctive intestinal glands.
1. the intestinal glands are dominated by goblet cells (produces mucus): lubrication for poop
2. mucus is secreted in response to friction or exposure to harsh chemicals
Describe and understand the physiology of the large intestine (absorption, vitamins, organic wastes, movements, defecation reflex)
Physiology of the large intestine - do digestive enzymes are released by cells.
* Less than 10% of nutrient absorption takes place in the colon
* reabsorption of water is the primary funciton of the large intestine
* the large intestine also reabsorbs bile salts, vitamins, and organic waste products.
* bacteria in the large intestine generate 3 vitamins, and organic waste products
* bacteria in the large intestine generate three vitamins that supplement our dietary supply
1. Vitamin K -
2. Biotin -
3. Vitamin B5 -
* Organic wastes absorbed by the large intestine: Bilirubin, peptides (bacteria breaks down to ammonia, indole and skatole, and hydrogen sulfide), and ammonia
* Movements - gastroileal and gastroenteric reflexes move materials into the cecum
1. movement from the cecum to the transverse colon is slow, allowing for water reabsorption
2. peristaltic waves move along the length of the colon, and haustral churning mix the contents of adjacent haustra
3. mass movements occur a few times a day, a powerful perstaltic contractions that move material from the transverse colon through the rest of the large intestine
4. defecation reflex - distention of the rectal wall triggers this, and involes 2 positive feedback loops (short reflex and long reflex)
Describe and understand the digestion and absorption of carbohydrates, lipids, and proteins.
- The large molecules have to be broken down to be able to be absorbed
- Smaller products will either be used to provide energy or used to synthesized carbohydrates, proteins, and lipids
- Digestive enzymes break down the bonds between these large macromolecules using a process called hydrolysis (adding a water to a molecule to break it into smaller parts). They come from saliva, tonue, stomach, pancrease, and brush borders.
- Carbohydrate digestion and absorption:
1. Salivary and pancreatic enzymes - break complex carbohydrates into disaccharides and trisaccharides (salivary amylase and pancreatic alpha-amylase)
2. brush border enzymes - on the microvilli to break disaccharides and trisaccharides.
3. intestinal epithelium absorbs monosaccharides by facilitated diffusion and cotransport. - Lipid digestion and absorption - involves lingual lipase and pancreatic lipase
1. the most abundant and important of dietary lipids are triglycerides
2. lipases break the triglycerides into monoglycerides
3. bile salts emulsifythese lipid droplets, producing micelles, a much smaller lipid droplet - Protein digestion and absorption - proteins are large and cocmplex, so their digestion is complex and time consuming
1. mastication and the highly acidic environment of the stomach provide breakdown of food into smaller pieces so pepsin can reach individual proteins
2. Once small, pancreatic proteases can begin.
3. epithelial cells of small intestine can dipeptidases that break short peptides into individual amino acids.
Discuss the absorption of water, ions, and vitamins.
- Water abosorption - water cannot be absorbed or secreted, it moves by osmosis
1. water movees to where there is higher concentration of solutes - Ion absorption - many regulatory mechanisms controlling the rate of ion absorption are poorly understood
1. Na+ may enter intestinal cells via diffusion, contransport, or active transport. High salt in food increase Na+ uptake, leading to water following
2. Ca2+ absorption involves active transport at the epithelial surface
3. K+ passively diffuses following the concentration gradient
4. Mg2+ and Fe2+ use specific transport proteins, and are moved using active transport
5. Cl-,I-,HCO3-, and No3- are absorbed by diffusion or carrier-mediated transport
6. PO43- and SO42- enter epithelial cells only be active transport - Vitamins -
1. include fat soluble - (A,D, E, K) can dissolve into lipids, absorbed with micelles
2. water soluble vitamins (B vitamins, C), there are 9 altogether, all but one (B12) can be easily absorbed by diffusion across the epithelial membrane.
Describe the location and structural features (external and internal anatomy) of the kidney
Follow the blood flow into and out of the kidney
Know the basic innervation of the kidneys
- Kidneys and ureters are innervated by renal nerves
- Most of the nerve fibers are sympathetic postganglionic fibers.
Identify and describe the structures and locations of nephrons
Renal corpuscles
