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Natural Science
NATS 1675
Robert Crippen

Midterm 2 ~ one hour and a half. 31 multiple choice question, matching and true and false. There are figures which answer the multiple choice format. There are two line pages to do your problem. Required readings section 8.6, pp 183-189 - nutrition and weight control. Do not be concerned with specific BMI number, percentages in Fig 8.14, specific information in tables 8.5, 8.7 and 8.8. CHAPTER 8 - DIGESTIVE SYSTEM  Digestive track that (tube) and associated organs (salivary glands, liver and pancreas)  Mammal’s digestive track is complete, start with the mouth and end with the anus.  Some organism only have one opening - jelly fish, fish,  Cavity of tract called the lumen  Wall of tract made of 4 layers 1. Mucosa - inner layer (which contain mucus) Mucus membrane, some areas of the mucosa contain specialize cells and other areas received digestive enzymes from other glands, i.e., single cells embedded en humocosas and/ or pancreas secretes mucous from a duct into the lumen 2. Submucosa - this contain blood vessel, lymphateic vessels and nerves. 3. Muscularis - is made of inner layer of circular muscles and outer layer of longitudinal muscle (run length of the tract). Outer layer is responsible of the peristalsis wave- like movement of the digestive tract. Allow movement of food or nutrients - combination of these muscles contracting to produce wave-like movement of the digestive tract. i. Responsible for peristaisis 4. Serosa - The outer covering is thin. Protecting layer. Mouth  Beginning of the digestive tract  Initial processing of food ~ Mechanical (chewing food down into smaller particles) and chemical digestion in the mouth, sugar digestion start here. Start breaking down complex sugar to simple sugars.  Children have 20 milk or dicedeous teeth  Adults have 32 teeth  Canines = cuspids  Incissors (8 in total) are for bitting and cutting  Bicuspids or premolars - 4 each jaw = 8 total, this are for grinding  Molars= 6 in each jaw, 12 total also for grinding   Read page 69, starting at point 4.3 and 70 Muscle Types 1. Skeletal or Voluntary ~ these are the muscles you want to show up. Muscles that are move by individual's will. 2. Cardiac Muscle ~ found in the heart (aorta) also striated but, involuntary, i.e. you do not have control over it. 3. Smooth Muscle ~ Cells are pointed at either ends; they are involuntary, and are not striated. Are single nucleous. Tongue  Contain skeletal muscle  Voluntary control  Upper surface covered with papillae. Functions of the papillae  Sensitive to touch  Adds roughness  Some of the papillae contain taste buds: salt, sweetness, bitterness & sour. The tongue is not only aids in chewing, but it also initiate aids in swalling by directing the food (= Bolus) to the back of the mouth and directs it into the pharynx (throat). At you are chewing your food, saliva is being added to it, also contain mucus which allow the food to slide down the digestive tract and the esophagus Absertion ~ this is not a primary function of the mouth; however, some absertion can occurs in the thin membrane beneath the tongue or in the throat.  Nitroglycerine ~ alleviates angina, alcohol by simple diffusion.  Salivary Glands ~ 6 glands/ 3 pairs, which empty the substances in the mouth  Basically, there are two types of solution: 1) serous - watery 2) mucus (thicker), together there are 6 salivary glands produce about one litre of saliva per day.  Salivary glands and saliva function in taste and digestion, swallowing, lubrication, cleansing and protection. Saliva Function 1. Taste ~ taste buds are only stimulated by substances in solution. Salt cannot be tastes in a dry tongue. Solution is made from a solvent and a solute. - Sugar in coffee. Sugar = solute (being dissolve), and coffee = solvent (does the dissolving). 2. Disgestion ~ produces salivary amylase or ptyalin; these begin to break down in starch and double sugars to simple sugars. [Fructose (simple sugar) and sucrose (table sugar is a double sugar)]. 3. Swallowing ~ one of the subtance produced by the salivary glands is called the mucin. Mucin is mucus like subtance, and it causes food particles to stick together. It acts as a lubricant. 4. Lubrication ~ A) It helps you to swallow. B) Mucin also prevents the mucous membranes from drying out. It aids in speaking (If you have a dry mouth, your lips and tongue would losse mobility, so this result in not speaking) 5. Cleansing ~ the longer the fermentable carbohydrates stay in the mouth, reside in the mouth the greater the chances of tooth decay. Fermentable carbohydrates or oral Bacteria produce organic acids which eat away our teeth. 6. Protection ~ A) There are substances in saliva that gived it a buffering capacity that neutralizes both acids and bases. (HCl + NaOH, the OH is the base --> HOH or H2O + NaCl). B) Saliva has a bactericidal effect on many organisms. Everytime you see a word finishing with cidal- mean can kill anyone. C) Nausea can triger salivation Pharynx ~ basically this is your throat; this is the region that connects both the mouth and nasal passsage. Swallowing ~ it is called voluntary and involuntary action, also chewing. Voluntary part refers to the facts that tonge forces the food into the pharynx. Both voluntary and involuntary automatic several things may happen 1. The soft palate elevates and closes the nasal passage 2. The epiglotti covers the glottis (open the larynx {voice box}) 3. Pharyngoesophaged sphincter relaxes and peristalsis propels the food down the esophagus. Sphincter = these are circular or doughnut shape muscles they function to close an opening of a lumen or tubular structure. We have sphincter all along the digestive tract, these are like belts that close or allow things to go in. Pharyngoesophaged = located between the pharynx and the esophagus, so then you are swallowing you have to relax so food get into the digestive tract. Peristalsis ~ It’s like a wave-like action that propels the food bolus or other materials down the digestive tract. It results from co-ordinated action of the circular and longitudinal muscles in the digestive tract. Esophagus ~  Food tube and soft structure  Muscular structure, soft that lies behind the trachea.  It about 25 cm long and it takes about 10 seconds to move down the esophagus.  It have no digestive function, it’s just a conductive organ.  At the button of the esophagus, there is another sphincter --> gastroesphageal sphincter located in the stomach and the esophagus.  Prevents he regurgitation of the acid contents of the stomach into the esophagus.  Histologically ~ not a true sphircter. Gastroesophageul sphincter  Stomach is a thick walled, J-shaped organ that functions for storage, mixing, digestion and emptying. The stomach is divided into four regions: cardiac region, fundus (above the cardiac region), body and pylorus.  The stomach is lined with mucosa made up of deep folds called RUGAE and millions of gastric pits. If your stomach fills, the rugae disappear. Storage is 1 litre, after a meal, it would take 4 to 6 hours to be empty. The stomach under dose gentle contraction, this mixes the food with gastric secretion. Protein digestion starts in the stomach.  At the pyloric sphincter the mixture of food and digestive fluids are called chyme. Chymes are the mixture of pepsin, hydrochloric acid and food.  Specialized cells lining the gastric glands produce pepsinogen (pepsin), hydrochloric acid and mucus that make up gastric juice.  Gastric pit contains specialize cells to produce digestive enzymes.  The pepsin works best at a pH of 2. ph scale goes from 0 to 14. 7 is neutral, such as water. The lower the pH the higher the acidity <7, Base on alkaline is >7. The acidity from 6 to 7 is 10x, from 5 to 7 = 100x and 4 to 7 = 1000x. pH stands from the power of Hydrogen ions.  HCL acid breaks down connective tissues, i.e. cartilage. It also kills the bacteria. Absorption is not a primary function of the stomach, but there some substances that can be absorb by it, such as:  1. alcohol  2. aspirin  3. Some lipid soluble drugs. Small Intestine ~ The small intestine is 3 m (10 ft.) in life; 6 m (20ft.) in death - this is due to relaxation of the longitudinal muscles. For comparison, the large intestine is 1.5 m long. There are number of mucus cells along the small intestine, for protection and lubrication of food. There are 2 primary functions: 1. digestion 2. absorption It exhibits three functional modifications compared to the rest of the digestive tract that aid in absorption: 1) plicae circulare - circular or transverse folds in the mucosa that increase the surface area 3 times; 2) villi - finger like projections that increase the surface area about 10 times; and 3) microvilli or brush border - each villus is covered with a layer of epithelial cells and each epithelial cell has about 600 microvilli that increase the surface area another 20 times. The total absorptive area of the small intestine is 250 m2. The small intestine is composed of three regions: (Fig. 5. 8) 1. duodenum: distinguished both structurally and histologically. The small region of the intestine 2. jejunum: it receives digestive secretion from pancreas and liver. Pancreas produ
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