Digestive System: Anatomy and Physiology PDF

Fiber- Indigestible plant material. Bolus- Mass of masticated (broken down) food ready to be swallowed. Exocrine (secrete outside, outward)- A gland that secretes its products through excretory ducts to the surface of an organ or tissue, or into a vessel.  Sphincter - Circular band of muscle fibe...

Fiber- Indigestible plant material. Bolus- Mass of masticated (broken down) food ready to be swallowed. Exocrine (secrete outside, outward)- A gland that secretes its products through excretory ducts to the surface of an organ or tissue, or into a vessel.  Sphincter - Circular band of muscle fibers that constricts a passage or closes a natural opening of the body. An example of a sphincter is the lower esophageal (cardiac) sphincter that constricts once food has passed into the stomach. 4\. Mastication- Breaking down of food 5\. Peristalsis- A wave of coordinated muscle contraction that move along the         length of the esophagus. 6\. Esophagus- A muscular tube about 10 inches long that goes through the  diaphragm and ends at the stomach. Its main purpose is to propel what you  swallow toward your stomach using peristalsis.  7\. Chyme- Food mixed with digestive enzymes. The main role of your digestive system is to extract nutrients from the food you eat so they can be distributed to the body's cells and used for energy and growth. That's one reason why what you eat can really make a difference to how well your body functions. The digestive system, also call the gastrointestinal (GI) system, consists of a digestive tube called the GI tract or alimentary canal, and several accessory organs whose primary function is to break down food, prepare it for absorption, and eliminate waste. The GI tract, extending from the mouth to the anus, varies in size and structure in several distinct regions: Mouth Pharynx (throat) Esophagus Stomach Small intestine Large intestine Rectum Anus Food passing along the GI tract is mixed with digestive enzymes and broken down into nutrient molecules, which are absorbed in the bloodstream. Undigested waste materials not absorbed by the blood are then eliminated from the body through defecation. Three organs, the liver, gallbladder and the pancreas, provide important substances that contribute to our digestion. These organs also contribute to many other body functions. Therefore, they're considered accessory organs to the digestive system.  Before you've even taken a bite, your salivary glands have begun to release saliva. Once you take that bite, you're setting the whole process of digestion in motion. You ingest food with your mouth, your teeth chomp it into smaller bites that you can swallow, and your tongue mixes it with saliva. (Your saliva contains some important digestive enzymes, and as soon as you begin to eat, it starts breaking down starches).  Once you've chewed a bite of food, the bolus is ready to be swallowed. When swallowed, it goes through your pharynx , down your esophagus, and on its way to your stomach.  The pharynx also leads to your lungs, so when you swallow, the epiglottis closes over your larynx so that food, water, or even saliva doesn't go into your lungs. Occasionally, if you eat or drink too fast or are distracted, what's going down your throat will move faster than your epiglottis, and you'll get something "down the wrong pipe."  While most of the organs in the GI tract have a special arrangement of muscles that produce peristalsis, the stomach has an additional layer that allows it to really mash food around and may even break it into smaller pieces.  When your stomach starts to fill up, stretch receptors in the stomach walls send the message that it's time to start the action.  Your stomach doesn't have to be full, sometimes just the sight or smell of something delicious can get your stomach going.  If you're hungry, your stomach might start up on its own, sending the message that it's waiting for some food to arrive.  From the stomach, chyme is pushed into the small intestine The small intestine averages 15-20 feet long and has three sections: Duodenum Section Average length 2 feet Duodenum- (do-AH-de-num) Jejunum (je-300-num) 6 feet Ileum 10 feet Ileum- (IL-ee-um) Jejunum- ★ All of this muscle is wound up in a precise way and takes up a big chunk of the space in your abdomen. As digestion takes place, small amounts of chyme are pushed slowly along the length of the small intestine. When you have a \"stomach ache,\" it\'s often in your intestines, caused by gas that\'s trapped and needs to make it around one of the corners of the folds. The gas is produced by the millions of bacteria that live in your small and large intestine. They eat some of what\'s in your food and even help you digest it. ★The small intestine is always slightly contracted and is usually busy doing something. In a living adult, it can be anywhere between 10 and 30 feet long. Once a person dies, his or her small intestine no longer stays contracted, and it can be 5 to 10 ft longer. As chyme makes its way through the small intestine, most of its nutrients are absorbed.  When it reaches the end, peristalsis pushes the material that's left into the large intestine (colon).  Once material enters the large intestine, it's called feces. The large intestine is much wider and shorter than the small intestine, and it makes a ring around the outside of the small intestine.  The main role of the large intestine is to absorb water that's left in the feces and pass it into the rectum, along with undigested food, unabsorbed bile, and bacteria.  The appendix is a worm-shaped extension hanging off an area near the start of the large intestine.  For many years, doctors have presumed that the appendix has no function, but now that researchers are becoming more aware of the number and role of bacteria in the intestines, some are looking into whether the appendix has a hand in maintaining or stabilizing the bacterial populations in the gut. Several times a day, the colon goes through long, slow peristaltic contractions that push the feces from the intestine into the rectum.  Fiber can make these contractions stronger and can soften feces, making it easier to move along.  As the feces reaches the end of the rectum and the beginning of the anus, it sets off a reflex. This reflex sends a signal to the brain that there is feces ready to make an exit. The brain then makes a decision about whether the moment is right or not. If the decision is to hold off, the rectum will stop sending the signal for a bit. If the colon goes through peristaltic contractions again, that will set off the defecation reflex once more.  The anus has two sphincters, or rings of muscle, that contract or expand to be closed or open. The inner sphincter is made of involuntary muscle, and the defecation reflex signal from the rectum causes this sphincter to relax. The outer sphincter is made of voluntary muscle. Under ordinary circumstances, the brain makes the decision whether to open this sphincter, and when it does, peristalsis in the muscles of the rectum push the feces through the anus and out of the body.    Although the liver, gallbladder, and pancreas lie outside the GI tract, they play a vital role in the proper digestion and absorption of nutrients. The liver, the largest glandular organ in the body, it weighs approximately 3-4 lbs. Its located beneath the diaphragm in the right upper quadrant (RUQ) of the abdominal cavity. The liver performs many vital functions and death occurs if it ceases to function. The liver is the second largest organ in the body (the skin being the largest), and is something of a jack-of-all-trades.  Its digestive function is only one of many vital things it does for the body.  It is also a filter; it removes toxins left behind by drugs or substances such as alcohol, and recycles the iron from old red blood cells.  It stores glucose that the body calls on when blood sugar is low, and it is also a parking place for many vitamins and minerals. It secretes proteins that circulate in the blood plasma, such as complement and clotting proteins, as well as multiple hormones.  It's the only internal organ capable of regenerating if a large portion of it has been damaged (the skin easily regenerates if its wounds are small).  A person can regenerate an entire liver if he or she has up to 25% of a healthy liver left. (That means a living person can donate part of his or her liver to another person for a transplant). On average, the donor's liver will have regenerated within six weeks.  The liver produces a yellowish green substance called bile, which contains bile salts.  Bile salts break down large globules made of many fat molecules stuck together into smaller pieces.  Once the liver has made bile, it sends the bile to the gallbladder, where it's stored until it is needed.  When the gallbladder gets the signal, it uses peristalsis to empty bile into the duodenum through a small duct.  Because the gallbladder does not make bile, its removal generally has limited impact on digestion. The person still makes bile---it just gets delivered directly to the small intestine.  Bile has a foul taste and the word bilious describes a person who has a foul or unpleasant disposition. The gallbladder, a saclike structure on the inferior surface of the liver, serves as a storage area for bile, which is produced by the liver. When bile is needed for digestion, the gallbladder releases it into the duodenum through the (common bile duct). Bile is also drained from the liver through the (right hepatic duct and the left hepatic duct). Bile production is stimulated by hormone secretions, which are produced in the duodenum, as soon as food enters the small intestine. Without bile, fat digestion is not possible The pancreas is an elongated, somewhat flattened organ that lies posterior and slightly inferior to the stomach.  You already know that the pancreas plays an important role in the body's ability to bring sugar into cells. It is also very important in the digestion of our food.  Tucked into a curve of the duodenum and beneath the stomach, it produces a fluid called pancreatic juice, which contains a variety of enzymes.  Individual enzymes digest specific types of molecules. Together, this group of enzymes is able to do some digestion on every category of food molecule.   When the pancreatic juice leaves the pancreas, it flows into a duct (pancreatic duct)that meets up with the duct from the gallbladder(cystic duct). The two ducts fuse to become one duct(common bile duct) that empties the fluids from both organs into the duodenum.  Abbreviation Meaning BM: Bowel Movement CT: Computed Tomography GERD: Gastroesophageal Reflux Disease GI: Gastrointestinal HAV: Hepatitis A Virus HBV: Hepatitis B Virus HCV: Hepatitis C Virus Abbreviation Meaning HDV: Hepatitis D Virus HEV: Hepatitis E Virus IBS: Irritable Bowel Syndrome NG: Nasogastric PE: Physical Examination; Pulmonary Embolism BMI: body mass index Stat, stat: immediately PMH: past medical history PUD: peptic ulcer disease R/O: rule out A.c.: before meal H.s.: At bedtime Abbreviation Meaning B.i.d: twice a day NPO, n.p.o: nothing by mouth P.c.: after meals P.o.: by mouth P.r.n: As needed, as required Abbreviation Meaning qAM: every morning Q.d.: every day q.h. : every hour Q.2.h: every two hours Q.i.d: four times a day Q.o.d: every other day qPM: every evening T.i.d: three times a day Blood, Lymph, and Immune The main function of the digestive system is to provide vital nutrients for growth, maintenance, and repair of all organs and body cells. ★ Liver regulates blood glucose levels. ★ Digestive tract secretes acids and enzymes to provide a hostile environment for pathogens. ★ Intestinal walls contain lymphoid nodules that help prevent invasion of pathogens. Digestive system absorbs vitamin K for blood clotting Integumentary ★ Digestive system supplies fats that provide insulation in the dermis and tissue. ★ Digestive system absorbs nutrients for maintenance, growth and repair of the skin. Cardiovascular ★ Digestive system absorbs nutrients needed by the heart. Musculoskeletal ★ Digestive system provides nutrients needed for energy fuel. ★ Digestive system absorbs calcium needed for bone salts and muscle contraction. ★ Liver removes lactic acid (resulting from muscle activity) Endocrine ★ Liver eliminates hormones from the blood to end their activity. ★ Pancreas contains hormone-producing cells. Nervous ★ Digestive system supplies nutrients for normal neural functioning, ★ Digestive system provides nutrients for synthesis of neurotransmitters and electrolytes for transmission of a nervous impulse. ★ Liver plays a role in maintaining glucose levels for neural function. Female reproductive ★ Digestive system provides adequate nutrition, including fats, to make conception and normal fetal development possible. ★ Digestive system provides nutrients for repair of endometrium following menstruation Genitourinary ★ Digestive system provides adequate nutrients in the development of viable sperm. ★ Liver metabolizes hormones, toxins, and drugs to forms that can be excreted in urine. Respiratory ★ Digestive system absorbs nutrients needed by cells in the lungs and other tissues in the respiratory tract. ★The pharynx is shared by the digestive and respiratory systems. The lowest portion of the pharynx divides into two tubes: one that leads to the lungs, called the trachea, and one that leads to the stomach, called the esophagus.