Anatomy Of Small And Large Intestine Pdf
File Name: anatomy of small and large intestine .zip
Nutrients are absorbed in the small intestine and waste is prepared for elimination in the large intestine. The vertebrate digestive system is designed to facilitate the transformation of food matter into the nutrient components that sustain organisms. The lower gastrointestinal tract includes the small and large intestines, rectum, anus, and accessory organs.
- Histology and Cellular Function of the Small Intestine
- The small intestine
- 34.1F: Digestive System: Small and Large Intestines
- Small intestine
The small intestine is an organ located in the gastrointestinal tract, between the stomach and the large intestine. It is, on average, 23ft long and is comprised of three structural parts; the duodenum, jejunum and ileum. Functionally, the small intestine is chiefly involved in the digestion and absorption of nutrients.
The small intestine is the part of the gastrointestinal tract where much of the digestion and absorption of food takes place. The small intestine is the part of the gastrointestinal tract that follows the stomach, which is in turn followed by the large intestine. The small intestine is the site where almost all of the digestion and absorption of nutrients and minerals from food takes place. Small intestine : An illustration of the small intestine with the duodenum, jejunum, and ileum labeled. The average length of the small intestine in an adult human male is 6.
Histology and Cellular Function of the Small Intestine
Chyme released from the stomach enters the small intestine , which is the primary digestive organ in the body. Not only is this where most digestion occurs, it is also where practically all absorption occurs. The longest part of the alimentary canal, the small intestine is about 3.
This large surface area is necessary for complex processes of digestion and absorption that occur within it. The coiled tube of the small intestine is subdivided into three regions. From proximal at the stomach to distal, these are the duodenum, jejunum, and ileum Figure The shortest region is the Just past the pyloric sphincter, it bends posteriorly behind the peritoneum, becoming retroperitoneal, and then makes a C-shaped curve around the head of the pancreas before ascending anteriorly again to return to the peritoneal cavity and join the jejunum.
The duodenum can therefore be subdivided into four segments: the superior, descending, horizontal, and ascending duodenum.
Of particular interest is the hepatopancreatic ampulla ampulla of Vater. Located in the duodenal wall, the ampulla marks the transition from the anterior portion of the alimentary canal to the mid-region, and is where the bile duct through which bile passes from the liver and the main pancreatic duct through which pancreatic juice passes from the pancreas join.
This ampulla opens into the duodenum at a tiny volcano-shaped structure called the major duodenal papilla. The hepatopancreatic sphincter sphincter of Oddi regulates the flow of both bile and pancreatic juice from the ampulla into the duodenum.
The jejunum is about 0. No clear demarcation exists between the jejunum and the final segment of the small intestine, the ileum. The ileum is the longest part of the small intestine, measuring about 1.
It is thicker, more vascular, and has more developed mucosal folds than the jejunum. The ileum joins the cecum, the first portion of the large intestine, at the ileocecal sphincter or valve. The jejunum and ileum are tethered to the posterior abdominal wall by the mesentery. The large intestine frames these three parts of the small intestine. Parasympathetic nerve fibers from the vagus nerve and sympathetic nerve fibers from the thoracic splanchnic nerve provide extrinsic innervation to the small intestine.
The superior mesenteric artery is its main arterial supply. Veins run parallel to the arteries and drain into the superior mesenteric vein. Nutrient-rich blood from the small intestine is then carried to the liver via the hepatic portal vein. The wall of the small intestine is composed of the same four layers typically present in the alimentary system.
However, three features of the mucosa and submucosa are unique. These features, which increase the absorptive surface area of the small intestine more than fold, include circular folds, villi, and microvilli Figure These adaptations are most abundant in the proximal two-thirds of the small intestine, where the majority of absorption occurs.
Also called plica circulares, or circular folds, are deep ridges in the mucosa and submucosa. Beginning near the proximal part of the duodenum and ending near the middle of the ileum, these folds facilitate absorption. Their shape causes the chyme to spiral, rather than move in a straight line, through the small intestine. Spiraling slows the movement of chyme and provides the time needed for nutrients to be fully absorbed. Within the circular folds are small 0.
There are about 20 to 40 villi per square millimeter, increasing the surface area of the epithelium tremendously. The mucosal epithelium, primarily composed of absorptive cells, covers the villi. In addition to muscle and connective tissue to support its structure, each villus contains a capillary bed composed of one arteriole and one venule, as well as a lymphatic capillary called a lacteal.
The breakdown products of carbohydrates and proteins sugars and amino acids can enter the bloodstream directly, but lipid breakdown products are absorbed by the lacteals and transported to the bloodstream via the lymphatic system. Although their small size makes it difficult to see each microvillus, their combined microscopic appearance suggests a mass of bristles, which is termed the brush border.
Fixed to the surface of the microvilli membranes are enzymes that finish digesting carbohydrates and proteins. There are an estimated million microvilli per square millimeter of small intestine, greatly expanding the surface area of the plasma membrane and thus greatly enhancing absorption. These produce intestinal juice , a slightly alkaline pH 7. Each day, about 0. The roles of the cells in the small intestinal mucosa are detailed in Table The lamina propria of the small intestine mucosa is studded with quite a bit of MALT.
Watch this animation that depicts the structure of the small intestine, and, in particular, the villi. Epithelial cells continue the digestion and absorption of nutrients and transport these nutrients to the lymphatic and circulatory systems.
In the small intestine, the products of food digestion are absorbed by different structures in the villi. Which structure absorbs and transports fats? The movement of intestinal smooth muscles includes both segmentation and a form of peristalsis called migrating motility complexes. The kind of peristaltic mixing waves seen in the stomach are not observed here. If you could see into the small intestine when it was going through segmentation, it would look as if the contents were being shoved incrementally back and forth, as the rings of smooth muscle repeatedly contract and then relax.
Segmentation in the small intestine does not force chyme through the tract. Instead, it combines the chyme with digestive juices and pushes food particles against the mucosa to be absorbed. The duodenum is where the most rapid segmentation occurs, at a rate of about 12 times per minute. In the ileum, segmentations are only about eight times per minute Figure When most of the chyme has been absorbed, the small intestinal wall becomes less distended.
At this point, the localized segmentation process is replaced by transport movements. The duodenal mucosa secretes the hormone motilin , which initiates peristalsis in the form of a migrating motility complex. These complexes, which begin in the duodenum, force chyme through a short section of the small intestine and then stop. The next contraction begins a little bit farther down than the first, forces chyme a bit farther through the small intestine, then stops.
These complexes move slowly down the small intestine, forcing chyme on the way, taking around 90 to minutes to finally reach the end of the ileum. At this point, the process is repeated, starting in the duodenum. The ileocecal valve, a sphincter, is usually in a constricted state, but when motility in the ileum increases, this sphincter relaxes, allowing food residue to enter the first portion of the large intestine, the cecum.
Relaxation of the ileocecal sphincter is controlled by both nerves and hormones. First, digestive activity in the stomach provokes the gastroileal reflex , which increases the force of ileal segmentation. Second, the stomach releases the hormone gastrin, which enhances ileal motility, thus relaxing the ileocecal sphincter. After chyme passes through, backward pressure helps close the sphincter, preventing backflow into the ileum. Because of this reflex, your lunch is completely emptied from your stomach and small intestine by the time you eat your dinner.
It takes about 3 to 5 hours for all chyme to leave the small intestine. The digestion of proteins and carbohydrates, which partially occurs in the stomach, is completed in the small intestine with the aid of intestinal and pancreatic juices. Lipids arrive in the intestine largely undigested, so much of the focus here is on lipid digestion, which is facilitated by bile and the enzyme pancreatic lipase.
Moreover, intestinal juice combines with pancreatic juice to provide a liquid medium that facilitates absorption. The intestine is also where most water is absorbed, via osmosis. This distinguishes the small intestine from the stomach; that is, enzymatic digestion occurs not only in the lumen, but also on the luminal surfaces of the mucosal cells. For optimal chemical digestion, chyme must be delivered from the stomach slowly and in small amounts. This is because chyme from the stomach is typically hypertonic, and if large quantities were forced all at once into the small intestine, the resulting osmotic water loss from the blood into the intestinal lumen would result in potentially life-threatening low blood volume.
In addition, continued digestion requires an upward adjustment of the low pH of stomach chyme, along with rigorous mixing of the chyme with bile and pancreatic juices. Both processes take time, so the pumping action of the pylorus must be carefully controlled to prevent the duodenum from being overwhelmed with chyme. Lactose intolerance is a condition characterized by indigestion caused by dairy products.
It occurs when the absorptive cells of the small intestine do not produce enough lactase, the enzyme that digests the milk sugar lactose. In most mammals, lactose intolerance increases with age. In contrast, some human populations, most notably Caucasians, are able to maintain the ability to produce lactase as adults. In people with lactose intolerance, the lactose in chyme is not digested.
Bacteria in the large intestine ferment the undigested lactose, a process that produces gas. In addition to gas, symptoms include abdominal cramps, bloating, and diarrhea. Symptom severity ranges from mild discomfort to severe pain; however, symptoms resolve once the lactose is eliminated in feces.
The hydrogen breath test is used to help diagnose lactose intolerance. Lactose-tolerant people have very little hydrogen in their breath. Those with lactose intolerance exhale hydrogen, which is one of the gases produced by the bacterial fermentation of lactose in the colon. After the hydrogen is absorbed from the intestine, it is transported through blood vessels into the lungs.
There are a number of lactose-free dairy products available in grocery stores. In addition, dietary supplements are available. Taken with food, they provide lactase to help digest lactose. The large intestine is the terminal part of the alimentary canal. The primary function of this organ is to finish absorption of nutrients and water, synthesize certain vitamins, as well as to form, store, and eliminate feces from the body. The large intestine runs from the appendix to the anus.
It frames the small intestine on three sides. Despite its being about one-half as long as the small intestine, it is called large because it is more than twice the diameter of the small intestine, about 3 inches. The large intestine is subdivided into four main regions: the cecum, the colon, the rectum, and the anus.
The small intestine
This article — the fifth in a six-part series describes the physiology and functions of the large intestine, the last portion of the gastrointestinal tract, as well as common conditions of both the small and large intestine. In the large intestine — the final section of the gastrointestinal tract — absorption of water and electrolytes takes place and colonic bacteria complete the process of chemical digestion. The large intestine is also where faeces are formed from the remains of food and fluid combined with by-products of the body. Intestinal content is pushed back and forth by haustral contractions and antiperistaltic contractions, until faeces are finally pushed towards the anal canal by mass movements. This article, the fifth in a six-part series exploring the gastrointestinal tract, describes the anatomy and functions of the large intestine.
The small intestine is the longest section of the digestive tube and consists of three segments forming a passage from the pylorus to the large intestine:. In most animals, the length of the small intestine is roughly 3. Although precise boundaries between these three segments of bowel are not observed grossly or microscopically, there are histologic differences among duodenum, jejunum and ileum. A bulk of the small intestine is suspended from the body wall by an extension of the peritoneum called the mesentery. As seen in the image to the right, blood vessels to and from the intestine lie between the two sheets of the mesentery. Lymphatic vessels are also present, but are not easy to discern grossly in normal specimens. It is within the small intestine that the final stages of enzymatic digestion occur, liberating small molecules capable of being absorbed.
Chyme released from the stomach enters the small intestine , which is the primary digestive organ in the body. Not only is this where most digestion occurs, it is also where practically all absorption occurs. The longest part of the alimentary canal, the small intestine is about 3. This large surface area is necessary for complex processes of digestion and absorption that occur within it. The coiled tube of the small intestine is subdivided into three regions. From proximal at the stomach to distal, these are the duodenum, jejunum, and ileum Figure
34.1F: Digestive System: Small and Large Intestines
Small intestine , a long, narrow, folded or coiled tube extending from the stomach to the large intestine ; it is the region where most digestion and absorption of food takes place. It is about 6. A thin membranous material, the mesentery , supports and somewhat suspends the intestines. The mesentery contains areas of fat that help retain heat in the organs, as well as an extensive web of blood vessels. Nerves lead to the small intestine from two divisions of the autonomic nervous system: parasympathetic nerves initiate muscular contractions that move food along the tract peristalsis , and sympathetic nerves suppress intestinal movements.
Skip to content. Access to the supplemental resources for this session is password-protected and restricted to University of Michigan students. If you are a University of Michigan student enrolled in a histology course at the University of Michigan, please click on the following link and use your Kerberos-password for access to download lecture handouts and the other resources. To help you keep track of changes in the various layers, you can fill in this spreadsheet as you work through today's and next week's labs. The histology of the wall of the small intestine differs somewhat in the duodenum, jejunum, and ileum, but the changes occur gradually from one end of the intestine to the other.
The small intestine or small bowel is an organ in the gastrointestinal tract where most of the end absorption of nutrients and minerals from food takes place. It lies between the stomach and large intestine , and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The small intestine is about 20 feet 6 meters long and folds many times to fit in the abdomen.
Сто десять? - оживился Джабба.
Мидж, - сказал Бринкерхофф, - Джабба просто помешан на безопасности ТРАНСТЕКСТА. Он ни за что не установил бы переключатель, позволяющий действовать в обход… - Стратмор заставил. - Она не дала ему договорить. Бринкерхофф почти физически ощущал, как интенсивно работают клеточки ее мозга. - Помнишь, что случилось в прошлом году, когда Стратмор занимался антисемитской террористической группой в Калифорнии? - напомнила .
Сьюзан посмотрела на экран и перевела взгляд на диалоговое окно. В самом низу она увидела слова: РАССКАЖИТЕ МИРУ О ТРАНСТЕКСТЕ СЕЙЧАС ВАС МОЖЕТ СПАСТИ ТОЛЬКО ПРАВДА Сьюзан похолодела. В АНБ сосредоточена самая секретная государственная информация: протоколы военной связи, разведданные, списки разведчиков в зарубежных странах, чертежи передовой военной техники, документация в цифровом формате, торговые соглашения, - и этот список нескончаем.
Мысли ее смешались. Хоть бы замолчала эта омерзительная сирена. Почему Стратмор отмел такую возможность. Хейл извивался на полу, стараясь увидеть, чем занята Сьюзан. - Что .
Gross and Microscopic Anatomy of the Small Intestine
Был субботний вечер, и севильский морг не работал. Молодой лейтенант пустил туда Беккера по распоряжению севильской гвардии - похоже, у этого приезжего американца имелись влиятельные друзья. Беккер осмотрел одежду. Среди вещей были паспорт, бумажник и очки, засунутые кем-то в один из ботинков. Еще здесь был вещевой мешок, который полиция взяла в отеле, где остановился этот человек. Беккер получил четкие инструкции: ни к чему не прикасаться, ничего не читать.
Продвигаясь по служебной лестнице, Тревор Стратмор прославился умением сжато и одновременно глубоко анализировать сложнейшие ситуации. Он обладал почти сверхъестественной способностью преодолевать моральные затруднения, с которыми нередко бывают связаны сложные решения агентства, и действовать без угрызений совести в интересах всеобщего блага. Ни у кого не вызывало сомнений, что Стратмор любит свою страну. Он был известен среди сотрудников, он пользовался репутацией патриота и идеалиста… честного человека в мире, сотканном из лжи. За годы, прошедшие после появления в АНБ Сьюзан, Стратмор поднялся с поста начальника Отдела развития криптографии до второй по важности позиции во всем агентстве. Теперь только один человек в АНБ был по должности выше коммандера Стратмора - директор Лиланд Фонтейн, мифический правитель Дворца головоломок, которого никто никогда не видел, лишь изредка слышал, но перед которым все дрожали от страха. Он редко встречался со Стратмором с глазу на глаз, но когда такое случалось, это можно было сравнить с битвой титанов.
- Посмотрите уран. Его сверхкритическую массу. - М-м… сто десять фунтов, - сказала Соши. - Сто десять? - оживился Джабба. - Сколько будет сто десять минус тридцать пять и две десятых. - Семьдесят четыре и восемь десятых, - сказала Сьюзан.
Выключив паяльник, он отложил в сторону фонарик и некоторое время отдыхал, лежа под большим стационарным компьютером. Затекшая шея причиняла ему сильную боль. Такая работа была непростой, особенно для человека его комплекции. И они делают их все более и более миниатюрными, - подумал .
Коммандер Тревор Стратмор снова стал самим собой - человеком железной логики и самообладания, делающим то, что полагалось делать. Последние слова предсмертной записки Хейла крутились у нее в голове, не повинуясь никаким приказам. И в первую очередь я искренне сожалею о Дэвиде Беккере.