File Name: gi system anatomy and physiology .zip
- Anatomy and physiology of the stomach
- Gastrointestinal system anatomy
- Overview of the Digestive System
- Gastrointestinal system anatomy
The gastrointestinal tract begins at the mouth and ends at the anus Fig. Its purpose is to mechanically and enzymatically digest food, absorb nutrients and water, protect the body from microbial invasion, and expel feces. Food enters the mouth where mechanical and enzymatic digestion begins and then is propelled down the esophagus and into the stomach where digestion continues.
Anatomy and physiology of the stomach
The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. Although the small intestine is the workhorse of the system, where the majority of digestion occurs, and where most of the released nutrients are absorbed into the blood or lymph, each of the digestive system organs makes a vital contribution to this process [link].
As is the case with all body systems, the digestive system does not work in isolation; it functions cooperatively with the other systems of the body. Consider for example, the interrelationship between the digestive and cardiovascular systems. Arteries supply the digestive organs with oxygen and processed nutrients, and veins drain the digestive tract. These intestinal veins, constituting the hepatic portal system, are unique; they do not return blood directly to the heart.
Rather, this blood is diverted to the liver where its nutrients are off-loaded for processing before blood completes its circuit back to the heart. At the same time, the digestive system provides nutrients to the heart muscle and vascular tissue to support their functioning.
The interrelationship of the digestive and endocrine systems is also critical. Hormones secreted by several endocrine glands, as well as endocrine cells of the pancreas, the stomach, and the small intestine, contribute to the control of digestion and nutrient metabolism.
In turn, the digestive system provides the nutrients to fuel endocrine function. The easiest way to understand the digestive system is to divide its organs into two main categories. The first group is the organs that make up the alimentary canal. Accessory digestive organs comprise the second group and are critical for orchestrating the breakdown of food and the assimilation of its nutrients into the body. Accessory digestive organs, despite their name, are critical to the function of the digestive system.
The main function of the organs of the alimentary canal is to nourish the body. This tube begins at the mouth and terminates at the anus. Between those two points, the canal is modified as the pharynx, esophagus, stomach, and small and large intestines to fit the functional needs of the body.
Both the mouth and anus are open to the external environment; thus, food and wastes within the alimentary canal are technically considered to be outside the body. Each accessory digestive organ aids in the breakdown of food [link]. Within the mouth, the teeth and tongue begin mechanical digestion, whereas the salivary glands begin chemical digestion. Once food products enter the small intestine, the gallbladder, liver, and pancreas release secretions—such as bile and enzymes—essential for digestion to continue.
Together, these are called accessory organs because they sprout from the lining cells of the developing gut mucosa and augment its function; indeed, you could not live without their vital contributions, and many significant diseases result from their malfunction. Even after development is complete, they maintain a connection to the gut by way of ducts.
Throughout its length, the alimentary tract is composed of the same four tissue layers; the details of their structural arrangements vary to fit their specific functions. Starting from the lumen and moving outwards, these layers are the mucosa, submucosa, muscularis, and serosa, which is continuous with the mesentery see [link].
The mucosa is referred to as a mucous membrane, because mucus production is a characteristic feature of gut epithelium. The membrane consists of epithelium, which is in direct contact with ingested food, and the lamina propria, a layer of connective tissue analogous to the dermis.
In addition, the mucosa has a thin, smooth muscle layer, called the muscularis mucosa not to be confused with the muscularis layer, described below. Epithelium —In the mouth, pharynx, esophagus, and anal canal, the epithelium is primarily a non-keratinized, stratified squamous epithelium.
In the stomach and intestines, it is a simple columnar epithelium. Notice that the epithelium is in direct contact with the lumen, the space inside the alimentary canal. Interspersed among its epithelial cells are goblet cells, which secrete mucus and fluid into the lumen, and enteroendocrine cells, which secrete hormones into the interstitial spaces between cells.
Epithelial cells have a very brief lifespan, averaging from only a couple of days in the mouth to about a week in the gut. This process of rapid renewal helps preserve the health of the alimentary canal, despite the wear and tear resulting from continued contact with foodstuffs.
Lamina propria —In addition to loose connective tissue, the lamina propria contains numerous blood and lymphatic vessels that transport nutrients absorbed through the alimentary canal to other parts of the body. The lamina propria also serves an immune function by housing clusters of lymphocytes, making up the mucosa-associated lymphoid tissue MALT. When you consider that the alimentary canal is exposed to foodborne bacteria and other foreign matter, it is not hard to appreciate why the immune system has evolved a means of defending against the pathogens encountered within it.
Muscularis mucosa —This thin layer of smooth muscle is in a constant state of tension, pulling the mucosa of the stomach and small intestine into undulating folds. These folds dramatically increase the surface area available for digestion and absorption. As its name implies, the submucosa lies immediately beneath the mucosa. A broad layer of dense connective tissue, it connects the overlying mucosa to the underlying muscularis.
It includes blood and lymphatic vessels which transport absorbed nutrients , and a scattering of submucosal glands that release digestive secretions. Additionally, it serves as a conduit for a dense branching network of nerves, the submucosal plexus, which functions as described below. The third layer of the alimentary canal is the muscularis also called the muscularis externa. The muscularis in the small intestine is made up of a double layer of smooth muscle: an inner circular layer and an outer longitudinal layer.
The contractions of these layers promote mechanical digestion, expose more of the food to digestive chemicals, and move the food along the canal. In the most proximal and distal regions of the alimentary canal, including the mouth, pharynx, anterior part of the esophagus, and external anal sphincter, the muscularis is made up of skeletal muscle, which gives you voluntary control over swallowing and defecation.
The basic two-layer structure found in the small intestine is modified in the organs proximal and distal to it. The stomach is equipped for its churning function by the addition of a third layer, the oblique muscle. While the colon has two layers like the small intestine, its longitudinal layer is segregated into three narrow parallel bands, the tenia coli, which make it look like a series of pouches rather than a simple tube.
The serosa is the portion of the alimentary canal superficial to the muscularis. Present only in the region of the alimentary canal within the abdominal cavity, it consists of a layer of visceral peritoneum overlying a layer of loose connective tissue.
Instead of serosa, the mouth, pharynx, and esophagus have a dense sheath of collagen fibers called the adventitia. These tissues serve to hold the alimentary canal in place near the ventral surface of the vertebral column.
As soon as food enters the mouth, it is detected by receptors that send impulses along the sensory neurons of cranial nerves. Without these nerves, not only would your food be without taste, but you would also be unable to feel either the food or the structures of your mouth, and you would be unable to avoid biting yourself as you chew, an action enabled by the motor branches of cranial nerves.
Intrinsic innervation of much of the alimentary canal is provided by the enteric nervous system, which runs from the esophagus to the anus, and contains approximately million motor, sensory, and interneurons unique to this system compared to all other parts of the peripheral nervous system. These enteric neurons are grouped into two plexuses. The myenteric plexus plexus of Auerbach lies in the muscularis layer of the alimentary canal and is responsible for motility , especially the rhythm and force of the contractions of the muscularis.
The submucosal plexus plexus of Meissner lies in the submucosal layer and is responsible for regulating digestive secretions and reacting to the presence of food see [link]. Extrinsic innervations of the alimentary canal are provided by the autonomic nervous system, which includes both sympathetic and parasympathetic nerves.
In general, sympathetic activation the fight-or-flight response restricts the activity of enteric neurons, thereby decreasing GI secretion and motility. In contrast, parasympathetic activation the rest-and-digest response increases GI secretion and motility by stimulating neurons of the enteric nervous system. The blood vessels serving the digestive system have two functions. They transport the protein and carbohydrate nutrients absorbed by mucosal cells after food is digested in the lumen.
Lipids are absorbed via lacteals, tiny structures of the lymphatic system. Specifically, the more anterior parts of the alimentary canal are supplied with blood by arteries branching off the aortic arch and thoracic aorta. Below this point, the alimentary canal is supplied with blood by arteries branching from the abdominal aorta.
The celiac trunk services the liver, stomach, and duodenum, whereas the superior and inferior mesenteric arteries supply blood to the remaining small and large intestines. The veins that collect nutrient-rich blood from the small intestine where most absorption occurs empty into the hepatic portal system.
This venous network takes the blood into the liver where the nutrients are either processed or stored for later use. Only then does the blood drained from the alimentary canal viscera circulate back to the heart.
The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by connective tissue. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelopes the abdominal organs [link].
The peritoneal cavity is the space bounded by the visceral and parietal peritoneal surfaces. A few milliliters of watery fluid act as a lubricant to minimize friction between the serosal surfaces of the peritoneum. Inflammation of the peritoneum is called peritonitis. Chemical peritonitis can develop any time the wall of the alimentary canal is breached, allowing the contents of the lumen entry into the peritoneal cavity. For example, when an ulcer perforates the stomach wall, gastric juices spill into the peritoneal cavity.
Hemorrhagic peritonitis occurs after a ruptured tubal pregnancy or traumatic injury to the liver or spleen fills the peritoneal cavity with blood. Even more severe peritonitis is associated with bacterial infections seen with appendicitis, colonic diverticulitis, and pelvic inflammatory disease infection of uterine tubes, usually by sexually transmitted bacteria. Peritonitis is life threatening and often results in emergency surgery to correct the underlying problem and intensive antibiotic therapy.
When your great grandparents and even your parents were young, the mortality from peritonitis was high. Aggressive surgery, improvements in anesthesia safety, the advance of critical care expertise, and antibiotics have greatly improved the mortality rate from this condition. Even so, the mortality rate still ranges from 30 to 40 percent.
The visceral peritoneum includes multiple large folds that envelope various abdominal organs, holding them to the dorsal surface of the body wall. Within these folds are blood vessels, lymphatic vessels, and nerves that innervate the organs with which they are in contact, supplying their adjacent organs.
The five major peritoneal folds are described in [link]. Note that during fetal development, certain digestive structures, including the first portion of the small intestine called the duodenum , the pancreas, and portions of the large intestine the ascending and descending colon, and the rectum remain completely or partially posterior to the peritoneum. Thus, the location of these organs is described as retroperitoneal. By clicking on this link you can watch a short video of what happens to the food you eat, as it passes from your mouth to your intestine.
Along the way, note how the food changes consistency and form. How does this change in consistency facilitate your gaining nutrients from food? The digestive system includes the organs of the alimentary canal and accessory structures.
The alimentary canal forms a continuous tube that is open to the outside environment at both ends. The organs of the alimentary canal are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The accessory digestive structures include the teeth, tongue, salivary glands, liver, pancreas, and gallbladder.
The wall of the alimentary canal is composed of four basic tissue layers: mucosa, submucosa, muscularis, and serosa.
Gastrointestinal system anatomy
The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. Although the small intestine is the workhorse of the system, where the majority of digestion occurs, and where most of the released nutrients are absorbed into the blood or lymph, each of the digestive system organs makes a vital contribution to this process [link]. As is the case with all body systems, the digestive system does not work in isolation; it functions cooperatively with the other systems of the body. Consider for example, the interrelationship between the digestive and cardiovascular systems. Arteries supply the digestive organs with oxygen and processed nutrients, and veins drain the digestive tract.
The stomach is a muscular, J-shaped organ in the upper part of the abdomen. It is part of the digestive system, which extends from the mouth to the anus. The size of the stomach varies from person to person, and from meal to meal. The stomach is part of the digestive system and is connected to the: esophagus — a tube-like organ that connects the mouth and throat to the stomach. The area where the esophagus joins the stomach is called the gastroesophageal GE junction.
Discuss the process of digestion, transport, and absorption within the gastrointestinal system. Identify the functions of the accessory organs of the gastrointestinal.
Overview of the Digestive System
The gastrointestinal tract GIT consists of a hollow muscular tube starting from the oral cavity, where food enters the mouth, continuing through the pharynx, oesophagus, stomach and intestines to the rectum and anus, where food is expelled. There are various accessory organs that assist the tract by secreting enzymes to help break down food into its component nutrients. Thus the salivary glands, liver, pancreas and gall bladder have important functions in the digestive system. Food is propelled along the length of the GIT by peristaltic movements of the muscular walls. Information on re-publishing of our images.
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion the tongue , salivary glands , pancreas , liver , and gallbladder. Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The process of digestion has three stages: the cephalic phase , the gastric phase , and the intestinal phase. The first stage, the cephalic phase of digestion, begins with gastric secretions in response to the sight and smell of food.
As adults, we know that a healthy digestive system is essential for good health because it converts food into raw materials that build and fuel our body cells. The organs of the digestive system can be separated into two main groups: those forming the alimentary canal and the accessory digestive organs.
Gastrointestinal system anatomy
Разве не так, коммандер. - Ни в коем случае! - отрезал Стратмор. Хейл вскипел: - Послушайте меня, старина. Вы отпускаете меня и Сьюзан на вашем лифте, мы уезжаем, и через несколько часов я ее отпускаю.
Лицо Стратмора побагровело. - Мистер Чатрукьян, такое уже случалось. Нет никакого файла, который мог бы заразить ТРАНСТЕКСТ. - Вы ошибаетесь, сэр! - вскричал Чатрукьян.
PDF | The anatomy and physiology of the ferret is different than cats or dogs. Gastrointestinal disease has is usually manifested by diarrhea, weight | Find, read.
Все прочитали: - …в этих бомбах использовались разные виды взрывчатого вещества… обладающие идентичными химическими характеристиками. Эти изотопы нельзя разделить путем обычного химического извлечения. Кроме незначительной разницы в атомном весе, они абсолютно идентичны. - Атомный вес! - возбужденно воскликнул Джабба.
Первая неделя оказалась последней. Солнечный удар и инфаркт. Бедолага.
Я сказала нет! - И, выдержав паузу, добавила: - И до вчерашней ночи это была правда. В глазах Сьюзан Дэвид был самим совершенством - насколько вообще такое. Одно только ее беспокоило: всякий раз, когда они куда-то ходили, он решительно противился тому, чтобы она сама платила за. Сьюзан не могла с этим смириться, видя, как он выкладывает за их обед свою дневную заработную плату, но спорить с ним было бесполезно. Она в конце концов перестала протестовать, но это продолжало ее беспокоить.
Он не привык, чтобы кто-то повышал на него голос, пусть даже это был его главный криптограф. Он немного смешался.