DOCSLIB.ORG

Digestive System and Glands 1

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Digestive System and Glands 1 Dr. Randall E. Merchant [email protected] DIGESTIVE SYSTEM & GLANDS Objectives 1. Describe the four basic layers that form the walls of the GI tract and know how they vary from one organ to another along the tract. 2. Identify the structures on the CD listed in the laboratory guide. 3. Describe the appearance and be able to recognize the following junctions: esophagus- stomach, stomach-small intestine, small intestine-large intestine, rectum-anal canal, and anal canal-anus. 4. Differentiate the three different types of mucosal glands in the stomach and describe the morphology and function of their component cells. 5. Characterize the differences between the duodenum and the remainder of small intestine as well as the differences between the small and large intestine and appendix. 6. Understand why the pancreas is both an exocrine and endocrine gland. Trace the pathway of exocrine secretions from the acinar cells to the small intestine. 7. Describe the architecture of the hepatic sinusoid and explain the route of blood and bile flow through the liver. 8. Trace the usual route by which proteins, carbohydrates, and fats taken up by the small intestine reach the liver. 9. Understand the anatomic and functional criteria that define the three forms of hepatic lobulation. Be able to identify structures located in a portal canal. I. General Description and Considerations Regarding the Tubular Digestive Tract A. Paradox of similarity and Change: 1. All organs of the GI tract are modifications of a simple tube 2. Epithelium of the entire tract is derived from a single embryonic germ cell layer 3. All organs have some function related to digestion 4. All areas of the tract have basically the same histological layers However, 5. Abrupt changes occur in the epithelium from one organ to the next 6. Drastic modifications of the mucosa occur from one organ to the next 7. Each organ along the tract performs a separate and unique function related to digestion B. General description of layers common to all organs of the GI tract 1. Mucosa - three components a. epithelium - shape and number of layers dependent upon function of organ - functions include conduction, absorption and secretion - invaginations of epithelium form glands - avascular and sits on a basement membrane b. lamina propria - loose CT - composed of collagen and elastic fibers along with various CT cell types - occasional areas of diffuse and nodular lymphoid tissue - some areas contain varying numbers of exocrine glands - contains small blood vessels, nerves, and lymphatics c. muscularis mucosa - smooth muscle mostly running longitudinally - relative thickness greatest in esophagus - contraction helps empty glands of mucosa & helps transport material along the tube - innervated by post-ganglionic parasympathetic fibers originating from Meissner's plexus General Plan of the Tubular Digestive Tract 2. Submucosa - classified as dense irregular CT a. coarser fiber bundles than in lamina propria b. large plexi of blood vessels and lymphatics, nerves, and Meissner's plexi (pre-ganglionic fibers from Vagus Nerve) c. contain glands in esophagus and duodenum 3. Muscularis externa - formed of smooth muscle except in upper esophagus a. varies in thickness and number of layers b. usually inner circular and outer longitudinal layers c. innervated by post-ganglionic parasympathetic fibers originating from Auerbach's (myenteric) plexus located between the two muscle layers (pre-ganglionic fibers from Vagus Nerve) d. functions - mainly in peristalsis - maintain tonus and propels food onward - circular layer controls caliber of lumen, also churns and propels food along - longitudinal muscle contraction shortens tube locally 4. Adventitia - dense irregular CT a. contains blood vessels, lymphatics, and nerve fibers b. when covered with visceral peritoneum called a serosa II. Esophagus A. General description and functions 1. Length, location, & relationships a. conveys food from pharynx to stomach b. about 10" long, all but final 1" intrathoracic 2. Innervation a. smooth muscle layers innervated by postganglionic parasympathetics from Meissner's and Auerbach's plexi b. vascular smooth muscle innervated by postganglionic sympathetics from cervical and thoracic sympathetic trunks c. skeletal muscle supplied by efferent fibers of Vagus Nerve 3. Functions a. completes warming or cooling of food b. conveys food by gravity and muscular contraction c. glands secrete mucus for lubrication B. Mucosa 1. Non-keratinized stratified squamous epithelium 2. Lamina propria - contains esophageal cardiac glands (mucus secreting) 3. Muscularis mucosa - mostly longitudinally oriented a. occurs as discreet bundles in upper portion b. continuous and thickest in lower portion c. innervated by post-ganglionic fibers from Meisner’s plexus C. Submucosa 1. Contributes to large longitudinal folds of esophagus - these smooth out during swallowing 2. Contains esophageal glands - compound tubuloalveolar, mucus secreting D. Muscularis externa - determines level of histological section 1. Upper 1/3 - composed of almost all skeletal muscle - because initiation of swallowing is voluntary 2. Middle 1/3 - a mixture of smooth and skeletal muscle 3. Lower 1/3 - composed only of smooth muscle a. at junction with stomach this layer forms a physiologic sphincter that prevents regurgitation of the stomach contents b. peppermint, alcohol, and nicotine will relax the sphincter, help you feel less "full" c. reflux of stomach contents into this area causes feeling of heartburn 4. Smooth muscle innervated by post-ganglionic parasympathetics from Auerbach's plexus, skeletal muscle by spinal nerves E. Adventitia 1. Intrathoracic portion blends with surrounding dense irregular CT 2. Below diaphragm covered with visceral peritoneum III. Stomach A. General description and functions 1. Role in digestion and storage a. acidifies and converts swallowed food into a viscous fluid called chyme b. mucosa produces digestive enzymes 2. Four gross anatomic vs. three histological divisions a. gross anatomic divisions - cardiac, fundic, body, and pyloric b. histological divisions - cardiac, fundic, and pyloric - based on gland structure - no sharp transitions between divisions 3. Rugae - large longitudinal folds formed by the mucosa and submucosa, most prominent when stomach empty B. Mucosa 1. Surface a. esophageal-gastric junction - abrupt change from stratified squamous to simple columnar b. gastric pits - fine furrows, lead into glands c. simple columnar epithelium - forms sheet gland, all mucus secreting, mucus has a basic pH - continuous with epithelium of gastric pits - cells anchored to each other by cell junctions - secretions form protective barrier from strong acidity of stomach content - cells continuously sloughed off - survive only about 3 days 2. Gastric gland structure & nomenclature a. simple, branched tubular glands - occupy entire thickness of mucosa b. each gland has a neck, body, and base 3. Lamina propria a. occupies space between glands and pits b. richly vascularized and slips of smooth muscle from muscularis mucosa 4. Cardiac glands a. location - in cardiac region of stomach, near esophageal orifice b. length of gland approximately equal to depth of pit c. component cells - mostly mucus secreting cells with a few parietal and enteroendocrine cells d. primary function is to produce a protective mucus secretion 5. Fundic glands a. located in fundic and body regions of the stomach b. one or more open into each gastric pit, glands are much longer than their pits are deep c. are classified as simple branched tubular d. are closely packed and orientated perpendicular to surface e. are the major source of gastric juice 6. Cells of the fundic glands a. mucous neck cells - appear basophilic with H&E stain • relatively few, located in necks of glands • produce an acidic mucous secretion b. parietal cells - appear acidophilic with H&E stain • the greater proportion of cells in upper part of glands • have a secretory canaliculus - increases surface area • contain an abundance of mitochondria (why cytoplasm eosinophilic) • secrete H+ and Cl- • secrete gastric intrinsic factor - binds to vitamin B12 and this allows it to be absorbed in small intestine, the vitamin is needed for proper RBC maturation - a lack of this factor (or vitamin) causes pernicious anemia c. chief cells - appear basophilic with H&E stain • dominant cell type in the lower half of glands • have zymogen granules in their apical cytoplasm • secrete pepsinogen - converted to pepsin by low pH - important enzyme in the digestion of proteins d. enteroendocrine cells - variable staining with H&E • a collection of at least 12 different cell types each of which secrete a specific endocrine hormones • found mostly in bases of glands • granules mostly on side of basal lamina • some produce gastrin - stimulates secretions of chief and parietal cells and increases gastric motility • some synthesize serotonin - triggers contraction of smooth muscle of blood vessels - leads to a slowing of gastric activity • secretions enter blood (endocrine) or affect adjacent cells (paracrine) 6. Pyloric glands a. located in distal 4-5 cm of stomach b. empty into wide, deep pits c. are simple, branched tubular which d. are very coiled e. composed of almost completely of mucus secreting cells with a few parietal cells and enteroendocrine cells C. Accessory coats 1. Submucosa - dense irregular CT 2. Muscularis externa - inner oblique, middle circular, and outer longitudinal layers a. pyloric sphincter - formed by middle circular layer b. Auerbach's plexus between circular and longitudinal layers c. functions in mixing and emptying contents of stomach d. emptying of stomach due to peristalsis and intermittent relaxation of the pyloric sphincter 3. Serosa - loose CT covered with mesothelium (visceral peritoneum) .
Load more

Recommended publications
  • The Anatomy of the Rectum and Anal Canal
    BASIC SCIENCE identify the rectosigmoid junction with confidence at operation. The anatomy of the rectum The rectosigmoid junction usually lies approximately 6 cm below the level of the sacral promontory. Approached from the distal and anal canal end, however, as when performing a rigid or flexible sigmoid- oscopy, the rectosigmoid junction is seen to be 14e18 cm from Vishy Mahadevan the anal verge, and 18 cm is usually taken as the measurement for audit purposes. The rectum in the adult measures 10e14 cm in length. Abstract Diseases of the rectum and anal canal, both benign and malignant, Relationship of the peritoneum to the rectum account for a very large part of colorectal surgical practice in the UK. Unlike the transverse colon and sigmoid colon, the rectum lacks This article emphasizes the surgically-relevant aspects of the anatomy a mesentery (Figure 1). The posterior aspect of the rectum is thus of the rectum and anal canal. entirely free of a peritoneal covering. In this respect the rectum resembles the ascending and descending segments of the colon, Keywords Anal cushions; inferior hypogastric plexus; internal and and all of these segments may be therefore be spoken of as external anal sphincters; lymphatic drainage of rectum and anal canal; retroperitoneal. The precise relationship of the peritoneum to the mesorectum; perineum; rectal blood supply rectum is as follows: the upper third of the rectum is covered by peritoneum on its anterior and lateral surfaces; the middle third of the rectum is covered by peritoneum only on its anterior 1 The rectum is the direct continuation of the sigmoid colon and surface while the lower third of the rectum is below the level of commences in front of the body of the third sacral vertebra.
    [Show full text]
  • Fecal Incontinence/Anal Incontinence
    Fecal Incontinence/Anal Incontinence What are Fecal incontinence/ Anal Incontinence? Fecal incontinence is inability to control solid or liquid stool. Anal incontinence is the inability to control gas and mucous in addition to the inability to control stool. The symptoms range from mild release of gas to a complete loss of control. It is a common problem affecting 1 out of 13 women under the age of 60 and 1 out of 7 women over the age of 60. Men can also be have this condition. Anal incontinence is a distressing condition that can interfere with the ability to work, do daily activities and enjoy social events. Even though anal incontinence is a common condition, people are uncomfortable discussing this problem with family, friends, or doctors. They often suffer in silence, not knowing that help is available. Normal anatomy The anal sphincters and puborectalis are the primary muscles responsible for continence. There are two sphincters: the internal anal sphincter, and the external anal sphincter. The internal sphincter is responsible for 85% of the resting muscle tone and is involuntary. This means, that you do not have control over this muscle. The external sphincter is responsible for 15% of your muscle tone and is voluntary, meaning you have control over it. Squeezing the puborectalis muscle and external anal sphincter together closes the anal canal. Squeezing these muscles can help prevent leakage. Puborectalis Muscle Internal Sphincter External Sphincter Michigan Bowel Control Program - 1 - Causes There are many causes of anal incontinence. They include: Injury or weakness of the sphincter muscles. Injury or weakening of one of both of the sphincter muscles is the most common cause of anal incontinence.
    [Show full text]
  • Rectum & Anal Canal
    Rectum & Anal canal Dr Brijendra Singh Prof & Head Anatomy AIIMS Rishikesh 27/04/2019 EMBRYOLOGICAL basis – Nerve Supply of GUT •Origin: Foregut (endoderm) •Nerve supply: (Autonomic): Sympathetic Greater Splanchnic T5-T9 + Vagus – Coeliac trunk T12 •Origin: Midgut (endoderm) •Nerve supply: (Autonomic): Sympathetic Lesser Splanchnic T10 T11 + Vagus – Sup Mesenteric artery L1 •Origin: Hindgut (endoderm) •Nerve supply: (Autonomic): Sympathetic Least Splanchnic T12 L1 + Hypogastric S2S3S4 – Inferior Mesenteric Artery L3 •Origin :lower 1/3 of anal canal – ectoderm •Nerve Supply: Somatic (inferior rectal Nerves) Rectum •Straight – quadrupeds •Curved anteriorly – puborectalis levator ani •Part of large intestine – continuation of sigmoid colon , but lacks Mesentery , taeniae coli , sacculations & haustrations & appendices epiploicae. •Starts – S3 anorectal junction – ant to tip of coccyx – apex of prostate •12 cms – 5 inches - transverse slit •Ampulla – lower part Development •Mucosa above Houstons 3rd valve endoderm pre allantoic part of hind gut. •Mucosa below Houstons 3rd valve upto anal valves – endoderm from dorsal part of endodermal cloaca. •Musculature of rectum is derived from splanchnic mesoderm surrounding cloaca. •Proctodeum the surface ectoderm – muco- cutaneous junction. •Anal membrane disappears – and rectum communicates outside through anal canal. Location & peritoneal relations of Rectum S3 1 inch infront of coccyx Rectum • Beginning: continuation of sigmoid colon at S3. • Termination: continues as anal canal, • one inch below
    [Show full text]
  • 48 Anal Canal
    Anal Canal The rectum is a relatively straight continuation of the colon about 12 cm in length. Three internal transverse rectal valves (of Houston) occur in the distal rectum. Infoldings of the submucosa and the inner circular layer of the muscularis externa form these permanent sickle- shaped structures. The valves function in the separation of flatus from the developing fecal mass. The mucosa of the first part of the rectum is similar to that of the colon except that the intestinal glands are slightly longer and the lining epithelium is composed primarily of goblet cells. The distal 2 to 3 cm of the rectum forms the anal canal, which ends at the anus. Immediately proximal to the pectinate line, the intestinal glands become shorter and then disappear. At the pectinate line, the simple columnar intestinal epithelium makes an abrupt transition to noncornified stratified squamous epithelium. After a short transition, the noncornified stratified squamous epithelium becomes continuous with the keratinized stratified squamous epithelium of the skin at the level of the external anal sphincter. Beneath the epithelium of this region are simple tubular apocrine sweat glands, the circumanal glands. Proximal to the pectinate line, the mucosa of the anal canal forms large longitudinal folds called rectal columns (of Morgagni). The distal ends of the rectal columns are united by transverse mucosal folds, the anal valves. The recess above each valve forms a small anal sinus. It is at the level of the anal valves that the muscularis mucosae becomes discontinuous and then disappears. The submucosa of the anal canal contains numerous veins that form a large hemorrhoidal plexus.
    [Show full text]
  • Lower Gastrointestinal Tract
    Lower Gastrointestinal Tract Hemorrhoids—Office Management and Review for Gastroenterologists Mitchel Guttenplan, MD, FACS 1 and Robert A Ganz, MD, FASGE 2 1. Medical Director, CRH Medical Corp; 2. Minnesota Gastroenterology, Chief of Gastroenterology, Abbott-Northwestern Hospital, Associate Professor of Medicine, University of Minnesota Abstract symptomatic hemorrhoids and anal fissures are very common problems. This article provides a review of the anatomy and physiology of the anorectum along with a discussion of the diagnosis and treatment of hemorrhoids and the commonly associated matters of anal sphincter spasm and fissures. The various office treatment modalities for hemorrhoids are discussed, as are the specifics of rubber band ligation (rBL), and a strategy for the office treatment of these problems by the gastroenterologist is given. The crh o’regan system™ is a technology available to the gastroenterologist that provides a safe, effective, and efficient option for the non-surgical treatment of hemorrhoids in the office setting. Keywords hemorrhoids, anal fissure, rubber band ligation, crh o’regan system™ Disclosure: Mitchel guttenplan is Medical Director of crh Medical Products corporation, the manufacturer of the crh o’regan system™. robert A ganz is a consultant to and holds equity in crh Medical Products corporation. Received: 2 november 2011 Accepted: 30 november 2011 Citation: Touchgastroentorology.com ; December, 2011. Correspondence: Mitchel guttenplan, MD, fAcs, 3000 old Alabama rd, suite 119 #183, Alpharetta, gA 30022-8555, us. e: [email protected] Diseases of the anorectum, including hemorrhoids and anal fissures, are experience also makes it clear that hemorrhoid sufferers frequently very common. The care of these entities is typically left to general and have additional anorectal issues that may both confuse the diagnosis colorectal surgeons.
    [Show full text]
  • Anal Cancer Anal Cancer, Also Known As Anal Carcinoma, Is Cancer of the Anus
    Anal Cancer Anal cancer, also known as anal carcinoma, is cancer of the anus. To help diagnose this condition, your doctor will perform a digital rectal exam and anoscopy. An MRI, CT, PET/CT, or an endoanal ultrasound may also be ordered by your doctor. Depending on the size, location, and extent of the cancer, treatments may include surgery, radiation therapy and chemotherapy. What is anal cancer? Anal cancer is a cancer that begins in the anus, the opening at the end of the gastrointestinal tract through which stool, or solid waste, leaves the body. The anus begins at the bottom of the rectum, which is the last part of the large intestine (also called the colon). Anal cancer usually affects adults over age 60 and women more often than men. More than 8,000 people in the U.S. are diagnosed with anal cancer each year. Anal cancer symptoms may include changes in bowel habits and changes in and around the anal area, including: bleeding and itching pain or pressure unusual discharge a lump or mass fecal incontinence fistulae. Some patients with anal cancers do not experience any symptoms. Some non-cancerous conditions, such as hemorrhoids and fissures, may cause similar symptoms. How is anal cancer diagnosed and evaluated? To diagnose the cause of symptoms, your doctor may perform: Digital rectal examination (DRE): Digital Rectal Exam (DRE): This test examines the lower rectum and the prostate gland in males to check for abnormalities in size, shape or texture. The term "digital" refers to the clinician's use of a gloved lubricated finger to conduct the exam.
    [Show full text]
  • Bowel Function Anatomy
    BOWEL FUNCTION ANATOMY Most of America gives little thought to bowel control. However, bowel control is actually a complex process involving the coordination of many different muscles and nerves. The bowel is considered to be a part of the digestive or gastrointestinal system. It is designed to help the body absorb nutrients and fluids from the foods we eat and drink. After taking out everything the body needs, the bowel then expels the leftover waste. The beginning of the bowel is the small intestine, sometimes referred to as the small bowel. This is where the useful nutrients are absorbed from what you eat. The small bowel delivers the waste to the colon, or large bowel. The colon is a 5-6 foot long muscular tube that delivers stool to the rectum. As the stool moves through the colon, the fluids are removed and absorbed into the body. The consistency of the stool is dependent upon many things, including how long the stool sits in the colon, how much of the water has been absorbed from the waste, and the amount of fiber and fluids in your diet. Stool consistency can vary from hard lumps to mushy to very loose, watery stool. The best and easiest consistency of stool is soft, like toothpaste; this consistency may be attained by adding fiber to your diet. Fiber helps move waste through the colon because it is indigestible by the human body. In other words, fiber adds ‘bulk’ to the stool. It is important to eat a diet high in fiber, however, most Americans lack fiber in their diet.
    [Show full text]
  • Progress Report Anal Continence
    Gut: first published as 10.1136/gut.12.10.844 on 1 October 1971. Downloaded from Gut, 1971, 12, 844-852 Progress report Anal continence Anal continence depends on an adaptable barrier formed at the ano-rectal junction and in the anal canal by a combination of forces. These are due in part to the configuration of the region and in part to the action of muscles. The forces are activated in response to sensory information obtained from the rectum and the anal canal. In order to understand some of the concepts of the mechanism of anal continence, some of the features of the anatomy and physiology of the region will be discussed. Anatomy (Fig. 1) The lumen of the rectum terminates at the pelvic floor and is continued, downwards and posteriorly, as the anal canal, passing through the levator ani muscle sheet and surrounded by the internal and external anal sphincters. The anal canal is 2.5 to 5 cm in length and 3 cm in diameter when distended. The axis of the rectum forms almost a right angle (average 820) with the axis of the anal canal. It has been established by radiological studies that the anal canal is an antero-posterior slit in the resting state.' The former concept of http://gut.bmj.com/ the anal canal being surrounded successively craniocaudally by the internal anal sphincter and then the external anal sphincter has been replaced by the knowledge that the two muscles overlap to a considerable extent with the external sphincter wrapped round the internal sphincter2'3.
    [Show full text]
  • Studies of the Reflex Activity of the External Sphincter Ani in Spinal Man
    STUDIES OF THE REFLEX ACTIVITY OF THE EXTERNAL SPHINCTER ANI IN SPINAL MAN By J. MELZAK, M.D. National Spinal Injuries Centre, Stoke Mandeville Hospital, Aylesbury and N. H. PORTER, F.R.C.S. Department of Surgery, Guy's Hospital, London INTRODUCTION IN normal man, the anus remains closed unless faeces or wind are to be evacuated. Anal closure is maintained by the tone of the anal sphincters. The importance of the internal and external anal sphincters in maintaining anal closure has for long been a controversial subject. Gowers (I877) made classical contributions to the understanding of visceral reflexes and sphincter activity. He postulated a complex lumbar reflex centre controlling the function of the rectum and anal sphincter. He demonstrated tonic contraction of the anal sphincter in paraplegic patients, pro­ vided the lumbar segments of the cord and the corresponding motor and sensory nerves were intact. Starling (I900) considered that both sphincters were tonically contracted. Frankl-Hochwart and Frohlich (I900) found that 60 per cent. of the tonic closure of the anus in dogs was due to the activity of the external sphincter. Matti (I 909, I9I 0) considered that both sphincters were tonically contracted in man and dogs. Denny-Brown and Robertson (I935) concluded from their studies that the postural tone of the internal anal sphincter was a local phenomenon and related to the peripheral nervous plexus. They also held the view that the external sphincter on the other hand was not tonically contracted. The external anal sphincter has repeatedly been the subject of electromyo­ graphic investigation. In I930, Beck, using steel needle electrodes and a string galvanometer, observed action potentials on contraction and relaxation of this muscle in a number of dogs and in one man.
    [Show full text]
  • Anatomy of Anal Canal
    Anatomy of Anal Canal Dr Garima Sehgal Associate Professor Department of Anatomy King George’s Medical University, UP, Lucknow DISCLAIMER: • The presentation includes images which are either hand drawn or have been taken from google images or books. • They are being used in the presentation only for educational purpose. • The author of the presentation claims no personal ownership over images taken from books or google images. • However, the hand drawn images are the creation of the author of the presentation Subdivisions of the perineum • Transverse line joining the anterior part of ischial tuberosities divides perineum into: 1. Urogenital region / triangle- ANTERIORLY 2. Anal region / triangle - POSTERIORLY Anal canal may be affected by many conditions that are not so rare, not necessarily serious and endangering to life but on the contrary very INCAPACITATING Haemorrhoids Anal fistula Anal fissure Perianal abscess Learning objectives At the end of this teaching session on anatomy of Anal canal all the MBBS 1st Year students must be able to correctly: • Describe the location, extent and dimensions of the anal canal • Enumerate the relations of the anal canal • Enumerate the subdivisions of anal canal • Describe & Diagrammatically display the special features on the interior of the anal canal • Discuss the importance of pectinate / dentate line • Write a short note on the arterial supply, venous drainage, nerve supply & lymphatic drainage • Write a short note on the sphincters of the anal canal • Describe the anatomical basis of internal
    [Show full text]
  • Colon and Rectum
    AJC12 7/14/06 1:24 PM Page 107 12 Colon and Rectum (Sarcomas, lymphomas, and carcinoid tumors of the large intestine or appendix are not included.) C18.0 Cecum C18.5 Splenic flexure of C18.9 Colon, NOS C18.1 Appendix colon C19.9 Rectosigmoid C18.2 Ascending colon C18.6 Descending colon junction C18.3 Hepatic flexure of C18.7 Sigmoid colon C20.9 Rectum, NOS colon C18.8 Overlapping lesion of C18.4 Transverse colon colon SUMMARY OF CHANGES •A revised description of the anatomy of the colon and rectum better delineates the data concerning the boundaries between colon, rectum, and anal canal. Ade- nocarcinomas of the vermiform appendix are classified according to the TNM staging system but should be recorded separately, whereas cancers that occur in the anal canal are staged according to the classification used for the anus. •Smooth extramural nodules of any size in the pericolic or perirectal fat are con- sidered lymph node metastases and will be counted in the N staging. In contrast, irregularly contoured nodules in the peritumoral fat are considered vascular invasion and will be coded as transmural extension in the T category and further denoted as either a V1 (microscopic vascular invasion) if only microscopically visible or a V2 (macroscopic vascular invasion) if grossly visible. • Stage Group II is subdivided into IIA and IIB on the basis of whether the primary tumor is T3 or T4 respectively. • Stage Group III is subdivided into IIIA (T1-2N1M0), IIIB (T3-4N1M0), or IIIC (any TN2M0). INTRODUCTION The TNM classification for carcinomas of the colon and rectum provides more detail than other staging systems.
    [Show full text]
  • Digestive System A&P DHO 7.11 Digestive System
    Digestive System A&P DHO 7.11 Digestive System AKA gastrointestinal system or GI system Function=responsible for the physical & chemical breakdown of food (digestion) so it can be taken into bloodstream & be used by body cells & tissues (absorption) Structures=divided into alimentary canal & accessory organs Alimentary Canal Long muscular tube Includes: 1. Mouth 2. Pharynx 3. Esophagus 4. Stomach 5. Small intestine 6. Large intestine 1. Mouth Mouth=buccal cavity Where food enters body, is tasted, broken down physically by teeth, lubricated & partially digested by saliva, & swallowed Teeth=structures that physically break down food by chewing & grinding in a process called mastication 1. Mouth Tongue=muscular organ, contains taste buds which allow for sweet, salty, sour, bitter, and umami (meaty or savory) sensations Tongue also aids in chewing & swallowing 1. Mouth Hard palate=bony structure, forms roof of mouth, separates mouth from nasal cavities Soft palate=behind hard palate; separates mouth from nasopharynx Uvula=cone-shaped muscular structure, hangs from middle of soft palate; prevents food from entering nasopharynx during swallowing 1. Mouth Salivary glands=3 pairs (parotid, sublingual, & submandibular); produce saliva Saliva=liquid that lubricates mouth during speech & chewing, moistens food so it can be swallowed Salivary amylase=saliva enzyme (substance that speeds up a chemical reaction) starts the chemical breakdown of carbohydrates (starches) into sugar 2. Pharynx Bolus=chewed food mixed with saliva Pharynx=throat; tube that carries air & food Air goes to trachea; food goes to esophagus When bolus is swallowed, epiglottis covers larynx which stops bolus from entering respiratory tract and makes it go into esophagus 3.
    [Show full text]