DOCSLIB.ORG

The Digestive System Chapter 15

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Digestive System Chapter 15 The Digestive System Chapter 15 Food is vital for life because it is the source of energy that drives the chemical reactions occurring in every cell. Energy is needed for muscle contraction, conduction of nerve impulses, and secretory and absorptive activities of many cells. Food, however, is not in a state suitable for immediate use as an energy source. The organs that mechanically and chemically break down food into usable molecules are collectively called the digestive system. Contents: 1. Oral cavity 2. Pharynx 3. Esophagus 4. Stomach 5. Small intestine 6. Large intestine Accessory glands/organs = contribute to digestion but food does not pass through. 1. Salivary glands 2. Pancreas 3. Liver 4. Gall bladder Functions: 1. Ingestion – taking food/drink into the body 2. Digestion – mechanical and chemical breakdown of food 3. Peristalsis – movement of food through digestive system 4. Absorption – taking nutrients into bloodstream 5. Egestion – elimination of unwanted/ undigested foods from body 6. Sensory Reception – sense of taste (chemoreceptors) 1 1. Oral Cavity = mouth. INGESTION. Lined with stratified squamous. Function: protection from abrasion vestibule = space between lips/cheeks and teeth lips = skeletal muscle = orbiculans oris muscle cheeks = skeletal muscle = buccinators muscle fauces = boundary between oral cavity and oropharynx. Location: between posterior tongue and tip of uvula. A. tongue A large, flexible muscular organ. Covered with stratified squamous. Protection from abrasion. –superior surface contains chemoreceptors (taste buds) B. Teeth Normally, 32 teeth in adults. Tooth socket = alveolus Each tooth held in place by periodontal ligaments tooth formula = 2 1 2 3 2 1 2 3 2 2. Accessory Glands of the Oral Cavity - 3 pairs of salivary glands located external to oral cavity - each has a duct that carries saliva into mouth (exocrine gland) -ducted! - functions: 1) keep mouth moist 2) begin chemical digestion of food A. Parotid gland - largest salivary gland. Secretes watery saliva. When infected with virus à mumps http://www.youtube.com/watch?v=5mZBz746o2E B. Submandibular gland middle in size. Secretes both a watery and mucousy saliva http://www.youtube.com/watch?v=uY_W1oToNJA C. Sublingual gland – smallest in size. Secretes mucousy saliva. 3 3. Pharynx - common openings for the respiratory and digestive systems A. Nasopharynx - only associated with the respiratory system B. Oropharynx – Middle division of pharynx Boundaries: fauces (opening of mouth into pharynx)- tip of epiglottis Lined with stratified squamous Common area for air, food and drink C. Laryngopharynx Inferior division of pharynx Boundaries: tip of epiglottis àtop of esophagus Lined with stratified squamous When swallowing, smooth muscle pulls epiglottis down to cover/protect airway. Food/drink channeled into esophagus. 4. Esophagus A long muscular tube extending from the pharynx to stomach. Consists of both skeletal and smooth muscle. Located posterior to trachea and anterior to vertebral column. Lined with stratified squamous Sphincter muscle at both ends Upper esophageal sphincter * skeletal muscle Lower esophageal sphincter *smooth muscle 5. Stomach http://www.youtube.com/watch?v=ZvudWuvMjtA An expandable muscular sack. Has 3 layers of smooth muscle Lined with simple columnar 4 Wall of stomach contains several gastric glands that secrete: a) HCL b) Digestive enzymes c) Mucus 1. Cardiac region 2. fundus (dome) 3. Body a) lesser curvature b) greater curvature 4. pyloric region 5. pyloric sphincter (boundary between stomach and small intestine) 5 6. Small intestine - has 3 subdivisions a relatively long muscular tube about 10 feet diameter 1-2 inches all 3 subdivisions lined with simple columnar Lacteals found in small intestine wall. A. duodenum About 1 foot long Shaped like a capital “C” Inner surface highly folded with villi and microvilli to increase surface area Receives digestive enzymes from liver and pancreas 6 B. Jejunum About 3 feet long with many tightly folded curves = flexure Inner surface highly folded with villi and microvilli to increase surface area. C. Ileum About 6 feet long Has many flexures No obvious boundary between jejenum and ileum Inner surface highly folded with villi and microvilli to increase surface area. ileocecal valve = a sphincter muscle *boundary between small & large intestines. 7 7. Large Intestine - has 4 subdivisions A relatively short muscular tube About 5 feet long Diameter = 6 cm (3 inches) First 3 subdivisions lined with simple columnar. Exception: anal canal. A. Cecum A blind pouch or sack Function: storehouse of intestinal bacteria Appendix attached B. Colon * has 4 subdivisions* (see diagram) 1. Ascending colon 8 2. Transverse colon 3. Descending colon 4. Sigmoid colon 3 long thin bands of smooth muscle along entire length of colon When contract, causes the colon to pleat. Each pleat = haustrum. Haustra (pl) C. Rectum A short muscular tube about 4-5 inches long Located with in pelvic cavity Function: temporary storage of feces prior to egestion. D. Anal canal A short muscular tube about 1-2inches long. Lined with stratified squamous. Protection from abrasion. Two sphincter muscles 1) internal anal sphincter *smooth muscle ( involuntary) 2) external anal sphincter *skeletal muscle (potty training) 9 3) Anal canal ends at opening to external environment – anus. 8. Accessory organs of the digestive system A. Liver The largest internal organ of body Dozens of important physiologic functions Two major lobes (left and right) Two minor lobes (caudate and quadrate Major digestive function: produces and secretes bile Bile travels through common hepatic duct àcommon bile ductà duodenum 10 B. Gall bladder A small sac on inferior side of liver Functions: 1. temporary storage of bile overproduced by liver 2. concentration of bile while being stored. When needed, bile is released through cystic duct (unites with common hepatic duct) into duodenum C. Pancreas A long slender organ with a bumpy surface Located within C-shape of duodenum Two major junctions: 1. Endocrine – production of insulin and glucagon 2. Exocrine – produces several digestive enzymes. Enzymes travel through pancreatic duct into duodenum. Quiz #1 11 9. Digestion of Ingested Food - 2 methods of digestion: mechanical digestion = Physically breaking large pieces of food into many smaller pieces Increases surface area chemical digestion = Breaking chemical bonds within food particles Proteins à amino acids Carbohydrates à glucose 10. DIGESTION: Oral cavity, pharynx, and esophagus Mechanical digestion begins when teeth grind food into smaller pieces (mastication) Chemical digestion begins when salivary glands secrete saliva, which contains salivary amylase Begins chemical breakdown of carbohydrates Glands in tongue secrete tiny amount of enzyme lipase to begin chemical digestion of lipids Food is pressed into a loose ball by tongue (bolus) 12 11. Swallowing A. voluntary stage Bolus is pushed by tongue posteriorly through fauces into oropharynx. Bolus hits uvula, which is a “trip-wire” to initiate involuntary stage B. involuntary stage - *reflex Once in oropharynx, bolus is moved inferiorly through the rest of pharynx by a series of smooth muscles that encircle pharynx (pharyngeal constrictor muscles) Epiglottis is pulled down to protect airway Bolus pass through upper esophageal sphincter Peristalsis moves bolus down esophagus Bolus passes through lower esophageal sphincter into stomach 13 14 12. DIGESTION: Stomach A. mechanical digestion Smooth muscle in stomach wall contracts to push bolus back and forth in churning motion (mixing waves) Similar to swishing mouthwash! chyme = Liquified food in stomach. Has thin watery consistency B. chemical digestion Salivay amylase and lingual lipase still working but soon inactivated by stomach acid 1) HCl – denatures proteins (breaks 3-D structure 2) pepsin – digests proteins – small polypeptides 3) gastric lipase – digests fats/lipids àtriglycerides 4) mucus – protects stomach itself from being digested! 13. ABSORPTION: Stomach Small amount of water absorbed Most all alcohol absorbed 14. Liver Produces about 1 liter of bile /day Function: breaks large globs of fat into many smaller globs of fat (emulsification) A form of mechanical digestion which increases surface area so lipase can work more efficiently. Bile sent through a common hepatic duct àcommon bile ductà duodenum 15 Excess bile rerouted into gall bladder for storage. 15. Pancreas Secretes a combination of digestive enzymes called: pancreatic juice Pancreatic juice sent through pancreatic duct into duodenum It is basic so it neutralizes stomach acid. A. pancreatic amylase – continues carbohydrate digestion B. trypsin – continues protein digestion C. pancreatic lipase – continues lipid digestion 16. DIGESTION: Small intestine chyme passes through pyloric sphincter into small intestine A. mechanical digestion - 2 processes: Peristalisis – pushes chyme through entire small intestine Segmentation – swishing chyme back and forth in short segments of intestine Both forms of mechanical digestion increase chances of substrate mixing with enzymes. B. chemical digestion Digestive enzymes from liver, gall bladder and pancreas are delivered into duodenum Most all-remaining chemical digestion occurs in duodenum 1. amylase (carbohydrates) à glucose 16 2. pepsin and trypsin (proteins) à amino acids 3. lipase and bile (lipids) à glycerol and fatty acids 17. ABSORPTION: small intestine Most all-remaining absorption of nutrients occurs in jejunum and ileum
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]
  • Pediatric Oral Pathology. Soft Tissue and Periodontal Conditions
    PEDIATRIC ORAL HEALTH 0031-3955100 $15.00 + .OO PEDIATRIC ORAL PATHOLOGY Soft Tissue and Periodontal Conditions Jayne E. Delaney, DDS, MSD, and Martha Ann Keels, DDS, PhD Parents often are concerned with “lumps and bumps” that appear in the mouths of children. Pediatricians should be able to distinguish the normal clinical appearance of the intraoral tissues in children from gingivitis, periodontal abnormalities, and oral lesions. Recognizing early primary tooth mobility or early primary tooth loss is critical because these dental findings may be indicative of a severe underlying medical illness. Diagnostic criteria and .treatment recommendations are reviewed for many commonly encountered oral conditions. INTRAORAL SOFT-TISSUE ABNORMALITIES Congenital Lesions Ankyloglossia Ankyloglossia, or “tongue-tied,” is a common congenital condition characterized by an abnormally short lingual frenum and the inability to extend the tongue. The frenum may lengthen with growth to produce normal function. If the extent of the ankyloglossia is severe, speech may be affected, mandating speech therapy or surgical correction. If a child is able to extend his or her tongue sufficiently far to moisten the lower lip, then a frenectomy usually is not indicated (Fig. 1). From Private Practice, Waldorf, Maryland (JED); and Department of Pediatrics, Division of Pediatric Dentistry, Duke Children’s Hospital, Duke University Medical Center, Durham, North Carolina (MAK) ~~ ~ ~ ~ ~ ~ ~ PEDIATRIC CLINICS OF NORTH AMERICA VOLUME 47 * NUMBER 5 OCTOBER 2000 1125 1126 DELANEY & KEELS Figure 1. A, Short lingual frenum in a 4-year-old child. B, Child demonstrating the ability to lick his lower lip. Developmental Lesions Geographic Tongue Benign migratory glossitis, or geographic tongue, is a common finding during routine clinical examination of children.
    [Show full text]
  • Vocabulario De Morfoloxía, Anatomía E Citoloxía Veterinaria
    Vocabulario de Morfoloxía, anatomía e citoloxía veterinaria (galego-español-inglés) Servizo de Normalización Lingüística Universidade de Santiago de Compostela COLECCIÓN VOCABULARIOS TEMÁTICOS N.º 4 SERVIZO DE NORMALIZACIÓN LINGÜÍSTICA Vocabulario de Morfoloxía, anatomía e citoloxía veterinaria (galego-español-inglés) 2008 UNIVERSIDADE DE SANTIAGO DE COMPOSTELA VOCABULARIO de morfoloxía, anatomía e citoloxía veterinaria : (galego-español- inglés) / coordinador Xusto A. Rodríguez Río, Servizo de Normalización Lingüística ; autores Matilde Lombardero Fernández ... [et al.]. – Santiago de Compostela : Universidade de Santiago de Compostela, Servizo de Publicacións e Intercambio Científico, 2008. – 369 p. ; 21 cm. – (Vocabularios temáticos ; 4). - D.L. C 2458-2008. – ISBN 978-84-9887-018-3 1.Medicina �������������������������������������������������������������������������veterinaria-Diccionarios�������������������������������������������������. 2.Galego (Lingua)-Glosarios, vocabularios, etc. políglotas. I.Lombardero Fernández, Matilde. II.Rodríguez Rio, Xusto A. coord. III. Universidade de Santiago de Compostela. Servizo de Normalización Lingüística, coord. IV.Universidade de Santiago de Compostela. Servizo de Publicacións e Intercambio Científico, ed. V.Serie. 591.4(038)=699=60=20 Coordinador Xusto A. Rodríguez Río (Área de Terminoloxía. Servizo de Normalización Lingüística. Universidade de Santiago de Compostela) Autoras/res Matilde Lombardero Fernández (doutora en Veterinaria e profesora do Departamento de Anatomía e Produción Animal.
    [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]
  • Vestibule Lingual Frenulum Tongue Hyoid Bone Trachea (A) Soft Palate
    Mouth (oral cavity) Parotid gland Tongue Sublingual gland Salivary Submandibular glands gland Esophagus Pharynx Stomach Pancreas (Spleen) Liver Gallbladder Transverse colon Duodenum Descending colon Small Jejunum Ascending colon intestine Ileum Large Cecum intestine Sigmoid colon Rectum Appendix Anus Anal canal © 2018 Pearson Education, Inc. 1 Nasopharynx Hard palate Soft palate Oral cavity Uvula Lips (labia) Palatine tonsil Vestibule Lingual tonsil Oropharynx Lingual frenulum Epiglottis Tongue Laryngopharynx Hyoid bone Esophagus Trachea (a) © 2018 Pearson Education, Inc. 2 Upper lip Gingivae Hard palate (gums) Soft palate Uvula Palatine tonsil Oropharynx Tongue (b) © 2018 Pearson Education, Inc. 3 Nasopharynx Hard palate Soft palate Oral cavity Uvula Lips (labia) Palatine tonsil Vestibule Lingual tonsil Oropharynx Lingual frenulum Epiglottis Tongue Laryngopharynx Hyoid bone Esophagus Trachea (a) © 2018 Pearson Education, Inc. 4 Visceral peritoneum Intrinsic nerve plexuses • Myenteric nerve plexus • Submucosal nerve plexus Submucosal glands Mucosa • Surface epithelium • Lamina propria • Muscle layer Submucosa Muscularis externa • Longitudinal muscle layer • Circular muscle layer Serosa (visceral peritoneum) Nerve Gland in Lumen Artery mucosa Mesentery Vein Duct oF gland Lymphoid tissue outside alimentary canal © 2018 Pearson Education, Inc. 5 Diaphragm Falciform ligament Lesser Liver omentum Spleen Pancreas Gallbladder Stomach Duodenum Visceral peritoneum Transverse colon Greater omentum Mesenteries Parietal peritoneum Small intestine Peritoneal cavity Uterus Large intestine Cecum Rectum Anus Urinary bladder (a) (b) © 2018 Pearson Education, Inc. 6 Cardia Fundus Esophagus Muscularis Serosa externa • Longitudinal layer • Circular layer • Oblique layer Body Lesser Rugae curvature of Pylorus mucosa Greater curvature Duodenum Pyloric Pyloric sphincter antrum (a) (valve) © 2018 Pearson Education, Inc. 7 Fundus Body Rugae of mucosa Pyloric Pyloric (b) sphincter antrum © 2018 Pearson Education, Inc.
    [Show full text]
  • The Digestive System Overview of the Digestive System • Organs Are Divided Into Two Groups the Alimentary Canal and Accessory
    C H A P T E R 23 The Digestive System 1 Overview of the Digestive System • Organs are divided into two groups • The alimentary canal • Mouth, pharynx, and esophagus • Stomach, small intestine, and large intestine (colon) • Accessory digestive organs • Teeth and tongue • Gallbladder, salivary glands, liver, and pancreas 2 The Alimentary Canal and Accessory Digestive Organs Mouth (oral cavity) Parotid gland Tongue Sublingual gland Salivary glands Submandibular gland Esophagus Pharynx Stomach Pancreas (Spleen) Liver Gallbladder Transverse colon Duodenum Descending colon Small intestine Jejunum Ascending colon Ileum Cecum Large intestine Sigmoid colon Rectum Anus Vermiform appendix Anal canal Figure 23.1 3 1 Digestive Processes • Ingestion • Propulsion • Mechanical digestion • Chemical digestion • Absorption • Defecation 4 Peristalsis • Major means of propulsion • Adjacent segments of the alimentary canal relax and contract Figure 23.3a 5 Segmentation • Rhythmic local contractions of the intestine • Mixes food with digestive juices Figure 23.3b 6 2 The Peritoneal Cavity and Peritoneum • Peritoneum – a serous membrane • Visceral peritoneum – surrounds digestive organs • Parietal peritoneum – lines the body wall • Peritoneal cavity – a slit-like potential space Falciform Anterior Visceral ligament peritoneum Liver Peritoneal cavity (with serous fluid) Stomach Parietal peritoneum Kidney (retroperitoneal) Wall of Posterior body trunk Figure 23.5 7 Mesenteries • Lesser omentum attaches to lesser curvature of stomach Liver Gallbladder Lesser omentum
    [Show full text]
  • Salivary Glands
    GASTROINTESTINAL SYSTEM [Anatomy and functions of salivary gland] 1 INTRODUCTION Digestive system is made up of gastrointestinal tract (GI tract) or alimentary canal and accessory organs, which help in the process of digestion and absorption. GI tract is a tubular structure extending from the mouth up to anus, with a length of about 30 feet. GI tract is formed by two types of organs: • Primary digestive organs. • Accessory digestive organs 2 Primary Digestive Organs: Primary digestive organs are the organs where actual digestion takes place. Primary digestive organs are: Mouth Pharynx Esophagus Stomach 3 Anatomy and functions of mouth: FUNCTIONAL ANATOMY OF MOUTH: Mouth is otherwise known as oral cavity or buccal cavity. It is formed by cheeks, lips and palate. It encloses the teeth, tongue and salivary glands. Mouth opens anteriorly to the exterior through lips and posteriorly through fauces into the pharynx. Digestive juice present in the mouth is saliva, which is secreted by the salivary glands. 4 ANATOMY OF MOUTH 5 FUNCTIONS OF MOUTH: Primary function of mouth is eating and it has few other important functions also. Functions of mouth include: Ingestion of food materials. Chewing the food and mixing it with saliva. Appreciation of taste of the food. Transfer of food (bolus) to the esophagus by swallowing . Role in speech . Social functions such as smiling and other expressions. 6 SALIVARY GLANDS: The saliva is secreted by three pairs of major (larger) salivary glands and some minor (small) salivary glands. Major glands are: 1. Parotid glands 2. Submaxillary or submandibular glands 3. Sublingual glands. 7 Parotid Glands: Parotid glands are the largest of all salivary glands, situated at the side of the face just below and in front of the ear.
    [Show full text]
  • 6 Physiology of the Colon : Motility
    #6 Physiology of the colon : motility Objectives : ● Parts of the Colon ● Functions of the Colon ● The physiology of Different Colon Regions ● Secretion in the Colon ● Nutrient Digestion in the Colon ● Absorption in the Colon ● Bacterial Action in the Colon ● Motility in the Colon ● Defecation Reflex Doctors’ notes Extra Important Resources: 435 Boys’ & Girls’ slides | Guyton and Hall 12th & 13th edition Editing file [email protected] 1 ﺗﻛرار ﻣن اﻟﮭﺳﺗوﻟوﺟﻲ واﻷﻧﺎﺗوﻣﻲ The large intestine ● This is the final digestive structure. ● It does not contain villi. ● By the time the digested food (chyme) reaches the large intestine, most of the nutrients have been absorbed. ● The primary role of the large intestine is to convert chyme into feces for excretion. Parts of the colon ● The colon has a length of about 150 cm. ( 1.5 meters) (one-fifth of the whole length of GIT). ● It consists of the ascending & descending colon, transverse colon, sigmoid colon, rectum and anal canal. 3 ● The transit of radiolabeled chyme through 4 the large intestine occurs in 36-48 hrs. 2 They know this how? By inserting radioactive chyme. 1 6 5 ❖ Mucous membrane of the colon ● Lacks villi and has many crypts of lieberkuhn. ● They consists of simple short glands lined by mucous-secreting goblet cells. Main colonic secretion is mucous, as the colon lacks digestive enzymes. ● The outer longitudinal muscle layer is modified to form three longitudinal bands called taenia coli visible on the outer surface.(Taenia coli: Three thickened bands of muscles.) ● Since the muscle bands are shorter than the length of the colon, the colonic wall is sacculated and forms haustra.(Haustra: Sacculation of the colon between the taenia.) Guyton corner : mucus in the large intestine protects the intestinal wall against excoriation, but in addition, it provides an adherent medium for holding fecal matter together.
    [Show full text]
  • Dynamic Colon Model (DCM): a Cine-MRI Informed Biorelevant in Vitro Model of the Human Proximal Large Intestine Characterized by Positron Imaging Techniques
    pharmaceutics Article Dynamic Colon Model (DCM): A Cine-MRI Informed Biorelevant In Vitro Model of the Human Proximal Large Intestine Characterized by Positron Imaging Techniques Konstantinos Stamatopoulos 1,* , Sharad Karandikar 2, Mark Goldstein 3, Connor O’Farrell 1, Luca Marciani 4 , Sarah Sulaiman 4 , Caroline L. Hoad 5, Mark J. H. Simmons 1 and Hannah K. Batchelor 6,7 1 School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; [email protected] (C.O.); [email protected] (M.J.H.S.) 2 Department of Surgery, University Hospitals Birmingham NHS Foundation Trust, Birmingham Heartlands Hospital, Bordesley Green East, Birmingham B9 5SS, UK; [email protected] 3 Department of Radiology, University Hospitals Birmingham NHS Foundation Trust, Birmingham Heartlands Hospital, Bordesley Green East, Birmingham B9 5SS, UK; [email protected] 4 Nottingham Digestive Diseases Centre and National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and University of Nottingham, Nottingham NG7 2UH, UK; [email protected] (L.M.); [email protected] (S.S.) 5 Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham NG7 2QX, UK; [email protected] 6 Institute of Clinical Sciences, College of Medical and Dental Sciences, Medical School Building, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; [email protected] 7 Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK * Correspondence: [email protected] or [email protected]; Tel.: +44-0121-4145-354 Received: 8 June 2020; Accepted: 10 July 2020; Published: 13 July 2020 Abstract: This work used in vivo MRI images of human colon wall motion to inform a biorelevant Dynamic Colon Model (DCM) to understand the interplay of wall motion, volume, viscosity, fluid, and particle motion within the colon lumen.
    [Show full text]
  • Motility in the Large Intestine Physiology > Digestive > Digestive
    Motility in the Large Intestine Physiology > Digestive > Digestive HAUSTRAL CONTRACTIONS (Definition): Slow, segmenting movements that further mix chyme. • About every 30 minutes. • Occur in haustra: small pouches caused by the teniae coli (longitudinal smooth muscle ribbons that run along outside the entire length of the colon). Because they are shorter than the large intestine, the large intestine tucks between the teniae and form sacs • Primarily occur in ascending and transverse colons. • Produced by contractions of smooth muscle layer Steps 1. Chyme fills a haustrum 2. Distension in the haustrum. 3. Smooth muscle layer contracts 4. Contractions move chyme into the next haustrum and subsequent haustra, where the sequence begins again. #Note that haustral contractions play a relatively minor role in propelling fecal waste through the large intestine; their main function to further mix waste. Contractions also bring chyme in close contact with the large intestine mucosal layer to maximize water and electrolyte absorption • Hasutral contractions also occur in the descending and sigmoid colon to further concentrate stored fecal waste prior to elimination. MASS MOVEMENTS (Definition): slow, but powerful contractions of the large intestine that move undigested waste to the rectum for defecation via the anus. • Much like stronger and sustained peristaltic contractions. • 3-4 times a day. • Mainly in the transverse, descending, and sigmoid colons. • Produced by circular layer (smooth muscle) contractions Steps 1. Undigested waste in the transverse colon. 2. Triggered by the gastrocolic reflex (initiated following ingestion of a meal when food enters the stomach causes its distension) 3. Circular layer contracts in the transverse colon 4. Contractions move waste towards the rectum.
    [Show full text]
  • Anatomy of the Digestive System
    The Digestive System Anatomy of the Digestive System We need food for cellular utilization: organs of digestive system form essentially a long !nutrients as building blocks for synthesis continuous tube open at both ends !sugars, etc to break down for energy ! alimentary canal (gastrointestinal tract) most food that we eat cannot be directly used by the mouth!pharynx!esophagus!stomach! body small intestine!large intestine !too large and complex to be absorbed attached to this tube are assorted accessory organs and structures that aid in the digestive processes !chemical composition must be modified to be useable by cells salivary glands teeth digestive system functions to altered the chemical and liver physical composition of food so that it can be gall bladder absorbed and used by the body; ie pancreas mesenteries Functions of Digestive System: The GI tract (digestive system) is located mainly in 1. physical and chemical digestion abdominopelvic cavity 2. absorption surrounded by serous membrane = visceral peritoneum 3. collect & eliminate nonuseable components of food this serous membrane is continuous with parietal peritoneum and extends between digestive organs as mesenteries ! hold organs in place, prevent tangling Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 1 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 2 is suspended from rear of soft palate The wall of the alimentary canal consists of 4 layers: blocks nasal passages when swallowing outer serosa: tongue visceral peritoneum,
    [Show full text]