It has three parts- Caecum, Colon, and Rectum g. Stomach. lamina propria. The third layer of the alimentary canal is the muscalaris (also called the muscularis externa). (5 Points) Serosa - The outer layer allows fluids to escape, keeping the outer surface wet and allowing organs to slide past one another during digestion and movement. Within these folds are blood vessels, lymphatic vessels, and nerves that innervate the organs with which they are in contact, supplying their adjacent organs. Legal. It plays a primary role in the digestion of food and is also called the digestive tract. Describe the development of the body cavities 3. Identify the structural characteristic of smooth muscle fibers. 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. Food, mucus, and digestive juices pass through the lumen, and the mucosa comes in direct contact with digested food (chyme). The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. This is the . It includes blood and lymphatic vessels (which transport absorbed nutrients), and a scattering of submucosal glands that release digestive secretions. In the small intestine, the epithelium (particularly the ileum) is specialized for absorption, with villi and microvilli increasing surface area. Lipids are absorbed via lacteals, tiny structures of the lymphatic system. 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. Mucosa is the moist innermost layer; it lines the cavity of the organ. Each layer has different structures and functions. 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 100 million motor, sensory, and interneurons (unique to this system compared to all other parts of the peripheral nervous system). The mucosa is the innermost layer, and functions in absorption and secretion. The mucosae (singular: mucosa) are highly specialized in each organ of the gastrointestinal tract in order to deal with different digestive tract conditions. The gallbladder releases bile, which is responsible as a buffer and emulsification, while the pancreas provides enzymes that break down starches, lipids, nucleic acids & proteins. Consider how understanding the function of the Gastro-intestinal (GI) tract is useful in the care of patients with surgical changes for example the formation of an ileostomy. Accessory digestive organs, despite their name, are critical to the function of the digestive system. Digestive mucosa is made up of three sublayers: (1) a lining epithelium, (2) a lamina propria, and (3) a musclularis mucosae. clinicalanatomy.com/mtd/382-layers-of-the-gi-tract, Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36. The GI tract contains four layers: the innermost layer is the mucosa, underneath this is the submucosa, followed by the muscularis propria and finally, the outermost layer - the adventitia. Each accessory digestive organ aids in the breakdown of food (Figure 23.1.2). By the end of this section, you will be able to: The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. The wall of the digestive tract has four layers or tunics: Mucosa Submucosa Muscular layer Serous layer or serosa The mucosa, or mucous membrane layer, is the innermost tunic of the wall. They transport the protein and carbohydrate nutrients absorbed by mucosal cells after food is digested in the lumen. The gastrointestinal wall is inflamed in a number of conditions. 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 (Figure 23.1.1). Ulcers that affect the tract include peptic ulcers and perforated ulcer is one that has eroded completely through the layers. As an Amazon Associate we earn from qualifying purchases. 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. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix. There are 4 layers in gastrointestinal tract: from inside to outside these are mucosa, submucosa, muscular layer and serosa. Muscularis mucosaThis thin layer of smooth muscle is in a constant state of tension, pulling the mucosa of the stomach and small intestine into undulating folds. Name the structure that forms the roof of the mouth. The mesocolon is the portion of the mesentery serving the colon and is considered part of the larger mesentery organ. The digestive tract wall initiates from the esophagus and ends at the rectum. Dec 13, 2022 OpenStax. Inflammation of the peritoneum is called peritonitis. Two B. The serosa is a serous membrane that covers the muscularis externa of the digestive tract in the peritoneal cavity. Extrinsic innervations of the alimentary canal are provided by the autonomic nervous system, which includes both sympathetic and parasympathetic nerves. 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. There are two types of epithelial membranes, mucous membrane and serous membrane. HV Carter was born in Yorkshire in 1831. Muscularis externa. Thus, the location of these organs is described as retroperitoneal. EpitheliumIn the mouth, pharynx, esophagus, and anal canal, the epithelium is primarily a non-keratinized, stratified squamous epithelium. The GI tract is composed of four layers. Only through the process of absorption do the nutrients in food enter into and nourish the bodys inner space.. From the inside out they are called: mucosa, submucosa, muscularis, and serosa. Even after development is complete, they maintain a connection to the gut by way of ducts. The layers are discussed below, from the inside lining of the tract to the outside lining: The mucosa is a mucous membrane that lines the inside of the digestive tract from mouth to anus. The parietal peritoneum lines the abdominopelvic cavity (abdominal and pelvic cavities). 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. Support/stabilize the organs of the abdominopelvic cavity and route for blood. are licensed under a, Structural Organization of the Human Body, Elements and Atoms: The Building Blocks of Matter, Inorganic Compounds Essential to Human Functioning, Organic Compounds Essential to Human Functioning, Nervous Tissue Mediates Perception and Response, Diseases, Disorders, and Injuries of the Integumentary System, Exercise, Nutrition, Hormones, and Bone Tissue, Calcium Homeostasis: Interactions of the Skeletal System and Other Organ Systems, Embryonic Development of the Axial Skeleton, Development and Regeneration of Muscle Tissue, Interactions of Skeletal Muscles, Their Fascicle Arrangement, and Their Lever Systems, Axial Muscles of the Head, Neck, and Back, Axial Muscles of the Abdominal Wall, and Thorax, Muscles of the Pectoral Girdle and Upper Limbs, Appendicular Muscles of the Pelvic Girdle and Lower Limbs, Basic Structure and Function of the Nervous System, Circulation and the Central Nervous System, Divisions of the Autonomic Nervous System, Organs with Secondary Endocrine Functions, Development and Aging of the Endocrine System, The Cardiovascular System: Blood Vessels and Circulation, Blood Flow, Blood Pressure, and Resistance, Homeostatic Regulation of the Vascular System, Development of Blood Vessels and Fetal Circulation, Anatomy of the Lymphatic and Immune Systems, Barrier Defenses and the Innate Immune Response, The Adaptive Immune Response: T lymphocytes and Their Functional Types, The Adaptive Immune Response: B-lymphocytes and Antibodies, Diseases Associated with Depressed or Overactive Immune Responses, Energy, Maintenance, and Environmental Exchange, Organs and Structures of the Respiratory System, Embryonic Development of the Respiratory System, Digestive System Processes and Regulation, Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder, Chemical Digestion and Absorption: A Closer Look, Regulation of Fluid Volume and Composition, Fluid, Electrolyte, and Acid-Base Balance, Human Development and the Continuity of Life, Anatomy and Physiology of the Testicular Reproductive System, Anatomy and Physiology of the Ovarian Reproductive System, Development of the Male and Female Reproductive Systems, Changes During Pregnancy, Labor, and Birth, Adjustments of the Infant at Birth and Postnatal Stages. 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 100 million motor, sensory, and interneurons (unique to this system compared to all other parts of the peripheral nervous system). Layers of the Stomach The stomach is a very complex organ. The epithelium of the mucosa is particularly specialized, depending on the portion of the digestive system. A broad layer of dense connective tissue, it connects the overlying mucosa to the underlying muscularis. These intestinal veins, constituting the hepatic portal system, are unique; they do not return blood directly to the heart. epithelium. Muscularis: voluntary swallowing 4. The structure of these layers varies, in different regions of the digestive system, depending on their function. The GI tract is composed of four layers. Along the way, note how the food changes consistency and form. Layers of GI tissue: Note the mucosa, located at the innermost layer. The stomach acids and enzymes work to break down food which is then released into the small intestine. Aggressive surgery, improvements in anesthesia safety, the advance of critical care expertise, and antibiotics have greatly improved the mortality rate from this condition. Goblet cells secrete mucus that protects the epithelium from digestion, and endocrine cells secrete hormones into the blood. Citation: Nigam Y et al (2019) Gastrointestinal tract 4: anatomy and role of the jejunum and ileum. Lamina propriaIn 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. Below this point, the alimentary canal is supplied with blood by arteries branching from the abdominal aorta. Our mission is to improve educational access and learning for everyone. If $V$ equals a constant throughout a given region of space what can you say about $\mathrm{E}$ in that region? Crown, neck, and root. The lamina propria also contains the mucosaassociated lymphoid tissue (MALT), nodules of lymphatic tissue bearing lymphocytes and macrophages that protect the GI tract wall from bacteria and other pathogens that may be mixed with food. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . e. SMALL INTESTINE - It is the longest part of the alimentary canal and comprises three parts- Duodenum, Jejunum, and Ileum. The main function of the organs of the alimentary canal is to nourish the body by digesting food and absorbing released nutrients. Muscularis: composed of two layers of muscle tissue. The third layer with high autonomy is defined as semiautonomous navigation, transferring the decision priority to the system. There are four layers making up our atmosphere: The troposphere, stratosphere, mesosphere and thermosphere. Incisors, cuspids (canines), bicuspids (premolars), and molars. An Introduction to the Human Body, Chapter 2. The epithelial membrane consists of a layer of epithelial tissue and has underlying connective tissue. From the inside out they are called the mucosa, submucosa, muscularis externa, and serosa. An ulcer is something that's eroded through the epithelium of the wall. Helping them along the way are the pancreas, gall bladder and liver. The system is much more complex. The basic two-layer structure found in the small intestine is modified in the organs proximal and distal to it. These intestinal veins, constituting the hepatic portal system, are unique in that they do not return blood directly to the heart. Name the major functions of the large intestine. The hollow organs that make up the gastrointestinal tract include the mouth, oesophagus, stomach, small intestine, cecum, colon (large intestine), rectum and anal canal. There are goblet cells present, which secrete mucus. The peritoneal cavity is the space bounded by the visceral and parietal peritoneal surfaces. It includes blood and lymphatic vessels (which transport absorbed nutrients), and a scattering of submucosal glands that release digestive secretions. Part B: First, describe the four major layers of the GI tract that are found from esophagus to anus. supports avascular mucosal epithelium. The secretions of the associated glandular organs, such as the salivary glands, pancreas, liver, and gall bladder, aid the GI tract in accomplishing these functions. Notice that the epithelium is in direct contact with the lumen, the space inside the alimentary canal. It consists of areolar connective tissue containing blood vessels, lymphatic vessels, and nerve fibers. The Cardiovascular System: Blood Vessels and Circulation, Chapter 21. Quiz: Function of the Digestive System. 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. The Lymphatic and Immune System, Chapter 26. In contrast, parasympathetic activation (the rest-and-digest response) increases GI secretion and motility by stimulating neurons of the enteric nervous system. These tissues serve to hold the alimentary canal in place near the ventral surface of the vertebral column. How does this change in consistency facilitate your gaining nutrients from food? The mucosa, composed of simple epithelium cells, is the innermost layer of the gastrointestinal (GI) tract. 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. 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. It is made up of three layers: the epithelium, lamina propria, and muscularis mucosae. In the stomach. Arteries supply the digestive organs with oxygen and processed nutrients, and veins drain the digestive tract. Its functions are to mix food with stomach acid and break food down into smaller particles using chemical and mechanical digestion. Explain how the displacement current maintains the continuity of current in a circuit containing a capacitor. These tissues serve to hold the alimentary canal in place near the ventral surface of the vertebral column. The serosa is the portion of the alimentary canal superficial to the muscularis. An important one of these folds is the mesentery which attaches the small intestine to the body wall allowing for blood vessels, nerves, and lymphatic vessels to have a secure structure to travel through on their way to and from the small intestine. The gastrointestinal tract is a one-of-a-kind system. 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. Muscularis: This is composed of smooth muscle and is found in two regions as inner . 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. Lamina propriaIn 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. Going from the inside out, these are: mucosa; submucosa; muscularis externa; adventitia or serosa; Figure 2: Schematic drawing of the digestive tract layers Mucosa. 1.2 Structural Organization of the Human Body, 2.1 Elements and Atoms: The Building Blocks of Matter, 2.4 Inorganic Compounds Essential to Human Functioning, 2.5 Organic Compounds Essential to Human Functioning, 3.2 The Cytoplasm and Cellular Organelles, 4.3 Connective Tissue Supports and Protects, 5.3 Functions of the Integumentary System, 5.4 Diseases, Disorders, and Injuries of the Integumentary System, 6.6 Exercise, Nutrition, Hormones, and Bone Tissue, 6.7 Calcium Homeostasis: Interactions of the Skeletal System and Other Organ Systems, 7.6 Embryonic Development of the Axial Skeleton, 8.5 Development of the Appendicular Skeleton, 10.3 Muscle Fiber Excitation, Contraction, and Relaxation, 10.4 Nervous System Control of Muscle Tension, 10.8 Development and Regeneration of Muscle Tissue, 11.1 Describe the roles of agonists, antagonists and synergists, 11.2 Explain the organization of muscle fascicles and their role in generating force, 11.3 Explain the criteria used to name skeletal muscles, 11.4 Axial Muscles of the Head Neck and Back, 11.5 Axial muscles of the abdominal wall and thorax, 11.6 Muscles of the Pectoral Girdle and Upper Limbs, 11.7 Appendicular Muscles of the Pelvic Girdle and Lower Limbs, 12.1 Structure and Function of the Nervous System, 13.4 Relationship of the PNS to the Spinal Cord of the CNS, 13.6 Testing the Spinal Nerves (Sensory and Motor Exams), 14.2 Blood Flow the meninges and Cerebrospinal Fluid Production and Circulation, 16.1 Divisions of the Autonomic Nervous System, 16.4 Drugs that Affect the Autonomic System, 17.3 The Pituitary Gland and Hypothalamus, 17.10 Organs with Secondary Endocrine Functions, 17.11 Development and Aging of the Endocrine System, 19.2 Cardiac Muscle and Electrical Activity, 20.1 Structure and Function of Blood Vessels, 20.2 Blood Flow, Blood Pressure, and Resistance, 20.4 Homeostatic Regulation of the Vascular System, 20.6 Development of Blood Vessels and Fetal Circulation, 21.1 Anatomy of the Lymphatic and Immune Systems, 21.2 Barrier Defenses and the Innate Immune Response, 21.3 The Adaptive Immune Response: T lymphocytes and Their Functional Types, 21.4 The Adaptive Immune Response: B-lymphocytes and Antibodies, 21.5 The Immune Response against Pathogens, 21.6 Diseases Associated with Depressed or Overactive Immune Responses, 21.7 Transplantation and Cancer Immunology, 22.1 Organs and Structures of the Respiratory System, 22.6 Modifications in Respiratory Functions, 22.7 Embryonic Development of the Respiratory System, 23.2 Digestive System Processes and Regulation, 23.5 Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder, 23.7 Chemical Digestion and Absorption: A Closer Look, 25.1 Internal and External Anatomy of the Kidney, 25.2 Microscopic Anatomy of the Kidney: Anatomy of the Nephron, 25.3 Physiology of Urine Formation: Overview, 25.4 Physiology of Urine Formation: Glomerular Filtration, 25.5 Physiology of Urine Formation: Tubular Reabsorption and Secretion, 25.6 Physiology of Urine Formation: Medullary Concentration Gradient, 25.7 Physiology of Urine Formation: Regulation of Fluid Volume and Composition, 27.3 Physiology of the Female Sexual System, 27.4 Physiology of the Male Sexual System, 28.4 Maternal Changes During Pregnancy, Labor, and Birth, 28.5 Adjustments of the Infant at Birth and Postnatal Stages. Epithelial cells have a very brief lifespan, averaging from only a couple of days (in the mouth) to about a week (in the gut). The mucosa consists of the epitheliumitself and also the supporting loose connective tissue, called lamina propria, immediately beneath the epithelium. 1999-2023, Rice University. The following is a description of the various types of serosae associated with the digestive system: The adventitia is the serous membrane that lines the muscularis externa of the oral cavity, pharynx, esophagus, and rectum. Large intestine. These lymphocyte clusters are particularly substantial in the distal ileum where they are known as Peyers patches. By the end of this section, you will be able to: The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. It can also determine the presence of small or large bowel obstruction, air fluid levels, pneumobilia or the presence of intramural air in bowel loops as well as in the gall bladder or urinary bladder. The alimentary canal is the pathway (a tube-like structure) that starts from the mouth and ends in the anus. The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo Removing #book# The interrelationship of the digestive and endocrine systems is also critical. Each layer has different tissues and functions. A few milliliters of watery fluid act as a lubricant to minimize friction between the serosal surfaces of the peritoneum. The digestive tract, from the esophagus to the anus, is characterized by a wall with four layers, or tunics. The contractions of these layers promote mechanical digestion, expose more of the food to digestive chemicals, and move the food along the canal. The thin filaments are anchored to dense bodies. Since it lacks sarcomeres, it is nonstriated. 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. Composed of 3 layers (epithelial, areolar connective, smooth muscle) Contains lymph tissue. This season, you are right on trend if you explore the depths and layers of this often overlooked color. A team of researchers from the Institute of Science and Technology Austria (ISTA) and the Weizmann Institute of Science has studied what happens when they layer four sheets of it on top of each other and how this can lead to new forms of exotic superconductivity. The accessory digestive structures include the teeth, tongue, salivary glands, liver, pancreas, and gallbladder. 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. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelopes the abdominal organs (Figure 23.1.3). Mucosa (adjacent to the lumen), submucosa, muscularis externa and serosa. Which is more efficient in propelling intestinal contents along the digestive tract: peristalsis or segmentation? Mucosa - 2. Fluid, Electrolyte, and Acid-Base Balance, Lindsay M. Biga, Sierra Dawson, Amy Harwell, Robin Hopkins, Joel Kaufmann, Mike LeMaster, Philip Matern, Katie Morrison-Graham, Devon Quick & Jon Runyeon, Next: 23.2 Digestive System Processes and Regulation, Creative Commons Attribution-ShareAlike 4.0 International License, Blood supplies digestive organs with oxygen and processed nutrients; absorption of nutrients, Endocrine hormones help regulate secretion in digestive glands and accessory organs, Skin helps protect digestive organs and synthesizes vitamin D for calcium absorption, Mucosa-associated lymphoid tissue and other lymphatic tissue defend against entry of pathogens; lacteals absorb lipids; and lymphatic vessels transport lipids to bloodstream, Skeletal muscles support and protect abdominal organs, Sensory and motor neurons help regulate secretions and muscle contractions in the digestive tract, Respiratory organs provide oxygen and remove carbon dioxide, Bones help protect and support digestive organs, Kidneys convert vitamin D into its active form, allowing calcium absorption in the small intestine, Apron-like structure that lies superficial to the small intestine and transverse colon; a site of fat deposition in people who are overweight, Anchors the liver to the anterior abdominal wall and inferior border of the diaphragm, Suspends the stomach from the inferior border of the liver; provides a pathway for structures connecting to the liver, Vertical band of tissue anterior to the lumbar vertebrae and anchoring all of the small intestine except the initial portion (the duodenum), Attaches two portions of the large intestine (the transverse and sigmoid colon) to the posterior abdominal wall, Describe the organs of the alimentary canal from proximal to distal, and briefly state their function, Identify the accessory digestive organs and briefly state their function, Describe the four fundamental tissue layers of the alimentary canal and the function of each layer, Contrast the contributions of the enteric and autonomic nervous systems to digestive system functioning, Explain how the peritoneum anchors the digestive organs. Name the four layers of the digestive tract from superficial to deep. It is composed of epithelium cells and a thin connective tissue. This process of rapid renewal helps preserve the health of the alimentary canal, despite the wear and tear resulting from continued contact with foodstuffs. are not subject to the Creative Commons license and may not be reproduced without the prior and express written Compare the submucosal plexus with the deeper myenteric plexus. To appreciate just how demanding the digestive process is on the cardiovascular system, consider that while you are resting and digesting, about one-fourth of the blood pumped with each heartbeat enters arteries serving the intestines. 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. Mucous membrane: It is also known as mucosa. Hemorrhagic peritonitis occurs after a ruptured tubal pregnancy or traumatic injury to the liver or spleen fills the peritoneal cavity with blood. For example, when an ulcer perforates the stomach wall, gastric juices spill into the peritoneal cavity. The mucosa surrounds the lumen, or open space within the digestive tube. A) Mucosa- The mucosa, or innermost of the GI tract, is a mucous membrane. typically a simple cuboidal or a simple columnar epithelium. Each layer has different tissues and functions. Esophagus. The five major peritoneal folds are described in Table 23.2. This venous network takes the blood into the liver where the nutrients are either processed or stored for later use. The Immune System and Other Body Defenses, Chemical Reactions in Metabolic Processes, Quiz: Chemical Reactions in Metabolic Processes, Connective Tissue Associated with Muscle Tissue, Quiz: Connective Tissue Associated with Muscle Tissue, Quiz: Structure of Cardiac and Smooth Muscle, Muscle Size and Arrangement of Muscle Fascicles, Quiz: Muscle Size and Arrangement of Muscle Fascicles, Quiz: The Ventricles and Cerebrospinal Fluid, Quiz: The Hypothalamus and Pituitary Glands, Quiz: Functions of the Cardiovascular System, Quiz: Specific Defense (The Immune System), Humoral and Cell-Mediated Immune Responses, Quiz: Humoral and Cell-Mediated Immune Responses, Quiz: Structure of the Respiratory System, Quiz: Structure of the Digestive Tract Wall, Online Quizzes for CliffsNotes Anatomy and Physiology QuickReview, 2nd Edition. The visceral peritoneum includes multiple large folds that envelope various abdominal organs, holding them to the dorsal surface of the body wall. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelopes the abdominal organs (Figure 23.4).