Chapter 23 Study Questions
Answer the following…..
1. Describe the overall function of the digestive system, and differentiate the organs of the alimentary canal from the accessory organs of digestion.
To stay healthy and functional, the body needs nutrients that one gets from food. The nutrients are included proteins, vitamins, carbohydrates, and fats. The digestive system absorbs and breaks down the nutrients to use for certain important things like repairing the body cells, growth, and energy.
Alimentary canal organs are those organs that the body requires to travel the liquid and food through when they are swallowed, absorbed, digested, and leave the body. The alimentary canal organ is included the pharynx, mouth, esophagus, small intestine, stomach, large intestine, anus, and rectum. The accessory organs of digestion are included with tongue, teeth, and glandular organs like salivary glands, pancreas, gallbladder, and liver. It functions to provide digestion, mechanical processing, absorption of food, and secretion of water.
2. Explain the location and function of the peritoneum and peritoneal cavity. Define mesentery.
The peritoneum lines the abdominal cavity walls and it is a serous membrane. It lies on the pelvic and abdominal organs. The peritoneal cavity is in between the two layers of visceral and parietal layers. The function of the peritoneum is to protect and support the abdominopelvic organs. It also connects the organ. It maintains the organ position by ligament suspending.
The mesentery is the peritoneum folds that suspend the organs from the abdominal wall situated at the posterior. A peritoneal fold is created by the projection of the organ into the peritoneum which wraps the organ and extends it back to the abdominal wall. These double layers of the peritoneum are known as mesentery.
3. Differentiate intraperitoneal and secondarily retroperitoneal digestive organs. Name the mesenteries associated with the intraperitoneal digestive organs.
The intraperitoneal digestive organs are included with the spleen, stomach, liver, jejunum, the fourth and first part of the duodenum, ileum, transverse and sigmoid colon. Whereas the Retroperitoneal organ is situated behind the peritoneum’s posterior sheath that is included the aorta, second and third part of the duodenum, esophagus, ascending and descending colon, kidneys, pancreas, and adrenal glands.
The mesenteries associated with intraperitoneal digestive organs are small intestine mesentery or mesentery proper, transverse mesocolon, and sigmoid mesocolon.
4. List the major processes that occur during digestion.
The major processes of the digestive system are included ingestion, mechanical breakdown, propulsion, absorption, digestion, and defecation. The first process is ingestion which is the entry of food into the alimentary canal with the help of the mouth. Here the food is chewed and digested with saliva. After that, the food passes through the digestive tract which is known as propulsion and includes swallowing and peristalsis. The process of digestion is included in both chemical and mechanical processes. The chemical nature of the food is not changed by the mechanical digestion process. The digestive materials are broken down from complex food molecules to chemical compounds with the help of chemical digestion. The broken-down food enters the bloodstream with the help of the absorption process.
5. Describe the four layers of the wall of the alimentary canal.
The four walls or layers of the alimentary canal are the mucosa, submucosa, muscular layers, and serous layer or serosa. The innermost layer of the wall which lines the digestive tract lumen is known as mucosa. It consists of epithelium and lamina propria. A thick layer of connective tissues that are loose and surrounds the mucosa is known as submucosa. The muscle layers are arranged into two layers the outer longitudinal layer and the inner circular layer. The serosa is situated below the diaphragm.
6. Describe the structure and appearance of smooth muscle fibers, and describe how smooth muscle cells are joined together to form a sheet-like tissue.
The smooth muscle fibers are involuntary muscles. There are no cross stripes under the microscopic magnification of this muscle. It is consisting of various narrow cells spindle-shaped with a centrally located, single nucleus. The contraction of smooth muscle tissue is slow and automatic, unlike the striated muscle.
They are composed of strands and sheets of smooth muscle cells that contain myosin and actin fibers which run into the cells and support the framework of certain other proteins.
7. Discuss the different stimuli that can initiate the contraction of smooth muscle tissue.
The action potential of smooth muscles is unique in the acts of membrane potential that modulate and initiate the contraction. The membrane response can be stimulated by various factors that are included hormonal factors, mechanical stimulation, and circulating hormones. It is also stimulated by catecholamines that are released by the nerves in the muscles.
8. Describe the innervation of the muscle and glands in the alimentary canal.
The glands associated with the alimentary canal are the liver, pancreas, and salivary glands. The glands are also included with gastric glands that are situated in the stomach. There are other glands also that are situated in bile ducts and gallbladder. The alimentary canal wall is associated with smooth muscle layers which are controlled by the autonomic nervous system. The contraction and relaxation of the muscles in an alternative way is known as peristalsis.
9. Describe the gross and microscopic anatomy and the basic functions of the mouth, teeth, tongue, salivary glands, and pharynx.
Mouth: It is the squamous epithelial that is stratified and lined with mucosa bound by the lips, tongue, palate, and cheeks. The food passes through the GI tract when it is ingested by the mouth. The food is pushed by the tongue to the throat when it is swallowed. There lies a small tissue flap that is known as the epiglottis that folds over the windpipe which helps in the prevention of choking.
Teeth: The contents of teeth are dentin, cementum, pulp tissue, and enamel. The part of the teeth that are in front of the oral cavity is known as the dental crown. Mastication is the primary function of teeth. Mastication is included mixing, cutting, and grinding the food that the body ingests. The oropharynx and tongue shape the masticated food into a bolus that one can swallow.
Tongue: It consists of striated muscle which occupies the mouth floor. The mucosal surface of the dorsal consists of the epithelium of stratified squamous that have certain taste buds and papillae. The voluntary muscle of the tongue is attached to the floor with the help of a fold named the frenulum. The tongue facilitates food movement during swallowing and mastication. The tongue also helps in speech and taste.
Salivary gland: The adult salivary gland consists of secretory glandular tissue, parenchyma, and stroma that support the connective tissue. The parenchyma consists of secretory endpieces. It plays an important functional role due to its secretion of saliva. The saliva helps in the moistening of food so that we can swallow it easily. The gland also secrets enzymes named amylase that help in the breaking down of starches.
Pharynx: It is commonly named throat which is a funnel-shaped, muscular passageway inside the human body. The nose and mouth are connected with the esophagus and larynx with the help of the pharynx. It carries the food, fluid, and air down from the mouth and nose.
10. Describe the gross and microscopic anatomy of the esophagus.
Oesophagus is a tube of muscles that is approximately twenty-five centimeters long. It is extended from the hypopharynx to the stomach. The esophagus is situated at the posterior side of the trachea and heart. It passes through the hiatus and mediastinum which is the opening of the diaphragm which is stretched from the thoracic to the cavity of the abdomen.
11. Describe the gross and microscopic anatomy of the stomach.
There are three layers in the stomach, the first layer is the longitudinal outer layer, the second layer is the circular middle layer and the third layer is the oblique inner layer. The inner lining of the wall of the stomach is known as mucosa. The mucosa consists of lamina propia, muscular mucosa, and epithelium.
12. Relate the histological modifications in the wall of the stomach to the digestive activities that occur there.
It is the main part of the tract of the gastrointestinal which is situated between the duodenum and esophagus. The function of the stomach is to mix food with stomach acid and break it down into small particles. There is a third layer obliquely oriented in the muscular externa of the stomach. This modification of the stomach wall allows the stomach to mix, churn, and pummelation of food. It helps the food to break down physically into smaller fragments.
13. Describe the gross and microscopic anatomy of the small and large intestines.
The longest part of the alimentary canal is the small intestine. The subdivision of the small intestine is the ileum, jejunum, and duodenum. There is a modification for the wall structure and nutrient absorption through the small intestine. The modification is found in microscopic anatomy.
Several subdivisions in the large intestine are included with the colon, appendix, cecum, anal canal, and rectum. The large intestine is served by the inferior and superior blood vessels. The organ is intervened by certain nerves, parasympathetic and sympathetic fibers. Defecation happens through the contraction of rectal wall muscles. The lack of villi is revealed by the microscopic anatomy.
14. Relate the individual histological modifications in the wall of the intestines to the digestive functions of these regions.
The modification of the intestine wall is included a six hundredfold increase in the surface area of the small intestine. The increase is included in microvilli, villi, and circular folds. The adaptation is abundant in almost two-thirds of the small intestine where maximum absorption happens. Four main layers in the wall of the small intestine are included epithelium, mucosa, lamina propia, and muscularis mucosa.
15. Describe the gross and microscopic anatomy and functions of the liver, gallbladder, and pancreas.
Liver: The largest gland in the body is the liver. It performs various essential functions. It involves digestion by producing bile. There are right and left lobes present in the liver which is the gross feature of the liver. The liver is also included with falciform ligament and caudate lobes. Hepatocytes are the functional cells of the liver. The classic liver lobules are revealed by microscopic anatomy.
Gallbladder: It concentrates and stores the bile that is produced by the liver. The bile duct is formed by joining the hepatic duct and the cystic duct. It releases the bile into the duodenum.
Pancreas: It is both an exocrine and endocrine gland. The digestive function of the pancreas is included with the production of enzymes that helps in the digestion of small intestine food.
16. Describe some disorders of the digestive system.
Several disorders are included in the digestive system. The digestive system disorder is included peptic ulcers, viral hepatitis, intestinal obstruction, inflammatory bowel disease, and cystic fibrosis. The additional disorders that have been discussed in the digestive system are gum disease, peritonitis, hiatal hernia, hemorrhoids, diverticulosis, appendicitis, gastroesophageal reflux disease, pancreatitis, liver cirrhosis, and gallstones.
17. Explain how the digestive organs develop in the embryo and define the foregut, midgut, and hindgut.
The primitive gut of week three is a tube of endoderm that is covered by splanchnic mesoderm. There are three divisions of the embryonic gut are included with hindgut, foregut, and midgut. It forms various regions of the system of digestion.
Foregut: It is the alimentary canal’s anterior part that extends from the mouth to the duodenum which is the bile duct entrance. The foregut is attached to the walls of the abdomen with the help of the mesentery that is beyond the stomach.
Midgut: Maximum of the intestine develops from the midgut portion of the embryo. It is known as the midgut loop when it bends around the mesenteric superior artery.
Hindgut: It is the alimentary canal’s posterior part. It is included with one-third of the distal transverse colon, descending colon, anorectal junction, and sigmoid colon.
