Digestive System of Vertebrates PDF

DIGESTIVE SYSTEM OF VERTEBRATES The digestive systems of amphibians are relatively simple, The Digestive System with a stomach and short intestines. The c...

DIGESTIVE SYSTEM OF VERTEBRATES The digestive systems of amphibians are relatively simple, The Digestive System with a stomach and short intestines. The comparative anatomy of Larval amphibians consume small digestive systems in vertebrates is a prey and aquatic plants, while adult testament to the incredible diversity amphibians, transitioning to a more and adaptability found in the animal terrestrial diet, develop longer kingdom. From the simplistic yet intestines to aid in nutrient efficient systems of fish to the highly absorption specialized structures of mammals, each group has evolved unique Reptiles digestive adaptations to suit their Reptiles exhibit a diverse range of dietary needs and environmental digestive adaptations across their niches. In this comprehensive various orders. exploration, we delve into the complex world of vertebrate Snakes, with their elongated bodies, digestive systems, highlighting their have highly specialized digestive varied structures, functions, and systems to accommodate large prey. evolutionary adaptations. Their elongated intestines allow for efficient nutrient extraction. Fish Crocodilians possess powerful As the oldest group of vertebrates, stomachs capable of digesting fish boast relatively straightforward bones and tough tissues. digestive systems. Consisting of a mouth, esophagus, stomach, and Many reptiles exhibit fermentation intestine, the system lacks a true processes in specialized regions of stomach in many species. their digestive tracts aiding in the breakdown of complex plant Digestion primarily occurs in the materials. intestine, where nutrients are absorbed. Birds The diets of fish vary widely, from Birds have evolved some of the carnivorous to herbivorous, most efficient and specialized influencing the length and function of digestive systems among their digestive tracts. vertebrates. Some fish, like cartilaginous species, Their digestive tract includes a crop possess specialized structures such for food storage and a muscular as the spiral valve, enhancing gizzard for mechanical digestion. nutrient absorption. Lacking teeth, birds use their Amphibians gizzard to grind food with swallowed stones. Amphibians undergo a metamorphosis from aquatic larvae The crop and proventriculus to terrestrial adults, shaping their secrete digestive enzymes while the digestive adaptations. highly developed small intestine maximizes nutrient absorption.  Gastroliths – tiny pebbles (stones) you eat and the liquids you drink in order to stay healthy and function Mammals properly. Nutrients include Mammals, including humans, exhibit carbohydrates, proteins, fats, intricate digestive systems. vitamins, minerals and water. Your digestive system breaks down and They possess specialized structures absorbs nutrients from the food and such as stomach with multiple liquids you consume to use for compartments, exemplified by the important things like energy, growth rumen in ruminants. and repairing cells. Mammals have efficient teeth for What organs make up the digestive grinding and chewing, and a lengthy system? small intestine for nutrient absorption. Herbivorous mammals The digestive system includes the have evolved complex fermentation mouth, pharynx (throat), esophagus, chambers, allowing them to extract stomach, small intestine, large nutrients from plant materials intestine, rectum, and anus. through microbial action. It also includes the salivary glands, What is a Digestive System? liver, gallbladder, and pancreas, which make digestive juices and Digestive system is a network of enzymes that help the body digest organs that help you digest and food and liquids. absorb nutrition from your food. It includes your gastrointestinal (GI) Mouth tract and your biliary system. The mouth is an oval-shaped cavity The Gl tract is a series of hollow inside the skull also known as the organs that are all connected to oral/buccal cavity. The two main each other, leading from your mouth functions of the mouth are eating to the anus. and speaking, and is essential for the formation of speech and normal The biliary system is a network of respiration. three organs that deliver bile and enzymes through to your Gl tract Parts of the mouth include the lips, your bile ducts. vestibule, mouth cavity, gums, teeth, hard and soft palate, tongue and The Gastrointestinal Tract salivary glands. The organs that make up your GI The teeth, which are the chief tract, in the order that they are structures of the oral cavity, tear and connected, include your mouth, grind ingested food into pieces small esophagus, stomach, small enough for digestion. intestine, large intestine and anus. Esophagus Why is digestion important? Function: to transport food entering the mouth through the throat and Digestion is important because your into the stomach. body needs nutrients from the food  Food entering the pharynx relaxes with digestive juices from the the upper esophageal sphincter pancreas and liver. and passes through it into the Pancreas esophagus; the sphincter immediately closes to prevent food The pancreas secretes digestive from backing up. enzymes into the duodenum that break down protein, fats and Contractions of the muscles in the carbohydrates. esophageal wall (peristalsis) move the food down the esophageal tube. The pancreas also makes insulin, passing it directly into the The food is pushed ahead of the bloodstream. peristaltic wave until it reaches the lower esophageal sphincter which Insulin is the chief hormone in your opens, allowing food to pass into the body for metabolizing sugar. stomach, and then closes to prevent the stomach's gastric juices and Liver contents from entering the The liver has many functions, but its esophagus. main job within the digestive system Stomach is to process the nutrients absorbed from the small intestine. The stomach is a hollow organ, or "container," that holds food while it is Bile from the liver secreted into the being mixed with stomach enzymes. small intestine also plays an important role in digesting fat and These enzymes continue the some vitamins. process of breaking down food into a usable form. The liver is your body's chemical "factory." It takes the raw materials Cells in the lining of your stomach absorbed by the intestine and makes secrete a strong acid and powerful all the various chemicals your body enzymes that are responsible for the needs to function. breakdown process. The liver also detoxifies potentially When the contents of the stomach harmful chemicals. It breaks down are processed enough, they're and secretes many drugs that can released into the small intestine. be toxic to the body. Small intestine Gallbladder Made up of three segments — the The gallbladder stores and duodenum, jejunum, and ileum, concentrates bile from the liver and the small intestine is a 22- foot long then releases it into the duodenum muscular tube that breaks down in the small intestine to help absorb food using enzymes released by the and digest fats. pancreas and bile from the liver. Peristalsis also works in this organ, moving food through and mixing it Colon Rectum The colon is responsible for The rectum is a straight, 8-inch processing waste so that emptying chamber that connects the colon to your bowels is easy and convenient. the anus. It's a 6-foot long muscular tube that The rectum's job is to receive stool connects the small intestine to the from the colon, let you know that rectum. there is stool to be evacuated (pooped out) and to hold the stool The colon is made up of the cecum, until evacuation happens. the ascending (right) colon, the transverse (across) colon, the When anything (gas or stool) comes descending (left) colon, and the into the rectum, sensors send a sigmoid colon, which connects to message to the brain. The brain then the rectum. decides if the rectal contents can be released or not. Stool Anus Stool, or waste left over from the digestive process, is passed through The anus is the last part of the the colon by means of peristalsis, digestive tract. It is a 2-inch long first in a liquid state and ultimately in canal consisting of the pelvic floor a solid form. muscles and the two anal sphincters (internal and external). As stool passes through the colon, water is removed. Stool is stored in The lining of the upper anus is able the sigmoid (S-shaped) colon until to detect rectal contents. a "mass movement" empties it into It lets you know whether the the rectum once or twice a day. contents are liquid, gas or solid. It normally takes about 36 hours for Types of Digestive System stool to get through the colon. The stool itself is mostly food ahes and Different species of animals are bacteria. better able to digest certain types of feeds than others. This difference These "good" bacteria perform occurs because of the various types several useful functions, such as of digestive systems found in synthesizing various ns processing animals. waste products and food particles and protecting against harmful There are four basic types of bacteria. digestive systems: monogastric, avian, ruminant, and pseudo- When the descending colon ruminant. becomes full of stool, or feces, it empties its contents into the rectum Monogastric: Single- chambered to begin the ess of elimination (a Stomach bowel movement). As the word monogastric suggests, this type of digestive system  consists of one ("mono") stomach Avian Anatomy chamber ("gastric"). E.g. humans Birds face special challenges when it The process of digestion begins with comes to obtaining nutrition from the mouth and the intake of food. food. They do not have teeth, so their digestive system must be able The teeth play an important role in to process un-masticated food. masticating (chewing) or physically breaking down food into smaller Birds have evolved a variety of beak particles. types that reflect the vast variety in their diet, ranging from seeds and The enzymes present in saliva also insects to fruits and nuts. begin to chemically break down food. The stomach of birds has two chambers: the proventriculus, The esophagus is a long tube that where gastric juices are produced to connects the mouth to the stomach. digest the food before it enters the Using peristalsis, the muscles of stomach, and the gizzard, where the the esophagus push the food food is stored, soaked, and towards the stomach. mechanically ground. In order to speed up the actions of The undigested material forms food enzymes in the stomach, the pellets that are sometimes stomach has an extremely acidic regurgitated. Most of the chemical environment, with a pH between digestion and absorption happens in 1.5 and 2.5. the intestine, while the waste is excreted through the cloaca. The gastric juices, which include enzymes in the stomach, act on the Bird digestive system food particles and continue the The avian esophagus has a pouch, process of digestion. called a crop, which stores In the small intestine, enzymes stomachs, called the produced by the liver, the small proventriculus, which contains intestine, and the pancreas continue digestive juices that break down the process of digestion. food. The nutrients are absorbed into the From the proventriculus, the food bloodstream across the epithelial enters the second stomach, called cells lining the walls of the small the gizzard, which grinds food. intestines. Some birds swallow stones or grit, The waste material travels to the which are stored in the gizzard, to large intestine where water is aid the grinding process absorbed and the drier waste Birds do not have separate openings material is compacted into feces that to excrete urine and feces. Instead, are stored until excreted through the uric acid from the kidneys is rectum. secreted into the large intestine and combined with waste from the digestive process.  This waste is excreted through an The reticulum is a small pouch on opening called the cloaca. the side of the rumen that traps foreign materials, such as wire, Ruminants nails, and so forth. Ruminants are mainly herbivores, Since ruminants do not chew their such as cows, sheep, and goats, food before swallowing, they will whose entire diet consists of eating occasionally swallow foreign objects. large amounts of roughage or fiber To help digest the large amount of They have evolved digestive plant material, the stomach of the systems that help them process vast ruminants is a multi-chambered amounts of cellulose organ. An interesting feature of the The four compartments of the ruminants' mouth is that they do not stomach are called the rumen, have upper incisor teeth reticulum, omasum, and They use their lower teeth, tongue, abomasum. and lips to tear and chew their food ◆ Omasum From the mouth, the food travels The omasum is the third through the esophagus and into the compartment of the stomach. stomach. The omasum produces a grinding ◆ Rumen action on the feed and removes The first and largest section of the some of the water from the feed. stomach is the rumen. Hydrochloric acid and digestive In the rumen, solid feed is mixed and enzymes are mixed with feed in the partially broken down. omasum. The rumen contains millions of ◆ Abomasum bacteria and other microbes that The abomasum, the "true" stomach, promote fermentation, which breaks is the equivalent of the monogastric down roughages. stomach chamber. This is where The rumen also contains gastric juices are secreted. microorganisms that synthesize The four-compartment gastric amino acids and B complex chamber provides larger space and vitamins. the microbial support necessary to Amino acids are the building blocks digest plant material in ruminants. of proteins and are essential for the The fermentation process produces growth and maintenance of cells. large amounts of gas in the stomach ◆ Reticulum chamber, which must be eliminated. The reticulum is the second segment As in other animals, the small of the stomach. intestine plays an important role in nutrient absorption, while the large  intestine aids in the elimination They eat a lot of plant material and caste. roughage. Rumen Microorganisms Digesting plant material is not easy because plant cell walls contain the Ruminants rely on microorganisms polymeric sugar molecule cellulose. for the digestion of roughages. The digestive enzymes of these Bacteria are the most numerous animals cannot break down rumen microorganisms, at cellulose, but microorganisms approximately 1 billion bacteria per present in the digestive system can. milliliter of rumen fluid. Bacteria are responsible for most feed digestion Since the digestive system must be in the rumen. able to handle large amounts of roughage and break down the Protozoa are typically responsible cellulose, pseudo-ruminants have a for about 25 percent of the fiber three-chamber stomach. digestion in the rumen, even though a ruminant can survive without any In contrast to ruminants, their protozoa in the rumen cecum (a pouched organ at the beginning of the large intestine Fungi contribute up to 8 percent of containing many microorganisms the total rumen microorganisms. that are necessary for the digestion Fungi are responsible for the of plant materials) is large. digestion of cellulose and lignin in more resistant forages, such as This is the site where the roughage barley straw. is fermented and digested. Ruminant mammal digestive system These animals do not have a rumen, but do have an omasum, Ruminant animals, such as goats abomasum, and reticulum. and cows, have four stomachs. The first two stomachs, the rumen and the reticulum, contain prokaryotes and protists that are able to digest cellulose fiber, The ruminant regurgitates cud from the reticulum, chews it, and swallows it into a third stomach, the omasum, which removes water. The cud then passes onto the fourth stomach, the abomasum, where it is digested by enzymes produced by the ruminant. Pseudo-ruminants Some animals, such as camels and alpacas, are pseudo-ruminants.