The Digestive System in Mammals

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Anatomy and Physiology of Animals/The Gut and Digestion
Save Search You can save your searches here and later view and run them again in "My saved searches". The Honey Possum The diet is a mix of nectar and pollen, an energy rich diet needed to maintain the possum's high metabolic rate. The duodenum receives 3 different secretions:. The digestive tract, alimentary canal or gut is a hollow tube stretching from the mouth to the anus. When the bolus reaches the stomach, the first portion of the stomach is the cardiac portion of the stomach. In addition to oral structures, the principal parts of the digestive system are pharynx, esophagus, stomach, small intestines, and large intestines. Nutritional value and diet preference of arboreal lichens and hypogeous fungi for small mammals in the Rocky Mountains.

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Their guts also tend to be lengthy and the food takes a long time to pass through it. Eating plants have other advantages. Plants are immobile so herbivores normally have to spend little energy collecting them.

This contrasts with another main group of animals - the carnivores that often have to chase their prey. Carnivorous animals like those in the cat and dog families, polar bears, seals, crocodiles and birds of prey catch and eat other animals. They often have to use large amounts of energy finding, stalking, catching and killing their prey. However, they are rewarded by the fact that meat provides a very concentrated source of nutrients.

Carnivores in the wild therefore tend to eat distinct meals often with long and irregular intervals between them. Time after feeding is spent digesting and absorbing the food. The guts of carnivores are usually shorter and less complex than those of herbivores because meat is easier to digest than plant material.

Carnivores usually have teeth that are specialised for dealing with flesh, gristle and bone. They have sleek bodies, strong, sharp claws and keen senses of smell, hearing and sight. They are also often cunning, alert and have an aggressive nature. Many animals feed on both animal and vegetable material — they are omnivorous. There are currently two similar definitions of omnivorism:. Some animals fit both definitions of omnivorism, including bears, raccoons, dogs, and hedgehogs.

Their food is diverse, ranging from plant material to animals they have either killed themselves or scavenged from other carnivores. They are well equipped to hunt and tear flesh claws, sharp teeth, and a strong, non-rotational jaw hinge , but they also have slightly longer intestines than carnivores, which has been found to facilitate plant digestion.

The examples also retain an ability to taste amino acids, making unseasoned flesh palatable to most members of the species. Classically, humans and chimpanzees are classified as omnivores. Humans, conversely, have chosen to eat meat for much of the archaeological record, although their teeth, jaw hinge, and stomach pH, and intestinal lengths also closely match other herbivores. First, there is research that both plant-only and some-animal diets promote health longevity and freedom from disease in humans.

Second, well-off humans have often chosen to eat meat and dairy products throughout written history, which some argue shows that we prefer meat and dairy by latent instinct. Per the classical definition, omnivores lack the specialized teeth and guts of carnivores and herbivores but are often highly intelligent and adaptable reflecting their varied diet.

Whether an animal eats plants or flesh, the carbohydrates , fats and proteins in the food it eats are generally giant molecules see chapter 1.

These need to be split up into smaller ones before they can pass into the blood and enter the cells to be used for energy or to make new cell constituents. The digestive tract, alimentary canal or gut is a hollow tube stretching from the mouth to the anus. It is the organ system concerned with the treatment of foods. At the mouth the large food molecules are taken into the gut - this is called ingestion. They must then be broken down into smaller ones by digestive enzymes - digestion , before they can be taken from the gut into the blood stream - absorption.

The cells of the body can then use these small molecules - assimilation. The indigestible waste products are eliminated from the body by the act of egestion see diagram The food that enters the mouth passes to the oesophagus , then to the stomach , small intestine , cecum , large intestine , rectum and finally undigested material exits at the anus. The liver and pancreas produce secretions that aid digestion and the gall bladder stores bile. Herbivores have an appendix which they use for the digestion of cellulose.

Carnivores have an appendix but is not of any function anymore due to the fact that their diet is not based on cellulose anymore. The mouth takes food into the body. In elephants the lips and nose have developed into the trunk which is the main food collecting tool. The sight or smell of food and its presence in the mouth stimulates the salivary glands to secrete saliva.

There are four pairs of these glands in cats and dogs see diagram The fluid they produce moistens and softens the food making it easier to swallow. It also contains the enzyme, salivary amylase , which starts the digestion of starch. The tongue moves food around the mouth and rolls it into a ball called a bolus for swallowing.

Taste buds are located on the tongue and in dogs and cats it is covered with spiny projections used for grooming and lapping. Swallowing is a complex reflex involving 25 different muscles. Teeth seize, tear and grind food. They are inserted into sockets in the bone and consist of a crown above the gum and root below.

The crown is covered with a layer of enamel , the hardest substance in the body. Below this is the dentine , a softer but tough and shock resistant material. At the centre of the tooth is a space filled with pulp which contains blood vessels and nerves.

The tooth is cemented into the socket and in most teeth the tip of the root is quite narrow with a small opening for the blood vessels and nerves see diagram In teeth that grow continuously, like the incisors of rodents, the opening remains large and these teeth are called open rooted teeth.

Mammals have 2 distinct sets of teeth. The first set, the milk teeth , are replaced by the permanent teeth. All the teeth of fish and reptiles are similar but mammals usually have four different types of teeth.

In rodents and rabbits the incisors never stop growing open-rooted teeth. They must be worn or ground down continuously by gnawing. They have hard enamel on one surface only so they wear unevenly and maintain their sharp cutting edge. The largest incisors in the animal kingdom are found in elephants, for tusks are actually giant incisors. Sloths have no incisors at all, and sheep have no incisors in the upper jaw see diagram Instead there is a horny pad against which the bottom incisors cut.

They are particularly well developed in the dog and cat families where they are used to hold, stab and kill the prey see diagram The tusks of boars and walruses are large canines while rodents and herbivores like sheep have no or reduced canines. In these animals the space where the canines would normally be is called the diastema. In rodents like the rat and beaver it allows the debris from gnawing to be expelled easily. The cheek teeth or premolars and molars crush and grind the food.

They are particularly well developed in herbivores where they have complex ridges that form broad grinding surfaces see diagram These are created from alternating bands of hard enamel and softer dentine that wear at different rates. In carnivores the premolars and molars slice against each other like scissors and are called carnassial teeth see diagram They are used for shearing flesh and bone. The numbers of the different kinds of teeth can be expressed in a dental formula.

This gives the numbers of incisors, canines, premolars and molars in one half of the mouth. The numbers of these four types of teeth in the left or right half of the upper jaw are written above a horizontal line and the four types of teeth in the right or left half of the lower jaw are written below it.

It indicates that in the upper right or left half of the jaw there are no incisors or canines i. In the lower right or left half of the jaw are three incisors, one canine, three premolars and three molars see diagram The formula indicates that in the right or left half of the upper jaw there are three incisors, one canine, four premolars and two molars.

In the right or left half of the lower jaw there are three incisors, one canine, four premolars and three molars see diagram The oesophagus transports food to the stomach. Food is moved along the oesophagus, as it is along the small and large intestines, by contraction of the smooth muscles in the walls that push the food along rather like toothpaste along a tube. This movement is called peristalsis see diagram The stomach stores and mixes the food.

Glands in the wall secrete gastric juice that contains enzymes to digest protein and fats as well as hydrochloric acid to make the contents very acidic. The walls of the stomach are very muscular and churn and mix the food with the gastric juice to form a watery mixture called chyme pronounced kime.

Rings of muscle called sphincters at the entrance and exit to the stomach control the movement of food into and out of it see diagram Most of the breakdown of the large food molecules and absorption of the smaller molecules take place in the long and narrow small intestine. The total length varies but it is about 6.

It is divided into 3 sections: The duodenum receives 3 different secretions:. These complete the digestion of starch, fats and protein. Houston, we have a problem! Stand out and be remembered with Prezi, the secret weapon of great presenters.

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Comments 0 Please log in to add your comment. Transcript of Mammal Digestive System The honey possum Tarsipes rostratus , is a native australian marsupial nectar feeder. The honey possum is found mainly in the southwest woodlands of Western Australia Dingo The dingo Canis Lupis Dingo is a free-ranging dog found mainly in Australia. They live in deserts, grasslands and forest edges. Red Kangaroo The red kangaroo Macropus rufus is the largest native terrestrial mammal in Australia.

It is found across mainland Australia, favouring less fertile areas of land Honey Possum Red Kangaroo A grazing herbivore, kangaroos rely solely on plants and vegetation. They do not need to intake much water, and obtain sufficient nourishment from leaves. The digestion of microbes from vegetation in the kangaroo's stomach acts as the main source of protein. Dingo Dingos eat a diet composed of mainly meat, including animal flesh, organs and muscle tissue.

This is very high in protein and fat, and provides the animal with large amounts of energy. The Honey Possum The diet is a mix of nectar and pollen, an energy rich diet needed to maintain the possum's high metabolic rate.

Nectar contains sugars including glucose, fructose and sucrose. Pollen cells contains protein, carbohydrates and fats. All of which serve as the main energy source to the organism. Common food sources include banksia pollen and nectar, bottlebrushes and dryandras. Red Kangaroo The Red Kangaroo has a specialized jaw to suit grazing habits, with increased room between the molars and the front teeth.

The stomach is long and tubular; consisting of 2 main sections, the enlarged fore-stomach and the hind stomach. The fore stomach is split into the sacciform and the tubiform by a ventral fold. The sacciform acts as a storage compartment and tubiform is mainly used for fermentation. They often regurgitate food to eat it again, which then recycles through the digestive system again.

Honey Possum The possum has a long pointed snout with a brush tip tongue that gathers pollen and nectar. The digestive system is small, as the ingested foods nectar are ready for immediate absorption when ingested. The digestive system lacks a caecum, making the small and large intestine hard to differentiate.

Proteins and pollens are digested in the large intestine. Native Australian Mammals Chemical Composition of Diet Main digestive structures and functions The Mammal Digestive System Dingo The dingo has a short and relatively non-complex digestive system due to the fact they do not digest any cellulose. The stomach is adapted to consume animal flesh.

The digestive system has very poor regions for microbial fermentation; with a short small intestine. Limited microbial digestion occurs in the shortened caecum.

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