...n food made by autotrophs. Types of heterotrophic nutrition Heterotrophic organisms have evolved many different ays of obtaining the organic nutrients they need. Holozoic nutrirtion Is the method by hich humans and other mammals feed, as ell as many other animals such as insects .food, in solid or liquid form is taken into a tube called the alimentary canal here it is digested and absorded into the body.Saprotrophic nutritionIs the method by hich fungi and many prokaryotes feed. They live and gro on their substance , hich can be anything organic, such as milk bread or dead body .They secrete enzymes from their bodies, and digest the food material around them before absorbing it.Parasitic nutritionIs the method of feeding hich has evolved in many different groups of organisms, including various kinds of orms and fungi and a fe plants. Parasites fed on, and live in close association ith, a living organism of a different species, called their host. They can feed either holozoically biting their host or sucking fluids from it, or they can feed saprotrophically ,absorbing soluble food into their bodies. Holozoic nutrition-feeding in humansHumans like all other animals are heterotrophs .This means that e need to eat food containing organic molecules. These organic molecules includes carbohydrates, fats and proteins. This all are our only source of energy. In contrast autotrophs such as green plants do not need to take in any organic molecules at all. They obtain their energy from sunlight, and can use their energy to built organic molecules from inorganic one. They produce carbohydrates from carbon dioxide and ater, by photosynthesis and can them use these carbohydrates, plus inorganic ions such as nitrate, phosphate and magnesium , to manufacture all the organic molecules that they require .Heterotrophs therefore depend on autotrophs for the supply of organic molecules on hich they feed. Some of them feed directly on plants, hile others feed further along a food chain. But eventually all of our food can be traced back to green plants, and the energy of sunlight. The structure of the human alimentary canalThe alimentary canal is a long hollo tube hich runs from the mouth to the anus .Together ith several other organs, including the liver and the pancreas, it makes up the digestive system.The total length of the human alimentary canal is beteen 5 and 6 m, from anus to mouth. To fit this considerable length into body, parts of the canal are folded and coiled inside the abdomen .The mucus is a substance secreted along the tube by cells lining its alls .Mucus helps food to slide through the canal ithout doing too much damage to the lining. It also forms a protective covering hich keeps the digestive juices, hich are inside the lumen of the canal, from coming into contact ith the living cells of the alls. Along the hole length of the alimentary canal there are muscles in the alls. These produce aves, ofContraction and relaxation called peristaltic aves, hich move food along the alimentary canal and help to mix the contents. Each region of the alimentary canal has it on function and different structure. There are 4 basic layers in the all of the alimentary canal. orking from the inside these are a the mucosa b the submucosa c the muscularis externa d the serosa. Many of this names came from Latin origin.The mucosa is made up of 3 layers. The innermost layer is the epithelium. The structure of the epithelium varies in different parts of INCLUDEPICTURE http.mhhe.combiosciapdynamichuman2contentgifs0123.
gif t MERGEFORMATINET the alimentary canal, but it alays contains cells hich secrete mucus.Beneath it is a layer of connective tissue called lamina propria, hich means closest layer. And beneath that is a layer of smooth muscle called the muscular is mucosa.The sub mucosa is made up of areole connective tissue. This is an open-textured stretchy tissue, containing many elastic fibred and collagen fibres. Running through it are numerous blood vessels and nerves.The muscularis externa ia made of to layers of muscle. The innermost layer has fibres running around the tube, and is called circular muscle. The outermost layer has fibres running along the tube and it is called longitudinal muscle.The serosa is a very thin layer, made up of connective tissue covered ith a single layer of thin, smooth closely fitting cells. INCLUDEPICTURE http.mhhe.combiosciapdynamichuman2contentgifs0120.
gif t MERGEFORMATINET e can observe in detail each part of the human alimentary canal structure in this diagram.The mouthTaking food into the mouth is called ingestion. e use lips, tongue and teeth. The tongue is also important in tasting food, to tell you hether it is good to eat if not it ill be ejected from the mouth rather than salloed.The main purpose of the human teeth is to break up large pieces of food, thus beginning the process of the mechanical digestion. This is done by cheing, or mastication. Strong muscle is the jas move the loer ja up and don from side to side, grinding the teeth in the loer ja against those in the upper ja.The premolar and molar teeth have ridges and grooves, hich trap food beteen them and crush it as che. Mastication greatly increases the surface area of the food, bringing more of it into direct contact ith enzymes in the digestive juice and so speeding up chemical digestion.Three pairs of salivary glands secrete atery liquid saliva, hich pours along ducts into the mouth. Like all secretions along the alimentary canal, saliva is mostly ater. It contains mucus, hich mixes ith the food as it is cheed, helping to glue it loosely together into a ball called a bolus. The mucus also makes the bolus slippery, so that is easier to sallo.Saliva contains the enzyme amylase, hich catalyses the hydrolysis of starch. .Thus, digestion by amylase produces maltose and small chain made up of three, four or more glucose molecules on the end of a chain . Thus , digestion by amylase produces maltose and small chains made up three, four or more glucose molecules linked together, but it does not produce individual glucose molecules.Saliva also contains an enzyme called lysozyme. This enzyme, hich is also found in tears, can destroy several types of bacteria hich can cause infection in the mouth and throat, including Staphylococcus and Streptococcus. The lysozyme,together ith a general ashing action of saliva, and a small amount of hydrogen carbonate ions in it hich partly neutralizes acids on teeth appear to help reduce the incidence of tooth decay.The stomachhen a bolus of food is salloed ,it is moved siftly don to the esophagus by peristalsis and into stomach.The stomach is a muscular sac, ith a capacity of up 5 dm.. In some parts of the stomach the muscle layers of the muscularis externa are thicker than in most other parts of the alimentary canal. They produce strong, rhythmic, churning movements hen th...
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