Define this: The digestive system?

Question

Trace/ explain the pathway through the alimentary canal from the mouth to the rectum, taking notes of all the organs/ structures found at each stage.

Answer 1

The digestive system is responsible for the intake and digestion of food and water, the absorption of nutrients, and the elimination of solid waste products.
The major structures of the digestive system include the oral cavity, pharynx, esophagus, stomach, and small intestines. The liver, gallbladder, and pancreas are organs associated with the digestive system.
The mechanical and chemical process of digestion begins in the mouth. The pharynx is the cavity in the caudal oral cavity that joins the respiratory and gastrointestinal systems. The esophagus is a collapsible muscular tube that leads from the oral cavity to the stomach. After the esophagus, the remaining organs of digestion are located in the abdominal cavity. The small intestine or small bowel extends from the pylorus to the proximal part of the large intestine. The large intestine or large bowel extends from the ileum to the anus.

Answer 2

Digestion is the process of metabolism whereby a biological entity processes a substance, in order to chemically and mechanically convert the substance into nutrients.


In humans, digestion begins in the oral cavity where food is chewed (mastication) with the teeth. The process stimulates exocrine glands in the mouth to release digestive enzymes such as salivary amylase, which aid in the breakdown of carbohydrates. Chewing (mechanical catabolism) also causes the release of saliva, which helps condense food into a bolus that can be easily passed through the oesophagus. The oesophagus is about 20 centimeters long. Saliva also begins the process of chemical catabolism, hydrolysis. Once food is chewed properly, the food is swallowed. The bolus is pushed down by the movement called peristalsis, which is an involuntary wave-like contraction of smooth muscle tissue, characteristic of the digestive system. The mechanism for swallowing is co-ordinated by the swallowing centre in the medulla oblongata and pons. The reflex is initiated by touch receptors in the pharynx as a bolus of food is pushed to the back of the mouth by the tongue. The uvula is a small flap that hangs from the roof of the mouth. During swallowing it and the soft palate retract upward and to the rear to close the nasopharynx, which prevents the food from entering the nasal passages by triggering closure of the soft palate. When swallowed, the food enters the pharynx, which makes special adaptations to prevent choking or aspiration when food is swallowed. The epiglottis is a cartilage structure that closes temporarily during swallowing, preventing food and liquids from entering the trachea.

The food enters the stomach upon passage through the cardiac sphincter. In the stomach, food is further broken apart through a process of heuristic churning and is thoroughly mixed with a digestive fluid, composed chiefly of hydrochloric acid, and other digestive enzymes to further denature proteins. The parietal cells of the stomach also secrete a compound, intrinsic factor which is essential in the absorption of vitamin B-12. As the acidic level changes in the small intestines, more enzymes are activated to split apart the molecular structure of the various nutrients so they may be absorbed into the circulatory or lymphatic systems.

After being processed in the stomach, food is passed to the small intestine via the pyloric sphincter. This is where most of the digestive process occurs as chyme enters the first 10 inches of the small intestine, the duodenum. Here it is further mixed with 3 different liquids: (1)bile (which helps aid in fat digestion, otherwise known as emulsification), (2) pancreatic juice and enzymes, (made by the pancreas), and (3) intestinal enzymes of the alkaline mucosal membranes. The enzymes include: maltase, lactase and sucrase, to process sugars. Trypsin and chymotrypsin are other enzymes added in the small intestine. (Bile also contains pigments that are by-products of red blood cell destruction in the liver; these bile pigments are eliminated from the body with the feces.) Most nutrient absorption takes place in the small intestine. The nutrients pass through the small intestine's wall, which contains small, finger-like structures called villi. The blood, which has absorbed nutrients, is carried away from the small intestine via the hepatic portal vein and goes to the liver for filtering, removal of toxins, and nutrient processing. The primary activity here is regulation of blood glucose levels through a process of temporary storage of excess glucose that is converted in the liver to glycogen in direct response to the hormone insulin. Between meals, when blood glucose levels begin to drop, the glycogen is converted back to glucose in response to the hormone glucagon.

After going through the small intestine, the food then goes to the large intestine. The large intestine has 3 parts: the cecum (or pouch that forms the T-junction with the small intestine), the colon, and the rectum. In the large intestine, water is reabsorbed, and the foods that cannot go through the villi, such as dietary fibre, can be stored in large intestine. Fibre helps to keep the food moving through the G.I. tract. The food that cannot be broken down is called faeces. Faeces are stored in the rectum until they are expelled through the anus.

Answer 3

Digestive gadget is the gadget that breaks down of chemical factors interior the physique, right into a sort which would be absorbed. it is likewise the gadget that procedures the technique referred to as digestion by potential of which the physique breaks down chemical factors into smaller factors which would be absorbed by potential of the blood circulate.

Answer 4

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Answer 5

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