write the major step in digestion in human being
Answers
Explanation:
Ingests food
Chews and mixes food
Begins chemical breakdown of carbohydrates
Moves food into the pharynx
Begins breakdown of lipids via lingual lipase
Moistens and dissolves food, allowing you to taste it
Cleans and lubricates the teeth and oral cavity
Has some antimicrobial activity
Pharynx
Propels food from the oral cavity to the esophagus
Lubricates food and passageways
Esophagus
Propels food to the stomach
Lubricates food and passageways
Stomach
Mixes and churns food with gastric juices to form chyme
Begins chemical breakdown of proteins
Releases food into the duodenum as chyme
Absorbs some fat-soluble substances (for example, alcohol, aspirin)
Possesses antimicrobial functions
Stimulates protein-digesting enzymes
Secretes intrinsic factor required for vitamin B12 absorption in small intestine
Small intestine
Mixes chyme with digestive juices
Propels food at a rate slow enough for digestion and absorption
Absorbs breakdown products of carbohydrates, proteins, lipids, and nucleic acids, along with vitamins, minerals, and water
Performs physical digestion via segmentation
Provides optimal medium for enzymatic activity
Accessory organs
Liver: produces bile salts, which emulsify lipids, aiding their digestion and absorption
Gallbladder: stores, concentrates, and releases bile
Pancreas: produces digestive enzymes and bicarbonate
Bicarbonate-rich pancreatic juices help neutralize acidic chyme and provide optimal environment for enzymatic activity
Large intestine
Further breaks down food residues
Absorbs most residual water, electrolytes, and vitamins produced by enteric bacteria
Propels feces toward rectum
Eliminates feces
Food residue is concentrated and temporarily stored prior to defecation
Mucus eases passage of feces through colon
These can be summarised as follows:
Basic Stages of the Digestive Process
1. Ingestion
Ingestion is the process by which food is taken into the alimentary canal.
It includes the processes that take place while the food is in the mouth (mouth = "buccal cavity"), such as chewing and grinding using the teeth, the lubrication and chemical effects of saliva released from the salivary glands, and swallowing of the food - which sends it onwards down the digestive tract.
2. Digestion
Digestion is the process by which ingested (food) material is broken down in the earlier stages of the alimentary canal into a form that can then be absorbed and assimilated into the tissues of the body.
Digestion includes two types of processes -
Mechanical (e.g. chewing, grinding, churning, mixing), and
Chemical (e.g. action of digestive enzymes, bile, acids, etc.).
The mechanical processes include the chewing and grinding of food by the teeth and also the churning and mixing of the contents of the stomach.
Chemical processes that contribute to digestion also begin in the mouth with action of saliva on food. However, most of the chemical digestive processes occur in the stomach and small intestine - where the partly-digested materials are subjected to gastric juices, pancreatic juice, succus entericus and so on.
3. Absorption / Assimilation
Absorption is the uptake of fluids or other substances by the tissues of the body.
Digested "food" (which is referred to by other terms depending on its stage of passage through the digestive system - see transit through the alimentary canal) is absorbed into the bodily fluids blood and lymph from the alimentary canal. Most of the absorption part of the digestive process occurs in the jejunum and the ileum of the small intestine, though alcohol is readily absorbed through the stomach. The small intestine is lined with minute finger-like processes (called "villi", a single example being a "villus"), that greatly increase its surface area, and hence the rate at which absorption can take place.
Assimilation is the process by which components/chemicals from food (incl. liquid refreshments such as milk drinks, fruit juices etc.) are taken into the cells of the body - after the food/beverage has been digested and absorbed.
4. Elimination
Elimination is the final stage of this 4-stage summary of digestion.
In physiology more generally the term "elimination" can apply to the entire process of excretion of metabolic waste products, incl. from the blood via the kidneys and urinary tract (as described in the section about the Renal ).