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Peristalsis is referred to as a series of muscle contractions, and such contractions take place in our digestive tract. Peristalsis can also be found in the tubes that connect the kidneys to the bladder. The human body is a smart manifestation and a classic example of different mechanical movements that happen to carry out basic life functions. One such type of involuntary muscle movement is the peristaltic movement. When you gulp down food after chewing or when gas moves along your digestive tract, you feel a series of contractions in the food pipe and the stomach. These are peristaltic movements that get initiated after the complete swallowing of food. We are going to discuss in detail these movements, their role in the digestion of food, and in performing the basic human functions.
Also Read: Ultrafiltration and Reabsorption
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Key Takeaways: Peristaltic Movement, Digestion, Esophageal Peristalsis, Intestinal Peristalsis, Reverse Peristalsis, Gastric Juices.
What is Peristalsis?
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A series of wave-like muscular contractions which moves material down the digestive tract or the alimentary canal is termed Peristalsis. It’s a normal yet vital process. This rhythmic motion of smooth muscles in the intestine or other tubular organs functions by generating alternating contractions and relaxations that propel content onwards. Usually, the area ahead of the content relaxes and the area behind undergoes contractions to facilitate forward movement.
Movement of food by the wave-like muscle contractions called Peristalsis
The automatic muscle contractions start at the esophagus where smooth muscles initiate strong wave-like motions that move balls of swallowed food (bolus) into the stomach. Solid food particles are churned into liquid mixtures called chyme, which first move into the small intestine, and peristalsis continues. This motion allows the chyme to mix and shifts it back and forth allowing the bloodstream to absorb essential nutrients from the walls of the small intestine. Peristalsis facilitates water absorption into the bloodstream as it moves through the large intestine. The waves could be long, short, or continuous as they pass through the organ length based on their location and the triggering action. Having understood the basic movement mechanism, let us now see in detail the areas where peristalsis occurs n the human body.
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Esophageal Peristalsis
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Once chewing and swallowing of the food are completed, peristalsis gets initiated from the upper end of the tube and passes through its complete length to reach the stomach. One single wave is capable of moving the entire tube length in about 8-9 seconds and this movement of food through the esophagus to the stomach is esophageal peristalsis.
Smooth muscles present behind the bolus contract to prevent the food from squeezing back into the mouth. When traces of food are left behind in the mouth, a secondary peristaltic wave begins to eliminate these leftovers. Once the stomach gets filled, the excess fats in the stomach stop these peristaltic movements and the waves eventually disappear till the food gets completely digested by the gastric juices.
At any point of time in this process, 203 waves are present in separate areas of the stomach and they help mix the stomach contents and drive food into the small intestine.
Esophageal Peristalsis
Peristalsis In the Stomach
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From the esophagus, once the bolus reaches the stomach, the muscles in the stomach compress and break down the food further. This is followed by some hydrolysis of the food particles in the stomach. The peristaltic waves begin as weak contractions and then grow bigger in the parts of the digestive system, the distal region.
Pepsin is an enzyme that facilitates the hydrolysis of food particles. Here the solid food bolus is churned into a liquid mixture called chyme causing the food particles to digest partially. This partially digested food stays in the stomach for some time allowing food storage to take place. The stomach can store up to 4 liters of food at any point in time. The peristaltic movements further push the food into the duodenum which is the first food processing part of the small intestine.
Peristalsis in Stomach
Intestinal Peristalsis
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The movements of food from the stomach to the intestines happens through the pyloric valve which opens up as the peristaltic movements begin for further food processing. The peristaltic movements take place at two locations in the intestine- the small intestine and the large intestine. Let us look at these briefly.
- Small Intestine
The chyme is squeezed into the small intestine via the pyloric sphincter and this lasts only for a couple of seconds. The food further travels at a few centimeters per second. The process of digestion continues and once the nutrients are absorbed into the bloodstream from the small intestine, the food then moves into the large intestine via the peristaltic movements.
Peristalsis in Small Intestines
- Large Intestine
The peristaltic movement in this part of the intestine is almost the same as in the small intestine. The mass movements take place 1-3 times per day. The digested chyme now travels as feces or the waste product into the rectum where it is later expelled out of the body. This peristaltic movement is triggered especially after meals wherein the chyme presence and the prompt from the duodenum pushes the food into the rectum.
Peristalsis in Large Intestine
Peristalsis in Urinary System
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The urinary system has two tubes where peristalsis is observed. Peristaltic movements in the two tubes bring the liquid leftover from the digested food all the way from the kidneys up to the bladder. This muscular movement facilitates the liquid to be expelled from the body through the urethra as urine.
Things to Remember
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- Peristalsis is a smooth wave-like automatic movement that allows pushing down the content in a human body through the digestive and alimentary system.
- The major organs which use peristalsis for movement and breaking down of food are the esophagus, stomach, small intestine, and large intestine.
- Esophageal peristalsis starts after swallowing food and the series of contractions and relaxations of the smooth muscles pushes the food down to the stomach.
- The bolus in the stomach gets further partially broken down with the help of hydrolysis and after a brief period of nutrient absorption, the peristalsis in the stomach propels the food into the small intestine.
- Intestinal peristalsis involves pushing food from the small intestine after nutrient absorption into the large intestine
- The large intestine is the second location of intestinal peristalsis wherein the food is finally converted into feces and pushed to the rectum by a series of contractions and relaxations.
- The urinary system also employs peristaltic movements in the two urinary tracts where the liquid from the digested food is pushed to the urethra and is expelled in the form of urine.
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Previous Year Questions
- The characteristic that is shared by urea... [KCET 2009]
- The primary dentition in humans differs from... [NEET 2015]
- Stool of a person contain whitish grey colour due to... [NEET 2002]
- Food is moved along the alimentary canal by the contraction known as... [JIPMER 2003]
- A baby boy aged two years is admitted to play school and passes through a dental check - up. The dentist observed that the boy had twenty teeth. Which teeth were absent?… [NEET 2017]
- Which cells of "Crypts of Lieberkuhn" secrete antibacterial lysozyme?... [NEET 2017]
- Secretin and cholecystokinin are digestive hormones. They are secreted in….[NEET 2005]
- Which of the following statements is not correct?... [NEET 2015]
- If for some reason the parietal cells of the gut epithelium become partially non-functional, what is likely to happen?... [NEET 2010]
- Jaundice is a disorder of... [NEET 2010]
- Duodenum has characteristic Brunner's gland which secrete two hormones called...[NEET 2004]
- A healthy person eats the following diet-5 gm raw sugar,. 4 gm albumin, 10 gm pure buffalo ghee adultrated with 2 gm vegetable ghee (hydrogenated vegetable oil) and 5 gm lignin. How many calories he is likely to get?...[NEET 2013]
- A person who is eating boiled potato, his food contains the component...[NEET 2000]
- Anxiety and eating spicy food together in an otherwise normal human, may lead to...[NEET 2012]
- Calcium deficiency in the body occurs in the absence of...[NEET 1994]
- Choose the correct enzyme - substrate pair... [NEET 1996]
- Continuous bleeding from an injured part of body is due to deficiency of...[NEET 2002]
- Duct leading from parotid gland and opening into vestibule is...[NEET 1998]
- During prolonged fastings, in what sequence are the following organic compounds used up by the body...[NEET 2003]
- Emulsification of fat is carried out by...[NEET 1990]
Sample Questions
Ques: Discuss some common functions of the peristaltic movement. (4 marks)
Ans: The peristaltic movement is an involuntary wave-like muscular movement responsible for pushing material through multiple organs of the digestive system and the alimentary canal. Following are the prominent functions:
- Esophagus peristalsis: The movements that get triggered at the beginning of the esophagus propel food to travel through the food pipe into the stomach. These are a series of contractions and relaxative actions.
- Peristalsis of Stomach: The food particles are pushed into the stomach where they are further partially broken down by the process of hydrolysis with the help of the enzyme pepsin. After a brief storage period, these peristaltic movements further impel food into the small intestine.
- Small Intestine: The partially digested food travels through the small intestine and the nutrients get absorbed in the bloodstream. The food is then pushed into the large intestines by peristaltic movements which travel a few centimeters per second.
- Large Intestine: The mass peristaltic movements take place 1-3 times per day converting the food into feces which gets pushed into the rectum for expulsion.
Ques: What are some diseases associated with peristalsis? (4 marks)
Ans: Improper peristaltic movements cause multiple ailments. Some are listed as follows:
- Gastroesophageal Reflux Disease (GERD): The smooth muscle between the esophagus and the stomach gets affected due to the acid reflux back into the esophagus. This irritates the esophageal lining causing uneasiness.
- Hirschprung Disease: The enteric nervous system controls motility in the human body. When this system becomes non-functional, it blocks the intestine causing peristaltic movements to stop. The food hence doesn’t pass through the intestine for further processing.
- Dysphagia: The esophageal peristaltic movements are affected in this disease. Patients find it difficult to swallow food and take more time and effort to push the food from the mouth to the stomach.
- Esophageal Spasms: Intermittent or severe spasms in the esophageal muscles are triggered causing regurgitation of food.
Ques: What is reverse peristalsis? (2 marks)
Ans: The esophageal peristaltic movements are unidirectional. When the intestinal contraction wave moves in the opposite direction (food moves back to the esophagus) through the tube, this is called reverse peristalsis or anti-peristalsis, or retro-peristalsis.
Ques: What causes vomiting? (2 marks)
Ans: When there is irritation in the stomach due to food poisoning, there is an opposite flow of the food from the intestine to the mouth, reverse peristalsis. This is a result of abdomen contraction and should not be confused with opposed esophageal peristalsis. This reverse peristalsis appears as a precursor wherein the emetic center of the brain is activated. This triggers immediate vomiting as a reflex to the reverse peristalsis.
Ques: What are gastric juices? (3 marks)
Ans; As soon as the food reaches the stomach from the esophagus, different glands in the stomach secrete a mixture capable of digesting and dissolving the solid (bolus) or liquid food received in the stomach. These are gastric juices which comprise electrolytes, water, hydrochloric acid, enzymes, mucus, and intrinsic factors.
The cardiac gland is present in the upper part of the stomach, the oxyntic gland is present in the stomach body, and the pyloric gland is present in the lower part of the stomach secrete these juices that aid digestion.
Different components of gastric juices are produced by specialized cells present in these glands. These cells are:
- Neck cells: produce mucus and bicarbonate
- Parietal cells: produce hydrochloric acid
- Chief cells: produce hormones for secretion of enteroendocrine cells
Ques: Are peristaltic movements found in other animals? Explain. (2 marks)
Ans: Peristaltic movements are found in cattle like cows, sheep, giraffes, camel, etc in the form of chewing of the cud. In this process, after the food is chewed once and pushed down into the stomach, it is again brought back to the mouth by reverse peristalsis for more chewing.
Ques: How does peristalsis protect from intestinal infections? (2 marks)
Ans: Peristalsis removes gas from the system and the various gastric juices that help digestion during this process produce hydrochloric acid. These movements thus help in the absorption of iron and other nutrients and also eliminate harmful bacteria entering from food to cause intestinal infections.
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