[Biology Class Notes] on Digestion Pdf

Digestion is the process of breakdown of large food molecules that are insoluble into small food molecules that are water-soluble. After the breakdown and conversion process of the food molecules, these are absorbed into the blood. Digestion is carried out by our digestive body organs, including the large intestine, small intestine, and the stomach. These body organs make up the digestive system of our body. 

 

Catabolism is a metabolic process in which large molecules are broken down into smaller molecules. Digestion is a type of catabolic process. The catabolism aspect is the breakdown of large food molecules into smaller food molecules that are soluble, and the nutrients generated by the food are absorbed by the bloodstream. Digestion is divided into two processes: mechanical digestion and chemical digestion. Refer to the official website of or download the app for an elaborate and comprehensive explanation.

 

Mechanical Digestion

Mechanical digestion refers to the breakdown of large food pieces into smaller food particles that are accessed by digestive enzymes. In chemical digestion, digestive enzymes help in the breakdown of large molecules that are insoluble into smaller molecules that are soluble.

In the human digestive system, the digestion process starts with mastication. Mastication is the chewing of food in the mouth. The food is crushed and grounded by teeth. Mastication is the mechanical digestion which occurs when the food is mixed with saliva. Saliva that is secreted by the salivary glands produces a kind of an enzyme called salivary amylase, which helps in digesting the starch present in food. Saliva also contains mucus which acts as a lubricant for the food that we eat. During mastication, when the food is mixed with saliva, it forms bolus. The bolus that is formed is then swallowed down the oesophagus from where through the action of peristalsis, it reaches the stomach.

Chemical Digestion

In the stomach, the gastric juice that contains hydrochloric acid and pepsin act upon the food particles to make simpler forms. The stomach further releases enzymes which act upon the food particles to absorb nutrients. The stomach breaks down the molecules and churns the bolus that was swallowed in the presence of gastric juice, pepsin, mucus and other enzymes. The food is not fully digested yet. It is partially digested in the stomach. The partially digested food is then entered in the duodenum, which is the first section of the small intestine. In the duodenum, the semi-digested food is called chyme. Chyme is a semi-liquid food that is passed from the stomach to the small intestine. The major part of the digestion takes place from here onwards. 

In the intestine, bile, pancreatic juice and intestinal juice are secreted, which helps in further digestion and metabolism. In the inner walls of the intestine, villi are lined, and the epithelial cells contain microvilli that support the absorption of nutrients and micronutrients. The storage capacity of the nutrients and micronutrients is increased by the villi as it increases the surface area of the intestines. From the small intestine, the food moves to the large intestine. In the large intestine, the digestion process is slowed down. The slow passage of the food helps in its fermentation. The fermentation of the food is carried out by the human gastrointestinal microbiota, which is also known as gut flora or gut microbiota. Water is absorbed from the food, and the rest of the waste which is stored as faeces is removed by the defecation process. In the defecation process, the waste material is expelled out of the body through the anal canal and anus.

Phases Of Digestion

The digestion process can be divided into three phases- the cephalic phase, the gastric phase, and the intestinal phase.

• The cephalic phase involves not just the digestive system but also the nervous system and the endocrine system, which collaborates to help the secretion of gastric acid. The sight of the cephalic phase is basically the sight of smell and food. 

• The gastric phase takes place in the stomach. It generally takes about three to four hours. With the presence of food, the pH level decreases, and this causes the enlargement of the stomach, which is called distension. There can be many other reasons for distention. Distension accelerates the secretion of various enzymes in the stomach – gastric juices and acetylcholine. 

• In the intestinal phase, the food moves to the duodenum, and from there the partially digested food is moved further to complete its full digestion.

The digestive system is complemented by the excretory system of our body. When we eat something, the food is swallowed through the digestive organs, but most of the nutrients are processed in the kidney, which is the fundamental unit of the excretory system. The unwanted materials like urea, ammonia and others are not retained but moved forward to the intestines, and from there the waste materials are expelled out of our body through the anal canal and anus. 

 

Digestive System Anatomy and Physiology

Physiology of digestive system or digestion process:

• Ingestion: Food set into the mouth before it may follow it up; this is a functioning, willful interaction called ingestion.  

• Impetus: Assuming food varieties are to be handled by more than one stomach related organ, they should be pushed starting with one organ then onto the next. Gulping is one illustration of food development that generally relies upon the propulsive cycle called peristalsis (compulsory, rotating rushes of compression and unwinding of the muscles in the organ divider).

• Food Breakdown by the Mechanical Method: It’s a mechanical absorption. Automatic absorption gets ready nourishment for additional corruption by compounds by genuinely dividing the food sources into more modest pieces. Examples of mechanical assimilation are: blending of food in the mouth by the tongue, stirring of food in the stomach, and division in the stomach by the small digestive system.  

• Food Breakdown by Chemical Methods: It’s a compound processing. The arrangement of steps in which the large food particles are separated into their structure blocks by compounds is called substance absorption.  

• Absorption: Transport of processed finished results from the lumen of the GI lot to the blood or lymph is ingested, and for assimilation to occur, the processed food sources should initially enter the mucosal cells by dynamic or inactive vehicle processes.  

• Excretion: The waste is the disposal of inedible buildups from the GI lot using the butt as defecation. 

 

Anatomy of the Digestive System 

The stomach-related framework’s organs can isolate into two fundamental gatherings: those shaping the nutritious channel and the frill stomach-related organs. Following is the digestion diagram depicting all the organs and glands involved.

 

                                            ( Image Will be Updated Soon )

 

Mouth 

Food enters the gastrointestinal system through the mouth, or oral cavity, a mucous layer lined hole.  

• Tongue: The solid tongue possesses the floor of the mouth and has a few complex connections; two of these are to the hyoid bone and the styloid cycles of the skull.  

• Lingual Frenulum: The lingual frenulum, an overlap of mucous film, ties down the tongue to the floor of the mouth and restricts its back developments.  

• Palatine Tonsils: At the back finish of the oral pit are combined masses of lymphatic tissue, the palatine tonsils.  

• Lingual Tonsil: The lingual tonsils cover the foundation of the tongue just past. 

 

Pharynx 

Food from the mouth passes into the oropharynx and laryngopharynx. 

 

Oesophagus 

The throat or neck runs from the pharynx through the stomach to the stomach.  Distinct nerve plexuses. The nutritious trench divider contains two significant inborn nerve plexuses- the submucosal nerve plexus and the myenteric nerve plexus. The two of which are organisations of nerve strands that are part of the autonomic sensory system and assist with managing the versatility and secretory movement of the GI parcel organs. 

 

Stomach 

The C-moulded stomach is on the left half of the stomach pit, almost concealed by the liver and the stomach.  The stomach goes about as a transitory “stockpiling tank” for food just as a site for food breakdown. The fundus is the extended piece of the stomach horizontal to the heart area.  The pylorus is present at the terminal of the stomach. It is filled by a small tract via the valve or the pyloric sphincter.  The mucosa of the stomach is tossed into enormous folds called rugae when it is vacant.  

 

The more major momentum, one more expansion of the peritoneum, wraps descending and covers the stomach organs like a soft cover before joining to the back body divider, and is loaded with fat, which assists with protecting, padding, and securing the stomach organs.  The stomach mucosa is a straightforward columnar epithelium made out of mucous cells that produce a defensive layer of bicarbonate-rich essential bodily fluid that sticks to the stomach mucosa and shields the stomach divider from being harmed by corrosive and processed catalysts.

 

Small Intestine

The small digestive tract is a solid cylinder stretching out from the pyloric sphincter to the internal organ. It is the most extended segment of the nutritious cylinder, with an average length of 2.5 to 7 m (8 to 20 feet) in a living individual.  

 

The small digestive tract has three developments: the duodenum, the jejunum, and the ileum, which contribute 5%, almost 40%, and just about 60% of the small digestive system, individually.  

• Ileocecal Valve: The ileum meets the digestive organ at the ileocecal valve, which joins the vast and small digestive system.  

• Hepatopancreatic Ampulla: The primary pancreatic and bile channels join at the duodenum to frame the flasklike hepatopancreatic ampulla, in a real sense, the “liver-pancreatic augmentation.”  

• Duodenal Papilla: From that point, the bile and pancreatic juice travel through the duodenal papilla and enter the duodenum together.  

• Microvilli: Microvilli are minuscule projections of the plasma film of the mucosa cells that give the cell surface a fluffy appearance, at times alluded to as the brush line; the plasma layers bear catalysts (brush line chemicals) total the absorption of proteins and starches in the small digestive tract.  

• Villi: Villi are finger-like projections of the mucosa that give it a smooth appearance and feel, similar to a towel’s delicate rest.  

• Lacteal: Inside every villus are a rich narrow bed and an altered lymphatic hairlike called a lacteal.

 

Ease the Digestion Process

The lifestyle change has developed serious digestion issues including lifestyle diseases including the youngsters. And the only way to go back to healthier ways is by adding some extra activities. Since we have already come to a point in life where we cannot eliminate non-vegetarian and fast food. 

 

So some of the changes that are done for the daily routine will help to ease the condition of our health to a great extent. So check out the points down below. 

• Heavy exercises after the food have to be avoided.

• After dinner, do not sleep immediately. Walk for about 10 minutes and only sleep at least 2 hours later. The food you eat needs 4 hours to digest completely.

• Brushing your teeth. As you already know about mechanical digestion, students should know how much hygiene our mouths should be!

• Drinking warm water will help to ease the digestion process and also kill the germs if present in our body.

• Taking heavy food often leads us to be overwhelmed. Do you want a solution for this? Add turmeric to your cuisine. The consumption of turmeric will never turn into a toxic habit. 

Obesity, diabetes have become more common among teenagers. This is only because of the unhealthy food they consume and also lessened physical activities. 

 

However, adopting the above mentioned can at least avoid the indigestion issues and avoid visiting the doctors frequently.