Chapter 06 Human Body Processes PDF

Human body processes Biology 06 Biological processes in human body Many different biological processes take place in the human body. We will discuss about thos...

Human body processes Biology 06 Biological processes in human body Many different biological processes take place in the human body. We will discuss about those processes and the systems specialized to perform them. 6.1 Digestion of food Energy is required for different biological processes that take place in human body. Energy is obtained through food that we take into the body. These food contain nutrients such as carbohydrates, lipids and proteins. Carbohydrates, lipids and proteins are complex organic molecules that do not dissolve in water. These compounds cannot be absorbed into the human body. Threfore they should be broken down into small particles. The process by which the complex organic compounds are converted into simple organic products to be absorbed into the human body is called digestion of food. Food digestion takes place in two prosesses namely mechanical and chemical processes During mechanical process the physical nature of the food is altered, E.g. :- Breaking down of food into small pieces by teeth inside mouth. During chemical process, the insoluble complex compounds are broken down into simple molecules by the action of enzymes. E.g. :- Starch is converted into maltose by ptyalin (salivary amylase) enzyme inside mouth. There are some nutrients, that can be used by the body without any digestion, such as mineral salts, some vitamins, glucose, fructose and galactose. The organs involved in food digestion, are collectively called as digestive system. Human digestive system Human digestive system is a single tube, that runs from mouth to anus. According to the requirement, the structure has changed at different places, and the glands (salivary glands, pancreas, liver) that supply enzymes and other substances (bile) connect at different sites. The functions take place in the digestive system are food digestion, absorption of digested end products and removal of undigested materials from the body. 143 For free distribution  Biology Human body processes Let us see the structures that belong to the digestive tract. Mouth cavity Salivary glands Epiglottis Oesophagus Diaphragm Liver Gall bladder Stomach Pancreas Large intestine Small intestine Appendix Rectum Anus Figure. 6.1 - Human digestive system Assignment - 6'1 yy Identify the parts of the human digestive tract in the human torso yy Concerm about the nature, size and location of those parts Figure. 6.2 - Human torso For free distribution 144 Human body processes Biology Let us observe the changes that occur in food at first part of the digestive tract, the buccal cavity. Digestion in the buccal cavity Mouth opens the buccal cavity to the environment. It is surrounded by muscular lips at the bottom and top. The buccal cavity is made up of upper and lower jaws. Only the lower jaw can be moved. Teeth are present in both jaws. Buccal cavity is surrounded by cheeks. The tongue is attached to the floor of the buccal cavity. Three salivary glands are present and these secrete saliva and the tongue helps in identification of taste, mixing of food with saliva and swallowing. A sweet taste is sensed when chewing rice or bread for sometime. Let's discuss why it is sweet? The ptyalin enzyme (salivary amylase), acts on starch in digestion of food. Starch will be partially digested into maltose. Digestion of food is start in the mouth. Ptyalin Starch Maltose When rice or bread is chewed for sometime starch is digested into maltose. As maltose is sweet, we sense the sweet taste. Initially digested food is formed into a bolus and pushed to the posterior part of the buccal cavity. Next food is pushed into the pharynx. Pharynx is a common area to both respiratory and digestive systems. There is a movable organ called epiglottis found just above the opening of trachea. When bolus is swallowed the epiglottis moves down to close the opening of trachea. Then bolus enters into oesophagus without entering into trachea. Nasal cavity Mouth cavity Pharynx Epiglottis Epiglottis Food bolus Oesophagus Trachea Figure. 6.3 - Trachea is closed with epiglottis when food enter into oesophagus 145 For free distribution  Biology Human body processes Epiglottis helps to prevent entering food into the trachea. When food enters to pharynx, respiratory track is blocked by epiglottis. This prolong blockcage of trachea may cause death. If the food is not removed instantly, the person may die due to blockage of respiratory tract. Oesophagus is a constricted tube. How is food moved along a constricted tubule? The bolus passes through the oesophagus by peristaltic movements. As oesophagus is a muscular structure, due to contractions and relaxations of it's wall the peristaltic movements appear as waves. These peristaltic movements provide the force to propel the bolus forward. Figure. 6.4 -How the food pass through oesophagus Then food is moved into stomach by peristaltic movements. Digestion in the stomach The stomach is a dilated sac like organ. Due to the peristaltic activity of muscles in the stomach wall the bolus is broken down and mixed well into a chyme. Several secretions ooze out into the stomach. It is collectively called the gastric juice. The gastric juice contains mainly hydrochloric acid (HCl) and pepsin enyme. HCl activates pepsin and pepsin starts the protein digestion to produce polypeptides. Renin present in infants causes coagulation of milk. Chyme containing partially digested proteins, digested and undigested carbohydrates, undigested lipids, water, minerals and vitamins are released into the proximal part of small intestine, duodenum part by part. When the stomach is empty, it continues to contract. When the stomach is empty for a longer time period, the rate of contraction is also high. So it causes a pain. It gives a sense about hunger. Hunger is a signal that indicate the need of food. Digestion in the small intestine The chemical digestion of food mainly takes place in the small intestine. Pancreatic enzymes as well as intestinal enzymes involve in this digestion. The small intestine is about 7 m in length. The proximal part of the small intestine is C shaped and known as duodenum.The duct of the pancreas and the gall bladder For free distribution 146 Human body processes Biology opens into the duodenum via a single pore. Pancreatic juice is secreted into the duodenum through pancreatic duct. It contains three main enzymes. They are trypsin, amylase and lipase. The bile carried through the bile duct is added to it. Bile is produced in the liver and stored in the gall bladder. Bile contains bile pigments, bile salts, bicarbonate ions and water. Due to mixing of bile with food at duodenum, the lipids in food are broken down into small droplets by the process called emulsification. Due to this action, enzymes get a greater surface area to act on lipid food. Intestinal juice secreted by the wall of the intestine contains, maltase, sucrase, lactase, peptidase and mucous. Mucous lubricates food and then helps to move along the digestive tract. Let us summarize food digestion takes place in small intestine (See table 6.1) Table 6.1 - Enzymes in food digestion in small intestine Organ Enzyme Substrate/food End products Pancreas trypsin Protein Polypeptides (Pancreatic amylase Starch Maltose juice) lypase Lipids Fatty acids and glycerol Small intestine Maltase Moltose Glucose (Intestinal Sucrase Sucrose Glucose and Fructose juice) Lactase Lactose Glucose and galactose Peptidase Polypeptides Amino acids These are the end products of digetion Carbohydrates Monosaccharides (Glucose $ Fructose / Galactose) Protein Amino acids Lipids Fatty acids ¬ Glycerol Proteins in wall of stomach and intestine is protected by the protein digestive en- zymes as there is a layer of mucous on the wall. What happens to the end products of food digestion? The absorption of digested end products into body takes place mainly in the small intestine. The small intestine is adapted to increase its efficiency of absorption in different ways. 147 For free distribution  Biology Human body processes yy Being a long tube yy Presence of circular folds in the inner wall yy Presence of finger like projections called villi in the circular folds yy Presence of microvilli in the epithelial cells of villi yy Thin epithelial lining on villi yy Villi are highly vascularised Blood capillaries Epidermal cells Micro villi Lacteal Figure. 6.5 - Structure of villi in small intestine The digestive end products given below are absorbed into the blood capillaries of villi. yy Amino acids yy Vitamins yy Mineral salts yy Monosaccharides (Glucose/ Galactose/ Fructose) Fatty acids and glycerol formed by digestion of lipids are absorbed into lacteals. Finally they enter into blood circulatory system when there is high amount of glucose in blood, they are converted into glycogen and stored in liver. In the same way when the concentration of glucose is dicreased, glycogen breaks down to form glucose and is added to blood. The unabsorbed materials are sent to the large intestine. Processes in the large intestine Length of the large intestine is about 1.5 m. It starts with caecum and ends up at anus. The dialated part of the large intestine is the rectum. The opening of it, is the anus. The materials entering into the large intestine contain a very small amount of nutrients. Mainly it contains undigested cellulose and water. A small blind ended tubular structure starts at the end of the caecum. It is known as the appendix. It is very small in humans and it may be infected and become swollen. This disease is known as appendicitis. For free distribution 148 Human body processes Biology The main function is to absorb water from received matter by ileum. Thereby making it into semi solid. When large intestine fills with faecal matter it passes out from the rectum. The diseases and disorders associated with digestive system The chance of getting infections to the digestive tract is high as materials are entered into it from outside frequently. Therefore digestive tract catches many diseases and disorders. Engage in the following assigment to get knowledge about the diseases and disorders associated with digestive system. Assignment - 6'2 Prepare a booklet about the diseases and disorders associated with digestive tract and how to prevent them. Discuss with doctors and refer news papers, magazines for information. Gastritis Inflammation of inner lining of mucosa is known as gastritis. It is a common disease among people. Generally known as acidity. The symptoms are, regurgitation of acid to mouth, burning feeling and pain in stomach. When the condition becomes worse, ulcers appear in stomach or duodenal wall. Bleeding can take place. The reasons for this disorder are as follows, ”” Skipping of meals ”” Consumption of acidic and spicy food ”” Excessive smoking and alcohol consumption ”” Mental stress By following healthy food diets and good habits one can avoid the above disease. Constipation Difficulty in defaecation due to hardening of faecal matter is known as constipation. Faeces remain in the large intestine for a longer time period and absorption of water takes place excessively, Thereby this condition may occur. Reasons for constipation are as follows, yy Consumption of food with low dietary fibres yy Not taking required volume of water yy Postponing of defaecation 149 For free distribution  Biology Human body processes By avoiding above bad habits one can avoid this disease. Some medicine may cause constipation. Due to forceful defaecation, the anal canal may damage and bleeding can occur. Typhoid Typoid is caused by a bacterium. The pathogen is transmitted through food. The bacterium can enter into the body through mouth while swimming and bathing in contaminated water. Pain in arms and legs, headache and fever are main symptoms. It is a disease which gradually becomes worse. Constipation can occur at initial stages. Tongue is covered by a plaque. After sometime stomachache and diarrhoea can occur. Ulcers can form in the small intestine and cause bleeding. Therefore blood is released with faecal matter. Due to ulcers, the wall can be damaged. Disease can be identified by a blood test or stool test. Diarrhoea Diarrhoea occurs when the intestines are infected with a virus, bacteria or a parasite. This disease is transmitted by the faeces of an infected person. The main symptom is release of faecal matter in liquid state. Absorption of water in the large intestine will not occur properly. Dehydration may occur due to loss of fluid. due to the difeare spready contaminated food or water. The above two diseases can be avoided by taking preventive measures given below yy Consumption of boiled water yy Removing fly breeding places and cover is food to prevent entering of flies to food yy Avoid consumption of food which are sold in open places yy Use of water seal latrines yy Wash hands well with soap after using the toilet yy Get a vaccine for typhoid. If dehydration becomes worse due to diarrhoea, it may be fatal. So it is better to consume more water and consult a doctor. 6.2 Process of respiration Respiration is a biological process. Inhaling and exhaling can be observed in some animals. Respiration in a human is a complex process and it occurs in three stages. 1. Gas exchange between external environment and lungs 2. Gas exchange in alveoli 3. Cellular respiration Intake of oxygen into lungs and removal of gaseouse waste in cells occurs in ventilation. For free distribution 150 Human body processes Biology Engage in the following activity to demonstrate external gas exchange Activity - - 6'1 Demonstration of gas exchange using a model Materials required :- Small bell jar, gas tube, a cork bore, two rubber balloons, balloon membrane or polythene sheath, several rubber bands Method :- Set the apparatus as shown in the diagram. Push and release the balloon membrane and observe the condition of balloons ^A& ^B& Figure - 6.6 According to the above activity when rubber membrane is pulled down the volume inside the bell jar increases. Then external gas enters and balloons get inflated. When rubber sheath is released, gas inside balloons go out as the volume of bell jar decreases. Likewise gas exchange between external environment and lungs occurs due to changes of volume of lungs. The system involved in entering O2 into lungs and release of gaseous waste products produced during biological processes is the respiratory system. The diagram given below shows the human respiratory system. Nasal kdiacavity l=yrh Buccal uqL cavity l=yrh Pharynx.%iksldj Trachea iajrd,h Larynx Yaajdikd