HUMAN DIGESTIVE SYSTEM HUMAN DIGESTIVE SYSTEM

HUMAN DIGESTIVE SYSTEM Human Digestive system is an organ system through which food enters the body, is broken down into simpler substances, absorbed, assimilated, and the undigestive food is thrown out of the body. HUMAN DIGESTIVE SYSTEM ALIMENTARY CANAL (DIGESTIVE TRACT - PROCESS OF DIGESTION TAKES PLACE) MOUTH (ORAL CAVITY) PHARYNX OESOPHAGUS STOMACH SMALL INTESTINE LARGE INTESTINE ANUS DIGESTIVE GLANDS (SECRETES DIGESTIVE JUICES IN THE ALIMENTARY CANAL AND HELP IN THE BREAKDOWN OF FOOD) SALIVARY GLANDS PANCREAS LIVER ALIMENTARY CANAL A long, hollow tube that starts at the mouth and ends at the anus. It is made up of numerous organs that work collectively for the digestion of food. The organs are : MOUTH (ORAL CAVITY) PHARYNX OESOPHAGUS STOMACH SMALL INTESTINE LARGE INTESTINE ANUS

ORAL CAVITY OR MOUTH The oral cavity is important for the ingestion (food is taken into the mouth and broken mechanically into pieces and mixed with saliva) of food, and to a certain extent its digestion. It includes Teeth Tongue Salivary glands (secretes saliva that contains an enzyme called Salivary Amylase) An adult human has 32 permanent teeth that helps in the breakdown of food into smaller pieces. These are of four different types: Incisors (8) biting and cutting Canines (4) tearing Premolars (8) grinding and crushing Molars (12) grinding and crushing Digestion STARCH salivary amylase Maltose After chewing and mixing with saliva, a semi solid mass of food is formed that makes the food easy to sallow - Bolus PHARYNX Wide, muscular tube situated posterior to the oral cavity and serves as the common pathway for food and air. OESOPHAGUS Tube extending from the mouth to the stomach. It has longitudinal and circular muscles in its walls. From the mouth the food is pushed into the stomach via the oesophagus. This is aided by a process called Peristalsis. Peristalsis A wave of muscular contractions that occur throughout the length of alimentary canal. STOMACH Expandable, J- shaped, sac like organ located on the left side of the abdominal cavity at the end of the oesophagus. Walls of the stomach secrete Gastric glands.

GASTRIC GLANDS HYDROCHLORIC ACID PEPSIN (Enzyme) Creates an acidic medium PROTEINS Pepsin Proteoses + Peptones Stomach in the muscles stomach churns the bolus with gastric juices to form a soupy liquid called Chyme, that passes Kills to the small bacteria intestine. Activates pepsin SMALL INTESTINE Narrow and extremely colied tube present behind the stomach. It has 3 parts: Upper Duodenum Middle Jejunun Lower coiled Ileum The inner walls of the small intestine contain numerous finger like projections called villi. Each villus has projections called microvilli to increase the surface area for maximum digestion and absorption of food. DUODENUM RECEIVES BILE FROM GALL BLADDER Provides an alkaline medium for the pancreatic juice to act PANCREATIC JUICE FROM PANCREAS Pancreatic Juice secretes Emulsification of fat breaking down fat into smaller fat droplets From the Duodenum, the chyme passes into the jejunum and then into ileum. Cells lining the ileum secretes an intestinal juice that contains the enzymes like erepsin, maltase, sucrose and lactase. Food is acted upon by these enzymes and is completely digested.

LARGE INTESTINE Undigested food passes into the large intestine where most of the water is absorbed into the blood, leaving behind a mass of undigested food called faeces. FINAL PRODUCTS OF DIGESTION CARBOHYDRATES GLUCOSE PROTEINS AMINO ACID FATS FATTY ACID + GLYCEROL INDIGESTION A condition of pain or discomfort in the stomach and an inability to digest the food properly. SYMPTOMS Bloating Nausea Vomiting Pain Heartburn CAUSES Drinking too much coffee or tea Consuming foods rich in fats and sugars Lack of sleep Presence of intestinal parasites HEALTHY FOOD HABITS Healthy eating is important for a sound body and mind. We should aim for a balanced diet and eat a variety of foods in moderation. Flavoured, carbonated and sugary foods should be avoided or consumed in very small quantities. It is important to eat substantial breakfast every day. We should choose seasonal and fresh fruits over frozen or preserved foods.

HUMAN RESPIRATORY SYSTEM The process by which food (glucose) is broken down in the cells to release energy is called respiration. Carbon dioxide and water vapour are produced as waste products and are removed from the body. In humans respiration takes place by following reaction. Glucose + Oxygen Carbon dioxide + water +energy The oxygen required for breaking down food to release energy is provided by respiratory system. Parts of respiratory system Nose Pharynx Larynx Trachea Bronchi and bronchioles Lungs Nose Air enters body through nose. It has two nostrils which leads into a pair of nasal chambers. Pharynx Common passage for air coming from the nose and for food coming from the food pipe. Larynx The larynx is an organ in the top of the neck involved in breathing, producing sound, and protecting the trachea against food aspiration. The larynx houses the vocal cords, and manipulates pitch and volume. It is situated just below where the tract of the pharynx splits into the trachea and the oesophagus.

Trachea Carries air from the nose to the lungs. C- Shaped cartilaginous rings in the walls of the trachea allows air to reach the lungs without any obstruction. Bronchi and bronchioles Trachea divides into two tubes, bronchi, which leads to left and right lungs. Inside lungs, each bronchus further divides into bronchioles which ends in minute air sacs called alveoli. Lungs Pair of spongy organs located within the chest cavity. There are million soft alveoli in each lung. Each alveolus is surrounded by a network of thin walled capillaries. Exchange of gases takes place here by diffusion. Breathing The process by which air is taken in and given out of the body is called breathing. Mechanism of breathing Inhalation The process by which air enters the lungs through the nose. Muscles of ribcage contract causing the ribcage to move upward and outward. The diaphragm moves downwards. Exhalation The process by which air rushes out of the lungs through the nose. Muscles of ribcage relax causing the ribcage to move inwards and downwards. The diaphragm arches up, compressing the chest cavity. Differences between breathing and respiration Physical process Biochemical process in which oxygen combines with food. It takes place outside the cell. It takes place inside the cell. No energy is released Food is broken down to release energy Process of breathing is different in different organisms Process of respiration is same in all organisms

Some respiratory diseases Asthma Chronic disease caused by obstruction of airways. Symptoms- wheezing, shortness of breath, coughing. Causes- can be triggered by various reasons including allergies. Bronchitis Condition in which bronchial tubes get inflamed and more mucus is accumulated than usual. It causes shortness of breath, wheezing and cough and tightness of chest. Causes- exposure to tobacco smoke, dust, fumes, vapour and air pollution. Pneumonia Caused when the alveoli get filled up with fluid or pus resulting in bacterial, viral or fungal infection in lungs. The airways gets thickened with mucus making it difficult for air to move in the lungs. Symptoms- fever, chills, cough with phlegm. Tuberculosis Caused by bacteria. Usually affects the lungs but can also spread to different parts of the body. Highly infectious but can be cured by well-planned course of antibiotics.

HUMAN CIRCULATORY SYSTEM Responsible for transporting materials like nutrients, water and oxygen to all body cells. Helps in carrying waste like carbon dioxide away from the body cells. Has three major parts: blood, blood vessels and the heart. BLOOD Composed of two components- Blood Cells. They lie suspended in the plasma Are of 3 types Plasma Straw coloured fluid in which blood cells are suspended. Function-without plasma, blood cells would have no medium to travel. i) Red Blood Cells ( Erythrocytes): Produced in the bone marrow Red colour is due to the presence of iron containing pigment called Haemoglobin. Function: The haemoglobin combines with oxygen to form oxyhaemoglobin to be carried from the lungs to all the body cells. ii) White Blood Cells (Leucocytes): colourless blood cells produced in the lymph nodes, the spleen and tonsils Function: They defend the body against harmful foreign bodies, such as bacteria.

They flow smoothly through the blood and reach the site of infection and destroy the germs in the body by engulfing and digesting them. iii) Platelets (Thrombocytes): Colourless blood cells Function: They play a major role in healing wounds. When there is a wound, the blood vessel gets ruptured and blood flows out. To prevent excessive loss of blood, platelets in blood gather around the wound- blood dries up and forms a clot- thus preventing further loss of blood from the wound. Blood Groups; Human blood is classified into major groups- A, B, O and AB. Person with blood group O is a Universal Donor- this person can donate blood to a person of any blood group. Person with blood group AB- is a Universal Recipient- this person can receive blood from a person of any blood group. Blood Vessels: Network of hallow tubes found throughout the body. Are of three types- arteries, veins and capillaries. Arteries Veins Capillaries Muscular, thick walled elastic vessels with narrow cavities Thin walled vessels with larger cavities. Extremely narrow blood vessels forming networks around organs and tissues of the body. Walls made up of a single layer of cells. Carry blood from the heart to different parts of the body. Carry or transport blood from different parts of the body to the heart. Carry blood from arteries or arterioles and supplies or transports them to venules/ veins.

Blood flows at a high pressure through arteries. Generally carry oxygenated blood except pulmonary artery which carries deoxygenated blood. Largest artery is called the Aorta, smaller arteries - called arterioles. Veins transport blood at lower pressure compared to arteries. Generally carry deoxygenated blood except pulmonary vein which carries oxygenated blood. Largest veins in the body are called Superior and Inferior Vena Cava, smaller veins called venules. Have valves at regular intervals to prevent backflow of blood. Permit exchange of gases, nutrients and wastes between blood and cells in the body. HEART: Muscular organ located in the centre of the chest cavity slightly to the left between the two lungs. Walls of heart are made up of cardiac muscles that contract rhythmically. Function: To pump blood in order to keep the blood moving throughout the body. CIRCULATION OF BLOOD IN THE HEART: Heart has four chambers- two upper chambers (thin layered) called atria or auricles and two lower chambers (thick layered) called ventricles. Atria or auricles receive blood from different organs in the body and pump it into the ventricles. Ventricles, pump blood received from the atria out of the heart to the different parts of the body. The human heart works as a double pump: why? The right atrium and right ventricle together pump deoxygenated blood.

The left atrium and left ventricle together pump oxygenated blood. The ventricles are divided or separated by a wall called the interventricular septum. Blood is pumped throughout the four chambers with the help of four heart valves. They ensure that the blood flows in only one direction in the heart. CIRCULATION OF BLOOD IN THE BODY: I) Aorta pumps oxygenated blood away from the heart. Oxygenated blood reaches the cells through arteries and capillaries Cells use up the oxygen present in blood. II) The Vena Cava receives the deoxygenated blood from various parts of the body and takes it to the heart. III) From the heart, the deoxygenated blood is sent to the lungs via the pulmonary artery. IV) In the lungs, blood is reoxgygenated and sent back to the heart via the pulmonary vein. From the heart, the reoxygenated blood is again pumped to different parts of the body via the aorta HEART BEAT: One complete contraction and relaxation of the heart makes up a HEART BEAT or CARDIAC CYCLE. The contraction and relaxation during a heartbeat creates a sound of the heart. Average rate of heart beat of a person is around 72 heartbeats per minute. PULSE: Contraction of Ventricles forces blood into the arteries. The walls of the arteries suddenly expand and relax due to the high pressure of blood being forced into the arteries. This generates a wave of pressure called a Pulse that passes along the arteries.

BLOOD PRESSURE Pressure exerted by the blood on the walls of the arteries is called BLOOD PRESSURE. During contraction, blood is pumped out at maximum high pressure. When the heart relaxes, pressure falls to a minimum. The Maximum and Minimum values together determine the blood pressure. Generally written as 120/80 mm Hg where the numerator (here 120) is the value during contraction and the denominator (here 80) is the value during relaxation. EXERCISE AND A HEALTHY HEART: Exercise is important to maintain a healthy heart. This can be achieved by engaging in activities like brisk walking, jogging, swimming or active outdoor sports for a maximum of 30 minutes per day. Aerobic exercises improve the efficiency of the heart as more oxygen rich blood is made available to the organs of the body. Passive lifestyles and unhealthy foods lead to a deposition of fats in the form of cholesterol in the blood vessels. This increases the blood pressure and may even cause heart attacks. Regular aerobic exercises can prevent this as well as other risks of heart diseases. *********************************************************************