Chapter 1: Humans and Animals (PDF)

Chapter-1 Humans and animals 1.1 Body organs The functions of the major organs in the body are: Brain – the part of the body that thinks and reasons and controls all body functions. Lungs – two spongy, saclike organs in the chest that...

Chapter-1 Humans and animals 1.1 Body organs The functions of the major organs in the body are: Brain – the part of the body that thinks and reasons and controls all body functions. Lungs – two spongy, saclike organs in the chest that provide the body with oxygen and remove carbon dioxide from it. Stomach – the enlarged, saclike portion of the alimentary canal. The stomach starts the digestion of protein and mixes the chewed, swallowed food with digestive juices. Liver- a large, reddish-brown organ located in the upper right abdomen. It stores energy, detoxifies harmful substances, and secretes bile to aid in fat digestion. Small intestine- It is where the digestion of proteins, fats, and carbohydrates is completed, and nutrients are absorbed into the bloodstream. Large intestine- It reabsorbs water from undigested food after nutrients have been removed. It then expels the remaining waste through the anus. Bladder- is where urine is stored. Heart – the circulatory organ that pumps blood carrying food and oxygen to all parts of the body. Kidneys – a pair of organs that maintain proper water and salt balance and regulate blood acidity. They filter the blood of metabolic wastes, which are then excreted as urine. 1 U Aung Tun Oo 1.2 The heart The human heart works like a pump sending blood around the body to keep us alive. It’s a muscle, about the size of our fist, in the middle of the chest tilted slightly to the left. Labels of the heart Labels Description vena cava Carries deoxygenated blood from the body to the heart left atrium Receives oxygenated blood from the lungs left ventricle Region of the heart that pumps oxygenated blood to the body right atrium Segment of the heart that receives deoxygenated blood right ventricle Region of the heart that pumps deoxygenated blood to the lungs pulmonary artery Carries deoxygenated blood to the lungs pulmonary vein Carries oxygenated blood from the lungs valves Heart valves are parts of your heart that act like doors. They open and close to let blood flow from one area of your heart to another. They help ensure that blood moves at the right time and in the correct direction. Aorta The main artery carrying oxygenated blood to all parts of the body 2 U Aung Tun Oo Circulatory system The parts of your circulatory system are: Heart, a muscular organ that pumps blood throughout your body. Blood vessels, which include your arteries, veins and capillaries. Blood, made up of red and white blood cells, plasma and platelets. The main function of the circulatory system is to provide oxygen, nutrients and hormones to muscles, tissues and organs throughout our body. Another part of the circulatory system is to remove waste from cells and organs so our body can dispose of it. There are three main types of blood vessels: Arteries carry blood away from your heart. Veins carry blood back toward your heart. Capillaries, the smallest blood vessels, connect arteries and veins. Double Circulatory System It is called a double circulatory system because blood passes through the heart twice per circuit. The right pump sends deoxygenated blood to the lungs where it becomes oxygenated and returns back to the heart. The left pump sends the newly oxygenated blood around the body. Blood enters the heart: Deoxygenated blood from the body enters into the right atrium of the heart. Blood pumped to lungs: This deoxygenated blood is pumped out of the heart and towards the lungs by the right ventricle. Lungs oxygenate the blood: At the lungs, the deoxygenated blood exchanges carbon dioxide for oxygen. This is how it becomes oxygenated (contains oxygen). Blood returns to the heart: Oxygenated blood returns to the left atrium of the heart. Blood pumped to the body: This oxygenated blood is pumped out of the heart and to the body by the left ventricle. 3 U Aung Tun Oo Blood returns to the heart: The oxygenated blood gives its oxygen to body cells in exchange for carbon dioxide. The blood becomes deoxygenated and returns to the heart. 1.3 Heartbeat and pulse The adult human heart beats about 70 times per minute at rest. The number of beats can be higher or lower than this figure depending on factors like a person’s age, fitness and how active they are. If we feel anxious or scared, our heart beats faster. Each time the heart beats, the heart muscle contracts and relaxes. The pulse is the contraction and relaxation of the arteries each time the heart beats. The pulse is different to the heartbeat. When the ventricles contract, the blood is forced into the arteries. This makes the arteries expand a little as the blood is pushed into them. The elastic walls of the arteries then contract until the next heartbeat forces more blood into them. When you take your pulse you are feeling the expansion of the artery wall, followed by its contraction. This occurs once every heartbeat. The easiest place to feel your pulse is on your wrist. We can use a person’s pulse rate as an indicator of how fit they are. The lower the pulse at rest and after exercise, the fitter the person is. 1.4 The lungs and breathing The respiratory system is the organs and other parts of your body involved in breathing, when you exchange oxygen and carbon dioxide. The respiratory system supplies oxygen to all cells and removes carbon dioxide. Oxygen is absorbed into the blood in the lungs. The oxygen is carried in the blood to all cells of the body where it is used for cellular respiration to release energy from simple food molecules, such as glucose. The process of respiration forms carbon dioxide as a waste product. The carbon dioxide moves from all body cells into the blood and is carried by the blood to the lungs, where it is breathed out. 4 U Aung Tun Oo Breathing Breathing is the movement of air into and out of the lungs. Breathing in is called inhalation. Breathing out is called exhalation. The lungs are inside the chest, surrounded and protected by the ribs. Muscles between the ribs and a sheet of muscle below the lungs, called the diaphragm, make the lungs work. Inhalation takes place as follows: (1) The muscles between the ribs contract and lift the ribs upwards and outwards; (2) The diaphragm muscle contracts and is _ flattened; (3) The volume of the chest increases; (4) The pressure in the chest decreases; and (5) Air is drawn into the lungs. Exhalation takes place as follows: (1) The muscles between the ribs relax and lower the ribs downwards and inwards; (2) The diaphragm muscle relaxes and the diaphragm bulges upwards; (3) The volume of the chest decreases; (4) The pressure in the chest increases; and (5) Air is pushed out of the lungs. 5 U Aung Tun Oo 1.5 The digestive system We need to eat food to get nutrients that supply the body with raw materials and with energy. The job of the digestive system is to absorb nutrients from food. In the digestive system, food is broken down into molecules that are small enough to be absorbed or taken in by the digestive system and then passed into the blood. The nutrients dissolve in the blood and are carried in the bloodstream to all parts of the body. 1. Salivary glands: They are located in the cheeks and under the tongue. They produce saliva to moisten food and secrete enzymes that break down starches in the mouth. 2. Esophagus: A muscular tube that transports food from the throat to the stomach through peristaltic waves. 3. Stomach: A muscular organ that churns food and releases enzymes and acids to aid in digestion. 4. Small intestine: A hollow tract where further digestion occurs, and nutrients are absorbed into the bloodstream. 5. Pancreas: An organ that produces and releases enzymes for digestion in the small intestine. 6. Liver: An organ responsible for processing digested food into useful substances, producing bile for fat digestion, and detoxifying the blood. 7. Gall bladder: A storage sac located beneath the liver that stores and releases bile for fat digestion. 8. Colon: The primary section of the large intestine where water absorption from undigested food occurs. 6 U Aung Tun Oo 9. Rectum: The final segment of the large intestine, responsible for eliminating waste material from the body. The main processes that happen to food in the digestive system are: (1) Ingestion – taking of food into the body through the mouth; (2) Digestion – the breakdown of large food molecules into small soluble food molecules that can be carried in the bloodstream; (3) Absorption – the movement of digested, soluble food molecules through the wall of the digestive system and into the blood; and (4) Egestion – the passing out of food that is not digested in the form of faeces. The digestive system, or alimentary canal, is a one-way tube that passes through the body. It starts at the mouth and ends at the anus. There are two types of digestion: Mechanical digestion and chemical digestion. Mechanical digestion is the physical breakdown of food into smaller pieces. It involves the breaking, crushing and mashing of food. It starts in the mouth where the teeth tear and crush the moistened food into a paste. Chemical digestion is the breakdown of chemical bonds in food molecules to produce smaller molecules. Enzymes are involved in this process. Enzymes are chemicals that break down large food molecules into smaller ones. 7 U Aung Tun Oo 1.6 What do the kidneys do? The kidneys, two bean-shaped organs, are integral to the urinary system, filtering blood and performing several crucial functions. They remove toxins and waste, including urea, creatinine, and acids, from the blood. Every minute, the kidneys filter approximately half a cup of blood, facilitating the body's detoxification process. The urinary system or excretory system. The urinary system comprises four main organs: the kidneys, ureters, urinary bladder, and urethra. These organs work together to filter blood, eliminate waste products, produce urine, and expel urine from the body. It is also referred to as the excretory system since urine contains excreted by-products like urea, uric acid, drugs, excess body fluid, and salts. These functions are crucial for regulating water and electrolyte levels in the blood. What is urinary system? Also called the excretory system, the urinary system acts to remove waste products and maintain the body’s balance of water and various chemical compounds. Urinary system organs Kidneys, ureters, bladder, urethra Function - Excrete waste products from the body - Maintain the body’s water balance - Maintain the body’s salt (electrolyte) balance - Regulates the blood’s acid-base (pH) balance - Regulates the body’s blood volume - Helps to regulate blood pressure - Helps stimulate red blood cell production - Converts Vitamin D to its active form of calcitriol 8 U Aung Tun Oo 1.7 What does the brain do? The human brain is an organ that lives inside the skull. It is about the same size as both of your fists put together and weighs about 1.3kg. It is covered in wrinkles and protected by fluid inside the skull. It’s sometimes nicknamed the ‘grey matter’, because it is grey in colour. The brain is part of the nervous system. Along with the spinal cord, it connects to all the nerves that travel throughout the body. The brain also uses those nerves to tell our muscles what to do. This is how we move. The nervous system The nervous system comprises two main components: 1. Central Nervous System (CNS): Consists of the brain and spinal cord, serving as the body's control center. 2. Peripheral Nervous System (PNS): Comprises nerves branching off from the spinal cord, extending throughout the body to facilitate communication between the brain and other body parts. The nervous system regulates various bodily functions, including movement, breathing, vision, cognition, and more, by transmitting signals between the brain and the rest of the body. It also oversees internal processes such as digestion, respiration, and sexual development. Damage from diseases, accidents, toxins, or aging can impair its functioning. 9 U Aung Tun Oo