Chapter 11: Human Body and Organ System
Solved textbook questions with step-by-step explanations.
Grade 8 Q&A: Chapter 11: Human Body and Organ Systems
Welcome to the Questions and Answers section for Grade 8 Science, Chapter 11: "Human Body and Organ Systems." This chapter explores the intricate organization of the human body, from cells to organ systems, and delves into the structure and vital functions of major systems such as the digestive, respiratory, circulatory, excretory, nervous, skeletal, and muscular systems.
Important Questions and Answers
Q1: List the levels of organization in the human body, starting from the basic unit.
Answer: The levels of organization in the human body are:
Cells → Tissues → Organs → Organ Systems → Organism
Q2: What is the primary function of the Digestive System? List its main organs.
Answer: The primary function of the Digestive System is to break down complex food into simpler substances that can be absorbed and utilized by the body.
Main organs: Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large Intestine, Anus. (Associated glands: Salivary glands, Liver, Pancreas).
Q3: Explain the process of 'Digestion' and 'Absorption'.
Answer:
- Digestion: The process of breaking down complex food substances into simpler, soluble forms that the body can use. It involves both mechanical (chewing, churning) and chemical (enzyme action) processes.
- Absorption: The process by which digested nutrients pass from the small intestine into the bloodstream or lymphatic system to be transported to various body cells.
Q4: What is the main function of the Respiratory System? List its main organs.
Answer: The main function of the Respiratory System is the exchange of gases (taking in oxygen and giving out carbon dioxide) between the body and the environment.
Main organs: Nose, Pharynx, Larynx, Trachea, Bronchi, Lungs, Diaphragm.
Q5: Describe the process of 'Gaseous Exchange' in the lungs.
Answer: Gaseous exchange occurs in the alveoli (tiny air sacs) of the lungs. Oxygen from the inhaled air diffuses from the alveoli into the blood capillaries surrounding them. Simultaneously, carbon dioxide, a waste product from the body, diffuses from the blood capillaries into the alveoli to be exhaled.
Q6: What are the main components of the Circulatory System?
Answer: The main components of the Circulatory System are the Heart, Blood, and Blood Vessels (Arteries, Veins, Capillaries).
Q7: Differentiate between Arteries and Veins.
Answer:
- Arteries: Carry oxygenated blood away from the heart to various body parts (except pulmonary artery). They have thick, elastic walls.
- Veins: Carry deoxygenated blood from various body parts back to the heart (except pulmonary vein). They have thinner walls and often have valves to prevent backflow of blood.
Q8: What is the function of 'Capillaries' in the circulatory system?
Answer: Capillaries are tiny, thin-walled blood vessels that connect arteries and veins. Their primary function is the exchange of gases (oxygen, carbon dioxide), nutrients, hormones, and waste products between the blood and the body tissues.
Q9: What is the main function of the Excretory System? List its main organs.
Answer: The main function of the Excretory System is to remove metabolic waste products and excess substances (like urea, excess salts, and water) from the body.
Main organs: Kidneys, Ureters, Urinary Bladder, Urethra.
Q10: Explain the role of 'Kidneys' in the human body.
Answer: Kidneys are vital organs in the excretory system. Their primary role is to filter the blood, removing waste products like urea, excess salts, and excess water to form urine. They also play a crucial role in maintaining fluid balance, electrolyte balance, and blood pressure.
Q11: What are the main organs of the Nervous System? What is its overall function?
Answer: The main organs of the Nervous System are the Brain, Spinal Cord, and Nerves. Its overall function is to control and coordinate all body activities, enabling communication between different parts of the body and allowing the body to respond to internal and external stimuli.
Q12: List three functions of the Skeletal System.
Answer:
- Provides framework and support to the body.
- Protects delicate internal organs (e.g., brain, heart, lungs).
- Along with muscles, enables movement.
- Produces blood cells (in bone marrow).
- Stores minerals (calcium, phosphorus).
Q13: Name the three types of muscles in the Muscular System and state their basic functions.
Answer:
- Skeletal Muscles: Attached to bones, responsible for voluntary movements (e.g., walking, lifting).
- Smooth Muscles: Found in internal organs, responsible for involuntary movements (e.g., digestion, blood vessel constriction).
- Cardiac Muscles: Found only in the heart, responsible for the involuntary pumping of blood.
Q14: What is the function of the Endocrine System? What are 'hormones'?
Answer: The Endocrine System consists of glands that produce and secrete hormones. Hormones are chemical messengers secreted directly into the bloodstream that travel to target organs and regulate various body functions like growth, metabolism, reproduction, and mood.
Q15: Why is 'Coordination Among Organ Systems' important?
Answer: Coordination among organ systems is crucial because no single system can function in isolation. They are interdependent and work together to maintain homeostasis (a stable internal environment) and ensure the overall survival and proper functioning of the entire organism. For example, the digestive system provides nutrients, the respiratory system provides oxygen, and the circulatory system transports both to all cells, all coordinated by the nervous and endocrine systems.
Q16: What is the role of the diaphragm in respiration?
Answer: The diaphragm is a large, dome-shaped muscle located at the base of the lungs. During inhalation, it contracts and moves downwards, increasing the volume of the chest cavity and drawing air into the lungs. During exhalation, it relaxes and moves upwards, decreasing the chest cavity volume and pushing air out of the lungs.
Q17: List the main components of blood and their functions.
Answer:
- Plasma: The liquid part of blood, transports nutrients, hormones, and waste.
- Red Blood Cells (RBCs): Contain hemoglobin, transport oxygen.
- White Blood Cells (WBCs): Part of the immune system, fight infections.
- Platelets: Involved in blood clotting to stop bleeding.
Q18: What is the difference between voluntary and involuntary actions? Give an example of each.
Answer:
- Voluntary Actions: Actions that are under the conscious control of the brain. Example: Walking, lifting an object, writing.
- Involuntary Actions: Actions that are not under conscious control and occur automatically. Example: Heartbeat, breathing, digestion, blinking.
Q19: How does the skeletal system protect internal organs? Give examples.
Answer: The skeletal system protects delicate internal organs by forming a strong bony framework around them. For example, the skull protects the brain, the rib cage protects the heart and lungs, and the vertebral column (backbone) protects the spinal cord.
Q20: What is the role of the liver and pancreas in the digestive system?
Answer:
- Liver: Produces bile, which helps in the digestion and absorption of fats. It also detoxifies harmful substances and metabolizes nutrients.
- Pancreas: Produces digestive enzymes (e.g., amylase, lipase, trypsin) that break down carbohydrates, fats, and proteins in the small intestine. It also produces hormones like insulin and glucagon.
Q21: What is 'Assimilation' in the context of the digestive system?
Answer: Assimilation is the process by which the absorbed nutrients are transported to various cells of the body and are utilized for energy, growth, and repair.
Q22: Why is the heart considered a muscular pumping organ?
Answer: The heart is considered a muscular pumping organ because it is primarily composed of cardiac muscle tissue. Its rhythmic contractions and relaxations continuously pump blood throughout the body via the circulatory system, ensuring that oxygen and nutrients reach all cells and waste products are removed.
Q23: What are 'joints' in the skeletal system? What is their function?
Answer: Joints are points where two or more bones meet. Their function is to allow movement between bones, providing flexibility and enabling various actions like bending, rotating, and extending limbs.
Q24: How does the nervous system enable communication within the body?
Answer: The nervous system enables communication through the transmission of electrical signals called nerve impulses. Nerves carry these impulses rapidly from sensory organs to the brain and spinal cord for processing, and then from the brain and spinal cord to muscles and glands, coordinating responses and actions.
Q25: Briefly describe the function of the Reproductive System.
Answer: The Reproductive System is responsible for the production of offspring, ensuring the continuation of the species. It involves the production of gametes (sperm in males, egg in females) and hormones necessary for the reproductive process.
Exercise Solutions (From Screenshot Page 82)
Q1: Fill in the blanks.
- The basic structural and functional unit of life is the cell.
- A group of similar cells performing a specific function forms a tissue.
- A group of different tissues working together forms an organ.
- A group of organs working together to perform a major function forms an organ system.
- The process of breaking down complex food into simpler substances is called digestion.
- The process of taking in oxygen and giving out carbon dioxide is called respiration.
- The organ that pumps blood throughout the body is the heart.
- The blood vessels that carry oxygenated blood away from the heart are arteries.
- The blood vessels that carry deoxygenated blood back to the heart are veins.
- The organ that filters blood to remove waste products is the kidney.
- The control center of the human body is the brain.
- The framework of the body is formed by the skeletal system.
- Muscles responsible for voluntary movements are skeletal muscles.
- Glands that produce hormones belong to the endocrine system.
Q2: Match the pairs.
(Note: As an AI, I cannot create interactive matching. I will provide the correct pairs.)
- Digestive System - Stomach
- Respiratory System - Lungs
- Circulatory System - Heart
- Excretory System - Kidneys
- Nervous System - Brain
- Skeletal System - Bones
- Muscular System - Muscles
- Endocrine System - Hormones
Q3: Give scientific reasons.
- The small intestine has a large surface area for absorption.
Reason: The small intestine has a large internal surface area due to the presence of millions of tiny, finger-like projections called villi, and further microscopic folds on these villi called microvilli. This extensive surface area is crucial because it maximizes the efficiency of nutrient absorption, allowing the digested food to quickly pass into the bloodstream and lymphatic system for distribution throughout the body. - The walls of arteries are thick and elastic.
Reason: Arteries carry oxygenated blood directly from the heart to various parts of the body. The heart pumps blood with high pressure, so the thick and elastic walls of arteries are necessary to withstand this high pressure and prevent them from bursting. Their elasticity also helps maintain blood pressure and ensures continuous blood flow. - The brain is protected by the skull.
Reason: The brain is an extremely delicate and vital organ that controls all bodily functions, thoughts, and emotions. Any damage to the brain can have severe and irreversible consequences. Therefore, it is protected by the strong, bony structure of the skull, which acts as a protective casing, shielding it from external impacts and injuries. - Our body needs a skeletal system.
Reason: Our body needs a skeletal system for several crucial reasons:- It provides the main framework and structural support to the body, giving it shape and posture.
- It protects delicate internal organs, such as the brain (by the skull), heart and lungs (by the rib cage), and spinal cord (by the vertebral column).
- It works in conjunction with the muscular system to facilitate movement.
- Bone marrow within bones produces blood cells.
- Bones serve as a reservoir for essential minerals like calcium and phosphorus.
Q4: Answer the following questions.
- Explain the process of digestion in the human body.
Answer: Digestion begins in the mouth, where food is chewed (mechanical digestion) and mixed with saliva (chemical digestion by salivary amylase). It then passes through the esophagus to the stomach, where it is churned and mixed with gastric juices (mechanical and chemical digestion). From the stomach, partially digested food moves to the small intestine, where most digestion and absorption occur with the help of enzymes from the pancreas and bile from the liver. Undigested food then passes to the large intestine, where water is absorbed, and finally, undigested waste is eliminated from the body through the anus. - Explain the process of respiration in the human body.
Answer: Respiration involves two main processes: inhalation and exhalation.- Inhalation: When we breathe in, the diaphragm contracts and moves downwards, and the rib cage moves upwards and outwards. This increases the volume of the chest cavity, creating lower pressure inside the lungs, causing air (rich in oxygen) to rush into the lungs through the nose, pharynx, larynx, trachea, and bronchi.
- Exhalation: When we breathe out, the diaphragm relaxes and moves upwards, and the rib cage moves downwards and inwards. This decreases the volume of the chest cavity, increasing pressure inside the lungs, forcing air (rich in carbon dioxide) out of the body.
- Explain the structure and function of the circulatory system.
Answer: The circulatory system consists of the heart, blood, and blood vessels (arteries, veins, capillaries).- Heart: A muscular pumping organ that continuously circulates blood throughout the body.
- Blood: A fluid connective tissue composed of plasma, red blood cells (transport oxygen), white blood cells (fight infection), and platelets (help in clotting).
- Blood Vessels:
- Arteries: Carry oxygenated blood away from the heart.
- Veins: Carry deoxygenated blood back to the heart.
- Capillaries: Tiny vessels where the exchange of gases, nutrients, and waste products occurs between blood and body tissues.
- Explain the structure and function of the excretory system.
Answer: The excretory system is responsible for removing metabolic waste products from the body. Its main organs are:- Kidneys: Two bean-shaped organs that filter blood to remove waste products like urea, excess salts, and water, forming urine.
- Ureters: Two tubes that carry urine from the kidneys to the urinary bladder.
- Urinary Bladder: A muscular sac that temporarily stores urine.
- Urethra: A tube that carries urine from the bladder out of the body.
Q5: Differentiate between.
- Arteries and Veins
Feature Arteries Veins Function Carry blood away from the heart Carry blood towards the heart Blood Type Mostly oxygenated (except pulmonary artery) Mostly deoxygenated (except pulmonary vein) Wall Thickness Thick and elastic Thin and less elastic Valves Absent (except at heart exit) Present (to prevent backflow) Pressure High pressure Low pressure - Inhalation and Exhalation
Feature Inhalation Exhalation Diaphragm Contracts and moves downwards Relaxes and moves upwards Rib Cage Moves upwards and outwards Moves downwards and inwards Chest Cavity Volume Increases Decreases Air Movement Air enters lungs Air leaves lungs Gas Exchange Oxygen enters blood Carbon dioxide leaves blood
References
- Maharashtra State Board Science and Technology Standard Eight Textbook (Specific Edition/Year) - Chapter 11: Human Body and Organ Systems.
- Maharashtra State Board 8th Standard Science Syllabus.
- Balbharati Science and Technology Textbook.