Human Organ Systems: Exercise Solutions Guide
This guide covers Samacheer Kalvi 6th Science Term 2, Chapter 6 — Human Organ Systems. Solve each exercise on your own first, then check your answers below.
I. Choose the Appropriate Answer (MCQs)
Q1. Circulatory system transports these throughout the body: (a) Oxygen (b) Nutrient (c) Hormones (d) All of these
The circulatory system is the body's transport network — it carries oxygen, nutrients, and hormones to every cell and removes waste products.
Q2. Main organ of respiration in human body is: (a) Stomach (b) Spleen (c) Heart (d) Lungs
Lungs are the primary organs where gas exchange occurs — oxygen enters the blood and carbon dioxide is expelled.
Q3. Breakdown of food into smaller molecules in our body is known as: (a) Muscle contraction (b) Respiration (c) Digestion (d) Excretion
Digestion is the process of converting complex food substances into simpler, absorbable forms.
Additional MCQs
Q4. A group of organs that work together to perform a particular function is known as ________ (a) Skeletal system (b) Muscular system (c) Nervous system (d) Organ system
Q5. ________ is the largest and strongest bone in the human face. (a) Hyoid bone (b) Stapes (c) Cranial bones (d) Lower jaw bone
Q6. The heart is surrounded by a double-layered membrane called: (a) Pleura (b) Alveolar membrane (c) Pericardium (d) Iris
Q7. ________ is a major organ for digestion of food materials. (a) Heart (b) Oesophagus (c) Stomach (d) Kidney
Q8. The ________ is a complex organ which is placed inside the cranium. (a) Kidney (b) Heart (c) Lungs (d) Brain
Q9. Skin helps us to synthesize ________ using sunlight. (a) Vitamin A (b) Vitamin B (c) Vitamin C (d) Vitamin D
Q10. ________ gland is located in the neck region. (a) Pituitary (b) Thyroid (c) Adrenal (d) Thymus
Q11. Pituitary gland is located at ________ in our body. (a) Neck region (b) Base of brain (c) Abdomen region (d) Above the kidney
Q12. The functional units of the kidney are called ________ (a) Nephrons (b) Neuron (c) Bladder (d) Urethra
II. Fill in the Blanks
1. A group of organs together make up an organ system.
2. The part of the skeleton that protects the brain is skull.
3. The process by which the body removes waste is Excretion.
4. The skin is the largest sense organ in our body.
5. The endocrine glands produce chemical substances called hormones.
Additional Fill in the Blanks
6. The adult human skeletal system consists of 206 bones.
7. Ligaments help in connecting bone to bone.
8. Vertebral column is formed by a number of serially arranged small bones called vertebrae.
9. The rib cage is made up of 12 pairs of curved flat rib bones.
10. The digestive gland associated with alimentary canal is salivary gland.
11. Lungs are located within the chest cavity.
12. The lungs are covered by a double layered pleura.
13. The heart is four chambered.
14. The heart is surrounded by a double layered membrane called pericardium.
15. Red Blood Corpuscles are produced in the bone marrow.
16. Nervous system is composed of neurons or nerve cells.
17. Brain is the controlling centre of the body.
18. The outer ear in human beings is made up of an external flap called pinna.
19. Adrenal gland is located above the kidney.
20. Our body contains 70 % of water.
21. Our stomach consists of Hydrochloric acid.
III. True or False (with Corrections)
Q1. Blood is produced in the bone marrow.
False. ✓ — Red Blood Corpuscles (RBCs) are produced in the bone marrow. Blood as a whole includes plasma, RBCs, WBCs, and platelets — it is not entirely "produced" in the bone marrow.
Q2. All the waste products of the body are excreted through the circulatory system.
False. ✓ — All the waste products of the body are excreted through the excretory system, not the circulatory system. The circulatory system only transports waste to the excretory organs.
Q3. The other name of food pipe is alimentary canal.
False. ✓ — The other name of food pipe is oesophagus. The alimentary canal refers to the entire digestive tract from mouth to anus, not just the food pipe.
Q4. Thin tube like structures which are the component of circulatory system are called blood vessels.
False. ✓ — The thin tube-like structures which are the component of circulatory system are called blood capillaries. Blood vessels is a broader term that includes arteries, veins, and capillaries.
Q5. The brain, the spinal cord and nerves form the nervous system.
True. ✓ — The nervous system is composed of the brain, spinal cord, and nerves.
Additional True or False
Q6. The nervous system consists of bones, cartilages and joints.
False. ✓ — The skeletal system consists of bones, cartilages, and joints — not the nervous system.
Q7. Lower jaw bone is the smallest and strongest bone in the human face.
False. ✓ — Lower jaw bone is the largest and strongest bone in the human face, not the smallest.
Q8. The smallest bone in our body is stapes.
True. ✓ — Stapes (stirrup bone in the ear) is the smallest bone in the human body.
Q9. Intake of oxygen from the air and releasing of carbon dioxide from the lungs occur through nostrils is called internal respiration.
False. ✓ — This process is called external respiration. Internal respiration refers to the exchange of gases between blood and body cells at the tissue level.
Q10. The walls of the heart are made up of cardiac muscle.
True. ✓ — The heart walls consist of cardiac muscle tissue, which contracts rhythmically and involuntarily.
Q11. Blood is a fluid connective tissue.
True. ✓ — Blood is classified as a fluid connective tissue because it has cells (RBCs, WBCs, platelets) suspended in a fluid matrix (plasma).
Q12. Kidney is located in the thoracic cavity between the two lungs.
False. ✓ — The heart is located in the thoracic cavity between the two lungs. Kidneys are located in the abdominal cavity.
Q13. A resting person usually has a pulse rate between 72 to 80 beats per minute.
True. ✓ — The normal resting pulse rate for a healthy person is 72–80 beats per minute.
Q14. Pulmonary artery carries blood from the lungs to the left atrium.
False. ✓ — Pulmonary vein carries blood from the lungs to the left atrium. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
Q15. Heart forms an effective barrier against infection by microbes and pathogens.
False. ✓ — Skin forms an effective barrier against infection by microbes and pathogens, not the heart.
Q16. The nitrogenous wastes are removed from the body by the endocrine system.
False. ✓ — Nitrogenous wastes are removed from the body by the excretory system, not the endocrine system.
IV. Match the Following
| Column I | Column II |
|---|---|
| 1. Ear | Sound |
| 2. Skeletal System | Protection of internal organs |
| 3. Diaphragm | Flat muscle |
| 4. Heart | Cardiac muscle |
| 5. Lungs | Air sacs |
V. Arrange in Correct Sequence
Q1. Arrange the parts of the digestive system in correct order: Stomach, Large intestine, Oesophagus, Pharynx, Mouth, Small Intestine, Rectum, Anus
Mouth → Pharynx → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus
Q2. Arrange the parts of the excretory system in correct sequence: Urethra, Ureter, Urinary Bladder, Kidney
Kidney → Ureter → Urinary Bladder → Urethra
VI. Analogy
Q1. Arteries : Carry blood from the heart :: ________ : Carry blood to the heart
Q2. Lungs : Respiratory system :: ________ : Circulatory system
Q3. Enzymes : Digestive glands :: ________ : Endocrine glands
Additional Analogy
Q4. Skull protects : Brain. Rib cage protects : ________
Q5. The smallest bone of our body : Stapes. The longest bone of our body : ________
Q6. A newborn baby has bones : More than 300. An adult has bones : ________
Q7. Skeletal muscle : Muscle of arm. Cardiac muscle : ________
Q8. Heart : Pericardium membrane. Lungs : ________
Q9. Carries blood from right ventricle to lungs : Pulmonary artery. Carries blood from the lungs to left atrium : ________
Q10. Carry oxygenated blood : Arteries. Carry deoxygenated blood : ________
Q11. Neurons : Nervous system. Nephrons : ________
VII. Very Short Answers
Q1. Write about skeletal system.
The skeletal system consists of bones, cartilages, and joints. Bones provide a framework for the body. Along with muscles, they help in movements such as walking, running, chewing, and dancing.
Q2. Write the functions of epiglottis.
The epiglottis is a flap-like structure that prevents the entry of food into the windpipe (trachea) during swallowing, directing food to the oesophagus instead.
Q3. What are the three types of blood vessels?
The three types of blood vessels are: 1. Arteries — carry blood away from the heart 2. Veins — carry blood towards the heart 3. Capillaries — thin vessels connecting arteries and veins where gas exchange occurs
Q4. Define the term "Trachea."
The trachea, commonly called the windpipe, is a tube supported by cartilaginous rings that connects the pharynx and larynx to the lungs, allowing the passage of air. It divides into the right and left bronchi that enter the lungs.
Q5. Write any two functions of digestive system.
1. Conversion of complex food substances into simple, absorbable forms. 2. Absorption of digested food into the blood.
Q6. Name the important parts of the eye.
The important parts of the eye are: cornea, iris, lens, and pupil.
Q7. Name the five important sense organs.
The five sense organs are: 1. Eyes (sight) 2. Ears (hearing) 3. Nose (smell) 4. Tongue (taste) 5. Skin (touch)
VIII. Short Answers
Q1. Write a short note on rib cage.
The rib cage is made up of 12 pairs of curved, flat rib bones. It forms a protective cage around the chest cavity and shields delicate vital organs such as the heart and lungs from injury.
Q2. List out the functions of the human skeleton.
1. Gives shape to the body. 2. Provides a framework that supports the body. 3. Along with muscles, helps in movements such as walking, running, chewing, and dancing. 4. Protects soft internal organs (e.g., skull protects brain, rib cage protects heart and lungs).
Q3. Differentiate between voluntary muscles and involuntary muscles.
| Feature | Voluntary Muscles | Involuntary Muscles |
|---|---|---|
| Control | Can be controlled by our will | Cannot be controlled by our will |
| Location | Attached to bones | Walls of digestive tract, urinary bladder, arteries, and other internal organs |
| Example | Muscles of the arm | Muscles of the stomach wall |
Additional Short Answers
Q4. List the major organ systems of our body.
The eight major organ systems are: 1. Skeletal system 2. Muscular system 3. Digestive system 4. Respiratory system 5. Circulatory system 6. Nervous system 7. Excretory system 8. Endocrine system
Q5. Explain axial skeleton.
The axial skeleton forms the upright axis of the body. It includes the skull, vertebral column, and rib cage. It provides central support and protects vital organs.
Q6. What are the three types of muscles?
1. Skeletal muscles — attached to bones, voluntary control 2. Smooth muscles — found in walls of internal organs, involuntary 3. Cardiac muscles — found in the walls of the heart, involuntary and rhythmic
Q7. How do muscles work?
Muscles can only pull and cannot push. Two muscles are required to move a bone at a joint. When one muscle contracts, the other relaxes. For example, to raise the lower arm, the biceps contract and the triceps relax. To lower the arm, the triceps contract and the biceps relax.
Q8. List the parts of the digestive system.
Mouth → Buccal cavity → Pharynx → Oesophagus → Stomach → Small intestine → Large intestine → Anus
Q9. List the glands associated with digestion.
1. Salivary glands 2. Gastric glands 3. Liver 4. Pancreas 5. Intestinal glands
Q10. List the parts of the respiratory system.
Nostrils → Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Lungs
Q11. What is internal respiration?
The circulatory system transports oxygen and carbon dioxide to and from all parts of the body. Haemoglobin in red blood cells carries oxygen and carbon dioxide. This exchange of gases between blood and body cells at the tissue level is called internal respiration.
Q12. Define blood.
Blood is a fluid connective tissue of red colour. It consists of:
- Plasma — the fluid part
- Red Blood Corpuscles (RBCs) — carry oxygen; produced in bone marrow
- White Blood Corpuscles (WBCs) — fight disease
- Blood Platelets — help in clotting
Q13. What is pulse rate?
The number of heart beats per minute is called the pulse rate. A resting person typically has a pulse rate of 72–80 beats per minute.
Q14. Name the three regions of the brain.
1. Fore brain 2. Mid brain 3. Hind brain
Q15. List the endocrine glands found in our body.
1. Pituitary gland 2. Pineal gland 3. Thyroid gland 4. Thymus gland 5. Pancreas (Islets of Langerhans) 6. Adrenal gland 7. Gonads
IX. Detailed Answers
Q1. List out the functions of Endocrine system and Nervous system.
Endocrine System:
- Regulates various functions of the body and maintains the internal environment (homeostasis).
- Endocrine glands produce chemical substances called hormones that control various activities.
- Example: Growth hormone controls growth.
- Adrenalin hormone acts at the time of fear and stress.
- Hormones are carried by blood to their target organs.
Nervous System: 1. Sensory input — Conduction of signals from sensory receptors (eyes, ears, skin, etc.) to the brain and spinal cord. 2. Integration — Interpretation of sensory signals and formulation of appropriate responses. 3. Motor output — Conduction of signals from the brain and spinal cord to effectors such as muscles and glands.
Together, both systems coordinate and regulate all body activities.
Q2. Label the diagram of the urinary system and answer the following:
A. Which organ removes extra salts and water?
Kidney — it filters blood and removes extra salts, water, and nitrogenous waste.
B. Where is the urine stored?
Urinary bladder — an expandable muscular sac that stores urine until it is discharged.
C. What is the tube through which urine exits the body?
Urethra — the tube through which urine is excreted out of the body.
D. What are the tubes that transfer urine from kidneys to the urinary bladder called?
Ureters — two thin tubes that carry urine from each kidney to the urinary bladder.
Additional Detailed Answers
Q3. (a) How do muscles work? (b) How is the circulatory system important for human life?
(a) How muscles work:
Muscles can only pull and cannot push. Two muscles work as a pair to move a bone at a joint. When one muscle contracts (becomes shorter), the other relaxes (becomes longer).
Example: To move the lower arm up and down:
- Raising the arm: Biceps contract and become short; triceps relax and stretch.
- Lowering the arm: Triceps contract and become short; biceps relax and stretch.
(b) Importance of the circulatory system:
1. It consists of the heart, blood vessels, and blood. 2. Transports respiratory gases (oxygen and carbon dioxide), nutrients, hormones, and waste materials throughout the body. 3. Protects the body from harmful pathogens through white blood cells. 4. Regulates body temperature by distributing heat. 5. The heart pumps blood continuously throughout our lifetime to sustain all body functions.
Q4. Tabulate the names of glands of the endocrine system and their locations.
| Gland | Location |
|---|---|
| Pituitary gland | Base of the brain |
| Pineal gland | Base of the brain |
| Thyroid gland | Neck |
| Thymus gland | Chest |
| Pancreas (Islets of Langerhans) | Abdomen |
| Adrenal gland | Above the kidney |
| Gonads | Pelvic cavity |
Q5. List the parts of the excretory system and write their functions.
1. Renal artery — Brings blood containing oxygen and urea from the aorta to the kidneys. 2. Renal vein — Carries filtered blood from the kidneys back to the inferior vena cava. 3. Kidneys — Filter blood, regulate chemical composition of body fluids, and remove nitrogenous waste. 4. Ureters — Carry urine from the kidneys to the urinary bladder. 5. Urinary bladder — An expandable muscular sac that stores urine until discharge. 6. Urethra — The tube through which urine is discharged from the body; surrounded by muscles that allow voluntary control of urination.
Q6. Describe the construction of the eye.
Eyes help us see things around us — their colour, shape, size, and whether they are near or far, moving or at rest. The eyelids and eyelashes protect the eyes. The eye has three main parts:
1. Cornea — The transparent outer layer that allows light to enter the eye. 2. Iris — The coloured part of the eye that controls the size of the pupil and regulates the amount of light entering. 3. Pupil — The dark opening in the centre of the iris through which light passes to the lens and retina.
X. Higher Order Thinking Skills (HOTS)
Q1. What will happen if the diaphragm shows no movement?
The diaphragm is the primary muscle of breathing. Its contraction and relaxation expand and contract the lungs, creating a vacuum that draws air in and pushes it out. If the diaphragm stops moving:
- The lungs cannot expand or contract.
- Air cannot be drawn into or expelled from the lungs.
- Breathing stops completely.
- The person will die due to lack of oxygen.
Q2. Why is the heart divided into two halves by a thick muscular wall?
The heart is divided into two halves (right and left) by a thick muscular wall called the septum to:
- Prevent mixing of oxygenated blood (from the lungs) with deoxygenated blood (from the body).
- Ensure that oxygen-rich blood is efficiently pumped to the body and oxygen-poor blood is sent to the lungs for oxygenation.
- This separation makes the circulatory system more efficient in delivering oxygen.
Q3. Why do we sweat more in summer?
Sweating is the body's natural mechanism to maintain a constant internal temperature (thermoregulation). In summer:
- The external temperature is higher, so the body produces more sweat.
- When sweat evaporates from the skin surface, it absorbs heat and cools the body.
- This evaporative cooling prevents overheating and keeps body temperature around 37°C.
- Hence, we sweat more in summer to dissipate excess heat.
Q4. Why do we hiccup and cough sometimes when we swallow food?
The epiglottis is a flap-like structure that normally closes the entrance to the windpipe (trachea) during swallowing, directing food to the oesophagus. When we eat in a hurry:
- The epiglottis gets less time to close the windpipe completely.
- Some food particles may enter the windpipe.
- This creates a hindrance to air movement and irritates the respiratory passage.
- The body responds with a reflex cough or hiccup to expel the foreign particles and clear the airway.
Common Mistakes
1. Confusing "oesophagus" with "alimentary canal" — The oesophagus (food pipe) is only one part of the alimentary canal. The alimentary canal is the entire digestive tract from mouth to anus.
2. Saying "blood is produced in bone marrow" — Only Red Blood Corpuscles (RBCs) are produced in the bone marrow. Blood also contains plasma, WBCs, and platelets, which are not all produced there.
3. Mixing up arteries and veins — Arteries carry blood away from the heart (usually oxygenated), while veins carry blood towards the heart (usually deoxygenated). The exception: pulmonary artery carries deoxygenated blood, and pulmonary vein carries oxygenated blood.
4. Confusing internal and external respiration — External respiration is the exchange of gases between the body and the environment (breathing). Internal respiration is the exchange of gases between blood and body cells at the tissue level.
5. Saying "kidney is in the thoracic cavity" — The kidney is in the abdominal cavity. It is the heart that is located in the thoracic cavity between the two lungs.
6. Confusing "blood vessels" with "blood capillaries" — Blood vessels is a broad term (arteries + veins + capillaries). The thin tube-like structures specifically are capillaries.
7. Mixing up endocrine and excretory systems — The endocrine system produces hormones for regulation. The excretory system removes nitrogenous waste. These are separate systems with different functions.
Exam Checklist
- [ ] I can list all eight major organ systems and name their main organs.
- [ ] I can trace the path of food through the digestive system (Mouth → Anus).
- [ ] I can trace the path of air through the respiratory system (Nostrils → Lungs).
- [ ] I can trace the path of urine through the excretory system (Kidney → Urethra).
- [ ] I can explain the difference between voluntary and involuntary muscles with examples.
- [ ] I can distinguish between arteries, veins, and capillaries.
- [ ] I can explain why the heart has a septum (to prevent mixing of oxygenated and deoxygenated blood).
- [ ] I can list the endocrine glands and their locations.
- [ ] I can explain the three functions of the nervous system: sensory input, integration, motor output.
- [ ] I can explain the role of the diaphragm in breathing.
- [ ] I can explain the function of the epiglottis and why we hiccup/cough when eating in a hurry.
- [ ] I can identify the difference between internal and external respiration.
- [ ] I can name the parts of the eye (cornea, iris, pupil, lens) and the five sense organs.
- [ ] I can list the components of blood (plasma, RBCs, WBCs, platelets) and state that blood is a fluid connective tissue.
- [ ] I can explain the analogy patterns: arteries vs veins, enzymes vs hormones, neurons vs nephrons.