Samacheer Kalvi Class 9 Science Solutions Chapter 20 Organ Systems in Animals

I. Choose the Correct Answer:

 

Question 1. Which of the following is not a salivary gland?
(a) Sublingual
(b) Lachrymal
(c) Submaxillary
(d) Parotid
Answer: (b) Lachrymal
In simple words: Lachrymal glands produce tears, not saliva. They are part of the eye's tear system.

🎯 Exam Tip: Remember the three major pairs of salivary glands: parotid, submandibular (submaxillary), and sublingual. Lachrymal glands are associated with tear production.

 

Question 2. Stomach of human beings mainly digests
(a) carbohydrates
(b) proteins
(c) fat
(d) sucrose
Answer: (b) proteins
In simple words: The stomach primarily digests proteins. It uses enzymes like pepsin to break down proteins into smaller peptides, beginning the digestion process for proteins.

🎯 Exam Tip: While some digestion of other nutrients might occur, protein digestion is the most significant chemical process in the stomach, thanks to pepsin and hydrochloric acid.

 

Question 3. To prevent the entry of food into the trachea, the opening is guarded by
(a) epiglottis
(b) glottis
(c) hard palate
(d) soft palate
Answer: (a) epiglottis
In simple words: The epiglottis acts like a lid over your windpipe. When you swallow, it closes so food goes down the right pipe, not into your lungs.

🎯 Exam Tip: Understanding the function of the epiglottis is key to explaining how choking is prevented during swallowing.

 

Question 4. Which of the following food types is mainly broken down by bile?
(a) proteins
(b) sugar
(c) fats
(d) carbohydrates
Answer: (c) fats
In simple words: Bile helps break down fats into tiny drops in the small intestine, so the body can digest them better.

🎯 Exam Tip: Remember that bile emulsifies fats, meaning it physically breaks them into smaller droplets, increasing the surface area for enzyme action, but it does not chemically digest them itself.

 

Question 5. The structural and functional unit of the kidney is
(a) villi
(b) liver
(c) nephron
(d) ureter
Answer: (c) nephron
In simple words: Nephrons are the tiny working parts inside the kidney. They clean the blood and make urine.

🎯 Exam Tip: The nephron is crucial for filtering blood, reabsorbing useful substances, and excreting waste, making it the fundamental unit of kidney function.

 

Question 6. Which one of the following substance is not a constituent of sweat?
(a) Urea
(b) Protein
(c) Water
(d) Salt
Answer: (b) Protein
In simple words: Sweat is mostly water with some salt and waste. Proteins are too big to come out in sweat.

🎯 Exam Tip: Sweat's primary role is thermoregulation, and its composition reflects this, mainly containing water, salts, and small amounts of metabolic wastes like urea.

 

Question 7. The passage meant for transporting urine and sperms in male is
(a) ureter
(b) urethra
(c) vas deferens
(d) scrotum
Answer: (c) vas deferens
In simple words: The vas deferens is a tube in males that carries sperm from one place to another before it leaves the body.

🎯 Exam Tip: Be precise in distinguishing between tubes that carry urine, sperm, or both. The vas deferens is specifically for sperm transport.

 

Question 8. Which of the following is not a part of female reproductive system?
(a) Ovary
(b) Uterus
(c) Testes
(d) Fallopian tube
Answer: (c) Testes
In simple words: Testes are found in males, not females. Ovaries, the uterus, and fallopian tubes are all parts of the female body.

🎯 Exam Tip: Clearly know the main organs of both the male and female reproductive systems to avoid confusion in such identification questions.

II. Fill in the Blanks:

 

Question 1. The opening of the stomach into the intestine is called pylorus.
Answer: The pylorus is a muscular valve at the bottom of the stomach that controls the flow of partially digested food (chyme) into the small intestine. It ensures that food is released slowly for proper digestion.
In simple words: The pylorus is like a gate at the bottom of the stomach. It lets food go into the intestine bit by bit.

🎯 Exam Tip: The pylorus acts as a sphincter, regulating the gastric emptying process and preventing too much acid from entering the small intestine at once.

 

Question 2. The muscular and sensory organ which helps in mixing the food with saliva is tongue.
Answer: The tongue is a strong muscle in the mouth that helps with tasting, chewing, and swallowing food. It also plays a key role in mixing food with saliva to form a soft bolus, making it easier to swallow.
In simple words: The tongue is a muscle in your mouth that helps you taste, chew, and mix food with spit.

🎯 Exam Tip: Beyond taste and mixing, remember the tongue's role in initiating the swallowing reflex and forming speech sounds.

 

Question 3. Bile secreted by the liver is stored temporarily in gall bladder.
Answer: The gall bladder is a small organ located under the liver that stores and concentrates bile. Bile is a digestive fluid produced by the liver that helps in the digestion of fats in the small intestine.
In simple words: Bile, which helps digest fats, is made by the liver and kept in the gall bladder until needed.

🎯 Exam Tip: Understand that the liver produces bile, but the gallbladder stores and concentrates it, releasing it when fatty foods are consumed.

 

Question 4. The longest part of the alimentary canal is ileum.
Answer: The ileum is the final and longest section of the small intestine. Its main function is to absorb vitamin B12, bile salts, and any remaining nutrients that were not absorbed in the jejunum.
In simple words: The ileum is the longest last part of your small intestine, where final nutrients like vitamin B12 are absorbed.

🎯 Exam Tip: While the small intestine as a whole is long, specifically identify the ileum as its longest segment for precise answers.

 

Question 5. The human body functions normally at a temperature of about 37°C.
Answer: The average normal human body temperature is around 37°C (98.6°F). Maintaining this steady internal temperature, known as homeostasis, is crucial for enzymes to work correctly and for bodily processes to function efficiently.
In simple words: Our body works best at about 37 degrees Celsius. This normal temperature helps everything inside work properly.

🎯 Exam Tip: Note that 37°C is the average internal body temperature; slight variations are normal, but significant changes can indicate health issues.

 

Question 6. The largest cell in the human body of a female is ovum.
Answer: The ovum, or egg cell, is the largest cell in the human female body and is involved in reproduction. It contains genetic material and cellular components necessary for the development of an embryo if fertilized.
In simple words: The ovum, or egg, is the biggest cell in a female's body and is important for making babies.

🎯 Exam Tip: Remember that the ovum is not only the largest cell but also unique in its role in carrying genetic information for potential offspring.

III. State Whether True or False. If False, Correct the Statement:

 

Question 1. Nitric acid in the stomach kills microorganisms in the food.
Answer: False. The stomach produces hydrochloric acid (HCl), not nitric acid, which is highly acidic and effectively kills most microorganisms present in food. This acid also activates enzymes for protein digestion.
In simple words: False. It's hydrochloric acid in the stomach, not nitric acid, that kills germs in our food.

🎯 Exam Tip: Hydrochloric acid is vital for both sterilization of food and creating the acidic environment needed for pepsin to function in protein breakdown.

 

Question 2. During digestion, proteins are broken down into amino acids.
Answer: True. Proteins are complex molecules that are broken down into smaller units called amino acids during digestion. These amino acids are then absorbed by the body to build new proteins and tissues.
In simple words: True. When we digest proteins, they turn into tiny building blocks called amino acids that our body can use.

🎯 Exam Tip: Understand that amino acids are the simplest absorbable form of proteins, just as monosaccharides are for carbohydrates and fatty acids/glycerol for fats.

 

Question 3. Glomerular filtrate consists of many substances like amino acids, vitamins, hormones, salts, glucose and other essential substances.
Answer: False. While glomerular filtrate contains small molecules like amino acids, vitamins, salts, and glucose, most hormones are larger protein-based molecules that typically do not pass into the filtrate. The body regulates hormones carefully, and they are not typically filtered out as waste in this manner.
In simple words: False. Things like amino acids and glucose are filtered, but most hormones are too big and are not found in this filtered liquid.

🎯 Exam Tip: The glomerular filter is selectively permeable; small molecules pass through, but large molecules like proteins and most hormones are retained in the blood.

IV. Match the Following:

 

Question. Match the following organs with their primary elimination products.

Answer: 1 - (b) Sweat, 2 - (c) Carbon dioxide, 3 - (d) Undigested food, 4 - (a) Urine
In simple words: Skin releases sweat. Lungs breathe out carbon dioxide. The intestine gets rid of undigested food. Kidneys make urine to clean the blood.

🎯 Exam Tip: Focus on the primary excretory function of each organ, as some organs have multiple roles, but the matching typically refers to their main elimination product.

V. Differentiate the Following:

 

Question. Differentiate between:
(a) Excretion and Secretion
(b) Absorption and Assimilation
(c) Ingestion and Egestion
(d) Diphyodont and Heterodont
(e) Incisors and Canines
Answer:
(a) **Excretion:** Excretion is the biological process of removing metabolic waste products, such as urea and carbon dioxide, from the body. These wastes are harmful if they build up.
**Secretion:** Secretion involves cells, glands, or organs producing and discharging substances that have a specific function within the body or are excreted later. Examples include hormones or digestive enzymes.
(b) **Absorption:** Absorption is the process where digested nutrients move from the small intestine into the bloodstream or lymph. Tiny finger-like structures called villi help to absorb these nutrients.
**Assimilation:** Assimilation is when the absorbed nutrients are taken up by the body's cells and used for growth, repair, and energy. It's how the body makes the absorbed food a part of itself.
(c) **Ingestion:** Ingestion is the first step in nutrition, involving the intake of food into the digestive system, usually through the mouth. It's simply the act of eating.
**Egestion:** Egestion is the process of eliminating undigested or unabsorbed food waste from the body, typically as faecal matter, through the anus. It is the final step in the digestive process.
(d) **Diphyodont:** Diphyodont refers to animals, like humans, that develop two sets of teeth during their lifetime: a set of milk teeth (deciduous teeth) that are later replaced by a set of permanent teeth. This allows for jaw growth and stronger teeth.
**Heterodont:** Heterodont describes animals that possess more than one type of tooth, each with a specialized function. Humans, for instance, have incisors for cutting, canines for tearing, and premolars and molars for grinding.
(e) **Incisors:** Incisors are the flat, sharp teeth located at the front of the mouth. Their primary function is for cutting and biting food into smaller, manageable pieces, making the initial step of digestion easier.
**Canines:** Canines are the pointed, fang-like teeth found next to the incisors. They are adapted for tearing and piercing tough foods, such as meat, due to their conical shape.
In simple words: (a) Excretion is when the body gets rid of waste products, while secretion is when the body makes and releases useful things. (b) Absorption is when food nutrients enter the blood from the gut, and assimilation is when your body uses those nutrients to build and grow. (c) Ingestion is putting food in your mouth, and egestion is getting rid of food waste from your body. (d) Diphyodont means having two sets of teeth in life, and heterodont means having different kinds of teeth for different jobs. (e) Incisors are your front teeth for cutting food, and canines are the pointy teeth next to them, used for tearing food.

🎯 Exam Tip: When differentiating terms, define each clearly and highlight their key distinguishing features or processes. Using bullet points or separate paragraphs for each term can improve clarity.

VI. Answer Briefly:

 

Question 1. How is the small intestine designed to absorb digested food?
Answer: The small intestine is specially designed for absorbing digested food. It has tiny, finger-like folds called villi, which greatly increase its inner surface area. Each villus contains many small blood vessels and lymphatic vessels (lacteal tubes) to quickly absorb nutrients into the bloodstream. This structure helps maximize nutrient uptake.
In simple words: The small intestine has tiny folds called villi that make its surface very large. These villi have many blood vessels to quickly soak up food nutrients.

🎯 Exam Tip: Focus on the structural adaptations like villi, microvilli, and extensive blood supply, which are crucial for the efficient absorption of nutrients.

 

Question 2. Why do we sweat?
Answer: We sweat to cool our bodies down. When our body temperature rises, sweat glands release sweat, which is mostly water with some salts and other waste products. As this sweat evaporates from the skin, it takes heat away from the body, helping to maintain a stable internal temperature of about 37°C.
In simple words: We sweat when we get hot to cool our bodies. The sweat evaporates from our skin and carries heat away.

🎯 Exam Tip: Explain the process of evaporative cooling, emphasizing that it's the evaporation of sweat, not just its production, that cools the body.

 

Question 3. Mention any two vital functions of the human kidney.
Answer: The human kidneys perform several important functions. Two vital roles are:
1. They maintain the balance of fluids and electrolytes (like sodium and potassium) in the body, which is crucial for nerve and muscle function.
2. They help maintain the osmotic pressure in the blood and tissues, ensuring proper water distribution and preventing swelling. Kidneys also filter waste and produce hormones.
In simple words: Kidneys help keep the right amount of water and salts in our body. They also keep the blood's pressure balanced to make sure cells get enough water.

🎯 Exam Tip: Besides filtering waste, highlight the kidney's role in maintaining homeostasis, especially fluid and electrolyte balance, which is often overlooked.

 

Question 4. What is micturition?
Answer: Micturition is the process by which urine is expelled from the body. When the urinary bladder fills with urine, it sends signals to the brain, leading to the voluntary contraction of bladder muscles and relaxation of sphincters, allowing urine to be discharged through the urethra. A healthy person typically passes 1-2 liters of urine daily.
In simple words: Micturition is simply the act of passing urine from your body when your bladder is full.

🎯 Exam Tip: Emphasize that micturition is a reflex action but is also under voluntary control, particularly in adults.

 

Question 5. Name the types of teeth present in an adult human being. Mention the functions of each.
Answer: An adult human has four types of permanent teeth, which are incisors, canines, premolars, and molars. Each type has a specific role in breaking down food.

Incisors are for cutting and biting. Canines are pointed for tearing and piercing. Premolars and molars are for crushing, grinding, and chewing food. These different shapes help with efficient digestion.
In simple words: Adult humans have four kinds of teeth: incisors for cutting, canines for tearing, and premolars and molars for crushing and chewing. Each type helps break down food.

🎯 Exam Tip: Remember the specific number and function of each tooth type to demonstrate comprehensive knowledge of human dentition.

 

Question 6. Explain the structure of nephron.
Answer: A nephron, the kidney's filtering unit, comprises a renal corpuscle and a renal tubule. The renal corpuscle includes a cup-shaped Bowman's capsule that encases a network of capillaries called the glomerulus. Blood enters these capillaries through afferent arterioles and exits via efferent arterioles. The Bowman's capsule extends into the renal tubule, which has three main segments: the proximal convoluted tubule, the U-shaped Loop of Henle, and the distal convoluted tubule. The distal tubule then connects to a collecting tubule. These components create a complex system for blood filtration.
In simple words: A nephron is made of two main parts: a blood filter called the renal corpuscle (which has a Bowman's capsule and glomerulus) and a long tube called the renal tubule. This tube has three sections that all work together to clean the blood.

🎯 Exam Tip: When describing the nephron, clearly outline the two main parts (renal corpuscle and renal tubule) and their respective sub-components, explaining how their structure facilitates filtration and reabsorption.

VII. Answer in Detail:

 

Question 1. Describe the alimentary canal of man.
Answer: The human alimentary canal is a long, muscular, coiled tube where food digestion and absorption occur. It starts at the mouth, moves through the buccal cavity, pharynx, and oesophagus, leading to the stomach. From there, food passes into the small intestine (duodenum, jejunum, ileum) and then the large intestine (caecum, colon, rectum), finally exiting through the anus. Several glands, like the liver and pancreas, also contribute digestive juices.
* **Mouth:** The digestive process begins here with chewing and mixing food with saliva. It is framed by soft lips.
* **Teeth:** Hard structures in the mouth used for cutting, grinding, and crushing food. Humans have two sets of teeth (diphyodont) and different types of teeth (heterodont) – incisors, canines, premolars, and molars – each with a specialized function. For example, incisors cut, and molars grind.
* **Salivary glands:** There are three pairs of these glands (parotid, sublingual, submaxillary/submandibular) that produce saliva to moisten food and begin carbohydrate digestion.
* **Tongue:** A muscular, sensory organ that helps mix food with saliva and aids in swallowing.
* **Pharynx:** A membrane-lined cavity behind the nose and mouth, serving as a pathway for food to the oesophagus and air to the trachea.
* **Oesophagus:** A muscular tube, about 22 cm long, that transports food from the pharynx to the stomach through wave-like contractions called peristalsis.
* **Stomach:** A wide, J-shaped muscular organ located between the oesophagus and small intestine. It churns food and secretes gastric juices to begin protein digestion.
* **Small intestine:** The longest part of the alimentary canal (5-7m), divided into the duodenum, jejunum, and ileum. It is the main site for nutrient absorption.
* **Duodenum:** The C-shaped first part, receiving bile from the liver and pancreatic juice from the pancreas for digestion.
* **Jejunum:** The middle part of the small intestine, primarily responsible for nutrient absorption.
* **Ileum:** The lower and longest part of the small intestine, connecting to the large intestine. It absorbs vitamin B12 and bile salts.
* **Liver:** The body's largest digestive gland, reddish-brown in color. It produces bile, which helps in the emulsification of fats (breaking large fat droplets into small ones).
* **Pancreas:** A leaf-shaped gland between the stomach and duodenum, acting as both an exocrine gland (producing digestive enzymes) and an endocrine gland (producing hormones like insulin).
* **Large intestine:** Approximately 1.5 meters long, it receives unabsorbed food from the ileum and extends to the anus. It consists of the caecum, colon, and rectum.
* **Caecum:** A small, blind pouch at the junction of the small and large intestines. The vermiform appendix, a vestigial organ, arises from its blind end.
* **Colon:** Broader than the ileum, it absorbs water and electrolytes from indigestible food matter. It has ascending, transverse, and descending parts.
* **Rectum:** The final section of the large intestine, temporarily storing faecal matter before its expulsion from the body through the anus.
In simple words: The alimentary canal is the whole path food takes through your body. It starts at your mouth, then goes down your throat to your stomach, small intestine, and large intestine, and finally out. Along the way, different parts and glands help break down the food and take out the good bits.

🎯 Exam Tip: When describing the alimentary canal, ensure you list all major organs in sequence and briefly explain the primary function of each, including accessory glands like the liver and pancreas.

 

Question 2. Explain the structure of the kidney and the steps involved in the formation of urine.
Answer:
STRUCTURE OF KIDNEYS:

• Kidneys are bean-shaped and reddish-brown in color.
• They are located on both sides of the backbone in the abdominal area, attached to the back body wall.
• The right kidney is positioned slightly lower than the left because the liver occupies space on the right side.
• Each kidney is about 11 cm long, 5 cm wide, and 3 cm thick.
• Inside, the kidney has two main regions: an outer dark part called the cortex and an inner lighter part called the medulla. These two areas contain many tiny filtering units called nephrons or uriniferous tubules.
• The medulla consists of many cone-shaped masses.
• On the inner curved side of each kidney, there is a dent called the hilum. Blood vessels and nerves enter through this opening, and urine leaves through it.

STEPS INVOLVED IN URINE FORMATION:
There are three main stages in urine formation:

1. Glomerular filtration: Urine production starts when blood is filtered through the thin walls of the glomerulus and Bowman's capsule. The liquid that is filtered out is called glomerular filtrate. Both useful and waste substances from the blood are filtered at this stage.
2. Tubular reabsorption: The filtrate in the first part of the kidney tubule (proximal tubule) contains important substances like glucose, amino acids, vitamins, sodium-potassium bicarbonates, and water. These useful substances are absorbed back into the blood through a process called selective reabsorption. This reabsorption ensures the body keeps what it needs.
3. Tubular secretion: Waste substances like urea or ions are actively moved from the blood into the kidney tubule. The fluid that remains after all these processes is finally known as urine, which is more concentrated in humans. The urine then moves into collecting ducts, through the pelvis, and into the ureters, which carry it to the urinary bladder.

When the urinary bladder becomes full, the urine is pushed out through the urethra. This process is called micturition. A healthy person usually passes about 1 to 2 liters of urine each day.
In simple words: Kidneys filter blood to make urine. This happens in three steps: first, blood is filtered; second, useful things are reabsorbed; and third, extra wastes are secreted into the urine. This keeps the body clean.

🎯 Exam Tip: When describing the kidney, remember to mention both its external features (shape, size, position) and internal structure (cortex, medulla, nephrons) to score full marks.

 

VIII. Assertion and Reason :

 

Question 1. Assertion: Urea is excreted out through the kidneys.
Reason: Urea is a toxic substance.
Answer: (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion
In simple words: The kidneys remove urea from the body because urea is harmful. The reason tells us why the assertion is true.

🎯 Exam Tip: For assertion-reason questions, first check if both statements are individually true, then see if the reason directly explains the assertion. Using "because" between the two statements can help test the link.

 

Question 2. Assertion: In both the sexes gonads perform dual function.
Reason: Gonads are also called primary sex organs.
Answer: (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion
In simple words: Gonads in both males and females do two jobs. They are called primary sex organs, and this is why they have a dual role.

🎯 Exam Tip: Gonads are important for both making sex cells and producing hormones, which defines their dual function. Understanding these roles helps clarify why they are primary sex organs.

 

IX. Higher Order Thinking Skills :

 

Question 1. If pepsin is lacking in gastric juice, then which event in the stomach will be affected?
(a) digestion of starch into sugars.
(b) breaking of proteins into peptides.
(c) digestion of nucleic acids.
(d) breaking of fats into glycerol and fatty acids.
Answer: (b) breaking of proteins into peptides.
In simple words: Pepsin is a special helper in the stomach that breaks down proteins. If it's not there, proteins cannot be broken into smaller pieces called peptides.

🎯 Exam Tip: Remember that different enzymes break down different types of food; pepsin is specifically for proteins in the stomach, while amylase handles starch and lipase handles fats.

 

Question 2. Name the blood vessel that
(a) enter malphigian capsule and
(b) leaves malphigian capsule.
Answer:
(a) Afferent arteriole.
(b) Efferent arteriole.
In simple words: Blood goes into the Malpighian capsule through the afferent arteriole and leaves through the efferent arteriole. These are like the "in" and "out" pipes for blood in the kidney's filtering unit.

🎯 Exam Tip: It's important to remember that the afferent arteriole is wider than the efferent arteriole, which helps create the pressure needed for filtration in the glomerulus.

 

Question 3. Why do you think that urine analysis is an important part of medical diagnosis?
Answer: Urine is waste liquid from the human body, made mostly of water (more than 95%) and other things like urea, salts, and various chemical compounds. If a person is sick or has a disease, the types and amounts of these substances in their urine can change. Looking at these changes helps doctors find and understand health problems such as kidney infections, liver issues, or diabetes. It's like a window into the body's internal health.
In simple words: Urine analysis is important because changes in urine content can show if someone has a disease like kidney problems or diabetes. It's an easy way for doctors to check on health.

🎯 Exam Tip: When explaining diagnostic tools, focus on what information they provide and how that information is used to identify medical conditions.

 

Question 4. Why does your doctor advise you to drink plenty of water?
Answer: Drinking enough water helps our body in several ways:

• It helps keep the right balance of fluids and salts in the body.
• When muscles don't get enough water, they can get tired easily.
• Our kidneys need a lot of water to work properly and clean the blood. Water helps flush out waste products effectively.
• Staying hydrated is generally important for good health and proper body functions.

In simple words: Doctors tell us to drink lots of water because it keeps our body fluids balanced, stops muscles from getting tired, helps kidneys work well, and keeps us healthy overall.

🎯 Exam Tip: Focus on key bodily functions directly affected by water intake—fluid balance, kidney function, and muscle performance—as these are crucial points.

 

Question 5. Can you guess why there are sweat glands on the palm of our hands and the soles of our feet?
Answer: Sweat glands are found on the palms of our hands and the soles of our feet primarily for controlling body temperature. Sweating on these areas, which are often exposed and interact with surfaces, helps to cool the body down. Also, sweat can act as a natural defense against tiny germs that our hands and feet often come into contact with, protecting these frequently used body parts.
In simple words: We have sweat glands on our palms and soles to help cool us down and to fight off germs, as these parts touch many things and get warm easily.

🎯 Exam Tip: The two main functions of sweat mentioned—thermoregulation and a minor role in defense against microbes—are the key points to include in your answer.

 

X. Match the parts of the given figure with the correct option:

Answer: (d) Fallopian tube Ovary Cervix Uterus Vagina
In simple words: Look at the diagram and match each numbered part with its correct name from the options given. This shows the parts of the female reproductive system.

🎯 Exam Tip: When matching diagram labels, always carefully trace the lines to the specific anatomical parts. Review the basic anatomy of major organ systems to avoid confusion.

 

ACTIVITY - 1
Answer:
1. Are the teeth of animals similar to ours?
2. How is the shape of their teeth related to their food habit?
No, there are many differences between human teeth and animal teeth:

• Humans usually have up to 32 teeth, but many animals have more than we do.
• Humans use their teeth mainly for breaking down food. Animals, however, need their teeth for breaking down food, and also for protecting themselves by hunting, attacking, or defending.

Lion Teeth: Carnivores like lions have very sharp, scissor-like teeth. Their front teeth are used to bite and hold prey, while their long canine teeth are for tearing flesh. Their back teeth (molars) are also sharp for slicing, rather than chewing, because they tend to swallow large pieces of food.Bison or Buffalo Teeth: Herbivores like bison or buffalo eat plants. They have more molars than humans. They use these flat teeth to grind branches, grasses, and seeds. Their front teeth are often shaped like pruning shears to cut leaves and stems.
In simple words: Animal teeth are different from human teeth because animals eat different foods and need teeth for hunting or defense. Lions have sharp teeth for meat, while bison have flat teeth for grinding plants.

🎯 Exam Tip: When comparing structures like teeth, always relate their form to their function and the organism's lifestyle (e.g., diet, defense) for a comprehensive answer.

 

I. Choose the correct answers :

 

Question 1. In the dental formula \( \frac{2,1,2}{2,1,2} \) 3 refers to
(a) incisors
(b) molars
(c) premolars
(d) canine
Answer: (c) premolars
In simple words: In the dental formula, the first number is incisors, the second is canines, the third is premolars, and the fourth is molars. So, '3' represents premolars.

🎯 Exam Tip: Remember the order of teeth in the dental formula: Incisors, Canines, Premolars, Molars (I, C, P, M). This sequence helps correctly identify each tooth type.

 

Question 2. Lysozyme is seen in
(a) gastric juice
(b) intestinal juice
(c) bile
(d) saliva
Answer: (d) saliva
In simple words: Lysozyme is a special substance found in saliva. It helps kill some germs in our mouth.

🎯 Exam Tip: Lysozyme is a key antibacterial enzyme found in body secretions like tears and saliva, providing a first line of defense against pathogens.

 

Question 3. ................ is the smallest gland.
(a) Pancreas
(b) Sublingual
(c) Parotid
(d) Submaxillary
Answer: (b) Sublingual
In simple words: The sublingual gland is the smallest among the main salivary glands in the mouth. It sits right under the tongue.

🎯 Exam Tip: Knowing the relative sizes and locations of the major salivary glands (parotid, submandibular, sublingual) is important for anatomy questions.

 

Question 4. Curdling of milk protein is done by ................
(a) pepsin
(b) rennin
(c) lipase
(d) maltase
Answer: (b) rennin
In simple words: Rennin is an enzyme, mainly found in babies, that helps curdle milk in the stomach. This makes it easier to digest milk proteins.

🎯 Exam Tip: Rennin (not to be confused with renin, a kidney hormone) is specifically responsible for coagulating milk proteins, especially in infants. Pepsin digests other proteins.

 

Question 5. ................ acts as birth canal.
(a) Fallopian tube
(b) Vagina
(c) Uterus
(d) Vasdeferens
Answer: (b) Vagina
In simple words: The vagina is the tube in the female body that acts as the birth canal. It is the passage through which a baby comes out during birth.

🎯 Exam Tip: Understand the primary functions of each part of the female reproductive system to correctly identify terms like "birth canal."

 

Question 6. The act of bringing swallowed food back to the mouth
(a) egestion
(b) ingestion
(c) micturition
(d) regurgitation
Answer: (d) regurgitation
In simple words: Regurgitation means food that has already been swallowed comes back up into the mouth. It's different from vomiting, where stomach contents are forcefully expelled.

🎯 Exam Tip: Differentiate between key digestive terms: ingestion (taking in food), digestion (breaking down food), absorption (taking nutrients into blood), egestion (removing undigested waste), and regurgitation (food coming back up).

 

Question 7. Gastric glands do not secrete
(a) renin
(b) pepsin
(c) lipase
(d) none of the options
Answer: (c) lipase
In simple words: Gastric glands in the stomach produce pepsin for protein digestion and small amounts of renin in infants. They do not produce significant amounts of lipase, which mainly digests fats in the small intestine.

🎯 Exam Tip: Focus on the primary enzymes and substances secreted by gastric glands: hydrochloric acid, pepsinogen (converts to pepsin), and mucus. While some gastric lipase exists, it's not a major secretion compared to pepsin.

 

Question 8. Excretion means
(c) distribution of digested food to the body tissues through blood.
(d) removal of nitrogenous wastes generated in the body.
Answer: (d) removal of nitrogenous wastes generated in the body
In simple words: Excretion is the process where our body gets rid of waste products that contain nitrogen, such as urea. It's how the body cleans itself of harmful by-products.

🎯 Exam Tip: Clearly distinguish excretion (removal of metabolic wastes) from egestion (removal of undigested food) and secretion (release of useful substances).

 

Question 9. Which is the major excretory product in human?
(a) \( H^+ \) or \( K^+ \)
(b) Glucose
(c) Urea
(d) Creatinine
Answer: (c) Urea
In simple words: The main waste product that humans excrete is urea. It is formed from the breakdown of proteins and is removed by the kidneys.

🎯 Exam Tip: Urea is the primary nitrogenous waste in mammals, highlighting its importance in excretory system functions. Other substances like creatinine are also excreted, but urea is the most significant in terms of quantity.

 

Question 10. Which is a pear-shaped muscular organ in females?
(a) Uterus
(b) Fallopian tubes
(c) Ovaries
(d) Vagina
Answer: (a) Uterus
In simple words: The uterus, also known as the womb, is a muscular organ shaped like a pear where a baby grows inside a female's body.

🎯 Exam Tip: Visualizing the organs' shapes helps remember their names and functions. The uterus is distinctly pear-shaped and crucial for fetal development.

 

Question 11. What is the other name of fallopian tubes?
(a) Ovaries
(b) Fimbriae
(c) Oviducts
(d) Ova
Answer: (c) Oviducts
In simple words: Fallopian tubes are also called oviducts. They are tubes that carry eggs from the ovaries to the uterus.

🎯 Exam Tip: Knowing synonyms for anatomical structures (e.g., Fallopian tubes = Oviducts) is often tested. Fimbriae are finger-like projections at the end of the Fallopian tubes, not the tubes themselves.

 

II. Fill in the blanks :

 

Question 1. ................ is the smallest cell in males.
Answer: Sperm
In simple words: The sperm cell is the smallest cell found in the male human body. It is designed to carry genetic information.

🎯 Exam Tip: Recall that the sperm cell is characterized by its small size and its tail (flagellum), which helps it move.

 

Question 2. Progesterone is secreted by..................
Answer: corpus luteum
In simple words: Progesterone is a hormone made by the corpus luteum, which forms in the ovary after an egg is released. This hormone helps prepare the uterus for pregnancy.

🎯 Exam Tip: Understand the sequence of events in the menstrual cycle, where the corpus luteum forms from the follicle after ovulation and produces progesterone.

 

Question 3. The oviducts are also known as ................
Answer: fallopian tubes
In simple words: Oviducts are another name for fallopian tubes. They are important for carrying eggs from the ovary to the uterus.

🎯 Exam Tip: Remember that "oviduct" and "Fallopian tube" refer to the same structure, highlighting their role in egg transport.

 

Question 4. One mature ovum is released once in every.................. days.
Answer: 28
In simple words: A mature egg is released from the ovary approximately every 28 days in a typical menstrual cycle. This regular release is part of the female reproductive cycle.

🎯 Exam Tip: The 28-day cycle is an average; menstrual cycles can vary, but this is the standard duration often used in textbooks.

 

Question 5. Beta cells of pancreas produce ................
Answer: insulin
In simple words: The beta cells found in the pancreas make insulin. Insulin is a hormone that helps control blood sugar levels in our body.

🎯 Exam Tip: It is crucial to associate beta cells with insulin production and alpha cells with glucagon production, as these hormones are vital for blood glucose regulation.

 

Question 6. Organs which are concerned with the formation, storage and elimination of urine constitute the ................
Answer: excretory system
In simple words: The excretory system is made up of all the organs that work together to create, store, and remove urine from the body. This system ensures waste is properly disposed of.

🎯 Exam Tip: Understand that the excretory system includes kidneys, ureters, urinary bladder, and urethra, each playing a specific role in managing urine.

 

Question 7. In the process of urine formation, the maximum amount of water from the glomerular filtrate is reabsorbed in the ................
Answer: proximal convoluted tubule
In simple words: Most of the water that is filtered out of the blood is taken back into the body in the first coiled part of the kidney tubule, called the proximal convoluted tubule. This stops too much water from being lost.

🎯 Exam Tip: The proximal convoluted tubule is where the majority of reabsorption (water, glucose, amino acids, salts) takes place, making it a critical segment of the nephron.

 

Question 8. ................ receives the sperms, acts as birth canal during childbirth.
Answer: Vagina
In simple words: The vagina is the female reproductive organ that receives sperm. It also stretches to become the birth canal when a baby is born.

🎯 Exam Tip: The vagina has multiple key roles, including being a part of sexual intercourse, the birth canal, and the exit for menstrual flow.

 

Question 9. The narrower lower part of the uterus is ................
Answer: cervix
In simple words: The cervix is the narrow, lower part of the uterus that connects to the vagina. It acts as a gateway between the uterus and the outside.

🎯 Exam Tip: The cervix is important for protecting the uterus from infection and for dilating during childbirth.

 

Question 10. ................ carries sperms to the seminal vesicles.
Answer: Vas deferens
In simple words: The vas deferens is a tube that transports sperm from the epididymis to the seminal vesicles before ejaculation. It's a key path for sperm travel.

🎯 Exam Tip: The vas deferens is a muscular tube that propels sperm through peristaltic contractions during ejaculation, connecting to the ejaculatory duct.

 

Question 11. ................ is the smallest cell in the male body.
Answer: Sperm
In simple words: The smallest cell in a male's body is the sperm cell. Its small size and mobility are designed for fertilization.

🎯 Exam Tip: This question reinforces the previous one about sperm's size, emphasizing its unique cellular characteristics.

 

Question 12. The process of formation of sperms is known as ................
Answer: spermatogenesis
In simple words: Spermatogenesis is the biological process where sperm cells are made in the testes of males. This process ensures the continuous production of male reproductive cells.

🎯 Exam Tip: Understand the 'genesis' suffix means 'origin' or 'formation,' helping to link terms like spermatogenesis (sperm formation) and oogenesis (egg formation).

 

Question 13. ................ is the vestigeal organ in human.
Answer: Vermiform appendix
In simple words: The vermiform appendix is a small, finger-shaped organ connected to the large intestine. It is called a vestigeal organ because it has lost its original function in humans.

🎯 Exam Tip: Vestigeal organs are remnants of structures that had a function in ancestral species but are no longer functional in the current species.

 

Question 14. ................ acts as a thermoregulatory organ.
Answer: Scrotum
In simple words: The scrotum is an organ that helps control temperature. It keeps the testes at a cooler temperature than the rest of the body, which is important for healthy sperm production.

🎯 Exam Tip: Emphasize the scrotum's role in maintaining optimal temperature for spermatogenesis, which is typically 1-3°C below core body temperature.

 

Question 15. Tubular filtrate finally known as..................
Answer: urine
In simple words: After the blood has been filtered and useful substances reabsorbed, the remaining liquid in the kidney tubules is finally called urine. This is the waste fluid that leaves the body.

🎯 Exam Tip: The term "filtrate" refers to the liquid initially filtered from the blood, while "urine" is the final product after reabsorption and secretion in the tubules.

 

III. Match the following:

Answer:
Ovaries - Bean shape
Fallopian tubes - Almond shape
Uterus - Funnel - shape
Kidney - Peas -shape
In simple words: This matching exercise connects each organ with its typical shape. For example, ovaries are shaped like beans, and the uterus has a funnel shape.

🎯 Exam Tip: When matching, remember distinct visual characteristics like the kidney's bean shape, which is a common mnemonic.

 

IV. Answer the following in one or two sentences :

 

Question 1. It conducts food from pharynx to stomach by peristalsis.
Answer: Oesophagus.
In simple words: The oesophagus is the tube that carries food from the throat down to the stomach using wave-like muscle movements.

🎯 Exam Tip: Peristalsis is the key action here, describing the involuntary muscle contractions that move food along the digestive tract.

 

Question 2. Finger-like projections enhance the absorbing capacity of the small intestine.
Answer: Villi.
In simple words: Villi are tiny finger-like structures in the small intestine that increase the surface area. This helps the body absorb more nutrients from digested food.

🎯 Exam Tip: Villi are crucial for efficient nutrient absorption; their large surface area is a vital adaptation of the small intestine.

 

Question 3. The bunch of capillaries inside the Bowman's capsule.
Answer: Glomerulus.
In simple words: The glomerulus is a cluster of tiny blood vessels inside Bowman's capsule. This is where blood filtration begins in the kidney.

🎯 Exam Tip: The glomerulus and Bowman's capsule together form the renal corpuscle, which is the primary site of blood filtration.

 

Question 4. Thin muscular tubes which carry urine from kidney to urinary bladder.
Answer: Ureter.
In simple words: Ureters are thin tubes made of muscle that transport urine from each kidney down to the bladder for storage.

🎯 Exam Tip: Ureters use peristaltic contractions to push urine, preventing backflow and ensuring a steady movement to the bladder.

 

Question 5. Small sac-like muscular structures that enclose testes.
Answer: Scrotal sacs.
In simple words: Scrotal sacs are small, muscular pouches that hold the testes. They help keep the testes at the right temperature for sperm production.

🎯 Exam Tip: Emphasize the scrotal sacs' role in temperature regulation, which is vital for the viability of sperm.

 

V. Very short answer questions :

 

Question 6. What is heparin?
Answer: Heparin is a special substance that prevents blood from clotting. It is naturally made by the liver in our body. This keeps the blood flowing smoothly.
In simple words: Heparin is a natural blood thinner made by the liver, which stops blood from forming clots.

🎯 Exam Tip: Remember heparin is an *anticoagulant* — a key term to use when explaining its function.

 

Question 7. What are Islets of Langerhans?
Answer: The Islets of Langerhans are groups of cells found in the pancreas. These special cells act like endocrine glands, which means they produce and release hormones directly into the bloodstream. They are very important for controlling blood sugar levels. They produce hormones like insulin and glucagon.
In simple words: Islets of Langerhans are cell clusters in the pancreas that make hormones like insulin and glucagon to control blood sugar.

🎯 Exam Tip: When defining a biological structure, always mention its location and primary function, especially for glands and hormone production.

 

Question 8. What is succus entericus?
Answer: Succus entericus is the name for the intestinal juice secreted by the intestinal glands. This juice contains many important enzymes such as maltase, lactase, sucrase, and lipase, which help in the final stages of digestion. These enzymes ensure that food is fully broken down for absorption.
In simple words: Succus entericus is the juice made by the small intestine, full of enzymes that finish breaking down food.

🎯 Exam Tip: When asked about digestive juices, always mention the specific enzymes they contain and what those enzymes digest.

 

Question 9. What is a vermiform appendix?
Answer: The vermiform appendix is a small, finger-like tube that comes out from the blind end of the caecum. The caecum is the beginning part of the large intestine. In humans, it is considered a vestigial organ, meaning it no longer has a significant function. However, some theories suggest it might play a minor role in the immune system.
In simple words: The vermiform appendix is a small, useless, finger-shaped organ attached to the large intestine.

🎯 Exam Tip: Highlight "vestigial organ" and "functionless" when describing the vermiform appendix, as these are key terms.

 

Question 10. What is the contribution of Joseph E. Murray in Nephrology?
Answer: Joseph E. Murray was a pioneer in nephrology. He performed the first successful human kidney transplant operation. This groundbreaking achievement revolutionized the treatment for kidney failure, offering a new hope for patients with end-stage renal disease.
In simple words: Joseph E. Murray did the first successful kidney transplant, which was a huge step for treating kidney disease.

🎯 Exam Tip: For historical contributions, state the person's name, their field, and their specific, significant achievement concisely.

 

Question 11. What is parturition?
Answer: Parturition is the scientific term for childbirth. It refers to the process where a baby is born by being expelled from the mother's uterus through the birth canal. This complex process involves a series of hormonal and muscular changes.
In simple words: Parturition is simply the medical word for giving birth to a baby.

🎯 Exam Tip: Define biological processes clearly and concisely, using scientific terms and a simple explanation.

 

VI. Short answer questions :

 

Question 1. What is an artificial kidney?
Answer: An artificial kidney, also known as a dialysis machine, is a device used to filter a patient's blood when their own kidneys stop working effectively.
(i) When natural kidneys fail, harmful fluids and waste products build up in the body, leading to a condition called kidney (renal) failure.
(ii) To treat this, the artificial kidney removes these toxic wastes from the blood in a process called hemodialysis. If kidney failure cannot be managed with medication or dialysis, a kidney transplant may be recommended. This technology has saved many lives.
In simple words: An artificial kidney is a machine that cleans a patient's blood when their own kidneys fail, removing harmful waste products.

🎯 Exam Tip: When explaining artificial kidneys, mention kidney failure, hemodialysis, and the reason for its use (removing toxic wastes and excess fluid).

 

Question 2. Draw the human excretory system and label the parts.
Answer:
In simple words: The drawing shows the main organs of the body that remove waste: the kidneys, tubes called ureters, the bladder that stores urine, and the urethra that lets urine out.

🎯 Exam Tip: When drawing diagrams, ensure all key parts are clearly visible and correctly labeled. Use appropriate colors for blood vessels if possible (red for arteries, blue for veins).

 

Question 3. What are the end products of digestion of starch, proteins and fats respectively?
Answer: After digestion is complete, starch, proteins, and fats are broken down into simpler forms that the body can absorb.
- Starch is broken down into Glucose.
- Proteins are broken down into Amino acids.
- Fats are broken down into Fatty acids and glycerol.
These simple forms can then be easily absorbed into the bloodstream.
In simple words: Starch becomes glucose, proteins become amino acids, and fats become fatty acids and glycerol after digestion.

🎯 Exam Tip: Remember the simplest units for each macromolecule: Carbohydrates (starch) into Monosaccharides (glucose), Proteins into Amino acids, and Lipids (fats) into Fatty acids and glycerol.

 

Question 4. What are the functions of the ovaries and uterus in the female reproductive system?
Answer: The ovaries and uterus are crucial parts of the female reproductive system.
**Functions of ovaries :**
- The ovaries act as the female gonads, which means they produce ova (eggs), which are the female gametes.
- They also make important female sex hormones, such as estrogen and progesterone. These hormones are essential for the menstrual cycle and pregnancy.
**Functions of uterus :**
- The uterus is a muscular, hollow organ shaped like a pear, located in the pelvic area.
- It is where a fetus develops during pregnancy. The uterus provides a nurturing environment for the growing baby.
In simple words: Ovaries make eggs and female hormones, while the uterus is a strong, pear-shaped organ where a baby grows.

🎯 Exam Tip: Clearly distinguish between the primary functions of ovaries (gamete and hormone production) and the uterus (fetal development and housing).

 

Question 5. Give reasons for the following
(a) Scrotum remains outside the body of human males.
(b) The wall of the stomach is not digested by its own enzyme.
Answer:
(a) The scrotum, which holds the two testes, is located outside the male body. This placement is important because it keeps the testes at a temperature about 1-3°C lower than the normal body temperature. This cooler temperature is essential for the proper development and formation of sperm, making the scrotum a thermoregulatory organ.
(b) The stomach wall is protected from being digested by its own strong enzymes, like pepsin, due to several protective mechanisms. First, the stomach lining produces a thick layer of mucus, which acts as a barrier. Second, the gastric enzyme pepsinogen is secreted in an inactive form (proenzyme) and only becomes active pepsin when food enters the stomach, preventing self-digestion when the stomach is empty.
In simple words: (a) The scrotum is outside the body to keep testes cool for healthy sperm production. (b) The stomach protects itself with a mucus layer and by keeping digestive enzymes inactive until food arrives.

🎯 Exam Tip: For "give reasons" questions, clearly state the biological reason and any related structures or processes, such as thermoregulation for the scrotum or mucus for the stomach.

 

Question 6. What is homeostasis?
Answer: Homeostasis is the body's natural ability to keep its internal environment stable and balanced, even when conditions outside the body change. It involves various processes that maintain a constant internal state, like body temperature, blood sugar, and water levels. This balance is vital for the body to function correctly.
In simple words: Homeostasis is how the body keeps itself balanced inside, no matter what changes happen outside.

🎯 Exam Tip: Emphasize "stable internal environment" and "balance" as key terms when defining homeostasis.

 

Question 7. Rearrange the jumbled sequence of the different parts of alimentary canal in proper sequence, (oesophagus, small intestine, stomach, large intestine, anus, mouth, rectum)
Answer: The proper sequence of the alimentary canal parts, from where food enters to where waste leaves, is:
Mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus.
Each part plays a specific role in breaking down food and absorbing nutrients.
In simple words: The correct order of food moving through the body is mouth, oesophagus, stomach, small intestine, large intestine, rectum, then anus.

🎯 Exam Tip: Practice visualizing the digestive path to accurately sequence the alimentary canal parts, starting from intake to elimination.

 

Question 8. Select the substances given below that need to be excreted from the body, (urea, amino acids, carbon dioxide, uric acid, glucose)
Answer: The substances from the list that need to be excreted from the body are:
Urea and carbon dioxide.
Urea is a waste product from protein breakdown, and carbon dioxide is a waste product from cellular respiration. Both are harmful if they build up in the body.
In simple words: Urea and carbon dioxide are the waste products from the list that the body must get rid of.

🎯 Exam Tip: Differentiate between waste products that must be excreted (like urea, uric acid, carbon dioxide) and useful substances that are absorbed or retained (like amino acids, glucose).

 

Question 9. Rearrange the jumbled words and fill in the blanks in the following passage to make it a meaningful description.
The human urinary system consists of a pair of ........ (nyedik), which form the urine; a pair of ........ (ertreu), which conduct the ..... (neuri) from kidneys to the ........ (naryuri drebdal) for storage of urine and a ........ (reuhrat) through which the urine is voided by bladder contractions.
Answer: The human urinary system consists of a pair of **Kidneys** (nyedik), which form the urine; a pair of **Ureters** (ertreu), which conduct the **urine** (neuri) from kidneys to the **Urinary bladder** (naryuri drebdal) for storage of urine and a **Urethra** (reuhrat) through which the urine is voided by bladder contractions.
1. Kidney
2. Ureter
3. Urine
4. Urinary bladder
5. Urethra
In simple words: The urinary system includes kidneys to make urine, ureters to carry it, the urinary bladder to store it, and the urethra to release it.

🎯 Exam Tip: Carefully read the context of each blank to match the jumbled word with the correct anatomical term, considering its function in the sentence.

 

VII. Long answer questions :

 

Question 1. List the function of the liver.
Answer: The liver performs many vital functions in the body, acting like a central processing unit for metabolism and detoxification.
- It helps make red blood cells in a fetus before birth.
- It creates fibrinogen and prothrombin, which are proteins necessary for blood clotting.
- The liver breaks down and removes old red blood cells.
- It stores important substances like iron, copper, and vitamins A and D.
- It produces heparin, a substance that stops blood from clotting.
- The liver gets rid of toxic and metallic poisons from the body.
- It also detoxifies various substances, including drugs and alcohol, making them less harmful.
In simple words: The liver makes blood clotting proteins, stores vitamins, destroys old red blood cells, filters poisons, and produces heparin.

🎯 Exam Tip: When listing functions, group similar activities (e.g., blood-related, storage, detoxification) to make the answer comprehensive and easy to remember.

 

Question 2. Draw a chart to show the various enzymes produced during digestion in our body and their action.
Answer:

In simple words: Different glands in our body make specific enzymes that break down food. For example, salivary glands make ptyalin for starch, gastric glands make pepsin for proteins, and the pancreas and intestinal glands make many enzymes for fats, proteins, and sugars.

🎯 Exam Tip: When creating charts for enzymes, ensure you clearly link each enzyme to its producing gland, the specific nutrient it acts upon (substrate), and the final products formed.

 

Question 3. Write a note on teeth of humans.
Answer: Human teeth are hard structures essential for holding, cutting, grinding, and crushing food, which is the first step in digestion.
- Humans have two sets of teeth during their lifetime, making them **Diphyodont**. The first set consists of 20 temporary or milk teeth, which are later replaced by 32 permanent teeth, with 16 in each jaw.
- Each tooth has a root that fits into the gum, a condition called **Thecodont**.
- Permanent teeth are of four different types, making humans **Heterodont**. These types-incisors, canines, premolars, and molars-each have a specific structure and function.
- The dental formula shows the number of each type of tooth in half of the upper and lower jaw.
For milk teeth (deciduous teeth), the formula for each half of the jaw is: \( \frac{2,1,2}{2,1,2} \) which means 2 incisors, 1 canine, 2 premolars in upper and lower jaw. So, \( (2+1+2) \times 2 = 10 \) teeth per jaw, total \( 10 \times 2 = 20 \) milk teeth.
For permanent teeth, the formula for each half of the jaw is: \( \frac{2,1,2,3}{2,1,2,3} \), meaning 2 incisors, 1 canine, 2 premolars, and 3 molars in upper and lower jaw. So, \( (2+1+2+3) \times 2 = 16 \) teeth per jaw, total \( 16 \times 2 = 32 \) permanent teeth.
**Types of teeth and their functions :**

In simple words: Humans have two sets of teeth in their lives (Diphyodont), with roots in their gums (Thecodont), and four different types of teeth for eating (Heterodont) – incisors, canines, premolars, and molars – each with a special job.

🎯 Exam Tip: Remember the terms Diphyodont, Thecodont, and Heterodont as they are key to describing human dentition, along with the specific functions of each tooth type.

 

Question 4. Write a note on functions of liver in digestion.
Answer: The liver is the body's largest digestive gland and is reddish-brown in color, divided into two main lobes. It plays several critical roles in digestion.
- The liver has a gallbladder on its underside, which stores bile. Liver cells produce bile.
- Bile is released into the small intestine when food enters it. Bile contains bile salts (like sodium glycolate and sodium tauroglycolate) and bile pigments (bilirubin and biliverdin).
- Bile salts are essential for the digestion of fats through a process called emulsification, which breaks large fat droplets into smaller ones. This makes it easier for enzymes to digest fats. This process is crucial for absorbing fats and fat-soluble vitamins.
In simple words: The liver makes bile, which is stored in the gallbladder and helps break down fats in the small intestine so they can be digested.

🎯 Exam Tip: Focus on the liver's role in bile production and fat emulsification when asked about its digestive functions.

 

Question 5. Write a note on the skin.
Answer: The skin is the outermost layer covering the entire human body, forming a protective barrier. It is the body's largest organ, accounting for about 15% of an adult's body weight.
- The skin protects the body from external harm and contains many structures and glands.
- It helps eliminate metabolic wastes through perspiration (sweating), acting as an excretory organ.
- The human body normally functions at about 37°C. When the body gets hot, sweat glands in the skin produce sweat, which contains water and small amounts of chemicals like ammonia, urea, lactic acid, and salts (mainly sodium chloride).
- As sweat evaporates from the skin's surface, it helps to cool the body down and maintain a stable internal temperature. This is a vital part of thermoregulation.
In simple words: Skin is the body's largest outer covering, it protects us, helps remove waste through sweat, and cools the body when it evaporates.

🎯 Exam Tip: Remember the key functions of skin: protection, excretion (through sweat), and thermoregulation.

 

VIII. Higher Order Thinking Skills :

 

Question 1. Reproductive organs are also considered endocrine glands.
Answer: Reproductive organs, such as the testes in males and ovaries in females, are considered endocrine glands because they perform a dual function. Besides producing reproductive cells (sperms and ova, respectively), they also produce and secrete hormones directly into the bloodstream. For example, the testes produce male sex hormones like testosterone, while the ovaries produce female sex hormones such as estrogen. These hormones are vital for the development of secondary sexual characteristics and for regulating the reproductive cycle.
In simple words: Reproductive organs are endocrine glands because they not only make sperm or eggs but also produce and release hormones like testosterone and estrogen.

🎯 Exam Tip: When discussing dual functions of organs, clearly state both roles (e.g., gamete production and hormone secretion for reproductive organs) and give examples of the substances produced.

 

Question 2. Skin is considered to be an excretory organ - Justify.
Answer: Skin is considered an excretory organ because it removes waste products from the body through sweat. When we sweat, the skin eliminates water, salts (like sodium chloride), and small amounts of metabolic wastes such as urea and lactic acid. While primarily known for cooling the body, this process also contributes to the removal of substances that the body does not need or that are in excess. This is a subtle but important excretory role.
In simple words: Skin is an excretory organ because it removes water, salts, and some waste like urea from the body through sweat.

🎯 Exam Tip: To justify skin as an excretory organ, focus on the specific waste products eliminated through sweat (water, salts, urea) rather than just "sweating."