Biology Notes – Grade 10
National Curriculum Pakistan - NCP
Chapter 1: Digestive System
Internal SLO Based Questions-An in-depth look at the circulatory system, its components, and key historical contributions to our understanding of digestive system.
1. What is the chemical composition of food?
Our food consists of carbohydrates, proteins, and fats. These are very large molecules. Every cell of the body needs these molecules for its proper functioning.
2. What do you understand by the term ingestion?
Taking in food is called ingestion. For example, when we are eating or drinking anything, we are going through the process of ingestion.
3. What is digestion?
The breakdown of large food molecules like carbohydrates and proteins into smaller soluble food molecules with the help of enzymes is called digestion.
4. What is absorption?
When the food has been digested, the small molecules must pass out of the digestive tube into the blood. This process is called absorption.
5. What is egestion?
The process by which the undigested part of the food is removed from the body is called egestion.
6. Composition and Function of the Alimentary Canal
The alimentary canal consists of the mouth, oral cavity, pharynx, oesophagus, stomach, small intestine, and large intestine. It is responsible for ingestion, digestion, absorption, and egestion of undigested food.
7. Name the glands involved in the process of digestion.
The digestive glands are salivary glands, gastric glands, intestinal glands, liver, and pancreas.
8. What is the alimentary canal?
The alimentary canal is also known as the gut, digestive tract, or gastrointestinal tract. It is a continuous tube about 9 meters long in adults and is specialized at various points along its length. Each region is designed to carry out different functions in digestion, absorption, and egestion.
9. Define the mouth.
The mouth is the external opening that leads into the oral cavity or mouth cavity.
10. What is the oral cavity?
The oral cavity is surrounded by the upper and lower jaws. The upper jaw is fixed, while the lower is movable. The oral cavity contains the teeth and tongue.
11. Explain the term pharynx.
The pharynx is a passage that leads from the mouth and nasal cavity to the oesophagus and trachea. It serves as a common passage for both food and air.
12. Define and explain the term oesophagus. Also state its function.
The oesophagus is a muscular tube about 25 cm long that leads from the pharynx to the stomach. No digestion takes place in the oesophagus.
13. What is the stomach?
The stomach is the dilated part of the digestive tube. It is roughly J-shaped and transversely placed on the left side of the abdomen just beneath the diaphragm.
14. Explain the openings of the stomach.
The stomach has two openings guarded by valves: the cardiac opening and the pyloric sphincter.
15. Describe the location of the cardiac opening.
The cardiac opening is located between the oesophagus and the stomach.
16. What is the pyloric opening?
The opening of the stomach into the duodenum is called the pyloric opening.
17. What is the pyloric sphincter?
The pyloric opening is guarded by muscles called the pyloric sphincter.
18. Describe the location and functioning of the small intestine
The small intestine is small in diameter and consists of the duodenum, jejunum, and ileum. The duodenum is about 20-25 cm long, and bile from the gall bladder, hepatic duct from the liver, and pancreatic duct from the pancreas empty their secretions into it. The jejunum is about 2.5 meters long, and the ileum is about 4 meters long.
19. What is the large intestine's diameter?
The large intestine has a larger diameter compared to the small intestine, measuring approximately 6.5 centimeters. It plays a crucial role in absorbing water and electrolytes from the remaining indigestible food matter. Its wider structure facilitates the movement and temporary storage of fecal matter before elimination from the body.
20. What are the three parts of the colon?
The colon, a major part of the large intestine, is divided into three main sections: the ascending colon, the transverse colon, and the descending colon. The ascending colon travels upwards on the right side of the abdomen, the transverse colon crosses horizontally, and the descending colon moves downwards on the left side. These segments process digestive waste.
21. What is attached to the cecum?
The cecum is the first part of the large intestine, a pouch-like structure located at the junction with the small intestine. Attached to the cecum is the appendix, a small, finger-like projection. Though its exact function is unclear, the appendix is involved in immune function and can become inflamed, causing appendicitis.
22. How long is the appendix?
The appendix, a small tube extending from the cecum, typically measures around 10 centimeters in length. Its narrow structure and closed end make it susceptible to blockage and infection. It is considered a vestigial organ with a debated role in human digestion.
23. What connects the colon to the anus?
The rectum and sigmoid colon connect the colon to the anus. The sigmoid colon is an S-shaped region linking the descending colon to the rectum. The rectum temporarily stores feces before they are expelled through the anus, the terminal opening of the digestive tract.
24. What controls the elimination of waste?
The elimination of waste, or defecation, is controlled by sphincter muscles located at the end of the rectum and around the anus. These muscles contract and relax to regulate the passage of feces. The external anal sphincter allows voluntary control over bowel movements.
25. Name four associated organs of the digestive system.
The digestive system relies on several organs that aid in food breakdown and absorption but are not part of the main digestive tract. These include the teeth, which break down food mechanically; the tongue, which helps in swallowing and tasting; the salivary glands, which produce digestive enzymes; and the liver, which produces bile for fat digestion.
26. What are the four types of teeth?
Humans possess four distinct types of teeth: incisors, canines, premolars, and molars. Incisors are used for cutting food, canines for tearing, and premolars and molars for grinding and chewing food.
27. What is the function of incisors?
Incisors are the eight front teeth with sharp, chisel-like edges. They are primarily used for cutting food into smaller pieces, playing a vital role in the initial mechanical breakdown during chewing.
28. What is the function of canines?
Canines are pointed teeth located beside the incisors. Their primary function is to tear and pierce food that is too tough for incisors, such as meat.
29. What is the function of premolars and molars?
Premolars and molars are larger teeth located at the back of the mouth. Their broad surfaces are specialized for grinding and chewing food, facilitating efficient digestion by increasing the surface area for enzyme action.
30. What kind of organ is the tongue?
The tongue is a highly mobile, muscular organ in the oral cavity. It helps manipulate food, mix it with saliva, form a bolus for swallowing, and plays a significant role in speech and taste perception.
31. Where is the tongue located?
The tongue is situated primarily within the floor of the mouth cavity. Its base is attached to the hyoid bone in the neck, while its main body occupies the oral space. The upper surface, or dorsum, of the tongue is covered with papillae, some of which contain taste buds, allowing for the sensation of different tastes.
32. What helps move food around in the mouth?
The tongue's intricate network of muscles enables it to move food around within the mouth effectively. This manipulation is crucial for mixing food with saliva, which begins the chemical digestion process. The tongue also helps to position food between the teeth for chewing and grinding, ensuring thorough mechanical breakdown before swallowing.
33. What senses do taste buds help with?
Taste buds, located on the surface of the tongue and other parts of the oral cavity, are specialized sensory receptors responsible for the sense of taste, or gustation. These buds contain taste receptor cells that detect different chemical compounds in food, allowing us to perceive the five basic tastes: sweet, salty, sour, bitter, and umami.
34. Name the five basic tastes.
The human tongue is capable of detecting five primary taste qualities, which allow us to perceive the diverse flavors of food. These basic tastes are sweet (associated with sugars), salty (detected by the presence of sodium ions), sour (indicating acidity), bitter (which can signal potentially harmful substances), and umami (a savory taste elicited by glutamates and certain amino acids).
35. What do salivary glands produce?
Salivary glands are exocrine glands located in the oral cavity that produce and secrete saliva. Saliva is a complex fluid that plays several crucial roles in digestion and oral hygiene. It contains water to moisten food, mucus to lubricate it for swallowing, enzymes like amylase to begin the breakdown of carbohydrates, and antimicrobial agents to protect the mouth from infection.
36. Name the three major pairs of salivary glands.
The oral cavity is served by three major pairs of salivary glands, each located in a different region and contributing to the overall production of saliva. These are the sublingual glands (under the floor of the mouth), the submandibular glands (below either side of the tongue), and the parotid glands (the largest, found in front of and below each ear).
37. Where are the sublingual glands located?
The sublingual glands are the smallest of the three major salivary gland pairs and are located beneath the tongue, on the floor of the mouth. They primarily secrete a mucous-rich saliva, which helps to lubricate the oral cavity and facilitate swallowing. Their ducts open into the mouth along the underside of the tongue.
38. Where are the submandibular glands located?
The submandibular glands are medium-sized salivary glands situated below the mandible (lower jawbone), on either side of the face. They produce a mixed serous and mucous secretion, contributing significantly to the total volume of saliva in the mouth. Their ducts travel forward and open under the tongue.
39. Where are the parotid glands located?
The parotid glands are the largest of the salivary glands and are located in front of and slightly below each ear. They primarily secrete a serous, watery saliva rich in enzymes, particularly salivary amylase, which begins the digestion of starches in the mouth. The saliva produced by the parotid glands enters the oral cavity through the parotid duct, which opens into the cheek near the upper molars.
40. Where does saliva from the parotid gland enter the mouth?
Saliva produced by the parotid gland travels through the parotid duct (Stensen's duct) and enters the oral cavity on the inner surface of the cheek, near the upper molars. This strategic location ensures that the enzyme-rich saliva is effectively mixed with food as it is chewed in the back of the mouth, initiating the breakdown of carbohydrates.
41. What kind of organ is the liver?
The liver is a vital and complex organ in the human body, classified as a gland due to its secretory functions. It is the largest internal organ and plays a crucial role in numerous metabolic processes, including the production of bile for fat digestion, detoxification of harmful substances, synthesis of proteins, and regulation of blood glucose levels.
42. Describe the liver's appearance.
The liver is a large, somewhat wedge-shaped organ characterized by its spongy texture and rich reddish-brown color due to its extensive blood supply. It is located in the upper right portion of the abdominal cavity, beneath the diaphragm and above the stomach and intestines. Its substantial size and unique coloration are indicative of its diverse and essential functions.
43. Where is the liver located?
The liver is strategically located in the upper right quadrant of the abdominal cavity, situated beneath the diaphragm, which separates it from the chest cavity. It lies primarily above the stomach and intestines, nestled under the protection of the rib cage. This positioning allows it to efficiently process nutrients absorbed from the digestive tract before they circulate throughout the body.
44. How many main parts does the liver have?
Anatomically, the liver is divided into two main lobes: the larger right lobe and the smaller left lobe. These lobes are further subdivided into smaller sections based on blood supply and function. Although traditionally described with two main lobes, a more detailed classification recognizes four lobes based on internal structures and blood vessel distribution.
45. Which lobe of the liver is larger?
Of the two main lobes of the liver, the right lobe is significantly larger than the left lobe. The right lobe accounts for the majority of the liver's mass and performs a greater proportion of its metabolic functions. The smaller left lobe is situated more towards the left side of the upper abdomen.
46. How does blood travel through the liver?
Blood travels through the liver via numerous blood vessels, including the hepatic artery bringing oxygenated blood and the portal vein carrying nutrient-rich blood from the digestive organs. This blood then flows through a network of sinusoids lined with liver cells (hepatocytes) that process and filter it before it drains into the hepatic veins.
47. What structures transport bile from the liver to the duodenum?
Bile produced by the liver cells travels through a network of small bile ducts within the liver. These ducts merge to form larger hepatic ducts, which eventually join the cystic duct from the gallbladder to form the common bile duct. The common bile duct then delivers bile into the duodenum, the first part of the small intestine.
48. Where is the gallbladder located in relation to the liver?
The gallbladder is a small, pear-shaped organ situated just beneath the liver. It is nestled in a shallow depression on the inferior (underside) surface of the liver's right lobe. This close proximity allows for efficient storage and release of bile produced by the liver.
49. What is the function of the gallbladder?
The primary function of the gallbladder is to store and concentrate bile produced by the liver. When fats enter the small intestine, the gallbladder contracts and releases the concentrated bile through the cystic duct and common bile duct into the duodenum to aid in the digestion and absorption of lipids.
50. Where is the pancreas located in the abdomen?
The pancreas is located behind the stomach, in the upper abdomen. Its head is situated near the curve of the duodenum, while its body extends horizontally, and its tail tapers towards the spleen on the left side of the body.
51. What is the role of the pancreatic duct?
The pancreatic duct is the main duct that runs through the length of the pancreas. It collects digestive enzymes produced by the pancreatic cells and transports them into the duodenum. This duct usually joins the common bile duct before emptying its contents into the small intestine, playing a vital role in the digestion of carbohydrates, proteins, and fats.
52. What are the two main processes involved in the movement of food?
The two main processes that facilitate the movement of food through the digestive tract are swallowing (deglutition) and peristalsis. Swallowing is the initial voluntary and involuntary action that moves food from the mouth to the esophagus, while peristalsis is a series of involuntary wave-like muscle contractions that propel food along the digestive tract.
53. Briefly describe the oral preparatory phase of swallowing.
The oral preparatory phase is the initial stage of swallowing that occurs in the mouth. During this phase, the tongue manipulates the food, mixing it with saliva to form a cohesive bolus. The teeth grind the food into smaller particles, and the soft palate moves forward to prevent food from entering the nasal cavity.
54. What happens during the pharyngeal phase of swallowing?
The pharyngeal phase is a rapid, involuntary stage where the bolus passes from the mouth through the pharynx (throat) to the esophagus. Several actions occur simultaneously, including the elevation of the soft palate to block the nasal cavity, the closure of the larynx by the epiglottis to prevent aspiration into the airway, and the initiation of peristaltic contractions in the pharyngeal muscles.
55. What is the esophageal phase of swallowing?
The esophageal phase is the final involuntary stage of swallowing where the bolus is transported down the esophagus to the stomach. This movement is accomplished by peristalsis, a wave of muscular contractions that propels the bolus forward. The lower esophageal sphincter then relaxes to allow the bolus to enter the stomach.
56. Describe the process of peristalsis in the alimentary canal.
Peristalsis is a wave-like muscular contraction that occurs along the walls of the alimentary canal. Circular muscles behind the food bolus contract, constricting the passage, while longitudinal muscles ahead of the bolus relax, shortening the adjacent segment. This coordinated action propels the food forward through the digestive tract.
57. What is the role of peristalsis in the digestive system?
The primary role of peristalsis is to move ingested food and its digestive products along the entire length of the alimentary canal, from the esophagus to the anus. This rhythmic contraction ensures that food is properly processed and absorbed as it travels through the stomach and intestines.
58. Where does chemical digestion begin?
Chemical digestion starts in the oral cavity.
59. What enzyme in saliva starts carbohydrate digestion?
Salivary amylase in saliva begins the digestion of starches into smaller sugars.
60. What does saliva help to form?
Saliva helps to moisten food and form a bolus, which is a soft, easily swallowed mass of food.
61. What controls the entry of food into the stomach?
The esophageal sphincter controls the passage of food from the esophagus into the stomach.
62. What is gastric juice mainly composed of?
Gastric juice mainly consists of hydrochloric acid (HCl) and the enzyme pepsin.
63. What is the function of mucus in the stomach?
Mucus forms a coating over the stomach lining, protecting it from the corrosive action of hydrochloric acid.
64. What is the role of hydrochloric acid in the stomach?
Hydrochloric acid (HCl) in the stomach stops the action of salivary amylase and activates pepsinogen into its active form, pepsin.
65. What enzyme in the stomach digests proteins?
Pepsin is the enzyme in the stomach that begins the digestion of proteins into smaller peptides.
66. What controls the exit of chyme from the stomach?
The pyloric sphincter regulates the release of partially digested food, now called chyme, from the stomach into the duodenum.
67. Where does the majority of chemical digestion occur?
The majority of chemical digestion takes place in the small intestine, specifically in the duodenum.
68. What secretions enter the duodenum?
Bile from the liver and gallbladder, and pancreatic juice from the pancreas enter the duodenum to aid in digestion.
69. What is the function of intestinal enzymes?
Intestinal enzymes, secreted by the lining of the small intestine, continue the breakdown of carbohydrates, proteins, and fats into smaller absorbable molecules.
70. Where is bile produced and stored?
Bile is produced in the liver and stored in the gallbladder.
71. What is emulsification?
Emulsification is the process by which bile breaks down large fat globules into smaller droplets, increasing the surface area for fat-digesting enzymes to work.
72. What is pancreatic juice?
Pancreatic juice is a secretion from the pancreas containing enzymes that digest carbohydrates (pancreatic amylase), fats (lipase), and proteins (trypsin and chymotrypsin).
73. What mainly occurs in the jejunum and ileum?
The jejunum and ileum are the primary sites for the absorption of digested nutrients into the bloodstream.
74. What enzymes are present in the intestinal juice?
Intestinal juice contains various enzymes, including sucrase, lactase, maltase (for carbohydrates), peptidases (for proteins), and lipase (for fats), which complete the digestion of these nutrients.
75. What are villi and what is their function?
Villi are tiny, finger-like projections lining the inner wall of the small intestine. They greatly increase the surface area for efficient absorption of digested nutrients.
76. How are simple sugars and amino acids absorbed?
Simple sugars (like glucose) and amino acids are absorbed into the blood capillaries within the villi through a combination of diffusion and active transport.
77. How are glycerol and fatty acids absorbed?
Glycerol and fatty acids are absorbed into the lacteals (lymphatic vessels) within the villi before eventually entering the bloodstream.
78. What is mainly absorbed in the large intestine?
The large intestine primarily absorbs water and some electrolytes from the remaining indigestible material.
79. How do absorbed substances from the large intestine reach the liver?
The water and electrolytes absorbed from the large intestine pass into the blood capillaries within its walls. These capillaries drain into veins that ultimately lead to the hepatic portal vein. This vein carries the blood, now containing the absorbed substances, directly to the liver for further processing and distribution throughout the body.
80. What happens to the absorbed substances after they enter the blood?
Once absorbed into the blood, nutrients like glucose, amino acids, and fatty acids are transported to various cells and tissues throughout the body. This process of utilizing the absorbed nutrients for energy production, building new tissues, or storing them for later use is called assimilation. It is a crucial step in providing the body with the necessary resources for its functions.
81. Describe the process of defecation.
Defecation is the process by which the body eliminates undigested waste material, also known as feces or stool. The remaining waste moves through the large intestine to the rectum, where it is temporarily stored. When the rectum becomes sufficiently full, stretch receptors trigger the defecation reflex, leading to the expulsion of feces through the anus with the help of voluntary and involuntary muscle contractions.
82. Briefly outline at least four key functions of the liver.
The liver performs numerous vital functions, including the production of bile, which aids in fat digestion. It also plays a crucial role in glucose metabolism by storing excess glucose as glycogen and releasing it when needed. Furthermore, the liver converts excess amino acids into urea for excretion and synthesizes essential plasma proteins. Additionally, it detoxifies harmful substances and metabolizes drugs.
83. How does the liver handle bilirubin and old red blood cells?
The liver plays a critical role in breaking down old and damaged red blood cells. During this process, hemoglobin is converted into bilirubin, a pigment that is then incorporated into bile and eventually excreted in the feces. This process is essential for removing waste products from the breakdown of red blood cells from the bloodstream.
84. What role does the liver play in storing vitamins and minerals?
The liver serves as a storage site for several important fat-soluble vitamins, including vitamins A, D, E, and K, as well as certain water-soluble vitamins like vitamin B12. It also stores essential minerals such as iron and copper. This storage capacity allows the body to maintain a reserve of these vital nutrients when dietary intake is insufficient.
85. Describe the structure of a villus and its importance in absorption.
A villus is a finger-like projection of the small intestinal lining, covered by a single layer of columnar epithelial cells. Each villus contains a network of blood capillaries and a lymphatic vessel called a lacteal in its core. This intricate structure significantly increases the surface area available for nutrient absorption, allowing for efficient uptake of digested food molecules into the bloodstream and lymphatic system.
86. What are crypts of Lieberkühn and goblet cells?
Crypts of Lieberkühn are small tubular glands located between the bases of the villi in the small intestine. These crypts secrete intestinal juice, which contains enzymes that aid in the final stages of digestion. Goblet cells are specialized epithelial cells interspersed among the absorptive cells of the villi and lining the crypts. They secrete mucus, which lubricates the intestinal lining and protects it from digestive enzymes.
87. What are the main characteristics and causes of diarrhea?
Diarrhea is characterized by the passage of frequent, watery stools. It often results from increased motility of the lower gastrointestinal tract and reduced absorption of water. Common causes include infections (bacterial, viral, or parasitic), food poisoning, nervous stimulation, and irritants. Diarrhea can lead to dehydration and electrolyte imbalance due to the excessive loss of fluids.
88. How is mild diarrhea typically treated?
Mild cases of diarrhea are often treated with oral rehydration solutions (ORS), which contain a balanced mixture of salt and sugar to help replenish lost fluids and electrolytes. Maintaining a bland diet can also aid recovery. It's important to stay hydrated by drinking plenty of clear fluids. However, persistent or severe diarrhea may require medical attention to identify and treat the underlying cause.
89. What are the symptoms and underlying causes of constipation?
Constipation is characterized by infrequent or difficult bowel movements, often resulting in hard, dry feces. It typically occurs due to decreased motility of the large intestine, allowing more time for water to be absorbed, making the stool harder. Common causes include a diet low in fiber, inadequate fluid intake, lack of physical activity, certain medications, and ignoring the urge to defecate.
90. What are some common recommendations for preventing and treating constipation?
Prevention and treatment of constipation often involve dietary and lifestyle modifications. Increasing the intake of dietary fiber through fruits, vegetables, and whole grains helps to add bulk to the stool. Drinking plenty of fluids keeps the stool soft and easier to pass. Regular physical activity can also stimulate bowel movements. In some cases, medications or laxatives may be recommended by a healthcare professional.
91. What is an ulcer in the digestive system?
An ulcer is an open sore or lesion that occurs in the lining of the digestive tract. It is caused by the gradual disintegration of the tissue. Common locations for ulcers include the stomach (gastric ulcer), lower part of the esophagus, or the duodenum (peptic ulcer).
92. What is a major cause of ulcer formation?
A major cause of ulcer formation is often an infection with the bacterium Helicobacter pylori (H. pylori). This bacterium can damage the protective mucus layer of the digestive lining, making it susceptible to the corrosive effects of stomach acid.
93. What are some common recommendations to prevent ulcers?
Several lifestyle modifications can help prevent ulcers, including managing stress, avoiding smoking, and being cautious with the long-term use of certain medications like aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs). It's also advisable to avoid foods that seem to irritate the digestive system and limit excessive alcohol consumption.