Important Questions (1 mark): Natural Resources - UPSC MCQ

The organic portion or protein fibers found in connective tissues are either collagen, elastic, or reticular fibers. Collagen fibers provide strength to the tissue, preventing it from being torn or separated from the surrounding tissues.

Muscles are composed of bundles of single large cells (called muscle fibers) that form by cell fusion and contain multiple nuclei. Each muscle fiber contains many myofibrils, which are bundles of actin and myosin filaments organized These bands correspond to the presence or absence of myosin filaments.

Canaliculi are found associated with:
Canaliculi are tiny channels or canals that are found in various tissues and organs in the body. These canaliculi play important roles in maintaining the health and function of the associated tissues. Specifically, canaliculi are found associated with:
A: Cartilage
- Canaliculi are present in cartilage, which is a connective tissue found in various parts of the body such as the joints, nose, and ears.
- In cartilage, canaliculi allow for the exchange of nutrients, waste products, and gases between the chondrocytes, the cells that make up the cartilage matrix.
B: Bone
- Canaliculi are also found in bone tissue, which provides structural support and protection to the body.
- In bone, canaliculi connect the lacunae, which are small spaces that contain bone cells called osteocytes.
- These canaliculi allow for the exchange of nutrients and waste products between the osteocytes and the blood vessels.
C: Muscle
- Canaliculi are not typically associated with muscle tissue.
- Muscle tissue is primarily composed of muscle fibers and does not contain canaliculi like cartilage and bone.
D: Neuron
- Canaliculi are not found in neurons, which are the functional units of the nervous system.
- Neurons have a unique structure with dendrites, cell body, and axons, but these structures do not include canaliculi.
Therefore, the correct answer is B: Bone. Canaliculi are found associated with bone tissue, allowing for communication and exchange of substances between the osteocytes and the blood vessels.

Processes from osteoblasts are found in :

• Lamella: Osteoblasts are responsible for the formation and deposition of new bone matrix, which is organized into concentric layers called lamellae.


• Canaliculi: Osteoblasts form small, branching processes called canaliculi, which connect adjacent osteocytes (mature bone cells) and allow for the exchange of nutrients and waste products.


• Dendrites: Osteoblasts do not have dendrites. Dendrites are branched extensions of nerve cells that receive and transmit electrical signals.


• Haversian canals: Osteoblasts are involved in the formation of Haversian systems, which consist of concentric layers of lamellae surrounding a central Haversian canal. However, the osteoblasts themselves are not located within the Haversian canals.

Therefore, the correct answer is B: Canaliculi. Osteoblasts play a crucial role in bone formation and maintenance, and their processes can be found in the canaliculi of bone tissue.

The bone marrow is composed of:
- Adipose tissue: Adipose tissue is the main component of bone marrow, making up a significant portion of its composition. It is responsible for storing energy in the form of fat and providing cushioning and insulation to the bones.
- Areolar tissue: Areolar tissue, also known as loose connective tissue, is found in the bone marrow. It is a type of connective tissue that provides support and flexibility to the surrounding structures.
- Blood vessels: The bone marrow contains a rich network of blood vessels that supply nutrients and oxygen to the cells within the marrow. These blood vessels also facilitate the transportation of immune cells and other important components.
- Stem cells: Bone marrow is the primary site of stem cell production and differentiation. Stem cells are responsible for generating various types of blood cells, including red blood cells, white blood cells, and platelets.
- Hematopoietic cells: Hematopoietic cells are specialized cells found in the bone marrow that give rise to different types of blood cells. These cells undergo a process called hematopoiesis, which involves their proliferation, differentiation, and maturation into functional blood cells.
- Macrophages: Macrophages are immune cells that are present in the bone marrow. They play a crucial role in engulfing and destroying foreign particles, damaged cells, and cellular debris, thus contributing to the immune response.
- Other cellular components: The bone marrow also contains other cellular components, such as fibroblasts, which produce the extracellular matrix, and osteoblasts, which are responsible for bone formation and remodeling.
Overall, the bone marrow is a complex tissue that consists of various cell types, adipose tissue, connective tissue, and blood vessels. Its composition is essential for the production and maintenance of blood cells and plays a vital role in hematopoiesis and immune function.

The Longitudinal Canals of the Bone:
The longitudinal canals of the bone are called Haversian canals.
Explanation:
The Haversian canals are an essential component of compact bone tissue. These canals run parallel to the long axis of the bone and are responsible for housing blood vessels, nerves, and connective tissue. Here's a detailed explanation of the different components:
- Haversian canals: These canals are also known as central canals or osteonic canals. They are named after the 17th-century anatomist Clopton Havers, who first described them. The Haversian canals contain blood vessels, lymphatic vessels, nerves, and loose connective tissue.
- Volkman's canals: These are also known as perforating canals. They are smaller canals that run perpendicular to the Haversian canals, connecting them to the periosteum and endosteum. Volkman's canals are responsible for transporting blood vessels and nerves from the periosteum to the Haversian canals.
- Periosteum: The periosteum is a dense connective tissue membrane that covers the outer surface of bones. It contains blood vessels, nerves, and cells involved in bone growth and repair. However, it is not a longitudinal canal of the bone.
- Endosteum: The endosteum is a thin layer of connective tissue that lines the inner surface of bones. It contains cells involved in bone remodeling and repair, but it is not a longitudinal canal of the bone.
Therefore, the correct answer is B: Haversian canals.

Volkmann's canals occur in bone.
- Volkmann's canals, also known as perforating canals, are a system of small channels that run perpendicular to the long axis of bone.
- These canals connect the Haversian canals, which contain blood vessels and nerves, with the outer surface of the bone.
- Volkmann's canals allow for the transportation of nutrients, oxygen, and waste products between the blood vessels in the periosteum and the Haversian canals.
- They also help in communication between different Haversian systems within the bone.
- Volkmann's canals are lined with endosteum, which is a thin layer of connective tissue that covers the inner surface of bone.
- They are important for maintaining bone health and function, as they ensure proper blood supply to the bone tissue.
- If Volkmann's canals become blocked or damaged, it can lead to impaired blood flow and compromised bone health.
- Common conditions associated with Volkmann's canals include osteomyelitis, fractures, and bone tumors.
- Overall, Volkmann's canals play a crucial role in the vascularization and communication within bone tissue.

A tissue is a group of similar cells that function together in a specialized activity.
Explanation:
- A tissue is a collection of cells that work together to perform a specific function.
- Tissues are the building blocks of organs and are organized to form different types of tissues in the body.
- There are four main types of tissues in the human body: epithelial, connective, muscle, and nervous tissues.
- Epithelial tissues line the surfaces or cavities of organs and provide protection and secretion.
- Connective tissues support and connect different structures in the body, such as bones, tendons, and blood vessels.
- Muscle tissues are responsible for movement and contraction.
- Nervous tissues transmit and process signals in the body.
- Each tissue type has specific characteristics and functions.
- Tissues are organized into organs, where different tissues work together to perform complex functions.
- The coordination between different tissues allows organs to carry out their specific functions and maintain homeostasis in the body.
- The study of tissues is called histology and plays a crucial role in understanding the structure and function of the human body.

Endothelium of the inner surface of blood vessels in vertebrates is formed by:

• Simple squamous epithelium: This is the correct answer. The endothelium of blood vessels is composed of a single layer of flat, thin cells, known as simple squamous epithelium. These cells are tightly packed together and form a smooth and continuous lining on the inner surface of blood vessels.


• Columnar epithelium: Incorrect. Columnar epithelium consists of tall, rectangular cells and is not found in the endothelium of blood vessels.


• Cuboidal epithelium: Incorrect. Cuboidal epithelium is made up of cube-shaped cells and is not present in the endothelium of blood vessels.


• Ciliated cells: Incorrect. Ciliated cells have hair-like projections called cilia and are not part of the endothelium of blood vessels.

Therefore, the correct answer is simple squamous epithelium (option A).

Squamous Epithelium Cells:
- Squamous epithelium cells are a type of epithelial cells that are characterized by their flat, plate-like shape.
- These cells are thin and scale-like, resembling the shape of fish scales or floor tiles.
- They are often found lining the surfaces of organs, blood vessels, and cavities throughout the body.
- Squamous epithelium cells are involved in functions such as protection, absorption, and diffusion.
- They can be found in various locations in the body, including the skin, respiratory tract, digestive tract, and urinary tract.
- The flat shape of these cells allows for efficient diffusion of substances across their surface.
- The nucleus of squamous epithelium cells is typically flattened and located towards the base of the cell.
- The cytoplasm of these cells is usually thin and contains minimal organelles.
- Squamous epithelium cells can be further classified into simple squamous epithelium (single layer) or stratified squamous epithelium (multiple layers).
Therefore, the correct answer is C: flat plate-like.

Correct Answer :- a

Explanation : Keratinised stratified squamous epithelium is a compound epithelium which covers the dry surface of  skin. It has many layers of epithelial cells .The deeper layers are formed by polygonal cells but superficial layers constitute  horny, scale like remains of dead squamous cells .Heavy deposits of the insoluble protein keratin in the dead superficial cells make the epithelium impervious to water and highly resistant to mechanical abrasions.

Horns of most mammals are composed of:
- Keratin: The main component of horns in most mammals is keratin. Keratin is a tough and fibrous protein that is also found in other parts of the body, such as hair and nails.
- Bones: While horns are not composed of bones, they do have a bony core called the horn core. The horn core is covered by a sheath of keratin, which is what we commonly refer to as the horn.
- Cartilage: Cartilage is not a major component of horns. However, it may be present in some species, such as the pronghorn antelope, where the cartilage contributes to the structure and growth of the horn.
- Chitin: Chitin is not found in mammalian horns. Chitin is a tough, flexible, and nitrogen-containing polysaccharide that is found in the exoskeletons of arthropods, such as insects and crustaceans.
In conclusion, the horns of most mammals are composed of keratin, with a bony core called the horn core. While cartilage may be present in some species, chitin is not found in mammalian horns.

Explanation:

Mammary glands are modified sweat glands, not sebaceous glands, oil glands, or lymph glands. This modification allows them to produce milk for feeding newborn offspring.

Here's a breakdown of the options:

A: Sebaceous gland
- Sebaceous glands are responsible for producing sebum, an oily substance that moisturizes and protects the skin and hair. They are not involved in milk production.
B: Sweat gland
- Sweat glands are responsible for producing sweat, which helps regulate body temperature. In the case of mammary glands, they are modified sweat glands that produce milk.
C: Oil gland
- Mammary glands are not modified oil glands. Oil glands, also known as sebaceous glands, produce sebum and are not involved in milk production.
D: Lymph gland
- Lymph glands, also known as lymph nodes, are part of the lymphatic system and play a role in immune responses. They are not involved in milk production.
Therefore, the correct answer is B: sweat gland.

Structural and Functional Performances of Tissues
Connective Tissue
- Connective tissue has a matrix that is the source of its structural and functional performances.
- The matrix is composed of extracellular material, which provides support, strength, and protection to the tissue.
- The matrix contains fibers, such as collagen and elastin, which give connective tissue its flexibility and resilience.
- Connective tissue includes various types, such as loose connective tissue, dense connective tissue, cartilage, bone, and blood.
- Each type of connective tissue has a specific matrix composition that determines its unique structural and functional properties.
Muscular Tissue
- Muscular tissue does not have a matrix that is the source of its structural and functional performances.
- Muscular tissue is composed of muscle cells, also known as muscle fibers.
- The contraction and relaxation of muscle fibers allow for movement and generate force.
- Muscular tissue includes three types: skeletal muscle, smooth muscle, and cardiac muscle.
- Each type of muscular tissue has its own characteristics and functions but does not rely on a matrix for its performance.
Nervous Tissue
- Nervous tissue does not have a matrix that is the source of its structural and functional performances.
- Nervous tissue is composed of specialized cells called neurons that transmit electrical signals.
- Neurons form networks and connections to communicate information throughout the body.
- Nervous tissue is responsible for sensory perception, motor control, and coordination of body functions.
- The performance of nervous tissue is based on the communication and electrical activity of neurons, not a matrix.
Epithelial Tissue
- Epithelial tissue does not have a matrix that is the source of its structural and functional performances.
- Epithelial tissue is composed of closely packed cells that form continuous sheets or linings.
- Epithelial tissue covers body surfaces, lines organs and cavities, and forms glands.
- Epithelial tissue functions include protection, absorption, secretion, and sensory reception.
- The performance of epithelial tissue is based on the arrangement and properties of its cells, not a matrix.
Based on the above explanations, the correct answer is Connective Tissue (A), as it is the only tissue that has a matrix that contributes to its structural and functional performances.

Explanation:

Wrinkling in old age is due to the breakdown of collagen, a key component of the skin's structure. Collagen is a protein that provides strength and elasticity to the skin, helping it to maintain its smooth and firm appearance. As we age, the production of collagen decreases, leading to a loss of elasticity and the formation of wrinkles.

Reasons:
- Wrinkling in old age is primarily due to the breakdown of collagen.
- Collagen is a protein that provides strength and elasticity to the skin.
- With age, the production of collagen decreases, leading to a loss of elasticity.
- The loss of elasticity in the skin causes wrinkles to form.
Therefore, the correct answer is A: collagen.

Dermis of mammalian skin is mainly composed of:
Connective tissue:
- The dermis is primarily made up of connective tissue, which provides support and structure to the skin.
- Connective tissue is composed of collagen fibers, elastic fibers, and ground substance.
- Collagen fibers give strength and flexibility to the skin, allowing it to resist stretching and tearing.
- Elastic fibers provide elasticity to the skin, allowing it to return to its original shape after being stretched.
Fibroblasts:
- Fibroblasts are the main cells found in the dermis that produce collagen and elastic fibers.
- They are responsible for maintaining the structural integrity of the dermis.
Blood vessels:
- The dermis contains a network of blood vessels that supply nutrients and oxygen to the skin cells.
- Blood vessels also help regulate body temperature by dilating or constricting, which can increase or decrease blood flow to the skin.
Nerve endings:
- The dermis is rich in nerve endings that allow us to perceive touch, temperature, and pain.
- These nerve endings transmit sensory information to the brain, enabling us to interact with our environment.
Appendages:
- The dermis contains various appendages, including hair follicles, sweat glands, and sebaceous glands.
- Hair follicles produce hair, sweat glands secrete sweat, and sebaceous glands produce sebum, an oily substance that moisturizes the skin.
Overall, the dermis is a complex structure composed mainly of connective tissue, which provides support, strength, and flexibility to the skin. It also contains blood vessels, nerve endings, and various appendages that contribute to the overall function and health of the skin.

Adipose tissue, or fat, is an anatomical term for loose connective tissue composed of adipocytes.

Its main role is to store energy in the form of fat, although it also cushions and insulates the body.

Obesity in animals, including humans, is not dependent on the amount of body weight, but on the amount of body fat - specifically adipose tissue.

Tendon connects
- Tendon is a tough and flexible band of fibrous tissue that connects muscle to bone.
- It plays a crucial role in transmitting the force generated by the muscle to the bone, allowing movement and providing stability to the joints.
- The correct answer is option B: bone with muscles.
Explanation:
Tendons are strong and elastic tissues that connect muscles to bones. They are composed of collagen fibers and are responsible for transmitting the force generated by the muscle to the bone, allowing movement and providing stability to the joints. Here is a breakdown of the answer choices:
A: Cartilage with muscles
- Cartilage is a flexible connective tissue found in various parts of the body, such as the joints, nose, and ears.
- While cartilage does play a role in connecting bones and providing cushioning in joints, it does not directly connect with muscles.
- Therefore, option A is incorrect.
B: Bone with muscles
- This is the correct answer. Tendons connect muscles to bones, allowing movement and providing stability to the joints.
- When a muscle contracts, it pulls on the tendon, which in turn pulls on the bone, resulting in movement.
C: Ligament with muscles
- Ligaments are another type of connective tissue, but they connect bones to other bones, not muscles.
- Ligaments help stabilize joints and prevent excessive movement.
- Therefore, option C is incorrect.
D: Bone with bone
- While bones do connect with each other at joints, tendons are the structures responsible for connecting muscles to bones.
- Therefore, option D is incorrect.
In conclusion, tendons connect muscles to bones, allowing movement and providing stability to the joints.

Cartilage is produced by:
- Chondroblasts - Chondroblasts are the cells responsible for producing cartilage. They are derived from mesenchymal stem cells and are found in the inner layer of the perichondrium, which is the connective tissue surrounding the cartilage. Chondroblasts secrete the extracellular matrix of cartilage, including collagen and proteoglycans.
Other options:
- Osteoblasts: Osteoblasts are responsible for bone formation, not cartilage production.
- Epithelium: Epithelial cells are specialized cells that line the surfaces of organs and structures in the body, but they do not produce cartilage.
- Fibroblasts: Fibroblasts are connective tissue cells that produce collagen and other components of the extracellular matrix, but they are not directly involved in cartilage production.
In summary, cartilage is produced by chondroblasts, which are specialized cells that secrete the extracellular matrix of cartilage.

Bone forming cells are osteoblasts.
Osteoblasts are responsible for bone formation and the production of new bone tissue. They play a crucial role in the development and growth of bones, as well as in bone remodeling and repair. Here is a detailed explanation of why osteoblasts are the correct answer:
Osteoblasts:
- Osteoblasts are specialized cells found in the bone.
- They are responsible for the synthesis and secretion of the organic components of the bone matrix, mainly collagen fibers.
- Osteoblasts also play a role in mineralization, as they produce and release proteins that help to initiate the deposition of calcium and other minerals onto the collagen fibers.
- They are essential for bone growth and development, as they are responsible for the formation of new bone tissue during bone growth.
- Osteoblasts are involved in bone remodeling, where they help in the removal and replacement of old bone tissue.
- They are derived from mesenchymal stem cells and are typically found on the surface of bone.
- Osteoblasts also communicate with other bone cells, such as osteocytes and osteoclasts, to maintain bone homeostasis.
Other options:
- Osteoclasts are bone-resorbing cells responsible for the breakdown and removal of old bone tissue.
- Chondroblasts are cartilage-forming cells found in the growth plates of long bones and in cartilage tissues.
- Chondroclasts are cells responsible for the breakdown and resorption of cartilage tissue.
Therefore, the correct answer is A: osteoblasts.

Importance of Bone Marrow:
Bone marrow plays a crucial role in the production of blood cells in the body. It is a soft, spongy tissue found inside the bones, primarily in the long bones and pelvic bones. The bone marrow contains stem cells that can differentiate into various types of blood cells, including red blood cells (RBCs), white blood cells (WBCs), and platelets.
Functions of Bone Marrow:
1. Production of Red Blood Cells (RBCs): RBCs are responsible for carrying oxygen to various tissues and organs in the body. The bone marrow produces RBCs through a process called erythropoiesis. Hematopoietic stem cells in the bone marrow differentiate into red blood cell precursors, which mature and enter the bloodstream.
2. Production of White Blood Cells (WBCs): WBCs are an essential part of the immune system and help in fighting against infections and diseases. Bone marrow produces different types of WBCs, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils. These cells are crucial for the body's defense mechanism.
3. Production of Platelets: Platelets are necessary for blood clotting and preventing excessive bleeding. Bone marrow produces platelets through a process called thrombopoiesis. Megakaryocytes, a type of cell in the bone marrow, undergo fragmentation to release platelets into the bloodstream.
4. Storage and Release of Stem Cells: Bone marrow acts as a reservoir for hematopoietic stem cells, which have the ability to self-renew and differentiate into different blood cell types. These stem cells can be harvested from the bone marrow for transplantation in certain medical conditions, such as bone marrow failure or leukemia.
5. Breakdown of Old or Damaged Red Blood Cells: While bone marrow is primarily involved in the production of blood cells, it also plays a role in the breakdown of old or damaged RBCs. Macrophages within the bone marrow phagocytose and break down the aged RBCs, recycling their components.
In summary, bone marrow is important for the production of RBCs, WBCs, and platelets, as well as the storage and release of stem cells. It also contributes to the breakdown of old or damaged RBCs.

Haversian system is typically found in bones of mammals.
The Haversian system, also known as osteons, is a structural unit found in compact bone tissue. It consists of several components that allow for the formation, remodeling, and repair of bones. Here is a detailed explanation of the Haversian system and its presence in mammalian bones:
Components of the Haversian system:
- Haversian canal: This is the central canal running through the core of the osteon. It contains blood vessels, nerves, and connective tissue.
- Lamellae: These are concentric layers of mineralized matrix that surround the Haversian canal. They provide strength and support to the bone.
- Osteocytes: These are mature bone cells that are located in small spaces called lacunae within the lamellae. Osteocytes maintain the bone tissue and play a role in bone remodeling.
- Canaliculi: These are tiny channels that connect the lacunae and allow for communication between osteocytes and the blood supply in the Haversian canal.
- Volkmann's canals: These are transverse canals that connect Haversian canals and allow for communication between different osteons.
Presence of the Haversian system in mammalian bones:
- Mammals have a complex skeletal system that requires strength, flexibility, and the ability to repair and remodel bone tissue. The Haversian system provides these functions.
- It is primarily found in compact bone, which is the dense outer layer of bones. Compact bone is commonly found in the long bones, such as the femur and humerus, as well as in the skull and pelvis.
- The Haversian system allows for the delivery of nutrients, oxygen, and waste removal through the blood vessels in the Haversian canals.
- It also provides a network of communication between osteocytes and allows for the exchange of signals and nutrients through the canaliculi.
- The presence of the Haversian system in mammalian bones enables bone remodeling, repair of micro-damage, and adaptation to changing mechanical stresses.
In conclusion, the Haversian system is typically found in the bones of mammals. It plays a crucial role in the structure, strength, and function of mammalian bones.

Blood is Alkaline

• Blood is classified as alkaline.


• The pH scale is used to measure the acidity or alkalinity of a substance, and it ranges from 0 to 14.


• A pH of 7 is considered neutral, below 7 is acidic, and above 7 is alkaline.


• The pH of blood is slightly alkaline, ranging between 7.35 and 7.45.


• This alkaline pH is important for the proper functioning of various physiological processes in the body.


• It allows enzymes and other proteins to maintain their optimal structure and function.


• Alkaline blood pH also helps in maintaining a healthy acid-base balance in the body.


• Any significant deviation from the normal blood pH range can have adverse effects on health.


• Various factors, such as diet, respiration, and kidney function, contribute to maintaining the alkaline pH of blood.

Therefore, the correct answer is B: Alkaline.

Mammalian erythrocytes are:
- Circular: Mammalian erythrocytes are disc-shaped cells that are rounded in appearance.
- Biconcave: They have a concave shape on both sides, giving them a biconcave appearance.
- Non-nucleated: Mammalian erythrocytes do not have a nucleus. This allows for more space to carry oxygen and increases flexibility.
- All the above: Therefore, all of the above statements are true for mammalian erythrocytes.
In summary, mammalian erythrocytes are circular, biconcave, and non-nucleated cells. These characteristics allow for efficient oxygen transport and flexibility in the bloodstream.

RBC's also known as red blood cells are formed in the bone marrow by erythropoiesis. They have an average lifespan of 120 days.  After ageing, they are selectively recognized in the spleen, liver and lymph nodes by macrophages followed by phagocytosis. This process is called eryptosis
So, the correct answer is '120 days'.