Which of the following glands produces an oily substance that lubricates the hair and skin?

Flagella

Reasoning:

The basal body is a cellular structure that acts as the organizing center for the growth of flagella and cilia. It is structurally similar to a centriole and anchors the flagellum to the cell, providing the foundation from which the flagellum extends.

The basal body is a microtubule-based structure that functions as the foundation and organizing center for two key cellular appendages:

• Flagella: Long, whip-like structures used for movement (e.g., sperm tails).
• Cilia: Short, hair-like projections that move substances across cell surfaces or serve sensory roles (e.g., respiratory tract cilia).

Structure and Function

• Structure: Composed of nine triplet microtubules arranged in a cylindrical pattern—similar to centrioles.
• Functions:
  • Serves as a template for building the axoneme (core) of flagella and cilia.
  • Anchors these structures to the cell membrane via transition fibers.
  • Helps regulate movement patterns, such as the synchronized beating of cilia.

Why the Other Choices Are Incorrect

• 1. Nucleus: The nucleus contains DNA and is not involved in microtubule organization or flagellar function.
• 2. Ribosome: Ribosomes produce proteins and are made of RNA and protein, not microtubules.
• 3. Mitochondria: Mitochondria generate energy for the cell but are not connected to basal body formation or function.

Clinical Significance

• Primary Ciliary Dyskinesia: A genetic disorder caused by defective basal bodies or cilia, leading to impaired mucus clearance and chronic respiratory issues.
• Infertility: Faulty sperm flagella, often due to basal body dysfunction, can result in reduced motility and infertility.

The glomerulus is a key structure in each nephron, which is the functional unit of the kidney. It consists of a tuft of capillaries surrounded by Bowman’s capsule.

Main function:

• The glomerulus filters blood plasma under high pressure.
• It allows water and small solutes (like sodium, glucose, amino acids, and urea) to pass into the Bowman’s capsule, creating a fluid called glomerular filtrate.
• Large molecules and blood cells are too big to pass through and remain in the blood.

This filtrate then enters the renal tubule, where selective reabsorption and secretion take place to form urine.

Why the Other Options Are Incorrect:

1. Responds to presence of ADH to control water reabsorption and produce a concentrated urine

• Incorrect, because this describes the collecting duct, not the glomerulus.
• ADH (antidiuretic hormone) increases water reabsorption by making the collecting duct walls more permeable to water, concentrating the urine.
• The glomerulus does not respond to hormones like ADH; its role is purely filtration.

2. Reabsorbs water into the blood that increases blood pressure

• Incorrect, because water reabsorption occurs primarily in the proximal convoluted tubule, loop of Henle, and collecting duct, not in the glomerulus.
• The glomerulus only filters; it does not reabsorb water.
• While kidney function can influence blood pressure, the glomerulus itself does not directly reabsorb water to raise blood pressure.

4. Allows K⁺, Na⁺, and Cl⁻ to move out of the filtrate through both active and passive transport

• Incorrect, because this describes what happens in the loop of Henle and distal tubule.
• The glomerulus does not perform transport of ions through active or passive mechanisms; it simply filters them based on size and pressure.
• Ion regulation is a function of the tubular parts of the nephron, not the glomerulus.

Summary:

• The glomerulus acts like a sieve, initiating urine formation by filtering blood.
• The renal tubules then modify this filtrate by reabsorbing useful substances and secreting waste.

Clinical Relevance: Glomerular Function

Glomerular Filtration Rate (GFR)

• GFR is a critical indicator of kidney function.
• A low GFR may suggest renal impairment or chronic kidney disease.
• Influenced by blood pressure, hydration status, and conditions such as diabetes.

Glomerular Disorders

• Glomerulonephritis: Inflammation of the glomeruli, often presenting with protein and/or blood in the urine.
• Diabetic nephropathy: Long-term high blood sugar damages glomeruli, leading to progressive kidney dysfunction.

Nursing Considerations

• Monitor: Urine output, presence of proteinuria, and blood pressure, especially in high-risk patients.
• Educate: Patients on kidney-friendly diets—low in sodium and protein—to reduce glomerular stress.

Memory Trick
"Glomerulus = Gatekeeper"

• It filters blood, allowing water and small molecules to pass through.
• It does not reabsorb or secrete—those functions occur in the renal tubule.

A substance with a pH of 3 is 10 times more acidic than a substance with a pH of 4.

Reasoning:

1. The pH Scale Basics:
The pH scale is logarithmic, meaning each unit change represents a tenfold difference in hydrogen ion concentration [H+].

• Formula:

pH=−log[H+]

• Key Principle:
  A decrease of 1 pH unit = 10 times more acidic (10× higher [H⁺]).

2. Comparing pH 3 and pH 4:

• pH 3: [H⁺] = 10⁻³ M =0.001 M.
• pH 4: [H⁺] = 10⁻⁴ M =0.0001 M.
• Ratio: 0.001 M / 0.0001 M =10.

• Conclusion:
  pH 3 has 10 times the hydrogen ion concentration of pH 4, making it 10 times more acidic.

3. Why Other Options Are Incorrect:

• 1 & 2: Incorrect—pH 3 is acidic, not alkaline (alkaline = pH > 7).
• 3: Incorrect—A 1-unit difference on the pH scale equals a 10-fold, not 2-fold, change.

4. NOTE:

• Acidic: pH < 7 (higher [H⁺])
• Neutral: pH = 7 (e.g., pure water)
• Basic/Alkaline: pH > 7 (lower [H⁺])

Summary:
A substance with a pH of 3 is 10 times more acidic than one with a pH of 4 because the pH scale is logarithm.

Urea

Reasoning:

When proteins are broken down in the body, a waste product called ammonia is formed. Since ammonia is toxic, the body converts it into urea, a less harmful substance. Urea is then eliminated from the body primarily by the kidneys through urine, but also in small amounts by sweat glands.

Here’s how it works:

1. Protein Catabolism
   • Proteins → Amino acids → Ammonia (NH₃)
   • Ammonia is highly toxic to cells and must be removed quickly.
2. Urea Formation
   • In the liver, ammonia is converted into urea via the urea cycle.
3. Excretion via Sweat
   • While the kidneys are the main organs responsible for filtering urea into urine, the sweat glands in the skin also excrete a small amount of urea.
   • This is why sweat can have a slightly ammonia-like odor during intense exercise or in people with kidney problems.
4. Other Options Explained:
   • Water: Also excreted in sweat, but not a direct byproduct of protein breakdown.
   • Sebum: An oily secretion from sebaceous glands, unrelated to nitrogen waste.
   • Lysozymes: Enzymes that kill bacteria, present in sweat but not related to protein catabolism.

Urea is the nitrogenous waste product excreted in small amounts by sweat glands after proteins are broken down and ammonia is formed. This helps the body safely eliminate excess nitrogen

The cells are muscle cells.

Reasoning:
Mitochondria are membrane-bound organelles known as the “powerhouses” of the cell because they generate ATP (adenosine triphosphate), the primary energy currency of the cell, through a process called aerobic respiration. Cells that are highly active and require large amounts of energy will naturally have more mitochondria to support their function.

1. Muscle cells, particularly skeletal and cardiac muscle, need a continuous and substantial supply of energy for contraction and movement. For example:
   • Skeletal muscle enables voluntary movements like walking or lifting objects.
   • Cardiac muscle contracts nonstop to pump blood throughout the body.
     To meet these energy needs, muscle cells are densely packed with mitochondria.
2. The other options:
   • Epidermal cells (skin surface cells) act mainly as a protective barrier and have relatively low metabolic activity, so they do not require many mitochondria.
   • Sebaceous gland cells are involved in producing and secreting oils (sebum) to lubricate the skin and hair. While they are active in secretion, they do not require as much continuous energy as muscle cells.
   • Fat cells (adipocytes) store energy in the form of lipids but are not metabolically active enough to need large numbers of mitochondria. In fact, their role is more about energy storage than usage.

Because mitochondria are essential for producing energy, and muscle cells use significantly more energy than the other cell types listed, it is most logical for the student to conclude that the cells with the highest number of mitochondria are muscle cells. This adaptation allows muscles to contract efficiently and sustain prolonged physical activity.

Skeletal muscle cells are highly active and require a large amount of energy to support continuous and powerful contractions. Mitochondria are the "powerhouses" of the cell, producing ATP (adenosine triphosphate) through cellular respiration, which fuels muscle activity.

Explanation:

• Mitochondria(4): Abundant in skeletal muscle cells to meet high energy demands, especially during exercise or repetitive movements. The more active the muscle, the more mitochondria it contains.
• Lysosomes (1): Help break down waste but are not especially concentrated in muscle tissue.
• Centrioles (2): Involved in cell division, which is not a primary function of mature skeletal muscle cells (they are typically multinucleated and non-dividing).
• Golgi Bodies (3): Package and modify proteins, important in general cell function but not uniquely enriched in muscle cells compared to mitochondria.

Clinical Insight:

Conditions like mitochondrial myopathies involve defective mitochondria and can lead to muscle weakness and fatigue, highlighting the importance of mitochondrial health in skeletal muscle function.

Exercise & Mitochondria

• Endurance training increases mitochondrial density, enhancing muscle efficiency.

Mitochondrial Diseases

• Mitochondrial defects can lead to muscle weakness, fatigue, and exercise intolerance (e.g., mitochondrial myopathy).

Implications for Patient Care

• Monitor fatigue levels in patients with mitochondrial disorders.
• Educate patients on the benefits of aerobic exercise to support mitochondrial health.

Fun Fact:

• Cardiac muscle contains even more mitochondria than skeletal muscle—because the heart never rests!

Calcium

Reasoning:

Parathyroid hormone (PTH) is secreted by the parathyroid glands in response to low blood calcium levels (hypocalcemia). Its main role is to raise calcium levels in the blood through a coordinated response involving the bones, kidneys, and intestines.

1. How PTH Increases Blood Calcium:

• Bone Resorption:
  PTH stimulates osteoclast activity, which breaks down bone tissue and releases calcium into the bloodstream.
• Kidney Effects:
  • Enhances reabsorption of calcium in the renal tubules, reducing calcium loss in urine.
  • Stimulates the conversion of inactive vitamin D into its active form, calcitriol.
• Intestinal Absorption (Indirect):
  Calcitriol (active vitamin D) promotes greater absorption of calcium from food in the small intestine.

2. Why the Other Options Are Incorrect:

• 1. Iron:
  Regulated primarily by the hormone hepcidin, not PTH. Involved in oxygen transport (via hemoglobin).
• 3. Sodium:
  Controlled by aldosterone and atrial natriuretic peptide (ANP), not PTH.
• 4. Potassium:
  Levels are regulated by aldosterone and insulin, not affected by PTH.

3. Clinical Relevance:

• Hyperparathyroidism:
  Excess PTH leads to high blood calcium levels (hypercalcemia), which can cause kidney stones, bone weakening, and other complications.
• Hypoparathyroidism:
  Deficient PTH causes low calcium levels (hypocalcemia), resulting in muscle cramps, spasms, or tetany.

Recent findings suggest that while parasitic worm infestations (helminth infections) have traditionally been viewed as harmful, they may actually have beneficial immunomodulatory effects in the context of autoimmune diseases. These parasites can dampen the immune system's overactivity, thereby reducing the severity of conditions like Crohn’s disease, multiple sclerosis, or asthma.

Why 2 is correct:

The hypothesis originally focused on the damaging effects of worms. However, given the new evidence showing that worms can relieve symptoms of autoimmune conditions, the hypothesis should be modified to reflect that worm infestations might play a protective or regulatory role in some immune functions. This doesn’t suggest that worms are entirely beneficial, but it acknowledges a more nuanced understanding of their effect on human health.

Why the other options are incorrect:

• 1. Lack of worm infestations is the cause of some autoimmune disorders
  This is an overgeneralization. While the hygiene hypothesis suggests a link between reduced exposure to parasites and increased autoimmune conditions, saying the cause is a lack of worms is too strong and not supported by sufficient evidence.
• 3. Worm infestations exacerbate the body's immune reactions
  This is the opposite of what new research suggests. Worms appear to suppress or regulate immune responses, not exacerbate them.
• 4. Worm infestation prevents the body from immune malfunction
  This is also too broad. Worms may reduce symptoms of some disorders but do not fully prevent immune malfunctions across the board.

Proteases (also called peptidases or proteinases) are enzymes that digest or break down proteins by hydrolyzing the peptide bonds between amino acids. Since enzymes themselves are proteins, proteases can digest enzymes just like any other protein substrate.

Explanation:

What Proteases Do:

• Target proteins, including enzymes.
• Break peptide bonds.
• Convert large proteins into smaller peptides or amino acids.
• Examples: Pepsin, trypsin, chymotrypsin.

So if you put any protein — even another enzyme — in the presence of active proteases, it will get digested.

Why the Other Options Are Incorrect:

• A. Endonucleases: These cut nucleic acids (DNA or RNA) at specific internal sites. They don’t affect proteins or enzymes.
• B. Lipases: These digest lipids/fats, not proteins or enzymes.
• C. Kinases: These are enzymes that add phosphate groups to other molecules (phosphorylation). They do not digest anything.

Clinical Relevance of Proteases

Proteases in the Human Body:

• Stomach:
  • Pepsin breaks down proteins in an acidic environment (low pH).
• Pancreas & Small Intestine:
  • Trypsin and chymotrypsin function in the alkaline environment of the small intestine to continue protein digestion.
• Lysosomes (inside cells):
  • Cathepsins help break down and recycle intracellular proteins.

Medical Applications of Proteases:

• Enzyme Supplements:
  • Patients with pancreatic insufficiency (e.g., cystic fibrosis, chronic pancreatitis) may need digestive enzyme therapy.
• Protease Inhibitors in Antiviral Therapy:
  • Drugs like ritonavir are used to block viral proteases (e.g., in HIV), stopping viral replication.

Nursing Considerations:

• Monitor for Signs of Malabsorption:
  • Watch for steatorrhea (fatty stools), weight loss, and nutrient deficiencies in patients with enzyme deficiencies.
• Patient Education:
  • Teach patients to take pancreatic enzyme replacements with meals to improve digestion and nutrient absorption.

Fun Fact:

• Bacterial Proteases in Wound Care:
  • Enzymes like collagenase (from bacteria) are used in wound debridement to remove dead tissue and promote healing.

Sarcoplasmic reticulum

Reasoning:

The sarcoplasmic reticulum (SR) is a specialized type of smooth endoplasmic reticulum found in muscle cells. Its main function is to store and release calcium ions (Ca²⁺), which are crucial for muscle contraction and relaxation.

Here’s how the process works:

1. Calcium Storage:
   • In a relaxed muscle, the SR stores large amounts of calcium ions.
2. Calcium Release During Contraction:
   • When a nerve impulse (action potential) reaches the muscle fiber, it triggers the SR to release calcium into the sarcoplasm (cytoplasm of the muscle cell).
   • Calcium binds to troponin, causing a conformational change that moves tropomyosin away from the actin binding sites, allowing myosin heads to attach to actin and begin contraction.
3. Calcium Reuptake During Relaxation:
   • Once the contraction ends, calcium is actively pumped back into the SR.
   • This removal of calcium from the sarcoplasm leads to muscle relaxation.

How It Controls Muscle Contraction-Relaxation:

1.Excitation-Contraction Coupling:

• • A nerve signal triggers an action potential in the muscle fiber, which travels into theT-tubules.
  • This activatesdihydropyridine receptors (DHPR), which openryanodine receptors (RyR)on the SR, releasingCa²⁺.

2. Contraction:

• • Released Ca²⁺ binds totroponinon the thin (actin) filaments, shiftingtropomyosinto expose myosin-binding sites.
  • Myosin headsbind to actin, forming cross-bridges and generating force (sliding filament mechanism).

3. Relaxation:

• • The SR actively pumps Ca²⁺ back into its lumen usingATP-dependent Ca²⁺-ATPase (SERCA).
  • As Ca²⁺ levels drop, tropomyosin re-blocks actin, and the muscle relaxes.

Other Options Explained:

• Myosin filaments: These are motor proteins involved in contraction, not in calcium storage or release.
• Cellular cytoskeleton: Maintains cell shape and structure but plays no role in calcium ion regulation for contraction.
• Troponin complex: Binds calcium during contraction but does not store or release it.

Summary:

The sarcoplasmic reticulum acts as a calcium reservoir and regulator during the skeletal muscle contraction-relaxation cycle, making it essential for proper muscle function.

Clinical Relevance:

• Malignant hyperthermia:A life-threatening condition caused bymutant RyR receptorsthat leak excessive Ca²⁺, leading to uncontrolled muscle contractions and heat production.
• Muscle fatigue:Prolonged activity can deplete SR Ca²⁺ stores.