B5M1 Flashcards
The foregut gives rise to which of the following structures?
The stomach
The foregut is an embryonic structure that develops into the upper digestive tract.
The blood supply to the foregut is primarily provided by what artery?
Celiac trunk
The celiac trunk supplies blood to the foregut, including the stomach, liver, and pancreas.
Which of the following embryonic structures gives rise to the pancreas?
Endoderm
The pancreas develops from the endodermal layer during embryogenesis.
A newborn infant is diagnosed with esophageal atresia. This condition results from a developmental defect in which process?
Failure of the foregut to divide properly into the trachea and esophagus.
Esophageal atresia is a congenital condition affecting the esophagus.
How does the development of the foregut contribute to the formation of the liver and pancreas?
The endodermal lining of the foregut forms outpouchings that differentiate into liver and pancreas.
This process is crucial for proper organ development.
What is the name of the main duct that drains the sublingual gland?
Bartholin’s duct
Bartholin’s duct is responsible for draining saliva from the sublingual gland.
Which of the following enzymes in saliva breaks down bacterial cell walls and provides antimicrobial activity?
Lysozyme
Lysozyme is an enzyme that helps protect the oral cavity from bacterial infections.
Which of the following is NOT a function of the salivary glands?
Producing bile for fat digestion
Salivary glands do not produce bile; this is the function of the liver.
Which of the following is the primary composition of saliva?
Water and electrolytes
Saliva mainly consists of water, electrolytes, and enzymes.
Which of the following is a major role of saliva in oral health?
Prevents tooth decay by neutralizing acids
Saliva plays a critical role in maintaining oral health.
How many deciduous teeth do humans have?
20
Deciduous teeth, also known as baby teeth, typically number 20 in children.
Why do permanent teeth replace deciduous teeth?
Because they are larger and the jaw grows to accommodate more teeth
Permanent teeth are larger and replace baby teeth as the jaw develops.
Which nerve provides general sensation to the anterior two-thirds of the tongue?
Lingual nerve (branch of mandibular division of trigeminal nerve)
The lingual nerve is responsible for sensory innervation of the tongue.
Why is the raising of the soft palate essential during swallowing?
It prevents food from entering the nasal cavity
The soft palate elevation is crucial for proper swallowing mechanics.
Which enzyme in saliva helps digest starches?
Ptyalin (α-amylase)
Ptyalin is responsible for initiating carbohydrate digestion in the mouth.
The successive stages of the swallowing process are automatically initiated in orderly sequence and are controlled by the deglutition or swallowing center located in the?
Medulla and lower pons
The swallowing center coordinates the complex actions of swallowing.
Which of the following statements accurately describes the esophageal wall?
The lower two-thirds of the esophagus is made up of smooth muscle controlled by CN-X
The esophagus has a distinct muscle composition along its length.
The intermediate filament found in both unitary and multi-unit smooth muscle includes?
Desmin
Desmin is a key protein in the structure of smooth muscle cells.
The regulatory protein found in smooth muscle cells that binds with calcium to form a complex that activates the myosin light chain kinase is?
Calmodulin
Calmodulin plays a crucial role in smooth muscle contraction regulation.
Which statement accurately describes the difference between smooth muscle and skeletal muscle contraction?
The maximum force of contraction of smooth muscle is often greater than that of skeletal muscle.
Smooth muscle can sustain longer contractions than skeletal muscle.
The enteric nervous system is composed of two main plexuses. Which of the following statements is true regarding these plexuses?
The Meissner plexus innervates the muscularis mucosa while the myenteric plexus innervates the circular and longitudinal muscles.
These plexuses regulate gastrointestinal motility and secretions.
Which of the following is true regarding the interaction between the enteric nervous system and the autonomic nervous system?
The vagus nerve stimulates activity in the enteric nervous system
The vagus nerve plays a significant role in gastrointestinal function.
Which of the following neurotransmitters is most commonly involved in inhibiting gastrointestinal smooth muscle contractions?
Norepinephrine
Norepinephrine acts as an inhibitory neurotransmitter in the gastrointestinal tract.
Which of the following vessels carries nutrient-rich, deoxygenated blood from the gastrointestinal tract to the liver?
Portal vein
The portal vein is essential for transporting absorbed nutrients to the liver.
Where do fats absorbed from the intestinal tract go after they are absorbed by the enterocytes?
Transported via the thoracic duct to the systemic circulation
This process is crucial for lipid metabolism.
Which of the following cells of the stomach secrete hydrochloric acid?
Parietal
Parietal cells are responsible for acid secretion in the stomach.
Identify the 4 regions of the stomach.
Body, cardiac, fundic, and pyloric
These regions play distinct roles in digestion.
Identify the hormone secreted by the stomach that controls muscular contraction and secretions of the stomach.
Gastrin
Gastrin is a key hormone regulating gastric functions.
Where does the stomach receive its blood supply?
Coeliac axis
The celiac trunk branches supply the stomach with blood.
Gastrin secretion will stop when the stomach pH reaches _______.
1.5
Gastrin secretion is inhibited at low pH levels.
The derivatives of the midgut include which of the following?
The duodenum distal to the opening of the bile ducts, the jejunum, ileum, ascending colon
The midgut gives rise to significant portions of the gastrointestinal tract.
In which part of the duodenum do the main pancreatic duct and bile duct pierce the duodenal forming the ampulla?
The Second part of the duodenum
This anatomical feature is crucial for digestion.
These are aggregates of lymphoid tissue present in the mucous membrane of the lower ileum along its antimesenteric border.
Peyer’s Patches
Peyer’s patches play a role in immune response in the intestine.
Which of the following hormones inhibit small intestinal motility?
Glucagon
They include gastrin, CCK, insulin, and serotonin, all of which enhance intestinal motility and are secreted during the various
phases of food processing.
Conversely, secretin and glucagon inhibit small intestinal motility.
What happens when the cecum is distended with digested food?
The ileocecal sphincter contracts which inhibits peristalsis and delays food emptying into the
cecum
This reflex helps facilitate the movement of contents through the gut.
Which vessels become the liver sinusoids?
Paired vitelline veins and umbilical veins
These vessels contribute to the unique blood supply of the liver.
What process brings the ventral and dorsal pancreatic buds together?
Rotation of the stomach and duodenum
This process is essential for proper pancreatic development.
Which part of the pancreas is formed from the ventral bud?
Head and uncinate process
The ventral bud contributes to specific anatomical structures of the pancreas.
The hepatic bud originates at the apex of the loop of which developing structure?
Duodenum
The hepatic bud is crucial for liver development.
Which of the following statements about the hepatic artery is correct?
The hepatic artery carries oxygenated blood to the liver
The hepatic artery is a vital vessel supplying blood to the liver.
Which of the following best describes the blood supply to the liver?
The liver receives blood from both the hepatic artery and the hepatic portal vein
This dual blood supply is important for liver function.
Which of the following best describes Kupffer cells in liver histology?
Resident macrophages involved in phagocytosis and immune response
Kupffer cells play a critical role in liver immunity.
Which of the following statements is true regarding the liver and its lymphatic system?
The liver produces a significant portion of the body’s lymph, primarily from fluid filtered through the Space of Disse
The liver has a unique role in lymph production.
Which nerve is responsible for the referred pain to the right shoulder in a patient with gallstones?
Phrenic nerve (C3-C5)
The phrenic nerve carries sensory information that can refer pain.
Which of the following statements best describes the anatomical position of the pancreas?
It is retroperitoneal, lying transversely at the level of L1-L2
The pancreas is located behind the peritoneal cavity.
Which pancreatic cells are responsible for insulin secretion?
Beta cells
Beta cells are crucial for glucose regulation in the body.
Venous drainage from the pancreas primarily empties into?
The portal vein
This drainage is vital for nutrient processing by the liver.
Which of the following is an endocrine function of the pancreas?
Glucagon secretion
The pancreas has both endocrine and exocrine functions.
Which of the following enzymes is secreted by the pancreas in its active form?
Lipase
Lipase is secreted in its active form to aid in fat digestion.
Which of the following is an endocrine function of the pancreas?
C. Glucagon secretion
Which enzyme is secreted by the pancreas in its active form?
Lipase
Thirdy, a neuroscientist, discussed how ordinary memories are usually stored in the
hippocampus. However, when these memories are tied with emotions and smell, they can be stored in the amygdala (responsible for powerful emotions and fear), and this is sometimes used to explain the mechanism of comfort eating as stress relief, as scent, emotion, and memory are intertwined. Which of the following is least likely to influence chewing?
Nucleus accumbens
Other choices are pons, rostral medulla, reticular formation
Zenker’s diverticulum is located between which structures?
Cricopharyngeus and thyropharyngeus
The glossopharyngeal nerve supplies which muscle that elevates the pharynx in swallowing and speech?
A. Stylopharyngeus
What is the layer identified by immune cells during esophageal tissue examination?
B. Submucosa
At what thoracic level does the esophagus lie anterior to the aorta?
T8
T4 is posterior
Which of the following is a primary retroperitoneal organ?
Pancreas
The median groove formed by the fusion of the Aponeurosis of the muscles of the Anterior Abdominal Wall is called?
Linea Alba
What is the ventral mesentery that extends from the lesser curvature to the liver?
Lesser Omentum
Which ligament connects the liver to the anterior abdominal wall?
Falciform Ligament
What is the remnant of the left umbilical vein located at the falciform ligament?
Ligamentum Teres Hepatis
What is the origin of the external oblique muscle?
Inferior border of the lower eight ribs
What is the most important amino acid metabolically?
Glutamine
A coenzyme frequently encountered in transamination reactions is?
B. Pyridoxal Phosphate
The carbon skeleton used to make serine is?
3-Phosphoglycerate
Which of the following is a source of one carbon in amino acid metabolism?
C. THF Derivative
The pK of the α-amino group of amino acids is around?
2
What is the sequence of atoms in the peptide bond backbone?
C-C-N-C
Which of the following amino acids is essential in mammals?
Lys
What is the primary nitrogen-containing waste product excreted by humans?
D. Urea
The Urea Cycle starts and ends with?
A. Ornithine
Which is the first enzyme in the urea cycle?
A. Carbamoyl phosphate synthetase 1
What is the primary function of goblet cells in the large intestine?
B. Secretion of mucus
Which part of the large intestine is most likely to be affected by inferior mesenteric artery blockage?
C. Descending colon
How much chyme passes through the ileocecal valve into the large intestine daily?
C. 1500 milliliters
What role do tight junctions in the large intestine’s epithelium play?
B. They prevent the back-diffusion of ions, maximizing sodium absorption
Water makes up about what percentage of the weight of feces?
C. 60-70%
What is the most likely explanation for unusually pale feces?
B. A problem with bilirubin metabolism or excretion
How is the external anal sphincter involved in defecation?
B. It is under conscious control, allowing for voluntary control of defecation
Where does the majority of absorption occur in the large intestine?
Proximal half of the colon
What is the role of the external anal sphincter in defecation?
It is under conscious control, allowing for voluntary control of defecation.
Where does the majority of absorption occur in the large intestine?
Proximal half of the colon.
Which amino acid is unlikely to be found in an α-helix due to its cyclic structure?
Proline.
Which component is most critical to include in a culturally sensitive nutrition intervention program?
Nutritional education that incorporates culturally relevant food choices and locally available, nutrient-rich ingredients.
Assess the statement: ‘Implementing vegetarian diets in teenage girls is always beneficial for health.’
It can be misleading since such dietary practices may sometimes indicate disordered eating behaviors or nutrient imbalances.
What is a potential drawback of using food as a reward for children?
It may increase the desirability of less healthy foods, leading to poor eating habits over time.
Why are complex carbohydrates generally recommended over simple sugars?
They provide a steady release of glucose along with additional vitamins and minerals.
What best describes carbohydrates?
The body’s most efficient fuel.
What does the Minimum Daily Requirement (MDR) refer to?
The amount of a nutrient needed each day by a person with no special metabolic needs.
Which of the following is considered a micronutrient?
Vitamins.
Which dietary preparations contain complex carbohydrates?
Rice, Pasta, Beans, Yam.
What kind of fat is considered the most dangerous?
Hydrogenated fat.
Which element is only found in a protein molecule and absent in both lipids and carbohydrates?
Nitrogen.
What change is expected in breast milk as it evolves from ‘transitional’ to ‘mature’ milk?
More lactose is synthesized.
What is the expected outcome in poorly nourished lactating women regarding milk characteristics?
Decreased protein concentration.
What is the most abundant component of whey proteins in human milk?
Alpha-lactalbumin.
Which compound constitutes the highest percentage of mature milk’s total nutritional content?
Lactose.
According to the Asia-Pacific BMI classification, a BMI of 23.2 is considered?
Overweight.
What type of dietary fat should comprise approximately 10-20% of total kcal per day?
Polyunsaturated fat.
Which dietary practice excludes all animal products as well as onion, garlic, and scallions?
Veganism.
What is a simple approximation of energy requirement to maintain body weight of a sedentary adult?
30 kcal/kg/day.
How long can the body’s stores of folate usually last?
4 weeks.
What component of Dietary Reference Intake (DRI) meets the requirements of nearly all individuals?
Recommended dietary allowance.
According to the Asia-Pacific BMI classification, a BMI of 18.4 is considered?
Underweight.
Triglycerides are composed of?
One glycerol and three fatty acids.
Which type of fat is considered essential for the body and must be obtained from the diet?
Polyunsaturated fats.
Which statement is TRUE about Vitamins A, D, E, and K?
They are stored in the body’s fat tissues and liver.
Which food item is an example of a complete protein?
Yogurt.
What happens when the body consumes too much simple carbohydrates?
It can cause blood sugar spikes and can lead to obesity.
What is the primary benefit of consuming insoluble fiber?
It adds bulk to stool and promotes regular bowel movement.
Which mineral is primarily responsible for maintaining proper fluid balance and nerve function?
Potassium.
If the concentration of the substrate is set at 0.5 mM, which enzyme will result in a higher reaction rate?
Enzyme A.
A 7-year-old boy with cystic fibrosis is likely to have a deficiency in which enzyme?
Lipase.
What type of enzyme is pepsin?
Aspartate protease.
What is the biochemical cause of symptoms in a patient with lactose intolerance?
Lack of lactase, leading to lactose fermentation in the colon.
What characterizes an enzyme obeying Michaelis-Menten kinetics?
The enzyme velocity is at one-half the maximal rate when 50% of the enzyme molecules contain bound substrate.
What kind of inhibitor is methotrexate?
Competitive.
Hexokinase and glucokinase are examples of ___________.
Isozymes.
What role does a metal ion play in enzyme activity?
It functions as a cofactor essential for enzyme activity.
What is true about an uncatalyzed reaction?
It has high activation energy.
What is the role of arachidonic acid in relation to the COX-2 enzyme?
Substrate.
What happens during the conversion of ethanol to acetaldehyde?
The substrate, ethanol, is oxidized.
What digestive process is impaired by a pancreatic tumor affecting acinar cells?
Protein and Lipid digestion.
Why are digestive enzymes synthesized as inactive zymogens?
To prevent the premature digestion of pancreatic and gastric tissues.
How long does human breastmilk provide complete nutrition to infants?
4-6 months.
Which cells dominate in human breastmilk?
Macrophages.
What is the change in whey:casein ratio in colostrum as it becomes mature breastmilk?
90:10 → 60:40.
Evaporated milk is dehydrated to what percentage of its volume?
60%.
How long does it take to achieve mature milk?
2-3 days.
Which food item has the lowest fat content?
Skimmed Milk.
Which pharyngeal arches do the laryngeal muscles develop from?
They develop from the fourth and sixth pharyngeal arches.
The external acoustic meatus develops from which pharyngeal groove?
First pharyngeal groove.
The epithelial lining of the larynx originates from which source?
Endoderm of the laryngotracheal tube.
The formation of laryngeal ventricles during recanalization leads to the development of which structures?
Vocal folds.
Trace the blood supply of the upper trachea.
Aortic arch → Brachiocephalic artery → Common carotid artery → External carotid artery → Superior thyroid artery.
What are basal cells in the tracheal epithelium known for?
They are considered reserve stem cells that replace damaged cells.
Where is a peanut most likely to be lodged after aspiration?
Right bronchus.
Which anatomical landmark is most helpful in determining the end of the trachea?
Cricoid cartilage.
What type of epithelium is found in the bronchus?
Pseudostratified columnar.
Which structure forms the posterior border of the lungs?
Spine.
What accurately describes the pleural surfaces of the lungs?
Visceral pleura covers the outer surface of the lungs, while parietal pleura lines the chest cavity.
Which structure plays a key role in the formation of the lung roots?
Trachea.
Which structures must be preserved during surgery involving the roots of the lungs?
Pulmonary arteries, veins, and nodes.
What is the functional significance of a bronchopulmonary segment?
It is the smallest subdivision of a lung lobe that can function independently.
What is the correct sequence describing the branching pattern of the respiratory tree?
Lobar bronchi → Segmental bronchi → Terminal bronchioles → Respiratory bronchioles → Alveolar ducts → Alveolar sacs.
What role do type II pneumocytes play?
They synthesize and secrete surfactant, which reduces surface tension and prevents alveolar collapse.
How does the blood-gas barrier in the alveolus facilitate efficient gas exchange?
It consists of different structures, all of which are extremely thin to allow efficient diffusion.
After performing the Heimlich maneuver, where are food particles likely lodged in a choking situation?
Food particles were likely lodged in the larger, more vertical right bronchus.
At what week do the bronchioles for gas exchange develop?
By 24 weeks.
What is true about the components of the blood-air barrier?
The terminal sacs are lined by surfactant-secreting cells, Type II pneumocytes.
What condition is indicated by a significantly decreased FEV1% on pulmonary function testing?
The patient has an obstructive lung disease.
What occurs during inspiration?
Thoracic cavity volume increases.
What does pulmonary ventilation refer to?
The movement of air into and out of the lungs.
What is the effect of decreased airway resistance and increased lung elastance on ventilation?
Decreased airway resistance facilitates airflow; increased elastance impedes lung expansion.
Calculate the minute ventilation for a tidal volume of 500 mL and respiratory rate of 12 breaths per minute.
6,000 mL/min; within normal range.
What accurately describes tissue forces in the lungs?
Elastin fibers are stretched at low and medium lung volumes, and collagen prevents overdistention of the lungs at high lung volumes.
What does the Law of Young-Laplace state?
Wall tension varies directly with the radius of curvature.
What summarizes the role of pulmonary surfactant?
A complex substance that lines the alveolar surface and markedly decreases surface tension.
What is true regarding phospholipids, particularly dipalmitoylphosphatidylcholine (DPPC)?
They are strong surface-active agents.
What is true regarding Respiratory Distress Syndrome (RDS)?
Gas exchange is impaired in infants with RDS due to alveolar instability and areas of edema and hemorrhage within the lungs.
What is true about Acute Respiratory Distress Syndrome (ARDS)?
It can be caused by shock, systemic infection, or trauma.
What best describes tissue interdependence in the lungs?
The tendency of a lung segment to collapse is counteracted by tension generated in adjacent alveolar walls.
What is the role of surfactant in reducing pulmonary capillary filtration?
Normal surfactant helps prevent pulmonary edema, which interferes with gas exchange.
What is most likely to cause an increase in airway resistance?
Constriction of smooth muscle in the bronchial airways.
What happens to airway resistance as lung volume decreases?
Airway resistance significantly increases as lung volume reduces.
If a person has insufficient surfactant production, what is the likely outcome?
What happens to airway resistance as lung volume decreases?
Airway resistance significantly increases as lung volume reduces.
This is due to the decrease in airway diameter as the lung volume decreases.
If a person has insufficient surfactant production, what is the likely consequence on alveolar function?
Alveolar compliance would decrease, making it more difficult to inflate the lungs and increasing the risk of alveolar collapse.
Surfactant reduces surface tension in the alveoli, aiding in lung inflation.
What would be an appropriate intervention for a person experiencing ‘pump failure’ in the respiratory muscles?
Providing mechanical ventilation or respiratory support to assist with breathing.
This intervention helps alleviate the work of breathing when respiratory muscles are fatigued.
How might increased airway resistance affect energy expenditure during exercise?
It would increase the energy required for breathing, making it harder to perform at higher intensities.
Increased resistance requires more effort to ventilate the lungs.
Which of the following best describes compliance work in the work of inspiration?
Work required to expand the lungs against lung and chest elastance.
Compliance is the ability of the lungs to stretch and expand.
Which lung capacity represents the maximal volume of gas expired after maximal inspiration?
Vital capacity.
Vital capacity is the total amount of air that can be exhaled after a full inhalation.
What is the normal tidal volume in an average healthy adult?
500 mL.
Tidal volume is the amount of air inhaled or exhaled in a normal breath.
According to Charles’ Law, what happens to the volume of a gas if the temperature increases at constant pressure?
It increases.
Charles’ Law states that volume is directly proportional to temperature.
Which factor increases airway resistance the most?
Increased turbulent airflow.
Turbulent airflow is caused by high flow rates and constricted airways.
What is the most commonly used screening test for airway disease?
Forced vital capacity (FVC).
FVC measures the amount of air a person can forcibly exhale after taking a deep breath.
During a panic attack, how does hyperventilation affect blood pH?
Hyperventilation leads to hypocapnia, causing respiratory alkalosis.
This occurs due to excessive loss of CO₂, which raises blood pH.
Which statement is correct regarding the superior mediastinum?
It is bounded superiorly by an imaginary line drawn from the sternal angle to the lower border of T4.
The superior mediastinum contains important structures such as the aortic arch and trachea.
Which statement is true about the thoracic outlet?
It is bounded laterally by the first rib and its cartilage.
The thoracic outlet is the space through which structures pass between the thorax and upper limb.
Which of the following is a characteristic of the costodiaphragmatic recess?
It is about 8–9 cm deep along the midaxillary line.
The costodiaphragmatic recess is the potential space between the diaphragm and the thoracic wall.
What is the most likely explanation for hypoxemia that does not correct with 100% oxygen?
Intrapulmonary shunt.
An intrapulmonary shunt occurs when blood bypasses the alveoli, preventing oxygenation.
What V/Q pattern is most likely present in a patient with pneumonia in the right lower lobe?
Decreased V/Q ratio.
Decreased V/Q ratio indicates poor ventilation relative to perfusion.
Under normal resting conditions, oxygen transfer in the lungs is typically:
Perfusion-limited.
This means that blood flow (perfusion) is the limiting factor for oxygen transfer.
Which region of the lung has the highest V/Q ratio in an upright individual?
Lung apex.
The apex has a higher V/Q ratio due to lower perfusion compared to ventilation.
What happens to peripheral chemoreceptors during hypoxemia?
A decrease in O₂ in the blood stimulates the peripheral chemoreceptors, which in turn stimulate the respiratory centers.
This response increases respiratory rate to improve oxygenation.
The peripheral chemoreceptors primarily detect changes in the concentration of which gas or ion in the blood?
Oxygen.
They respond primarily to low levels of O₂ to regulate breathing.
What accurately describes J receptors?
Located near pulmonary capillaries, primarily responsible for the sensation of dyspnea.
J receptors are sensitive to pulmonary congestion and edema.
What characterizes Cheyne-Stokes breathing?
A periodic breathing pattern with a crescendo-decrescendo respiration followed by apnea.
It is often seen in conditions affecting the brain’s respiratory centers.
What is the most likely mechanism of hypoxemia in a patient with pulmonary fibrosis and a widened A-a gradient?
Diffusion-limited gas exchange due to thickened respiratory membrane.
Pulmonary fibrosis increases the thickness of the alveolar-capillary membrane, hindering gas exchange.
What best describes the ventilation-perfusion (V/Q) ratio?
The ratio of alveolar ventilation to pulmonary blood flow.
Understanding the V/Q ratio is crucial for diagnosing respiratory conditions.
What is the most likely cause of hypoxemia in a chronic smoker with low PaO₂/FiO₂?
Low V/Q ratio due to obstructed alveoli.
Chronic smoking can lead to obstructive lung diseases that impair ventilation.
What is the most likely diagnosis for a patient who develops sudden dyspnea and hypoxemia with V/Q scan showing ventilation without perfusion?
Pulmonary embolism.
Pulmonary embolism blocks blood flow to parts of the lung, leading to ventilation-perfusion mismatch.
Which condition causes a rightward shift in the oxygen-hemoglobin dissociation curve?
Acidosis.
A rightward shift indicates decreased affinity of hemoglobin for oxygen, facilitating oxygen release.
The maximum oxygen-carrying capacity of blood is primarily determined by:
Hemoglobin concentration.
Hemoglobin is the key protein responsible for oxygen transport in the blood.
In sickle cell anemia, oxygen transport is impaired due to:
Hemoglobin polymerization at low O₂.
This polymerization distorts red blood cells and reduces their ability to transport oxygen.
What explains the discrepancy in a patient with CO poisoning who has normal PaO₂ but elevated COHb?
Pulse oximeter overestimates O₂ saturation in CO poisoning.
CO competes with O₂ for binding sites on hemoglobin, affecting saturation readings.
What is the major transport form of CO₂ in the blood?
Bicarbonate.
Most CO₂ is converted to bicarbonate ions in red blood cells for transport in plasma.
What does oxidation of hemoglobin iron from ferrous to ferric state produce?
Methemoglobin.
Methemoglobin cannot effectively bind oxygen, leading to functional anemia.
What is the role of the basement membrane in gas exchange?
Connects alveolar and capillary layers.
The basement membrane facilitates the diffusion of gases between alveoli and blood.
What most directly influences the rate of gas diffusion?
Partial pressure gradient.
A greater difference in partial pressures drives faster diffusion of gases.
Which condition most likely reduces oxygen diffusion across the membrane?
Thickened membrane.
A thickened membrane increases the distance oxygen must travel to enter the blood.
CO₂ diffuses faster than O₂ due to:
Higher solubility in body fluids.
CO₂ is more soluble in plasma compared to O₂, aiding its diffusion.
The nerves stimulating the respiratory muscles arise from:
Ventral respiratory group.
This group of neurons in the medulla provides the primary drive for breathing.
As bicarbonates leave the RBC, which ion enters to maintain neutrality?
Cl⁻.
This process is known as the chloride shift, maintaining ionic balance in red blood cells.
Which process minimizes CO₂ increase in venous blood?
Haldane effect.
The Haldane effect describes how deoxygenated blood can carry more CO₂.
Which of the following is a likely effect of nicotine in a young smoker?
Bronchiolar constriction.
Nicotine can lead to airway narrowing, affecting airflow.
At what core body temperature do symptoms of heatstroke typically begin?
105°F.
Heatstroke occurs when the body temperature exceeds normal regulatory limits.
Which type of heatstroke occurs in patients with impaired thermoregulatory mechanisms?
Classic heatstroke.
This type affects individuals like the elderly, who struggle to regulate body temperature.
Fast-twitch muscle fibers are primarily used for which type of activity?
Weightlifting and sprinting.
Fast-twitch fibers are designed for short bursts of power and strength.
Which statement is true about slow-twitch fibers compared to fast-twitch fibers?
Slow-twitch fibers are more efficient in using oxygen to generate energy.
They are adapted for endurance activities.
Which of the following is a characteristic of red muscle fibers?
High myoglobin content.
Red muscle fibers are rich in myoglobin, aiding oxygen storage and utilization.
White muscle fibers are best suited for which of the following?
Short bursts of power and strength.
White fibers favor anaerobic metabolism and fatigue quickly.
What is the most likely explanation for early fatigue during training in a college athlete?
Accumulation of lactic acid and inorganic phosphate in muscle.
This accumulation is a common cause of fatigue during intense exercise.
Which statement is correct regarding muscle fiber types in a long-distance runner compared to a powerlifter?
Slow oxidative fibers in runners are fatigue-resistant due to high mitochondrial content.
Runners rely on aerobic metabolism for endurance.
What type of muscle fibers are fatigue-resistant in runners?
Slow oxidative fibers
These fibers are characterized by high mitochondrial content.
Why do slow oxidative fibers in powerlifters fatigue quickly?
Due to lactate accumulation
Which fibers generate low force but resist fatigue in powerlifters?
Fast oxidative fibers
What explains the early exhaustion during activity for a 45-year-old man with COPD?
Cardiopulmonary fatigue due to poor oxygen delivery
What is the most likely explanation for muscle weakness and slowed contraction after repeated maximal isometric contractions?
Manifestation of fatigue with reduced force and contractile speed
What mechanism is most likely responsible for joint pain and dizziness in a diver shortly after surfacing?
Nitrogen gas embolism due to decompression
What is the physiologic benefit of placing a patient with CO poisoning in a hyperbaric chamber?
Increases dissolved O₂ in plasma beyond hemoglobin saturation
What is the most likely cause of reduced exercise tolerance and orthostatic hypotension in a 38-year-old astronaut?
Loss of gravitational stimulus causing cardiovascular deconditioning
What explains fatigue and confusion reported by a pilot during long-haul flights?
Mild hypoxia from reduced partial pressure of oxygen
What condition explains euphoria and confusion experienced by a diver at 100 feet?
Nitrogen narcosis from high partial pressure
Is inspiration a passive or active process?
Active process
Which statement is correct regarding the mechanics of respiration?
Expiration is a passive process
What drives respiration as a mechanical process?
Thoracic volume changes to exchange gases
What influences the metabolic use of oxygen by the cell?
ATP level
How is the diffusion of CO₂ from cells to capillaries characterized?
Affected by tissue metabolism and perfusion
What happens during expiration in normal respiration?
Passive process when alveolar pressure exceeds atmospheric pressure
What explains confusion and tachypnea in a 29-year-old mountaineer at 15,000 ft?
Reduced barometric pressure lowers oxygen content of hemoglobin
What is the likely cause of decreased exercise tolerance in a 40-year-old astronaut after months in microgravity?
Redistribution of ventilation and perfusion due to gravity loss
What explains orthostatic intolerance in a 35-year-old astronaut after returning to Earth?
Baroreceptor desensitization and reduced sympathetic tone
Which change is most likely to occur in microgravity?
Redistribution of pulmonary blood flow and ventilation
