B5M1 Flashcards
(235 cards)
1
Q
The foregut gives rise to which of the following structures?
A
The stomach
The foregut is an embryonic structure that develops into the upper digestive tract.
2
Q
The blood supply to the foregut is primarily provided by what artery?
A
Celiac trunk
The celiac trunk supplies blood to the foregut, including the stomach, liver, and pancreas.
3
Q
Which of the following embryonic structures gives rise to the pancreas?
A
Endoderm
The pancreas develops from the endodermal layer during embryogenesis.
4
Q
A newborn infant is diagnosed with esophageal atresia. This condition results from a developmental defect in which process?
A
Failure of the foregut to divide properly into the trachea and esophagus.
Esophageal atresia is a congenital condition affecting the esophagus.
5
Q
How does the development of the foregut contribute to the formation of the liver and pancreas?
A
The endodermal lining of the foregut forms outpouchings that differentiate into liver and pancreas.
This process is crucial for proper organ development.
6
Q
What is the name of the main duct that drains the sublingual gland?
A
Bartholin’s duct
Bartholin’s duct is responsible for draining saliva from the sublingual gland.
7
Q
Which of the following enzymes in saliva breaks down bacterial cell walls and provides antimicrobial activity?
A
Lysozyme
Lysozyme is an enzyme that helps protect the oral cavity from bacterial infections.
8
Q
Which of the following is NOT a function of the salivary glands?
A
Producing bile for fat digestion
Salivary glands do not produce bile; this is the function of the liver.
9
Q
Which of the following is the primary composition of saliva?
A
Water and electrolytes
Saliva mainly consists of water, electrolytes, and enzymes.
10
Q
Which of the following is a major role of saliva in oral health?
A
Prevents tooth decay by neutralizing acids
Saliva plays a critical role in maintaining oral health.
11
Q
How many deciduous teeth do humans have?
A
20
Deciduous teeth, also known as baby teeth, typically number 20 in children.
12
Q
Why do permanent teeth replace deciduous teeth?
A
Because they are larger and the jaw grows to accommodate more teeth
Permanent teeth are larger and replace baby teeth as the jaw develops.
13
Q
Which nerve provides general sensation to the anterior two-thirds of the tongue?
A
Lingual nerve (branch of mandibular division of trigeminal nerve)
The lingual nerve is responsible for sensory innervation of the tongue.
14
Q
Why is the raising of the soft palate essential during swallowing?
A
It prevents food from entering the nasal cavity
The soft palate elevation is crucial for proper swallowing mechanics.
15
Q
Which enzyme in saliva helps digest starches?
A
Ptyalin (α-amylase)
Ptyalin is responsible for initiating carbohydrate digestion in the mouth.
16
Q
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?
A
Medulla and lower pons
The swallowing center coordinates the complex actions of swallowing.
17
Q
Which of the following statements accurately describes the esophageal wall?
A
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.
18
Q
The intermediate filament found in both unitary and multi-unit smooth muscle includes?
A
Desmin
Desmin is a key protein in the structure of smooth muscle cells.
19
Q
The regulatory protein found in smooth muscle cells that binds with calcium to form a complex that activates the myosin light chain kinase is?
A
Calmodulin
Calmodulin plays a crucial role in smooth muscle contraction regulation.
20
Q
Which statement accurately describes the difference between smooth muscle and skeletal muscle contraction?
A
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.
21
Q
The enteric nervous system is composed of two main plexuses. Which of the following statements is true regarding these plexuses?
A
The Meissner plexus innervates the muscularis mucosa while the myenteric plexus innervates the circular and longitudinal muscles.
These plexuses regulate gastrointestinal motility and secretions.
22
Q
Which of the following is true regarding the interaction between the enteric nervous system and the autonomic nervous system?
A
The vagus nerve stimulates activity in the enteric nervous system
The vagus nerve plays a significant role in gastrointestinal function.
23
Q
Which of the following neurotransmitters is most commonly involved in inhibiting gastrointestinal smooth muscle contractions?
A
Norepinephrine
Norepinephrine acts as an inhibitory neurotransmitter in the gastrointestinal tract.
24
Q
Which of the following vessels carries nutrient-rich, deoxygenated blood from the gastrointestinal tract to the liver?
A
Portal vein
The portal vein is essential for transporting absorbed nutrients to the liver.
25
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
## Footnote
This process is crucial for lipid metabolism.
26
Which of the following cells of the stomach secrete hydrochloric acid?
Parietal
## Footnote
Parietal cells are responsible for acid secretion in the stomach.
27
Identify the 4 regions of the stomach.
Body, cardiac, fundic, and pyloric
## Footnote
These regions play distinct roles in digestion.
28
Identify the hormone secreted by the stomach that controls muscular contraction and secretions of the stomach.
Gastrin
## Footnote
Gastrin is a key hormone regulating gastric functions.
29
Where does the stomach receive its blood supply?
Coeliac axis
## Footnote
The celiac trunk branches supply the stomach with blood.
30
Gastrin secretion will stop when the stomach pH reaches _______.
1.5
## Footnote
Gastrin secretion is inhibited at low pH levels.
31
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
## Footnote
The midgut gives rise to significant portions of the gastrointestinal tract.
32
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
## Footnote
This anatomical feature is crucial for digestion.
33
These are aggregates of lymphoid tissue present in the mucous membrane of the lower ileum along its antimesenteric border.
Peyer’s Patches
## Footnote
Peyer's patches play a role in immune response in the intestine.
34
Which of the following hormones inhibit small intestinal motility?
Glucagon
## Footnote
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.
35
What happens when the cecum is distended with digested food?
The ileocecal sphincter contracts which inhibits peristalsis and delays food emptying into the
cecum
## Footnote
This reflex helps facilitate the movement of contents through the gut.
36
Which vessels become the liver sinusoids?
Paired vitelline veins and umbilical veins
## Footnote
These vessels contribute to the unique blood supply of the liver.
37
What process brings the ventral and dorsal pancreatic buds together?
Rotation of the stomach and duodenum
## Footnote
This process is essential for proper pancreatic development.
38
Which part of the pancreas is formed from the ventral bud?
Head and uncinate process
## Footnote
The ventral bud contributes to specific anatomical structures of the pancreas.
39
The hepatic bud originates at the apex of the loop of which developing structure?
Duodenum
## Footnote
The hepatic bud is crucial for liver development.
40
Which of the following statements about the hepatic artery is correct?
The hepatic artery carries oxygenated blood to the liver
## Footnote
The hepatic artery is a vital vessel supplying blood to the liver.
41
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
## Footnote
This dual blood supply is important for liver function.
42
Which of the following best describes Kupffer cells in liver histology?
Resident macrophages involved in phagocytosis and immune response
## Footnote
Kupffer cells play a critical role in liver immunity.
43
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
## Footnote
The liver has a unique role in lymph production.
44
Which nerve is responsible for the referred pain to the right shoulder in a patient with gallstones?
Phrenic nerve (C3-C5)
## Footnote
The phrenic nerve carries sensory information that can refer pain.
45
Which of the following statements best describes the anatomical position of the pancreas?
It is retroperitoneal, lying transversely at the level of L1-L2
## Footnote
The pancreas is located behind the peritoneal cavity.
46
Which pancreatic cells are responsible for insulin secretion?
Beta cells
## Footnote
Beta cells are crucial for glucose regulation in the body.
47
Venous drainage from the pancreas primarily empties into?
The portal vein
## Footnote
This drainage is vital for nutrient processing by the liver.
48
Which of the following is an endocrine function of the pancreas?
Glucagon secretion
## Footnote
The pancreas has both endocrine and exocrine functions.
49
Which of the following enzymes is secreted by the pancreas in its active form?
Lipase
## Footnote
Lipase is secreted in its active form to aid in fat digestion.
50
Which of the following is an endocrine function of the pancreas?
C. Glucagon secretion
51
Which enzyme is secreted by the pancreas in its active form?
Lipase
52
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
53
Zenker’s diverticulum is located between which structures?
Cricopharyngeus and thyropharyngeus
54
The glossopharyngeal nerve supplies which muscle that elevates the pharynx in swallowing and speech?
A. Stylopharyngeus
55
What is the layer identified by immune cells during esophageal tissue examination?
B. Submucosa
56
At what thoracic level does the esophagus lie anterior to the aorta?
T8
T4 is posterior
57
Which of the following is a primary retroperitoneal organ?
Pancreas
58
The median groove formed by the fusion of the Aponeurosis of the muscles of the Anterior Abdominal Wall is called?
Linea Alba
59
What is the ventral mesentery that extends from the lesser curvature to the liver?
Lesser Omentum
60
Which ligament connects the liver to the anterior abdominal wall?
Falciform Ligament
61
What is the remnant of the left umbilical vein located at the falciform ligament?
Ligamentum Teres Hepatis
62
What is the origin of the external oblique muscle?
Inferior border of the lower eight ribs
63
What is the most important amino acid metabolically?
Glutamine
64
A coenzyme frequently encountered in transamination reactions is?
B. Pyridoxal Phosphate
65
The carbon skeleton used to make serine is?
3-Phosphoglycerate
66
Which of the following is a source of one carbon in amino acid metabolism?
C. THF Derivative
67
The pK of the α-amino group of amino acids is around?
2
68
What is the sequence of atoms in the peptide bond backbone?
C-C-N-C
69
Which of the following amino acids is essential in mammals?
Lys
70
What is the primary nitrogen-containing waste product excreted by humans?
D. Urea
71
The Urea Cycle starts and ends with?
A. Ornithine
72
Which is the first enzyme in the urea cycle?
A. Carbamoyl phosphate synthetase 1
73
What is the primary function of goblet cells in the large intestine?
B. Secretion of mucus
74
Which part of the large intestine is most likely to be affected by inferior mesenteric artery blockage?
C. Descending colon
75
How much chyme passes through the ileocecal valve into the large intestine daily?
C. 1500 milliliters
76
What role do tight junctions in the large intestine’s epithelium play?
B. They prevent the back-diffusion of ions, maximizing sodium absorption
77
Water makes up about what percentage of the weight of feces?
C. 60-70%
78
What is the most likely explanation for unusually pale feces?
B. A problem with bilirubin metabolism or excretion
79
How is the external anal sphincter involved in defecation?
B. It is under conscious control, allowing for voluntary control of defecation
80
Where does the majority of absorption occur in the large intestine?
Proximal half of the colon
81
What is the role of the external anal sphincter in defecation?
It is under conscious control, allowing for voluntary control of defecation.
82
Where does the majority of absorption occur in the large intestine?
Proximal half of the colon.
83
Which amino acid is unlikely to be found in an α-helix due to its cyclic structure?
Proline.
84
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.
85
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.
86
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.
87
Why are complex carbohydrates generally recommended over simple sugars?
They provide a steady release of glucose along with additional vitamins and minerals.
88
What best describes carbohydrates?
The body’s most efficient fuel.
89
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.
90
Which of the following is considered a micronutrient?
Vitamins.
91
Which dietary preparations contain complex carbohydrates?
Rice, Pasta, Beans, Yam.
92
What kind of fat is considered the most dangerous?
Hydrogenated fat.
93
Which element is only found in a protein molecule and absent in both lipids and carbohydrates?
Nitrogen.
94
What change is expected in breast milk as it evolves from 'transitional' to 'mature' milk?
More lactose is synthesized.
95
What is the expected outcome in poorly nourished lactating women regarding milk characteristics?
Decreased protein concentration.
96
What is the most abundant component of whey proteins in human milk?
Alpha-lactalbumin.
97
Which compound constitutes the highest percentage of mature milk's total nutritional content?
Lactose.
98
According to the Asia-Pacific BMI classification, a BMI of 23.2 is considered?
Overweight.
99
What type of dietary fat should comprise approximately 10-20% of total kcal per day?
Polyunsaturated fat.
100
Which dietary practice excludes all animal products as well as onion, garlic, and scallions?
Veganism.
101
What is a simple approximation of energy requirement to maintain body weight of a sedentary adult?
30 kcal/kg/day.
102
How long can the body's stores of folate usually last?
4 weeks.
103
What component of Dietary Reference Intake (DRI) meets the requirements of nearly all individuals?
Recommended dietary allowance.
104
According to the Asia-Pacific BMI classification, a BMI of 18.4 is considered?
Underweight.
105
Triglycerides are composed of?
One glycerol and three fatty acids.
106
Which type of fat is considered essential for the body and must be obtained from the diet?
Polyunsaturated fats.
107
Which statement is TRUE about Vitamins A, D, E, and K?
They are stored in the body's fat tissues and liver.
108
Which food item is an example of a complete protein?
Yogurt.
109
What happens when the body consumes too much simple carbohydrates?
It can cause blood sugar spikes and can lead to obesity.
110
What is the primary benefit of consuming insoluble fiber?
It adds bulk to stool and promotes regular bowel movement.
111
Which mineral is primarily responsible for maintaining proper fluid balance and nerve function?
Potassium.
112
If the concentration of the substrate is set at 0.5 mM, which enzyme will result in a higher reaction rate?
Enzyme A.
113
A 7-year-old boy with cystic fibrosis is likely to have a deficiency in which enzyme?
Lipase.
114
What type of enzyme is pepsin?
Aspartate protease.
115
What is the biochemical cause of symptoms in a patient with lactose intolerance?
Lack of lactase, leading to lactose fermentation in the colon.
116
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.
117
What kind of inhibitor is methotrexate?
Competitive.
118
Hexokinase and glucokinase are examples of ___________.
Isozymes.
119
What role does a metal ion play in enzyme activity?
It functions as a cofactor essential for enzyme activity.
120
What is true about an uncatalyzed reaction?
It has high activation energy.
121
What is the role of arachidonic acid in relation to the COX-2 enzyme?
Substrate.
122
What happens during the conversion of ethanol to acetaldehyde?
The substrate, ethanol, is oxidized.
123
What digestive process is impaired by a pancreatic tumor affecting acinar cells?
Protein and Lipid digestion.
124
Why are digestive enzymes synthesized as inactive zymogens?
To prevent the premature digestion of pancreatic and gastric tissues.
125
How long does human breastmilk provide complete nutrition to infants?
4-6 months.
126
Which cells dominate in human breastmilk?
Macrophages.
127
What is the change in whey:casein ratio in colostrum as it becomes mature breastmilk?
90:10 → 60:40.
128
Evaporated milk is dehydrated to what percentage of its volume?
60%.
129
How long does it take to achieve mature milk?
2-3 days.
130
Which food item has the lowest fat content?
Skimmed Milk.
131
Which pharyngeal arches do the laryngeal muscles develop from?
They develop from the fourth and sixth pharyngeal arches.
132
The external acoustic meatus develops from which pharyngeal groove?
First pharyngeal groove.
133
The epithelial lining of the larynx originates from which source?
Endoderm of the laryngotracheal tube.
134
The formation of laryngeal ventricles during recanalization leads to the development of which structures?
Vocal folds.
135
Trace the blood supply of the upper trachea.
Aortic arch → Brachiocephalic artery → Common carotid artery → External carotid artery → Superior thyroid artery.
136
What are basal cells in the tracheal epithelium known for?
They are considered reserve stem cells that replace damaged cells.
137
Where is a peanut most likely to be lodged after aspiration?
Right bronchus.
138
Which anatomical landmark is most helpful in determining the end of the trachea?
Cricoid cartilage.
139
What type of epithelium is found in the bronchus?
Pseudostratified columnar.
140
Which structure forms the posterior border of the lungs?
Spine.
141
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.
142
Which structure plays a key role in the formation of the lung roots?
Trachea.
143
Which structures must be preserved during surgery involving the roots of the lungs?
Pulmonary arteries, veins, and nodes.
144
What is the functional significance of a bronchopulmonary segment?
It is the smallest subdivision of a lung lobe that can function independently.
145
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.
146
What role do type II pneumocytes play?
They synthesize and secrete surfactant, which reduces surface tension and prevents alveolar collapse.
147
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.
148
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.
149
At what week do the bronchioles for gas exchange develop?
By 24 weeks.
150
What is true about the components of the blood-air barrier?
The terminal sacs are lined by surfactant-secreting cells, Type II pneumocytes.
151
What condition is indicated by a significantly decreased FEV1% on pulmonary function testing?
The patient has an obstructive lung disease.
152
What occurs during inspiration?
Thoracic cavity volume increases.
153
What does pulmonary ventilation refer to?
The movement of air into and out of the lungs.
154
What is the effect of decreased airway resistance and increased lung elastance on ventilation?
Decreased airway resistance facilitates airflow; increased elastance impedes lung expansion.
155
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.
156
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.
157
What does the Law of Young-Laplace state?
Wall tension varies directly with the radius of curvature.
158
What summarizes the role of pulmonary surfactant?
A complex substance that lines the alveolar surface and markedly decreases surface tension.
159
What is true regarding phospholipids, particularly dipalmitoylphosphatidylcholine (DPPC)?
They are strong surface-active agents.
160
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.
161
What is true about Acute Respiratory Distress Syndrome (ARDS)?
It can be caused by shock, systemic infection, or trauma.
162
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.
163
What is the role of surfactant in reducing pulmonary capillary filtration?
Normal surfactant helps prevent pulmonary edema, which interferes with gas exchange.
164
What is most likely to cause an increase in airway resistance?
Constriction of smooth muscle in the bronchial airways.
165
What happens to airway resistance as lung volume decreases?
Airway resistance significantly increases as lung volume reduces.
166
If a person has insufficient surfactant production, what is the likely outcome?
167
What happens to airway resistance as lung volume decreases?
Airway resistance significantly increases as lung volume reduces.
## Footnote
This is due to the decrease in airway diameter as the lung volume decreases.
168
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.
## Footnote
Surfactant reduces surface tension in the alveoli, aiding in lung inflation.
169
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.
## Footnote
This intervention helps alleviate the work of breathing when respiratory muscles are fatigued.
170
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.
## Footnote
Increased resistance requires more effort to ventilate the lungs.
171
Which of the following best describes compliance work in the work of inspiration?
Work required to expand the lungs against lung and chest elastance.
## Footnote
Compliance is the ability of the lungs to stretch and expand.
172
Which lung capacity represents the maximal volume of gas expired after maximal inspiration?
Vital capacity.
## Footnote
Vital capacity is the total amount of air that can be exhaled after a full inhalation.
173
What is the normal tidal volume in an average healthy adult?
500 mL.
## Footnote
Tidal volume is the amount of air inhaled or exhaled in a normal breath.
174
According to Charles’ Law, what happens to the volume of a gas if the temperature increases at constant pressure?
It increases.
## Footnote
Charles' Law states that volume is directly proportional to temperature.
175
Which factor increases airway resistance the most?
Increased turbulent airflow.
## Footnote
Turbulent airflow is caused by high flow rates and constricted airways.
176
What is the most commonly used screening test for airway disease?
Forced vital capacity (FVC).
## Footnote
FVC measures the amount of air a person can forcibly exhale after taking a deep breath.
177
During a panic attack, how does hyperventilation affect blood pH?
Hyperventilation leads to hypocapnia, causing respiratory alkalosis.
## Footnote
This occurs due to excessive loss of CO₂, which raises blood pH.
178
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.
## Footnote
The superior mediastinum contains important structures such as the aortic arch and trachea.
179
Which statement is true about the thoracic outlet?
It is bounded laterally by the first rib and its cartilage.
## Footnote
The thoracic outlet is the space through which structures pass between the thorax and upper limb.
180
Which of the following is a characteristic of the costodiaphragmatic recess?
It is about 8–9 cm deep along the midaxillary line.
## Footnote
The costodiaphragmatic recess is the potential space between the diaphragm and the thoracic wall.
181
What is the most likely explanation for hypoxemia that does not correct with 100% oxygen?
Intrapulmonary shunt.
## Footnote
An intrapulmonary shunt occurs when blood bypasses the alveoli, preventing oxygenation.
182
What V/Q pattern is most likely present in a patient with pneumonia in the right lower lobe?
Decreased V/Q ratio.
## Footnote
Decreased V/Q ratio indicates poor ventilation relative to perfusion.
183
Under normal resting conditions, oxygen transfer in the lungs is typically:
Perfusion-limited.
## Footnote
This means that blood flow (perfusion) is the limiting factor for oxygen transfer.
184
Which region of the lung has the highest V/Q ratio in an upright individual?
Lung apex.
## Footnote
The apex has a higher V/Q ratio due to lower perfusion compared to ventilation.
185
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.
## Footnote
This response increases respiratory rate to improve oxygenation.
186
The peripheral chemoreceptors primarily detect changes in the concentration of which gas or ion in the blood?
Oxygen.
## Footnote
They respond primarily to low levels of O₂ to regulate breathing.
187
What accurately describes J receptors?
Located near pulmonary capillaries, primarily responsible for the sensation of dyspnea.
## Footnote
J receptors are sensitive to pulmonary congestion and edema.
188
What characterizes Cheyne-Stokes breathing?
A periodic breathing pattern with a crescendo-decrescendo respiration followed by apnea.
## Footnote
It is often seen in conditions affecting the brain's respiratory centers.
189
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.
## Footnote
Pulmonary fibrosis increases the thickness of the alveolar-capillary membrane, hindering gas exchange.
190
What best describes the ventilation-perfusion (V/Q) ratio?
The ratio of alveolar ventilation to pulmonary blood flow.
## Footnote
Understanding the V/Q ratio is crucial for diagnosing respiratory conditions.
191
What is the most likely cause of hypoxemia in a chronic smoker with low PaO₂/FiO₂?
Low V/Q ratio due to obstructed alveoli.
## Footnote
Chronic smoking can lead to obstructive lung diseases that impair ventilation.
192
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.
## Footnote
Pulmonary embolism blocks blood flow to parts of the lung, leading to ventilation-perfusion mismatch.
193
Which condition causes a rightward shift in the oxygen-hemoglobin dissociation curve?
Acidosis.
## Footnote
A rightward shift indicates decreased affinity of hemoglobin for oxygen, facilitating oxygen release.
194
The maximum oxygen-carrying capacity of blood is primarily determined by:
Hemoglobin concentration.
## Footnote
Hemoglobin is the key protein responsible for oxygen transport in the blood.
195
In sickle cell anemia, oxygen transport is impaired due to:
Hemoglobin polymerization at low O₂.
## Footnote
This polymerization distorts red blood cells and reduces their ability to transport oxygen.
196
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.
## Footnote
CO competes with O₂ for binding sites on hemoglobin, affecting saturation readings.
197
What is the major transport form of CO₂ in the blood?
Bicarbonate.
## Footnote
Most CO₂ is converted to bicarbonate ions in red blood cells for transport in plasma.
198
What does oxidation of hemoglobin iron from ferrous to ferric state produce?
Methemoglobin.
## Footnote
Methemoglobin cannot effectively bind oxygen, leading to functional anemia.
199
What is the role of the basement membrane in gas exchange?
Connects alveolar and capillary layers.
## Footnote
The basement membrane facilitates the diffusion of gases between alveoli and blood.
200
What most directly influences the rate of gas diffusion?
Partial pressure gradient.
## Footnote
A greater difference in partial pressures drives faster diffusion of gases.
201
Which condition most likely reduces oxygen diffusion across the membrane?
Thickened membrane.
## Footnote
A thickened membrane increases the distance oxygen must travel to enter the blood.
202
CO₂ diffuses faster than O₂ due to:
Higher solubility in body fluids.
## Footnote
CO₂ is more soluble in plasma compared to O₂, aiding its diffusion.
203
The nerves stimulating the respiratory muscles arise from:
Ventral respiratory group.
## Footnote
This group of neurons in the medulla provides the primary drive for breathing.
204
As bicarbonates leave the RBC, which ion enters to maintain neutrality?
Cl⁻.
## Footnote
This process is known as the chloride shift, maintaining ionic balance in red blood cells.
205
Which process minimizes CO₂ increase in venous blood?
Haldane effect.
## Footnote
The Haldane effect describes how deoxygenated blood can carry more CO₂.
206
Which of the following is a likely effect of nicotine in a young smoker?
Bronchiolar constriction.
## Footnote
Nicotine can lead to airway narrowing, affecting airflow.
207
At what core body temperature do symptoms of heatstroke typically begin?
105°F.
## Footnote
Heatstroke occurs when the body temperature exceeds normal regulatory limits.
208
Which type of heatstroke occurs in patients with impaired thermoregulatory mechanisms?
Classic heatstroke.
## Footnote
This type affects individuals like the elderly, who struggle to regulate body temperature.
209
Fast-twitch muscle fibers are primarily used for which type of activity?
Weightlifting and sprinting.
## Footnote
Fast-twitch fibers are designed for short bursts of power and strength.
210
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.
## Footnote
They are adapted for endurance activities.
211
Which of the following is a characteristic of red muscle fibers?
High myoglobin content.
## Footnote
Red muscle fibers are rich in myoglobin, aiding oxygen storage and utilization.
212
White muscle fibers are best suited for which of the following?
Short bursts of power and strength.
## Footnote
White fibers favor anaerobic metabolism and fatigue quickly.
213
What is the most likely explanation for early fatigue during training in a college athlete?
Accumulation of lactic acid and inorganic phosphate in muscle.
## Footnote
This accumulation is a common cause of fatigue during intense exercise.
214
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.
## Footnote
Runners rely on aerobic metabolism for endurance.
215
What type of muscle fibers are fatigue-resistant in runners?
Slow oxidative fibers
## Footnote
These fibers are characterized by high mitochondrial content.
216
Why do slow oxidative fibers in powerlifters fatigue quickly?
Due to lactate accumulation
217
Which fibers generate low force but resist fatigue in powerlifters?
Fast oxidative fibers
218
What explains the early exhaustion during activity for a 45-year-old man with COPD?
Cardiopulmonary fatigue due to poor oxygen delivery
219
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
220
What mechanism is most likely responsible for joint pain and dizziness in a diver shortly after surfacing?
Nitrogen gas embolism due to decompression
221
What is the physiologic benefit of placing a patient with CO poisoning in a hyperbaric chamber?
Increases dissolved O₂ in plasma beyond hemoglobin saturation
222
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
223
What explains fatigue and confusion reported by a pilot during long-haul flights?
Mild hypoxia from reduced partial pressure of oxygen
224
What condition explains euphoria and confusion experienced by a diver at 100 feet?
Nitrogen narcosis from high partial pressure
225
Is inspiration a passive or active process?
Active process
226
Which statement is correct regarding the mechanics of respiration?
Expiration is a passive process
227
What drives respiration as a mechanical process?
Thoracic volume changes to exchange gases
228
What influences the metabolic use of oxygen by the cell?
ATP level
229
How is the diffusion of CO₂ from cells to capillaries characterized?
Affected by tissue metabolism and perfusion
230
What happens during expiration in normal respiration?
Passive process when alveolar pressure exceeds atmospheric pressure
231
What explains confusion and tachypnea in a 29-year-old mountaineer at 15,000 ft?
Reduced barometric pressure lowers oxygen content of hemoglobin
232
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
233
What explains orthostatic intolerance in a 35-year-old astronaut after returning to Earth?
Baroreceptor desensitization and reduced sympathetic tone
234
Which change is most likely to occur in microgravity?
Redistribution of pulmonary blood flow and ventilation
235
