D313 Anatomy and Physiology II - Set 5 - Part 2

Correct Answer: Right subclavian vein

Option d is correct because lymphatic fluid from the right side of the face, neck, right upper extremity, and right thorax drains into the right lymphatic duct, which empties into the right subclavian vein. Option a is incorrect because the left subclavian vein receives lymphatic drainage from the thoracic duct, which collects lymph from the rest of the body rather than the right upper quadrant. Option b is incorrect because the inferior vena cava is a large systemic vein that returns deoxygenated blood from the lower body to the heart and does not receive direct lymphatic drainage. Option c is incorrect because the superior mesenteric vein drains blood from the small intestine and parts of the large intestine into the hepatic portal system rather than receiving lymphatic fluid.

Correct Answer: Phagocytes

Option b is correct because phagocytes are the first line of internal cellular defense that engulf and destroy invading pathogens through phagocytosis when bacteria breach the skin barrier. Option a is incorrect because antibodies are protein molecules produced by B-cells during the adaptive immune response and do not perform phagocytosis or directly engulf invading pathogens themselves. Option c is incorrect because helper T-cells are part of the adaptive immune system and regulate other immune cells through cytokine release rather than directly engulfing pathogens at infection sites. Option d is incorrect because plasma cells are differentiated B-cells that produce and secrete large quantities of antibodies during adaptive immunity, not the first responders that engulf bacteria.

Correct Answer: Dendritic cells

Option a is correct because dendritic cells are specialized antigen-presenting cells that capture pathogens at infection sites, process their antigens, and travel to regional lymph nodes to activate adaptive immunity. Option b is incorrect because natural killer cells are innate immune lymphocytes that destroy virus-infected cells and tumor cells through direct cytotoxicity rather than performing antigen presentation in lymph nodes. Option c is incorrect because neutrophils are the most abundant white blood cells that arrive first to destroy pathogens but do not typically travel to lymph nodes to present antigens to T-cells. Option d is incorrect because mast cells reside in tissues and release histamine and other inflammatory mediators during allergic responses but do not carry processed antigens to lymph nodes for presentation.

Correct Answer: Helper T-cells

Option c is correct because helper T-cells are the central coordinators of adaptive immunity, releasing cytokines that activate B-cells, cytotoxic T-cells, and macrophages to mount a full response. Option a is incorrect because cytotoxic T-cells are the effector cells that directly kill infected or abnormal cells by releasing perforins and granzymes, rather than coordinating other immune cells. Option b is incorrect because regulatory T-cells function to suppress and control immune responses to prevent autoimmunity and excessive inflammation, not to activate and coordinate immune cell types. Option d is incorrect because natural killer T-cells are a specialized subset that bridges innate and adaptive immunity but do not serve as the primary regulatory coordinators of adaptive responses.

Correct Answer: Antibodies

Option d is correct because breast milk contains maternal antibodies that provide the newborn with naturally acquired passive immunity, offering immediate protection without the infant mounting its own response. Option a is incorrect because while cytokines are signaling molecules present in breast milk, the primary immune protective component transferred to the newborn for passive immunity is antibodies specifically. Option b is incorrect because antigens are foreign molecules that trigger immune responses and are not the protective immune components transferred from mother to infant through breast milk. Option c is incorrect because complement proteins are part of the innate immune system that enhance phagocytosis but are not the primary immune component in breast milk providing passive immunity.

Correct Answer: They maintain equal air pressure between adjacent alveoli

Option b is correct because alveolar pores are small openings between adjacent alveoli that allow air to pass between them, maintaining equal air pressure and preventing uneven ventilation. Option a is incorrect because although immune cells are present in the alveoli, the primary purpose of alveolar pores is pressure equalization between adjacent air sacs rather than immune cell migration. Option c is incorrect because alveolar pores do not significantly increase gas exchange surface area since they are small passages between alveoli, not additional membrane surfaces for diffusion. Option d is incorrect because surfactant is secreted by type two alveolar cells on the alveolar surface itself, not through the pores that connect neighboring alveoli to each other.

Correct Answer: Larynx

Option c is correct because the larynx, also known as the voice box, sits just inferior to the pharynx and contains the vocal cords, but it is anatomically distinct and not part of the throat. Option a is incorrect because the trachea is the windpipe that extends below the larynx and carries air toward the bronchi, sitting further from the pharynx than the structure described. Option b is incorrect because the epiglottis is a cartilaginous flap within the larynx that covers the airway during swallowing but is not the entire structure housing the vocal cords. Option d is incorrect because the bronchi are the two main branches that split from the trachea to enter each lung and are located much further down the respiratory tract from the pharynx.

Correct Answer: Aortic and carotid bodies

Option a is correct because the aortic and carotid bodies are peripheral chemoreceptors that detect changes in blood oxygen, carbon dioxide, and pH and signal the brainstem to adjust breathing. Option b is incorrect because the hypothalamus regulates temperature and thirst while the thalamus relays sensory information, and neither functions as a peripheral chemoreceptor for blood gas monitoring. Option c is incorrect because baroreceptors detect blood pressure changes and proprioceptors detect body position and movement, neither of which directly monitors blood gas levels for breathing regulation. Option d is incorrect because while the medulla contains the respiratory centers that control breathing, it is the target receiving signals from peripheral chemoreceptors rather than acting as a sensor itself.

Correct Answer: Carbonic anhydrase

Option c is correct because carbonic anhydrase is the enzyme inside red blood cells that catalyzes the conversion of carbon dioxide and water into carbonic acid, which then dissociates into hydrogen and bicarbonate ions. Option a is incorrect because pepsin is a protein-digesting enzyme found in the stomach that breaks peptide bonds in an acidic environment and has no role in carbon dioxide transport. Option b is incorrect because lipase is a fat-digesting enzyme produced by the pancreas and stomach that breaks down triglycerides into fatty acids and has no respiratory function. Option d is incorrect because amylase is a carbohydrate-digesting enzyme found in saliva and pancreatic juice that breaks starch into sugars and is unrelated to gas transport in blood.

Correct Answer: Chloride

Option d is correct because during the chloride shift, a chloride ion moves into the red blood cell from the plasma for every bicarbonate ion that exits, maintaining electrical neutrality across the membrane. Option a is incorrect because sodium ions are primarily involved in nerve impulse transmission and fluid balance regulation and do not participate in the exchange mechanism known as the chloride shift. Option b is incorrect because potassium ions play key roles in resting membrane potential and muscle contraction but are not the ions exchanged for bicarbonate during carbon dioxide transport. Option c is incorrect because calcium ions are critical for muscle contraction and blood clotting processes but do not enter red blood cells in exchange for bicarbonate ions during the chloride shift.

Correct Answer: Hormones

Option a is correct because hormones such as antidiuretic hormone and aldosterone are the class of signaling molecules used to increase glomerular filtration rate or modify tubular reabsorption in kidneys. Option b is incorrect because neurotransmitters are chemical messengers that transmit signals across synapses between neurons and are not the primary regulators of glomerular filtration or tubular reabsorption. Option c is incorrect because cytokines are signaling molecules released by immune cells to coordinate inflammatory and immune responses rather than directly controlling kidney filtration and reabsorption rates. Option d is incorrect because while prostaglandins can influence renal blood flow locally, they are not the primary class of molecule used to regulate glomerular filtration rate and tubular reabsorption.

Correct Answer: Ammonium ions

Option b is correct because ammonium ions are diffused and secreted in the collecting ducts as part of the kidney's acid-base regulation, helping to eliminate excess hydrogen ions from the body. Option a is incorrect because bicarbonate ions are primarily reabsorbed in the proximal convoluted tubule and loop of Henle to buffer blood pH rather than being secreted in the collecting ducts. Option c is incorrect because while potassium ions are secreted in the distal tubule and collecting duct under aldosterone influence, they serve electrolyte balance rather than being the primary acid-base ions. Option d is incorrect because sodium ions are primarily reabsorbed throughout the nephron rather than secreted into the collecting duct fluid for acid-base regulation purposes.

Correct Answer: Pituitary gland

Option c is correct because the pituitary gland, specifically the posterior pituitary, releases antidiuretic hormone which acts on collecting ducts to increase water reabsorption and concentrate urine. Option a is incorrect because the adrenal gland produces aldosterone which affects sodium reabsorption in the distal tubule but does not release antidiuretic hormone for water conservation in collecting ducts. Option b is incorrect because the thyroid gland produces thyroid hormones that regulate metabolism and basal metabolic rate but has no direct role in releasing hormones that concentrate urine. Option d is incorrect because the pineal gland primarily produces melatonin to regulate sleep-wake cycles and circadian rhythms and does not release hormones that control water reabsorption in kidneys.

Correct Answer: They prevent the early release of urine

Option d is correct because the sphincters of the urinary system act as muscular valves that prevent the premature and uncontrolled release of urine from the bladder until voluntary urination occurs. Option a is incorrect because filtering waste from the blood is performed by the glomerulus within the nephrons of the kidney, not by the sphincters that control urine release from the bladder. Option b is incorrect because water reabsorption occurs along the nephron tubules, particularly in the loop of Henle and collecting ducts under hormonal influence, not at the sphincter level. Option c is incorrect because urine production occurs within the nephrons through the processes of filtration, reabsorption, and secretion, which are entirely separate from sphincter function.

Correct Answer: Bicarbonate ions

Option c is correct because the loop of Henle reabsorbs bicarbonate ions from the filtrate, which is essential for maintaining the body's acid-base balance and blood pH buffering capacity. Option a is incorrect because while chloride ions are reabsorbed in the loop of Henle through the chloride channels in the thick ascending limb, they serve electrolyte balance rather than buffering capacity. Option b is incorrect because phosphate ions serve as intracellular buffers and are filtered and partially reabsorbed in the proximal tubule, not primarily recovered as buffers in the loop of Henle. Option d is incorrect because ammonium ions are produced and secreted by kidney tubular cells to eliminate acid from the body rather than being reabsorbed from the filtrate in the loop of Henle.

Correct Answer: Hypothalamus

Option a is correct because the hypothalamus initiates the hormonal cascade by releasing gonadotropin-releasing hormone, which stimulates the anterior pituitary to secrete LH and FSH for testosterone production. Option b is incorrect because the cerebral cortex is responsible for higher cognitive functions such as thinking, decision-making, and sensory processing but does not initiate the reproductive hormonal cascade. Option c is incorrect because the anterior pituitary is the second step in the cascade that responds to hypothalamic signals by releasing gonadotropins, rather than being the initial triggering structure. Option d is incorrect because the medulla oblongata controls vital autonomic functions like heart rate, breathing, and blood pressure but does not initiate the hormonal pathway for testosterone production.

Correct Answer: To maintain a temperature below core body temperature

Option d is correct because the scrotum holds the testes outside the body to maintain a temperature slightly below core body temperature, which is essential for proper sperm development and survival. Option a is incorrect because the external location of the testes in the scrotum is not primarily about increasing blood flow, as adequate blood supply reaches the testes through the testicular arteries. Option b is incorrect because sperm storage primarily occurs in the epididymis and the external positioning of the scrotum is about temperature regulation rather than providing additional storage space. Option c is incorrect because while the testes do have some immune privilege, the primary reason for scrotal positioning is temperature regulation for spermatogenesis rather than immune cell avoidance.

Correct Answer: Luteal phase

Option c is correct because the luteal phase occurs after ovulation when the corpus luteum forms and becomes the dominant endocrine structure, primarily secreting progesterone to maintain the uterine lining. Option a is incorrect because the follicular phase occurs before ovulation when developing follicles produce estrogen to stimulate endometrial growth, not after the corpus luteum has formed. Option b is incorrect because the menstrual phase is when the endometrial lining is being shed due to declining hormone levels, occurring at the beginning of the cycle rather than after ovulation. Option d is incorrect because the proliferative phase overlaps with the follicular phase and describes the estrogen-driven rebuilding of the endometrium before ovulation, not the post-ovulatory period.

Correct Answer: Labia minora

Option d is correct because the superior and anterior portions of the labia minora extend upward and forward to encircle the clitoris, forming the prepuce and frenulum of this sensitive structure. Option a is incorrect because the labia majora are the larger outer folds of skin that border the vulva and provide protection but do not directly encircle or form a covering around the clitoris. Option b is incorrect because the mons pubis is the fatty pad of tissue over the pubic bone that provides cushioning during intercourse but does not extend to encircle the clitoris directly. Option c is incorrect because vaginal rugae are the internal folds within the vaginal canal that allow for expansion during childbirth and are not external structures that encircle the clitoris.

Correct Answer: Arrested in meiosis two

Option b is correct because the oocyte within a Graafian follicle has completed meiosis one and is currently arrested in meiosis two, where it will remain until fertilization triggers completion. Option a is incorrect because the oocyte does not complete meiosis two while still inside the follicle, as the second meiotic division is only finished upon fertilization by a sperm cell. Option c is incorrect because arrest in meiosis one describes the primary oocyte stage found in primordial and primary follicles, which occurs much earlier in development before follicular maturation. Option d is incorrect because all oocytes have already begun meiosis during fetal development, and by the Graafian follicle stage the cell has progressed well beyond the initial starting point.