D313 Anatomy and Physiology II - Set 5 - Part 1

Correct Answer: Hemoglobin would permanently lose its ability to carry oxygen molecules at all

Option c is correct because according to Boyle's Law, as thoracic volume increases due to diaphragm contraction, intrapulmonary pressure drops below atmospheric pressure, creating a gradient that draws air inward. Option a is incorrect because when the diaphragm contracts and thoracic volume increases, the pressure inside the lungs actually decreases rather than increases, which is the opposite of what occurs. Option b is incorrect because during normal quiet inhalation, air is not actively pushed into the lungs by external muscles but rather drawn in passively by a negative pressure gradient. Option d is incorrect because oxygen does not enter the lungs by diffusing through the chest wall during normal breathing but instead flows through the airways due to pressure differences.

Correct Answer: Alveolar macrophages

Option d is correct because alveolar macrophages reside on the walls of the alveoli and serve as immune defenders by phagocytizing inhaled debris, dust, and pathogens to keep lungs clean. Option a is incorrect because parietal cells are found in the stomach lining and secrete hydrochloric acid for protein digestion, having no role in the respiratory immune defense system. Option b is incorrect because goblet cells secrete mucus to trap particles in the airways but are not the specialized phagocytic cells found within the alveoli responsible for removing debris. Option c is incorrect because ciliated epithelial cells line the upper airways and move mucus upward through wave-like motions but do not perform phagocytosis within the alveoli themselves.

Correct Answer: Carbaminohemoglobin

Option c is correct because carbaminohemoglobin is the specific compound formed when carbon dioxide molecules bind directly to hemoglobin proteins inside red blood cells for transport back to the lungs. Option a is incorrect because oxyhemoglobin is the compound formed when oxygen binds to hemoglobin, not carbon dioxide, and it represents the oxygen-loaded state of the molecule. Option b is incorrect because bicarbonate ions are formed when carbon dioxide reacts with water inside red blood cells through carbonic anhydrase, not by direct binding to hemoglobin. Option d is incorrect because carboxyhemoglobin refers to carbon monoxide bound to hemoglobin, which is a toxic condition, not the normal transport form of carbon dioxide in blood.

Correct Answer: Aortic body

Option a is correct because the aortic body is a peripheral chemoreceptor that monitors the partial pressure of carbon dioxide, oxygen, and pH levels in arterial blood flowing through the aorta. Option b is incorrect because the hypothalamus regulates many homeostatic functions including temperature and thirst but is not the peripheral chemoreceptor monitoring blood gas partial pressures directly. Option c is incorrect because the carotid sinus is a baroreceptor that primarily detects changes in blood pressure within the carotid artery, not the chemical composition of the blood. Option d is incorrect because while medullary chemoreceptors do monitor carbon dioxide levels centrally, the question specifically describes peripheral detection of oxygen and carbon dioxide partial pressures together.

Correct Answer: Epiglottic cartilage

Option d is correct because the epiglottic cartilage is the elastic, flexible cartilage in the larynx that forms the epiglottis, which folds over the tracheal opening during swallowing. Option a is incorrect because the thyroid cartilage is a large hyaline cartilage that forms the anterior wall of the larynx and is commonly known as the Adam's apple structure. Option b is incorrect because the cricoid cartilage is a ring-shaped hyaline cartilage located below the thyroid cartilage that provides structural support to the lower larynx, not flexibility. Option c is incorrect because the arytenoid cartilages are small paired cartilages that sit on top of the cricoid cartilage and help control vocal cord tension and movement.

Correct Answer: Nephron

Option a is correct because the nephron is the functional unit of the kidney responsible for filtering blood, reabsorbing nutrients and water, secreting wastes, and producing urine. Option b is incorrect because the collecting duct receives processed filtrate from multiple nephrons and fine-tunes water reabsorption but is not considered the complete functional filtering unit. Option c is incorrect because the renal pelvis is a funnel-shaped structure that collects urine from the nephrons and channels it into the ureter, not the filtering unit itself. Option d is incorrect because the glomerulus is only the capillary network within the nephron where initial filtration occurs, representing just one component rather than the entire functional unit.

Correct Answer: Proximal convoluted tubule

Option b is correct because the proximal convoluted tubule reabsorbs the majority of filtered nutrients from the filtrate, including glucose, amino acids, vitamins, and a large portion of water. Option a is incorrect because the distal convoluted tubule primarily fine-tunes the composition of urine by responding to hormones like aldosterone, rather than performing the initial bulk reabsorption. Option c is incorrect because the loop of Henle primarily focuses on creating a concentration gradient in the kidney medulla and reabsorbing bicarbonate ions rather than recovering nutrients. Option d is incorrect because the collecting duct receives processed filtrate from multiple nephrons and adjusts final water reabsorption under the influence of antidiuretic hormone, not nutrient recovery.

Correct Answer: Loop of Henle

Option d is correct because the loop of Henle establishes the osmotic concentration gradient in the renal medulla through the countercurrent multiplier system, which is essential for producing concentrated urine. Option a is incorrect because the proximal convoluted tubule reabsorbs the majority of nutrients and water through obligatory reabsorption but does not create the medullary concentration gradient itself. Option b is incorrect because the distal convoluted tubule adjusts sodium and potassium levels in response to aldosterone but does not establish the countercurrent multiplication gradient in the medulla. Option c is incorrect because the collecting duct responds to the gradient created by the loop of Henle and uses antidiuretic hormone to reabsorb water but does not generate the gradient.

Correct Answer: Antidiuretic hormone and aquaporins

Option b is correct because antidiuretic hormone released by the pituitary gland stimulates the insertion of aquaporin water channels into collecting duct membranes, increasing water reabsorption during dehydration. Option a is incorrect because aldosterone acts primarily on the distal convoluted tubule to increase sodium reabsorption through sodium channels, not water channels in the collecting ducts directly. Option c is incorrect because renin is an enzyme released by the kidneys that activates the angiotensin pathway and is not a hormone that directly inserts channel proteins into tubular membranes. Option d is incorrect because atrial natriuretic peptide is released by the heart to promote sodium and water excretion, working opposite to the water-conserving mechanism described in the scenario.

Correct Answer: Ureter

Option a is correct because the renal pelvis narrows and becomes the ureter, a muscular tube that uses peristaltic contractions to transport urine from each kidney downward to the bladder. Option b is incorrect because the collecting duct is a microscopic tubular structure within the kidney that receives filtrate from nephrons but does not transport urine to the bladder externally. Option c is incorrect because the urethra is the tube that carries urine from the bladder to the outside of the body during urination, not from the kidney to the bladder. Option d is incorrect because the renal artery carries oxygenated blood to the kidney for filtration and has no role in transporting urine from the renal pelvis to the bladder.

Correct Answer: Seminiferous tubules

Option c is correct because spermatogenesis occurs within the seminiferous tubules of the testes, where cells progress through developmental stages from spermatogonia at the outer edge to mature sperm. Option a is incorrect because the epididymis is the coiled tube located on the posterior surface of each testis where sperm are stored and undergo final maturation after leaving the tubules. Option b is incorrect because the ductus deferens is the muscular tube that transports mature sperm from the epididymis toward the urethra during ejaculation, not where sperm develop. Option d is incorrect because the prostate gland is an accessory reproductive gland that produces alkaline fluid contributing to semen volume but plays no role in the creation of sperm.

Correct Answer: LH binding to Leydig cells

Option d is correct because luteinizing hormone from the anterior pituitary binds to receptors on Leydig cells located between the seminiferous tubules in the testes, directly stimulating testosterone production. Option a is incorrect because FSH binds to Sertoli cells to support spermatogenesis and sperm development, but Sertoli cells do not produce testosterone in response to follicle-stimulating hormone. Option b is incorrect because inhibin is produced by the testes and travels to the anterior pituitary to inhibit FSH release through negative feedback, not to stimulate testosterone production. Option c is incorrect because GnRH is released by the hypothalamus and acts on the anterior pituitary to stimulate LH and FSH release, not directly on the testicular cells themselves.

Correct Answer: Acrosomal cap with lysosomal enzymes

Option a is correct because the acrosomal cap on the sperm head contains lysosomal enzymes that digest the outer protective layers of the egg, which is essential for successful fertilization. Option b is incorrect because the flagellar base provides the structural foundation for the sperm tail's whip-like movement used for swimming, not for enzymatic digestion of egg barriers. Option c is incorrect because the mitochondrial sheath is located in the midpiece of the sperm and provides energy for flagellar movement, not enzymes for penetrating the egg layers. Option d is incorrect because the nuclear envelope surrounds the genetic material within the sperm head but does not contain the specialized digestive enzymes needed for egg penetration.

Correct Answer: Inhibin

Option d is correct because inhibin is produced by the testes and sends negative feedback signals specifically to the anterior pituitary gland, inhibiting further release of follicle-stimulating hormone. Option a is incorrect because testosterone provides negative feedback primarily to the hypothalamus to reduce GnRH secretion and to the anterior pituitary for LH, not specifically FSH inhibition. Option b is incorrect because while small amounts of estrogen are present in males, estrogen is not the primary hormone responsible for directly inhibiting FSH release from the anterior pituitary. Option c is incorrect because luteinizing hormone is released by the anterior pituitary to stimulate the testes and is not a feedback hormone produced by the testes to inhibit pituitary function.

Correct Answer: Prostate gland

Option b is correct because the prostate gland surrounds the urethra just below the bladder, and when it enlarges it can constrict the urethra, causing difficulty urinating and weakened flow. Option a is incorrect because the seminal vesicles are located posterior to the bladder and produce fructose-rich fluid for semen but do not surround the urethra or cause urinary obstruction. Option c is incorrect because the bulbourethral glands are small pea-sized glands located below the prostate that secrete pre-ejaculatory fluid and do not typically cause urinary obstruction when enlarged. Option d is incorrect because the epididymis is located on the posterior surface of each testis within the scrotum and has no anatomical proximity to the urethra to cause urinary symptoms.

Correct Answer: Graafian follicle

Option a is correct because the Graafian follicle is the fully mature ovarian follicle that contains an oocyte which has completed meiosis one and is arrested in meiosis two before ovulation. Option b is incorrect because the corpus luteum forms after ovulation from the remnants of the ruptured follicle and secretes progesterone, rather than being the pre-ovulatory mature follicle. Option c is incorrect because a primordial follicle is the earliest dormant stage of follicular development containing a primary oocyte that has not yet begun any significant growth or maturation. Option d is incorrect because the corpus albicans is the final degraded remnant of the corpus luteum that forms a small scar on the ovary after progesterone production has ceased.

Correct Answer: Estrogen

Option b is correct because estrogen shows two peaks during the menstrual cycle, with the first driven by growing follicles in the follicular phase and the second produced by the corpus luteum in the luteal phase. Option a is incorrect because progesterone primarily rises during the luteal phase after ovulation when the corpus luteum is active and does not show a significant peak during the follicular phase. Option c is incorrect because luteinizing hormone displays one dramatic surge just before ovulation that triggers the release of the egg, rather than showing two separate peaks across the cycle. Option d is incorrect because follicle-stimulating hormone rises early in the follicular phase to stimulate follicle growth but does not display a characteristic second peak during the luteal phase.

Correct Answer: Progesterone

Option d is correct because progesterone produced by the corpus luteum during the luteal phase is the key hormone that maintains the thick stratum functionalis layer of the endometrium for implantation. Option a is incorrect because while estrogen helps build the endometrial lining during the follicular phase, progesterone is the primary hormone responsible for maintaining the stratum functionalis after ovulation. Option b is incorrect because follicle-stimulating hormone acts on the ovaries to stimulate follicle development and does not directly maintain or support the thickness of the uterine lining. Option c is incorrect because luteinizing hormone triggers ovulation and stimulates corpus luteum formation but does not directly act on the endometrium to maintain the stratum functionalis layer.

Correct Answer: Clitoris

Option b is correct because the clitoris arises from the same embryological cells as the glans penis during fetal development, making them homologous structures in male and female anatomy. Option a is incorrect because the labia majora are the embryological homologue of the scrotum rather than the glans penis, as both develop from the same fetal tissue called labioscrotal swellings. Option c is incorrect because the vaginal opening is a distinct female anatomical structure that does not share a direct embryological developmental origin with the glans penis in males. Option d is incorrect because the labia minora, while they do encircle the clitoris superiorly and anteriorly, are not themselves the embryological homologue of the glans penis structure.

Correct Answer: Stratum functionalis shed due to progesterone decline

Option a is correct because when the corpus luteum degenerates and progesterone levels decline, the stratum functionalis layer of the endometrium loses its hormonal support and is shed during menstruation. Option b is incorrect because the myometrium is the thick muscular wall of the uterus responsible for contractions during labor and is not a lining layer that is shed during the menstrual cycle. Option c is incorrect because the stratum basalis is the deep permanent layer of the endometrium that is not shed during menstruation and serves as the regenerative base for the functionalis layer. Option d is incorrect because the perimetrium is the outermost serous membrane covering the uterus and is a structural layer that is never shed during the monthly menstrual cycle process.