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Biology 250 Exam 3 2025 Entry Latest
Edition with A+ Graded Answers.
What is a liver lobule? - Correct Ans: ✔✔Liver lobules are composed of repeating hexagons of heptocytes and contain blood vessels and bile ducts. They allow for efficient filtering and removal of nutrients from blood coming from the digestive organs via the hepatic portal system.
What is the portal triad? - Correct Ans: ✔✔The portal triad is located at each corner of a liver lobule and is composed of a vein, an artery, and a bile duct.
What are the functions of the pancreas? - Correct Ans: ✔✔Exocrine function - produce digestive enzymes (pancreatic juice)
Endocrine function - produce insulin and glucagon to maintain blood sugar levels
How can the pancreas be both an endocrine and exocrine organ? -
Correct Ans: ✔✔It has acinar cells that fulfill the exocrine function and produce digestive enzymes and it has other cells that fulfill the endocrine function and make hormones, insulin, and glucagon.
What do acinar cells produce? - Correct Ans: ✔✔Digestive enzymes (pancreatic juice)
What is the difference between a cloaca and an anus? - Correct Ans:
✔✔A cloaca is a single opening with different compartments used to drain the kidneys, rectum, and reproductive system. An anus is a single opening used only to drain the rectum with different exits used to drain the urogenital system.
Is energy required to move oxygen and carbon dioxide across
membranes? - Correct Ans: ✔✔No, it is done via passive diffusion from high partial pressure to low partial pressure.
How do internal and external respiration differ? - Correct Ans:
✔✔Internal: gas exchange between the blood and the tissues
External: gas exchange between the environment and the blood
What processes constitute respiration? - Correct Ans: ✔✔Delivery of oxygen to tissues and removal of waste products; can be external (environment and blood) or internal (blood and tissues)
What processes constitute ventilation? - Correct Ans: ✔✔Breathing; the active process of moving respiratory medium (water or air) across an exchange surface (inspiration and expiration)
What is perfusion? - Correct Ans: ✔✔The pumping of blood through an organ via capillaries.
What surfaces can act as respiratory membranes in vertebrates? -
Correct Ans: ✔✔Skin, lungs, external gills, and internal gills
expand pharyngeal chamber, creating a vacuum that sucks water in; stops when pharynx is filled with water.
Expiration: the mouth closes and the levator and hypobranchial muscles expand the gill chambers causing them to fill with water which is then forced out of the gill chambers via external gill slits.
Describe the structure of the gills in bony fish. - Correct Ans:
✔✔Operculum is located caudally on the hyoid arch; operculum chamber unites with the branchiostegal membrane rays beneath the gills with interbranchial septa; the demibranch is unattached distally for water flow
Describe the process by which bony fish ventilate their gills. - Correct
Ans: ✔✔Inspiration: the pharyngeal floor is lowered, the mouth opens, and the operculum closes; branchiostegal membrane unfolds and expands operculum chamber to draw water over the gills into the chamber.
Expiration: the mouth closes, the pharyngeal floor is elevated which compresses the operculum chamber, forcing water out of the opercular cleft.
What is a major anatomical difference in how sharks vs bony fish
ventilate their gills? - Correct Ans: ✔✔Sharks use the dual pump system that creates alternating negative/positive pressures, use spiracle to suck in water, and branchiomeric, levator and hypobranchial muscles to inspire/expire
Bony fish use pharyngeal floor and mouth to compress the operculum chamber to inspire/expire
What is a swim bladder? What taxa have this structure? - Correct
Ans: ✔✔An air sac similar to a lung; almost all fish have a swim bladder
What is the function of the swim bladder? - Correct Ans:
✔✔Buoyancy in the water, some fish use for sound detection and vocalization
What are the two types of swim bladders and how do they differ
anatomically? - Correct Ans: ✔✔Phyostomous: connected to the digestive tract by the pneumatic duct (primitive)
Physoclistous: closed bag that is not connected to the digestive tract
What are the external nares used for in fish? - Correct Ans: ✔✔Used to monitor chemicals in the water
Describe how the nares function in fish. - Correct Ans: ✔✔While the fish is swimming, water flows into the forward directed incurrent aperture and exits through either a lateral or ventral directed excurrent aperture. Between the two apertures, the water flows over the olfactory epithelium.
Describe the structure of amphibian lungs. - Correct Ans: ✔✔Simple sacs that take the shape of the pleuroperitoneal cavity; better developed anteriorly; septal surface with subdivision to increase
instead a system of muscles located within the shell contract and relax to bring air in and out of lungs. This results in compression of the visceral organs.
Using humans as the example, describe ventilation in mammalian
lungs. - Correct Ans: ✔✔Aspiration pump
Inhalation: external intercostal muscles contract to rotate adjacent ribs and medial sternum forward, expanding the space around the lungs so that the lungs can expand and draw in air
Exhalation: internal intercostals pull the ribs back, the diaphragm recoils, and chest volume decreases, forcing air out of the lungs
What structures make up the conducting zone in the human
respiratory system? - Correct Ans: ✔✔Nostrils, pharynx, larynx, trachea, bronchi, bronchioles
What structures make up the respiratory zone in the human
respiratory system? - Correct Ans: ✔✔Alveolar ducts, alveoli
List, in order, the respiratory structures a breath of air will pass through as it travels through the human respiratory system. -
Correct Ans: ✔✔Nostrils, nasopharynx, oropharynx, laryngopharynx, larynx, trachea, primary bronchi to lungs, secondary bronchi to lungs, tertiary bronchi, bronchioles, alveolar ducts, alveoli
What are the 3 regions of the human pharynx? - Correct Ans:
✔✔Nasopharynx, oropharynx, laryngopharynx
Where are the vocal cords located? - Correct Ans: ✔✔Larynx
What structure keeps ingested food from entering the trachea? -
Correct Ans: ✔✔Epiglottis
What structure opens to allow air to flow over the vocal cords? -
Correct Ans: ✔✔Glottis
Correctly label the structures indicated on the following diagram: -
Correct Ans: ✔✔Larynx, Trachea, Primary bronchi, Seconday bronchi, Tertiary bronchi, Bronchiole
What are 2 major anatomical differences between the right and left
human lung? - Correct Ans: ✔✔Right: 3 lobes
Left: 2 lobes with notch for the heart
Where would you find the parietal pleura? - Correct Ans: ✔✔The lining of the pleural cavity
Where would you find the visceral pleura? - Correct Ans: ✔✔The lining outside of the lungs
What is the function of the pleural cavity? - Correct Ans: ✔✔It contains fluid to reduce friction and keep the pressure difference to keep the lungs inflated.
- Exhalation 2 - spent air is pushed out of the lungs and exits with air from anterior sacs
Differences: Gas exchange occurs in capillaries; work at higher altitudes than mammalian lungs; more efficient, 1 draft of air in and back out with 2 cycles of inhalation/exhalation; no residual volume left in body as seen in mammals
What is the function of the pneumatic foramen in bird bones? -
Correct Ans: ✔✔Allows diverticula of the air sacs to penetrate the bones.
Discuss the importance of maintaining the appropriate
ventilation/perfusion ratio. - Correct Ans: ✔✔The rate of ventilation must match with the rate of perfusion because:
If perfusion is too rapid, blood won't be fully saturated with oxygen
If perfusion is too slow, blood becomes saturated and can't take up any more oxygen and oxygenated air is exhaled.
Besides amphibians, do any other taxa utilize cutaneous respiration?
- Correct Ans: ✔✔Bats and turtles
Discuss the evolution of air breathing. Make sure to include in your answer any intermediate adaptations and anatomical changes that needed to occur. Also discuss relevant hypotheses for why evolution would have favored the full transition to land. (ESSAY QUESTION) -
Correct Ans: ✔✔Lungs developed (lungfish) before moving to land. (hypoxia, preadaptation)
Evolution occurred many times within the bony fish line and included different organs like: swim bladder, digestive tract, gill chamber compartments, and true lungs.
Carp-like fish can gulp air into their intestine where extra capillaries take up oxygen → certain freshwater eels can gulp ai bubbles and hold against gills → lungfish with preadaptation to well-developed lungs to breath air → electric eels hold air and take up oxygen thru mouth
The transition into freshwater and land led to (interchangeably) the favor for a developed lungs and a redesign of the respiratory system to avoid hypoxia and find food/avoid predators.
Water: dual pump (most fishes) → buccal pump (air-breathing fishes) →
Water/Land: specialized/modified buccal pump (Lissamphibia) →
Land: aspiration pump (reptiles) → specialized aspiration pump (mammals)
What structures make up the cardiovascular system? - Correct Ans:
✔✔Blood, blood vessels, the heart, and the lymphatic system
Besides transport of gases between the sites of internal/external respiration, what are some other functions of the cardiovascular
system? - Correct Ans: ✔✔Transports excess heat to the skin or absorbs heat and carries it to deeper tissues, carries glucose and other end products of digestion, delivers hormones, brings waste to kidneys, transports immune cells and chemicals
lymphocytes*)? - Correct Ans: ✔✔Erythrocytes - arise from myeloid stem cells
Platelets - arise from myeloid stem cells
Granulocytes - arise from myeloid stem cells
Lymphocytes - arise from lymphoid stem cells
What type of blood vessel carries blood away from the heart? -
Correct Ans: ✔✔Arteries
What type of blood vessel carries blood toward the heart? - Correct
Ans: ✔✔Veins
Compare and contrast the tunic layers that make up blood vessels. -
Correct Ans: ✔✔The innermost layer is called the tunica interna and it is composed of an endothelial layer that lines the lumen of the vessel. The middle layer is called the tunica media and it is composed of smooth muscle and elastin. It is usually the thickest layer, and it is thicker in arteries than veins. It allows the vessel to regulate blood flow and blood pressure. The outermost layer is called the tunica externa and it is composed of areolar and dense, irregular connect tissue. It protects the vessel from getting damaged. It is thicker in veins than arteries.
What is the difference between systolic and diastolic blood pressure?
- Correct Ans: ✔✔Systolic blood pressure - the peak pressure in the arteries after ventricle contraction
Diastolic blood pressure - the lowest pressure in the arteries in between heartbeats
What is the microcirculation? - Correct Ans: ✔✔The circulation of blood by different smooth muscles, shunts, and precapillary sphincters from the heart to arterioles, to capillaries, to venules, and then back to the heart. Precapillary sphincters and shunts restrict and divert blood flow to different areas or capillary beds. It functions in thermoregulation and directs blood to active organs.
What mechanisms does the microcirculation use to direct and
regulate organ perfusion? - Correct Ans: ✔✔Precapillary sphincters are used to restrict blood flow to certain capillary beds. Shunts are used to divert blood flow around capillary beds and can sometimes be used to bypass entire regions.
What are the consequences if the microcirculation does not function
properly? - Correct Ans: ✔✔Inadequate blood supply, also known as Ischemia.
Massive drop in blood pressure, usually seen during hypotensive shock where the microcirculation fails completely.
Describe the differences between double and single circulation and
give an example taxa for each. - Correct Ans: ✔✔Single circulation - the blood pumped from the heart travels through the lungs, through the body, and then back to the heart. Results in a single circulation. Ex: fishes
Double circulation - the blood pumped from the heart travels through the lungs, and then back to the heart, and then travels through the body. Results in a total of two circulations. Ex: amphibians and amniotes
Discuss the evolutionary modifications in the aortic arches of amphibians. Be specific about how they differ from the aortic arches of fish, and note at least one difference between larva with external
gills and adults. - Correct Ans: ✔✔Contrary to fish, in amphibians, the first and second arches disappear completely. The ventral aorta between arch 3 and 4 becomes the common carotid artery. Larval amphibians respirate through external gill slits. Arches 3-5 go to the external gills and arch 6 sprouts the pulmonary artery. Adult amphibians lose the gills but but the arches are still retained as systemic vessels. During metamorphosis, the carotid duct closes. Frogs also have a pulmocutaneous artery to aid in cutaneous respiration.
What is the function of the carotid duct found in the aortic arches of
amphibians? - Correct Ans: ✔✔Closes arches 3 & 4 during metamorphosis
Compare and contrast the aortic arches of either reptiles, birds, or mammals (choose 1) with bony fish. Explain the major changes that occurred with the full transition to terrestrial life, and note at least 2
specific structures that differ. - Correct Ans: ✔✔Reptiles - arches become asymmetrical; Arches III, IV, VI persist; most changes in Arch IV with a right and left systemic arch following the pulmonary trunk that exits the right ventricle
Bony fish - arch I disappears and II is no longer associated with gills but other than that they are all efferent/afferent arteries with collecting loops amongst the gills
In reptiles, the ventral aorta splits into what 3 arteries that leave the
heart? - Correct Ans: ✔✔Left systemic arch, right systemic arch, and pulmonary trunk
What are the 3 general function systems of vertebrate venous
circulation? - Correct Ans: ✔✔Systemic, hepatic portal system, and pulmonary
What is the function of the sinus venosus in fish? - Correct Ans:
✔✔To collect blood from systemic circulation, mainly from the anterior cardinal veins and the inferior jugular veins.
In all vertebrate taxa except mammals, the kidneys are drained by
what system? - Correct Ans: ✔✔Renal portal system
The posterior cardinal veins seen in amphibians become what in
reptiles? - Correct Ans: ✔✔Azygos veins
In mammals, the posterior vena cava is subdivided into what major
veins? - Correct Ans: ✔✔Hepatic, renal, and subcardinal veins
Be able to label the major veins/arteries of the general vertebrate
circulation plan in the figure provided. - Correct Ans: ✔✔See figure
What is the name for the sac of dense connective tissue that
encircles the heart? - Correct Ans: ✔✔Fibrous pericardium
true chambers: the ventricle and the atrium, and the sinus and conus arteriosus.
Amphibians - heart has 5 parts with 3 true chambers: the ventricle and 2 atria, and they also have the sinus venosus, which is much smaller compared to the one in fish, and the conus arteriosus.
What structure in amphibian hearts allows them to direct blood
either to the pulmonary or systemic circulation? - Correct Ans:
✔✔The spiral valve of the conus arteriosus
What is unique about the crocodilian heart? How does its anatomy
differ from other reptiles? - Correct Ans: ✔✔The crocodilian heart has 4 true chambers including 2 ventricles and 2 atria. Other reptiles other have 1 ventricle and 2 atria, meaning they have 3 chambered hearts. Crocodilians also have a Foramen of Panizza, which connects the left and right aortic arches and allows blood to bypass the pulmonary circulation when the animal is diving.
Correctly label these structures on the human heart in the figure
provided. - Correct Ans: ✔✔See figure on slide 28
What is the function of the atrioventricular valves? - Correct Ans:
✔✔To separate the atria and ventricles and prevent the back flow of blood.
What is the function of the semilunar valves? - Correct Ans: ✔✔To separate the ventricles from the major vessels that exit them and prevent the back flow of blood.
Trace the flow of blood through the human circulation beginning with the superior and inferior vena cava dumping deoxygenated blood into the heart. List ALL specific chambers of the heart and valves that the blood will flow through, in order, and the major arteries/veins that enter/leave the heart (NOTE: if this question appears as the essay, it will be combined with the one below asking you to describe the intrinsic conduction system) (ESSAY QUESTION) -
Correct Ans: ✔✔The superior vena cava and the inferior vena cava dump deoxygenated blood into the right atrium. The blood then flows through the tricuspid valve into the right ventricle. The heart contracts and the blood moves from the right ventricle through the pulmonary semilunar valve, up the pulmonary trunk, and into the pulmonary arteries to the lungs where gas exchange occurs and the blood becomes oxygenated. The blood then flows back down through the pulmonary veins into the left atria where it then flows through the mitral (bicuspid) valve into the left ventricle. The blood then passes through the aortic semilunar valve into the aorta where it then gets pumped through the rest of the body.
How does the intrinsic conduction system function to generate regular heart beats? (Make sure to name all relevant structures) -
Correct Ans: ✔✔The sinoatrial node, which is located below the superior vena cava in the right atrium, generates the first electrical impulse to generate a contraction. In a normal heart, this happens about every 0.8 seconds. This impulse spreads throughout the right and left atria, and is further carried by the atrioventricular node, which delays the impulse by 0.1 seconds to allow the atria to fully contract before the impulse is carried to the ventricle. The impulse then travels down the interventricular septum through the Bundle of His until it gets to the left and right bundle branches, which go down
