Which layer of a blood vessel wall consists mainly of smooth muscle and elastic fibers?
Tunica media
✓
Tunica intima
Tunica externa
Endothelium
Correct Answer
Tunica media
The tunica media is the middle layer, made of smooth muscle and elastic fibers that let the vessel constrict, dilate and recoil. The tunica intima is the innermost layer of endothelium and supporting tissue. The tunica externa is the outer layer, made mostly of collagen. Endothelium is the simple squamous lining of the tunica intima, not a muscular layer.
Category: Vessel Structure
Question 2
Which vessels provide the greatest resistance to blood flow and act as the main site of blood pressure regulation?
Capillaries
Arterioles
✓
Venules
Elastic arteries
Correct Answer
Arterioles
Arterioles have smooth muscle that changes their small radius, so they produce the greatest resistance and the steepest drop in pressure. This makes them the main resistance vessels. Capillaries have no smooth muscle in their walls and are built for exchange. Venules are low-pressure collecting vessels. Elastic arteries are wide conducting vessels that offer little resistance.
Category: Vessel Structure
Question 3
Which type of capillary has large gaps that let large molecules and even blood cells pass, and is found in the liver and bone marrow?
Continuous capillary
Fenestrated capillary
Sinusoid capillary
✓
Lymphatic capillary
Correct Answer
Sinusoid capillary
Sinusoid capillaries have wide gaps between endothelial cells and an incomplete basement membrane, so large molecules and cells can cross. They occur in the liver, spleen, bone marrow and lymph nodes. A continuous capillary is the most common type and has tight junctions. A fenestrated capillary has small pores but does not pass cells. A lymphatic capillary carries lymph, not blood.
Category: Vessel Structure
Question 4
In which vessels is blood velocity lowest, because their combined cross-sectional area is the largest in the circulation?
Aorta
Large veins
Arterioles
Capillaries
✓
Correct Answer
Capillaries
Capillaries have the greatest total cross-sectional area of any vessel type, so blood moves through them most slowly. The slow flow gives time for exchange with the tissues. The aorta has a small total cross-sectional area and the fastest flow. Large veins speed blood up again on its way back to the heart. Arterioles have more total area than arteries but far less than capillaries.
Category: Blood Pressure and Flow
Question 5
A patient's blood pressure is 120/80 mm Hg. What is the pulse pressure?
40 mm Hg
✓
80 mm Hg
93 mm Hg
200 mm Hg
Correct Answer
40 mm Hg
Pulse pressure is systolic pressure minus diastolic pressure, so 120 minus 80 gives 40 mm Hg. 80 mm Hg is the diastolic value itself. 93 mm Hg is approximately the mean arterial pressure for this reading. 200 mm Hg is the sum of the two values, which has no physiological meaning.
Category: Blood Pressure and Flow
Question 6
Using the standard estimate, what is the mean arterial pressure of someone whose reading is systolic 120 and diastolic 90 mm Hg?
90 mm Hg
100 mm Hg
✓
105 mm Hg
110 mm Hg
Correct Answer
100 mm Hg
Mean arterial pressure is estimated as diastolic pressure plus one third of the pulse pressure. Here the pulse pressure is 30, so 90 plus 10 gives 100 mm Hg. 90 mm Hg is only the diastolic value. 105 mm Hg is the simple average of the two numbers, which overweights systole because the heart spends longer in diastole. 110 mm Hg is too close to the systolic value.
Category: Blood Pressure and Flow
Question 7
If the radius of a blood vessel is cut in half while everything else stays the same, by about how much does its resistance to flow increase?
2 times
4 times
16 times
✓
8 times
Correct Answer
16 times
Resistance is inversely proportional to the radius raised to the fourth power. Halving the radius gives (1/2) to the fourth power, or 1/16, so resistance rises 16 times. 2 times would mean resistance varied directly with radius. 4 times would fit the square of the radius. 8 times would fit the cube of the radius.
Category: Blood Pressure and Flow
Question 8
Which mechanism aids venous return when inhalation lowers pressure in the thoracic cavity and draws blood toward the heart?
Skeletal muscle pump
Venous reserve
Myogenic response
Respiratory pump
✓
Correct Answer
Respiratory pump
The respiratory pump works because inhalation lowers thoracic pressure, so blood moves from the higher-pressure abdominal veins into the thoracic veins and on to the heart. The skeletal muscle pump relies on contracting limb muscles squeezing veins with valves. Venous reserve is blood stored in venous networks of organs like the liver and skin. The myogenic response is arteriole smooth muscle reacting to stretch.
Category: Blood Pressure and Flow
Question 9
Which force is mainly responsible for pushing fluid out of a capillary at its arterial end?
Capillary hydrostatic pressure
✓
Blood colloidal osmotic pressure
Active sodium transport
Lymphatic drainage
Correct Answer
Capillary hydrostatic pressure
Capillary hydrostatic pressure is the pressure of blood against the capillary wall, and at the arterial end it exceeds the inward pull, so fluid is filtered out. Blood colloidal osmotic pressure pulls water into the capillary rather than out. Active sodium transport does not drive bulk fluid movement across capillary walls. Lymphatic drainage removes excess interstitial fluid but does not push fluid out of blood capillaries.
Category: Capillary Exchange
Question 10
The blood colloidal osmotic pressure that draws water back into the blood from the tissues is created mainly by which substance?
Sodium ions
Plasma proteins
✓
Glucose
Red blood cells
Correct Answer
Plasma proteins
Plasma proteins are too large to cross most capillary walls, so they stay in the blood and create an osmotic pull that draws water inward. Sodium ions cross capillary walls freely, so their concentration is similar on both sides. Glucose also crosses readily and does not create a lasting gradient. Red blood cells are cells, not dissolved solutes, and do not generate colloidal osmotic pressure.
Category: Capillary Exchange
Question 11
Excess filtered fluid that is not reabsorbed into the blood returns to the circulation through which body system?
Digestive system
Urinary system
Lymphatic system
✓
Integumentary system
Correct Answer
Lymphatic system
Capillaries filter slightly more fluid than they reabsorb, and the lymphatic system collects the excess as lymph and returns it to the blood at the subclavian veins. Without it, fluid would build up in the tissues. The digestive system absorbs nutrients from the gut. The urinary system removes fluid as urine rather than returning it. The integumentary system is the skin and its structures.
Category: Capillary Exchange
Question 12
Where are the cardiovascular centers that control heart rate and blood vessel tone located?
Hypothalamus
Cerebellum
Pons
Medulla oblongata
✓
Correct Answer
Medulla oblongata
The cardiovascular centers, including the cardioaccelerator, cardioinhibitory and vasomotor centers, sit in the medulla oblongata of the brainstem. The hypothalamus influences these centers but does not house them. The cerebellum coordinates movement. The pons helps regulate breathing but is not the site of the cardiovascular centers.
Category: Vascular Regulation
Question 13
Baroreceptors in the carotid sinuses and aortic sinus respond directly to which stimulus?
Stretch of the vessel wall
✓
Blood oxygen level
Blood glucose level
Body temperature
Correct Answer
Stretch of the vessel wall
Baroreceptors are stretch receptors, so rising blood pressure stretches the vessel wall and increases their firing. The brain then slows the heart and dilates vessels to bring pressure down. Blood oxygen level is sensed by chemoreceptors. Blood glucose level is monitored by the pancreas. Body temperature is sensed by thermoreceptors and the hypothalamus.
Category: Vascular Regulation
Question 14
Which hormone, released from the posterior pituitary, increases water reabsorption by the kidneys and constricts peripheral vessels?
Aldosterone
Antidiuretic hormone
✓
Atrial natriuretic hormone
Erythropoietin
Correct Answer
Antidiuretic hormone
Antidiuretic hormone, also called vasopressin, is released from the posterior pituitary when blood volume or pressure falls, and it raises blood pressure by conserving water and constricting vessels. Aldosterone comes from the adrenal cortex and promotes sodium retention. Atrial natriuretic hormone lowers blood volume by promoting sodium and water loss. Erythropoietin from the kidneys stimulates red blood cell production.
Category: Vascular Regulation
Question 15
Which hormone is released by cardiac muscle cells of the upper heart chambers when blood volume is high, and promotes loss of sodium and water in the urine?
Renin
Angiotensin II
Atrial natriuretic hormone
✓
Aldosterone
Correct Answer
Atrial natriuretic hormone
Atrial natriuretic hormone is secreted when the atrial walls are stretched by high blood volume, and it lowers volume and pressure by increasing sodium and water excretion. It opposes the renin-angiotensin-aldosterone system. Renin is an enzyme from the kidneys that starts angiotensin II production. Angiotensin II constricts vessels and raises pressure. Aldosterone causes sodium and water retention.
Category: Vascular Regulation
Question 16
Circulatory shock caused by severe hemorrhage or extensive burns that reduce blood volume is classified as which type?
Cardiogenic shock
Obstructive shock
Neurogenic shock
Hypovolemic shock
✓
Correct Answer
Hypovolemic shock
Hypovolemic shock results from loss of blood or other body fluid, so too little volume is available to maintain pressure and tissue perfusion. Cardiogenic shock occurs when the heart itself fails as a pump, often after a heart attack. Obstructive shock comes from a blockage of flow, such as a pulmonary embolism. Neurogenic shock is a form of vascular shock caused by loss of vessel tone.
Category: Vascular Regulation
Question 17
Which vessel is the first branch of the aortic arch and divides into the right subclavian and right common carotid arteries?
Brachiocephalic trunk
✓
Celiac trunk
Left common carotid artery
Thyrocervical trunk
Correct Answer
Brachiocephalic trunk
The brachiocephalic trunk is the first and largest branch of the aortic arch, and it splits into the right subclavian and right common carotid arteries. The celiac trunk arises from the abdominal aorta and supplies the stomach, liver and spleen. The left common carotid artery is the second branch of the arch and does not divide into subclavian vessels. The thyrocervical trunk is a branch of the subclavian artery.
Category: Circulatory Pathways
Question 18
Which vein is formed by the union of the superior mesenteric vein and the splenic vein, and carries nutrient-rich blood to the liver?
Inferior vena cava
Hepatic portal vein
✓
Hepatic vein
Renal vein
Correct Answer
Hepatic portal vein
The hepatic portal vein carries blood from the digestive organs and spleen to the liver, where nutrients are processed and toxins removed before the blood reaches the general circulation. The inferior vena cava returns blood from the lower body to the right atrium. A hepatic vein drains blood out of the liver into the inferior vena cava. A renal vein drains a kidney.
Category: Circulatory Pathways
Question 19
The two vertebral arteries join at the base of the brain to form which artery?
Internal carotid artery
Middle cerebral artery
Basilar artery
✓
Posterior communicating artery
Correct Answer
Basilar artery
The left and right vertebral arteries travel up through the cervical vertebrae, enter the skull and unite to form the basilar artery, which supplies the brainstem and cerebellum. The internal carotid artery arises from the common carotid artery in the neck. The middle cerebral artery is a branch of the internal carotid artery. The posterior communicating artery links the internal carotid and posterior cerebral arteries.
Category: Circulatory Pathways
Question 20
Which fetal shunt connects the pulmonary trunk to the aorta, diverting most blood away from the nonfunctional lungs?
Foramen ovale
Ductus venosus
Umbilical vein
Ductus arteriosus
✓
Correct Answer
Ductus arteriosus
The ductus arteriosus is a short vessel between the pulmonary trunk and the aorta that sends most blood leaving the right ventricle into the systemic circulation. After birth it closes and becomes the ligamentum arteriosum. The foramen ovale is an opening between the right and left atria. The ductus venosus lets blood bypass the liver. The umbilical vein carries oxygen-rich blood from the placenta to the fetus.
Category: Vessel Development and Fetal Circulation