Cardiovascular System: Blood Vessels and Circulation

Practice Q&A flashcards based on OpenStax Anatomy and Physiology Chapter 20: Blood Vessels and Circulation.

What three tunics make up the walls of most blood vessels, and what are their primary components?

1. Tunica Intima: Epithelial and connective tissue, containing endothelium and an internal elastic membrane.
2. Tunica Media: Middle layer made of smooth muscle.
3. Tunica Externa: Connective tissue layer that helps hold the vessel in position.

How do arteries and veins differ regarding wall thickness, general appearance, pressure, and the presence of valves?

Arteries have thicker walls, a rounded general appearance, higher blood pressure, and no valves. Veins have thinner walls, an irregular or collapsed appearance, lower pressure, and contain valves (most commonly in limbs and inferior to the heart).

How do elastic arteries, muscular arteries, and arterioles differ in structure, location, and function?

Elastic arteries are located close to the heart, containing elastic fibers to handle high pressure. Muscular arteries have a thick tunica media responsible for vasoconstriction. Arterioles are tiny vessels leading to capillaries that regulate blood pressure.

Based on the image provided, name the three types of capillaries and state where sinusoid capillaries are typically found in the body.

1. Continuous capillary
2. Fenestrated capillary
3. Sinusoid capillary

Sinusoid capillaries are found in the liver, spleen, and lymph nodes.

Based on the diagram, what vessel feeds directly into a capillary bed and can act as a vascular shunt when precapillary sphincters are closed?

Metarteriole

What type of blood vessel measures $8\text{--}100\text{ microns}$ in diameter, joins multiple capillaries, and serves as the primary site of emigration or diapedesis?

Venules

Why are systemic veins referred to as blood reservoirs, and what percentage of blood volume do they hold?

Systemic veins hold $64\%$ of the body's blood volume due to their high capacitance, allowing the cardiovascular center in the medulla oblongata to redistribute blood via venoconstriction when needed.

What is the formula for calculating Mean Arterial Pressure (MAP)?

$\text{MAP} = \text{Diastolic BP} + \left(\frac{\text{Pulse Pressure}}{3}\right)$, where Pulse Pressure (PP) is $\text{Systolic BP} - \text{Diastolic BP}$.

What are Korotkoff sounds and what instrument is used to clinically measure blood pressure?

Korotkoff sounds are produced by turbulent blood flow as a cuff deflates (the first sound recorded is systolic BP and the last is diastolic BP). A sphygmomanometer is used in clinical measurement along with a stethoscope.

What five main variables directly affect arterial blood flow and blood pressure?

1. Cardiac output
2. Compliance
3. Blood volume
4. Blood viscosity
5. Blood vessel length and diameter

How do the skeletal muscle pump and respiratory pump assist venous return to the heart?

The skeletal muscle pump increases pressure on veins during muscle contraction (e.g., walking/running) to push blood toward the heart. The respiratory pump uses inhalation to cause blood to flow slowly into the thoracic cavity and exhalation to speed up blood flow into the heart.

What two primary pressures govern bulk flow across capillary walls during capillary exchange?

Hydrostatic pressure (composed of blood/capillary hydrostatic pressure and interstitial fluid hydrostatic pressure) and Osmotic pressure (composed of blood colloidal osmotic pressure and interstitial fluid colloidal osmotic pressure).

What structures in the brain and peripheral vessels control neural regulation of vascular homeostasis?

The cardiovascular center in the brain, baroreceptor reflexes in the aortic and carotid sinuses (sensing pressure), and chemoreceptor reflexes (sensing oxygen, carbon dioxide, and pH).

How do Antidiuretic Hormone (ADH) and Atrial Natriuretic Hormone (ANH) differ in their regulation of blood volume and blood pressure?

Antidiuretic hormone (ADH/vasopressin) causes fluid retention in the kidneys and acts as a vasoconstrictor to restore and increase blood volume and pressure. Atrial natriuretic hormone (ANH), secreted by atrial cells in the heart, promotes sodium and water loss, thereby reducing blood volume and pressure.

What is the function of Erythropoietin (EPO) in regulating blood homeostasis?

Erythropoietin (EPO) stimulates red blood cell (RBC) production, acts as a vasoconstrictor, and increases blood pressure.

How does cardiac output increase during maximal exercise in a trained athlete compared to a healthy young non-athlete?

In a healthy young adult, cardiac output increases from $5.0\,\text{L/min}$ at rest to $20\,\text{L/min}$ during maximal exercise. In a trained athlete, cardiac output increases from $5.3\,\text{L/min}$ at rest to $30\,\text{L/min}$ during maximal exercise.

What are the four clinical types of circulatory shock described in the lecture notes?

1. Hypovolemic shock: Caused by hemorrhage or fluid loss.
2. Cardiogenic shock: Results from an inability of the heart to maintain cardiac output (e.g., following myocardial infarction).
3. Vascular shock: Occurs when arterioles lose muscular tone.
4. Obstructive shock: Occurs when a portion of the vascular system is physically blocked.

What three major arterial branches originate directly from the aortic arch?

1. Brachiocephalic artery
2. Left common carotid artery
3. Left subclavian artery

What is the Arterial Circle (Circle of Willis) and which vessels form it?

The Circle of Willis is an arterial anastomosis located at the base of the brain that ensures continuous blood supply to the brain. It is formed from branches of the internal carotid and vertebral arteries.

What is the function of the Hepatic Portal System?

It absorbs nutrients and water from the digestive system and delivers them (except most lipids) directly to the liver for processing via the hepatic portal vein.

From which embryonic germ layer do blood vessels develop, and what are the key precursor cells involved?

Blood vessels originate from embryonic mesoderm, beginning with hemangioblasts and angioblasts, which form blood islands that develop into vascular tubes.

Based on the diagram of fetal circulation, identify the three temporary vascular shunts and describe their connections.

1. Foramen ovale: Located in the interatrial septum; shunts blood from the right atrium directly to the left atrium.
2. Ductus arteriosus: Connects the pulmonary trunk to the aorta, allowing most blood to bypass the non-functional fetal lungs.
3. Ductus venosus: Branches from the umbilical vein, carrying oxygenated blood straight to the fetal heart.