Week 7: Central and Peripheral Perfusion Flashcards
Which has thicker walls: Arteries or Veins?
Arteries
What sort of living cells are arteries and veins made up of?
Collagenous and elastic fibres, as well as other living cells.
What is the Vasa Vasorum?
Smaller blood vessels within the walls of larger veins and arteries
What are Nervi Vasorum?
Minute nerves within the walls of veins and arteries that control contraction and dilation of smooth muscle.
What are the 3 layers of tissues that arteries and veins are made up of?
Tunica intima
Tunica media
Tunica externa
What is the general appearance of Arteries?
Thick walls with small lumens, generally appear rounded
What is the general appearance of Veins?
Thin walls with large lumens, generally appear flattened
What are 2 types of arteries?
Elastic and Muscular arteries
What are Elastic Arteries?
Close to the heart, these arteries have thick walls with a high percentage of elastic fibers, allowing them to withstand high pressure and maintain the pressure gradient through elastic recoil. They have diameters larger than 10 mm.
What are Muscular Arteries?
Found farther from the heart, these arteries have more smooth muscle in the tunica media and fewer elastic fibers, enabling vasoconstriction but limiting elasticity. Their diameters range from 0.1 mm to 10 mm.
What is a gradual transition between arteries?
There is no clear division between elastic and muscular arteries; instead, a gradual transition occurs as arteries branch and lead to smaller arterioles.
What is the role of Elastic Arteries VS the role of Muscular Arteries?
Elastic arteries conduct large volumes of blood to smaller branches, while muscular arteries distribute blood to arterioles for precise regulation of blood flow.
What are Capillaries?
Capillaries are microscopic channels that supply blood to the tissues, in a process called perfusion; The wall of a capillary consists of the endothelial layer surrounded by a basement membrane with occasional smooth muscle
For capillaries to function, their walls must be leaky, allowing substances to pass through.
What are the 3 major types of Capillaries (based on leakiness)?
Continuous, Fenestrated, Sinusoid
What are Continuous Capillaries?
- The most common type of capillary, found in almost all vascularized tissues.
- Have complete endothelial lining with tight junctions
- Although a tight junction is usually impermeable and only allows for the passage of w
- In the brain, continuous capillaries are part of the blood-brain barrier.
What are Fenestrated Capillaries?
- Has pores (or fenestrations) and tight junctions in the endothelial lining.
- The number of fenestrations and their degree of permeability vary by location.
What are Sinusoid Capillaries?
- Least common type of capillary; found in the liver and spleen, bone marrow, lymph nodes (where they carry lymp).
- Flattened, have extensive intercellular gaps and incomplete basement membranes, and intercellular clefts and fen
- These very large openings (think of swiss cheese) allow for the passage of the largest molecules, including plasma
- Blood flow through sinusoids is very slow, allowing time for exchange of gases, nutrients, and wastes.
What is edema?
The presence of excess tissue fluid around the cells.
What are Varicose Veins?
Defective valves allow blood to accumulate within the veins, causing them to distend, twist, and become visible on the surface of the integument.
T or F: Systemic Veins contain 64% of blood volume.
True
Why do systemic veins hold so much blood?
Due to their high capacitance (capacity to expand) and readiness to store a high volume of blood, even at low pressure.
Why are veins more distensible than arteries?
Their large lumens and relatively thin walls
Which of the following statements is TRUE about a sinusoid capillary?
A. It has a complete basement membrane
B. In the liver and spleen, it facilitates the exchange of various molecules
C. It is the MOST common type of capillary
D. It is a main component of the blood-brain barrier
B. In the liver and spleen, it facilitates the exchange of various molecules
What is Pulse Pressure?
The difference between systolic and diastolic blood pressure
What is Mean Arterial Pressure (MAP)?
The average blood pressure in an individual over a cardiac cycle.
In the Arterial system, blood is pumped from the heart into the arteries at _____ pressure?
High
What happens if you increase pressure in the arteries (afterload), and the cardiac function does not compensate?
Blood flow will actually decrease.
In the Venous system, increased pressure in the veins ________ flow.
Increases
What are the 5 variables affecting blood flow and blood pressure?
- Cardiac output
- Compliance
- Volume of blood
- Viscosity of the blood
- Blood vessel length and diameter
What is Cardiac output?
Measurement of blood flow from the heart through the ventricles, and is usually measured in liters per minute
What is Compliance?
The ability of any compartment to expand to accommodate increased content
How does Volume of blood impact pressure and blood flow?
As blood volume decreases, pressure and flow decrease.
As blood volume increases, pressure and flow increase.
How does Viscosity of blood impact pressure and blood flow?
Thickness of fluids that affects their ability to flow
How does Blood Vessel Length and Diameter impact pressure and blood flow?
The length of a vessel is directly proportional to its resistance: the longer the vessel, the greater the resistance and the lower the flow.
What happens to Compliance, Pressure, and Resistance in the blood vessel due to Arteriosclerosis?
Compliance is reduced
Pressure/Resistance is increased
What are the 2 pumps of the Venous system?
Skeletal Muscle pump
Respiratory pump
What is the Skeletal Muscle pump?
The skeletal muscle pump helps veins counteract gravity by increasing pressure to move blood back to the heart; Muscle contractions compress veins, opening superior valves for upward blood flow while closing inferior valves to prevent backflow.
What is the Respiratory pump?
- The respiratory pump aids blood flow through the veins of the thorax and abdomen.
- On inhalation: Thoracic volume increases, lowering air and vein pressure, aiding blood return to the heart.
- On exhalation: Thoracic pressure rises, speeding blood flow to the heart while valves prevent backflow.
What is Vasoconstriction in arteries and arterioles?
Reduces radius, increases resistance and pressure, but decreases blood flow.
What is Venoconstriction of veins?
Makes the lumen more rounded, reducing surface area and resistance, facilitating smoother blood flow. Venoconstriction increases blood return to the heart by raising venous pressure to increase blood flow.
What is Bulk Flow?
What is Hydrostatic Pressure?
What is Osmotic Pressure?
Capillary Exchange: What occurs at +10mmHg?
Filtration, arterial end.
Fluid exits capillary since hydrostatic pressure is greater than the blood colloidal osmotic pressure.
Capillary Exchange: What occurs at 0mmHG?
No net movement since hydrostatic pressure = blood colloidal osmotic pressure.
Capillary Exchange: What occurs at -7mmHg?
Reabsorption, venous end.
Fluid re-enters capillary hydrostatic pressure is less than blood colloidal osmotic pressure.
What is the role of Cardioaccelorator centres?
Stimulate cardiac function by regulating heart rate and stroke volume via sympathetic stimulation from the cardiac accelerator nerve
What is the role of Cardioinhibitor centres?
Slow cardiac function by decreasing heart rate and stroke volume via parasympathetic stimulation from the vagus nerve.
What is the role of Vasomotor centres?
Control vessel tone or contraction of the smooth muscle in the tunica media.
What are Baroreceptors?
Specialized stretch receptors located within thin areas of blood vessels and heart chambers that respond to the degree of stretch caused by the presence of blood; Sends impulses to the cardiovascular center to regulate blood pressure.
What are Chemoreceptors?
Monitor levels of oxygen, carbon dioxide, and hydrogen ions (pH); they are in close proximity to the baroreceptors in the aortic and carotid sinuses.
Endocrine control over the cardiovascular system involves these 2 things:
- Catecholamines (epinephrine and norepinephrine)
- Hormones that interact with the kidneys in the regulation of blood volume.
What do Chemical Signals do in Autoregulation of Perfusion?
Work at the level of the precapillary sphincters to trigger either constriction or relaxation.
Why might the opening of percapillary sphincters be triggered?
- Decreased oxygen concentrations;
- Increased carbon dioxide concentrations;
- Increasing levels of lactic acid or other byproducts of cellular metabolism;
- Increasing concentrations of potassium ions or hydrogen ions (falling pH);
- Inflammatory chemicals such as histamines;
- Increased body temperature.
What is the Myogenic Response?
Reaction to the stretching of the smooth muscle in the walls of arterioles as changes in blood flow occur
through the vessel.
How does the Myogenic response affect perfusion?
If perfusion of an organ is too low (ischemia), the tissue will experience low levels of oxygen (hypoxia); Excessive perfusion could damage the organ’s smaller and more fragile vessels.
How does the Myogenic response affect blood flow?
- When blood flow is low, the vessel’s smooth muscle will be only minimally stretched. In response, it relaxes,
allowing the vessel to dilate and thereby increase the movement of blood into the tissue. - When blood flow is too high, the smooth muscle will contract in response to the increased stretch,
prompting vasoconstriction that reduces blood flow.
Why is Hypertension a silent disorder?
Hypertensive patients may fail to recognize the seriousness of their condition, which can lead to a heart attack, stroke, aneurysm (ballooning of a blood vessel caused by a weakening of the wall), peripheral arterial disease (obstruction of vessels in peripheral regions of the body), chronic kidney disease, or heart failure
What is a Hemorrhage?
A loss of blood that cannot be controlled by hemostatic mechanisms; Initially, the body responds to hemorrhage by
initiating mechanisms aimed at increasing blood pressure and maintaining blood flow.
To restore blood loss, these can be triggered by the body:
- The angiotensin-renin-aldosterone mechanism.
- The kidneys increase production of EPO to form erythrocytes.
What is the angiotensin-renin-aldosterone mechanism?
1) Stimulates the thirst center in the hypothalamus, which increases fluid consumption to help restore the lost blood.
2) Increases renal reabsorption of sodium and water, reducing water loss in urine output.
What are the 5 different types of shock the body can go into?
- Circulatory shock
- Hypovolemic shock
- Cardiogenic shock
- Vascular shock
- Obstructive shock
What is Circulatory shock?
The loss of too much blood; the circulatory system is unable to maintain blood flow to adequately supply sufficient oxygen and other nutrients to the tissues to maintain cellular metabolism.
What is Hypovolemic shock?
The loss of too much fluid (often caused by hemorrhage). In children it may be caused by fluid losses related to severe
vomiting or diarrhea. Other causes for hypovolemic shock include extensive burns, exposure to some toxins, and
excessive urine loss related to diabetes insipidus or ketoacidosis.
What is Cardiogenic shock?
The inability of the heart to maintain cardiac output. Most often, it results from a myocardial infarction (heart attack).
What is Vascular shock?
Occurs when arterioles lose their normal muscular tone and dilate dramatically.
–> Think about anaphylaxis.
What is Obstructive shock?
Occurs when a significant portion of the vascular system is blocked. It is not always recognized as a distinct condition and may be grouped with cardiogenic shock, including pulmonary embolism.
Which of the following responses occurs in the presence of high blood pressure?
A. Increased baroreceptor firing
B. Activation of cardiac accelerator centres
C. Activation of vasomotor centres
D. Suppression of cardiac inhibitor centres
A. Increased baroreceptor firing
What are some of the Major Arteries serving the Throax and Upper Limbs?
Axillary
Brachial
Radial
Ulnar
Palmar (deep and superficial)
Digital
What are some of the Major Arteries serving the Lower Limbs?
Femoral
Deep femoral
Genicular (knee)
Popliteal (behind knee)
Anterior tibial
Dorsalis pedis
Posterior tibial
Medial plantar
Lateral plantar
Dorsal or arcuate arch
Plantar arch
What are some of the Major Veins serving the Upper Limbs?
Digital
Palmar
Radial
Ulnar
Brachial
Median antebrachial
Basilic
Median cubital
Cephalic
Subscapular
Axillary
What are some of the Major Veins serving the Lower Limbs?
Plantar
Dorsal venous arch
Plantar venous arch
Anterior tibial
Posterior tibial
Fibular
Small saphenous
Popliteal
Great saphenous
Deep femoral
Femoral circumflex
Femoral
External iliac
Internal iliac
Middle sacral
Common iliac
What are the functions of the Liver?
- Packages nutrients absorbed by the digestive system
- Produces plasma proteins, clotting factors, and bile
- Disposes of worn-out cell components and waste products
What is the Hepatic Portal System?
Absorbed nutrients and certain wastes travel to the liver via the hepatic portal system for processing, bypassing direct entry into circulation; The liver processes the blood from the portal system to remove certain wastes and excess nutrients, which are stored for later use.
What is the Portal System Structure?
Portal systems start and end in capillaries; in this case, capillaries from digestive and circulatory organs (including the stomach, intestines, and spleen) lead to the hepatic portal vein and end in the hepatic sinusoids in the
liver.
What is the Dual Liver Blood Supply?
The liver receives blood from systemic circulation via the hepatic artery and from the hepatic portal vein for nutrient and waste processing.
How does the liver process blood?
The liver removes wastes and stores nutrients, maintaining stable systemic blood composition; Processed
blood exits via hepatic veins into the inferior vena cava.
List the following veins from most proximal to distal:
Ulnar
Digital
Subclavian
Subclavian
Ulnar
Digital
What is the placenta and umbilical vessels?
The placenta, formed from both embryonic and uterine structures, facilitates nutrient and gas exchange.
The umbilical vein delivers oxygenated blood to the fetal heart, while two umbilical arteries carry deoxygenated
blood and waste back to the placenta.
What are the 3 fetal shunts?
Ductus venosus
Foramen ovale
Ductus Arteriosus
What do the 3 fetal shunts do?
They redirect blood flow to adapt to nonfunctional fetal lungs; they close after birth as the newborn begins to breathe.
What is the Foramen ovale and where is it located?
Located in the interatrial septum allows blood to flow from the right atrium to the left atrium.
What is the Ductus Arteriosus and where is it located?
It is a temporary vessel, connecting the aorta to the pulmonary trunk.
What is the Ductus Venosus and where is it located?
It links the umbilical vein to the inferior vena cava largely through the liver.
