Chapter 20: Vessels

20. Cardiovascular System: Blood Vessels & Circulation

20.1 Structure and Function of Blood Vessels

• Key Functions:

  • Transport blood to and from tissues for gas, nutrient, and waste exchange.

  • Regulate blood flow to tissues and control blood pressure.

  • Secrete various biochemical substances.

• Circuits:

  • Systemic circuit (84%)

  • Pulmonary circuit (9%)

  • Heart (7%)

• Types of Blood Vessels:

  • Arteries: Carry blood away from the heart.

  • Veins: Carry blood back to the heart.

  • Capillaries: Connect smallest arteries to smallest veins.

20.2 Blood Flow, Blood Pressure, and Resistance

• Venous System:

  • Requires pressure gradient to return blood to the heart.

  • Atrial diastole pressure and pumps (skeletal muscle and respiratory) assist.

• Varicose Veins:

  • Dilated, bulging veins often in the lower limbs; caused by conditions like obesity and prolonged standing.

    • These veins can lead to discomfort and complications such as swelling, pain, and in severe cases, ulcers or blood clots.

  • Hemorrhoids are a specific instance of varicose veins of the anal canal

• Atherosclerosis:

  • Arterial Disease characterized by plaque buildup(buildups of lipids, cholesterol, calcium salts, cellular debris) in arteries within arterial tunica intima, increasing the risk of heart attack and stroke.

    • tend to form in regions where blood undergoes sudden changes in velocity and direction of flow (branching points, curves)

    • vessel wall inflammation attracts phagocytes to cl

• Aneurysm:

  • Weakness in arterial wall leading to a localized dilation, potentially life-threatening due to risk of rupture.

20.3 Capillary Exchange

• Capillaries Function:

  • Thin-walled vessels that facilitate gas, nutrient, and waste exchanges.

  • Blood flows in and out of capillary beds via metarterioles and precapillary sphincters.

• Exchange Mechanism:

  • Hydrostatic Pressure (HP): Drives fluid out of capillaries into tissue.

  • Osmotic Pressure (OP): Draws fluid back into capillaries.

  • Balance between HP and OP allows for effective nutrient delivery and waste removal.

• Edema:

  • Accumulation of excess fluid in interstitial spaces, can result from high HP or low COP.

20.4 Homeostatic Regulation of the Vascular System

• Regulation Mechanisms:

  • Local Control: Autoregulation allows blood flow to match tissue activity.

  • Neural Control: Autonomic nervous system regulates heart rate and vessel diameter.

  • Hormonal Control: Hormones such as epinephrine, norepinephrine, and angiotensin II influence blood pressure.

• Baroreceptor Reflex:

  • Maintains blood pressure through rapid adjustments using glossopharyngeal and vagus nerves.

20.5 Circulatory Pathways

• Hepatic Portal System (HPS):

  • Vital for processing nutrients and detoxification.

  • Medications are affected by HPS metabolism; careful dosing is essential to avoid toxicity due to hepatic breakdown.

Miscellaneous

Aortic Aneurysms

• Tests like the thumb-palm test can help identify individuals at risk for aortic aneurysms, which can lead to significant morbidity and mortality if undiagnosed.