Cardiovascular System: Vessels and Circulation Vocabulary//STUDIED

Blood Vessels Anatomy

• Arteries: Carry blood away from the heart.
• Arterioles: Smallest artery branches.
• Capillaries: Site of diffusion between blood and interstitial fluid.
• Venules: Collect blood from capillaries.
• Veins: Return blood to the heart.

Vessel Wall Structure

• Tunica Intima: Innermost layer; includes endothelial lining.
• Tunica Media: Middle layer; contains smooth muscle.
• Tunica Externa: Outer layer; connective tissue.

Artery vs. Vein Differences

• Artery walls are thicker.
• Arteries have smaller, round lumens; veins have larger, flat lumens.
• Veins contain valves.

Arteries

• Contractility: Allows diameter change.
  • Vasodilation: Lumen enlargement.
  • Vasoconstriction: Lumen reduction.
• Elastic Arteries: Large vessels that transport large volumes of blood away from the heart.
• Muscular Arteries: Medium-sized distribution arteries with more muscle cells.
• Arterioles: Control resistance; called resistance vessels.
• Aneurysm: Weakening in artery wall leading to bulging. Risk of rupture.

Capillaries

• Exchange site in capillary networks.
• Diameter is about 8 micrometers.
• Form capillary beds between arterioles and venules.
• Collateral Arteries: Allow circulation if one capillary is blocked.
• Arteriovenous Anastomoses (AV Anastomoses): Direct connections between arterioles and venules, bypassing the capillary bed.

Veins

• Thinner walls, larger diameter than arteries.
• Venous Valves: Prevent backflow.
• Skeletal muscles compress veins, pushing blood toward the heart.

Blood Distribution

• Heart, arteries, and capillaries hold 30-35% of blood.
• Venous system holds 60-65%.
• Venous constriction forces blood into arterial side during hemorrhaging.

Special Circulation

• Brain: Cerebral vessels dilate when peripheral vessels constrict.
• Heart: Coronary arteries dilate with low oxygen or high lactic acid.
• Lungs: Pulmonary vessels dilate with increased oxygen levels.

Pulmonary Circuit

• Deoxygenated blood goes to lungs via pulmonary arteries.
• Oxygenated blood returns to heart via pulmonary veins.

Systemic Circuit - Arteries

• Ascending Aorta: Aortic sinus with branching off of coronary arteries
• Aortic Arch:
  • Brachiocephalic trunk: To brachium and head.
    • Right subclavian – to right arm
    • Right common carotid – to head
  • Left common carotid artery – to head
  • Left subclavian artery – to left arm
• Common Carotid Arteries: Blood supply to the brain.
  *External carotid artery – supplies tissues outside of the cranium
  *Internal carotid artery – supplies tissues inside the cranium; Interruption of blood flow to brain tissue results in a cerebrovascular accident (CVA) or stroke
• Descending Aorta: Divided by the diaphragm
  *Thoracic aorta:
  *Visceral branches supply the organs of the chest
  *Parietal branches supply the chest wall
  *Abdominal aorta:
  *Major branches to visceral organs (like spleen, liver, etc.) are unpaired
  *Branches to the body wall, kidneys, urinary bladder, gonads, etc. are paired

Systemic Circuit - Veins

• Superior Vena Cava: Returns blood from head, neck, and upper extremities.
• Inferior Vena Cava: Returns blood from the lower body.

Hepatic Portal System

• Connects two capillary beds; hepatic portal vein delivers nutrient-laden blood to the liver.

Fetal Circulation

• Umbilical Arteries: Carry blood to the placenta.
• Umbilical Vein: Drains into the inferior vena cava.
• Foramen Ovale → Fossa Ovalis
• Ductus Arteriosus → Ligamentum Arteriosum

Aging - Cardiovascular System Changes

• Blood: Decreased hematocrit, blood clots, blood pooling.
• Heart: Decreased cardiac output, reduced elasticity, atherosclerosis.
• Blood Vessels: Decreased elasticity, aneurysm, calcium deposits, atherosclerosis.