Circulatory system: blood vessels

• The circulatory system transports gases, nutrients, and molecules while removing waste products and regulating body temperature.
• Blood vessels form the transport network for the circulatory system.
• The three major types of blood vessels include capillaries, veins, and arteries.

Capillaries

• These are the smallest blood vessels serving as the connective network between arteries and veins.
• They facilitate most of the molecular and gas exchange between blood and nearby tissues such as muscles, organs, and bones.

Veins

• These carry deoxygenated blood back to the heart.
• Blood is then pumped to the lungs for reoxygenation in the alveoli.
• Veins hold nearly 60% of the body's total blood volume.
• Blood flow is aided by skeletal muscle movement.
• Valves prevent the backward flow of blood.

Arteries

• These are the largest blood vessels.
• They carry oxygenated blood away from the heart to the body.
• Arteries consist of three layers: the tunica intima (inner), tunica media (middle), and tunica externa (outer).
• The layers are made of connective tissues and muscles.
• They provide strength and flexibility to withstand blood pressure.

Aorta Branches

• Major arteries direct blood flow, and their locations determine which anatomical structures receive blood.

Aorta

• It is the largest artery in the body arising from the left ventricle of the heart.
• It forms an arch that descends behind the heart into the abdomen.
• It carries oxygenated blood to major cranial, thoracic, and abdominal structures.
• At the iliac crest level, it branches into the left and right common iliac arteries.
• These supply blood to the lower limbs.

Thoracic Aorta

• The thoracic cavity is in the chest region between the neck and the diaphragm.
• The ascending aorta, aortic arch, and descending aorta (thoracic aorta) branch off from the aorta in this cavity.
• These segments supply oxygenated blood to organs and structures.
• The left and right internal thoracic arteries supply the front chest region.
• Other structures receiving blood include the esophagus, diaphragm, and lungs.

Ascending Aorta

• This part arises directly from the left ventricle.
• It branches into the coronary arteries.
• These provide blood to the heart muscle.
• Blockage can lead to heart disease and a higher risk of heart attack.

Arch of the Aorta

• As the aorta ascends, it bends to form the aortic arch.
• The aortic arch has three branches:
  • Brachiocephalic artery: supplies blood to the right side of the neck, skull, and right arm.
  • Left common carotid artery: supplies blood to the left side of the neck and skull.
  • Left subclavian artery: supplies blood to the left arm.

Descending Aorta

• The section of the aorta between the aortic arch and the diaphragm is the descending or thoracic aorta.
• Major branches include:
  • Bronchial arteries: supply blood to the lungs.
  • Mediastinal arteries: supply blood to chest lymph glands.
  • Esophageal arteries: supply blood to the esophagus.
• It also supplies blood to abdominal wall muscles, the diaphragm, and the pericardium.

Abdominal Aorta

• This is the portion of the aorta below the diaphragm in the abdominal cavity.
• Main branches are the celiac trunk and the common iliac arteries.
• It supplies blood to the digestive system, parts of the reproductive and urinary systems, and the lower limbs.

Celiac Trunk

• It is the first major branch from the abdominal aorta.
• It supplies blood to the liver, pancreas, gallbladder, spleen, and other digestive organs.
• Its three major branches include:
  • Left gastric artery: supplies blood to the stomach.
  • Common hepatic artery: supplies blood to the liver, stomach, pancreas, intestines, and gallbladder.
  • Splenic artery: supplies blood to the stomach and spleen.
  • Renal arteries: supplies blood to the kidneys.

Common Iliac Arteries

• These are the terminal branches of the abdominal aorta, dividing into left and right common iliac arteries.
• They further subdivide into external and internal iliac arteries and femoral arteries.
• These supply blood to the pelvic organs and lower limbs.