Arteries and Veins: Quick Reference

Overview of Circulation

• Blood vessels transport blood to tissues for gas/nutrient/waste exchange, regulate flow and pressure, and secrete chemicals.

• Two main circuits:

  • Pulmonary circuit: heart ↔ lungs

  • Systemic circuit: heart ↔ rest of body

• Vessels: arteries, capillaries, veins (three-tier structure and function).

Vessel Structure and Tunics

• All vessels have lumen and three tunics:

  • Tunica intima

  • Tunica media

  • Tunica externa

• Arteries vs veins:

  • Arteries: thicker tunica media and more extensive elastic laminae; higher pressure.

  • Veins: thinner walls, valves common to prevent backflow; operate at lower pressure.

Arteries: Types and Features

• Three classes by structure/function:

  • Elastic arteries (conducting)

  • Muscular arteries (distributing)

  • Arterioles

• Key facts:

  • Elastic arteries: largest diameter; near the heart; high pressure; diameter $2.5\ \text{cm} \rightarrow 1.0\ \text{cm}$; extensive elastic laminae.

  • Muscular arteries: intermediate diameter; thick tunica media rich in smooth muscle; distribute blood to organs; diameter $1.0\ \text{cm} \rightarrow 0.3\ \text{mm}$.

  • Arterioles: small vessels controlling flow to tissues; diameter $0.3\ \text{mm} \rightarrow 10\ \mu\text{m}$; thin walls with smooth muscle.

• Capillaries are the exchange vessels; walls often only one cell thick.

Capillaries and Tissue Perfusion

• Capillary beds: networks between tissue cells and blood; gases, nutrients, wastes exchange across walls.

• Capillary structure: endothelial cells, basal lamina; pericytes support capillary stability.

• Tissue perfusion: blood flow through capillary beds is tightly regulated to meet metabolic needs.

Venous System: Types and Features

• Venules: smallest veins; diameter $8.0\ \mu\text{m} - 100\ \mu\text{m}$; endothelium with limited smooth muscle; merge into larger veins.

• Veins: larger lumen, thin walls, little smooth muscle; diameter $100\ \mu\text{m} - 1.5\ \text{cm}$; valves prevent backflow; drain capillary beds and return blood to the heart.

Atherosclerosis (Key Clinical Concept)

• Atherosclerosis: buildup of plaques (lipids, cholesterol, calcium, debris) in tunica intima; plaques tend to form at sites of flow changes (branch points, curves); major cause of death in developed world.

Systemic Arteries: Major Pathways

• Aorta: largest artery; divisions:

  • Ascending aorta

  • Aortic arch with branches; three main branches:

  • Brachiocephalic trunk → right common carotid & right subclavian

  • Left common carotid

  • Left subclavian

  • Descending thoracic aorta

  • Descending abdominal aorta; terminates as right and left common iliac arteries

• Arteries of head/neck:

  • Common carotid → external carotid (face/scalp) and internal carotid (brain); carotid sinus near its base

  • Vertebral arteries contribute to brain circulation

• Arteries of trunk and abdomen: celiac trunk, superior mesenteric, renal, inferior mesenteric, gonadal, hepatic, splenic, gastric branches, etc.

• Arteries of limbs:

  • Upper limb: subclavian → axillary → brachial → radial/ulnar; deep/superficial palmar arches

  • Lower limb: external iliac → femoral → popliteal → anterior/posterior tibial → dorsalis pedis

• Pulse points (highlights): temporal, carotid, brachial, radial, ulnar, femoral, popliteal, dorsalis pedis, posterior tibial

Head and Neck Arteries (Detail)

• Common carotids split into external and internal carotid; carotid sinus acts as a pressure sensor.

• Brain circulation includes anterior, middle, and posterior cerebral arteries; cerebral arterial circle (circle of Willis) connections via anterior and posterior communicating arteries.

Thoracic and Abdominal Arteries (Detail)

• Thorax: posterior intercostal arteries; posterior chest supply via descending aorta; anterior intercostal arteries; internal thoracic arteries provide thoracic wall blood

• Abdomen: hepatic, splenic, gastric supplies; celiac trunk distribution to stomach, spleen, liver; superior mesenteric and inferior mesenteric arteries supply intestines; renal and gonadal arteries supply respective organs

Systemic Veins: Major Pathways

• Venous return routes:

  • Superior vena cava forms from brachiocephalic veins (drains head, neck, thorax, upper limbs)

  • Inferior vena cava formed by merging common iliac veins (drains lower body)

• Hepatic portal system:

  • Drains nutrient-rich blood from digestive organs and spleen to liver via hepatic portal vein; liver processes blood and returns to systemic circulation via hepatic veins into the inferior vena cava

• Veins of the head/neck, upper limb, trunk, abdomen, and lower limb listed in flowcharts; many named veins mirror artery pathways (e.g., internal/external jugulars, axillary/brachial, femoral, etc.)

Hepatic Portal System (Key Concept)

• Purpose: deliver nutrient-rich blood to liver for processing; after processing, blood drains to the inferior vena cava via hepatic veins.

Quick Reference: Major Vessels by Region

• Head/Neck arteries: common carotid, internal/external carotid, vertebral

• Thorax arteries: intercostals, internal thoracic, aorta segments

• Abdominal arteries: celiac trunk, superior/inferior mesenteric, renal, gonadal, hepatic, splenic, common/ internal/external iliacs

• Upper limb arteries: subclavian → axillary → brachial → radial/ulnar

• Lower limb arteries: abdominal aorta → common iliac → internal/external iliac → femoral → popliteal → tibials/pedis

• Venous system: brachiocephalic veins → superior vena cava; common/iliac veins → inferior vena cava; hepatic portal system connects digestive organs to liver

Quick Reference: Capillaries and Perfusion

• Capillaries: exchange vessels; walls are typically one cell thick; RBCs traverse in single-file; pericytes present in many capillaries

• Tissue perfusion is tightly regulated to meet metabolic demands