Arterial and Venous Circulation: Structure and Function in Human Anatomy

Circulatory Pathways

Pulmonary Circulation

Pulmonary circulation is responsible for oxygenating blood by transporting it from the heart to the lungs and back. Deoxygenated blood leaves the right ventricle via the pulmonary artery, travels to the lungs, and returns oxygenated to the left atrium.

• Function: Oxygenates blood

• Pathway: Right ventricle → pulmonary artery → lungs → left atrium

Systemic Circulation

Systemic circulation delivers oxygenated blood to body tissues and returns deoxygenated blood to the heart. It begins at the left ventricle and ends at the right atrium.

• Function: Supplies tissues with oxygen and nutrients

• Pathway: Left ventricle → aorta → body tissues → right atrium

Arteries of the Systemic Circulation

Major Arterial Branches

The aorta is the largest artery, branching into several major arteries that supply the head, neck, upper extremities, thorax, abdomen, and lower limbs.

• Ascending Aorta: First to exit the heart; branches into coronary arteries

• Aortic Arch: Has three main branches: brachiocephalic, left common carotid, left subclavian

• Brachiocephalic: Supplies right arm and head; branches into right common carotid and right subclavian

• Left Common Carotid: Supplies left side of head

• Left Subclavian: Supplies left upper extremity and thorax

Arteries Supplying the Head

Four main arteries supply the head: two vertebral arteries and two common carotids. Vertebral arteries arise from the subclavian and enter the skull via the foramen magnum, forming the basilar artery. Common carotids travel up lateral to the trachea and split into internal and external carotids at the hyoid bone.

• Vertebral Arteries: Enter skull through foramen magnum; unite to form basilar artery

• Common Carotids: Split into internal (supplies brain) and external (supplies face and scalp) carotids

External Carotid Artery Branches

The external carotid artery supplies structures outside the skull and has several branches.

• Lingual: Supplies floor of mandible and tongue

• Facial: Supplies face; travels under mandible

• Maxillary: Supplies maxillary region

• Superficial Temporal: Supplies scalp and external jaw muscles; pulse point

Internal Carotid Artery and Circle of Willis

The internal carotid artery supplies the brain and enters the skull through the carotid canal. The Circle of Willis is a circular anastomosis that provides collateral blood supply to the brain, fed by internal carotids and the basilar artery.

• Circle of Willis: Ensures continuous blood supply to the brain

• Anastomosis: Connection between blood vessels for safety

Arteries of the Upper Extremity

Major Arteries

The upper extremity is supplied by a series of arteries that change names as they pass anatomical landmarks.

• Subclavian: Becomes axillary after passing the first rib

• Axillary: Travels through the axilla

• Brachial: Travels through the arm; pulse point

• Radial: Lateral forearm; radial pulse

• Ulnar: Medial forearm

Arteries of the Thorax and Abdominal Cavity

Thoracic and Abdominal Aorta

The aorta descends through the thorax and abdomen, giving rise to several important branches.

• Thoracic Aorta: Small intercostal arteries

• Abdominal Aorta: Branches include celiac trunk, superior mesenteric, suprarenal, renal, gonadal, inferior mesenteric, and common iliacs

Abdominal Aorta Branches

• Celiac Trunk: Left gastric, hepatic, splenic

• Superior Mesenteric: Pancreas, small intestine, upper large intestine

• Suprarenal: Adrenal glands

• Renal: Kidneys

• Gonadal: Testicular/ovarian

• Inferior Mesenteric: Lower large intestine, sigmoid colon, rectum

• Common Iliacs: Split at pelvis

Arteries of the Lower Limbs

Major Arteries

The lower limbs are supplied by arteries that branch from the external iliac and femoral arteries.

• Femoral: Continuation of external iliac

• Popliteal: Behind the knee; branches into anterior tibial, posterior tibial, and peroneal arteries

• Anterior Tibial: Supplies anterior compartment and dorsal foot

• Posterior Tibial: Supplies posterior compartment and plantar foot

• Peroneal: Supplies lateral compartment

Fetal Blood Circulation

Special Fetal Structures

Fetal circulation includes unique structures that bypass certain organs to optimize oxygen delivery.

• Ductus Arteriosus: Connects pulmonary artery to aorta; becomes ligamentum arteriosum

• Foramen Ovale: Opening between atria; becomes fossa ovalis

• Ductus Venosus: Shunts blood from umbilical vein to inferior vena cava; becomes ligamentum teres

• Umbilical Vein and Arteries: Carry oxygenated and deoxygenated blood to and from placenta

Venous Circulation

Major Veins

Venous circulation returns deoxygenated blood to the heart via the superior and inferior vena cava.

• Superior Vena Cava: Drains upper body

• Brachiocephalic Veins: Right and left; continue as subclavian veins

• External Jugular: Drains head, neck, face, scalp

• Internal Jugular: Drains cranium, face, neck; travels with carotid artery and vagus nerve

Veins of the Upper Extremity

• Subclavian Veins: Continue as axillary veins

• Axillary Veins: Continue as brachial veins

• Cephalic Veins: Superficial, lateral arm

• Basilic Veins: Superficial, medial arm

• Median Cubital Vein: Connects cephalic and basilic veins; common site for blood draws

Veins of the Thorax and Abdomen

• Azygos and Hemiazygos Veins: Drain intercostal veins into superior vena cava

• Inferior Vena Cava: Drains lower body; passes through liver

• Hepatic Veins: Drain liver

• Renal Veins: Drain kidneys

• Genital Veins: Drain testicular/ovarian tissue

Veins of the Lower Limbs

• Common Iliac Veins: Drain into inferior vena cava

• Internal Iliac Veins: Drain pelvic organs

• External Iliac Veins: Continue as femoral veins

• Femoral Veins: Medial, posterior thigh

• Popliteal Veins: Behind knee; branches into anterior and posterior tibial veins

• Great Saphenous Vein: Superficial, medial leg; used in bypass surgery

Hepatic Portal System

Function and Structure

The hepatic portal system receives nutrient-rich, unoxygenated blood from digestive organs and delivers it to the liver for processing. It is defined by vessels lying between two capillary beds.

• Portal Vein: Formed by veins draining digestive organs

• Branches: Inferior mesenteric, superior mesenteric, splenic, gastroepiploic veins

• Function: Stores nutrients, detoxifies substances, cleans blood

Summary Table: Major Arteries and Veins

Region	Major Arteries	Major Veins
Head/Neck	Common carotid, vertebral, external/internal carotid	External/internal jugular, brachiocephalic
Upper Extremity	Subclavian, axillary, brachial, radial, ulnar	Subclavian, axillary, brachial, cephalic, basilic, median cubital
Thorax	Thoracic aorta, intercostal	Azygos, hemiazygos
Abdomen	Abdominal aorta, celiac trunk, mesenteric, renal, gonadal	Inferior vena cava, hepatic, renal, genital
Lower Extremity	Femoral, popliteal, tibial, peroneal	Femoral, popliteal, saphenous, iliac

Key Terms and Concepts

• Anastomosis: Connection between blood vessels for collateral circulation

• Pulse Points: Locations where arteries are close to the skin and pulse can be felt (e.g., radial, brachial, superficial temporal)

• Collateral Blood Supply: Alternative routes for blood flow in case of blockage

• Portal System: Vessel between two capillary beds (e.g., hepatic portal system)

Clinical Relevance

• Stroke: Disruption of blood supply to the brain

• Berry Aneurysm: Weakness in vessel wall, often in Circle of Willis

• Blood Draws: Median cubital vein is commonly used

• Bypass Surgery: Great saphenous vein is often harvested