Named Blood Vessels and Circulatory Routes: Pulmonary and Systemic Circulation

Named Blood Vessels

Introduction

The study of named blood vessels is essential for understanding the anatomy and physiology of the circulatory system. Blood vessels are classified based on their structure, function, and the regions they supply or drain. This section introduces the major types and routes of blood vessels in the human body.

Circulatory Routes

Overview of Circulatory Pathways

Blood circulates through the body via distinct routes, each serving specific physiological functions. The main circulatory routes include the simple path, portal system, and anastomosis.

• Simple Path: The most direct route, where blood flows from an artery to a capillary and then to a vein.

• Portal System: Involves a sequence of two capillary beds before returning to the heart. This is seen in the hepatic portal system, where blood passes through the capillaries of the digestive organs and then through the liver.

• Anastomosis: A vessel merger that occurs without an intervening capillary bed, allowing for alternative routes of blood flow.

Figure 21.12 illustrates these circulatory routes, showing the flow of blood through arteries, capillaries, and veins.

The Pulmonary Circuit

Structure and Function

The pulmonary circuit is responsible for transporting blood between the heart and lungs for gas exchange. It is unique in that it is the only circuit where arteries carry oxygen-poor blood and veins carry oxygen-rich blood.

• Pulmonary Trunk: The single vessel that exits the right ventricle and splits into the pulmonary arteries.

• Pulmonary Arteries: Carry oxygen-poor blood from the right ventricle to the lungs. There is one pulmonary artery for each lung.

• Lobar Arteries: Branches of the pulmonary arteries that supply each lobe of the lungs.

• Alveolar Capillaries: Surround the alveoli, facilitating gas exchange (oxygen uptake and carbon dioxide removal).

• Pulmonary Veins: Carry oxygen-rich blood from the lungs to the left atrium. There are two pulmonary veins from each lung.

Key Points

• Arteries in the pulmonary circuit carry deoxygenated blood.

• Veins in the pulmonary circuit carry oxygenated blood.

Example

Blood leaves the right ventricle via the pulmonary trunk, travels through the pulmonary arteries to the lungs, exchanges gases in the alveolar capillaries, and returns to the left atrium via the pulmonary veins.

The Pulmonary Circulation

Detailed Anatomy

The pulmonary circulation includes all vessels involved in transporting blood to and from the lungs. The diagram shows the heart, lungs, and associated vessels, highlighting the path of blood flow and the site of gas exchange in the alveoli.

• Pulmonary trunk branches into left and right pulmonary arteries.

• Lobar arteries supply each lung lobe.

• Alveolar capillaries are the site of gas exchange.

• Pulmonary veins return oxygenated blood to the heart.

Additional info:

Gas exchange occurs in the alveoli, where oxygen diffuses into the blood and carbon dioxide diffuses out.

Major Arteries of the Systemic Circulation

Overview

The systemic circulation supplies oxygenated blood to all body tissues and returns deoxygenated blood to the heart. Major arteries are named based on the regions they supply.

• Aorta: The largest artery, originating from the left ventricle and branching into major arteries.

• Brachiocephalic artery: Supplies the right arm and head.

• Common carotid arteries: Supply the head and neck.

• Subclavian arteries: Supply the arms.

• Celiac trunk, superior mesenteric, and inferior mesenteric arteries: Supply abdominal organs.

• Renal arteries: Supply the kidneys.

• Common iliac arteries: Supply the pelvis and lower limbs.

Table: Major Systemic Arteries and Their Regions

Artery	Region Supplied
Aorta	Entire body (via branches)
Brachiocephalic	Right arm, head
Common carotid	Head, neck
Subclavian	Arms
Celiac trunk	Stomach, liver, spleen
Superior mesenteric	Small intestine, part of large intestine
Renal	Kidneys
Common iliac	Pelvis, lower limbs

Example

The brachial artery supplies blood to the upper arm, while the femoral artery supplies the thigh.

Additional info:

Arteries are typically named for the region or organ they supply, and their branching pattern is consistent among individuals.