Circulatory System Module 10

Study Notes

Consists of the heart, blood vessels (arteries, veins, and capillaries), and blood
Responsible for circulating blood, nutrients, oxygen, hormones, and waste products throughout the body

Arteries: carry oxygenated blood away from the heart to various tissues and organs
- Have thick, muscular walls to withstand high pressure
Veins: carry deoxygenated blood back to the heart from the body’s tissues
- Have thinner walls than arteries and often contain valves to prevent backflow
Capillaries: tiny, thin-walled vessels where gas exchange and nutrient exchange occur between the blood and tissues

Right Atrium: receives deoxygenated blood from the body via the superior and inferior vena cavae
Right Ventricle: pumps deoxygenated blood to the lungs through the pulmonary artery
Left Atrium: receives oxygenated blood from the lungs via the pulmonary veins
Left Ventricle: pumps oxygenated blood to the rest of the body through the aorta

Myocardium: thick, middle layer of the heart wall, composed of cardiac muscle cells or cardiomyocytes
- Contracts rhythmically to pump blood throughout the body
- Striated, involuntary, highly resistant to fatigue
Pericardium: double-layered sac that surrounds and protects the heart
- Fibrous Pericardium: outer layer of dense connective tissue that provides protection and anchorage for the heart
- Serous Pericardium: inner layer composed of two sublayers
  - Parietal Layer: lines the fibrous pericardium
  - Visceral Layer (Epicardium): directly covers the outer surface of the heart and is continuous with the epicardium
Endocardium: innermost layer of the heart, consisting of endothelial cells and connective tissue
- Provides smooth lining for the chambers of the heart and covers the heart valves
- Helps reduce friction as blood flows through the heart and maintains the integrity of the heart’s structure
Epicardium: outer layer of the heart wall, adjacent to the myocardium
- Serves as protective layer and secretes lubricating fluid that reduces friction between the heart and surrounding structures

Network of vessels and organs that play a crucial role in maintaining fluid balance, immune function, and lipid absorption in the body
Lymphatic capillaries: tiny, thin-walled vessels located throughout the body's tissues
- Collect excess tissue fluid (interstitial fluid), proteins, and cellular debris from the interstitial spaces and transport it as lymph
Lymphatic vessels: larger vessels that collect lymph from lymphatic capillaries and transport it towards lymph nodes and eventually back into the bloodstream
- Serve as conduits for transporting lymph and immune cells throughout the body
- Have valves to prevent the backward flow of lymph and contain smooth muscle in their walls to help propel lymph forward
Lymphatic ducts: largest lymphatic vessels that drain lymph into the venous circulation
- Return lymph to the bloodstream, primarily through two main ducts: the thoracic duct