Understanding the Cardiovascular and Lymphatic Systems
The cardiovascular system consists of:
- A pump (the heart) that circulates fluid (blood).
- A circulating fluid (blood) containing substances and cells that need to be transported.
- A network of vessels through which blood circulates.
It has several functions:
- Transports nutrients from the digestive system to all body tissues.
- Takes oxygen from the respiratory system to cells.
- Collects waste products produced by cell metabolism.
- Takes specialized defense cells and molecules to tissues infected by pathogenic microorganisms.
- Distributes hormones produced by the endocrine glands.
- Helps to regulate body temperature.
Blood Components
Blood is made up of various types of cells:
- Blood plasma: A yellowish fluid.
- Red blood cells: They are red because they contain hemoglobin.
- White blood cells: There are two types: granulocytes and agranulocytes.
- Platelets: Fragments of cells made in the red bone marrow.
Blood Vessels
There are three types of blood vessels:
- Capillaries: Microscopic vessels that form a network and take blood to all cells in the body.
- Arteries: Take blood from the heart to the rest of the body.
- Veins: Collect blood from the body and take it into the heart.
The Heart
The heart is a muscular organ consisting of the following layers:
- Endocardium: A layer of epithelial tissue that lines the inside of the heart.
- Myocardium: This middle layer is the thickest part of the heart.
- Pericardium: A double membrane surrounding the heart.
Parts of the Heart
Key parts include:
- Superior vena cava
- Aorta
- Pulmonary artery
- Pulmonary veins
- Right atrium
- Left atrium
- Tricuspid valve
- Mitral valve
- Right ventricle
- Left ventricle
- Interventricular septum
- Inferior vena cava
Cardiac Cycle
- Atrial systole: Atria contract and push blood into the ventricles via the mitral and tricuspid valves.
- Ventricular systole: The ventricles contract and push blood through semilunar valves.
- Diastole: The cardiac muscle relaxes, and the atria fill with blood.
Blood Circulation
Blood circulation is:
- Closed: Blood always circulates through blood vessels and never leaves them.
- Double: Blood must flow through the heart twice to complete a circuit.
- Complete: Oxygenated and deoxygenated blood never mix; they circulate through different circuits.
Pulmonary Circuit
Deoxygenated blood in the right atrium flows through the tricuspid valve into the right ventricle.
Lymphatic System
Lymph nodes: Organs formed by an internal network of fibers.
Lymph vessels: Narrow tubes with closed sacs at the end, found throughout the body.
Lymph: A colorless liquid that circulates through the lymph vessels, formed of intestinal fluid and blood plasma.
Functions of the Lymphatic System
- Absorption of fats from digested foods: After food has been digested, fats are absorbed by the mucosa of the small intestine.
- Interstitial fluid drainage: Blood capillaries filter out substances and pass them into the interstitial fluid that bathes cells.
- Formation of immune system cells: The lymph nodes store infectious organisms collected by the lymph as it travels through the body.
Excretory System
Elimination of the waste products resulting from the metabolic activity of cells.
Urinary System
Kidneys: Two bean-shaped organs, approximately 15 cm long, surrounded by a thick layer of fat and formed by nephrons.
Ureters: Two…