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Circulatory System

•  The circulatory system is an organ system that passes nutrients (such as amino acids, electrolytes and lymph), gases, hormones, blood cells, etc. to and from cells in the body. The circulatory system help fight diseases, stabilize body temperature and pH, and to maintain homeostasis.
•    The discovery of blood circulation or blood flow was done by William Harvey in 1628.

•    The Blood flow is the continuous running of blood in the cardiovascular system.
•    The human body is made up of several processes all carrying out various functions.
•    The gastrointestinal system which aids the digestion and the absorption of food.
•    The respiratory system which is responsible for the absorption of O2 and elimination of C O2 .
•    The urinary system removes waste from the body. The cardiovascular system helps to distribute food, O2and other product of metabolism.
•    The reproductive system is responsible for perpetuating the species.
•    The nervous and endocrine system is responsible for coordinating the integration and function of other system.
•    There involve four parts of human body in blood circulatory system Heart, Arteries, Veins, and Blood


•    The heart is a myogenic muscular organ with a circulatory system which pumps blood throughout the blood vessels by repeated, rhythmic contractions. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek word kardia, for "heart".
•    The heart is mainly composed of cardiac muscle and connective tissue. Cardiac muscle is an involuntary striated muscle tissue found only in this organ and responsible for the ability of the heart to pump blood.
•    The human heart has a mass of between 250 and 350 grams and is about the size of a fist.
•    The heart holds a special place in our collective psyche as well.
•    The average lifetime total heartbeats is based on an average of 72 beats per minute during an average lifespan of 75 years.
•    72 beats per minute x 60 = 4,320 beats per hour. 4,320 beats per hour x 24 = 103,680 beats per day.
•    103,680 beats per day x 365 = 37,843,200 beats per year.
•    37,843,200 beats per year x 75 = 2,838,240,000 beats in an average lifetime.
•    Obesity, high blood pressure, and high cholesterol can increase the risk of developing heart disease.
•    Half the number of heart attacks occurs in people with normal cholesterol levels.
•    Heart disease is a major cause of death.
•    The factors such as exercise, diet, and overall well-being, including both emotional and physiological components, affect heart health in humans.


•    Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries.

Types of arteries

•    Pulmonary arteries - The pulmonary arteries carry deoxygenated blood that has just returned from the body to the heart towards the lungs, where carbon dioxide is exchanged for oxygen.

•    Systemic arteries - Systemics arteries can be subdivided into two types - muscular and elastic The larger arteries (>10mm diameter) are generally elastic and the smaller ones (0.1-10mm) tend to be muscular. Systemic arteries deliver blood to the arterioles, and then to the capillaries, where nutrients and gasses are exchanged.

•    Aorta- The aorta is the root systemic artery. It receives blood directly from the left ventricle of the heart via the aortic valve.

•    Arterioles- The Arterioles, the smallest of the true arteries, help regulate blood pressure by the variable contraction of the smooth muscle of their walls, and deliver blood to the capillaries.


Veins are similar to arteries but, because they transport blood at a lower pressure, they are not as strong as arteries. Like arteries, veins have three layers: an outer layer of tissue, muscle in the middle, and a smooth inner layer of epithelial cells. However, the layers are thinner, containing less tissue.


•    The word is derived from the name of the Roman deity of fresh water, Lympha.

•    Lymph is the fluid that circulates throughout the lymphatic system.
•    The lymph is formed when the interstitial fluid, the fluid which lies in the interstices of all body tissues is collected through lymph capillaries.
•    It is then transported though lymph vessels to lymph nodes before emptying ultimately into the right or the left subclavian vein, where it mixes back with blood.

•    Lymph returns protein and excess interstitial fluid to the circulation.
•    Lymph may pick up bacteria and bring them to lymph nodes where they are destroyed. Metastatic cancer cells can also be transported via lymph.
•    Lymph also transports fats from the digestive system.

Excretory System

The excretory system is a passive biological system that removes excess, unnecessary materials from human body. It is responsible for the elimination of the waste products from our body.

The excretory system in human has four organs- Kidneys, Skin, Liver and Lungs


The kidneys' main function is the removal of waste from the bloodstream by production of urine. They perform several homeostatic functions such as:

•    Maintain volume of extracellular fluid
•    Maintain ionic balance in extracellular fluid
•    Maintain pH and osmotic concentration of the extracellular fluid.
•    Excrete toxic metabolic by-products such as urea, ammonia, and uric acid.


•    The human skin makes the outer cover of the human body. The skin has protects the underlying muscles, bones, ligaments and internal organs.
•    There are at least five different pigments that determine the color of the skin. These pigments are found at different levels and places as described below.
•    Melanin: It is brown in color and present in the germinative zone of the epidermis.
•    Melanoid: It resembles melanin but is present diffusely throughout the epidermis.
•    Keratin: This pigment is yellow to orange in color. It is present in the stratum corneum and fat cells of dermis and superficial fascia.
•    Hemoglobin (also spelled haemoglobin): It is found in blood and is not a pigment of the skin but develops a purple color.
•    Oxyhemoglobin: It is also found in blood and is not a pigment of the skin. It develops a red color.

Skin performs the following functions:

•    Protection
•    Sensation
•    Heat regulation
•    Control of evaporation
•    Aesthetics and communication
•    Storage and synthesis
•    Excretion
•    Absorption
•    Water resistance


•    The human lungs are responsible for respiration in humans.
•    Humans have two lungs; together, these contain nearly 2,400 kilometres of capillaries and a total surface area of about 70 square metres (750 sq ft) (8.4 x 8.4 m) in adults, almost equal in to one side of a tennis court.
•    Each lung weighs approximately 1.1 kilograms.
•    The lungs change angiotensin I to angiotensin II.
•    They remove several blood-borne substances, e.g. PGE1, PGE2, PGF2α, leukotrienes, serotonin, bradykinin.

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