What is the Circulatory System?

Circulatory system describes both the cardiovascular system and the lymphatic system Both systems work closely together to move fluids around your body and protect it from disease The two systems help maintain homeostasis Both systems are made up of vessels Both systems are part of the body’s defense against bacteria, viruses and other pathogens

Your heart, blood and blood vessels make up your cardiovascular system Blood is the fluid that carries gases, nutrients and wastes through the body It is a closed circulatory system – the blood is carried in vessels that form a loop The lymphatic system is a group of organs and tissues that collect the fluids that leak from blood and returns it to the blood The leaked fluid is called lymph It is an open circulatory system – lymph can move in and out of the vessels

How Do The Systems Work Together?

Every time your heart pumps, a little fluid is forced out of the thin walls of the tiniest blood vessels called capillaries Most of the fluid is reabsorbed by the capillaries The rest of the fluid is collected by lymph capillaries Lymph capillaries absorb fluid, dead cells and pathogens from around body cells The fluid, called lymph is returned to the cardiovascular system when it drains into blood vessels at the base of the neck The lymphatic system is where white blood cells mature - where they attack invading pathogens

Parts of the Lymphatic System

Lymph nodes are small, bean – shaped organs that remove pathogens and dead cells from lymph Lymph nodes are concentrated in the armpits, neck and groin Infection – fighting cells, called white blood cells, are found in lymph nodes When pathogens cause an infection, the number of white blood cells can increase greatly the increased number causes the lymph nodes to become swollen and painful

Lymph vessels are the thin walled vessels of the lymphatic system They carry lymph back to lymph nodes From the lymph nodes, the fluid is returned to the cardiovascular system Vessels have valves inside them to stop lymph from flowing backwards Bone marrow is part of the lymphatic system – the soft tissue inside the bone produces blood cells Tonsils – small lymphatic organs at the back of the throat and tongue Help defend the body against infection

White blood cells in the tonsil tissue trap pathogens An infection of the tonsils is called tonsillitis – they become swollen and are painful Spleen – the largest lymphatic organ – it stores white blood cells and allows them to mature As blood flows through the spleen, white blood cells attack pathogens in the blood

Disorders of the Lymphatic System

Lymphoma is a type of cancer that often begins in a lymph node The swelling it can cause in the node is called a tumor Lymphedema is a swelling of body tissues caused by a blockage or injury to lymph vessels Lymph vessels are unable to drain lymph from a certain area and the area becomes swollen Bubonic plague is a bacterial infection of the lymphatic system The bacteria can enter the body through the bite of an infected flea

Parts of the Cardiovascular System

The cardiovascular system is the organ system that carries nutrients, gases and hormones to body cells and waste products from the body cells Heart – the pump that sends blood around the body when heart muscle contracts, it squeezes the blood inside the heart The squeezing creates a pressure that pushes blood through the body Your heart has a left side and a right side – the two sides are separated by a thick wall

Heart Anatomy

The right side of the heart pumps oxygen – poor blood to the lungs The left side pumps oxygen – rich blood to the body Each side has an upper chamber and a lower chamber The upper chamber is called an atrium The lower chamber is called a ventricle Blood enters the atria and is pumped down to the ventricles Flap – like structures called valves are located between the atria and the ventricles and where large vessels are attached to the heart – valves prevent blood from flowing backward

Blood

Blood is a type of connective tissue that is part of the cardiovascular system It serves as a transport system, providing supplies for cells, carrying chemical messages and removing wastes so cells can maintain homeostasis Blood contains cells, fluid and other substances It travels through miles and miles of blood vessels

Blood Vessels

Blood travels throughout your body in tubes called blood vessels The three types of blood vessels are arteries, capillaries and veins Arteries – blood vessels that carry blood away from the heart Each heartbeat pumps blood into your arteries at high pressure, which is your blood pressure Capillary – a tiny blood vessel that allows the exchange of carbon dioxide and wastes between body cells and the blood – capillary walls are one cell thick Vein – a blood vessel that carries blood back to the heart – not under as much pressure as arteries

What is Blood Made Of?

Plasma – the fluid part of the blood - a mixture of water, minerals, nutrients, sugars, proteins and other substances Platelets – tiny pieces of larger cells found in bone marrow When you cut yourself you bleed because blood vessels are cut open – as soon as bleeding starts, platelets begin to clump together to form a plug – reduces blood loss – release a chemical to form tiny fibers White blood cells – fight pathogens such as bacteria and viruses – when they find one they destroy it

Other white blood cells form antibodies Antibodies are chemicals that identify pathogens White blood cells destroy dead or damaged body cells Red blood cells – disk – shaped cells that do not have a nucleus They bring oxygen to every cell in your body Each red blood cell has hemoglobin – an oxygen – carrying protein The disk shape of the red blood cell helps them squeeze into capillaries

How Does Blood Move Through the Body?

Blood is pumped from the right side of the heart to the lungs From the lungs it moves into the left side of the heart From the left side of the heart the blood is pumped to the body Blood in the arteries that come out of the heart is under great pressure from the pumping action of the heart Veins carry larger volumes of blood more slowly – less pressure Blood moves in two loops or circuits –pulmonary circulation (blood flow between heart and lungs) and systemic circulation (blood flow between heart and the rest of the body)

How Does Circulation Help maintain Body Temperature?

When the brain senses that that body temperature is rising, it signals blood vessels in the skin to widen As the blood vessels get wider, heat from the blood is transferred to the air around the skin The transfer helps lower body temperature When the brain senses the body temperature is getting too low, it signals the blood vessels near the skin to get narrower This allows blood to stay close to internal organs to keep them warm

Problems that Affect the Cardiovascular System

Atherosclerosis – hardening of the artery walls caused by the build up of cholesterol and other lipids Build up causes the blood vessels to become narrower and less elastic Hypertension – abnormally high blood pressure – may be caused by atherosclerosis Heart attack – happens when an artery that supplies blood to the heart becomes blocked and the heart muscle tissue does not get oxygen Stroke – a blood vessel in the brain becomes blocked or bursts – as a result, that part of the brain receives no oxygen

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