Circulatory System: Blood, Vessels, and Heart

• The circulatory system consists of blood, blood vessels, and the heart.

Blood

• Blood is a fluid tissue that transports nutrients and oxygen to cells, removing carbon dioxide and waste.
• Plasma is the fluid component of blood, containing various dissolved salts and nutrients.
• Blood cells, including red blood cells (RBCs), white blood cells (WBCs), and platelets, are suspended in plasma.

Red Blood Cells (RBCs)

• RBCs transport oxygen throughout the body.
• RBCs contain hemoglobin, a red pigment, which binds with oxygen.
• Hemoglobin gives blood its reddish color.

White Blood Cells (WBCs)

• WBCs defend against invading microbes that may cause illness.

Platelets

• Platelets are the smallest cells in the blood.
• They initiate blood clotting to prevent blood loss from bleeding.

Functions of Blood

• Carries carbon dioxide to the lungs for purification and oxygen from the lungs to the body.
• Delivers digested food to all areas of the body.
• Maintains steady body temperature.
• Transports waste products to the kidneys for excretion.

Blood Vessels

• There are three types: arteries, veins, and capillaries.

Arteries

• Arteries carry blood away from the heart.
• Arteries carry oxygenated blood, except for the pulmonary artery.
• Blood pressure is high in the arteries.
• Arteries have thick, muscular, elastic walls to pump and accommodate blood flow.
• The lumen (channel) of an artery is relatively narrow.

Veins

• Veins carry blood to the heart.
• Veins carry deoxygenated blood, except for the pulmonary vein.
• Blood pressure is low in the veins.
• Veins have thin walls with less muscular tissue than arteries.
• Veins have a wide lumen.

Capillaries

• Capillaries are much smaller than arteries and veins.
• Capillaries are only one cell thick.
• Substances like oxygen, glucose, and carbon dioxide can diffuse through capillary walls.
• Blood pressure is very low in capillaries.
• Gas exchange occurs in capillaries: oxygen passes into tissues, and carbon dioxide passes into the blood.

Heart

• Fist-sized, muscular organ located on the left side of the chest.
• The heart is a vital organ.
• It's divided into four chambers to prevent mixing of oxygenated and deoxygenated blood.
• The top two chambers are the left and right atria.
• The lower two chambers are the left and right ventricles.
• The heartbeat is the contraction and relaxation of the heart's chamber walls.
• Valves in the heart ensure blood flows in one direction.
• The "lub-dub" sound of the heartbeat is caused by the opening and closing of heart valves.

Pulmonary Circuit

• System of veins and arteries that connects the lungs and the heart.
• Blood that has lost oxygen is pumped to the lungs to replenish it.
• Then it returns to the heart to be recirculated.

Pulse

• The pulse refers to the rhythmic contraction and relaxation of heart muscles, producing the "lubb-dubb" sound.
• At rest, the average adult heartbeat is 72-80 beats per minute, increasing during and after exercise.
• The heartbeat rate equals the pulse rate per minute.

Stethoscope

• Instrument used to listen to the heartbeat.
• Used by doctors to amplify sounds of the heart.
• Consists of a chest piece with a diaphragm, two earpieces, and a connecting tube.

Human Excretory System

• The excretory system removes waste products from the body.

Kidneys

• The kidneys filter wastes from the blood, which are then removed in urine.
• Blood capillaries in the kidneys filter blood.

Urinary Bladder

• The urinary bladder stores urine produced in the kidneys.

Ureters

• Ureters are tubes connecting the kidneys to the urinary bladder.
• They transport urine from the kidneys to the urinary bladder.

Urethra

• The urethra is a muscular tube through which stored urine is expelled from the body.

Dialysis

• Dialysis is the filtering of blood outside the human body using a machine when both the kidneys fail.

Transportation in Plants

• Plants require carbon dioxide, water, and nutrients to survive.
• Leaves produce food through photosynthesis, combining carbon dioxide and water.

Root Hair

• Root hairs are elongated extensions of roots, increasing the surface area for water and mineral absorption.

Vascular Tissues

• Vascular tissues are of two types: xylem and phloem.

Xylem

• Xylem transports water and nutrients from the roots to other parts of the plant.

Phloem

• Phloem transports soluble organic material (food) produced during photosynthesis from the leaves to other parts of the plant.

Transpiration

• Transpiration is the evaporation of water through stomata on the leaf surfaces.
• Continuous evaporation creates a suction force that pulls water from roots upward through the plant.
• Transpiration is a necessary process, even though it causes water loss.
• The suction force helps draw water to great heights in tall trees.
• It produces a cooling effect on the plant, preventing damage from sunlight's heat.
• Also helps transport water and minerals to leaves for photosynthesis.
• Transpiration increases in hot, sunny, or windy conditions due to increased evaporation.
• Increased transpiration leads to increased water absorption through the roots.

An overview of the circulatory system, including the role of blood, blood cells, and the heart. Blood is a fluid tissue that transports nutrients and oxygen to cells, and platelets initiate blood clotting to prevent blood loss. Learn about the functions of blood.