Body fluids and circulation

Blood is a fluid connective tissue that transports nutrients, gases, hormones, and wastes throughout the body.

Blood consists of plasma and formed elements such as RBCs, WBCs, and platelets.

Plasma is the liquid matrix of blood that contains water, proteins, minerals, glucose, and other solutes.

RBCs transport oxygen with the help of the pigment hemoglobin.

The average lifespan of RBCs is about 120 days.

WBCs are immune cells that protect the body against infections and foreign substances.

Platelets help in blood clotting and prevent excessive blood loss.

Lymph is a colorless fluid that helps in immune responses and the transport of absorbed fats.

Double circulation refers to the separate systemic and pulmonary pathways in which blood flows twice through the heart in one complete cycle.

The cardiac cycle is the sequence of events during one heartbeat, including systole and diastole.

Systole is the contraction phase of the heart chambers.

Diastole is the relaxation phase of the heart chambers.

Cardiac output is the amount of blood pumped by each ventricle per minute.

ECG is a graphical recording of the electrical activity of the heart.

The P-wave represents atrial depolarization.

The QRS complex represents ventricular depolarization.

The T-wave represents ventricular repolarization.

The SA node acts as the natural pacemaker of the heart.

Arteries are blood vessels that carry blood away from the heart under high pressure.

Veins are blood vessels that carry blood toward the heart under low pressure.