Human physiologyis: Blood and Circulation

Human physiology involves the study of how the human body functions, and blood circulation is a critical part of this system. Here's a basic overview of blood and circulation:

Blood

Blood is a specialized fluid in the human body that performs several essential functions critical for maintaining life. It circulates through the body, delivering oxygen and nutrients to tissues and removing waste products.

Blood is a fluid that carries vital substances throughout the body. It consists of:

1.Red blood cells (RBCs): Carry oxygen from the lungs to the rest of the body and bring carbon dioxide back to the lungs for exhalation.Red

●Blood Cells (RBCs) or Erythrocytes:

•Make up about 40-45% of blood volume.

•Function: Primary role is to transport oxygen from the lungs to the body’s tissues and bring carbon dioxide back to the lungs for exhalation.

•Hemoglobin: A protein in RBCs that binds oxygen, giving blood its red color.

●White blood cells (WBCs): Part of the immune system, they defend the body against infection.

•White Blood Cells (WBCs) or Leukocytes:Far fewer in number than red blood cells.

•Function: Play a critical role in the immune system by defending the body against infections and foreign invaders.Types of WBCs include neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

●Platelets: Help in blood clotting, preventing excessive bleeding when injured.Plasma: A liquid that makes up about 55% of blood, containing water, salts, proteins, hormones, and waste products.

•Platelets or Thrombocytes:Small, disc-shaped cell fragments.

•Function: Help in blood clotting by gathering at the site of an injury, sticking together to form a temporary plug, and working with clotting factors to form a stable clot to prevent excessive bleeding.

Components of Blood

Blood consists of four main components:

1.Plasma (55% of blood volume):A straw-colored liquid that makes up more than half of blood volume.

■ A straw-colored liquid that makes up more than half of blood volume.

■Contents: Water (90%), proteins, electrolytes, hormones, nutrients, and waste products.

■Functions: Carries dissolved substances such as glucose, amino acids, waste products, and hormones. It also helps maintain blood pressure and volu

Functions of Blood

Blood has several critical functions:

1.Transportation:Carries oxygen from the lungs to tissues and organs.Transports carbon dioxide from the tissues back to the lungs for exhalation.Delivers nutrients from the digestive system to cells and tissues.Carries waste products to the kidneys and liver for excretion.Distributes hormones throughout the body.

2.Regulation:Helps maintain homeostasis by regulating body temperature, pH levels (through buffering systems), and fluid balance.

3.Protection:White blood cells defend the body against infection by identifying and destroying pathogens.Platelets and clotting factors in blood prevent blood loss by forming clots.Antibodies and other immune proteins in plasma help fight off foreign invaders

Blood Groups

Humans have different blood types based on the presence of specific antigens on the surface of red blood cells:

ABO System: Blood types A, B, AB, and O.Rh

Factor: Blood is either Rh-positive (if the Rh antigen is present) or Rh-negative (if absent).

Blood VolumeThe average adult human has about 4-6 liters of blood, depending on body size and weight.

Circulation

Blood circulation is responsible for transporting oxygen, nutrients, hormones, and waste products throughout the body. It includes two primary circuits:

1.Pulmonary Circulation:

●Function: Moves deoxygenated blood from the heart to the lungs and back to the heart after oxygenation.

●Pathway: Blood flows from the right ventricle → pulmonary artery → lungs (where it picks up oxygen and releases carbon dioxide)→ pulmonary veins → left atrium.

2. Systemic Circulation:

●Function: Delivers oxygen-rich blood from the heart to the body’s tissues and returns oxygen-poor blood back to the heart.

●Pathway: Blood flows from the left ventricle → aorta → arteries → capillaries (where gas exchange occurs with body tissues) → veins → vena cava → right atrium.

The Heart

The heart is the central organ of circulation, and it functions as a pump:

●Four chambers: The right and left atria (upper chambers) and the right and left ventricles (lower chambers).

●Valves: Ensure one-way flow of blood through the heart and prevent backflow.

Blood Pressure

Blood pressure is the force exerted by circulating blood on the walls of blood vessels. It's controlled by factors like heart rate, blood volume, and the resistance of blood vessels.