Heart Structure and Blood Flow

Heart Structure

• The heart is a muscular organ responsible for pumping blood throughout the body via a network of blood vessels.
• The pericardium is a sac-like membrane that surrounds and protects the heart.
• The septum is a wall that vertically divides the heart into two sides.
• The atrium is an upper chamber of the heart.
• The ventricle is a lower chamber of the heart.
• The heart has four chambers consisting of the right and left atria, and the right and left ventricles.
• Atrioventricular valves separate the atria from the ventricles.
• Semilunar valves separate the ventricles from the blood vessels.

Blood Flow Through the Heart

• Blood flow: superior and inferior vena cava -> right atrium -> right ventricle -> pulmonary artery -> lungs -> pulmonary vein -> left atrium -> left ventricle -> aorta.

Blood Oxygenation in the Heart

• The right side of the heart contains deoxygenated blood, which has a low oxygen and high carbon dioxide concentration.
• The left side of the heart contains oxygenated blood, which has a high concentration of oxygen.

Heartbeat Control

• The sinoatrial (SA) node is a group of heart muscle cells that initiate electrical impulses, causing the atria to contract; it is known as the pacemaker and is located in the atrium.
• The atrioventricular (AV) node receives impulses from the SA node and causes the muscle cells of the ventricles to contract.

Blood Vessels

• Arteries are large, muscular vessels that carry blood away from the heart.
• Capillaries are tiny vessels that facilitate the exchange of materials at the cellular level.
• Veins are large blood vessels that carry blood back to the heart.

Blood Pressure

• Blood pressure is the force exerted by blood against the walls of blood vessels.
• Systolic pressure is the pressure when the ventricles contract.
• Diastolic pressure is the pressure when the ventricles relax.
• Blood pressure is represented by two numbers, such as 110/70, where 110 is the systolic and 70 is the diastolic pressure.

Lymphatic System

• The lymphatic system returns fluids leaked from the blood and filters foreign particles.
• Lymph is the excess fluid found in tissues.
• Lymph vessels are the vessels that collect lymph.
• Lymph nodes filter lymph.

Blood Composition

• Blood is composed of liquid and solid components, with a total volume of 4-5 liters in the body.
• Plasma is the liquid part of blood, consisting of water, vitamins, minerals, hormones, and waste products.
• Red blood cells transport oxygen to cells, with hemoglobin, an iron-containing protein, facilitating oxygen transport.
• White blood cells help defend the body against disease.
• Platelets are cell fragments that aid in the formation of blood clots.

Blood Types

• Blood type is determined by the type of antigen present on the red blood cell, classified as Type A, B, AB, and O.
• An antigen is a protein or carbohydrate that enables the body to recognize foreign substances.
  • A blood has A antigens and anti-B antibodies.
  • B blood has B antigens and anti-A antibodies.
  • AB blood has both A and B antigens.
  • O blood has no antigens but has both A and B antibodies.
• The Rh system indicates whether the Rh antigen is present (+) or absent (-).

Lung Function

• Lungs are the site of gas exchange between the atmosphere and blood.
• The lungs are surrounded by a membrane called the pleura.

Air Passage to the Lungs

• Air enters through the mouth and nose, where it is filtered, moistened, and warmed.
• The pharynx is a tube at the back of the nasal cavities.
• The epiglottis is a flap of cartilage that covers the air passage.
• The trachea is the main air passageway that traps particles.
• The larynx is the upper end of the trachea that contains vocal cords.
• The Bronchi are two branches off the trachea that lead to the lungs.
• Bronchioles are smaller tubes within the lungs.
• Alveoli are clusters of tiny air sacs surrounded by capillaries.

Gas Exchange in the Lungs

• Oxygen crosses the alveolar membranes and capillary walls into the blood.
• Carbon dioxide crosses the capillary walls and alveolar membranes, entering the alveoli.

Breathing Process

• Breathing involves moving air into and out of the lungs.
• Inspiration (inhaling):
  • The diaphragm contracts and pushes down.
  • The volume in the chest cavity expands, lowering air pressure.
  • Air rushes into the lungs.
• Expiration (exhaling):
  • The diaphragm relaxes.
  • The volume in the chest cavity decreases, increasing air pressure.
  • Air rushes out of the lungs.