Circulatory and respiratory system structure and function

SECTION 1: THE CIRCULATORY SYSTEM

The circulatory system, also known as the cardiovascular system, primarily consists of the heart, blood vessels, and blood.
The main function of this system is to transport oxygen, nutrients, hormones, and cellular waste products throughout the body.
The human heart has four chambers: two atria (plural of atrium) at the top and two ventricles at the bottom. The right side of the heart pumps deoxygenated blood to the lungs, and the left side pumps oxygenated blood to the body.
Blood vessels are categorised into three main types: arteries, veins, and capillaries. Arteries carry blood away from the heart, veins carry it towards the heart, and capillaries connect arteries and veins at the body’s tissues.
Blood carries oxygen, nutrients, and hormones to cells and removes waste products like carbon dioxide. It is composed of red blood cells, white blood cells, platelets and plasma.

SECTION 2: BLOOD FLOW AND BLOOD PRESSURE

Blood flow is the continuous movement of blood through the circulatory system, driven by the pumping action of the heart.
The cycle of blood flow is called the cardiac cycle and includes two stages: diastole, when the heart muscles relax and fill with blood, and systole, when the heart muscles contract and pump blood out.
Blood pressure is the force that blood exerts against the walls of the blood vessels. It is chiefly affected by the strength and rate of the heart’s contractions and the resistance of the blood vessels.

SECTION 3: THE RESPIRATORY SYSTEM

The respiratory system primarily includes the nose, trachea, lungs, and the diaphragm.
The main function of the respiratory system is to oxygenate blood and remove carbon dioxide through the process of respiration.
Inhaled air is warmed, moistened, and filtered in the nasal cavity before heading down the trachea.
The trachea divides into two bronchi which lead to the lungs. The bronchi branch off into smaller bronchioles which end in tiny, sac-like structures called alveoli.
Alveoli are where the gas exchange occurs. They are surrounded by a network of capillaries, allowing for the oxygen to pass into the blood, and carbon dioxide to be removed.

SECTION 4: RESPIRATION AND BREATHING

Respiration is the biochemical process where cells use oxygen to convert glucose into energy.
Breathing, or ventilation, is a mechanical process where air is inhaled into and exhaled out from the lungs. This process brings oxygen into the lungs and removes carbon dioxide.
The diaphragm and intercostal muscles play a critical role in breathing. During inhalation, these muscles contract, expanding the chest cavity and pulling air in. During exhalation, these muscles relax, reducing the chest cavity’s volume and pushing air out.