Essential Human Body Systems and Their Core Functions
Cardiovascular and Circulatory Systems
The circulatory system, often referred to as the cardiovascular system, is vital for maintaining life. It helps to fight off disease, regulate normal body temperature, and maintain the chemical balance necessary for the body’s homeostasis (a state of balance among all its systems).
Components of the Circulatory System
The circulatory system consists of four major components:
The Heart
About the size of two adult hands held together, the heart rests near the center of the chest. Thanks to consistent pumping, the heart keeps the circulatory system working at all times.
Arteries
Arteries carry oxygen-rich blood away from the heart to where it needs to go.
Veins
Veins carry deoxygenated blood back to the heart and then to the lungs where the blood receives oxygen.
Blood
Blood is the transport medium of nearly everything within the body. It transports hormones, nutrients, oxygen, antibodies, and other important substances needed to keep the body healthy.
Types of Circulation
There are three different types of circulation that occur regularly in the body:
Pulmonary Circulation
This part of the cycle carries oxygen-depleted blood away from the heart, to the lungs, and back to the heart.
Systemic Circulation
This is the part that carries oxygenated blood away from the heart and to other parts of the body.
Coronary Circulation
This type of circulation provides the heart itself with oxygenated blood so it can function properly.
The Respiratory System
The respiratory system, which includes air passages, pulmonary vessels, the lungs, and breathing muscles, aids the body in the exchange of gases between the air and blood, and between the blood and the body’s billions of cells. Most of the organs of the respiratory system help to distribute air, but only the tiny, grape-like alveoli and the alveolar ducts are responsible for actual gas exchange.
Respiratory Tract Divisions
Upper Respiratory Tract
Composed of the nose, the pharynx, and the larynx, the organs of the upper respiratory tract are located outside the chest cavity.
Lower Respiratory Tract
Composed of the trachea, the lungs, and all segments of the bronchial tree (including the alveoli), the organs of the lower respiratory tract are located inside the chest cavity.
The Nervous System
The nervous system has two major parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS is the primary command center for the body and is composed of the brain and spinal cord. The PNS consists of a network of nerves that connects the rest of the body to the CNS. The two systems work together to collect information from inside the body and from the environment outside it. The systems process the collected information and then dispatch instructions to the rest of the body, facilitating an appropriate response.
The Skeletal System
Bone, or osseous tissue, is a hard, dense connective tissue that forms most of the adult skeleton, the support structure of the body. In the areas of the skeleton where bones move (for example, the ribcage and joints), cartilage, a semi-rigid form of connective tissue, provides flexibility and smooth surfaces for movement. The skeletal system is the body system composed of bones and cartilage and performs the following critical functions for the human body:
- Supports the body
- Facilitates movement
- Protects internal organs
- Produces blood cells
- Stores and releases minerals and fat
The Muscular System
Muscles play a part in every function of the body. The muscular system is made up of over 600 muscles, which include three primary muscle types:
- Smooth muscle
- Skeletal muscle
- Cardiac muscle
Only skeletal muscles are voluntary, meaning you can control them consciously. Smooth and cardiac muscles act involuntarily.