Respiratory Tract

HUMAN RESPIRATORY TRACT SYSTEM

Structure

Complete respiratory system

The respiratory tract is divided into the upper airways and lower airways. The upper airways or upper respiratory tract includes the nose and nasal passages, the pharynx, and the portion of the larynx above the vocal cords. The lower airways or lower respiratory tract includes the portion of the larynx below the vocal cords, trachea , bronchi and bronchioles. The lungs can be included in the lower respiratory tract or as separate entity and include the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

The respiratory tract can also be divided into a conducting zone and a respiratory zone, based on the distinction of transporting gases versus exchanging them.

From the bronchi, the dividing tubes become progressively smaller with an estimated 20 to 23 divisions before ending at an alveolus.

Upper respiratory tract

 

The upper respiratory tract, can refer to the parts of the respiratory system lying above the sternal angle (outside of the thorax), above the glottis (vocal cords), or above the cricoi cartilage. So that the larynx is sometimes included in the upper airway and sometimes in the lower airway.The larynx is also called the voice box and has the associated cartilage that produces sound. The tract consists of the nasal cavity and paranasal sinuses, the pharynx  and sometimes includes the larynx.

Lower respiratory tract

The lower respiratory tract or lower airway is derived from the developing foregut and consists of the trachea, bronchi (primary, secondary and tertiary), bronchioles (including terminal and respiratory), and lungs (including alveoli. It also sometimes includes the larynx.

ALVEOLI

Our bodies perform certain functions every second of the day and night without our conscious awareness. For example, breathing is a job that our body does for us, whether we are asleep or awake, conscious or unconscious. But what is the actual purpose of breathing, other than merely keeping us alive? You probably already know that it has to do with taking in oxygen and getting rid of carbon dioxide. In this lesson, we will learn about tiny organs that help our body parts get the oxygen that we breathe in and get rid of the carbon dioxide we don't need. These organs are called alveoli.

HEART



The heart is a muscular organ in humans and other animals, which pumps blood through the blood vessels of the circulatory system. Blood provides the body with oxygen and nutrients, and also assists in the removal of metabolic wastes. The heart is located in the middle compartment of the mediastinum in the chest.

In humans, other mammals and birds the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. Fish in contrast have two chambers, an atrium and a ventricle, while reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.