The Respiratory System

The Respiratory System Process by which O2 and CO2 are exchanged between cells, the blood, and air in the lungs = respiration The human respiratory system has three phases of gas exchange: breathing, the ventilation of the lungs by alternate inhalation and exhalation, transport of oxygen from the lungs to the rest of the body via the circulatory system, and diffusion of oxygen from the blood and release of CO2 into the blood by cells of the body.

The Respiratory System (continued) Human Respiratory System Consists of the nose, pharynx, larynx, trachea, bronchi (singular bronchus), and lungs

The Respiratory System Figure 23.19a The Respiratory System Pharynx Nasal cavity Esophagus Larynx (voice box) Left lung Trachea (windpipe) Right lung Bronchus Bronchiole Diaphragm Heart (a) Overview of the human respiratory system

Passageway of Air Into the Lungs Air entering the lungs is warmed, moistened, and filtered by the nose and mouth, keeping lung tissue healthy Air enters pharynx – passageway for food and air Air then passes through the larynx – area containing vocal cords Air passes through trachea – the windpipe – which is covered by the epiglottis (flap of cartilage) when you swallow

Passageway of Air Into the Lungs (continued) Air then passes from the trachea into two large tubes in the chest called bronchi. Each bronchus leads to one of the lungs. The bronchi then branch out and get smaller and are called bronchioles Bronchi and bronchioles are surrounded by smooth muscle and help regulate the size of air passageways Bronchioles continue to get smaller and read “dead ends” – millions of tiny air sacs called alveoli. Alveoli are grouped into little clusters (like grapes) with capillaries surrounding each alveolus. This is where gas exchange takes place.

carbon dioxide exchange at Movement of Oxygen and Carbon Dioxide In and Out of the Respiratory System Nasal cavities Oxygen-rich air from environment Pharynx Trachea Bronchi Oxygen and carbon dioxide exchange at alveoli Bronchi Bronchioles Alveoli Bronchioles Nasal cavities Carbon dioxide-rich air to the environment Trachea Pharynx

Gas Exchange 350 million alveoli in healthy lung O2 dissolves on wet surface of alveoli and then diffuses into capillaries CO2 in blood, diffuses across membrane of alveolus and into the air of the lung Alveoli Bronchiole Capillary

Gas Exchange However, there is one problem with this simple gas delivery system. Problem: Oxygen does not readily dissolve in blood. Solution: Oxygen is carried in hemoglobin molecules within red blood cells.

Hemoglobin in Red Blood Cells Figure 23.23 Hemoglobin in Red Blood Cells Heme group Iron atom O2 O2 loaded in lungs O2 O2 unloaded in tissues Polypeptide chain

Breathing Movement of air into and out of lungs Air is driven into lungs by air pressure Bottom of chest cavity is the muscular diaphragm When you inhale, the diaphragm contracts and expands chest cavity = less pressure inside = vacuum that brings air into lungs When you exhale, the diaphragm relaxes and makes the chest cavity smaller = more pressure inside = air rushes out of lungs If chest cavity punctured, probably not be able to breathe

Breathing Inhalation Exhalation Air exhaled Air inhaled Rib cage descends Rib cage rises Diaphragm Diaphragm Inhalation Exhalation

Breathing Inhalation Exhalation Air exhaled Air inhaled Rib cage descends Rib cage rises Diaphragm Diaphragm Inhalation Exhalation

The Respiratory System

How Breathing is Controlled Breathing is NOT voluntary Nervous system controls breathing in the medulla oblongata which “senses” when CO2 levels rise = impulses sent to diaphragm to contract = breathe

Tobacco and the Respiratory System Tobacco destroys lung tissue Carbon Monoxide (CO) in tobacco prevents O2 from getting into blood and deprives body of O2 Smokers cough due to mucus and trapped smoke particles building up in airways

Healthy Lung Tissue vs. Diseased Lung Tissue

Tobacco and the Respiratory System (continued) Smoking causes chronic bronchitis, emphysema, cancer, and heart disease Chronic Bronchitis – swollen bronchi = exercise difficult Emphysema – loss of elasticity of lungs = breathing difficult Lung cancer – can spread to other parts of the body Heart disease – smoking causes high blood pressure = heart has to work harder