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GAS EXCHANGE IN HUMANS. The Human Respiratory System The human respiratory system is made up of lungs and a system of air tubes that carry air to and.

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Presentation on theme: "GAS EXCHANGE IN HUMANS. The Human Respiratory System The human respiratory system is made up of lungs and a system of air tubes that carry air to and."— Presentation transcript:

1 GAS EXCHANGE IN HUMANS

2 The Human Respiratory System The human respiratory system is made up of lungs and a system of air tubes that carry air to and from the lungs. LUNGS are the gas exchange organs in air- breathing vertebrates and in some other animals. DIAPHRAGM is a muscle that forms the floor of the chest cavity PLEURA each lung is covered with a two- layered membrane called pleura.

3 The Human Respiratory System Air passes through; The nose Pharynx Larynx Trachea Bronchi Bronchial tubes Bronchioles Alveoli

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6 THE NOSE: air enters through nostrils the spaces in the nose are called nasal passages hairs stop foreign substances from entering the wall of the nasal passages are covered with; Mucous membraneCells that have cilia moistens air They both trap bacteria, dust, and particles The Human Respiratory System

7 THE PHARYNX: from the nasal passages, air travels through the pharynx (throat) it connects the nasal cavity and oral cavity to larynx tonsils form a protective barrier at the junction of pharynx and oral cavity The Human Respiratory System

8 THE LARYNX: (VOICEBOX) it is mainly made up of cartilage vocal cords are two pairs of membranes streched across the inside of the larynx as air is breathed out, the vocal cords vibrate The Human Respiratory System

9 Epiglottis: To prevent chocking during swallowing food and liquids are blocked from entering the opening of the larynx by the epiglottis. The Human Respiratory System

10 TRACHEA: is made up of smooth muscle, cartilage and mucous membrane it’s always open by cartilage rings inside of it is lined with ciliated mucous membrane The Human Respiratory System

11 BRONCHI: in the middle of the chest cavity, trachea branches into two bronchi. they are made up of cartilage and lined with ciliated cells. when they enter the lungs, they form the bronchial tubes BRONCHIOLES: the bronchial tubes divide and subdivide, finally they become a group of tiny tubes called bronchioles The Human Respiratory System

12 ALVEOLI: each bronchiole ends in a tiny air chamber that looks like a cluster of grapes each chamber contains several cup-shaped cavities called alveoli the walls of the alveoli is only one cell-thick and they are the respiratory surface they are moist and surrounded by large no. of capillaries the exchange of O 2 and CO 2 between air and blood takes place through the capillaries. The Human Respiratory System

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14 Gas Exchange in Humans Gas exchange in humans can be divided into 4 stages; *Breathing is the movement of air into and out of the lungs *External respiration is the exchange of O 2 and CO 2 between the air and the blood in the lungs *Internal respiration is the exchange of O 2 and CO 2 between the blood and the body cells *O 2 and CO 2 transport is the movement of gases between the lungs and other body parts

15 DURING INHALATION (INSPIRATION) DURING EXHALATION (EXPIRATION) The diaphragm muscles contract and pull it down The diaphragm muscles relax, allowing the diaphragm to return to its domed shape (upward-arched) The intercostal (rib) muscles contract and pull the rib cage up and out. The intercostal (rib) muscles relax, allowing the ribs to move downwards under their own weight. Chest (thoracic) cavity volume increasesChest (thoracic) cavity volume decreases Pressure in the cavity decreases as (compared to atmosphere) Pressure in the cavity increases (as compared to atmosphere) Air is sucked into the respiratory tract & lungsAir is forced out through the system. AN ACTIVE PROCESSA PASSIVE PROCESS

16 Control of Breathing Breathing is mostly involuntary and it’s controlled by respiratory center in the brain. When [CO 2 ] increases in blood Chemoreceptors on aorta and some arteries detect changes Respiratory center in the brain is stimulated Nerves carry impulses to Diaphragm and chest muscles The rate and depth of breathing is increased [CO 2 ] is lowered in the blood

17 Control of Breathing ***CO 2 and lactic acid that is formed during heavy exercise increases the acidity of blood and stimulates respiratory center to increase breathing.

18 Control of Breathing

19 External and Internal Breathing External Respiration is the exchange of O 2 and CO 2 between the air and the blood in the lungs. After inhalation, the amount of O 2 in the alveoli is higher than in the blood So O 2 dissolves into moist lining of alveoli Then diffuses into blood that is the region where [O 2 ] is lower As the blood is pumped from heart, O 2 rich blood from lungs is carried to body tissues

20 External and Internal Breathing Blood that is rich in CO 2 from body tissues is returned to lungs Then diffuses into blood that is the region where [O 2 ] In the lungs, the amount of CO 2 in the blood is higher than the CO 2 in the alveoli CO 2 diffuses out of the blood into the alveoli

21 External and Internal Breathing Internal Respiration is the exchange of O 2 and CO 2 between the blood and the body cells. In the capillaries of the body tissues, O 2 diffuses from blood the body cells. CO 2 diffuses out of the cells into the blood. ***Each gas diffuses down a concentration gradient, that is each gas diffuses from a high concentration area to a low concentration area.

22 O 2 and CO 2 Transport Oxygen Transport 1.98% of oxygen is carried from lungs to body tissues by the hemoglobin in RBCs. (Hemoglobin holds O 2 loosely) Hb + O 2 HbO 2 (Hemoglobin) (Oxyhemoglobin) 2. 2% of oxygen is transported by blood plasma as dissolved O 2

23 O 2 and CO 2 Transport ** The amount of oxygen in the surrounding tissues determines whether hemoglobin will combine with oxygen or will release oxygen. In the lungs there is large amount of O 2 Hemoglobin combines with O 2 to form oxyhemoglobin When blood reaches to body cells, amount of O 2 in the surrounding is low Oxyhemoglobin breaks down into oxygen and hemoglobin

24 O 2 and CO 2 Transport

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26 Carbondioxide Transport 1.70% of CO 2 is transported in blood is carried in blood plasma. CO 2 + H 2 O H 2 CO 3 Carbonic anhydrase H 2 CO 3 quickly breaks down into H + ions and HCO 3 H 2 CO 3 H + + HCO 3 - (is held by (bicarbonate ions hemoglobin) diffuses into plasma) forms quickly by the enzyme found in RBCs

27 O 2 and CO 2 Transport 2. 20% of carbondioxide is transported by RBCs as carboxyhemoglobin. CO 2 + Hb HbCO 2 (carboxyhemoglobin) 3. 10% of carbondioxide that diffuses into blood is transported by blood plasma as dissolved CO 2.

28 O 2 and CO 2

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