Surviving in Thin Air People cannot survive in

Surviving in Thin Air People cannot survive in the air at the world’s highest peaks in the Himalayan Mountains Twice a year, flocks of geese migrate over the Himalayas How can geese fly where people cannot breathe? Copyright © 2009 Pearson Education, Inc.

MECHANISMS OF GAS EXCHANGE Copyright © 2009 Pearson Education, Inc.

Gas exchange in an animal with lungs Three phases of gas exchange 1. Breathing 2. Transport of oxygen and carbon dioxide in blood 3. Body tissues take up oxygen and release carbon dioxide Cellular respiration requires a continuous supply of oxygen and the disposal of carbon dioxide Copyright © 2009 Pearson Education, Inc.

O 2 1 CO 2 Breathing Lung Circulatory system 2 Transport of gases by the circulatory system Mitochondria 3 Exchange of gases with body cells CO 2 Capillary Cell O 2

Animals exchange O 2 and CO 2 across moist body surfaces Respiratory surfaces must be thin and moist for diffusion of O 2 and CO 2 Cut Cross section of respiratory surface (the outer skin) Body surface Respiratory surface (gill) CO 2 Capillaries CO 2 Copyright © 2009 Pearson Education, Inc. Capillary

Body surface CO 2 O 2 Respiratory surface (within lung) O 2 Capillary

The evolution of lungs facilitated the movement of tetrapods onto land – Tetrapod adaptation: Fossil fish with legs had lungs and gills – Legs may have helped them lift up to gulp air – The fossil fish Tiktaalik illustrates these airbreathing adaptations Copyright © 2009 Pearson Education, Inc.

In the human respiratory system From the nasal cavity, air next passes to… Nasal cavity Pharynx (Esophagus) Larynx Left lung Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) Copyright © 2009 Pearson Education, Inc.

What do the alveoli do? Oxygen-rich blood Nasal cavity Pharynx (Esophagus) Larynx Oxygen-poor blood Bronchiole Alveoli Left lung Trachea Right lung Bronchus Blood capillaries Bronchiole Diaphragm (Heart)

Oxygen-rich blood Oxygen-poor blood Bronchiole Alveoli Blood capillaries

Alveoli are site for gas exchange Alveoli are well adapted for gas exchange – High surface area of capillaries – High surface area of alveoli Oxygen-rich blood Oxygen-poor blood Bronchiole Alveoli In alveoli – O 2 diffuses into the blood – CO 2 diffuses out of the blood Copyright © 2009 Pearson Education, Inc. Blood capillaries

Why is smoking is a serious assault on the respiratory system?

The fun effects of smoking 1. Damages cilia and decreases mucus production in the respiratory passages Copyright © 2009 Pearson Education, Inc.

The fun effects of smoking 1. Damages cilia and decreases mucus production in the respiratory passages 2. And also… – Increases the risk of heart attacks and strokes (increases heart disease) – Raises blood pressure – Increases harmful types of cholesterol – Causes lung cancer (90%) – Causes emphysema Copyright © 2009 Pearson Education, Inc.

Here’s the 411 Every year in the United States, smoking kills about 440, 000 people – This is more than all the deaths from accidents, alcohol, drug abuse, HIV, and murders combined Adults who smoke cut 13– 14 years from their lifespan Copyright © 2009 Pearson Education, Inc.

Lung Heart

How is breathing controlled?

Breathing is automatically controlled Breathing is usually under automatic control= breathing control center in brain As CO 2 increases (and p. H decreases) in blood rate of depth of breathing increases Copyright © 2009 Pearson Education, Inc.

Cerebrospinal fluid Brain Pons 1 Nerve signals trigger contraction of muscles Diaphragm Rib muscles Medulla

Cerebrospinal fluid Brain Pons 2 Breathing control 1 Nerve signals trigger contraction of muscles Diaphragm Rib muscles Medulla centers respond to p. H of blood

Cerebrospinal fluid Brain Pons 2 Breathing control 1 Nerve signals trigger contraction of muscles Medulla centers respond to p. H of blood 3 Nerve signals indicating CO 2 and O 2 levels CO 2 and O 2 sensors in aorta Diaphragm Rib muscles

How are gasses (O 2 and CO 2) transported throughout body? Copyright © 2009 Pearson Education, Inc.

BLOOD The heart pumps blood to two regions – The right side pumps oxygen-poor blood to the lungs – The left side pumps oxygen-rich blood to the body In the lungs, blood picks up O 2 and drops off CO 2 In the body tissues, blood drops off O 2 and picks up CO 2 Copyright © 2009 Pearson Education, Inc.

Blood transports respiratory gases Gases move from areas of higher concentration to areas of lower concentration – Example: Gases in the alveoli of the lungs have more O 2 and less CO 2 than gases the blood – How does this happen? ? – Diffusion down the pressure gradient – Each gas exerts a pressure called partial pressure Copyright © 2009 Pearson Education, Inc.

What physically carries the respiratory gasses in the blood?

Hemoglobin carries O 2, helps transport CO 2, and buffers the blood Most animals transport O 2 bound to proteins called respiratory pigments – Iron-containing hemoglobin – Is used by almost all vertebrates and many invertebrates – Transports oxygen, buffers blood, and transports CO 2 Iron atom O 2 loaded in lungs Polypeptide chain Copyright © 2009 Pearson Education, Inc. O 2 unloaded in tissues Heme group O 2

The human fetus exchanges gases with the mother’s bloodstream ◦ A human fetus – Does not breathe with its lungs – Instead, it exchanges gases with maternal blood in the placenta ◦ In the placenta, capillaries of maternal blood and fetal blood run next to each other – The fetus and mother do not share the same blood Copyright © 2009 Pearson Education, Inc.

Placenta, containing maternal blood vessels and fetal capillaries Umbilical cord, containing fetal blood vessels Amniotic fluid Uterus