Chapter 33 Respiration Chapter 33 Opener These students say they will quit smoking later. Only about one in three will succeed.

Chapter 33 Outline 33.1 Why Exchange Gases? 33.2 What Are Some Evolutionary Adaptations for Gas Exchange? 33.3 How Does the Human Respiratory System Work?

Section 33.1 Outline 33.1 Why Exchange Gases?  Gas exchange supports cellular respiration Gas exchange in vertebrates O2 is inhaled into lungs, deposited in blood, and transported to body cells O2 is used in cellular respiration to convert the energy in nutrients into ATP, generating CO2 as a waste product Blood transports CO2 from tissues to lungs CO2 released from lungs during exhalation

Section 33.2 Outline 33.2 What Are Some Evolutionary Adaptations for Gas Exchange? Some Animals in Moist Environments Lack Specialized Respiratory Structures Respiratory Systems Facilitate Gas Exchange by Diffusion Terrestrial Animals Have Internal Respiratory Structures

Common Respiratory Features All animal respiratory systems share three features (1) Respiratory surface must be moist so gases can diffuse across cell membranes (2) Cells lining respiratory surface are thin to optimizes gas diffusion (3) The respiratory surface area must be large to allow for adequate gas exchange

Animals in Moist Environments Some animals in moist environments lack specialized respiratory structures Gases diffuse short distances in smaller animals to reach cells Gas exchange optimized by long, flat bodies with greater surface area Examples: flatworms

Animals in Moist Environments Low energy demands translate into larger animals that rely on their moist body surface for gas exchange Larger size possible because less O2 needed by cells Example: sea jellies

Animals in Moist Environments Some animals bring the environment close to all their cells Allows greater exposure of cells to O2 Example: sponges

Animals in Moist Environments Other animals combine large skin surface area with well-developed circulation for delivery to cells Skin has many capillaries that carry O2 to internal body tissues This arrangement sustains a favorable O2 concentration gradient between skin and blood Example: earthworm

Gas Exchange Respiratory systems facilitate more effective exchange of gases between the environment and an animal’s body Respiratory systems alternate bulk flow of air/water and diffusion of gases Bulk Flow: describes when fluids or gases move through spaces from high pressure to low pressure

Gas Exchange In mammals Air or water moves past respiratory surface by bulk flow (down pressure gradient) O2 and CO2 are exchanged by diffusion Gases transported to/from tissues by bulk flow Gases exchanged with tissues (cells) by diffusion

Gas Exchange in Water Gills are external projections of the body that exchange gases Most commonly used in aquatic animals Can be elaborately folded to maximize their surface area Have many capillaries to bring blood to body surface for gas exchange

Gas Exchange in Water Fish gills are complex structures Protected by a bony flap (operculum) Fish controls water flow over gills by swimming with mouth open Water flows over gills and out of body through opercular openings Gills are elaborately folded, and cannot support themselves out of water

Internal Respiratory Structures Internal respiratory structures are used by most terrestrial animals to help keep respiratory surfaces moist Gas exchange is optimized across moist surfaces Two common terrestrial respiratory structures Tracheae (insects) Lungs (most terrestrial vertebrates)

Tracheae Tracheae are elaborately branched internal tubes that deliver air to body cells Used by insects Branch into smaller tubes (tracheoles) Air enters tracheae though abdominal openings (spiracles) Some insects use abdominal contractions to enhance air movements

Lungs Lungs are internal chambers containing moist respiratory surfaces Used by most terrestrial vertebrates Developed to allow ancestral fish to survive in stagnant, O2-poor water

Lungs Lungs have differing levels of complexity In amphibians Many use gills as larvae and simple, sac-like lungs as more terrestrial adults Many use the skin as a supplemental respiratory surface Example: tadpoles and a bullfrog

Lungs In reptiles Scales reduce body water loss and allow for survival in dry environments Scales reduce gas exchange through skin Lungs have more respiratory surface area than amphibians Example: a mangrove snake

Lungs In birds Exclusively lung breathers Extremely efficient lungs accommodate O2 demands during flight Air flows through lungs during inhalation and exhalation due to coordination of air sac activity Bird lungs filled with thin walled tubes (parabronchi)

Section 33.3 Outline 33.3 How Does the Human Respiratory System Work? The Conducting Portion of the Respiratory System Carries Air to the Lungs Gas Exchange Occurs in the Alveoli Oxygen and Carbon Dioxide Are Transported Using Different Mechanisms Air Is Inhaled Actively and Exhaled Passively Breathing Rate Is Controlled by the Respiratory Center of the Brain

The Human Respiratory System The human respiratory system can be divided into two parts The conducting portion The gas-exchange portion

The Conducting Portion The conducting portion is a series of passageways that carry air into the gas-exchange portion of the lungs Warms and moistens air on way to lungs Debris in air sticks to mucus that lines respiratory passages Mucus carried to pharynx by cilia lining respiratory passages

The Conducting Portion Nose and mouth Nasal cavity and oral cavity Pharynx(인두): chamber where nasal and oral cavities converge

The Conducting Portion Larynx: opening called the “voice box” Contain vocal cords: bands of elastic tissue controlled by muscles; vibrate as exhaled air passes over them

The Conducting Portion Larynx covered by epiglottis: flap of tissue that prevents food from entering larynx when swallowing If food lodges in larynx, choking can occur Heimlich maneuver can dislodge food

Heimlich maneuver FIGURE 33-8 The Heimlich maneuver can save lives If a person is choking and unable to breathe, use the Heimlich maneuver to push upward on the victim's diaphragm, forcing air out of the lungs and often dislodging the object. Repeat if necessary.

The Conducting Portion Trachea: flexible tube reinforced with cartilage Bronchi: splitting of trachea into two branches; each leading to a lung

The Conducting Portion Bronchioles: repeated branchings of bronchi Lined with smooth muscle that can constrict or dilate passageway

The Gas Exchange Portion Where gases are exchanged with the blood Occurs in the alveoli in the lungs Alveoli: tiny air sacs where gas exchange occurs 300 million alveoli in both lungs Arranged in grape-like clusters Surrounded by dense capillary networks

The Gas Exchange Portion Alveoli in lungs are well adapted for gas exchange Extensive collective surface area Are enmeshed in capillaries Made of a single thin layer of endothelial cells that form the innermost portion of the respiratory membrane, across which gas exchange occurs

The Gas Exchange Portion The respiratory membrane Consists of the alveolar epithelium and the layer of endothelial cells that forms the innermost wall of each capillary The alveolar and capillary walls are only one cell thick, minimizing diffusion distance for gases between the blood and the air

The Gas Exchange Portion O2 diffuses from lung air into blood O2 in freshly inhaled air has higher O2 concentration than O2-poor blood O2 diffuses down concentration gradient into capillary blood Oxygenated blood transported to heart, then the rest of body

The Gas Exchange Portion CO2 diffuses from lung blood into alveoli Metabolically active tissues release CO2 into blood, which transports it to alveolar capillaries Alveolar capillaries have a higher CO2 concentration than that of alveolar air CO2 diffuses down concentration gradient into alveolar air, which is then exhaled

The Gas Exchange Portion Surfactant Oily secretion lining alveolar walls Reduces surface tension of alveolar walls, preventing collapse during exhalation

Oxygen Transport O2 binds reversibly to hemoglobin molecules in red blood cells Hemoglobin: iron-containing protein that can bind to four O2 molecules When bound to O2: cherry-red color When not bound to O2: maroon-red color

Carbon Dioxide Transport CO2 is transported in the blood in three ways (1) As bicarbonate ions (2) Bound to hemoglobin (3) Dissolved in plasma as CO2

Carbon Dioxide Transport CO2 transport as bicarbonate ions (HCO3-) 70% of CO2 reacts with water to form HCO3-, which is then transported in the plasma CO2 transported bound to hemoglobin 20% of CO2 binds to and is carried by hemoglobin CO2 transported dissolved in plasma 10% of CO2 is transported this way

Inhalation and Exhalation Breathing occurs due to volume changes in the airtight chest cavity Located within rib cage Bottom of chest cavity defined by dome-shaped diaphragm muscle

Inhalation and Exhalation Breathing occurs in two stages Inhalation Exhalation Air is inhaled actively and exhaled passively

Inhalation and Exhalation Inhalation: when air is drawn into lungs Chest cavity enlarges when diaphragm and rib muscles contract Lungs expand with chest cavity, creating a partial vacuum that draws air into lungs

Inhalation and Exhalation Exhalation: when air is passively expelled out of lungs Chest cavity size decreases when diaphragm and rib muscles relax Decreasing chest cavity size forces air out of lungs Additional air can be expelled by actively contracting the abdominal muscles

The Respiratory Center The respiratory center is a cluster of nerve cells located in the medulla(연수) of the brain Generate cyclic bursts of impulses that cause contraction of respiratory muscles Sets baseline breathing rate

The Respiratory Center Breathing rate can be modified by Blood CO2 levels Blood O2 levels Activity levels

The Respiratory Center Breathing rate can be modified by blood CO2 levels Chemoreceptors in medulla detect elevated CO2 levels and stimulate the respiratory center Respiratory center causes an increase in breathing rate and depth

The Respiratory Center Breathing rate can be modified by blood O2 levels Chemoreceptors in aorta and carotid arteries detect drastically low O2 levels and stimulate the respiratory center Respiratory center causes an increase in breathing rate and depth Little influence on normal breathing

The Respiratory Center Breathing rate can be modified by physical activity During exercise, higher brain centers activate muscles and stimulate the respiratory center Causes increased breathing rate and depth Occurs in advance of significant changes in blood CO2 and O2 concentrations