1 Chapter 14 Lecture and Animation Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. To run the animations.

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Chapter 14Lecture and

Animation Outline

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Respiratory System Overview

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14.1 The Respiratory System

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A. Introduction

1. Major function is gas exchange2. Works with the cardiovascular system to

accomplish:a. Pulmonary ventilationb. External respirationc. Internal respirationd. Transport of gases

3. Reason for the respiratory events – provide oxygen for cellular respiration and remove carbon dioxide waste from cellular respiration

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The respiratory tract

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B. The respiratory tract

1. Introductiona. Nasal hairs, cilia, and mucus cleanse

inhaled air1) Lysozyme in the mucus helps to kill

bacteria2) Mucociliary escalator

b. Inhaled air is warmed by superficial blood vessels lining the airways

c. Air is moistened by the mucous membrane

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2. The nose

a. The only external portion of the respiratory system

b. Air enters through the nostrilsc. Contains two nasal cavities

1) Lined by a mucous membrane2) Nasal conchae increase the surface area

for moistening and warming inhaled air3) Odor receptors located in the olfactory

epithelium

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The nose, cont

1. Tears empty into the nasal cavities by way of the nasolacrimal canals

2. Paranasal sinuses connect to the nasal cavities and act as resonating chambers for speech

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The path of air

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3. The pharynx (throat)

a. Connects the nasal and oral cavities to the larynx

b. Three parts:1) Nasopharynx2) Oropharynx3) Laryngopharynx

c. Tonsils provide the primary lymphatic tissue defense for breathing

d. Passageway for both food and air

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4. The larynx (voicebox)

a. Cartilaginous passageway for air between the pharynx and trachea

b. Houses the vocal cords1) Mucosal folds that vibrate as air is

expelled2) Pitch regulated by the tension on the

vocal cords and opening of glottis3) Loudness depends on the amplitude of

the vibrationsc. Thyroid cartilage – Adam’s appled. The epiglottis prevents food from entering

the larynx

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Anatomy of the larynx

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5. The trachea (windpipe)

a. Connects the larynx to the primary bronchib. Ventral to esophagusc. C-shaped cartilaginous rings

1) Creates a patent airway2) Allows for expansion of the esophagus

d. Mucosal lining has pseudostratified ciliated columnar epithelium that forms the mucociliary escalator

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Pseudostratified ciliated columnar epithelium

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6. The bronchial tree

a. The trachea divides into the right and left primary bronchi to enter the lungs

b. The primary bronchi branch into secondary bronchi1) Three for the right lung2) Two for the left lung

c. The secondary bronchi divide into tertiary bronchi

d. Bronchioles are the smallest conducting airways; no cartilage

e. Each bronchiole leads to air sacs called alveoli

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C. The lungs

1. Lung structurea. Paired, cone-shaped organsb. Each lobe is divided into lobulesc. Each lobule has a bronchiole and

pulmonary arteries that serves many alveoli

d. Elastic connective tissue helps with lung recoil when a person exhales

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1. Pleura

a. Double layered serous membrane1) The visceral pleura adheres to the

surface of the lung2) The parietal pleura lines the inside of the

thoracic cavityb. Produces a lubricating serous fluid that also

creates surface tension between the layers

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3. The alveoli

a. Alveolar sacs are made up of simple squamous epithelium surrounded by blood capillaries

b. Site of gas exchangec. Alveoli must stay open to receive inhaled air

1) Surfactant lowers the surface tension of water lining the alveoli preventing them from collapsing completely

2) Respiratory distress syndrome occurs in premature infants who lack surfactant

d. Also contain dust cells, macrophages to defend against inhaled debris and pathogens

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Gas exchange in the lungs

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4. The respiratory membrane

a. Facilitates rapid gas exchangeb. Composed of juxtaposed alveolar epithelium

and the capillary epitheliumc. Extremely thind. Large surface area (50-70m2)

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Alveolus and respiratory membrane

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14.2 Mechanism of breathing

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A. Ventilation

1. Introductiona. The manner in which air enters and exits

the lungsb. Conditions to consider:

1) The lungs lie within the sealed-off thoracic cavity

2) The lungs adhere to the thoracic cavity wall by way of the pleurae; creates intrapleural pressure

3) A continuous column of air extends from the pharynx to the alveoli of the lungs

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2. Inspiration

a. Active phase of ventilationb. Diaphragm contracts and flattensc. External intercostal muscles contract, and the

rib cage moves upward and outwardd. Thoracic cavity volume increases, causing the

lungs to increase in volumee. Air pressure within the alveoli

(intrapulmonary pressure) decreasesf. Air flows from an area of higher pressure

(atmospheric pressure) to an area of lower pressure (within the lungs) until pressures are equal

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Inspiration

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3. Expiration

a. Usually the passive phase of ventilationb. The diaphragm relaxes and resumes its

dome shapec. The intercostal muscles relax and the rib

cage moves down and ind. The volume of the thoracic cavity decreases

and the lungs recoile. Lung volume decreases and the

intrapulmonary pressure increasesf. Since intrapulmonary pressure is now

greater than atmospheric pressure, air will flow out of the lungs until pressure are equal

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Expiration

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4. Maximum inspiratory effort

a. Involves the accessory muscles of respiration1) Erector spinae2) Pectoralis minor3) Scalene and sternocleidomastoid muscles

b. Help increase the size of the thoracic cavity larger than normal

c. Allows more air to be inspired

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1. Forced expiration

a. During heavy exercise, singing, etc.b. Involves contraction of abdominal wall

muscles and the internal intercostal muscles

c. Increased pressure in the thoracic cavity will expel more air

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Alveolar Pressure Changes


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Mechanism of Breathing, cont

6. Spirometer – instrument that records the volume of air exchanged during breathing

7. Spirogram – shows the measurements recorded by a spirometer

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B. Respiratory volumes

1. Tidal volumea. Normal, relaxed breathingb. About 500 mL

2. Vital capacitya. Maximum volume of air that can be inhaled plus

the maximum volume of air that can be exhaledb. Depends on:

1) Inspiratory reserve volumea) Forced inspirationb) Increases the volume of air beyond the

tidal volume by 2,900 mL2) Expiratory reserve volume

a) Forced expirationb) 1,400 mL

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Respiratory volumes, cont

3. Residual volumea. Amount of air remaining in the lungs

after a forced expirationb. About 1,000 mL

4. Dead air space – 30% of the inspired air that does not reach the alveoli for exchange but remains in the passageways

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Respiratory volumes

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C. Control of ventilation

1. Controlled by a primary respiratory center in the medulla oblongataa. The phrenic nerve carries impulses to the

diaphragmb. The intercostal nerves stimulate the

external intercostal musclesc. Normal breathing rhythm also requires

input from the pons

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Nervous control of breathing

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2. Nervous input

a. Can influence depth and rate of breathingb. Cerebral cortex, limbic system,

hypothalamus, and other brain centersc. Hering-Breuer reflex – prevents over-

inflation of the lungs

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1. Chemical input

a. The respiratory center is sensitive to the levels of CO2 and H+

b. Chemoreceptors in the carotid and aortic bodies are sensitive to the level of oxygen in the blood

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14.3 Gas exchange and transport

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A. External respiration

1. Exchange of gases in the lungs between the air in the alveoli and the blood in the pulmonary capillaries

2. Oxygena. Higher concentration in the alveolib. Diffuses from the alveoli into the blood

3. Carbon dioxidea. Higher concentration in the bloodb. Diffuses from the blood in the pulmonary

capillaries to the alveoli4. Partial pressure

a. Amount of pressure exerted by each gas b. Symbolized as PO2 and PCO2

c. Alveolar PO2 is higher than in the blood d. Blood PCO2 is higher than in the alveoli

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B. Internal respiration

1. Exchange of gases in the tissues between the blood in systemic capillaries and tissue fluids

2. Oxygena. Higher concentration in the bloodb. Diffuses from the blood into the tissue fluidc. PO2 of the blood is higher than in tissue fluid

3. Carbon dioxidea. Higher concentration in the tissue fluidb. Diffuses from the tissue fluid into the bloodc. PCO2 is higher in the tissue fluid than in the blood

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External & internal respiration

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Gas Exchange During Respiration


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C. Gas transport

1. Oxygen Transporta. 97-98% transported by hemoglobin in the

red blood cells1) Combined with oxygen –

oxyhemoglobin2) Released oxygen – deoxyhemoglobin

b. Small amount (2-3%) transported in the plasma

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2. Carbon dioxide transport

a. As a dissolved gas in blood plasma and in the cytoplasm of red blood cells – 10%

b. Combined with globin portion of hemoglobin – carbaminohemoglobin – 30%

c. Most is carried as bicarbonate ions – 60%1) Carbon dioxide combines with water to form

carbonic acid in the RBC2) Carbonic acid dissociates into hydrogen ions

and bicarbonate ions3) Excess H+ combines with the globin portion of

hemoglobin (reduced hemoglobin)4) Bicarbonate ions diffuse out of red blood cells

into the plasma in exchange for chloride ions – chloride shift

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3. pH

a. The respiratory system helps regulate pHb. Bicarbonate/Carbonic acid buffer system is

altered by breathing1) Hypoventilation = increased CO2 =

decreased pH = acidosis (pH less than 7.35)

2) Hyperventilation = decreased CO2 = increased pH = alkalosis (pH greater than 7.45)

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14.4 Respiration and health

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A. Upper respiratory tract infections

1. Can spread from the nasal cavities to the sinuses, middle ears, and larynx

2. Viral infections can lead to secondary bacterial infections

3. Strep throata. Primary bacterial infectionb. Caused by streptococcus pyogenesc. Can lead to a generalized upper

respiratory infection

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4. Sinusitis

a. Infection of the cranial sinusesb. Develops when nasal congestion blocks

openings to the sinusesc. Symptoms include:

1) Postnasal discharge2) Facial pain

d. Treatment depends on restoring proper drainage of the sinuses

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5. Otitis media

a. Bacterial infection of the middle earb. Often a complication seen in children who

have a nasal infectionc. Pain is the primary symptomd. Other symptoms include:

1) Sense of fullness2) Hearing loss3) Vertigo 4) Fever

e. Treatment is antibiotics and/or placement of tympanostomy tubes to drain fluid

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URIs, cont

6. Tonsillitisa. Tonsils become inflamed and enlargedb. Tonsillectomy – surgical removal of

tonsils7. Laryngitis

a. Inflammation of the larynxb. Hoarseness leads to the inability to talk

in an audible voicec. Causes by an upper respiratory infection

or overuse

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B. Lower respiratory tract disorders

1. Lower Respiratory Infectionsa. Bronchitis

1) Bacterial infection of the primary and secondary bronchi

2) Usually preceded by a viral URIb. Pneumonia

1) Viral or bacterial infection of the lungs2) Bronchi and alveoli fill with thick fluid3) Risk factors include:

a) Advanced ageb) Weakened immune systemc) Smoking and being immobilized

4) May be localized in specific lobules of the lungs

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Lower respiratory infections, cont

c. Pulmonary tuberculosis1) Caused by the tubercle bacillus bacterium2) Lung tissue develops tubercles around the

invading pathogens3) Tuberculosis skin test can detect if a

person has ever been exposed to the bacteria

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Common bronchial & pulmonary diseases

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2. Restrictive pulmonary disorders

a. Vital capacity is reducedb. Lungs have lost their elasticityc. Pulmonary fibrosis

1) Fibrous connective tissue buildup in the lungs

2) Can be caused by inhaling silica, coal dust, asbestos, clay, cement, flour, fiberglass

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3. Obstructive pulmonary disorders

a. Air does not flow freely in the airwaysb. Maximal inhalation or exhalation time is

greatly increasedc. COPD – chronic obstructive pulmonary

disease1) Develop slowly, over a long period of

time2) Recurrent

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COPDs, cont

3) Chronic bronchitisa) Airways are inflamed and filled with

mucusb) Bronchi have undergone degenerative

changesc) Causes – smoking and long-term

exposure to pollutants

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4) Emphysema

a) Incurable disorderb) Alveoli are distended and walls are

damaged and the surface area available for gas exchange is reduced

c) Often preceded by chronic bronchitisd) Lungs have lost their elasticitye) Exhaling is difficult and residual volume

increasesf) Less oxygen reaches the heart and braing) Surgical treatment of lung volume

reduction and lung transplant

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d. Asthma

1) Acute obstructive disorder 2) Disease of the bronchi and bronchioles3) Marked by:

a) Wheezingb) Breathlessnessc) Sometimes a cough and expectoration of

mucus4) Airways are sensitive to irritants5) Is not curable, but treatable with inhalers to

control inflammation and stop muscle spasms

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4. Lung cancer

a. Linked to smokingb. Progressive steps in the development of

lung cancer:1) Thickening and callusing of the cells lining

the primary bronchi2) Cells with atypical nuclei appear in the

callused lining3) Cells break loose and penetrate other

tissues (metastasis)c. Pneumonectomy – surgical removal of a

lobe of a lung or removal of the entire lung

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Normal lungs vs. diseased lungs

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14.5 Effects of aging

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A. Effects of Aging

1. Respiratory fitness decreases with age2. Maximum breathing capacities decline3. Gas exchange in the lungs becomes less

efficient4. Respiratory membrane thickens5. Ciliated cells of the trachea decline in

number6. Respiratory diseases are more common

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14.6 Homeostasis

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A. Gas exchange

1. Oxygen is needed by cells for cellular respiration

2. Carbon dioxide is a waste product of cellular respiration

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1. Regulation of pH

1. Altering blood CO2 levels

2. Increased CO2, increases H+, and decreases pH (acidosis)

3. Decreased CO2, decreased H+, and increases pH (alkalosis)

4. Hypoventilation – build-up CO2

5. Hyperventilation – too much CO2 leaving

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1. Control of blood pressure

1. Assists in the renin-angiotensin-aldosterone pathway

2. The lungs contain ACE (angiotensin converting enzyme) that converts angiotensin I into angiotensin II

3. Angiotensin II is a vasoconstrictor that raises blood pressure

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1. Defense

1. Part of the 1st line of defense2. Mucus and cilia capture and remove

pathogens3. Assists immunity through the tonsils and

alveolar dust cells

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Human systems work together

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