Chapter 23: The Respiratory System

Chapter 23:

The Respiratory System

Primary sources for figures and content:

Marieb, E. N. Human Anatomy & Physiology. 6th ed. San Francisco: Pearson Benjamin Cummings, 2004.

Martini, F. H. Fundamentals of Anatomy & Physiology. 6th ed. San Francisco: Pearson Benjamin Cummings,

2004.

The primary functions of

the respiratory system.

The Respiratory System

• Cells produce energy:– for maintenance, growth, defense,

and division– through mechanisms that use oxygen

and produce carbon dioxide

Oxygen

• Is obtained from the air by diffusion across delicate exchange surfaces of lungs

• Is carried to cells by the cardiovascular system which also returns carbon dioxide to the lungs

5 Functions of the Respiratory System

1. External respiration:- Provides extensive gas exchange surface area

between air and circulating blood2. Pulmonary ventilations

- Moves air to and from exchange surfaces of lungs3. Protects respiratory surfaces from outside environment

- dehydration, temperature changes, invasion by pathogens

4. Produces sounds for communication5. Provide olfactory sensation = Smell

Components of the Respiratory System

Figure 23–1

Organization of the Respiratory System

• The respiratory system is divided into the upper respiratory system, above the larynx, and the lower respiratory system, from the larynx down

Anatomy of Respiratory System

1. Upper Respiratory System– Function to warm and humidify air– Nose, nasal cavity, sinuses, pharynx

2. Lower Respiratory SystemA.Conduction portion

- Bring air to respiratory surfaces- Larynx, trachea, bronchi, bronchioles

B.Respiratory portion- Gas exchange- Alveoli

Alveoli

• Are air-filled pockets within the lungs– where all gas exchange takes place

The Respiratory Epithelium

Figure 23–2

Respiratory Mucosa = mucus membrane

• Lines conducting portion of respiratory system • Epithelial layer:

•pseudostratified columnar epithelium•Usually ciliated•Scattered goblet cells = mucin production

• Areolar layer = lamina propria (trachea, bronchi)•Areolar connective tissue•Mucus glands = mucin•Serous glands = lysozyme

• Glands produce ~1 quart mucus fluid/day• Cilia move mucus to pharynx to be swallowed

– Cilia beat slow in the cold

Alveolar Epithelium

• Is a very delicate, simple squamous epithelium

• Contains scattered and specialized cells

• Lines exchange surfaces of alveoli

The Respiratory Defense System

• Consists of a series of filtration mechanisms

• Removes particles and pathogens

Components of the Respiratory Defense System

1. Mucus– From goblet cells and glands in lamina propria,

traps foreign objects2. Cilia “mucus escalator”

– Move carpet of mucus with trapped debris out of the respiratory tract

3. Alveolar macrophages– Phagocytose particles that reach alveoli

4. Filtration in nasal cavity removes large particles

Disorders of theRespiratory Defense System

1. Cystic fibrosis– Cause Failure of mucus escalator– Result Produce thick mucus which blocks

airways and encourages bacteria growth

2. Smoking destroys cilia3. Inhalation of irritants chronic

inflammation cancer e.g. squamous cell carcinoma

The upper respiratory system and their

functions.

The Upper Respiratory System

Figure 23–3

1. Nose2. Nasal Cavity3. Pharynx

-Nasopharynx-Oropharynx-Laryngopharynx

1. The Nose

• Only external feature• Air enters the respiratory system:

– through external nares– into nasal vestibule

•Space in flexible part, lined with hairs to filter particles, leads to nasal cavity

•Nasal hairs in nasal vestibule are the first particle filtration system

1. The Nose

• Functions

1. Opening to airway for respiration2. Moisten and warm entering air3. Filter and clean inspired air4. Resonating chamber for speech5. Houses olfactory receptors

2. The Nasal Cavity

• The nasal septum:– divides nasal cavity into left and right

• Superior portion of nasal cavity is the olfactory epithelium provides sense of smell

• Nasal conchae (superior, middle, inferior) project into cavity on both sides– Nasal conchae cause air to swirl

1. Increase likelihood of trapping foreign material in mucus

2. Provide time for smell detection3. Provide time and contact to warm and humidify air

2. The Nasal Cavity

• Hard and soft palate form floor• Internal nares open to nasopharynx• Mucosa has large superficial blood supply

– Function warm, moisten air– Epistaxis = nose bleed

• Paranasal sinuses in frontal, sphenoid, ethmoid, and maxillary bones– Lined with respiratory mucosa– Connected to nasal cavity– Aid in warming/moistening air

• Hard palate:– forms floor of nasal cavity– separates nasal and oral cavities

• Soft palate:– extends posterior to hard palate– divides superior nasopharynx from lower

pharynx

• Air flow Nasal cavity opens into nasopharynx through internal nares

2. The Nasal Cavity

3. The Pharynx

• A chamber shared by digestive and respiratory systems

• Extends from internal nares to entrances to larynx and esophagus

• Three Parts:1. Nasopharynx2. Oropharynx3. Laryngopharynx

3. The Pharynx1. Nasopharynx = air only

- Posterior to nasal cavity- Pseudostratified columnar epithelium– Closed off by soft palate and uvula during swallowing– Pharyngeal tonsil located on posterior wall

• Inflammation can block airway– Auditory tubes open here

2. Oropharynx = food and air– Posterior to oral cavity– Stratified squamous epithelium– Palatine and lingual tonsils in mucosa

3. The Pharynx

3. Laryngopharynx = food and air- Lower portion- Stratified squamous epithelium- Continuous with esophagus

Why is the vascularization of the nasal cavity important?

A. It heats incoming air.

B. It moisturizes incoming air.

C. It nourishes nasal epithelial cells.

D. All of the above.

Why is the lining of the nasopharynx different from that of the oropharynx

and the laryngopharynx?

A. Nasopharynx lining is not subjected to food abrasion.

B. Nasopharynx lining must withstand temperature extremes.

C. Nasopharynx must be protected from drying out.

D. All of the above.

The lower respiratory system and their

functions.

Air Flow

• From the pharynx enters the larynx:– a cartilaginous structure that

surrounds the glottis

4. Larynx

Figure 23–4

4. Larynx = voice box

• Hyaline cartilage around glottis– Opening form laryngopharynx to trachea

• Functions of larynx1.Provide continuous airway2.Act as switch to route food and air properly3.Voice production

• Contains epiglottis– Elastic cartilage flap covers glottis during

swallowing

The Glottis

Figure 23–5


• Folds of epithelium over ligaments of elastic fibers create focal folds/cords

• Vocal cords project into glottis• Air passing through glottis vibrates folds

producing sound• Pitch Controlled by tensing/relaxing of the cords

•Tense + narrow = high pitch• Volume Controlled by the amount of air• Sound Production phonation


• Speech– Formation of sound using mouth and tongue

with resonance in pharynx, mouth, sinuses and nose

• Laryngitis– Inflammation of vocal folds– Cause infection or overuse that can

inhibit phonation

When the tension in your vocal folds increases, what happens to the pitch of

your voice?

A. It rises.

B. It falls.

C. Nothing happens.

D. It squeaks and cracks.

5. Trachea

Figure 23–6

The Trachea • Attached inferior to larynx• Walls composed of three layers

1. Mucosa•Pseudostratified columnar epithelium, goblet cells,

lamina propria, smooth muscle and glands

2. Submucosa•CT with additional mucus glands

3. Adventitia•CT with hyaline cartilage rings (15-20) keep airway

open, C-shaped•Opening toward the esophagus to allow expansion,

ends connected by trachealis muscle

6. Primary Bronchi

• Trachea branches into the Right and left primary bronchi

• Similar structure as trachea– No trachealis muscle

• Right = steeper angle• Enter lungs at groove (hilus)

– Along with blood and lymphatic

Hilus

• Where pulmonary nerves, blood vessels, and lymphatics enter lung

• Anchored in meshwork of connective tissue

Figure 23–7

Gross Anatomy of the Lungs

Right = 3 lobes

Left = 2 lobes

6. Primary Bronchi

• Lungs have lobes separated by deep fissures

• Inside lungs bronchi branch, get smaller in diameter– Branch ~23 times creating the bronchial tree

• As bronchi get smaller, structure changes1.Less cartilage in adventitia2.More smooth muscle in lamina propria3.Epithelium is thinner, less cilia, less mucus

Bronchitis

• Inflammation of bronchial walls:– causes constriction and breathing

difficulty

Relationship between Lungs and Heart

Figure 23–8

7. Terminal bronchiole

Figure 23–9

Smallest bronchi of Respiratory Tree

7. Terminal bronchiole • Smallest Bronchi• No cartilage• Last part of conduction portion• Trachea, Bronchi and Bronchioles innervated by ANS

to control airflow to the lungs– ANS Regulates smooth muscle:

•controls diameter of bronchioles•controls airflow and resistance in lungs

– Sympathetic bronchodilation– Parasympathetic bronchocontriction

•histamine release (allergic reactions)

Asthma

• Excessive stimulation and bronchoconstriction

• Activated by inflammatory chemicals (histamine)

• Stimulation severely restricts airflow• Epinephrine inhaler mimics

sympathetic ANS bronchodilation

7. Terminal bronchiole

• Each terminal bronchiole delivers air to one pulmonary lobule, separated by CT

• Inside lobule, terminal bronchiole branches into respiratory bronchioles– No cilia or mucus

• Each respiratory bronchiole connects to alveolar sac made up of many alveoli

Figure 23–10

The Bronchioles

Figure 23–11

8. Alveoli

8. Alveoli• Wrapped in capillaries• Held in place by elastic fibers• Three cell types

1. Type 1 cells = gas exchange•Simple squamous epithelium, lines inside

2. Type II cells = surfactant•Cuboidal epithelial cells produce surfactant

– Phospholipids + proteins– Prevent alveolar collapse, reduces surface tension

3. Alveolar macrophages = Phagocytosis•Phagocytosis of particles

8. Alveoli

• Alveoli connected to neighbors by alveolar pores– Equalize pressure

• Gas exchange occurs across the respiratory membrane (0.5µm thick)

• 3 Parts of the Respiratory Membrane 1.Squamous epithelial lining of alveolus2.Endothelial cells lining an adjacent capillary3.Fused basal laminae between alveolar and

endothelial cells

Respiratory Distress

• Difficult respiration:– due to alveolar collapse – caused when septal cells do not

produce enough surfactant

Disorders of the Alveoli

1. Pneumonia:– Inflammation of lungs from infection or injury– causes fluid to leak into alveoli– compromises function of respiratory

membrane prevents gas exchange

2. Pulmonary embolism– Block in branch of pulmonary artery– Reduce blood flow – Causes alveolar collapse

Figure 23–8

Gross Anatomy of Lungs

Gross Anatomy of Lungs• Concave base, rest on diaphragm• Right = 3 lobes• Left = 2 lobes (accommodates heart)• Housed in pleural cavity

– Cavity lined with parietal pleura– Lungs covered by visceral pleura

• Both pleura produce serous pleural fluid to reduce friction during expansion

• Pleurisy– Inflammation of pleura– Restrict movement of lungs breathing difficulty

Why are the cartilages that reinforce the trachea C-shaped?

A. To prevent tracheal crushing.

B. To conform to thoracic cavity shape.

C. To allow room for esophageal expansion.

D. To allow normal cardiac functioning.

What would happen to the alveoli if surfactant were not produced?

A. The alveoli would contract.

B. The alveoli would collapse.

C. The alveoli would expand.

D. The alveoli would pop.

What path does air take in flowing from the glottis to the respiratory

membrane?

A. larynx, trachea, bronchi, alveolar duct, alveolar sac, respiratory membrane

B. larynx, trachea, alveolar duct, bronchioles, respiratory membrane

C. trachea, bronchi, larynx, bronchioles, alveolar duct, alveolar sac,

D. larynx, trachea, bronchioles, alveolar duct, bronchi, alveolar sac, respiratory membrane

List the functions of the pleura. What does it secrete?

A. prevents cardiac friction; secretes mucus

B. prevents respiratory friction; secretes pleural fluid

C. protects lungs from drying out; secretes mucus

D. protects heart and thoracic cavity; secretes enzymes

Respiratory Physiology

Respiration

• External Respiration– Includes all processes involved in

exchanging O2 and CO2 with the environment

• Internal Respiration– Also called cellular respiration

– Involves the uptake of O2 and production of CO2 within individual cells

External Respiratory Physiology

• 3 steps of respiration1. Pulmonary ventilation = breathing2. Gas Diffusion/Exchange, across

membranes and capillaries3. Gas Transport to/from tissues– between alveolar capillaries– between capillary beds in other

tissues

1. Pulmonary Ventilation

• Movement of air into/out of alveoli• Visceral pleura adheres to parietal

pleura via surface tension– Altering size of pleural cavity will alter

size of lungs

• Pneumothorax– Injury of thoracic cavity– Air breaks surface tension lung recoil =

atelectasis, or collapsed lung


• Mechanics of breathing– Boyle’s law: gas pressure is inversely

proportional to volume•Defines the relationship between gas

pressure and volume: P = 1/V

– Air flows from area of high pressure to low pressure

Gas Pressure and Volume

Figure 23–13

Figure 23–14

Mechanisms of Pulmonary

Ventilation

Mechanisms of Pulmonary Ventilation

Diaphragm• Contraction of diaphragm pulls it toward abdomen

– Lung volume INCREASE– Air pressure DECREASE– Air flow ins

• Relaxation causes diaphragm to rise in dome shape– Lung volume DECREASE– Air pressure INCREASE– Air flows out

Rib cage movements can contribute– Superior = bigger, air in– Inferior = smaller, air out

Table 23–1

Common Methods of Reporting Gas Pressure

Pressure and Volume Changes with Inhalation and

Exhalation

Figure 23–15


Factors influencing pulmonary ventilation

1. Airway resistance– Diameter of bronchi– Obstructions

2. Alveolar surface tension– Surfactant (Type II cells) reduces alveoli surface

tension •Allow inflation

– Respiratory distress syndrome•Too little surfactant requires great force to

open alveoli to inhale


3. Compliance– Effort required to expand lungs and chest– High compliance = expand easily, normal– Low compliance = resist expansion– Compliance affected by

1. CT structure2. Alveolar Expandability3. Mobility of thoracic cage


3. Compliance affected by 1. CT structure

- Loss of elastin/replacement by fibrous tissue = Decrease compliance

- Emphysema - respiratory surface replaced by scars- Decrease elasticity = Decrease compliance- Loss of surface for gas exchange

2. Alveolar Expandability - Increase surface tension (decr. Surfactant) = decrease compliance - Fluid (edema) = decrease compliance


3. Compliance affected by 3. Mobility of thoracic cage

- less mobility = decrease compliance

Inspiration

• Inhalation involves contraction of muscles to increase thoracic volume

1. Quite breathing = eupnea– Diaphragm: moves 75% of air– External intercostals: elevate ribs, 25%more

2. Forced breathing = hyperpnea– Maximum rib elevation increases respiratory

volume 6x•Serratus anterior, pectoralis minor, scalenes,

sternocleidomastoid

Figure 23–16a, b

The Respiratory Muscles

Expiration

1. Eupnea– Passive, muscles relax, thoracic

volume decrease

2. Hyperpnea– Abdominal muscles (obliques,

transversus, rectus) contract forcing diaphragm up, thoracic volume further decrease

The Respiratory Muscles

Figure 23–16c, d

Respiratory Volumes and Capacities

Figure 23–17

4 Pulmonary/Respiratory Volumes

1. Resting tidal volume:– The amount of air inhaled or exhaled with each breath

under resting conditions2. Expiratory reserve volume (ERV):

– Amount of air that can be forcefully exhaled after a normal tidal volume exhalation

3. Residual volume:– Amount of air reaming in the lungs after a forced

exhalation4. Inspiratory reserve volume (IRV):

– Amount of air that can be forcefully inhaled after a normal tidal volume inhalation

4 Respiratory Capacities

1. Inspiratory capacity (IC): - Maximum amount of air that can be

inspired after a normal expiration- IC = Tidal volume + IRV

2. Functional residual capacity (FRC):- Volume of air remaining in the lungs after

a normal tidal volume expiration- FRC = ERV + RV

4 Respiratory Capacities

3. Vital capacity: - Maximum amount of air that can be

expired after a maximum inspiratory effort- VC = TV + IRV + ERV

4. Total lung capacity: - Maximum amount of air contained in lungs

after a maximum inspiratory effort- TLC = TV + IRV + ERV + RV

Respiratory Volumes and Capacities

• A breath = one respiratory cycle• Respiratory rate = breaths/min

– At rest ~18-20• Respiratory Minute Volume (RMV/MRV) =

respiratory rate X tidal volume, ~ 6 L• Not all air reaches alveoli, some air remains in

conduction portions = anatomic dead space– ~1ml/lb body weight

• Alveolar ventilation = air reaching alveoli/min– At rest ~ 4.2 L

• Both tidal volume and respiratory rate are adjusted to meet oxygen demands of body

Respiratory Minute Volume

• Amount of air moved per minute• Is calculated by:

respiratory rate tidal volume

• Measures pulmonary ventilation

Alveolar Ventilation

• Amount of air reaching alveoli each minute

• Calculated as:tidal volume — anatomic dead space

respiratory rate

In pneumonia, fluid accumulates in the alveoli of the lungs. How would this accumulation affect vital capacity?

A. increase vital capacity

B. decrease vital capacity

C. increase breathing rate, with no effect on vital capacity

D. decrease tidal volume, with no effect on vital capacity

2. Gas Exchange

Composition of Air

• Nitrogen (N2) about 79%

• Oxygen (O2) about 21%

• Water vapor (H2O) about 0.5%

• Carbon dioxide (CO2) about 0.04%

• Trace inert gasses• Partial pressure of gas =

concentration in air

2. Gas Exchange

• Depends on:1. Partial Pressures of the gases

•The pressure contributed by each gas in the atmosphere

•All partial pressures together add up to 760 mm Hg

– also known as Atmospheric Pressure 2.Gasses follow diffusion/concentration gradients to

diffuse into liquid•Rate depends on partial pressure and temperature

Henry’s Law

Figure 23–18

2. Gas Exchange

1. High Altitude Sickness

– Decrease PP O2 at high altitude decrease diffusion into blood

2. Decompression Sickness– PP of air gasses high underwater

– High amounts of N2 diffuses in blood

– If pressure suddenly decreases

•N2 leaves blood as gas causing bubbles damage & pain

– Hyperbaric chambers are used to treat

Efficiency of Gas Exchange/Diffusion at the Respiratory Membrane

• Due to:1. Substantial differences in partial

pressure across the respiratory membrane2.Distances involved in gas exchange are

small3. O2 and CO2 are lipid soluble

4. Total surface area for diffusion is large5.Coordination of blood and air flow

- Increase blood to alveoli with increase O2

Respiratory Processes and Partial Pressure

Figure 23–19

2. Gas Exchange

In Lungs

• PP O2

– High in alveoli and Low in capillary (blood)•Diffuse into capillaries

• PP CO2

– Low in alveoli and High in capillary (blood)•Diffuse into alveoli

In Tissues– Pressure and flow reversed

– O2 into tissues

– CO2 into capillary

3. Gas Transport

3. Gas TransportA. Transport of Oxygen

– 1.5% dissolved in plasma– Most bound to iron ions on heme of hemoglobin in erythrocytes

•4 O2/HB, ~280 million Hb/RBC = 1 million O2/RBC

– Hemoglobin saturation = % hemes bound to O2

•~97.5% at alveoli

•At high PP O2 hemoglobin binds O2

•At low PP O2 hemoglobin drops O2

– Carbon Monoxide Poisoning = CO out-

•Compete O2 for binding to Hb, even at low PP CO

•Causes suffocation (no O2)

Oxyhemoglobin Saturation Curve

Figure 23–20 (Navigator)

3. Gas TransportA. Transport of Oxygen

– Other factors that affect Hb saturation1.Bohr effect = Affect of pH

- Hb releases O2 in acidic pH

- High CO2 creates carbonic acid

2.Temperature- Hb releases O2 in high temperature

3.BPG (2,3 bisphosphoglycerate)- Produced by healthy RBC during glycolysis

- Increase BPG = Increase O2 release

4.Pregnancy- Fetal Hb = increase O2 binding

Figure 23–21

pH, Temperature, and Hemoglobin Saturation

The Bohr Effect• Caused by CO2:

– CO2 diffuses into RBC

– an enzyme, called carbonic anhydrase, catalyzes reaction with H2O

– produces carbonic acid (H2CO3)

• Carbonic acid (H2CO3):

– dissociates into hydrogen ion (H+) and bicarbonate ion (HCO3

—)

• Hydrogen ions diffuse out of RBC, lowering pH

Fetal and Adult Hemoglobin

Figure 23–22

Fetal and Adult Hemoglobin

• The structure of fetal hemoglobin:– differs from that of adult Hb

• At the same PO2:

– fetal Hb binds more O2 than adult Hb

– which allows fetus to take O2 from maternal blood

KEY CONCEPT

• Hemoglobin in RBCs:– carries most blood oxygen

– releases it in response to low O2 partial pressure in surrounding plasma

• If PO2 increases, hemoglobin binds oxygen

• If PO2 decreases, hemoglobin releases oxygen

• At a given PO2:

– hemoglobin will release additional oxygen

– if pH decreases or temperature increases

3. Gas Transport

A. Transport of Carbon Dioxide1. ~ 70% as Carbonic acid

- In RBCs and plasma- Carbonic anhydrase in RBCs catalyze reaction

with water

- CO2 + H2O H2CO3 H+ + HCO3-

- Reaction is reversed at lungs2. ~ 23% as carbaminohemoglobin

- CO2 bound to amino groups of Hb

3. ~ 7% dissolved in plasma as CO2

Carbon Dioxide Transport

Figure 23–23 (Navigator)

KEY CONCEPT

• CO2 travels in the bloodstream primarily as bicarbonate ions, which form through dissociation of carbonic acid produced by carbonic anhydrase in RBCs

• Lesser amounts of CO2 are bound to Hb or dissolved in plasma

Summary: Gas Transport

Figure 23–24

As you exercise, hemoglobin releases more oxygen to your active skeletal

muscles than it does when the muscles are at rest. Why?

A. Oxygen is released more readily at higher temperatures.

B. Oxygen is released more readily at higher pH.

C. Oxygen is released more readily at lower temperatures.

D. B and C are correct.

How would blockage of the trachea affect the blood pH?

A. increase blood pH

B. decrease blood pH

C. rapid fluctuations

D. no effect

Regulation of Respiration

Respiratory Centers and Reflex Controls

Figure 23–26


• Respiratory homeostasis requires that– Diffusion rates at peripheral

capillaries (O2 in, CO2 out) and alveoli (CO2 out, O2 in) must match

• Regulation1.Autoregulation2.Neural Regulation


1. AutoregulationA. Lung perfusion

- Blood flow is lungs is redirected to alveoli with high partial pressure of O2

B. Alveolar ventilation- Alveoli with high partial pressure of

CO2 receive increased air flow

Regulation of Respiration2. Neural Regulation

A. Respiratory Rhythmicity Centers- Located in the medulla oblongata- Control the basic pace and depth of respiration1. DRG (Dorsal Respiratory Group)

- Controls diaphragm and external intercostal muscles on the every breath

- Serves as the pacesetting respiratory center- Active for 2 sec, inactive for 3 sec

2. VRG (Ventral Respiratory Group)- Controls accessory muscles during forced breathing

Figure 23–25a

Quiet Breathing

Regulation of Respiration 2. Neural Regulation

B. Respiratory Centers- Located in the pons- Influence and modify activity of the DRG and VRG

- to fine tune breathing rhythm - prevent lung over-inflation

- Monitor input from sensory receptors to trigger- appropriate reflex alter respiratory rate and depth of respiration to

satisfy gas exchange needs

1. Apneustic Center- Stimulates the DRG for inhalation

- Helps increase intensity of inhalation- Responds to lung inflation signals from sensory receptors

Regulation of Respiration 2. Neural Regulation

B. Respiratory Centers2. Pneumotaxic Center

- Inhibits the apneustic center to allow exhalation- Modifies the pace set by DRG and VRG- Increased signaling

- increase respiratory rate by decreasing duration of inhalation

- Decreased signaling - decrease respiratory rate but increase depth by

allowing apneustic center to signal DRG for greater inhalation


2. Neural RegulationC. Respiratory Reflexes

- Respiratory centers modify activity based on input from receptors

1. Chemoreceptors: - monitor CO2, O2, and pH in blood and CSF

2. Baroreceptors: - monitor blood pressure in aorta and carotid artery

3. Stretch receptors: - monitor inflation of the lungs (Hering-Breuer

Reflex)


2. Neural RegulationC. Respiratory Reflexes

4. Pulmonary irritant receptors: - monitor particle sin respiratory tracts

and trigger cough or sneeze5. Other:

- pain, temperature, and visceral sensations can trigger respiratory reflexes

The Hering–Breuer Reflexes

• 2 baroreceptor reflexes involved in forced breathing:– inflation reflex:

• prevents overexpansion of lungs

– deflation reflex:• inhibits expiratory centers• stimulates inspiratory centers during lung

deflation

KEY CONCEPT

• A basic pace of respiration is established between respiratory centers in the pons and medulla oblongata, and modified in response to input from:– chemoreceptors– baroreceptors– stretch receptors

• In general, CO2 levels, rather than O2 levels, are primary drivers of respiratory activity

3 Effects of Aging on the Respiratory System

1. Elastic tissues deteriorate:– reducing lung compliance– lowering vital capacity

2. Arthritic changes in rib cage:– Decrease mobility of chest movements– decrease respiratory minute volume

3. Emphysema:– Decrease gas exchange– Higher risk if exposed to respiratory

irritants (e.g., cigarette smoke, dusty jobs)

Respiratory Performance and Age

Figure 23–28

What effect would exciting the pneumotaxic centers have on

respiration?

A. shorter breaths

B. rapid breathing rate

C. no effect

D. A and B

Are peripheral chemoreceptors as sensitive to levels of carbon dioxide as

they are to levels of oxygen?

A. Yes.

B. No, they are more sensitive to oxygen levels.

C. No, they are more sensitive to carbon dioxide levels.

D. The sensitivities can not be compared.

Johnny is angry with his mother, so he tells her that he will hold his breath until he turns blue and dies. Should

Johnny’s mother worry?

A. Yes

B. No

SUMMARY• 5 functions of the respiratory system:

– gas exchange between air and circulating blood– moving air to and from exchange surfaces– protection of respiratory surfaces– sound production– facilitating olfaction

• Structures and functions of the respiratory tract:– alveoli– respiratory mucosa– lamina propria– respiratory defense system

• Structures and functions of the upper respiratory system:– the nose and nasal cavity– the pharynx

• Structures and functions of the larynx:– cartilages and ligaments– sound production– the laryngeal musculature

SUMMARY• Structures and functions of the trachea and primary bronchi• Structures and functions of the lungs:

– lobes and surfaces– the bronchi– the bronchioles– alveoli and alveolar ducts– blood supply to the lungs– pleural cavities and membranes

• Respiratory physiology:– external respiration– internal respiration

• Pulmonary ventilation:– air movement– pressure changes– the mechanics of breathing– respiratory rates and volumes

• Gas exchange:– the gas laws– diffusion and respiration

SUMMARY

• Gas pickup and delivery:– partial pressure– oxygen transport (RBCs and hemoglobin)– carbon dioxide transport

• Control of respiration:– local regulation (lung perfusion, alveolar ventilation)– respiratory centers of the brain– respiratory reflexes– voluntary control of respiration

• Aging and the respiratory system

Documents

Chapter 23: The Respiratory System