Tortora & Grabowski 9/e 2000 JWS 23-1 BIOLOGY 252 Human Anatomy & Physiology Chapter 23 The Respiratory System: Lecture Notes

Tortora & Grabowski 9/e 2000 JWS 23-1

BIOLOGY 252

Human Anatomy & Physiology

Chapter 23

The Respiratory System:

Lecture Notes

The Respiratory System

• Cells continually use O2 & release CO2

• Respiratory system designed for gas exchange

• Cardiovascular system transports gases in blood

• Failure of either system– rapid cell death from

O2 starvation

Respiratory System Anatomy

• Nose• Pharynx = throat• Larynx = voicebox• Trachea = windpipe• Bronchi = airways• Lungs• Locations of infections

– upper respiratory tract is above vocal cords

– lower respiratory tract is below vocal cords

Nose - Internal Structures

• Large chamber within the skull• Roof is made up of ethmoid and floor is hard palate• Internal nares (choanae) are openings to pharynx• Nasal septum is composed of bone & cartilage• Bony swelling or conchae on lateral walls

Functions of the Nasal Structures

• Olfactory epithelium for sense of smell• Pseudostratified ciliated columnar with goblet cells

lines nasal cavity– warms air due to high vascularity– mucous moistens air & traps dust– cilia move mucous towards pharynx

• Paranasal sinuses open into nasal cavity– found in ethmoid, sphenoid, frontal & maxillary– lighten skull & resonate voice

Pharynx • Muscular tube (5 inch long) hanging from skull

– skeletal muscle & mucous membrane• Extends from internal nares to cricoid cartilage• Functions

– passageway for food and air– resonating chamber for speech production– tonsil (lymphatic tissue) in the walls protects

entryway into body• Distinct regions -- nasopharynx, oropharynx and

laryngopharynx

Cartilages of the Larynx

• Thyroid cartilage forms Adam’s apple• Epiglottis---leaf-shaped piece of elastic cartilage

– during swallowing, larynx moves upward– epiglottis bends to cover glottis

• Cricoid cartilage---ring of cartilage attached to top of trachea

• Pair of arytenoid cartilages sit upon cricoid– many muscles responsible for their movement– partially buried in vocal folds (true vocal cords)

Larynx

• Cartilage & connective tissue tube• Anterior to C4 to C6• Constructed of 3 single & 3 paired cartilages

Vocal Cords

• False vocal cords (ventricular folds) found above vocal folds (true vocal cords)

• True vocal cords attach to arytenoid cartilages

Trachea• Size is 12 cm (5 in) long & 1in diameter• Extends from larynx to T5 anterior to the esophagus and

then splits into bronchi• Layers

– mucosa = pseudostratified columnar with cilia & goblet

– submucosa = loose connective tissue & seromucous glands

– hyaline cartilage = 16 to 20 incomplete rings • open side facing esophagus contains trachealis m.

(smooth)• internal ridge on last ring called carina

– adventitia binds it to other organs

Trachea and Bronchial Tree

• Full extent of airways is visible starting at the larynx and trachea

Histology of the Trachea

• Ciliated pseudostratified columnar epithelium • Hyaline cartilage as C-shaped structure closed by trachealis

muscle

Airway Epithelium

• Ciliated pseudostratified columnar epithelium with goblet

cells produce a moving mass of mucus.


Tracheostomy and IntubationTracheotomy, syn. = Tracheostomy

• Reestablishing airflow past an airway obstruction– crushing injury to larynx or chest– swelling that closes airway– vomit or foreign object

• Tracheostomy is incision in trachea below cricoid cartilage if larynx is obstructed

• Intubation is passing a tube from mouth or nose through larynx and trachea

Bronchi and Bronchioles

• Primary bronchi supply each lung• Secondary bronchi supply each lobe of the lungs (3 right + 2 left)• Tertiary bronchi supply each bronchopulmonary segment• Repeated branchings called bronchioles form a bronchial tree


• Tidal volume = amount air moved during quiet breathing• MVR= minute ventilation is amount of air moved in a minute• Reserve volumes ---- amount you can breathe either in or out above that amount

of tidal volume• Residual volume = 1200 mL permanently trapped air in system• Vital capacity & total lung capacity are sums of the other volumes

Lung Volumes and Capacities

Structures within a Lobule of Lung

• Branchings of single arteriole, venule & bronchiole are wrapped by elastic CT

• Respiratory bronchiole– simple squamous

• Alveolar ducts surrounded by alveolar sacs & alveoli– sac is 2 or more alveoli sharing

a common opening

Photomicrograph of lung tissue showing bronchioles, alveoli and alveolar ducts.

Histology of Lung Tissue

Cells Types of the Alveoli

• Type I alveolar cells– simple squamous cells where gas exchange

occurs

• Type II alveolar cells (septal cells)– free surface has microvilli– secrete alveolar fluid containing surfactant

• Alveolar dust cells– wandering macrophages remove debris

Alveolar-Capillary Membrane

• Respiratory membrane = 1/2 micron thick• Exchange of gas from alveoli to blood• 4 Layers of membrane to cross

– alveolar epithelial wall of type I cells– alveolar epithelial basement membrane– capillary basement membrane– endothelial cells of capillary

• Vast surface area = handball court

Details of Respiratory Membrane

• Find the 4 layers that comprise the respiratory membrane

Double Blood Supply to the Lungs

• Deoxygenated blood arrives through pulmonary trunk from the right ventricle

• Bronchial arteries branch off of the aorta to supply oxygenated blood to lung tissue

• Venous drainage returns all blood to heart

Breathing or Pulmonary Ventilation

• Air moves into lungs when pressure inside lungs is less than atmospheric pressure– How is this accomplished?

• Air moves out of the lungs when pressure inside lungs is greater than atmospheric pressure– How is this accomplished?

• Atmospheric pressure = 1 atm or 760mm Hg

Boyle’s Law

• As the size of closed container decreases, pressure inside is increased

• The molecules have less wall area to strike so the pressure on each inch of area increases.

Dimensions of the Chest Cavity

• Breathing in requires muscular activity & chest size changes• Contraction of the diaphragm flattens the dome and increases the

vertical dimension of the chest

• Diaphragm moves 1 cm & ribs lifted by external intercostal muscles

• Intrathoracic pressure falls and 2-3 liters of air is inhaled

Quiet Inspiration

• Passive process with no muscle action• Elastic recoil & surface tension in alveoli pulls inward• Alveolar pressure increases & air is pushed out

Quiet Expiration

Labored Breathing

• Forced expiration– abdominal mm force

diaphragm up– internal intercostals

depress ribs

• Forced inspiration– sternocleidomastoid,

scalenes & pectoralis minor lift chest upwards as you gasp for air

IntrapleuralPressures

(see text p. 885) &

Intrathoracicpressures

• Always subatmospheric (756 mm Hg)• As diaphragm contracts intrathoracic pressure

decreases even more (754 mm Hg)

Alveolar Surface Tension

• Thin layer of fluid in alveoli causes inwardly directed force = surface tension– water molecules strongly attracted to each

other• Causes alveoli to remain as small as possible• Detergent-like substance called surfactant

produced by Type II alveolar cells – lowers alveolar surface tension– insufficient in premature babies so that alveoli

collapse at end of each exhalation


Pneumothorax

• Pleural cavities are sealed cavities not open to the outside

• Injuries to the chest wall that let air enter the intrapleural space– causes a pneumothorax– collapsed lung on same side as injury – surface tension and recoil of elastic fibers

causes the lung to collapse


Compliance of the Lungs

• Ease with which lungs & chest wall expand depends upon elasticity of lungs & surface tension

• Some diseases reduce compliance– tuberculosis forms scar tissue– pulmonary edema - fluid in lungs & reduced

surfactant– paralysis

Airway Resistance

• Resistance to airflow depends upon airway size– increase size of chest

• airways increase in diameter– contract smooth muscles in airways

• decreases in diameter

Breathing Patterns

• Eupnea = normal quiet breathing (yu-p-ne a)• Apnea = temporary cessation of breathing (ap ne a)• Dyspnea =difficult or labored breathing (disp-ne a)• Tachypnea = rapid breathing (tak-ip-ne a)• Diaphragmatic breathing = descent of diaphragm

causes stomach to bulge during inspiration• Costal breathing = just rib activity involved

Modified Respiratory Movements• Coughing

– deep inspiration, closure of glottis & strong expiration blasts air out to clear respiratory passages

• Hiccuping– spasmodic contraction of diaphragm & quick

closure of glottis produce sharp inspiratory sound• Valsalva maneuver

- forced exhalation against a closed glottis as may occur when lifting a heavy weight

• Chart of others on page 868


The Gas Laws

Boyle’s Law – the pressure of a gas varies inversely with its volume (if temperature remains constant).

Gay-Lussac’s Law – the pressure of a gas increases directly in proportion to its (absolute) temperature.


The Gas Laws

Dalton’s Law – in a mixture of gasses, each gas exerts a partial pressure, proportional to its concentration.

Henry’s Law – the quantity of a gas that will dissolve in a liquid is directly in proportional to its partial pressure, if temperature remains constant.


What is the Composition of Air?

• Air = 20.93% O2, 79.04% N2 and 0.03% CO2• Alveolar air = 14% O2, 79% N2 and 5.2% CO2• Expired air = 16% O2, 79% N2 and 4.5% CO2

– Anatomical dead space = 150 ml of 500 ml of tidal volume

Dalton’s Law

• In a mixture of gasses, each gas exerts a partial pressure, proportional to its concentration.

• Each gas in a mixture of gases exerts its own pressure• as if all other gases were not present• partial pressures denoted as p• Total pressure is sum of all partial pressures

• atmospheric pressure (760 mm Hg) = pO2 + pCO2 + pN2 + pH2O

Thus in atmospheric air with a total pressure of

760 mm Hg, O2 which makes up 20.93% - has a

partial pressure of 20.93/100 x 760 = 159.1 mm Hg.

Henry’s Law

• The quantity of a gas that will dissolve in a liquid is directly proportional to its partial pressure, if temperature remains constant.

OR

• The quantity of a gas that will dissolve in a liquid depends upon the amount of gas present and its solubility coefficient


Partial Pressures of Respiratory Gases at Sea Level

Total 100.00 760.0 760 760 706 0

H2O 0.00 0.0 47 47 47 0

O2 20.93 159.1 105 100 40 60

CO2 0.03 0.2 40 40 46 6

N2 79.04 600.7 568 573 573 0

Partial pressure (mmHg)

% in Dry Alveolar Arterial Venous DiffusionGas dry air air air blood blood gradient


The Processes of Respiration• Pulmonary ventilation – or breathing, is the mechanical flow of

air into (inhalation) and or out of (exhalation) the lungs

• External respiration – is the exchange of gases between the air spaces of the lungs and the blood in the pulmonary capillaries. In this process, pulmonary capillary blood gains O2

and loses CO2

• Internal respiration – is the exchange of gases between blood in systemic capillaries and tissue cells. The blood loses O2 and gains CO2. Within cells, the metabolic reactions that consume O2 and give off CO2 during the production of ATP termed cellular respiration

External Respiration

• Gases diffuse from areas of high partial pressure to areas of low partial pressure

• Exchange of gas between air & blood

• Deoxygenated blood becomes saturated

• Compare gas movements in pulmonary capillaries to tissue capillaries

Rate of Diffusion of Gases

• Depends upon partial pressure of gases in air

– p O2 at sea level is 160 mm Hg

– 10,000 feet is 110 mm Hg / 50,000 feet is 18 mm Hg• Large surface area of our alveoli• Diffusion distance is very small (0.5 µm)• Solubility & molecular weight of gases

– O2 smaller molecule diffuses somewhat faster

– CO2 dissolves 24x more easily in water so net outward diffusion of CO2 is much faster

Internal Respiration

• Exchange of gases between blood & tissues

• Conversion of oxygenated

blood into deoxygenated

• Observe diffusion of O2 inward

– at rest 25% of available O2 enters cells

– during exercise more O2 is absorbed

• Observe diffusion of CO2

outward

Oxygen Transport in the Blood

• Oxyhemoglobin contains 98.5% chemically combined oxygen and hemoglobin

– inside red blood cells

• Does not dissolve easily in water– only 1.5% transported dissolved in blood

(plasma)

• Blood is almost fully saturated at pO2 of 60mm– people OK at high

altitudes & with some diseases

• Between 40 & 20 mm Hg, large amounts of O2 are released as in areas of need like contracting muscle

Hemoglobin and Oxygen Partial Pressure

Acidity & Oxygen Affinity for Hb

• As acidity increases, O2 affinity for Hb decreases

• Bohr effect• H+ binds to

hemoglobin & alters it

• O2 left behind in needy tissues

pCO2 & Oxygen Release

• As pCO2 rises with exercise, O2 is released more easily

• CO2 converts to carbonic acid & becomes H+ and bicarbonate ions & lowers pH.

Temperature & Oxygen Release

• Metabolic activity

& heat• As temperature

increases, more

O2 is released


Carbon Monoxide Poisoning

• CO from car exhaust & tobacco smoke

• Binds to the Hb heme group more successfully than O2

• CO poisoning

• Treat by administering pure O2


Carbon Dioxide Transport

• 100 ml of blood carries 55 ml of CO2

• Is carried by the blood in 3 ways– dissolved in plasma– combined with the globin part of Hb molecule

forming carbaminohemoglobin– as part of bicarbonate ion

• CO2 + H2O combine to form carbonic acid (H2CO3) that dissociates into hydrogen ions (H+) and bicarbonate ions

(HCO3-)

Role of the Respiratory Center

• Respiratory mm. controlled by neurons in pons & medulla

• 3 groups of neurons– medullary rhythmicity– pneumotaxic– apneustic centers


CONDITIONS AT VARIOUS ALTITUDES

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Tortora & Grabowski 9/e 2000 JWS 23-1 BIOLOGY 252 Human Anatomy & Physiology Chapter 23 The Respiratory System: Lecture Notes