SCIT 1408 Applied Human Anatomy and Physiology II - Respiratory System Chapter 22 A

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Respiratory System Consists of the respiratory and conducting zones Respiratory zone:

Site of gas exchange respiratory bronchioles (just before alveolar

ducts) alveolar ducts alveolar sacs alveoli


Respiratory System: Conducting zone:

Conduits for air to reach respiratory zone nose, nasal cavity pharynx, trachea rt, left primary bronchus secondary bronchi, tertiary bronchi bronchioles, to terminal bronchiols)

Respiratory muscles – diaphragm, internal & external intercostals

PLAYInterActive Physiology ®: Anatomy Review: Respiratory Structures, page 3


Respiratory System

Figure 22.1

Respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli


Major Functions of the Respiratory System Supply oxygen and dispose of carbon dioxide Respiration/ventilation – 4 processes must happen

1. Pulmonary ventilation – air moves in/out of lungs

2. External respiration – O2 in CO2 out; blood/lungs

3. Transport- gas transport between lungs & tissues

4. Internal respiration- O2 out CO2 in; blood/tissues


Conducting zone: Function/Structure of the Nose

Functions: Airway for respiration Moistens, warms, filters air Olfactory receptors

Structure: Nasal bone Cartilage plates with dividing septum


Structure of the Nose

Figure 22.2a


Structure of the Nose

Figure 22.2b


Conducting zone: Nasal Cavity

Figure 22.3b


Paranasal Sinuses Sinuses in bones that surround the nasal cavity Sinuses lighten the skull and help to warm and

moisten the air


Conducting zone: Pharynx Tube of skeletal muscle between nasal cavity &

esophagus (C6); 3 parts:

1. Nasopharynx –air passageway; closes during swallowing; pharyngeal tonsils; auditory tube

2. Oropharynx- food & air passageway; palatine & lingual tonsils

3. Laryngopharynx- food & air passageway; posterior to epiglottis, superior to esophagus


Conducting zone: Larynx (Voice Box) Attaches to hyoid bone; between laryngopharynx

& trachea Continuous with the trachea posteriorly Functions:

1. To provide a patent airway

2. Route air and food into the proper channels; epiglottis

3. Voice production


Framework of the Larynx

Figure 22.4a, b

hyaline

Elastic cartilage


Movements of Vocal Cords

Figure 22.5


Sphincter Functions of the Larynx The larynx is closed during coughing, sneezing, and

Valsalva’s maneuver Valsalva’s maneuver

Air is temporarily held in the lower respiratory tract by closing the glottis

Causes intra-abdominal pressure to rise when abdominal muscles contract

Helps to empty the rectum Acts as a splint to stabilize the trunk when lifting

heavy loads


Conducting zone: Trachea

Figure 22.6a

Cartilage rings open posteriorly

Smoking destroys cilia


Conducting Zone: Bronchi Carina- tracheal cartilage @ end of trachea,

beginning of bronchi Air reaching the bronchi is:

Warm and cleansed of impurities Saturated with water vapor

Bronchi subdivide into secondary bronchi, each supplying a lobe of the lungs

Air passages undergo 23 orders of branchingPLAY InterActive Physiology ®:

Anatomy Review: Respiratory Structures, page 6


Conducting Zone: Bronchial Tree Tissue walls of bronchi mimic that of the trachea As conducting tubes become smaller, structural

changes occur

1. Cartilage rings become plates

2. Epithelium from pseudostratified ciliated columnar to columnar

3. Amount of smooth muscle increases


Conducting Zones: Bronchial Tree

Figure 22.7

(thru terminal bronchiols)


Respiratory Zone

Figure 22.8a

Alveoli- most of the lungs’ volume Provide tremendous surface area for gas

exchange


Respiratory Zone

Figure 22.8b

Pores: Allow air pressure throughout the lung to be equalized


Respiratory Membrane

Figure 22.9b


Respiratory Membrane This air-blood barrier is composed of:

Alveolar and capillary walls Their fused basal laminas

Alveolar walls: Are a single layer of type I epithelial cells Permit gas exchange by simple diffusion Secrete angiotensin converting enzyme (ACE)

Type II cells secrete surfactant


Respiratory Membrane: air-blood barrier

Figure 22.9c ,d

**************


Organs in the Thoracic Cavity

Figure 22.10a


Transverse Thoracic Section

Figure 22.10c


Blood Supply to Lungs: Pulmonary & Bronchial

1. Pulmonary circulation

Pulmonary arteries to lungs for oxygen

Feed into pulmonary capillaries around alveoli

Pulmonary veins – oxygenated blood from respiratory zones to the heart

2. Bronchial circulation

From aorta, enter at hilus

Supply all lung tissue except alveoli

Bronchial veins anastomose with pulmonary veins


Pleurae: double- layered Parietal pleura

Covers thoracic wall, superior diaphragm Continues around heart and between lungs

Visceral, or pulmonary, pleura Covers the external lung surface Divides the thoracic cavity into three chambers

The central mediastinum Two lateral compartments, each containing a lung

Pleurisy


Breathing Breathing, or pulmonary ventilation, consists of

two phases Inspiration – air flows into the lungs Expiration – gases exit the lungs


Pressure Relationships in the Thoracic Cavity Respiratory pressure as relative to atmospheric

pressure

Atmospheric pressure (Patm) = 760 mm Hg

Pressure exerted by the air surrounding the body

Negative respiratory pressure < Patm;

-4mm = 756 mm Hg

Positive respiratory pressure > Patm


Pressure Relationships in the Thoracic Cavity Intrapulmonary pressure (Ppul) – pressure within the

alveoli

Intrapleural pressure (Pip) – pressure within the pleural cavity

Both fluctuate with inspiration & expiration

Ppul equalizes itself with atmospheric pressure

Pip < Ppul and < Patm

Transpulmonary pressure: Ppul minus Pip


Intrapulmonary & Intrapleural Pressure Relationships

Figure 22.12

> Transpulmonary pressure, > lung inflation


Pressure Relationships Two forces act to pull the lungs away from the

thoracic wall, promoting lung collapse

1. Elasticity of lungs causes them to assume smallest possible size; recoil

2. Surface tension of alveolar fluid draws alveoli to their smallest possible size

Opposing force – elasticity of the chest wall pulls the thorax outward to enlarge the lungs


Boyle’s Law Boyle’s law – the relationship between the pressure

and volume of gases

P1V1 = P2V2

P = pressure of a gas in mm Hg V = volume of a gas in cubic millimeters Subscripts 1 and 2 represent the initial and

resulting conditions, respectively


Inspiration The diaphragm and external intercostal muscles

(inspiratory muscles) contract and the rib cage rises The lungs are stretched and intrapulmonary

volume increases Intrapulmonary pressure drops below

atmospheric pressure (1 mm Hg) Air flows into the lungs, down its pressure

gradient, until intrapleural pressure = atmospheric pressure


Inspiration

Figure 22.13.1


Expiration Inspiratory muscles relax and the rib cage descends

due to gravity Thoracic cavity volume decreases Elastic lungs recoil passively and intrapulmonary

volume decreases Intrapulmonary pressure rises above

atmospheric pressure (+1 mm Hg) Gases flow out of the lungs down the pressure

gradient until intrapulmonary pressure is 0


Expiration

Figure 22.13.2


Pulmonary Pressures: Inspiration/Expiration

Figure 22.14

Lungs expand, pressure drops

Lungs deflate, pressure increases

Always maintains transpulmonary pressure


Lung Collapse Caused by equalization of the intrapleural pressure

with the intrapulmonary pressure Transpulmonary pressure keeps the airways open

Transpulmonary pressure – difference between the intrapulmonary and intrapleural pressures (Ppul – Pip)

Atelectasis – collapsed lung

Pneumothorax (tension) - air in intrapleural space


Pulmonary Ventilation A mechanical process that depends on volume

changes in the thoracic cavity Volume changes lead to pressure changes, which

lead to the flow of gases to equalize pressure


Friction is the major nonelastic source of resistance to airflow

The relationship between flow (F), pressure (P), and resistance (R) is:

Physical Factors Influencing Ventilation: Airway Resistance

PRF =

pressure gradient: atmosphere/alveoli

> est R in medium-sized bronchi


Resistance in Repiratory Passageways

Figure 22.15

> branches, > cross- sectional area here


Airway Resistance – Life Threatening > resistance, > effort to breathe Constricted or obstructed bronchioles from:

Reflex RXN to inhaled irritants/particles by parasympathetic nervous system

Acute asthma attacks, histamine release, actions Epinephrine

Sympathetic nervous system release; dilates bronchioles and reduces air resistance

RX for asthma attacks


Total Respiratory System Compliance

Two factors:

1. Lung compliance

2. Thoracic wall compliance


Lung Compliance Change in lung volume that occurs with a given

change in transpulmonary pressure (stretchiness) Determined by two main factors

1. Distensibility of the lung tissue (stretchiness, elasticity)

2. Surface tension of the alveoli

InterActive Physiology ®: Anatomy Review: Respiratory Structures, pages 10, 11


Factors That Diminish Lung Compliance- elasticity

Scar tissue or fibrosis of the lungs; untreated subacute asthma

Blockage of smaller respiratory passages by mucus or fluid


Factors that decrease Thoracic Wall Compliance

Decreased flexibility of the thoracic cage or its decreased ability to expand

Deformities of thorax Ossification of the costal cartilage Paralysis of intercostal muscles


Factors That Diminish Lung Compliance- Alveolar Surface Tension Surface tension – cohesion of water molecules On alveoli, water molecules would stick to each

other & shrink alveoli Surfactant, a detergent-like complex, reduces

surface tension and helps keep the alveoli from collapsing

Surfactant production develops in last 2 months of gestation, premature infants suffer from < amts; can survive at 28 wks

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SCIT 1408 Applied Human Anatomy and Physiology II - Respiratory System Chapter 22 A