Mechanics of Breathing 17 & 18

Respiratory System Functions & Structures Fuctions: Exchange of gases between the atmosphere and the blood- inhale O2 and exhale CO2 Homeostatic regulation of body pH- the amounts of CO2 in the blood affect the pH Protection from inhaled pathogens and irritating substances- preventive mechanisms against pathogens that could cause harm Vocalization- voice production is possible when one exhales Structures or zones Conducting system (zone)- components of the respiratory tract that are involved with the flow of air and not the exchange Respiratory zones- site where gas exchange occurs Alveoli- site for quick two-way transfer of substances between the blood and the lung tissue Bones and muscle of thorax- (muscular pump) use to increase or decrease pressure. Includes the diaphram, internal/external intercostal, abdominals, ect.

Respiratory System Ventilation External Respiration Circulation Pulmonary circulation: Right ventricle  pulmonary trunk  lungs  pulmonary veins  left atrium Ventilation External Respiration Circulation Internal Respiration Cellular Respiration Figure 17-1

Conditioning Functions performed by the respiratory epithelium found in the nasal cavity and trachea: Warming air to body temperature Adding water vapor Filtering out foreign material

Respiratory System There are three sections to the pharynx. The upper respiratory tract is purely a conduction zone. Lower respiratory tract includes conduction and respiratory zones Lungs are surrounded by serous membranes called pleura Figure 17-2a

Detailed Anatomy of Upper Respiratory Tract

The Plural Membranes The relationship between the pleural sac and the lung Pleural fluid reduces friction and protects the lungs Figure 17-3

Muscles Used for Ventilation Some muscles are only used during forceful expiration or inspiration Figure 17-2b

Movement of the Diaphragm

Movement of the Rib Cage during Inspiration Rib movement increases or decreases the width of the rib cage.

Branching of Airways Branching of airways changes in ways similar to how it occurs in blood vessels. In the lungs airway diameter is also mediated by smooth muscle Figure 17-2e

Branching of the Airways As branching becomes more numerous the wall thins out. Alveoli design allows for increased surface area. Figure 17-4

Alveolar Structure Type I cells make up the walls of the alveoli Type II cells release surfactant to prevent alveolar collapse Figure 17-2g

Alveoli & Capillary Walls

Principles of Bulk Flow THESE ARE FACTORS THAT AFFECT THE FLOW OF AIR- NOTICE HOW THEY ARE THE SAME AS THOSE THAT AFFECT THE FLOW OF BLOOD Flow from regions of higher to lower pressure Boyle’s Law P1V1=P2V2 Decreasing volume increases collision & decreases pressure Muscular pump creates pressure gradients Muscular contractions increase or decrease the size of the thoracic cavity, changing the pressure so air moves in or out Resistance to flow Diameter of the bronchiole tubes changes size to increase or decrease resistance. Bronchoconstriction increases resistance and reduces flow

Spirometer This apparatus measure the air going into or out of the lungs. It does not measure the TOTAL air volume moving in the lungs because, like the heart, they are never completely empty. Figure 17-6

Air Flow Flow  P/R = air flows due to pressure gradient and decreased with increased resistance Alveolar pressure or intrapleural pressure can be measured = the amount of air that moves in/out can be used to infer pressure Single respiratory cycle consists of inspiration followed by expiration= remember- there is quiet and forced breathing

Lungs Volumes and Capacities RV= residual volume ERV=air forcefully exhaled Vt= amount the is normally exhaled& inhaled IRV= additional air above Vt VC=maximum amount of air that can move in/out Figure 17-7

Pressure Changes during Quiet Breathing Notice the intrapleural pressure drops more than alveolar and it is not exactly aligned with alveolar changes Figure 17-11

Pressure in the Pleural Cavity The pull on the walls creates a pressure lower than atmospheric- allowing air to move in and keep the lung from collapsing. Pneumothorax results in collapsed lung that can not function normally Figure 17-12a

Compliance and Elastance Compliance: ability to stretch High compliance- not a helpful condition in lungs Stretches easily- but has low recoil thus its hard to exhale Low compliance Requires more force- more work is needed to stretch a stiff lung Restrictive lung diseases- pathology decreasing compliance Fibrotic lung diseases and inadequate surfactant production- inelastic scar tissue and alveolar walls that stick together Elastance: returning to its resting volume when stretching force is released

Surface Tenstion and Surfactant Surface tension is created by the thin fluid layer between alveolar cells and the air Mixture containing proteins and phospholipids that reduces surface tension. Increased surface tension would cause the alveolar walls to stick to each other Newborn respiratory distress syndrome Premature babies may have inadequate surfactant concentrations making difficult for them to breathe

Ventilation **** Total pulmonary ventilation and alveolar ventilation Total pulmonary ventilation = ventilation rate  tidal volume 150 mL 350 2700 mL 2200 mL Dead space filled with fresh air PO2 = 160 mm Hg PO2 ~ 100 mm Hg ~ Respiratory cycle in an adult End of inspiration Inhale 500 mL of fresh air (tidal volume). Dead space filled with stale air KEY Only 350 mL reaches alveoli. The first exhaled air comes out of the dead space. Only 350 mL leaves the alveoli. Dead space is filled with fresh air. The first 150 mL of air into the alveoli is stale air from the dead space. At the end of expiration, the dead space is filled with “stale” air from 500 mL Atmospheric air Exhale 500 mL 1 2 3 4 Figure 17-14

Ventilation Figure 17-14, steps 1–2 Dead space filled with fresh air 150 mL 2700 mL 2200 mL Dead space filled with fresh air PO2 = 160 mm Hg PO2 ~ 100 mm Hg ~ Respiratory cycle in an adult End of inspiration KEY The first exhaled air comes out of the dead space. Only 350 mL leaves the alveoli. 350 Exhale 500 mL (tidal volume). 1 2 Figure 17-14, steps 1–2

Ventilation Figure 17-14, steps 1–3 150 mL 2700 mL 2200 mL Dead space filled with fresh air PO2 = 160 mm Hg PO2 ~ 100 mm Hg ~ Respiratory cycle in an adult End of inspiration Dead space filled with stale air KEY The first exhaled air comes out of the dead space. Only 350 mL leaves the alveoli. At the end of expiration, the dead space is filled with “stale” air from alveoli. 350 Exhale 500 mL (tidal volume). 1 2 3 Figure 17-14, steps 1–3

Ventilation Figure 17-14, steps 1–4 150 mL 350 2700 mL 2200 mL Dead space filled with fresh air PO2 = 160 mm Hg PO2 ~ 100 mm Hg ~ Respiratory cycle in an adult End of inspiration Inhale 500 mL of fresh air (tidal volume). Dead space filled with stale air KEY Only 350 mL reaches alveoli. The first exhaled air comes out of the dead space. Only 350 mL leaves the alveoli. Dead space is filled with fresh air. The first 150 mL of air into the alveoli is stale air from the dead space. At the end of expiration, the dead space is filled with “stale” air from 500 mL Atmospheric air Exhale 500 mL 1 2 3 4 Figure 17-14, steps 1–4

Ventilation Figure 17-14, steps 1–5 150 mL 350 2700 mL 2200 mL Dead space filled with fresh air PO2 = 160 mm Hg PO2 ~ 100 mm Hg ~ Respiratory cycle in an adult End of inspiration Inhale 500 mL of fresh air (tidal volume). Dead space filled with stale air KEY Only 350 mL reaches alveoli. The first exhaled air comes out of the dead space. Only 350 mL leaves the alveoli. Dead space is filled with fresh air. The first 150 mL of air into the alveoli is stale air from the dead space. At the end of expiration, the dead space is filled with “stale” air from 500 mL Atmospheric air Exhale 500 mL 1 2 3 4 Figure 17-14, steps 1–5

Ventilation Alveolar ventilation = ventilation rate  (tidal volume – dead space volume)

Ventilation

Ventilation Effects of changing alveolar ventilation on PO2 and PCO2 in the alveoli Figure 17-15

Ventilation Notice that the sytemic arterioles and bronchioles react the same and opposite to the pulmonary arterioles.

Ventilation Auscultation = diagnostic technique- listening to breath sounds to resulting from different types of fluid accumulations or membrane changes Obstructive lung diseases- cause narrowing of the bronchioles reducing the amount of air flow Asthma- caused by allergies leading to inflammation or edema Emphysema- reduction in alveolar surface area, decreased tissue elasticity, mucous build-up Chronic bronchitis- also called COPD- inflammation of the bronchioles due to infection

Causes of Low Alveolar PO2 (Chapter 18) Inspired air has abnormally low oxygen content Altitude Alveolar ventilation is inadequate Decreased lung compliance Increased airway resistance Overdose of drugs Pathological changes Decrease in amount of alveolar surface area Increase in thickness of alveolar membrane Increase in diffusion distance between alveoli and blood

Alveolar Ventilation (Chapter 18) Pathological conditions that reduce alveolar ventilation and gas exchange -only high altitude reduces oxygen amounts in air -most disorders are due to decreased lung compliance, increased resistance, or slow ventilation (CNS affected) Figure 18-4a

Alveolar Ventilation (Chapter 18) Diffusion rate is proportional to surface area- here the walls are broken down, the lung now has high-compliance, low-elasticity Figure 18-4b

Healthy Lung Emphysema

Alveolar Ventilation (Chapter 18) Diffusion rate is inversely proportional to membrane thickness- thickened by scar tissue Figure 18-4c

Alveolar Ventilation (Chapter 18) Diffusion rate is inversely proportional to distance Figure 18-4d

Alveolar Ventilation (Chapter 18) Decreased ventilation brings in low oxygen and thus the blood will have less oxygen dissolved in it Figure 18-4e

Lung Cancer