Chapter 35: Structure and Function of the Pulmonary System

peripheral chemoreceptors

located in the aorta and carotid bodies and is stimulated by hypoxemia (PaO2), which results in an increase in ventilation in response to arterial hypoxemia

parietal pleura

outer layer of pleura lying closer to the ribs and chest wall; line the thoracic cavity

What mechanism promotes rapid diffusion from the alveolus into the capillary?

partial pressure of oxygen molecules (PO2)

What is the pulmonary artery pressure?

18

Causes of oxyhemoglobin disassociation curve shifting to the left

Alkalosis hypocapnia hypothermia

Where does gas exchange occur?

Alveolocapillary membrane

What role does the lymphatic system play in the respiratory system?

It keeps the lung free of fluid and providing immune defense

Oxyhemoglobin

Hgb bind to O2

What happens to lungs and chest wall when there is high compliance?

Increased work of expiration

structures of the lower respiratory tract

bronchi, bronchioles, alveolar ducts, alveoli, carina, trachea, larynx

How does alveolar ventilation or distention made possible?

by surfactant

pulmonary C-fiber receptors (juxtapulmonary capillary (J) receptors)

causes an increase in pulmonary capillary pressure, which stimulates rapid, shallow breathing; laryngeal constriction on expiration and mucus secretion; hypotension; and bradycardia

Central chemoreceptors located in the medulla provide feedback to increase the rate and depth of breathing when they sense:

central chemoreceptors

What are the two types of chemoreceptors?

central chemoreceptors and peripheral chemoreceptors

What needs to occur for even gas exchange?

even distribution of gas (ventilation) and blood (perfusion) in all parts of the lungs

When smooth muscle contracts (vasoconstriction), does pulmonary artery pressure increase or decrease?

increase

What happens when academia is present in the pulmonary artery?

it causes constriction

How to calculate effective ventilation?

ventilatory rate (breaths per min) x volume of air per breath (liters per breath, tidal volume)

Can low PAO2 be reversible?

yes, PAO2 is reversible as long as levels are corrected

What are the two types of epithelial cells found on alveoli and its functions?

- Type 1 Alveolar cells: provides structure of the alveoli - Type 2 Alveolar cells: surfactant production, which prevents lung from collapsing

functions of alveoli

- air sacs that exchange gases - site where O2 enters the blood and CO2 removed - prevent lung collapse - prevent foreign substances from entering - provide structure - secretes surfactant - promote collateral ventilation between alveoli

What two structures of the lower respiratory tract help to prevent infection?

- alveolar macrophages -surfactant

Causes of muscular effort

- decreased lung and chest wall compliance - airway obstruction caused by bronchospasm or mucous plugs

What are the function of the pulmonary circulation system?

- facilitate gas exchange - delivers nutrients to lung tissues - acts as a blood reservoir for the left ventricle - filters by removing clots, air, and other debris from circulation

What is the primary function of the pulmonary system?

- gas exchange between air and blood - ventilation - diffusion - perfusion

Name the lung sensory receptors to stimulate breathing (DRG)

- irritant receptors - stretch receptors - pulmonary C-fiber receptors (juxtapulmonary capillary (J) receptors)

What are alveolar macrophages?

- phagocytic cells in alveoli of lungs - macrophages most abundant in the lungs to provide immune support

What are the benefits of surfactant of the alveoli?

- prevents the lung from collapsing (atelectasis) - control lung inflammation - prevent oxidative injury - regulating the role of fibroblasts in airway - ingest foreign material and remove it through the lymphatic system

Pores of Kohn

- small openings in the alveolar walls that allow gases and macrophages to travel between the alveoli - promotes collateral ventilation and even air distribution between alveoli

What are the 3 functions of the pulmonary system?

1. Ventilate the alveoli 2. diffuse gases in and out of blood 3. perfuses the lungs to provide organs and tissues oxygen rich blood and low in CO2

Diseases associated with low lung and chest wall compliance

ARDS, Pneumonia, Pulmonary edema, Fibrosis

Causes of oxyhemoglobin disassociation curve shifting to the right

Acidosis hypercapnia hyperthermia

Where is the respiratory center located and what does it do?

Brainstem; controls respirations by transmitting impulses to the respiratory muscles, causing them to contract and relax

How does the nervous system control breathing?

Breathing is involuntary and it automatically adjusts ventilatory rate and volume to maintain normal gas exchange this is called neurochemical control of ventilation

What are the mechanisms of the neurochemical control of ventilation?

Chemoreceptors and lung innervation (supply of nerves)

What are the two groups involved in medullary rhythmic functions?

Dorsal Respiratory Group (DRG) Ventral Respiratory Group (VRG) * located in the medulla

chest radiograph

Evaluates air trapping, consolidation, cavity formation, or presence of tumors

diffusion capacity

Measures the gas diffusion rate at the alveolocapillary membrane

Perfusion

Movement of blood into and out of the capillary beds of the lungs to body organs and tissues

ventilation-perfusion ratio

Perfusion > ventilation in bases Ventilation > perfusion in the apices

Gas velocity increases as gas passes through a restricted area, whose law is expressed?

Poiseuille's Law

central chemoreceptors

Receptors in the central nervous system that monitor the pH of cerebrospinal fluid to help regulate ventilation rate.and depth

oxyhemoglobin dissociation curve

Relationship between available oxygen and amount of oxygen carried by hemoglobin.

Bohr effect

Shift in the oxyhemoglobin dissociation curve caused by changes in CO2 and H+ concentration in the blood

Cause of low lung and chest wall compliance

Stiff lungs- difficult to inflate

What type of cells produce surfactant?

Type II alveolar cells

pulmonary circulation

The passage of venous blood from the right atrium of the heart through the right ventricle and pulmonary arteries to the lungs where it is oxygenated and its return via the pulmonary veins to enter the left atrium and participate in systemic circulation.

Minute Volume (MV)

The volume of air breathed in one minute; tidal volume (TV) x RR = MV

function of surfactant

Thin layer of fluid that covers the alveoli. Reduces surface tension of the fluid layer lining the alveoli, preventing the alveoli from collapsing during exhalation.

True or False: The bronchial circulation is part of the systemic circulation and does not participate in gas exchange?

True

Compliance

a measure of the ease of expansion of the lungs and thorax.

arterial blood gases (ABGs)

a test performed on arterial blood to determine levels of oxygen, carbon dioxide, and pH concentrations

Mechanisms that contribute to airway resistance

airway size gas velocity (Poiseullille's Law) normally low bronchoconstriction bronchodilation

dorsal respiratory group (DRG)

alters breathing patterns to restore normal blood gases

Where is surfactant located?

alveolocapillary membrane

How to measure alveolar ventilation?

arterial blood gas analysis to measure PaCO2

What happens when one lobe is obstructed from hypoxic pulmonary vasoconstriction?

blood shunts to the well-ventilated portions of the lung, called reflex, to better match ventilation and perfusion

How does diffusion of CO2 occur?

diffusion from systemic capillaries into the cells >>> perfusion of systemic capillaries into the cells >>> diffusion of O2 from the alveoli into the capillary blood >>> ventilation of the lungs

What determines compliance of lungs?

elastic recoil and alveolar surface tension

Pulmonary hypertension

elevated pulmonary artery pressure resulting from an increase in pulmonary vascular resistance to blood flow through small arteries and arterioles.

Disease associated with high lung and chest wall compliance

emphysema

Acinus

functional respiratory unit that consists of the bronchioles, alveolar ducts, alveolar sacs, and the alveoli.

What happens when the walls of the alveolocapillary membrane thickens?

gas exchange is impaired

What happens when oxyhemoglobin disassociation curve shifts to the right?

hemoglobin has a decreased affinity to oxygen

What happens when oxyhemoglobin disassociation curve shifts to the left?

hemoglobin has an increased affinity to O2

What biochemical factors causes a decrease in diameter of the vessels in pulmonary system?

histamine, prostaglandins, endothelin, serotonin, nitric oxide, and bradykinin

What happens to lungs when there is low compliance?

increased work of inspiration d/t stiff lungs and chest wall

What happens in chronic alveolar hypoxia?

inflammation and structural remodeling in pulmonary arterioles occurs, causing permanent pulmonary artery hypertension that eventually leads to right heart failure

visceral pleura

inner layer of pleura lying closer to the lung tissue; covers the lung

oxygen transport

is the diffusion of alveolocapillary membrane

Alterations of aging pulmonary system

loss of elastic recoil stiffening of lung and chest wall alterations of gas exchange increase in flow and resistance loss of alveoli wall tissue decreased PaO2 decrease in respiratory muscle strength and endurance

Cause of high lung and chest wall compliance

loss of elastic recoil- making lungs easy to inflate

What is the main cause of pulmonary artery constriction?

low alveolar partial pressure of oxygen (PAO2)

What causes pulmonary vasoconstriction?

low partial pressure of oxygen (PAO2)

low lung and chest wall compliance

lungs and thoracic wall resist expansion

spirometry

measures volume and flow rate during forced expiration

Chemoreceptors

monitors pH, PaCO2, and PaO2

Ventilation

movement of air in and out of the lungs

Diffusion

movement of gas between air spaces and lungs

What determines work of breathing?

muscular effort required for ventilation

structures of the upper respiratory tract

nasal cavity, pharynx, larynx, oropharynx

What is the pressure in the pleural space?

negative or subatmospheric -4 to -10 mmHg

partial pressure of oxygen molecules (PO2)

pressure is greater in alveolar gas than it is in capillary blood alveoli pressure > capillary

Irritant receptors

receptors that are stimulated by noxious substances and causes cough, bronchoconstriction, and increase respiratory rate

stretch receptors

receptors that sense muscle stretch and contraction to protect against excess lung inflation, which results in decrease respiratory rate and volume

ventilatory rate

the number of times gas is inspired and expired per minute; breaths per minute

What causes academia?

respiratory acidosis and metabolic acidosis

What are the gas exchange airways?

respiratory bronchioles, alveolar ducts, alveoli

How does hypoxic pulmonary vasoconstriction occur?

results from an increase in intracellular calcium levels in smooth muscle cells in response to low O2 and the presence of charged oxygen molecules called oxygen free radicals

ventral respiratory group (VRG)

sets automatic rhythm of respiration

Tests for pulmonary function

spirometry diffusion capacity residual volume functional reserve capacity (FRC) total lung capacity arterial blood gas analysis chest radiograph

elastic recoil

tendency of the lungs to return to the resting state after inspiration

gas transport

the delivery of oxygen to the cells of the body and the removal of CO2

What happens to the diameter of the pulmonary artery when smooth muscle contracts?

the diameter of the pulmonary artery decreases

How does distribution of ventilation and perfusion achieved?

through gravity and alveolar pressure, depends on body position

What is the purpose of eliminating CO2?

to maintain a partial pressure of arterial CO2 (PaCO2) of 40 mmHg and normal acid-base balance

bronchial circulation

transports oxygenated blood to bronchi and bronchioles

Hypoxic pulmonary vasoconstriction

vasoconstriction caused by alveolar and pulmonary venous hypoxia

What happens if the whole lung is obstructed from hypoxic pulmonary vasoconstriction?

vasoconstriction occurs throughout the whole pulmonary circulation and pulmonary hypertension can result

What are the four steps of gas transport?

ventilation of the lungs >>> diffusion of O2 from the alveoli into the capillary blood >>> perfusion of systemic capillaries into the cells >>> diffusion from systemic capillaries into the cells