McCance Patho Chapter 34

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Structure and Function of the Pulmonary System

Nasopharynx and Oropharynx

the upper airway that warms, humidifies and cleans the air

Larynx

Connects the upper and lower airways. Consists of the endolarynx, which forms the vocal cords.

Cartilage rings

prevent airway collapse

Carina

where the trachea divides into two main airways.

Stimulation of the carina causes

coughing

Hila

Where the bronchi enter the lungs

How many lobes in the left lung

2

How many lobes in the right lung

3

mediastinum

the space between the lungs

Bronchioles

sixteen divisions and the smallest of the conducting airways

Respiratory bronchioles

16th-23rd division, increasing number of alveoli, gas exchange airway

goblet cells

mucus-secreting cells in the epithelial lining of the bronchial walls

Acinus

respiratory bronchioles, alveolar ducts, alveoli. The structures that participate in gas exchange.

Pores of Kohn

Allow pressure to equalize between adjacent alveoli. Tiny passages that permit some air to pass through the septa from alveolus to alveolus

The pulmonary circulation has ___________ pressure and resistance than systemic circulation

Lower (18mm Hg, 1/5 of the pressure of the systemic circulation)

The acinus (does, does not) have accompanying lymphatic capillaries.

Does not

A terminal bronchiole (does, does not) have accompanying lymphatic capillaries

Does

Type I alveolar cells

Provide structure

Type II alveolar cells

Secrete surfactant

Pulmonary and Bronchial Circulation function to:

1) Facilitate gas exchange
2) Deliver nutrients to lung tissues
3) Act as a reservoir for the left ventricle
4) Filter and remove debris from the circulation

Usually how much of the pulmonary vessels are perfused at any given time?

1/3 (When carciac output increases, additional vessels become perfused and the mean arterial pressure remains low.)

The most effective way to measure the adequacy of alveolar ventilation is to measure____________.

PaCO2

The site of gas exchange

Alveolocapillary membrane

What is unique about bronchial circulation?

Not all of its capillaries drain into its own venous system, but empty into the pulmonary vein and contribute to the normal venous admixture.

Trachea

Connects larynx to the bronchi

surfactant

Lipoprotein--90% lipids, 10% protein. Coats inner surface of alveoli

Pulmonary veins

Similar to systemic veins, but have not valves

Hypoxic pulmonary vasoconstriction

Vasoconstriction cause by alveolar and pulmonary venous hypoxia. The most important cause of pulmonary artery constriction is low alveolar partial pressure of oxygen (PAO2)

Ventilation

The mechanical movement of gas or air into and out of the lungs

Respiration

Exchange of O2 and CO2 during cellular metabolism

Alveolar dead space

volume of gas in unperfused alveoli

alveolar ventilation

portion of tidal volume that reaches alveoli; during expiration, part of this alveolar gas remains in the conducting airways and moves back into the alveoli with next inspiration

anatomic dead space

portion of tidal volume that remains in conducting airways; approximately 1/3 of each breath

dead-space ventilation

volume of air that is wasted--does not participate in gas exchange

expiratory reserve volume (ERV)

amount of gas that can be expired after a passive expiration

Functional residual capacity (FRC)

amount of gas remaining in the lung at the end of a passive expiration (RV + ERV)

Inspiratory Capacity (IC)

amount of gas that can be inspired after a passive expiration (includes Vt and IRV)

Inspiratory reserve volume (IRV)

amount of gas that can be inspired in addition to tidal volume

minute volume

ventilatory rate (breaths per minute) times the tidal volume (liters per breath)

physiologic dead space

sum of normal anatomic dead space and alveolar dead space

residual volume (RV)

volume of gas that cannot be expired and is always present in the lung

tidal volume (Vt)

amount of gas inspired and expired during normal breathing

total lung capacity (TLC)

total gas volume in the lung when it is maximally inflated (RV + ERV + Vt + IRV)

vital capacity (VC)

maximum amount of gas that can be displaced (expired) from the lung (IRV + Vt + ERV)

The neurons that control respiration are located in the _______________

brainstem

Parasympathetic stimulation causes airways to _______________

constrict

Sympathetic stimulation causes airways to ________________

dilate

Bohr Effect

The shift in the oxyhemoglobin dissociation curve caused by alteration in pH and PaCO2

The basic automatic rhythm of respiration is set by the _____________

Dorsal respiratory group (DRG) located in the respiratory center

Which group of neurons receives afferent impulses from peripheral chemoreceptors in the carotid and aortic bodies?

the Dorsal respiratory group (DRG)

Ventral Respiratory Group (VRG)

located in the medulla; almost inactive during normal, quiet respiration; becomes active when increased ventilation effort is required

pneumotaxic center and apneustic center

situated in the pons; do not generate primary rhythm, but act as modifiers of the inspiratory depth and rate established in the medullary centers

breathing can also be modified by the __________, _____________, and ________________.

cortex, limbic system, hypothalamus

Irritant receptors

in the lung conducting airways; sensitive to noxious aerosols and dust; initiate cough reflex

stretch receptors

found in smooth muscles of airways and are sensitive to increases in size or volume.

j- receptors

located near alveolar capillaries; sensitive to decrease in alveolar size due to edema and fibrosis; stimulate rapid, shallow breathing. Also stimulates laryngeal constriction on expiration and mucous secretion; hypotension; bradycardia

central chemoreceptors

monitor arterial blood indirectly by sensing changes in pH of the CSF. Sensitive to hydrogen ion concentration in the CSF. Sensitive to very small changes.

peripheral chemoreceptors

located in the aortic bodies, aortic arch and carotid bodies and are sensitive to oxygen levels (PaO2) in arterial blood. Not as sensitive as the central chemoreceptors.

The peripheral chemoreceptors will respond once the PaO2 drops below __________.

60 mmHg

Major muscles of inspiration

Diaphragm and external intercostal muscles

Accessory muscles of inspiration

sternocleidomastoid and scalene muscles

compliance

measure of lung and chest wall distensibility and represents the relative ease with which these structures can be stretched.

elasticity

tendency of a structure to resist stretching and when stretched, return to its original shape

Surfactant proteins SP-B and SP-C

small hydrophobic molecules that have a detergent-like effect that separates the liquid molecules, thereby decreasing aleveolar surface tension.

Surfactant proteins SP-A and SP-D

consists of large hydrophillic molecules called collectins (pattern recognition molecules) that are capable of inhibiting foreign pathogens.

Airway resistance

Normally very low. 1/2 - 2/3 of resistance occurs in the nose. Determined by the length, radius, and cross-sectional area of the airway and density, viscosity and velocity of the gas.

Ohm's Law

Resistance = Change in pressure/rate of flow

Which steps are involved in the process of gas exchange?

Ventilation, perfusion, and diffusion

Which side of the oxyhemoglobin dissociation curve represents the situation of blood in the lungs?

Left (increased affinity)

Which side of the oxyhemoglobin dissociation curve represents the situation of the blood in the tissues?

Right (decreased affinity)

List three factors that cause the oxyhemoglobin dissociation curve to shift to the right (decreased affinity)?

Increase in PaCO2 (hypercapnea), increase in acidosis, hyperthermia

A shift to the left (increased affinity) in the oxyhemoglobin dissociation curve may be caused by...

alkalosis, hypocapnia (decrease in PaCO2), hypothermia, decrease in 2,3-diphosphoglycerate, carbon monoxide

spirometery

measure forced expiration--both volume and flow. FVC and FEV1 most important

diffusing capacity

Measure of the rate of gas diffusion across the alveolocapillary membrane. Determines how much CO2 is taken up by the blood and dividing this amount by the pressure gradient across the alveocapillary membrane

chest radiograms

abnormalities of the pulmonary system--among the most commom of examinations

Which alterations involved with aging are considered normal?

Increased flow resistance, alterations in gas exchange, loss of recoil.

Elastin

Fibers that give lung tissue its elasticity

oxyhemoglobin

hemoglobin molecules that have bound oxygen

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