Chapter 19 :The Respiratory System

The respiratory system consists of a series of passages that

The entire process of exchanging gases between the atmosphere and the body cells is called respiration. It involves several smaller steps:

Breathing or ventilation.



External respiration.

Transport of gases by the blood


Internal respiration.


Cellular respiration.



 

(Review - the reason we breathe is:

Divided into two parts, or tracts:

Upper respiratory tract -

Lower respiratory tract - l

URT:

Nose

Openings to the exterior are the external nares (NA-reez) or nostrils.

Hairs prevent -

The internal portion communicates with

The nasal cavity is divided

On the lateral sides of the nasal cavity are the nasal conchae or turbinate bones.

The nose warms

moistens

 and filters air

and functions in olfaction and speech

Pharynx

 The anatomic regions are the nasopharynx, oropharynx, and laryngopharynx.

The nasopharynx functions in respiration.

 The oropharynx and laryngopharynx function both in digestion and in respiration.
 

Larynx The larynx (voice box) is a passageway that connects the pharynx with the trachea. It functions in:

The larynx contains muscle, and 9 cartilages connected by elastic tissue.

the thyroid cartilage

The cricoid cartilage

The epiglottic cartilage is the only cartilage of the larynx that is elastic instead of hyaline cartilage.

The paired, pyramid shaped arytenoid (ar-i-TEE-noid) cartilages

Attached to the tips of the arytenoid cartilages are the corniculate (cor-NIK-yoo-late) cartilages.

The cuneiform (kynoo-NEE-i-form) cartilages are small cylindrical structures in the mucous membrane between the epiglottic and arytenoid cartilages

Inside the larynx are two pairs of horizontal folds of muscle and connective tissue, covered with mucous membrane.

 The upper folds are called the "false vocal cords"

The true vocal cords contain elastic fibers.

 

Trachea The trachea (windpipe) extends from the larynx to the primary bronchi.(T5) (5" X 1").

It is composed of smooth muscle ( trachealis muscle )and about 20 C- shaped rings of cartilage.

 It is lined with

 Where the trachea divides into the right and left primary bronchi is a ridge called the carina (ka-REYE-na). 


 Two methods of bypassing obstructions from the air ways are
 

Bronchi

Bronchi:
Branching off the trachea are the right and left primary bronchi.

The right primary bronchus is:



The secondary or lobar bronchi -

Tertiary or segmental bronchi -

Intralobular bronchioles-

Terminal bronchioles -

Respiratory bronchioles -
 

Alveolar ducts:

The walls of bronchi contain

Walls of bronchioles contain

Contraction of the smooth muscle is controlled by the autonomic nervous system

Lungs

 

The right lung has three lobes separated by two fissures


Apex, base, hilus.

 

Secondary bronchi give rise to branches called segmental bronchi, which supply segments of lung tissue called bronchopulmonary segments.
 

Each bronchopulmonary segment consists of lobules.


Terminal bronchioles divide into respiratory bronchioles

 alveolar ducts, alveolar sacs, and alveoli.

Alveolar sacs are two or more alveoli that share a common opening.

Alveolar walls consist of type I alveolar cells

type II alveolar cells


surfactant

Alveolar Surface Tension




When an infant is born prematurely, less than 37 weeks of gestation, the surfactant producing cells in the alveoli are to immature to function adequately, resulting in "respiratory-distress syndrome of the newborn."

 The treatment used to involve delivering high amounts of O2 under pressure.

retrolental fibroplasia.


Arterial oxygen pressures should be monitored, and should not exceed 100 mm Hg.

Also present are alveolar macrophages (dust cells).


The alveoli are surrounded by

Gas exchange occurs across the alveolar-capillary (respiratory) membranes.

PULMONARY VENTILATION Breathing

 Air moves in and out of the lungs depending on the pressure gradient.

Inspiration




The most important muscle of inspiration is





 If more air is needed, additional muscles, such as the pectoralis minors, scalenes, and sternocleidomastoids can pull the thoracic cage further upward and outwards decreasing the pressure even more.

Breathing consists of inspiration and expiration.

Expiration Expiration occurs when alveolar pressure

 

Forced expiration employs contraction of the

 

Breathing Patterns

Eupnea.

Apnea -

Dyspnea -

tachypnea -

LUNG VOLUMES AND CAPACITIES
In clinical practice, respiration refers to



 Lung volumes measured by spirometry include:

tidal volume -

Other lung volumes come into play as a result of strenuous breathing. In general, these volumes are greater in males, taller persons and younger adults.

inspiratory reserve volume-

expiratory reserve volume -

Residual volume

inspiratory capacity -

functional residual capacity-

vital capacity  -

and total lung capacity -

Other lung volumes are anatomic dead space -

minute volume of respiration = tidal volume X breaths per minute

alveolar ventilation rate=

CONTROL OF RESPIRATION

Respiration is a

Respiratory Center

The respiratory center is made up of

The medullary rhythmicity


 

The ventral respiratory group has two sets of neurons.
The expiratory center

Other neurons in this area generate impulses that cause increased inspiratory movement.

Although the medulary rhythmicity center controls the basic rhythm of respiration,

pneumotaxic area
 

apneustic area
 

Regulation of the Respiratory Center

cortical influences -

chemical stimuli

these receptors respond vigorously to the increase in H+

Peripheral chemoreceptors

neural changes due to movement

Other factors:

the limbic system

pain

irritation to the airways

EXCHANGE OF OXYGEN AND CARBON DIOXIDE

Exchanges of O₂ and CO₂ are purely passive processes, operating by diffusion, and depend on the behavior of gases.

Gas Laws The partial pressure of a gas is the pressure exerted by that gas in a mixture of gases. It is symbolized by p. According to Dalton's law, each gas in a mixture of gases exerts its own pressure as if all the other gases were not present.

atmospheric pressure (760) = pO₂ + pCO₂+pN₂ + pH₂O

The partial pressure of each gas can be found by multiplying the total pressure by the percentage of that gas.

These gases will diffuse down a concentration gradient determined by their partial pressures.

External Respiration

 

The pO₂ of alveolar air is 105 mm Hg pO₂ of deoxygenated blood is 40 mm Hg.

 

The same process occurs with CO2. The pCO2 at the alveolus is 40, and in deoxygenated blood is 45.

 

The factors involved are:

partial pressure differences :

 

10,000 feet = 110 mm Hg

20,000 feet = 73 mm Hg

50,000 feet = 18 mm Hg

the rate of airflow into and out of the lungs -

a large surface area for gas exchange -
 

a small diffusion distance -
 

Solubility and molecular weight :

 

Internal Respiration
 

pO2 of oxgenated blood = 100 mm Hg

pO2 in tissues = 40 mm Hg

pCO2 in oxygenated blood = 40

pCO2 in tissues = 45

TRANSPORT OF OXYGEN AND CARBON DIOXIDE

Oxygen Transport

 oxyhemoglobin (HbO2). Hb + O2 = HbO2

The association of O2 and hemoglobin is affected by:

pO2
 

acidity (pH),
 

pCO2

CO2 + H2O ↔ H2CO3 ↔ H⁺ + HCO3^-

temperature

BPG. a substance found in RBC's is called 2,3-biphosphoglycerate.

Fetal hemoglobin

Hypoxia :

anemic

stagnant -

histotoxic. -

Carbon Dioxide Transport


 

Blood supply to the lungs

 

Pulmonary circulation

 

Compliance

 

Airway Resistance