Respiratory system

The Respiratory System

Human Respiratory System

Figure 10.1

Components of the Upper Respiratory Tract

Figure 10.2

Passageway for respiration Receptors for smell Filters incoming air to filter larger foreign

material Moistens and warms incoming air Resonating chambers for voice

Upper Respiratory Tract Functions

Components of the Lower Respiratory Tract

Figure 10.3

Functions: Larynx: maintains an open airway, routes food and air

appropriately, assists in sound production Trachea: transports air to and from lungs Bronchi: branch into lungs Lungs: transport air to alveoli for gas exchange

Lower Respiratory Tract

Organs of the Respiratory system

Slide 13.1Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

· Nose· Pharynx· Larynx· Trachea· Bronchi· Lungs –

alveoli

Figure 13.1

Chapter 22, Respiratory System 8

Respiratory System

• Consists of the respiratory and conducting zones

• Respiratory zone– Site of gas exchange – Consists of bronchioles, alveolar ducts, and alveoli


Respiratory System

• Conducting zone – Provides rigid conduits for air to reach the sites of

gas exchange– Includes all other respiratory structures (e.g.,

nose, nasal cavity, pharynx, trachea)• Respiratory muscles – diaphragm and other

muscles that promote ventilation


Major Functions of the Respiratory System

• To supply the body with oxygen and dispose of carbon dioxide

• Respiration – four distinct processes must happen– Pulmonary ventilation – moving air into and out of

the lungs– External respiration – gas exchange between the

lungs and the blood


Major Functions of the Respiratory System

– Transport – transport of oxygen and carbon dioxide between the lungs and tissues

– Internal respiration – gas exchange between systemic blood vessels and tissues


Function of the Nose

• The only externally visible part of the respiratory system that functions by:– Providing an airway for respiration– Moistening (humidifying) and warming the

entering air– Filtering inspired air and cleaning it of foreign

matter– Serving as a resonating chamber for speech– Housing the olfactory receptors


Structure of the Nose

• The nose is divided into two regions– The external nose, including the root, bridge,

dorsum nasi, and apex – The internal nasal cavity

• Philtrum – a shallow vertical groove inferior to the apex

• The external nares (nostrils) are bounded laterally by the alae



Figure 22.2a



Figure 22.2b


Nasal Cavity

• Lies in and posterior to the external nose• Is divided by a midline nasal septum• Opens posteriorly into the nasal pharynx via

internal nares• Connects with pharynx posteriorly through

choanae (posterior nasal apertures*)• The ethmoid and sphenoid bones form the roof• The floor is formed by the hard and soft palates

*


Linings of Nasal Cavity

• Vestibule – nasal cavity superior to the nares – Vibrissae – hairs that filter coarse particles from

inspired air• Olfactory mucosa

– Lines the superior nasal cavity – Contains smell receptors– (Cribriform plate – small patch of olfactory mucosa

near roof)

*

Olfactory mucosa


Linings of Nasal Cavity

• Respiratory mucosa – Lines the balance of the nasal cavity – Glands secrete mucus containing lysozyme and

defensins to help destroy bacteria


Nasal Cavity

• Inspired air is: – Humidified by the high water content in the nasal

cavity– Warmed by rich plexuses of capillaries

• Ciliated mucosal cells remove contaminated mucus


Nasal Cavity

• Superior, medial, and inferior conchae:– Protrude medially from the lateral walls– Increase mucosal area– Enhance air turbulence and help filter air

• Sensitive mucosa triggers sneezing when stimulated by irritating particles


Functions of the Nasal Mucosa and Conchae

• During inhalation the conchae and nasal mucosa:– Filter, heat, and moisten air

• During exhalation these structures:– Reclaim heat and moisture– Minimize heat and moisture loss


Paranasal Sinuses

• Sinuses in bones that surround the nasal cavity

• Sinuses lighten the skull and help to warm and moisten the air


Pharynx

• Funnel-shaped tube of skeletal muscle that connects to the:– Nasal cavity and mouth superiorly– Larynx and esophagus inferiorly

• Extends from the base of the skull to the level of the sixth cervical vertebra


Pharynx

• It is divided into three regions– Nasopharynx– Oropharynx– Laryngopharynx


Nasopharynx

• Lies posterior to the nasal cavity, inferior to the sphenoid, and superior to the level of the soft palate

• Strictly an air passageway• Lined with pseudostratified columnar epithelium• Closes during swallowing to prevent food from

entering the nasal cavity• The pharyngeal tonsil lies high on the posterior wall • Pharyngotympanic (auditory) tubes open into the

lateral walls


Oropharynx

• Extends inferiorly from the level of the soft palate to the epiglottis

• Opens to the oral cavity via an archway called the fauces

• Serves as a common passageway for food and air• The epithelial lining is protective stratified

squamous epithelium• Palatine tonsils lie in the lateral walls of the fauces• Lingual tonsil covers the base of the tongue


Laryngopharynx

• Serves as a common passageway for food and air

• Lies posterior to the upright epiglottis• Extends to the larynx, where the respiratory

and digestive pathways diverge


Larynx (Voice Box)

• Attaches to the hyoid bone and opens into the laryngopharynx superiorly

• Continuous with the trachea posteriorly• The three functions of the larynx are:

– To provide a patent airway– To act as a switching mechanism to route air and

food into the proper channels– To function in voice production


Framework of the Larynx

• Cartilages (hyaline) of the larynx (9)– Shield-shaped anterosuperior thyroid cartilage with a midline

laryngeal prominence (Adam’s apple)– Signet ring–shaped anteroinferior cricoid cartilage– Cricoid cartilage inferior to thyroid cartilage: the only

complete ring of cartilage: signet shaped and wide posteriorly– Three pairs of small arytenoid (anchor the vocal cords),

cuneiform, and corniculate cartilages• Epiglottis – elastic cartilage that covers the laryngeal

inlet during swallowing (9th cartilage)– Attaches to back of tongue


Framework of the Larynx

Figure 22.4a, b


Vocal Ligaments

• Attach the arytenoid cartilages to the thyroid cartilage

• Composed of elastic fibers that form mucosal folds called true vocal cords– The medial opening between them is the glottis– They vibrate to produce sound as air rushes up

from the lungs


Vocal Ligaments

• False vocal cords– Mucosal folds superior to the true vocal cords– Have no part in sound production


Vocal Production

• Speech – intermittent release of expired air while opening and closing the glottis

• Pitch – determined by the length and tension of the vocal cords

• Loudness – depends upon the force at which the air rushes across the vocal cords

• The pharynx resonates, amplifies, and enhances sound quality

• Sound is “shaped” into language by action of the pharynx, tongue, soft palate, and lips


Movements of Vocal Cords

Figure 22.5

Glottis - the space between the vocal cords


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 of lower respiratory tract

Trachea • At the level of the sternal angle, the

trachea bifurcates into two smaller tubes, called the right and left primary bronchi.

• Each primary bronchus projects laterally toward each lung.

• The most inferior tracheal cartilage separates the primary bronchi at their origin and forms an internal ridge called the carina.

Bronchial tree

• A highly branched system of air-conducting passages that originate from the left and right primary bronchi.

• Progressively branch into narrower tubes as they diverge throughout the lungs before terminating in terminal bronchioles.

• Incomplete rings of hyaline cartilage support the walls of the primary bronchi to ensure that they remain open.

• Right primary bronchus is shorter, wider, and more vertically oriented than the left primary bronchus.

• Foreign particles are more likely to lodge in the right primary bronchus.

Bronchial tree• The primary bronchi enter the hilus of each lung

together with the pulmonary vessels, lymphatic vessels, and nerves.

• Each primary bronchus branches into several secondary bronchi (or lobar bronchi).

• The left lung has two secondary bronchi.The right lung has three secondary bronchi.

• They further divide into tertiary bronchi. • Each tertiary bronchus is called a segmental

bronchus because it supplies a part of the lung called a bronchopulmonary segment.

Bronchial Tree• Secondary bronchi tertiary bronchi bronchioles

terminal bronchioles • with successive branching amount of cartilage decreases and

amount of smooth muscle increases, this allows for variation in airway diameter

• during exertion and when sympathetic division active bronchodilation

• mediators of allergic reactions like histamine bronchoconstriction

• epithelium gradually changes from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium in terminal bronchioles

45

46

Carina*• Ridge on

internal aspect of last tracheal cartilage

• Point where trachea branches (when alive and standing is at T7)

• Mucosa highly sensitive to irritants: cough reflex

*


Trachea

• Composed of three layers– Mucosa – made up of goblet cells and ciliated

epithelium – Submucosa – connective tissue deep to the

mucosa– Adventitia – outermost layer made of C-shaped

rings of hyaline cartilage


Trachea

Figure 22.6a


Conducting Zone: Bronchi

• The carina of the last tracheal cartilage marks the end of the trachea and the beginning of the right and left 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 branching in the lungs


Conducting Zone: Bronchial Tree

• Tissue walls of bronchi mimic that of the trachea

• As conducting tubes become smaller, structural changes occur– Cartilage support structures change– Epithelium types change– Amount of smooth muscle increases


Conducting Zone: Bronchial Tree

• Bronchioles – Consist of cuboidal epithelium– Have a complete layer of circular smooth muscle – Lack cartilage support and mucus-producing cells


Respiratory Zone

• Defined by the presence of alveoli; begins as terminal bronchioles feed into respiratory bronchioles

• Respiratory bronchioles lead to alveolar ducts, then to terminal clusters of alveolar sacs composed of alveoli

• Approximately 300 million alveoli:– Account for most of the lungs’ volume – Provide tremendous surface area for gas exchange

Alveoli

Slide 13.17

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

· Structure of alveoli· Alveolar duct· Alveolar sac· Alveolus· Gas exchange


Alveoli• Surrounded by fine elastic fibers• Contain open pores that:

– Connect adjacent alveoli– Allow air pressure throughout the lung to be

equalized• House macrophages that keep alveolar surfaces

sterile


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

Figure 22.9b

58

Surfactant

• Type II cuboidal epithelial cells are scattered in alveolar walls

• Surfactant is a detergent-like substance which is secreted in fluid coating alveolar surfaces – it decreases tension

• Without it the walls would stick together during exhalation

• Premature babies – problem breathing is largely because lack surfactant

59

Microscopic detail of alveoli• Alveoli surrounded by fine elastic fibers• Alveoli interconnect via alveolar pores• Alveolar macrophages – free floating “dust cells”• Note type I and type II cells and joint membrane


Gross Anatomy of the Lungs

• Lungs occupy all of the thoracic cavity except the mediastinum– Root – site of vascular and bronchial attachments– Costal surface – anterior, lateral, and posterior

surfaces in contact with the ribs– Apex – narrow superior tip– Base – inferior surface that rests on the diaphragm– Hilus – indentation that contains pulmonary and

systemic blood vessels


Lungs

• Cardiac notch (impression) – cavity that accommodates the heart

• Left lung – separated into upper and lower lobes by the oblique fissure– smaller than the right lung

• Right lung – separated into three lobes by the oblique and horizontal fissures

• There are 10 bronchopulmonary segments in each lung


Gross Anatomy of Lungs• Base, apex (cupula), costal surface, cardiac notch• Oblique & horizontal fissure in right lung results in 3 lobes• Oblique fissure only in left lung produces 2 lobes


Mediastinal Surface of Lungs

• Blood vessels & airways enter lungs at hilus• Forms root of lungs• Covered with pleura (parietal becomes visceral)


Blood Supply to Lungs

• Lungs are perfused by two circulations: pulmonary and bronchial

• Pulmonary arteries – supply systemic venous blood to be oxygenated– Branch profusely, along with bronchi– Ultimately feed into the pulmonary capillary

network surrounding the alveoli• Pulmonary veins – carry oxygenated blood from

respiratory zones to the heart


Blood Supply to Lungs

• Bronchial arteries – provide systemic blood to the lung tissue– Arise from aorta and enter the lungs at the hilus– Supply all lung tissue except the alveoli

• Bronchial veins anastomose with pulmonary veins

• Pulmonary veins carry most venous blood back to the heart

Pleura and Pleural Cavities• The outer surface of each lung and the

adjacent internal thoracic wall are lined by a serous membrane called pleura.

• The outer surface of each lung is tightly covered by the visceral pleura.

• while the internal thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm are lined by the parietal pleura.

• The parietal and visceral pleural layers are continuous at the hilus of each lung.

Pleural Cavities The potential space between the serous

membrane layers is a pleural cavity. • The pleural membranes produce a thin,

serous pleural fluid that circulates in the pleural cavity and acts as a lubricant, ensuring minimal friction during breathing.

• Pleural effusion – pleuritis with too much fluid

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Respiratory system