Basic Pulmonary Anatomy

The Upper and Lower Airways

Respiratory System

Upper Airways

Nose Paranasal sinuses Pharynx

The Functions of the Nose

Filter the air Humidify the air Warm the air Site for sense of

small To generate

resonance in speech

The Nose

Rigid structure composed of cartilage and bone

Septal cartilage divides nasal cavity into two nasal fossae

Palate divides nasal cavity and oral cavity

Nose divided into 3 regions

Nasal structure

Nares and Nasal Cavity

Regions of the nose Nares or nostrils serve as opening

for the nasal fossae—two cavities in middle of the face

Vestibule/vestibular regionVestibule/vestibular region Lined with stratified squamous

epithelium Contain vibrissae-nasal hair, first

line of defense, function to filter inspired air

Sagital section of the head

Nasal regions

Vestibular area contains sebaceous glands; secrete sebum

Keeps vibrissae soft and filter gases

Olfactory regionOlfactory region: pseudostratified columnar epithelium and olfactory cells

Regions of the nose Respiratory—highly vascular;

ciliated, pseudostratified columnar epithelium Contains turbinates or conchae;

increase surface area (166 cm2) for humidification, heating/cooling and filtering of air

Mucous membranes provide up to 650-1000 ml of water/day to humidify air

Respiratory region of nose

Goblet cells in mucus membrane secrete 100 ml/day of mucous; aids in trapping inspired particles and prevents them from entering lower respiratory trace

Each columnar cell contains 200-250 cilia; beat in waves toward oropharynx (mouth), 2cm/min

Sinuses

Air-filled cavities within the skull (cranium)

Aka paranasal sinuses (four pairs) Function not clear, lighten head and

provide voice resonance Lied with pseudostratified cliated

columnar epithelium and goblet cells

Paranasal Sinuses

Oral Cavity

Alternate respiratory passage Anterior 2/3 of tongue located in

oral cavity Another “respiratory” muscle Lined with stratified squamous

epithelium

+Pharaynx (Throat), hollow, upper portion of

the airway and the digestive tract Subdivided into: nasopharynx,

oropharynx, laryngopharynx

Nasopharynx Pseudostratified ciliated columnar

epithelium

Pharynx

Nasopharynx

Filters bacteria and foreign particles from inspired air

Carries this to the stomach Eustachian tube and auditory tube

open into lateral surfaces, connect nasopharynx to middle each, equalizes pressure of middle ear

Nasopharynx

Oropharynx

Between soft palate above and base of tongue below

From tip of uvula to epiglottis Stratified squamous epithelium Gas conduction, filtering of air Defense mechanism: gag reflex

Oropharynx

Laryngopharynx

Stratified squamous epithelium Gas conduction Connecting zone between upper

and lower airway (vocal cords and below)

Lower Airway Begins with true

vocal cords and extends to alveoli

Larynx Trachea Main stem bronchi Segmental bronchi Subsegmental

bronchi

Bronchioles Terminal

bronchioles Respiratory

bronchioles Alveolar ducts Alveolar sacs alveoli

Larynx Lies between base of tongue and

trachea Protrusion is the thyroid cartilage,

aka “Adam’s apple.” Houses the vocal cords, primary

use is vocalization Connection point-upper and lower

airways

Larynx

Larynx Extends from C3

to C6 Pseudostratified

ciliated columnar epithelium

Functions: Free flow of air to

the lungs

During inspiration, vocal folds abduct, move apart, and widen glottis

Valsalva maneuver and Muller maneuver

Larynx Composed of 3 single

cartilaginous structures:

Epiglottis-flap, swings down to meet larynx during swallowing

Thyroid-bulk of this forms larynx

Cricoid-circular, keeps head of trachea open

Larynx Posterior view

Epiglottis

Covers the rima glottidis during swallowing (glottis=cords & space)

Larynx has poor lymphatic drainge, prone to edema

Epiglottitis is a life-threatening condition (supraglottic croup), bacterial origin

Narrowest part of lower airway in adult

Glottis

Thyroid

Largest of the laryngeal cartilages Primary housing the vocal cords Inflammation below the vocal cords

known as laryngotracheobronchitis Croup Subglottic croup Viral orgins

Cricoid

A complete cartilaginous ring Narrowest portion of the lower

airway in a neonate and infant Actual start of the lower airway

Larynx – superior view

Tracheobronchial Tree Series of branching

airways commonly referred to a “generations” or “orders”

The first generation or order is zero (0), the trachea itself.

Bifucrates at the carina

Two Types of Airways Cartilaginous

-serve only to conduct air between external environment and the sites of gas exchange

Non-cartilaginous

-serve both as conductors of inspired air and as sites of gas exchange

Tracheobronchial Tree Dichotomous branching (daughter

branches) Airways become progressively

narrower, shorter, and more numerous

Cross-sectional area enlarges Common histology (at the nose) and

throughout until the bronchiole generation

Histology

Three major layers

Epithelial lining

Lamina propria

Cartilaginous layer

Histology

Tracheal lining

Pseudostratified columnar epithelium with cilia; goblet cells, serous cells, and specialized submucosal bronchial glands

200+ cilia per cell, 5-7 microns long

Beat cephalid (head) toward oropharynx

Tracheal Lining

Epithelial lining

Pseudostratified ciliated columnar epithelium is homogenous until the level of the bronchioles

Cilia disappear in terminal bronchioles

Cilia absent in respiratory bronchioles

Histology

Mucous blanket

Covers the epithelial lining Composed of

-95% water -glycoproteins Carbohydrate lipids DNA Cellular debris

Mucous

Mucus produced by Goblet cells

Found through terminal bronchiolesSubmucosal (bronchial) glands

extend into laminar propriaInnervated by vagus nerve

(parasympathetic)Produce 100 ml of secretions/dayDisappear at end of terminal bronchioles

Mucous Blanket Two distinct

layers Sol layer Gel layer

Cilia move through sol layer and strike gel layer propelling it toward mouth

At a rate of 2 cm/minute

Mucocilliary Escalator

Defense mechanism of lower airways

Mucus propelled up airway to larynx

Cough mechanism moves secretions into oropharynx via sheering forces

Mucociliary transport & cough

Factors Which Slow Mucocilliary Transport Cigarette smoke Dehydration Positive pressure

ventilation Endotracheal

suctioning High inspired

oxygen concentrations

Hypoxia Atmospheric

pollutants General

anesthesia Parasympatholyti

c drugs

Lamina Propria

Submucosal layer Contains loose fibrous tissue with

Tiny blood vessels Lymphatic vessels Branches of the vagus nerve Two sets of smooth muscle fibers

which continue/extend down to alveolar ducts

Lamina propria

Mast cells Found in lamina propria near

Branches of vagus nerve and blood vessels

Scattered throughout smooth muscle Loose connective tissue of skin and

intestinal mucosa Cell constituents of submucosal glands

Important part of humoral immune response (circulating antibodies) which defend against antigens

Mast Cells Release histamine

Cartilaginous Layer Outermost layer of

tracheobronchial tree Consist of

Trachea Mainstem bronchi Lobar bronchi Segmental bronchi Subsegmental bronchi

Trachea

10-12 cm long 1.5-2.5 cm wide Extends to second rib anteriorly

and T4-T5 posteriorly 15-20 C shaped rings

Main Stem Bronchi Right bronchus

Wider More vertical 5 cm shorter Supported by C

shaped cartilages 20-30 degree

angle First generation

Left bronchus Narrower More angular Longer Supported by C

shaped cartilages 40-60 degree

angle First generation

Lobar Bronchi R main stem

divides into: Upper lobar

bronchus Middle lobar

bronchus Lower lobar

bronchus

L main stem divides into: Upper lobar

bronchus

Lower lobar bronchus

Segmental Bronchi 3rd generation

R lobar divides into Segmental bronchi 10 segments on

right

L lobar divides into Segmental bronchi 8 segments on left

Subsegmental Bronchi

4th to 9th generations Progressively smaller airways 1-4 mm diameter At 1 mm diameter connective

tissue sheath disappears

Noncartilagenous Airways Bronchioles

10-th to 15th generation

Cartilage is absent Lamina propria is

directly connected with lung parenchyma

Surrounded by spiral muscle fibers

Epithelial cells are cuboidal

Less goblet cells and cilia

With no cartilage, airway remains open due to pressure gradients

Terminal Bronchioles

16th to 19th generation Average diameter is 0.5 mm Cilia and mucous glands begin to

disappear totally End of the conducting airway Canals of Lambert-interconnect this

generation,provide collateral ventilation

Gas exchange zone

Respiratory bronchioles Acinus (aka primary acinus; aka

primary lobule)—respiratory bronchioles to the alveoli

Ducts, sacs, alveolar Squamous epithelium

The Functional Units of Gas Exchange

Functional Units of Gas Exchange

Three generations of respiratory bronchioles

Three generations of alveolar ducts

15-20 clusters--sacs

Gas exchange terminology

All of the structures arising from a single terminal bronchiole are called Primary lobule Acinus Terminal respiratory unit Lung parenchyma Functional units

Acinus/Primary lobule

Respiratory bronchioles with some alveoli arising from their walls

Alveolar ducts arise from respiratory bronchioles--alveoli whose septal wall contain smooth muscle

Alveoli

Ca. 300 million alveoli Between 75 µ to 300 µ in

diameter

Most gas exchange takes place at alveolar-capillary membrane

Anatomic Arrangement of Alveoli

85-95% of alveoli covered by small pulmonary capillaires

The cross-sectional area or surface area is approximately 70m2

Acinus or Lobule

Each acinus (unit) is approximately 3.5 mm in diameter

Each contains about 2000 aveloli

Approximately 130,000 primary lobules in the lung

Acinus

Alveolar epithelium

Two principle cell types:

Type I cell, squamous pneumocyte

Type II cell, granular pneumocyte

Type I Cell

95% of the alveolar surface is made up of squamous pneumocyte cells

Between 0.1 µ and 0.5µ thick

Major site of gas exchange

Type II Cell

5% of the surface of alveoli composed of granular pneumocyte cells

Cuboidal in shape with microvilli Primary source of pulmonary

surfactant Involved with reabsorption of fluids

in the dry, alveolar spaces

Type II Pneumocyte

Pore of Khon

Small holes in the walls of adjoining alveoli (alveaolar septa)

Between 3 to 13 µ in diameter Formation of pores may be due to:

Desquamation due to disease Normal degeneration due to aging Movement of macrophages leaving

holes

Canals of Lambert/Pores of Kohn

Provide for collateral ventilation of difference acinii or primary lobules

Additional ventilation of blocked units

May explain why diseases spread so quickly at the lung tissue (paremchymal) level

Pores of Kohn

Alveolar macrophages

So-called Type III cell Remove bacteria and foreign

particles May originate as

Stem cells precursors in bone marro Migrate as monocytes through the

blood and into the lungs

Intersitium/interstial space

Surround, supports, and shapes the alveoli and capillaries

Composed of a gel like substance and collagen fibers

Contains tight space and loose space areas

Alveolar-Capillary Site--Interstitial Space

Interstitium Water content in loose space can

increase by 30% before there is a significant change in pulmonary capillary pressure

Lymphatic drainage easily exceeded Collagen limits alveolar distensibility Area of scarring, making for stiffer or

non-compliant lungs

Blood Supply to the Pulmonary System

Two Systems

Bronchial Blood Supply

Bronchial arteries From aorta to temrinal bronchioles

Merge with pulmonary arteries and capillaries

1% of total cardiac output (left ventricle)

Bronchial arteries

Also nourish Mediastinal lymph nodes Pulmonary nerves Some muscular pulmonary arteries

and veins Portions of the esophagus Visceral pleura

Bronchial venous system

1/3 blood returns to right heart Azygous Hemiazygous Intercostal veins

This blood comes form the first two or three generations of bronchi

Bronchial venous return 2/3 of blood flowing to terminal

bronchioles drains into pulmonary circulation via “bronchopulmonary anastomoses”

Then flows to left atrium via pulmonary veins

Contributes to “venous admixture” or “anatomic shunt” (ca. 5% of C.O.)

Pulmonary Vascular System

The second source of blood to the lungs

Primary purpose is to deliver blood to lungs for gas exchange

Also delivers nutrients to cells distal to terminal bronchioles

Composed of arteries, arterioles, capllaries, venules, and veins

Pulmonary Capillaries

Walls are les than 0.1µ thick Total external thickness is about

10µ Selective permeability to water,

electrolytes, sugars Produce and destroy biologically

active substances

Lymphatic System Lymphatic vessels

remove fluids and protein molecules that leak out of the pulmonary capillaries

Transfer fluids back into the circulatory system

Lymphatics

Lymphatic vessels arise within loose spaces of connective tissue

Vessels then follow bronchial airways, pulmonary airways, pulmonary arteries and veins to the hilum

Lymphatics

Vessels end in pulmonary and bronchopulmonary lymph nodes within and outside of lung parenchyma

Nodes acts as filters to keep particles and bacteria from entering the blood

Lymphatics Lymphatic vessels are not

in the walls of the alveoli.

Within the interstial spaces to help drain fluids and foreign materials.

More lymphatic vessels on surface of lower lobes than on upper and middle lobes (dependent portions)

Lymphatic vessels Thoracic duct

carries lymph fluid coming from tissues inferior to diaphragm and from left side of upper body

Eventually empties into left subclavian vein

Lymphatic vessels

Right lymphatic duct drains the right half of the body superior to the diaphragm

Empties into the right subclavian vein