Basic Pulmonary Anatomy

Dr. Mohanad

Lung is porous, highly elastic and spongy

It crepitates on touch and floats on water

Color : -In new born it is rosy pink -Becomes darker slat grey due to

deposition of carbonacious particles

Lungs

Lungs Located within the thoracic cavity, surrounded by the double-layered pleural membrane –

parietal pleura – lines cavity wall

visceral pleura – covers the lungs

Lungs- Anatomical Features

Apex – extends 1” above clavicle

Base – rests on diaphragm

Right lung Left

lung

Superior lobe

Middle lobe

Inferior lobe

Horizontal fissure

Oblique fissure

Superior lobe

Inferior lobe

Oblique fissure

Cardiac notch

Hilum – at medial surface; where primary bronchus, pulmonary artery & veins enter/exit lung

Hilum

Cardiac notch of Lt. lung

Lung – medial surfaceGroove for aorta

Right lung

Upper lobeMiddle lobeLower lobe

Left lung

Upper lobeLower lobe

Right lung Left lung

Each lung has a primary bronchus entering at the Hilus.

Each lobe of a lung has a secondary (a.k.a. lobar) bronchus

Lobes are functionally divided into bronchopulmonary segments & each segment has a tertiary (segmental) bronchus

Segments are functionally divided into many lobules & each lobule receives a terminal bronchiole

Airways within Lungs

  Trachea Bronchus Tertiary bronchus Bronchiole Respiratory bronchiole

Epithelium Pseudostratified

Columnar Cuboidal

Goblet cells +++ ++ ++ + Absent

Clara cells Absent Absent Absent + +

Muscularis mucosae Absent + ++ +++ +++

Mucous glands +++ ++ + Absent Absent

Cartilage +++ ++ + Absent Absent

Alveoli Absent Absent Absent Absent +

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

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 200-300 million in a normal lung Between 75 µ to 300 µ in diameter- Total area-

75 square meters Most gas exchange takes place at alveolar-

capillary membrane

85-95% of alveoli covered by small pulmonary capillaries

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

Alveoli are expanded chambers of epithelial tissue that are the exchange surfaces of the lungsMultiple alveoli usually share a common alveolar duct, creating “alveolar sacs”

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

Alveolar Sac

Alveolar epithelium Two principle cell types:

Type I cell, squamous pneumocyte

Type II cell, granular pneumocyte

Type I Cell (Pneumocytes) 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 Preventing leakage of blood from

capillaries to the alveolar lumen Form Blood Air barrier

Type I Pneumocytes

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 pneumocytes

Also known as Septal cells Rounded or cuboidal secretory cells with microvilli Secretory granules are made of several layers- Multilamellar

bodies. Is constantly renewed. Pulmonary Surfactant – is the fluid secreted that spreads

over the alveolar surface.

Pulmonary Surfactant

Surfactant contains phospholipids, proteins and glycosaminoglycans, reduces the surface tension and prevents collapse of the alveolus during expiration.

The reduced surface tension in the alveoli decreases the force that is needed to inflate alveoli during inspiration.

Therefore surfactant stabilizes the alveolar diameters, facilitates their expansion and prevents their collapse by minimizing the collapsing forces.

Surfactant also has bactericidal properties

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

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

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

Respiratory Membrane

Respiratory membrane Alveolar wall – type I and type II alveolar cells Epithelial basement membrane Capillary basement membrane Capillary endothelium Very thin – only 0.5 µm thick to allow rapid diffusion of

gases Permit gas exchange by simple diffusion

Components of Alveolus

Blood Air Barrier

Consist of a thin layer of surfactant Basement membrane of Pneumocytes I Basement membrane of capillary endothelial cell

It exists to prevent air bubbles form forming in the blood, and from blood entering alveoli

Nutrition of the lung

The lung gets nutrition from two sources:

1.Conducting part up to the beginning of respiratory bronchiole is supplied by Bronchial artery

2. Respiratory part is supplied by pulmonary artery via Pulmonary capillary plexus

•Primary purpose is to deliver blood to lungs for gas exchange

•Right lung has one bronchial artery and left lung has two Bronchial artery

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 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, not in the walls of the alveoli.

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

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

Thank You