Segmental Anatomy of Lungs ,

Anatomy of Mediastinum and

Secondary Lobule

Gamal Rabie Agmy, MD, FCCP

Professor of chest Diseases,

Assiut university

There are approximately 23

generation of dichotomous

branching From trachea to the

alveolar sac

HRCT can identify upto 8th order

central bronchioles

An

App

An

Ap

P App = Apicoposterior

An = Anterior

P = Posterior

1 1

2

3

2

&

3

Upper lobe

Lower lobe

An

App

SL

Ap

P An SL

SL = Superior LL

An = Anterior

App = Apicoposterior

P = Posterior

1 1

4 4

Middle lobe Lower lobe

Lingula Lower lobe

SL

S

I

L

M

SL

AN P L AN

L,M P

SL = Superior LL

AN = Anterior LL

P = Posterior LL

L,M = Lateral, Medial LL

7 6 5

8

9 9

10 10

11 11

12

M 44Y with malignant liver F 45Y with post irradiation changes after radical mastectomy

Atelectasis in the middle lobe Post irradiation scarring in

the right upper lobe

35Y male with fever and expectoration

Pneumonic consolidation in the left upper lobe

45Y male with chest pain and hemoptysis

Bronchogenic carcinoma in the left lower lobe

43Y male with acute chest pain and hemoptysis

Multiple infarcts in the lingula as

well as the left lower lobe

Secondary lobule

• The secondary lobule is the basic anatomic

unit of pulmonary structure and function.

Interpretation of interstitial lung diseases is

based on the type of involvement of the

secondary lobule.

It is the smallest lung unit that is surrounded

by connective tissue septa.

It measures about 1-2 cm and is made up of

5-15 pulmonary acini, that contain the alveoli

for gas exchange.

Secondary lobule

Basic anatomic unit of pulmonary

structure and function.

1-2 cm and is made up of 5-15

pulmonary acini

Supplied by a small bronchiole

(terminal bronchiole) in the

center, that is parallelled by the

centrilobular artery.

Pulmonary veins and lymphatics

run in the periphery

Two lymphatic systems:

central network

peripheral network

• The secondary lobule is supplied by a small

bronchiole (terminal bronchiole) in the

center, that is parallelled by the

centrilobular artery.

Pulmonary veins and lymphatics run in the

periphery of the lobule within the

interlobular septa.

Under normal conditions only a few of

these very thin septa will be seen.

There are two lymphatic systems: a

central network, that runs along the

bronchovascular bundle towards the

centre of the lobule and a peripheral

network, that is located within the

interlobular septa and along the pleural

linings.

The terminal bronchiole in the center divides into respiratory bronchioli with acini that contain alveoli. Lymphatics and veins run within the interlobular septa

Centrilobular area

It is the central part of the secondary

lobule.

It is usually the site of diseases, that

enter the lung through the airways (

i.e. hypersensitivity pneumonitis,

respiratory bronchiolitis, centrilobular

emphysema ).

Centrilobular area in blue perilymphatic area in yellow

Perilymphatic area

Perilymphatic areais the peripheral part

of the secundary lobule.

It is usually the site of diseases, that are

located in the lymphatics of in the

interlobular septa ( i.e. sarcoid,

lymphangitic carcinomatosis, pulmonary

edema).

These diseases are usually also located in

the central network of lymphatics that

surround the bronchovascular bundle.

Raoof, S. , CHEST 2006; 129:805

40

A group of terminal bronchioles

41

Unit of lung (0.5-3 cm) Irregularly polyhedral Supplied by a group of terminal bronchioles and accompanying pulmonary arterioles surrounded by lymph vessels Demarcated by “interlobular septa”

pulmonary veins pulmonary lymphatics connective tissue stroma

Accompanying pulmonary arterioles

43

Surrounded by lymph vessels

44

Pulmonary veins

45

Pulmonary lymphatics

46

47

Connective Tissue Stroma

HRCT

PATTERN

INCREASED LUNG

ATTENUATION

LINEAR AND RETICULAR OPACITIES

NODULES AND NODULAR OPACITIES

PARENCHYMAL OPACIFICATION

consolidation

Ground glass

DECREASED LUNG

ATTENUATION

CYSTIC LESIONS, EMPHYSEMA, AND BRONCHIEACTASIS

MOSAIC ATTENUATION AND

PERFUSION

AIR TRAPPING ON EXPIRATORY

SCANS

49