Cui Dongmei. Atlas of Histology: with functional and clinical correlations. 1st ed

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CHAPTER 10

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Lymphoid System

195

Figure 10-14A. Spleen. H&E, 60

The spleen is a large lymphoid organ (about 140–180 g in

humans) located in the left superior quadrant of the abdomen

(Fig. 10-6). It is covered by a thick, dense connective tissue

(capsule), which extends into the organ to form trabeculae.

Trabeculae provide structural support for arteries and veins,

which supply the compartments (white and red pulp) of the

spleen. The spleen is not organized into a cortex and medulla as

are lymph nodes and the thymus but is divided into white pulp

associated with a central artery and red pulp associated with

a vein and venous sinusoids. Functions of the spleen include

(1) an immune component (white pulp) to activate lymphocytes

and promote antibody production by plasma cells, (2) ﬁ ltration

of blood and destruction of aged erythrocytes in red pulp, and

(3) serving as reservoir for erythrocytes and platelets.

Capsule

White pulp

Red pulp

White pulp

Red pulp

Trabeculae

Red pulp

Trabeculae

Red pulp

Germinal

center

Germinal

center

Marginal zone

Mantle

zone

Mantle

zone

Central

artery

Central

artery

Primary

follicle

Primary

follicle

PALS

Figure 10-14B. White pulp, spleen. H&E, 194; inset

748

White pulp and red pulp are the two basic components of the

spleen. White pulp is composed of a central artery, a PALS,

and a lymphatic nodule. The nodules with germinal centers are

secondary nodules (follicles) where B cells actively differentiate

into large cells (lymphoblasts and lymphocytes). The dark ring

region around the germinal center is the mantle zone where

small inactive B cells are hosted. The mantle zone stains dark

because of densely packed lymphocytes. The nodules without

the germinal centers are primary nodules, which contain most

of the inactive B cells. The region that surrounds the white

pulp is the marginal zone, which contains marginal sinuses.

(G, germinal center.)

Splenic

cord

Lymphatic

nodule

Splenic

cord

Lymphatic

nodule

Venous

sinuses

Venous

sinuses

Splenic

cord

Splenic

cord

Venous sinuses

Figure 10-14C. Red pulp, spleen. H&E, 256; inset 385

Red pulp (red because it is rich in blood) stains light and con-

tains splenic cords and venous sinuses that are ﬁ lled with blood.

Venous sinuses are discontinuous capillaries, which have large

lumens, incomplete basal laminae, and gaps between endothe-

lial cells. These special features allow blood cells to pass

through the capillary wall (see Fig. 9-14A,B). The splenic cord

is a framework of reticular tissue that contains B cells, T cells,

plasma cells, macrophages, and other blood cells. Macrophages

in the splenic cord often extend their processes into the lumen

of the sinuses to reach and engulf foreign substances, microbes,

and aged erythrocytes. The red pulp of the spleen also serves as

a reservoir for platelets (Fig 10-16).

Spleen

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Organ Systems

Lymphocytes

Macrophage

Lymphocytes

Macrophage

Luman of

central artery

Lumen of

central artery

Endothelial

cells

T cells

Endothelial

cells

Central artery

PALS

Central artery

PALS

Figure 10-15B. Periarterial lymphatic sheath, spleen. H&E stain, 564; insets

1,727

The central artery, which helps to maintain the lymphatic sheath, continues through

the white pulp and branches before supplying the marginal sinuses (capillaries). Its

distal branches supply the red pulp. The central artery carries lymphocytes into

the marginal sinuses in the marginal zone, where B cells encounter antigens. Naive

B cells become memory B cells and plasma cells, which produce antibodies. T cells

migrate to the central artery region and form multiple layers that surround that

artery to form the PALS. T cells interact with antigen-presenting cells (inset shows a

macrophage) and receive antigens. Active T cells undergo proliferation to increase

their population (Fig. 10-5A).

Figure 10-15A. Splenic circulation.

The splenic artery enters the spleen at the hilum and

branches into trabecular arteries, which follow the

trabeculae into the white pulp where they become the cen-

tral artery. Lymphatic tissue that immediately surrounds

the central artery is called the PALS. The central artery

passes through the white pulp and gives rise to two routes

of capillaries: (1) those which supply sinuses (marginal

sinuses) around the lymphatic nodule; (2) those which

supply sinuses in the red pulp. The central artery leaves

the white pulp and forms several penicillar arterioles (not

surrounded by PALS). The branches of the penicillar arte-

rioles are called terminal arterial capillaries, which either

give rise directly to the splenic sinuses (closed circulation)

or terminate as open-ended vessels within the splenic

cord of the red pulp (open circulation). Open circula-

tion allows blood passing through the splenic cord to be

ﬁ ltered by macrophages before the blood cells enter the

sinuses. The aggregation of the macrophages surround-

ing the terminal arterial capillaries is called the sheath of

macrophages or the Schweigger-Seidel sheath.

Open

circulation

Pulp

vein

Sheath of

macrophages

Macrophage

Splenic

cord

Splenic

sinuses

Penicillar

arterioles

Closed

circulation

Central

artery

Marginal

sinuses

Splenic nodule

Trabecular

artery and vein

Germinal

center

PALS

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197

Figure 10-16. Red pulp of the spleen. TEM, 7,100.

Part of the wall and lumen of a red pulp sinusoid is shown here along with some adjacent red pulp cord (cord of Billroth) on the left.

The plane of section through the sinusoid appears to be transverse to its long axis as indicated by the varying shapes and sizes of the

many proﬁ les of endothelial cells that make up this part of its wall. These cells have a fusiform three-dimensional shape, and their

long axis parallels that of the vessel. A few endothelial cells are cut through the nucleus, but many more show only small proﬁ les of

cytoplasm. The basement membrane of the endothelium is incomplete, and only a couple of pieces are visible here. In life, the formed

elements of blood squeeze between endothelial cells to move into and out of the red pulp cords. Macrophages, plasma cells, and all

types of blood cells and platelets are suspended in the reticular framework of the red pulp cord tissue.

Plasma cell

Sinusoid

lumen

Plasma cell

Sinusoid

lumen

Endothelial cells

Basement

membrane

Erythrocyte

Platelet

Macrophage

Lymphocyte

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Organ Systems

Organ Epithelium/

Capsule

Covering

Cortex and

Medulla

Cords and

Sinuses

B-cell Main

Region

T-cell Main

Region

Special Features (1)

and Functions (2)

Tonsils Incomplete

epithelium

and capsule

No No Primary and

secondary nodules

Outside of

the lymphatic

nodules

1. Epithelial covering

2. Promotes B cells to

proliferate and to

produce IgA; immune

defense against upper

respiratory infections,

where B and T cells

encounter foreign

antigens and initiate

immune response

Lymph

nodes

Capsule

(thin)

Cortex, paracortex,

and medulla

Medullary

cords and

medullary

sinuses

Primary and

secondary nodules

(most nodules

are secondary);

medullary cords

Paracortex 1. Afferent lymphatic

vessels and

subcapsular sinuses

2. Filter lymph and

recirculate both B

and T cells; provide

place for lymphocytes

to meet antigens and

start immune response

Thymus Capsule

(thin)

Cortex (without

lymphatic nodules);

medulla (with

Hassall corpuscles)

No No Cortex and

medulla

1. Epithelial reticular

cells and Hassall

corpuscles; no

lymphatic nodules

2. Development and

maturation of T cells

Spleen Capsule

(thick)

No, arranged in

white pulp and red

pulp

Splenic cords

and venous

sinuses

Secondary nodules

(splenic nodules)

PALS 1. Central arteries and

PALS

2. Red pulp ﬁ lters

blood, removes aged

erythrocytes, and

acts as a reservoir

for erythrocytes and

platelets; the white

pulp hosts B and T

lymphocytes, where

they meet antigens,

mature and prolif-

erate, and initiate

immune response

TABLE 10-2 Lymphoid Organs

SYNOPSIS 10-3 Pathological and Clinical Terms for the Lymphoid System

Lymphadenopathy ■ : Enlarged lymph nodes due to a variety of causes including lymphoma, infection, autoimmune disease,

medications, and metastatic disease (Fig. 10-9C).

Myalgia

■ : Muscle pain that may be caused by a variety of conditions including exercise, autoimmune disease, medications,

infections, and neoplasms (Fig. 10-9C).

Lymphoid hyperplasia

■ : A reactive proliferative process of lymphoid tissues, particularly lymph nodes, characterized by

enlarged follicles with abundant macrophages within the germinal center (Fig. 10-9C).

Reed-Sternberg cell

■ : Characteristic cell of classical Hodgkin lymphoma containing two nuclei or nuclear lobes, each with

a prominent nucleolus (Fig. 10-12C).

Waldeyer ring

■ : Lymphoid tissues of the nasopharynx including the palatine tonsils and pharyngeal tonsils (adenoids) that

may be an extranodal site of lymphoma development (Fig. 10-9B).

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199

Respiratory System

Introduction and Key Concepts for the Respiratory System

Figure 11-1 Overview of the Respiratory System

Figure 11-2 Orientation of Detailed Respiratory System Illustrations

Conducting Portion

Upper Respiratory Airway

Figure 11-3A Nasal Vestibule, Nose

Figure 11-3B,C Nasal Mucosa, Nose

Figure 11-4A,B Olfactory Mucosa, Nose

Figure 11-5A,B Epiglottis, Larynx

Figure 11-5C Clinical Correlation: Age Impact on the Epiglottis

Lower Respiratory Airway

Figure 11-6A,B Trachea

Figure 11-6C Trachealis Muscle, Trachea

Figure 11-7A,B Respiratory Epithelium

Figure 11-8A,B Secondary Bronchi

Figure 11-8C Tertiary Bronchus

Figure 11-9 Overview of the Bronchioles and Alveoli

Figure 11-10A,B Bronchioles, Lung

Figure 11-10C Clinical Correlation: Small Cell Neuroendocrine Carcinoma

Figure 11-11A Clara Cells, Terminal Bronchioles

Figure 11-11B Terminal Bronchiole, Lung

Respiratory Portion

Figure 11-11C Respiratory Bronchioles, Lung

Alveolar Ducts and Alveoli

Figure 11-12A Alveolus and Gas Exchange

Figure 11-12B Blood-Air Barrier

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Figure 11-13A,B Type I Pneumocytes

Figure 11-14A,B Type II Pneumocytes

Figure 11-15A,B Alveolar Macrophages

Figure 11-16A Clinical Correlation: Acute Respiratory Distress Syndrome

Figure 11-16B Clinical Correlation: Emphysema

Synopsis 11-1 Pathological and Clinical Terms for the Respiratory System

Table 11-1 Respiratory System

Synopsis 11-2 Structural Differences (from Upper to Lower Airway) in the Respiratory System

Introduction and Key Concepts

for the Respiratory System

The primary function of the respiratory system is to supply the

body’s need for oxygen and to give off carbon dioxide. Other

functions include maintaining homeostasis and a normal pH

and participating in the body’s immune defense against bacte-

rial and viral infections. Anatomically, the respiratory system

can be divided into an upper respiratory airway and a lower

respiratory airway. Functionally, the respiratory system can

be divided into a conducting portion for the transportation

of gases and a respiratory portion for gas exchange. The con-

ducting portion includes the upper respiratory airway and the

lower respiratory airway. These conducting airways include

the nasal cavity, pharynx, larynx, trachea, extrapulmonary and

intrapulmonary bronchi, bronchioles, and terminal bronchi-

oles. The respiratory portion includes the respiratory bronchi-

oles, alveolar ducts, alveolar sacs, and alveoli. The respiratory

muscles (skeletal muscles: external intercostal muscle and the

diaphragm) play an important role in producing the movement

of air into and out of the lungs. The sympathetic and para-

sympathetic nervous systems innervate the smooth muscle of

the bronchial tree as well as the mucous membranes and blood

vessels in the lungs. Sympathetic ﬁ bers cause bronchodilation

(relaxation of bronchial smooth muscles), whereas parasym-

pathetic ﬁ bers cause bronchoconstriction (contraction of bron-

chial smooth muscles).

Conducting Portion

Upper Respiratory Airway

The upper respiratory airway functions as a part of the con-

ducting portion; it consists of the nasal cavity, nasopharynx,

oropharynx, and larynx. In general, the conducting airway is

composed of bone, cartilage, and ﬁ brous tissue and is lined

with stratiﬁ ed squamous and ciliated pseudostratiﬁ ed columnar

epithelia moistened with mucus and other glandular secretions.

Cilia on the surface of the pseudostratiﬁ ed columnar epithelia

sweep particles out of the respiratory airway.

THE NASAL CAVITY is the ﬁ rst portion of the upper respira-

tory airway. It can be divided into three regions based on the

types of epithelial coverings. (1) The nasal vestibule is the most

anterior part of the nasal cavity and is covered by a keratinized

stratiﬁ ed squamous epithelium and vibrissae (stiff hairs); it is

continuous with a mucosa of nonkeratinized stratiﬁ ed squamous

epithelium (Fig. 11-3A). (2) The nasal mucosa region is covered

by pseudostratiﬁ ed ciliated epithelium (respiratory epithelium),

which contains ciliated columnar cells, goblet cells, basal cells,

and, occasionally, neuroendocrine cells (Figs. 11-3B and 11-7).

The goblet cells manufacture mucus, which traps particles

of dust and bacteria and moves them out of the nasal fossa,

sinuses, and the nasopharynx, with the help of the ciliary action

of the epithelium. Nasal mucosa ﬁ lters, warms, and moistens

the inhaled air. Mucus serves as a protective mechanism for pre-

venting pathogens and irritants from entering the respiratory

airway (Fig. 11-3B,C). There is a special vascular arrangement

in the lamina propria of the nasal conchae called swell bodies

(venous plexuses), which alternately ﬁ ll with blood from the

small arteries directly into the venous plexuses on each side of

the nasal cavity to help reduce air ﬂ ow and increase air contact

with nasal mucosa. (3) The olfactory mucosa region is located

in the roof of the nasal cavity and is covered by pseudostratiﬁ ed

columnar epithelium, which is composed of ciliated olfactory

cells (olfactory receptor neurons), nonciliated columnar cells,

and basal cells. It functions as a site for odorant chemorecep-

tion (Fig. 11-4A,B).

THE NASOPHARYNX AND OROPHARYNX conduct

air from the nasal cavity and oral cavity to the larynx. The

oropharynx is lined by stratiﬁ ed squamous epithelium, and the

nasopharynx is lined by respiratory (pseudostratiﬁ ed columnar)

epithelium (see Table 11-1). The nasopharynx contains sero-

mucous glands in the lamina propria. The pharyngeal tonsil, an

unencapsulated patch of lymphoid tissue, is located in the pos-

terior aspect of the nasopharynx (see Fig. 10-8A). The palatine

tonsils are located at the junction of the oral cavity and the oral

pharynx, between the palatoglossal and the palatopharyngeal

folds, which indicate the posterior boundary of the oral cavity

(see Fig. 10-8B). Tonsils, rich in lymphoid tissue, are the ﬁ rst

line of defense against many airborne pathogens and irritants.

Streptococcal pharyngitis is the most frequent bacterial upper

respiratory infection in children.

THE LARYNX conducts air from the pharynx to the trachea.

It is supported by a set of cartilages of complex shape and cov-

ered by a ciliated, pseudostratiﬁ ed respiratory epithelium. This

mucosa continues from that of the pharynx and extends to the

trachea. The larynx contains several structures, including the

epiglottis, vocal cords, and nine pieces of cartilage located in its

wall. The epiglottis is a thin leaﬂ ike plate structure; its central

cord contains a large piece of elastic cartilage. This cartilage is

attached to the root of the tongue and projects obliquely upward

behind the tongue and the hyoid body. The epiglottis stands in

front of the laryngeal inlet and bends posteriorly to cover the

inlet of the larynx when food is swallowed. The upper anterior

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201

surface of the epiglottis is covered by nonkeratinized stratiﬁ ed

squamous epithelium. In children, the epiglottis will occasion-

ally become infected with Haemophilus. In elderly individu-

als, the elastic cartilage of the epiglottis is often reduced in size

and is replaced by adipose tissue (Fig. 11-5C). The vocal cords

(folds), which contain striated skeletal muscle and ligaments

(mainly elastic ﬁ bers), are lined by thin nonkeratinized stratiﬁ ed

squamous epithelium, which is ﬁ rmly attached to the underlying

vocal ligaments. The stratiﬁ ed squamous epithelium protects the

vocal cords from mechanical stress. The main functions of the

vocal cords are to control airﬂ ow and facilitate speaking.

Lower Respiratory Airway

The lower respiratory airway includes the trachea, bronchi,

bronchioles, and terminal bronchioles. Each portion of the

lower respiratory airway has unique tissue components, which

facilitate oxygen delivery, gas exchange, and immune defense

mechanisms. Individual airways decrease in diameter as they

continue branching.

THE TRACHEA is a tube formed of cartilage and ﬁ bromus-

cular membrane, 10 to 12 cm long, with a diameter of 2 to

2.5 cm. It extends from the larynx, at the cricoid cartilage, to

the bifurcation of the bronchi. The trachea is lined by pseu-

dostratiﬁ ed ciliated columnar epithelium and reinforced by 10

to 12 C-shaped hyaline cartilage rings (Fig. 11-6). A band of

smooth muscle is located between the two ends of the C-shaped

cartilage. The epithelium is composed of several cell types

including goblet cells, ciliated columnar cells, basal cells, and,

occasionally, neuroendocrine cells, which are also called dif-

fuse neuroendocrine system (DNES) cells (Fig. 11-7A). Chronic

irritation of the epithelium will lead to an increase in goblet

cells and a transformation to a stratiﬁ ed squamous epithelium,

known as squamous metaplasia.

EXTRAPULMONARY BRONCHI are the primary bronchi,

which begin at the bifurcation of the trachea and lead to the

right and left lungs. They are called “extrapulmonary” bronchi

because they are positioned outside the lungs. They are structur-

ally similar to the trachea, are lined by respiratory epithelium

(pseudostratiﬁ ed columnar epithelium), and have C-shaped

hyaline cartilage. The left primary bronchus is narrower and

less vertical than the right one and gives rise to two second-

ary (lobar) bronchi. The right primary bronchus is wider and

shorter and more vertical than the left one; it gives rise to three

secondary (lobar) bronchi. That is the reason foreign body aspi-

ration occurs more often to the right lung.

INTRAPULMONARY BRONCHI are secondary and tertiary

bronchi. As the primary (extrapulmonary) bronchi enter the

hiluses of the lungs they become the secondary (lobar) bronchi,

which eventually divide into the tertiary (segmental) bronchi

(Figs. 11-1 and 11-8C). They are lined by respiratory epithe-

lium, and the bronchial glands (seromucous glands) are found

in the submucosa. A band of spiral smooth muscle separates

the lamina propria and submucosa of the intrapulmonary bron-

chi. The skeletal support for each intrapulmonary bronchus is

provided by several hyaline cartilage plates instead of C-shaped

cartilage rings. As the bronchi continue branching, there is a

decrease in airway diameter and in the amount of cartilage in

their walls. The number of goblet cells, glands, and the height

of epithelial cells also decrease. However, the airways tend to

have increased amounts of smooth muscle and elastic tissues.

Smooth muscle in the bronchi is innervated by the sympathetic

and parasympathetic nervous systems. In patients with asthma,

this smooth muscle thickens with hyperplasia and hypertrophy

and undergoes extensive and prolonged contraction causing

reduction in airway luminal diameter and difﬁ culty in exhaling

and inhaling. Bronchial branches are accompanied by branches

of the pulmonary arteries, pulmonary veins, nerves, and lymph

vessels. These structures usually travel in intersegmental and

interlobar layers of connective tissue.

BRONCHIOLES are smaller airways deriving from tertiary

bronchi, which continue to branch into terminal bronchioles

(Fig. 11-9). Bronchioles have no cartilage in their walls. Large

bronchioles are lined with ciliated columnar epithelial cells and

a gradually decreasing number of goblet cells. Small bronchioles

are covered with ciliated cuboidal epithelial cells and with Clara

cells. The number of Clara cells is greatly increased in the ter-

minal bronchioles (Fig. 11-11A). Terminal bronchioles are the

smallest and last of the conducting portion of the respiratory

system and they have no gas exchange function. Terminal bron-

chioles give rise to respiratory bronchioles, which connect to the

alveolar ducts, alveolar sacs, and alveoli (Fig. 11-11A,B).

Respiratory Portion

The respiratory portion of the lungs includes the respiratory

bronchioles, alveolar ducts, alveolar sacs, and alveoli. This por-

tion of the respiratory system does not have cartilage and has

gradually increasing numbers of alveoli.

Respiratory Bronchioles

Respiratory bronchioles are lined by cuboidal epithelium and

are interrupted by pouchlike, thin-walled structures called alve-

oli. Alveoli function in gas exchange. Respiratory bronchioles

continue to branch to become alveolar ducts (Figs. 11-9 and

11-11C).

Alveolar Ducts and Alveoli

Alveolar ducts arise from respiratory bronchioles. They have

more alveoli and some cuboidal epithelium on the walls as

compared to respiratory bronchioles. They terminate as blind

pouches with clusters of alveolar sacs. An alveolar sac is com-

posed of two or more alveoli that share a common opening.

Alveolar ducts and alveoli are rich in capillaries, which make

gas exchange more efﬁ cient. Alveoli are thin-walled pouches,

which provide the respiratory surface area for gas exchange

(Figs. 11-9 and 11-11C). The wall of the alveolus is formed by

a delicate layer of connective tissue with reticular and elastic

ﬁ bers covered by type I and type II pneumocytes. The type I

pneumocytes lie on a basal lamina, which is fused with the basal

lamina surrounding the adjacent capillaries to form a blood-

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air barrier. The blood-air barrier is an important structure for

oxygen and carbon dioxide exchange (Fig. 11-12A,B). The

neighboring alveoli are separated by alveolar septa, which con-

tain elastic connective tissue and may have capillaries within

them. The lumina of the neighboring alveoli may be connected

to each other by small alveolar pores.

TYPE I PNEUMOCYTES are also called type I alveolar cells.

These cells cover 95% to 97% of the alveolar surface, whereas

type II pneumocytes cover the rest of the surface. Type I pneu-

mocytes are squamous cells with a ﬂ at, dark, oval nucleus.

Tight junctions between type I pneumocytes help prevent move-

ment of extracellular ﬂ uid into the alveolar sacs. Type I pneu-

mocytes are unable to divide; however, they can be regenerated

from type II pneumocytes (Fig. 11-13A,B).

TYPE II PNEUMOCYTES cover about 3% to 5% of the alve-

olar surface and form tight junctions with type I pneumocytes.

Their cytoplasm contains numerous characteristic secretory

lamellar bodies, which are mainly composed of phospholipids

and proteins. These components can be released by exocytosis

into the alveolar lumen to form a thin ﬁ lm of pulmonary sur-

factant. The function of the pulmonary surfactant is to increase

pulmonary compliance and decrease surface tension of the alve-

oli to prevent them from collapsing. Type II pneumocytes can

undergo mitosis to regenerate and also can form type I pneumo-

cytes. The pulmonary surfactant is recycled by type II pneumo-

cytes or cleared by alveolar macrophages (Fig. 11-14A,B).

ALVEOLAR MACROPHAGES are also called dust cells. They

originate in bone marrow and circulate in blood as monocytes.

They become mature and migrate into the connective tissue of

the alveolar septa and into the lumina of the alveoli from blood

capillaries. They move around on the epithelial surfaces and

help to clear particles, as well as excessive surfactant, out of the

respiratory spaces (Fig. 11-15A,B).

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Figure 11-1. Overview of the respiratory system.

The respiratory system plays the essential role of supplying oxygen to the body. It can be divided into the upper respiratory airway

and lower respiratory airway; functionally, the respiratory system can also be divided into a conducting portion and respiratory por-

tion. Upper respiratory airway infection is a common term in clinical diagnosis. The upper respiratory airway consists of the nasal

cavity, nasopharynx, oropharynx, and larynx. There are three regions in the nasal cavity classiﬁ ed according to types of epithelial

covering: the nasal vestibule (stratiﬁ ed squamous epithelium), the nasal mucosa (ciliated pseudostratiﬁ ed columnar epithelium), and

the olfactory mucosa (specialized olfactory epithelium). The nasopharynx is continuous with the oropharynx and extends to the

larynx. The larynx is composed of the epiglottis, vocal cords (folds), and a set of cartilages of complex shape. The lower respiratory

airway consists of the trachea, bronchi, bronchioles, and alveoli in the lungs. The skeletal support changes from C-shaped hyaline

cartilage in the trachea and primary bronchi to cartilage plates in secondary and tertiary bronchi. Bronchioles have no cartilage

support. Terminal bronchioles give rise to respiratory bronchioles. which have the function of gas exchange along with the alveoli

(see Fig. 11-9).

Structures of the Respiratory System

I. Conducting portion

A. Upper respiratory airway

1. Nasal cavity

a. Nasal vestibule

b. Nasal mucosa

c. Olfactory mucosa

2. Nasopharynx

3. Oropharynx

4. Larynx

a. Epiglottis

b. Vocal cords (folds)

B. Lower respiratory airway

1. Trachea

2. Extrapulmonary bronchi (primary bronchi)

3. Intrapulmonary bronchi

a. Secondary bronchi

b. Tertiary (segmental) bronchi

c. Bronchioles

d. Terminal bronchioles

II. Respiratory portion

A. Respiratory bronchiole (respiratory portion begins)

B. Alveolar ducts and alveoli

C. Type I and II pneumocytes

D. Alveolar macrophages

Vestibule

Bronchioles

Nasal mucosa

Nasopharynx

Oropharynx

Extrapulmonary

(primary) bronchus

Larynx

Intrapulmonary

(secondary) bronchus

Intrapulmonary

(tertiary) bronchus

Alveoli

Epiglottis

Trachea

Olfactory

mucosa

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Figure 11-2. Orientation of detailed respiratory system illustrations.

Fig. 11-6A,B,C

Fig. 11-7A,B

Fig. 11-3A

Fig. 11-5A,B,C

Fig. 11-4A,B

Fig. 11-3B,C

Fig. 11-8A,B

Fig. 11-8C

Fig. 11-9

Fig. 11-10A to

Fig. 11-15B

Structures of the Respiratory System with Figure Numbers

Nasal vestibule

Figure 11-3A

Nasal mucosa

Figure 11-3B

Figure 11-3C

Olfactory mucosa

Figure 11-4A

Figure 11-4B

Epiglottis

Figure 11-5A

Figure 11-5B

Figure 11-5C

Trachea

Figure 11-6A

Figure 11-6B

Figure 11-6C

Figure 11-7A

Figure 11-7B

Bronchi

Figure 11-8A

Figure 11-8B

Figure 11-8C

Overview of bronchioles and alveoli

Figure 11-9

Bronchioles

Figure 11-10A

Figure 11-10B

Figure 11-10C

Figure 11-11A

Figure 11-11B

Figure 11-11C

Alveoli, type I and II pneumocytes, and macrophages

Figure 11-12A

Figure 11-12B

Figure 11-13A

Figure 11-13B

Figure 11-14A

Figure 11-14B

Figure 11-15A

Figure 11-15B

Figure 11-16A

Figure 11-16B

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