Dr. Nabil Khouri MD, MSc. Ph.D

Respiratory system

Lung

Conducting portion

INTRAPULMONARY

BRONCHI

BRONCHIOLES

TERMINAL

BRONCHIOLES

Respiratory portion

RESPIRATORY

BRONCHIOLES

ALVEOLAR DUCTS

ALVEOLI

Airways – conducting

portion

Nasal cavity

Pharynx (naso – oro –

laringo-)

Larynx

Trachea

Bronchi (extra

pulmonary)

Conducting portion

Nasal Cavity

Nasal cavity composed of three

regions( vestibule, respiratory

and olfactory regions)

Anterior portion – Vestibule:

vibrissae – skin - sebaceous +

sweat glands

Posterior aspect – nasal fossae:

conchae (sup, mid, inf), olfactory

region,

arterial plexuses and venous sinuses

bleeding

Vestibule

Anterior portion of nasal cavity near of the

nares dilated and known as the vestibule

lined with skin and has short, stiff hairs named VIBRISSAE that prevent large dust particles to enter

It is made of Keratinized stratified squamous epithelium

And Non Keratinized stratified squamous epithelium

Dermis houses numerous sebaceous glands

Posterior aspect of Nasal cavity

Is lined by Pseudostratified ciliated columnar epithelium

(RESPIRATORY EPITHELIUM)

Cellular content of the respiratory epithelium

Ciliated columnar cells: Most common, each cell has about 300

cilia

Goblet cells: Secret mucous (Found in frequency)

Brush cells: Have short microvilli, nerve fibers, sensory function

Basal cells: Are rounded STEM CELLS that located near basal

lamina and show mitotic figures

Small granule cells

Nasal Cavity

The Lamina Propria

(Subepithelial CT)

Mucous Glands Serous Glands Venous Sinuses lymphoid elements

CT Lamina Propria Is richly vascularized,

containing large arterial plexuses and venous sinuses, many

Secretions of nasal mucosa - Bactericides - Lysozymes

Olfactory region The olfactory epithelium

Lamina propria (serous secreting BOWMAN’S GLANDS (Boumans GL) a rich vascular plexus and many axons arising from olfactory cells of the olfactory epithelium)

olfactory epithelium comprises three types of cells:

Olfactory cells olfactory cells are bipolar neurons whose apical aspect (dendrite) is modified to form a bulb known as olfactory vesicle

Sustentacular cells (Supporting Cells)

• Cells that has a striated border composed of microvilli, and

secretory granules

• They provide physical support, nourishment

Basal cells

• Are short basophilic cells

• Their apical aspects do not reach the epithelial surface

they proliferate and replace both two other cells

Olfactory

Epithelium

(Sustentacular cells)

(bipolar neurons)

Transition between the Naso and the Oro-

pharynx

The naso-pharynx

The upper part of the pharynx which –

Anteriorly is open into the nasal cavity through posterior

nares,choana!

Posteriorly and laterally is surrounded by the muscular tissue

caudally is continued with the oropharynx and larynx

the epithelium of the pharynx is PSEUDOSTRATIFIED

CILIATED COLUMNAR

goblet cells and small glands (mucous, serous and mixed)

Accumulations of lymphatic tissue

pharyngeal tonsil – posteriorly

Tubal tonsils – laterally both are found in the lamina propria

The middle layer of the pharynx is of muscular character

being formed by bundles of the striated muscles

Pharynx Oro-pharynx

It is lined by a STRATIFIED SQUAMOUS NON-KERATINIZING

TYPE OF EPITHELIUM and lacks both muscularis mucosae and

submucosa.

The epithelium rests on a lamina propria that contains a thick layer of

longitudinally oriented elastic fibers that appear dark, glassy red located

near the underlying muscularis externa.

Lamina propria – loose-dense irregular CT

Vascularized

Seromucous gland: Mucous glands seen in this muscular layer in some

of our glass slides are the extensions of those present in the lamina

propria.

Lymphoid tissue – posterior: pharyngeal tonsil

Skeletal muscle-epimysium

The muscularis externa is composed of somewhat irregularly arranged

skeletal muscle, the longitudinal and constrictor muscles of the pharynx.

Larynx – voice box Additional function:

Phonation

Prevent food/drinks – respiratory system

Tube : cartilage (hyaline, elastic) – ligaments – skeletal muscles

(intrinsic-extrinsic)

Epiglottis – elastic cartilage

Stratified squamous non keratinized epithelium

Pseudostratified (respiratory epithelium)

Vestibular fold – false vocal cord (superior)

Vocal fold - true vocal cord (inferior) - stratified squamous

Vocalis muscle

vocal ligament – regular dense elastic CT

is an elastic cartilage of larynx

It is lined by stratified squamous epithelium on lingual surface

Pseudostratified ciliated columnar epithelium lined the laryngeal side

Serous and mucous glands located in lamina propria

Epiglottis

Trachea–extrapulmonary bronchus

Mucosa

Respiratory epithelium – Pseudostratified ciliated columnar

epithelium: goblet, cilated columnar, basal, brush, serous, DNES

cells

Lamina propria – loose fibroelastic-mucous, seromucous gl-

lymphoid tissue --elastic lamina

Submucosa-dense irreg. fibroelastic CT, mucous-

seromucous gl- lymphoid tissue

Adventitia – fibroelastic CT - C ring hyaline cartilage (p

cartilaginea) – fibrous CT – smooth muscle (p.

membranacea)

Lamina propria

composed of loose fibroelastic CT, contain seromucous glands and lyphoid elements, elastic lamina separate this layer from submucosa

Submucosa

Subnucosa is composed of dense irregular fibroelastic CT that houses mucous and seromucous glands, rich in blood and lymph supply

Adventitia

Adventitia is a fibroelastic CT that houses C-shaped hyaline cartilage, at posterior aspect of cartilage, there is a dense band of smooth muscle cells known as trachealis muscle

Trachea • The Mucosa

• Respiratory epithelium composed of 6 cell types located on a thick basement membrane

• Goblet cells are about 30% of cells, produce mucinogen

• Ciliated columnar cells about 30% of cells, are tall which have cilia and microvilli

• Basal cells are also about 30% of cells, they are undifferentiated stem cells

• Brush cells are just 3% of cells, they are narrow columnar cells that their function is unknown, but nerve ending associated with them

• Serous cells are about 3% of cells, they are columnar and have serous granule

• DNES cells, constitute about 3-4% of cells, have numerous granule in basal cytoplasm which is contain various pharmacological agents

Lung

Intrapulmonary bronchus

(2ndary -3tiary: lobe –

broncho pulmonary segment)

Mucosa –folded app

Respiratory epithelium

L propria – fibroelastic-

seromucous gl-lymphoid

nodules

--Smooth muscles-spiral

Submucosa-seromucous

gl-lymphoid nodules

Adventitia – plates of

cartilage (hyaline)

Bronchioles

Mucosa

Pseudostratified columnar

epithelium- goblet cells

ciliated simple columnar

ciliated cuboidal (with

Clara cells)

Lamina propria

No glands

Elastic fibers

Smooth muscles – helical

loose meshwork –

surrounded by fibroelastic

CT

Bronchial Tree

is composed of:

2 primary bronchus that enter lungs

3 lobar ( secondry) bronchus on right and 2 on the left

Segmental (tertiary) bronchus

bronchioles

Terminal bronchioles

Respiratory bronchioles

Progressively airways decreased in size and cartilage, glands,

goblet cells, and the height of epithelial cells

But increase smooth muscle cells and elastic tissue

Primary Bronchi

(Extrapulmonary)

Primary bronchi is

identical to trachea,

but have smaller

diameter and thinner

wall

Cartilage is in form

of irregular plates

Smooth muscle

located between

lamina propria and

submucosa as 2

distinct layers

PB

Bronchioles have no any cartilage or glands but have few Goblet cells In larger bronchioles epithelium is simple columnar ciliated, with

occasional goblet cells In smaller bronchioles epithelium change to Simple cuboidal,

with no goblet cells Bronchioles have a smooth muscle coats surrounded by

fibroelastic connective tissue

Terminal bronchioles are terminus of conducting portion they are lined by cuboidal cells(some with cilia) and Clara cells which have

domed apical surface Lamina propria is a fibroelastic CT, 1-2 layer of smooth muscle cells separate it from

adventitia

CLARA CELLS ( exocrine bronchiolar cells) • Clara cells are columnar with dome-shaped apex • Secretory granules which secret glycoproteins and surfactant-like materials • degrade toxins(SER) • divide to replace other cells • antimicrobial peptide

Terminal Bronchiole

Respiratory Bronchioles

are a transitional zone

between conducting and

respiratory tissues

Alveoli branching from their

walls

are lined by ciliated cuboidal

epithelium with Clara cells

that change to type I alveolar

cells

Smooth muscle cells and

elastic fibers underlie

epithelium

Respiratory Bronchiole

Alveolus Small air sac - gas exchange

Between alveoli – interalveolar septum – alveolar pores

Connective tissue: elastic, reticular (coll III) – lymphoid tissue

Macrophages, fibroblast, myofibroblast, mast cells

Continuous capillary bed (from pulmonary artery vein)

Both side

Type I Pneumocytes/alveolar cells - squamous alveolar cells) –

tight junction – basal lamina – very thin region permeable to

gasses

Type II Pneumocytes/alveolar cells - great alveolar cell – septal

cells – surfactant – surface tension↓ ≠ collapse

Alveolar walls & Alveolar cells

Cells of the Alveolar Septa

Endothelial cells are nonfenestrated with a thin dark nucleus, and

pinocytotic vesicles

Type I squamous cells that cover most of alveolar surface area, they have

pinocytotic vesicles

Type II (greater alveolar) cells are cuboidal, located on alveolar surface

where septa intersect, they have foamy cytoplasm, surfactant granules

(reduces surface tension to keep alveoli open during expiration)

Alveolar macrophages that are known as dust cells

Interstitial cells consist of fibroblasts and mast cells

Elastic & reticular fibers

•95% of the alveolar surface is composed of the simple squamous cells which are known as type I pneumocytes

•occluding junction attaches to other cells

•have basal lamina,

•alveolar pore formed by fusion of two adjacent type I cells

Type I pneumocytes (Squamus alveolar cells)

Type II pneumocytes (Septal cells)

•They are more numerous than type I

•cover just 5% of the alveolar surface

• located among type I cells, cuboidal with dome-shaped apical

•Located where adjacent alveoli separated by septum

•They have an abundance of RER, developed golgi complex, their lamellar bodies contain pulmonary surfactant

Type I Pneumocytes

Type II Alveolar or Type II pneumocytes

Also known as Septal cells

Rounded or cuboidal

secretory cells with

microvilli

Secretory granules are

made of several layers-

Multilamellar bodies.

These lamillar bodies are

cytoplasmic inclusions

made up of phospholipid

which combines with other

chemicals to form

surfactant & then ooze out

of the cell by exocytosis.

Pulmonary Surfactant – is

the fluid secreted that

spreads over the alveolar

surface

These cells can multiply to

replace damaged cells.

Surfactant also has

bactericidal properties

Type I and II Pneumocytes, capillaries and Dust

cells

Alveolar Macrophages or Dust cells Derived from Monocytes

and are part

mononuclear

phagocytic system.

Either seen in the septa

or alveoli

Cytoplasm contains

phagocytosed inhaled

carbon and dust

particles

Inhaled carbon and dust

particles are passed on

to them from

pneumocyte I through

pinocytic vesicles

Alveolar

Macrophages or

Dust cells

Migrate from septum to

alveolar surface and are

carried to the pharynx

through sputum

Main function is to clean

the alveoli of invading

microorganisms and

inhaled particulate matter

by phagocytosis

Trachea Bronchus Tertiary bronchus Bronchiole Respiratory

bronchiole

Epithelium Pseudostra

tified

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 +