Respiratory SystemRespiratory System

Prof. Ji-Cheng LiDepartment of Histology and Embryolo

gy

ObjectivesObjectives• Components of the conducting and respiratory

portions of the respiratory system.• Wall structure and key distinguishing features of the

trachea and the various segments of the bronchial tree.

• Structure of the alveolar wall and components of the gas-blood barrier.

• Structure of the type I, II alveolar cells.

Components• Nasal cavity• The pharynx (digestive

system)

• The larynx• The trachea • The bronchi• The lung

vestibular region

respiratory region

olfactory region

1.Nasal cavity (study by yourself)Ep: stratified squamous epi.

LP: sebaceous and sweat glandEp: pseudostratified ciliated columnar epi.

LP: vascular network

Ep: olfactory epi.

LP: serous gland (Bowman gland, olfactory gland)

Olfactory cellsSupporting cellsBasal cells

2. Trachea and main bronchi2. Trachea and main bronchi

Structure:

• Mucosa • Submucosa• Adventitia

(1) Mucosa(1) Mucosa : Epithelium : Epithelium

Pseudostratified ciliated columnar epithelium

• Ciliated cell• Goblet cell• Brush cell• Basal cell• Small granule cell

EpitheliumEpithelium

Figure 17-6: Ciliated respiratory epithelium

ciliated cell• with cilia • To provide a sweepin

g motion from the farthest reaches towards larynx

Goblet cell • to synthesize and

secrete mucus• the secretion covers

the epithelium surface

• Brush cell -columnar, microvilli, -EM: RER, no granules

-function: not very clear i. become into ciliated cell ii.receive sensory stimuli

• Small granule cell (neuroendocrine cell)

-EM: dense-core granules -Function: secret hormones to regulate c

ontract of SM and secretion of gland i. 5-hydroxytryptamine(serotonin) ii. Calcitonin

• Basal cell

stem cell

(2) Submucosa LCT, containing mixed glandswith diffuse LT and LN

SIg A = secretory component (secreted by epithelum cell) + Ig A ( produced by plasma cell)

(3) Adventitia: • cartilage ring: 16-20 “C ” shaped• circular ligament: elastic fiber• posterior part (membrane part): SM, elastic

fiber, tracheal gland

3. Lung3. Lung---paired organ,

located in thoracic cavity

General structure: ---capsule: visceral layer of pleura- serous

membrane

---parenchyma: all branches of bronchi and alveoli

---interstitia

Conducting portion: bronchi

→intrapulmonary bronchial tree

(lobar bronchial tree, segmental bronchi and small bronchi)

→ small bronchi→bronchioles →terminal bronchioles • Function: inspire air (cleaned,

moistened, warmed)

Respiratory portionrespiratory bronchioles

→alveolar duct →alveolar sac

→ alveoli

Function: gas exchange

1) Conducting portion ① bronchi→small bronchi

(from lobar bronchi to small bronchi)

• mucosa: Pseudostratified ciliated columnar epithelium -epithelium : thinner -goblet cell: number ↓ -lamina propria: thinner, -SM ↑

• submucosa: gland ↓• adventitia: cartilage ↓

② bronchiole: • diameter< 1mm• pseudostratified ciliated columnar ep

ithelium• goblet cell, Gland, cartilage↓

or disappear• smooth muscle ↑• circular mucosa plica ↑

*pulmonary lobule: one bronchioles and its all

branches and all alveoli• cone or pyramidal-shape• 0.1 cm in diameter

*Asthma*Asthma

• Allergy--"the epidemic of the 21st century".

• Asthma is a serious disease that affects the lungs and the airways that deliver air to the lungs.

③ terminal bronchiole: Diameter < 0.5 mm---goblet cell, gland, cartilage

disappear---SM: form a whole layer of

circumferential SM---Wall:• simple ciliated columnar

epithelium two types of cells

i.   ciliated cell ii.  secreting cell: Clara cellnon-ciliated and contain rich secret

ory granules (proteolytase) function: • dissolve the mucus• undifferentiated cell→ ciliate

d cell

Clara cell

Summary: Summary: Changes of conduction portionChanges of conduction portion

• The cartilages become irregular,and are smaller.

• The amount of muscle in the bronchial wall increase.

• Glands become fewer,and are absent in the bronchioles.

• The epithelium become thinner.

terminal bronchiolebronchiolebronchi → small bronchi

2) respiratory portion     ① respiratory bronchiole

• simple columnar or cuboidal epithelium• smooth muscle less

  ② alveolar duct: ---wall: alveoli or alveolar sac opening simple cuboidal epithelium or squamous epithelium

   ③ alveolar sac:---many alveoli open to it

   ④ alveoli:---with opening alveolar sac0.2mm in diameter, 300-400 million/per lung, total area: 70-80mm2

---wall squamous epithelium

SummarySummary

Respiratory bronchiole

Alveolar duct

Alveolar sac

Alveoli

Epithelium of AlveoliEpithelium of Alveoli

• type I alveolar cells: • squamous, • cover 95% of the alveolar

surface

• type II alveolar cell• cuboidal • cover 5% of the alveolar s

urface

---type I alveolar cell: EM: • plasmalemmal vesicles• tight junction

Function: constitute the blood-air barrier

---type II alveolar cell: secretory cells• contain osmiophilic multilamellar bodies• to release the surfactant to lower the surface tension• differentiate into type I alveolar cells.

• EM:secreting granules: osmiophilic multilamellar b

ody-0.1-1.0 um

• contains: phospholipid, glycosaminoglycan protein

• surfactant

alveolar septum:• Ct , elastic and reticular fibers• Fibroblast, macrophage, plasma cell, mast

cell• capillary: endothelium + basement

membrane

Elastic fiberElastic fiber

Blood-air barrier (respiratory memebrane)---components: • a layer of liquid• type I alveolar cell and ba

sement membrane• Ct• capillary endothelial cell a

nd basement membrane

alveolar pore: 10-15 um---balance the air-pressure between alveoli---lober pneumonia - bacteria or inflammatory sprea

d through the pore

alveolar marcophage: ---dust cell: phagocytose carbon or duct particles

alveolar macrophages:alveolar macrophages:

heart failure cell: lung edemathe alveolar marcophage

phagocytose RBC

digest the hemoglobin

hemosiderin (pigment)

accumulated them within macrophage

Pulmonary blood vesselsPulmonary blood vessels

• Pulmonary artery and veinFunction: contain venous blood to be oxygenated

• Bronchial artery and veinFunction: nourish the bronchial tree

Review TestReview Test• 1. Which of the following statements concerning terminal bronchioles is TRUE?• (A) They are part of the conducting portion of the respiratory system• (B) They function in gas exchange• (C) They do not contain ciliated cells• (D) They have cartilage plates present in their walls• 2. Alveoli in alveolar sacs possess all of the following components EXCEPT?• (A) elastic fibers in their walls• (B) a simple squamous lining epithelium• (C) reticular fibers in their walls• (D) smooth muscle in their walls

Homework1. Compare the structure of bronchiole with that of terminal bronchiole.2. Describe the morphology and function of type I cell and type II cell in lung in detail.3. What is the air-blood barrier (or respiratory memebrane) composed of ?

Reference book and websiteReference book and website

• 成令忠主编 .组织学与胚胎学 .第 4版 .北京；人民卫生出版社 .1995• Junqueira LC ,Carneiro J,Kelley RO.Basic Histology.

9th ed.New York;Appleton & Lange.Stamford,Connecticut,2005.

• http://www.meddean.luc.edu/lemen/MedEd/Histo?frames/histo_frames.html

• http://medicine.ucsd.edu/pathology/~som213/HistologyImageBank/

• http://www.whizseek.com/Scince/Biology/Histology/