Respiratory System Prof. Ji-Cheng Li Department of Histology and Embryology

Objectives 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 gland Ep: pseudostratified ciliated columnar epi. LP: vascular network Ep: olfactory epi. LP: serous gland (Bowman gland, olfactory gland) Olfactory cells Supporting cells Basal cells

2. Trachea and main bronchi Structure: Mucosa Submucosa Adventitia

(1) Mucosa : Epithelium Pseudostratified ciliated columnar epithelium Ciliated cell Goblet cell Brush cell Basal cell Small granule cell

Epithelium Figure 17-6: Ciliated respiratory epithelium

ciliated cell with cilia To provide a sweeping 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 contract of SM and secretion of gland i. 5-hydroxytryptamine(serotonin) ii. Calcitonin

Basal cell stem cell

(2) Submucosa LCT, containing mixed glands with diffuse LT and LN SIg A = secretory component (secreted by epithelum cell) + Ig A ( produced by plasma cell)

(3) Adventitia: cartilage ring: “C ” shaped circular ligament: elastic fiber posterior part (membrane part): SM, elastic fiber, tracheal gland

3. 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 portion respiratory 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 epithelium 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 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 cell non-ciliated and contain rich secretory granules ( proteolytase ) function: dissolve the mucus undifferentiated cell→ ciliated cell

Clara cell

Summary: Changes 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 sac 0.2mm in diameter, million/per lung, total area: 70-80mm wall squamous epithelium

Summary

Respiratory bronchiole Alveolar duct Alveolar sac Alveoli

Epithelium of Alveoli type I alveolar cells: squamous, cover 95% of the alveolar surface type II alveolar cell cuboidal cover 5% of the alveolar surface

---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 body um contains: phospholipid, glycosaminoglycan protein surfactant

alveolar septum: Ct, elastic and reticular fibers Fibroblast, macrophage, plasma cell, mast cell capillary: endothelium + basement membrane

Elastic fiber

Blood-air barrier ( respiratory memebrane ) ---components: a layer of liquid type I alveolar cell and basement membrane Ct capillary endothelial cell and basement membrane

alveolar pore: um ---balance the air-pressure between alveoli ---lober pneumonia - bacteria or inflammatory spread through the pore

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

alveolar macrophages:

heart failure cell: lung edema the alveolar marcophage phagocytose RBC digest the hemoglobin hemosiderin (pigment) accumulated them within macrophage

Pulmonary blood vessels Pulmonary artery and vein Function: contain venous blood to be oxygenated Bronchial artery and vein Function: nourish the bronchial tree

Review 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

Homework 1. 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 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, mes/histo_frames.htmlhttp:// mes/histo_frames.html gyImageBank/ gyImageBank/ / /