Respiratory system Department of Histology and Embryology Medical college in Three Gorges University

Conduction 1.What is respiration? 2.Composition of respiratory system: conducting portion （ air ways) respiratory portion 3.Function: exchange of gases--- oxygen and carbon dioxide

Respiration is very important for the human body which have role in inhalation of oxygen and exhalation of carbon dioxide. Because an excessive amount of carbon dioxide produces acidity that can be toxic to cell.

Nose pharynx larynx Trachea bronchi lung

Conduction 1.What is respiration? 2.Composition of respiratory system: conducting portion （ air ways) respiratory portion 3.Function: exchange of gases--- oxygen and carbon dioxide

The trachea and principal bronchi: Trachea: The skeletal basis:16 to 20 tracheal cartilages. Each of these is a C-shaped mass of hyaline cartilage.

The open end of the “C” is directed filled by SM and Fibrous tissue. SM Cilia Caliber press

Mucosa 黏膜层 Adventitia 外膜 Submucosa 粘膜下层 Smooth muscle, CT

Pseudostratified ciliated columnar. Lamina propria Submucosa Mixed gland

Epithelium: lined by a pseudostratified ciliated columnar epithelium( respiratory epithelium). The cells: (a) Ciliated cells: move mucus (b) Goblet cells scattered in the epithelium produce mucous. To slide 5

(C) Brush cells:Non-ciliated columnar cells with microvilli on the free surface probably secrete a serous fluid which keeps the mucosa moist. ( D) Basal cells ： lying near the basal lamina probably give rise to ciliated cells to replace those lost. (E) Neuoendocrine cells (K cell):peptide To 4 basal cell

Ciliated cells 纤毛细胞

Goblet cell 杯状细胞

Mucos moved towards the larynx by ciliary action. back 3CiliaCilia

obstruct

Submucosa Mixed gland serous glands: keep moist mucous glands:a covering of mucous in which dust particles get caught.

Trachea Mucosa Submucosa Adventitia Lamina propria: CT Pseudostratified ciliated columnar. C-shaped cartilage Smooth muscle CT CT,serous-mucous gland Lymphoid tissue

Principal bronchi: The right and left principal bronchi (primary or main bronchi) have a structure similar to that of the trachea described above. The intrapulmonary bronchi are described with the lung.

Lung

The structure of the lungs has to be understood keeping in mind their function of oxygenation of blood.

Main bronchus trachea Bronchiole segment bronchus lobar bronchus

Alveolar duct Alveolar sacs Respiratory bronchioles Terminal bronchiole alveroli

The lung Conducting portion: lobar bronchi segmental bronchi smaller bronchi lobular bronchioles terminal bronchioles Respiratory portion: respiratory bronchioles alveolar duct alveolar sac pulmonary alveolus

Pulmonary lobule : lobular bronchioles, their branches and pulmonary alveolus. lobule pneumonia

The structure of the larger intrapulmonary bronchi is similar to that of the trachea. Conducting portion

Intrapulmonary bronchus: It is lined by pseudostatified columnar epithelium with goblet cells resting on a thin basement membrane. The lamina propria consists of reticular and elastic fibres. The submucous coat contains both mucous and serous acini.A complete layer of smooth muscle fibres is present which is resonsible for infolding of the mucous membrane.

Outermost is the hyaline cartilage which is visible as small cartilaginous plates of varying in sizes and shapes

(1) pseudostatified ciliated columnar epithelium simple ciliated columnar, then non-ciliated columnar finally cuboidal. (2) Glands become fewer, and are absent in the walls of bronchioles. Changes of micrograph in the bronchus of the lung

(3) The amount of muscle in the bronchial wall increases as the bronchi become smaller. The presence of muscle in the walls of bronchi is of considerable clinical significance.Spasm of this muscle constricts the bronchi and can cause difficulty in breathing. leads to a disease called asthma.

(4)The cartilages become irregular in shape, and are progressively smaller. It is absent in the walls of bronchioles. This is the criterion that distinguishes a bronchiole from a bronchus.

Bronchioles: less than 1mm in diameter Each bronchioles supplies air to a pulmonary lobule. (1)Epithelium:simple columnar with occasional goblet cells to cuboidal with Clara cells. (2)Submucous of bronchioles has no gland (3)no cartilage

Terminal bronchiole: It is lined by simple columnar epithelium. The propria contains elastic and smooth muscle fibres.The gland and cartilage plates are absent.

Respiratory bronchiole: The wall is interrupted by the presence of alveoli.It is lined by cuboidal epithelium. The walls consist of collagenous connective tissue containing bundles of interlacing smooth muscle fibers and elastic fibres. Respiratory portion

alveolar ducts and alveolar sac: The alveolar ducts have a long tortuous course and give off several branches and do not have walls of their own. These are closely with thin-walled outpouchings the alveolar sacs and alveoli.The alveolar ducts and alveoli are lined with squamous epithelium.

Alveoli are specialized saclike structure that make up the greater part of the lungs.They are the main sites for the principal function of the lungs the exchange of O2 and CO2 between inspired air and blood. Alveoli

LM: These are thin walled polyhedral sacs. The alveoli are lined by simple squamous epithelium, with two types of cells which rest on a basement membrane. The main support of the alveoli is provided with elastic fibres.

type II pneumocytes type I pneumocytes

The alveoli are blind sacs having very thin walls through which oxygen passes from air into blood, and carbon dioxide passes from blood into air.

EM: Type I pneumocytes: the squamous cells, Majority of cells lining the alveoli.provide a barrier of minimal thickness that is readily permeable to gases. Type II pneumocytes: the cuboidal, few, Type II cells secrete the surfactant which lowers surface tension and prevents alveoli from collapsing.

Type I cells Type II cells Dust cells capillary

Interalveolar septa: the connective tissue that lie between the adjacent alveoli. It contains: (1) Numerous capillaries, (2)Elastic fibers: the main support (3)Cells:macrophages and leucocytes, fibroblast.

Blood –gas Barrier: The Blood-gas barriers is that region of the interalveolar septum that is traversed by O2 and CO2 as these gases go from the blood to the lumen of the alveolus,and vice versa. The following structure: Surfactant and type I pneumocytes, fused based laminae of type I pneumocytes and endothelial cells of the capillary, endothelial cells of the continuous caillary.