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.
SM
Cilia
Caliber
press
The open end of the “C” is directed filled by SM and Fibrous tissue.
Submucosa 粘膜下层
Adventitia 外膜
Mucosa 黏膜层
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
back 3Cilia
action.
obstruct
Submucosa
Mixed gland
serous glands: keep moist
mucous glands:a covering of
mucous in which dust particles
get caught.
Mucosa
Pseudostratified
ciliated columnar.
Lamina propria: CT
Trachea
Submucosa
CT,serous-mucous gland
Lymphoid tissue
C-shaped cartilage
Adventitia
Smooth muscle
CT
• 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.
trachea
Bronchiole
segment bronchus
Main bronchus
lobar bronchus
Terminal bronchiole
Respiratory
bronchioles
Alveolar duct
Alveolar sacs
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
Conducting portion
The structure of the larger intrapulmonary
bronchi is similar to that of the trachea.
• 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
Changes of micrograph in the bronchus of the lung
• (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.
• (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 portion
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.
• 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
• 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.
• 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 I pneumocytes
type II 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.
Dust cells
Type II cells
Type I 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.