Lower respiratory tract, Biology

Assignment Help:

Lower Respiratory Tract:

Trachea:

 

1053_Lower Respiratory Tract.png

Trachea or windpipe  is 12 cm long, 2.5 cm in diameter lying in front of the esophagus and  ends opposite the fourth dorsal vertebrae where it divides  into main bronchi.  It consists of a number of c-shaped rings of cartilage connected byfibrous tissues and having the opening of the C posteriorly. The hnction of the rings of cartilage is to keep trachea open  and prevent the collapse of the wall like those of the esophagus. It is lined with ciliated columnar epithelium and cells which secrete mucus.  

Bronchi and Bronchioles:

Trachea ends by  bifurcating into right and  left bronchi at the carina, the level of fourth dorsal vertebra. Each bronchus passes  to the corresponding lung. From each main bronchus smaller bronchi are given off, like branches of a tree, and the smallest bronchi is called bronchioles. The structure of  the bronchi is similar to that of the bronchi, but they  contain no cartilaginous loops, instead there are more muscle fibers. Mucus is secreted by  goblet cells interspersed between the ciliated cells and  by  sub-mucosal mucus-secreting glands. 

Each bronchioles terminate in an alveolar sac made up of number of air pockets wihc are lined with delicate layer of flattened epithelial cells and are surrounded by network of capillaries through the walls of which interchange of gasses takes place. Blood in the capillaries is brought by  the pulmonary artery from the right ventricle and drained into  the  left atrium through the pulmonary veins. Alveoli which number 300 millions  in adults are minute sacs that arise from the walls of the respiratory bronchioles and alveolar ducts. The alveolus is composed of a single layer of squamous epithelium and elastic basement membrane. These two layers together with the interstitium and the endothelial and basement layers of the adjacent capillary, from the alveolar-capillary membrane or interface. It is across this membrane diffusion of carbon dioxide and oxygen occurs. The structure of millions alveoli provides a large surface area for gaseous diffusion to occur. In  addition to this respiratory hnction the alveoli prevent  lung collapse by producting surfactant, a phospholipid that decreases surface tension and prevents intersititial fluid  from  transferring into the lung space.  


Related Discussions:- Lower respiratory tract

Vertebrate kidney, Normal 0 false false false EN-IN X...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Erythema - common disorders of skin, Erythema: Erythema is one of  the...

Erythema: Erythema is one of  the,commonest primary lesions of  the skin. It  is produced by  the dilation of the cutaneous blood vessels.  If the dilation  is accompanied  by

Choice of transgenic animal, C h oice of transgenic animal First and ...

C h oice of transgenic animal First and foremost is the selection of animal species in which gene of interest is to be transferred. Whatever is the goal of production of tran

Epilimnion - summer stratification, Epilimnion - Summer Stratification ...

Epilimnion - Summer Stratification This forms the upper layer of the lake and consists of freely- circulating warm water which is well lighted though poor in nutrients. Most o

Phylum, Are protozoan''s diploblastic or triploblastic

Are protozoan''s diploblastic or triploblastic

Middle ear, MIDDL E EAR - Protected by tympanic bone. It's cavity...

MIDDL E EAR - Protected by tympanic bone. It's cavity is tympanic cavity. It is lined by simple cilliated columnar epithelium. It is connected to naso pharynx by Eu

Definition of osseointegration, Q. Definition of Osseointegration From the ...

Q. Definition of Osseointegration From the view of the patient? An implant fixture is osseointegrated if it provides a stable and apparently immobile support of a prosthesis un

Disbeliefs about insulin injection, Some people have disbeliefs regarding i...

Some people have disbeliefs regarding insulin injection. You have to find out if there are any disbeliefs and try to explain the importance of insulin injection. Do not force the p

What is the phenotype, What is the phenotype? Phenotype is every observ...

What is the phenotype? Phenotype is every observable characteristic of a living being conditioned by its genes. A few phenotypes may be altered by nongenetic factors (for insta

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd