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

Clinical features - infective endocarditis, The clinical  manifestations of...

The clinical  manifestations of IE result from the local destructive effects of intracardiac infection; the embolization of bland or septic fragments of vegetations to

Veterbrate, Draw and describe the structure of amphibian,reptile mammal and...

Draw and describe the structure of amphibian,reptile mammal and bird

Why bacteria classified as prokaryotes, Bacteria have a region known as a n...

Bacteria have a region known as a nucleoid, in which their genetic material is located. Why, then, are bacteria classify as prokaryotes? The nucleoid is not surrounded by a mem

Concept of universality of the genetic code, Q. What is the concept of univ...

Q. What is the concept of universality of the genetic code? What are the exceptions to this universality? The genetic code is universal because the rules of protein codificatio

Explain fontan operation and ross operation in heart dieases, Explain fonta...

Explain fontan operation and ross operation in heart dieases? Fontan Operation: The Fontan principle involves redirecting the whole systemic return into the lungs bypassing t

Dimensions of the cells, On a given microscope, the numerical aperture of t...

On a given microscope, the numerical aperture of the objective is 1.5. The microscope is provided with a filter that selects a wavelength of 500 nm. What is the limit of resolution

What are the major cellular features of fungi, Q. What are the major cellul...

Q. What are the major cellular features of fungi? There are pluricellular and unicellular fungi. All fungi are heterotrophs and eukaryotes. Fungi have cells with cell wall m

Phosphorus cycle - nutrient cycles, Phosphorus Cycle - Nutrient Cycles ...

Phosphorus Cycle - Nutrient Cycles Phosphorus is a very important nutrient because of its role in the form of phosphate, in reactions that store and release energy. The availa

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