Composition of capillaries, Biology

Assignment Help:

Composition of Capillaries

Capillaries are made up of a single layer of endothelial cells surrounded by a basal membrane. The walls ale thin and fragile but because of their small diameter resist stretching in response to capillary blood pressure. Water and dissolved substances of small molecular weight (gases, salts, sugars, amino acids etc.) can diffuse easily.

2056_Composition of Capillaries.png

Figure:  Fluid exchange across a capillary wall

In addition, fluid is forced out through the walls. Substances of molecular weight more than 70,000 (mostly proteins) do not pass out of the capillary walls. These proteins exert an osmotic effect called the colloidal osmotic pressure, which tends to draw water back into the capillary from the surrounding tissue fluid. Another force, the hydrostatic pressure of blood tends to push the water across the endothelial cell layer out of the capillaries. When the hydrostatic pressure within the capillary exceeds colloidal osmotic pressure, fluid is passed out through the capillary wall; when the hydrostatic pressure in the capillary falls below the colloidal osmotic pressure the 'fluid is drawn in. The hydrostatic pressure in the arterial end of the capillary is higher than the colloidal arterial pressure while at the venous end it is often lower. Therefore, fluid is filtered out at the arterial end and redrawn in at the venous end. This amount of fluid forced out and the amount re-entering varies greatly. Usually outflow exceeds inflow and excess fluid remains in the interstitial spaces. This as you already know forms the lymph.


Related Discussions:- Composition of capillaries

What are fat soluble vitamins, What are fat soluble vitamins? As we al...

What are fat soluble vitamins? As we already know, there are four fat-soluble vitamins - A, D, E and K, The presence of fat is required for the assimilation of these vitamins

Prognosis, The course and ultimate prognosis of ARF is usually directly rel...

The course and ultimate prognosis of ARF is usually directly related to the severity of carditis. The course and prognosis also depends upon recurrence of rheumatic fever. In pre-p

Role of carbohydrates in dyslipidemia, Q. Role of Carbohydrates in dyslipid...

Q. Role of Carbohydrates in dyslipidemia? It is important to know about these carbohydrates, as they all differ in their digestive properties. The rate of absorption is variabl

Intermediate products of anaerobic respiration, (a) What are the intermedia...

(a) What are the intermediate products of anaerobic respiration in an active muscle? (b) Which of them is associated with oxygen debt? (c) In what way is th

Explain about human sperm, Which one of the following statements about huma...

Which one of the following statements about human sperm is correct? 1. Acrosome has a conical pointed structure used for piercing and penetrating the egg, resulting in fertilis

Explain disease jet lag, Jet Lag   Disturbance of body and environmental...

Jet Lag   Disturbance of body and environmental rhythms resulting from a rapid change in time zones gives rise to jet lag, which is characterized by insomnia, decreased quality

What is the ecological role of earthworms, Q. What is the ecological role o...

Q. What is the ecological role of earthworms? Earthworms have an important ecological role as they eat decomposing organic material. They also dig tunnels in the subsoil allowi

Induction of antimicrobial substances, Induction of antimicrobial substance...

Induction of antimicrobial substances Phytoalexins are antimicrobial substances produced by plants in response to pathogen. They accumulate at the site of infection. For exam

Respiration, how does respiration in animals occur? what is respiration? wh...

how does respiration in animals occur? what is respiration? what are the common types of respiration?

What are the major morphological features of birds, Q What are the major mo...

Q What are the major morphological features of birds? Birds are animals that present aerodynamic bodies covered with feathers, pneumatic bones, anterior limbs transformed into

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