English for doctors. Capillaries (lecture notes)

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English for doctors. Capillaries (lecture notes)

Lecture notes, cheat sheets

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LECTURE 19

Capillaries are thin-walled, narrow-diameter, low-pressure vessels that generally permit easy diffusion across their walls. Most capillaries have a cross-sectional diameter of 7-12 mm. They are composed of a simple layer of endothelium, which is the lining of the entire vas cu-lar system, and an underlying basal lamina. They are attached to the surrounding tissues by a delicate reticulum of collagen. Associated with these vessels at various points along their length are specialized cells called pericytes. These cells, enclosed within their own basal lamina, which is continuous with that of the endothelium, contain contractile proteins and thus may be involved in the control of capillary dynamics. They may also serve as stem cells at times of vascular repair. Capillaries are generally divided into three types, according to the structure of their endothelial cell walls.

Continuous (muscular, somatic) capillaries are formed by a single uninterrupted layer of endothelial cells rolled up into the shape of a tube and can be found in locations such as connective tissue, muscle, and nerve.

Fenestrated (visceral) capillaries are characterized by the presence of pores in the endothelial cell wall. The pores are covered by a thin diaphragm (except in the glomeruli of the kidney) and are usually encountered in tissues where rapid substance interchange occurs (eg, kidney, intestine, endocrine glands).

Sinusoidal capillaries can be found in the liver, hematopoietic and lymphopoietic organs, and in certain endocrine glands. These tubes with discontinuous endothelial walls have a larger diameter than other capillaries (up to 40 mm), exhibit irregular cross-sectional profiles, have more tortuous paths, and often lack a continuous basal lamina. Cells with phagocytic activity (macrophages) are present within, or just subjacent to, the endothelium.

new words

capillaries - capillaries

to thin-walled - surrounded by a thin wall

narrow-diameter - narrow diameter

low-pressure - low pressure

that - that

generally - mostly

permit - permission

easy - easy

diffusion - diffusion

cross-sectional - transverse

to be composed - to be composed

simple - simple

endothelium - endothelium

lining - alignment

entire - all

vascular - vascular

underlying - underlying

basal - basic

lamina - thin plate

Rules for using articles with geographical names.

The definite article is used before the names of rivers, canals, seas, bays, straits, oceans, archipelagos, mountain ranges.

The article is not used before the names of lakes, mountains, islands, continents, cities, countries. Exceptions:

the United States of America

the United Kingdom of Great Britain and Northern Ireland the Netherlands the Ukraine the Crimea the Congo

Answer the questions.

1. Describe capillaries: how do they like?

2. What diameter do the most capillaries have?

3. What are the capillaries composed of?

4. Where are the capillaries attached to?

5. What are pericytes?

6. What do pericytes contain?

7. Where can pericytes be involved?

8. Where can sinusoidal capillaries be found?

9. What diameter do sinusoidal capillaries have?

10. With help of what are continuous (muscular, somatic) capillaries formed by?

Make the sentences of your own using the new words (10 sentences).

Find the definite and indefinite articles in the text.

Author: Elena Belikova

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