Capillary System

Question 1

What are the general characteristics of capillaries

Answer 1

smallest blood vessels, that are used to exchange nutrients and waste products -thin walled for diffusion, they lack tunica media and tunica externa (adventitia) -largest surface area of all the vessels

Question 2

What are examples of tissues w/o capillaries

Answer 2

cornea and lens of the eye, cartilage

Question 3

What is a capillary bed

Answer 3

a network of 10-100 capillaries that arise from 1 metarteriole

Question 4

Describe vasomotion

Answer 4

Contraction/relaxation of pre-capillary sphincters while tissue is at rest which, insures all capillary beds receive blood flow at rest -w/o these tissue becomes ischemic

Question 5

What causes vasomotion

Answer 5

local chemicals released by endothial cells in response to O2, CO2, lactic acid, H levels

Question 6

What are the 3 types of capillaries

Answer 6

1. Continuous 2. Fenestrated 3. Sinusoid

Question 7

Describe continuous capillaries

Answer 7

-endothelial cells form a continuous tube, only interrupted by small intracellular clefts (where exchange happens) -most common

Question 8

Describe fenestrated capillaries

Answer 8

-endothelial cells have small intracellular clefts and many fenestrations (cycloplasmic holes) allowing diffusion of larger molecules -found in kidneys, villi of small intestines

Question 9

Describe sinusoid capillaries

Answer 9

Have incomplete or absent basement membranes and large fenestrations and very large intercellular clefts that allow blood cells and proteins to pass through -least common -contain specialized cells -found in liver, spleen, bone marrow

Question 10

Describe a portal system and give examples of these systems

Answer 10

-When blood passes from one capillary network to another, with veins/venules in between. -Use to transport products of one region into another in high concentrations -example=hepatic portal circulation or hypophyseal portal system