Cell Biology and Histology of Vascular System

Question 1

What kind of epithelium is in the blood vessels

Answer 1

Simple squamous epithelium

Question 2

Where does most of the blood pressure drops

Answer 2

In the arterioles

Question 3

Walls of the arteries

Answer 3

1. Inner most is the tunica intima 2. Middle one is the tunica media 3. Outermost is the tunica external or adventitia

Question 4

Details about large artery

Answer 4

1. Also called conducting artery 2. Walls extend and contract during systole and diastole

Question 5

What are the wavy structures

Answer 5

The wavy structures in the tunica media are the elastic fibers and the rest of it are the smooth muscles

Question 6

Details about the muscular arteries

Answer 6

1. Medium or muscular arteries, also called distributing arteries since they can determine the distribution of blood to the periphery by shunting of vessels
2. Compared with large arteries, medium arteries have a more prominent internal elastic laminae
3. In the tunica media they have less elastic fibers and more prominent smooth muscles

Question 7

Details about the arterioles

Answer 7

1. They are the resistance vessels, major determinants of TPR - exhibit the property of vasoconstriction and vasodilation
2. There are 2 to 5 concentric layers of vascular smooth muscles intunica media

Note: The adventitia blends into the adipose tissue in the surrounding

Question 8

What is the diameter of a capillary

Answer 8

5 to 10 micrometers

Question 9

What are the different types of capillaries

Answer 9

1. Continous capillaries: They have modified smooth muscle cells called pericytes which occur between the endothelium cells and the basement membrane.
2. Fenestrated capillaries: The cytoplasm of the endothelial cells is perforated
3. Discontinuous capillaries: There are big gaps between the endothelial cells

Question 10

How are substances transported across the continuous capillaries

Answer 10

The cytoplasm is thin but also there is tremendous amount of vessicle trafikking across the cytoplasm. This is a bidirectional transportation mechanism.

These vessicles are called Calveolae and the protein responsible for them is the claveolin.

This is not needed in fenestrated and discontinuous capillaries

Question 11

Answer 11

Pericyte nucleus is on the left, it is larger the nucleus of the endothelial cells

Question 12

What is the function of pericytes

Answer 12

1. They are involved with tight junction formation and vessicle traficking in the endothelial cells
2. Loss of pericytes in the brain contributes to increase permeability of the blood-brain barrier which leads to neurodegenerative diseases
3. These cells allow the endothelial cells to mutliply which is crucial in angiogenesis during the time of growth and repair
4. Can dedifferentiate into myofibroblast like cells which leads to abnormal ECM production leading to fibrosis

Question 13

What are some of the things to note here in the diagram

Answer 13

Several things to note here:

1. There are pores between the cytoplasmic surface
2. The pores are lined by diaphram sometimes
3. Size of the pore can change to regulate permeability
4. The second picture shows fenestrated capillaries that both have and lack diaphrams on the pores

Question 14

Some details about the veins

Answer 14

1. This is the site of leukocyte egress from the blood into the tissue - done by disrupting endothelial junctions
2. Pericytes can also be present

Question 15

What are the functions of endothelial cells

Answer 15

1. They set the vascular tone
2. Blood clothing
3. Inflammation
4. Angiogenesis

Question 16

What is atherosclerosis and what are the risk factors that contribute to it

Answer 16

It causes formation of lesions in the blood vessels that are called atheroma. These lesions are formed by deposition of fatty material and usually happens in large (elastic) arteries.

1. Diabetes
2. Smoking
3. Hypertension
4. Aging
5. Obesity

Question 17

Describe the formation of atheroma

Answer 17

1. Initiated by damage to the blood vessel - the slide said that it can be due to hypercholestrolinemia
2. Macrophages invade the space which causes the fibroblasts in the tunica media to proliferate
3. Macrophages release lipids and cytokines causes the smooth muscle proliferation and collagen depsoition
4. This surface promotes thrombosis and the blood vessel can be completely occluded (with or without thrombosis formation)

Question 18

Describe the structure of the lymphatic vessels

Answer 18

1. Structure is really leaky and discontinuous
2. The basement membrane is also discontinuous
3. Also have valves

Question 19

Know the difference between vasculogenesis and angiogenesis

Answer 19

Vasculogenesis is making blood vessels from scratch whereas angiogenesis is sprouting of new blood vessels from existing blood vessels

Question 20

Steps of vasculogenesis

Answer 20

1. Blood islands are formed by hemangioblasts
2. Enapsulate themselves to form the hematopoietic stem cells inside a vessel
3. Form the primary capillary plexus
4. Forms blood vessel

Question 21

What are the 2 ways a cell can become hypoxic

Answer 21

Increased oxygen demand or decreased oxygen supply

Question 22

What happens when a cells is hypoxic

Answer 22

In hypoxic conditions HIF-1 transcription factor is released which has the following roles

1. Eryhtropoietin (EPO) is made to increase the rate of erythropoiesis
2. VEGF is made to induce angiogenesis and vasculogenesis
3. Glycolytic enzymes are increased to survive in hypoxic conditions

Question 23

What are the HIF target genes

Answer 23

1. EPO
2. VEGF
3. VEGF-R
4. GLUT

Question 24

What kind of angiogenesis is shown by tumor cells

Answer 24

Angiogenesis of the blood vessels and of the lymphatics