Blood Vessels Introduction

When it comes to Blood Vessels, there are 3 types. Can you name them?

Arteries, Capillaries, and Veins 

What is the function of the Arteries?

Convey blood from the heart to the capillaries. 

What is the function of the Capillaries?

Microscopic porous blood vessels exchange substances between the blood and the tissue. 

What is the function of the Veins?

Transport blood from capillaries 

What part of the Blood Vessel (in the red box) is this

Vaso Vasorum

What part of the Blood Vessel (in the red box) is this

Fat Cells

What part of the Blood Vessel (in the red box) is this

Endothelium

What part of the Blood Vessel (in the red box) is this

Subendothelial Connective Tissue

What part of the Blood Vessel (in the red box) is this

Internal Elastic Membrane

What part of the Blood Vessel (in the red box) is this

Tunica Intima

What part of the Blood Vessel (in the red box) is this

Tunica Media

What part of the Blood Vessel (in the red box) is this

External Elastic

What part of the Blood Vessel (in the red box) is this

Tunica Adventitia (or Externa)

What is the space inside a blood vessel called?

The Lumen

How many layers make up the walls of blood vessels, and what are they called?

Three layers called tunics, the tunica intima, tunica media, and tunica externa 

What is the innermost layer of the Blood vessel wall called?

The Tunica intima

What type of epithelium makes up the endothelium of the tunica intima 

Simple Squamous Epithelium

What type of connective tissue is found in the subendothelial layer of tunica intima?

Areolar connective tissue

What is the middle layer of a blood vessel wall called?

Tunica media

What is the middle layer of a blood vessel wall called? 

Tunica media

What type of tissue makes up the tunica media

Circularly arranged layers of smooth muscle and elastic fibers

What happens to the lumen when the smooth muscle in the tunica media contracts

It causes vasoconstriction, which narrows the lumen.

What happens to the lumen when the smooth muscle in the tunica media relaxes?

It causes vasodilation, which widens the lumen.

What is the outermost layer of a blood vessel wall called?

The tunica externa

What type of tissue is the tunica externa made of ?

Areolar connective tissue with elastic collagen fibers

What is the main function of the tunica externa?

It helps anchor the vessel to other structures. 

What are the small arteries in the tunica externa that supply very large blood vessels called?

Vasa Vasorum 

What are companion vessels

Arteries and veins that lie next to each other and serve the same body region

Which type of vessel has a thicker tunica media and a narrower lumen (Arteries or Vein)?)

Arteries

Which type of vessel has more elastic and collagen fibers?

Elastic Arteries

Why are arteries more resilient and resistant to change in blood pressure?

Because they have thicker walls with more elastic and collagen fibers

Which type of vessel has a thicker tunica externa and a larger lumen (Arteries or Veins)?

Veins

Why do veins collapse more easily than arteries when empty?

They have thinner walls and fewer elastic and collagen fibers.

What layers make up the wall of a capillary

Only the tunica intima is composed of endothelium and the basement membrane

Why do capillaries have thin walls?

Their thin walls allow for rapid gas and nutrient exchange between the blood and tissues

As arteries branch farther from the heart, what happens to the lumen diameter?

The lumen diameter decreases

What happens to the amount of elastic fibers as arteries branch into smaller vessels?

The amount of elastic fibers decreases 

What happens to the relative amount of smooth muscle as arteries branch into smaller vessels? 

The relative amount of smooth muscle increases 

What are the three basic types of arteries?

Their thin walls allow for rapid gas and nutrient exchange between the blood and tissues

In general, arteries branch into smaller vessels that extend from which organ?

The heart

In which direction do arteries carry blood?

Away from the heart to the tissues.

Why are the walls of arteries elastic?

Their elasticity allows them to absorb the pressure created by the ventricles as they pump blood into the arteries 

What allows arteries to regulate their diameter?

The smooth muscle in the tunica media 

What are elastic arteries also known as

Conducting arteries 

What is the diameter range of elastic

From 2.5 cm to 1cm

What is the main function of elastic arteries 

To conduct blood from the heart to the muscular arteries 

Why do elastic arteries have a large portion of elastic fibers?

The elastic fibers allow them to stretch and recoil, helping to propel blood through the arteries during diastole 

What are some examples of elastic arteries?

The aorta, pulmonary trunk, common carotid arteries, and common iliac arteries.

What role do elastic arteries (like the aorta) play in blood flow

They act as pressure reservoirs that help maintain continuous blood flow during the cardiac cycle 

What happens to the elastic arteries during ventricular contraction (systole)

They stretch as the left ventricle contracts and ejects blood into them.

What happens to the elastic arteries during ventricular relaxation (diastole)?

They recoil, pushing blood forward toward the capillaries even while the ventricle refills.

Why is the stretch and recoil of elastic arteries important?

It smooths out the pressure fluctuations from the heartbeat and ensures continuous blood flow to tissues.

What are muscular arteries also known as

Distributing arteries

What is the diameter range of muscular arteries?

From 1cm to 3mm

What is the primary function of muscular arteries?

To distribute blood to specific body regions

What allows muscular arteries to perform vasoconstriction and vasodilation?

The smooth muscle in their walls 

Where is the internal elastic lamina located in a muscular artery?

Between the tunica intima and the tunica media 

Where is the external elastic lamina located in a muscular artery?

Between the tunica media and the tunica externa 

What type of arteries are usually named arteries of the body?

Muscular arteries 

Give examples of muscular arteries.

The brachial artery and the coronary arteries 

What are arterioles?

The smallest arteries with diameters ranging from 3mm to 10 micrometers.

How do larger and smaller arterioles differ in structure?

Larger arterioles have three tunics; smaller arterioles have only a thin endothelium and a single layer of smooth muscle.

What is a vasometer tone?

The state in which the smooth muscle of arterioles is somewhat constricted

What is the primary function of arterioles?

To regulate systemic blood pressure and blood flow.

What is atherosclerosis?

A progressive disease of elastic and muscular arteries characterized by the presence of atheromatous plaques (Atheromas)

What is an atheroma?

A thickening of the tunica intima that narrows the arterial lumen.

What can cause atherosclerosis?

Injury to the endothelium caused by infection, trauma, or hypertension.

How does endothelial injury lead to atherosclerosis?

Injury triggers an inflammatory reaction, leading to the formation and enlargement of atheromas, which narrow the lumen.

Why might someone be unaware they have atherosclerosis

Plaques often do not cause symptoms until they restrict blood flow to a region

What condition makes a person more prone to atherosclerosis?

Increased cholesterol in the blood, known as hypercholesterolemia 

Which sex is more commonly affected by atherosclerosis?

Males are more affected than females

How do smoking and hypertension influence atherosclerosis risk

They increase vascular injury and the overall risk of developing the disease

What is angioplasty

A treatment that expands a narrowed reigon of an artery

What is the purpose of coronary bypass surgery

To create a new route for blood to flow around a blocked or narrowed artery

What is an aneurysm?

A condition where part of an atrial wall thins and balloons out.

Why is an aneurysm dangerous?

The weekend wall is more prone to rupture, which can cause massive bleeding and death

Which type of arteries are most affected by aneurysms?

Elastic and muscular arteries

Why do arteries become more prone to aneurysms with age?

 They become less able to withstand the forces from pulsating blood

Where are aneurysms most commonly found?

 in the aorta or arteries at the base of the brain.

How does age affect aneurysm risk?

The risk of developing an aneurysm increases with age

What do capillaries connect?

 They connect arterioles to venules

What is the average length and diameter of a capillary?

Average length is about 1 mm, and diameter is 8 to 10 micrometers

How do erythrocytes travel through capillaries?

 in a single file, a formation called a rouleau

What is the structure of a capillary wall?

It consists of an endothelial layer resting on a basement membrane

Why are capillary walls thin and their diameters small

 to optimize exchange between Blood and Tissue fluid

What are the three types of capillaries?

Continuous, fenestrated, and sinuosoid capillaries

What type of lining do continuous capillaries have?

 endothelial cells form a continuous lining

How are endothelial cells in continuous capillaries connected?

 by tight junctions that do not form a complete seal

What are intercellular clefs?

 gaps between endothelial cells of the capillary wall that allow small molecules to pass

Which substances can and cannot pass through continuous capillary walls?

 Larger particles like cells and proteins cannot pass, but smaller molecules such as glucose can pass.

Where are continuous capillaries commonly found?

 in muscle, skin, lungs, and the central nervous system

What structural feature distinguishes fenestrated capillaries from continuous capillaries

 endothelial cells form a continuous lining, but contain small pores called fenestrations.

What is the function of fenestrations in capillaries?

They allow movement of smaller plasma proteins through the capillary wall.

Where are fenestrated capillaries commonly found?

In areas with extensive fluid transport

Give two examples of locations with fenestrated capillaries

Intestinal capillaries ( for nutrient absorption)  and kidney capillaries ( for blood filtration to form urine). 

What kind of lining do sinusoid capillaries have?

An incomplete endothelial lining with large gaps.

What is special about the basement membrane of sinusoids?

 It is incomplete or absent.

 what can pass through the opening in sinusoids capillaries?

 large substances such as formed elements and large proteins.

Where are sinusoids commonly found?

In the bone marrow, spleen, and some endocrine glands.

What are capillary beds?

Groups of capillaries that function together to exchange substances between blood and tissues.