Ch20: Blood Vessels

Define the following: Arteries, capillaries, veins. What does a blue vs. red blood vessel represent?

• Arteries: Carry oxygenated blood away from the heart to the body's tissues (except pulmonary arteries)
• Capillaries: Tiny vessels that connect arteries and veins, allowing exchange of substances between blood and tissues
• Veins: Return deoxygenated blood from the body back to the heart (except pulmonary veins)

In diagrams:
• Red vessels -typically represent arteries carrying oxygenated blood
• Blue vessels- usually represent veins carrying deoxygenated blood

What are the three layers (tunics) found in a typical blood vessel?

A typical blood vessel consists of three layers or tunics:
1. Tunica intima: The innermost layer, consisting of endothelial cells lining the lumen of the vessel.

2. Tunica media: The middle layer, composed primarily of smooth muscle cells and elastic fibers.

3. Tunica externa: The outermost layer, made up of connective tissue that helps anchor the blood vessel to surrounding tissues.

What are the differences between an artery and a vein?

Structure and Function:
- Arteries: Carry blood away from the heart, have thicker walls to withstand higher blood pressure
- Veins: Carry blood towards the heart, have thinner walls and valves to prevent backflow

Blood Pressure:
- Arteries:Higher blood pressure
- Veins: Lower blood pressure

Oxygenation:
- Arteries: Usually carry oxygenated blood (except pulmonary arteries)
- Veins: Usually carry deoxygenated blood (except pulmonary veins)

Location:
- Arteries: Generally located deeper in the body
- Veins: Often found closer to the skin surface

What are the three different types of arteries and what are their functions?

There are three main types of arteries, each with distinct functions:

1. Elastic arteries:
- Function: Conduct blood away from the heart and withstand high pressure
- Examples: Aorta, pulmonary arteries

2. Muscular arteries:
- Function: Distribute blood to various body parts and regulate blood flow
- Examples: Femoral, brachial, and radial arteries

3. Arterioles:
- Function: Control blood flow into capillary beds and regulate blood pressure
- Smallest type of arteries, connecting to capillaries

What are the two different types of capillaries and their functions

1. Continuous capillaries:
- Found in most tissues
- Have a continuous, uninterrupted lining of endothelial cells
- Function: Allow passage of small molecules and ions

2. Fenestrated capillaries:
- Found in organs that filter or secrete substances
- Have small pores or "windows" in the endothelial lining
- Function: Allow for rapid exchange of larger molecules

(Both types play crucial roles in the exchange of substances between blood and tissues, but their specific structures adapt them to the needs of different organs and systems in the body.)

What are the three different types of veins? What is the general function of veins?

1. Superficial veins:
- Located close to the skin surface
- Often visible through the skin

2. Deep veins:
- Located deeper in the body, usually alongside arteries
- Responsible for most blood return to the heart

3. Connecting (perforating) veins:
- Connect superficial and deep veins
- Allow blood to flow between the two systems

The general function of veins is to:

• Return blood to the heart - from various parts of the body
• Transport deoxygenated blood- (except for pulmonary veins)
• Act as a blood reservoir- storing extra blood when needed

How does blood pressure and blood flow change within arteries, capillaries, and veins?

Arteries:
• Highest blood pressure
• Rapid blood flow
• Thick, elastic walls to handle pressure

Capillaries:
• Significantly lower blood pressure
• Slowest blood flow
• Thin walls for easy exchange of substances

Veins:
• Lowest blood pressure
• Moderate blood flow
• Thinner walls with valves to prevent backflow

This gradual change in pressure and flow allows for efficient circulation and exchange of materials throughout the body.

Compare and contrast the tunic composition between arteries (elastic, muscular, arterioles), capillaries, veins (venule, medium size, large size) and what is the general function of each tunic.

Arteries, capillaries, and veins have different tunic compositions and functions:

Elastic Artery:
- Largest artery's
-Diameters 2.5cm to 1cm
- Aorta and major branches
-AKA conducting Arteries
Muscular Arteries
-distal to elastic arteries
-Diameter 1cm to 0.5mm
-unique feature, Internal and external laminae
Arterioles
-smallest arteries
-Diameter 0.3mm to 10Nm

Capillaries:
- smallest blood vessels
- 8-10 Nm
• Single layer of endothelial cells
• Function: Allow exchange of substances between blood and tissues

Veins:
• Three tunics, but thinner than arteries
• Function: Return deoxygenated blood to the heart under low pressure

How do elastic arteries and muscular arteries maintain relatively constant blood flow and pressure?

Elastic and muscular arteries work together to maintain relatively constant blood flow and pressure:

- Elastic arteries (e.g., aorta):
• Have high elastin content
• Expand during systole, storing energy
• Recoil during diastole, propelling blood forward
• Help dampen pressure fluctuations

- Muscular arteries:
• Have more smooth muscle in their walls
• Can constrict or dilate to regulate blood flow
• Adjust blood distribution to different organs based on need
• Help maintain overall blood pressure

This combination allows for efficient blood circulation and pressure regulation throughout the body.

Describe the following structures and their function: precapillary sphincter, true capillaries, metarteriole, through fare channel, intercellular clefts, tight junctions.

Precapillary sphincter - regulate the flow of blood tissue
True Capillaries -connect terminal arteriole to post capillary venule.
Metarteriole - Main source of branching
Intercellular clefts - gaps between cells that allow small molecules to pass through.
Tight Junctions- Protein complexes that act as semipermeable barrier is between epithelial and endothelial tissues.

How does material move out of the capillaries and into the interstitial tissue?

-Primarily through diffusion
-Hydrostatic Pressure

Why do some veins have valves?

prevent blood from flowing backward

What is the function of the blood brain-barrier?

• Prevents toxins: It prevents most blood-borne toxins from entering the brain.

• Selective permeability:
- Impermeable to most substances in the blood
- Allows essential nutrients like oxygen to pass through
- Permits passage of certain substances like alcohol, nicotine, and anesthetics.

• Not absolute: It's important to note that the blood-brain barrier is not an absolute barrier, allowing some substances to pass while blocking others.

This specialized barrier plays a crucial role in maintaining the brain's delicate environment and protecting it from potentially harmful substances in the bloodstream.

Describe the anatomy of the following capillaries: continuous and fenestrated.

Continuous Capillaries; Basement membrane, endothelial cells, tight junction, endothelia cells, RBCs in lumen, has nucleus.
Fenestrated Capillaries; Pores, increase permeability

15. Describe the anatomy and the function of sinusoids, where are they found.

Wide, leaky, capillaries; Occur in Bone marrow and spleen.

What are the two mechanisms that allow the movement of blood through the veins?

1. Skeletal muscle pump: Contraction of skeletal muscles compresses nearby veins, pushing blood towards the heart.

2. Respiratory pump: Changes in thoracic pressure during breathing help move blood in the veins.

3. Venous valves: One-way valves in veins prevent backflow of blood, ensuring it moves towards the heart.

4. Residual arterial pressure: Some of the pressure from arterial blood flow helps push blood through the capillaries and into the veins.

5. Gravity: In areas above the heart, gravity assists in venous return.

Define the following: vasoconstriction, vasodilation.

Vasoconstriction - is the narrowing of blood vessels, which reduces blood flow to a specific area of the body.

Vasodilation - is the widening of blood vessels, which increases blood flow to a specific area of the body.

(These processes are important for regulating blood pressure and blood flow throughout the body. They are controlled by various factors, including the autonomic nervous system and local chemical signals.)

During fetal development, is there a need for the pulmonary circuit? How does the developing heart by-pass the lungs and what happens to these structures after the infant is born?

During fetal development:
• The fetus receives oxygenated blood from the placenta
• The lungs are not functional for gas exchange
• Blood largely bypasses the lungs through fetal shunts (foramen ovale and ductus arteriosus)

After birth:
• The baby takes its first breath, expanding the lungs
• Fetal shunts close, separating the pulmonary and systemic circuits
• Blood flow is redirected through the lungs for gas exchange
• The heart transitions from a fetal to neonatal circulation pattern

These changes allow the newborn to adapt to breathing air and establish independent circulation.

Foramen Ovale open during fetal circulation
After birth the foramen ovale closes due to oxygen flowing, increasing pressure which closes the foramen ovale.

T/F ; Blood flow in capillaries is always very constant?

False

T/F; All arteries contain blood rich in oxygen?

False

T/F; The elastic arteries primary function is to determine which organs will receive blood ?

False

T/F Arteries transport blood away from the heart

True

T/F; The tunica external layer of blood vessels contains smooth muscle tissue

True

This vessel has a large tunica media

artery

This vessels has a large, dominant tunica Adventita (externa)

Vein

Most Blood is found in these vessels

Vein

This may have valves.

Veins

Most veins could be characterized not which of the following ?

They have large lumen compared too the thickness of their wall

Most Blood is found in which of the following ?

Veins