Blood Vessels Flashcards
What are the three main functions of blood vessels?
- Supply oxygen
- Supply nutrients to body tissues
- Remove metabolic wastes
What are the three layers of a general wall in blood vessels?
Lumen of blood vessel
- Tunica intima
- Tunica media
- Tunica adventitia
What are the two types of capillaries?
- Continuous
- Fenestrated
What are two types of arteries?
- Muscular
- Elastic
What is the largest elastic artery in the body?
The aorta
What type of cells in the tunica media of large arteries makes elastin?
Smooth muscle cells
Smooth muscle fibers occur in what blood vessels? Why?
All vessels larger than capillaries
For vasoconstriction and vasodilation
What types of fibers are in the connective tissues of blood vessels?
- Collagen is in the subendothelial layer and between smooth muscle layers
- Elastin is found in between smooth muscle layers
What are the three components of the tunica intima?
- Endothelium
- Subendothelial layer of loose connective tissue sometimes containing smooth muscle
- Internal elastic lamina composed of elastin (in arteries and large veins)
What are the two components of the tunica media?
- Concentric layers of helically arranged smooth muscle cells
- Elastic fibers interspersed between muscle fibers
What are the five components of the tunica adventitia?
- Type I collagen
- Elastin fibres
- Nerve fibers that release vasoconstrictor (more in arteries)
- Vasa vasorum (more in veins)
- Lymphatic capillaries
What are vasa vasorum?
Arterioles, capillaries and venules in the tunica adventitia of large blood vessels.
What type of blood vessels contains the most amount of vasa vasorum? Why?
Veins, their blood is deoxygenated
What are the two elastic arteries in the body?
- Aorta
- Pulmonary artery
As well as their largest branching arteries
What is characteristic of elastic arteries?
They have a very thick tunica media with alternating layers of elastic lamellae and smooth muscle
In what vessels is the internal elastic lamina hard to differentiate? Why?
Elastic arteries, because of the abundance of elastic lamellae in the tunica media
What does elastin do for arteries?
- Distends wall under pressure until it hits the limit imposed by collagen
- Rebounds with low pressure to maintain arterial pressure
What are two distinct characteristics of muscular arteries?
- Very thin subendothelial layer in the tunica intima
- Distinct internal elastic lamina
When is an external elastic lamina present?
In the largest of muscular arteries
What is the wall of arterioles like? (4)
- Tunica intima has very thin subendothelium
- Elastic laminae are absent
- Circularly arranged smooth muscle in tunica media
- Thin tunica adventitia
Which vessels are the major determinant of systemic blood pressure? How?
Arterioles, by always having partially constricted smooth muscle in the tunica media
What are arteriovenous shunts?
Arterioles that bypass capillary beds and connect directly to venules. Used in thermoregulation.
What type of cells compose capillaries?
Endothelial
A variable number of what type of junction plays a role in capillary permeability?
Tight junctions
What are the three types of capillaries?
- Continuous (muscle, connective tissue etc.)
- Fenestrated (eg. kidneys, intestine)
- Discontinuous (sinusoidal) (eg. spleen, liver, bone marrow)
What are pericytes?
Mesenchymal cells with long cytoplasmic processes partly surrounding the endothelial layer (embedded in basement membrane) of continuous capillaries and postcapillary venules. These are contractile and facilitate blood flow.
Stem cells for generating new vasculature
What is the characteristic feature of venules?
Large lumen with thin walls
What propels blood through veins? (2)
- Contraction of smooth muscle in tunica media
- External compression from surrounding muscles and other organs.
What part of a blood vessel are valves? Where are valves most common?
Tunica intima projections
Most common in veins of legs
What are differences between small/medium and large veins?
- Large veins have thick intima, thin media and thick tunica adventitia
- Large veins have longitudinal bundles of smooth muscle in the tunica adventitia
What is lymph before it is collected?
Interstitial fluid
What is the purpose of lymphatic vascular system?
To collect excess interstitial fluid and return it to the blood as well as distributing lymphocytes, antibodies and other immune components through the body and its various lymph nodes
Lymphatic vessels most resemble which type of blood vessel? What are the three exceptions?
Veins
- With thinner walls
- And no clear differentiation between tunica layers
- More numerous endothelial valves than veins
What is the systemic circulation pressure?
90-100 mmHg
What is the pulmonary circulation pressure?
30-40 mmHg
The internal elastic lamina in blood vessels separates:
Tunica intima from tunica media
External elastic lamina in blood vessels separates:
tunica media and tunica adventitia
How can large materials be moved from inside continuous capillaries to outside them into surrounding tissue?
Capillary endothelial cells controlling pinocytosis (pinocytotic vessicles)
The largest arteries are ____ arteries with 50% ____
The largest arteries are elastic arteries with 50% elastin
The smallest arteries are ____ arteries with 50% ____
The smallest arteries are muscular arteries with 50% smooth muscle
