Histology Of The Cardiovascular System (Exam II)

Question 1

List the functions of the Cardiovascular System

Answer 1

Maintenance of adequate blood flow.
Delivery of O2, nutrients, hormones ,electrolytes and water to peripheral tissues.
Removal of CO2 and other metabolic waste products
Maintenance of normal thermoregulation and glomerular filtration rate

Question 2

Describe the flow of blood through vessels.

Answer 2

Artery–> Arteriole –> Metarteriole –> Capillaries –> Venule –> Vein

Question 3

Where are Purkinje Fibers located

Answer 3

Subendocardium - thin layer of CT

Question 4

What is the epicardium made of? What do these cells do?

Answer 4

Epicardium is formed by a single layer of flattened epithelial cells, the mesothelium - supported by CT including fat.
Mesothelial cells secrete small amount of serous fluid that lubricates the movement of the epicardium on opposite parietal pericardium.

Question 5

What else does the epicardium represent in regards to the pericardium?

Answer 5

It represents the visceral layer of the pericardial sac.

Question 6

Describe the 2 regions of intercalated discs.

Answer 6

Transverse Regions - Desmosomes - hold cell tightly together

Longitudinal Regions - Gap Junctions - electrical synapses

Question 7

Describe the Myocardium

Answer 7

Cross striated
Single, central nucleus
Intercalated discs
Lipofuscin
Sarcoplasmic reticulum
Many mitochondria - requires a lot of O2

Question 8

Describe the epicardium

Answer 8

The outer surface of heart (visceral pericardium)
Surface covered by mesothelium (simple squamous epithelium), a thin layer of dense CT and potentially a layer of adipose tissue with blood vessels
Is contiguous with the endocardium at the level of endocardial cushion.

Question 9

What is the cardiac skeleton?

Answer 9

Consist of 4 dense bonds of fibrous CT that encircles the base of the pulmonary trunk, aorta and the AV valves - provides structural support to the heart.

Question 10

What is the fibrous trigon?

Answer 10

Triangular mass of CT the connects the aortic arterial ring and the left and right atrioventricular ring.

Question 11

What happen in the fibrous trigon as animals age?

Answer 11

Can undergo osseous differentiation and forms the “Os Cardis” - primarily in cattle - will see bone in the heart of these older cattle

Question 12

Describe the main differences between arteries and veins.

Answer 12

Vein - larger lumen, valves, thickest wall is tunica externa

Artery - smaller lumen, no valves, thickest wall is tunica media

Question 13

Describe a capillary’s structure.

Answer 13

Thin wall of endothelium.

Question 14

What are the 3 tunics of vessels and what are they composed of?

Answer 14

Tunica Intima - endothelium, internal elastic membrane, subendothelial CT
Tunica Media - smooth muscle, elastic lamellae/fibers
Tunica Adventitia/Externa - CT, principally collagen, may contain blood vessels, nerves, capillaries

Question 15

What are the roles of the vascular endothelium? BE SPECIFIC.

Answer 15

Role in Hemostasis: anti-thrombotic and pro-fibrinolytic in normal state; pro-thrombotic and anti-fibrinolytic during injury
Modulates Perfusion: Nitrous Oxide - vasodilation; Endothelin - vasoconstriction
Role in Inflammation: regulates traffic of inflammatory cells, produces pro-inflammatory cytokines, control angiogenesis and tissue repair

Question 16

What is hemostasis? How does endothelium accomplish this??

Answer 16

Arrest bleeding by physiological properties of vasoconstriction and coagulation or by surgical mean.

Endothelium has pro-thrombotic and anti-fibrinolytic during injury and anti-thrombotic and pro-fibrinolytic in normal state.

Question 17

What is the vaso vasorum and what is its purpose?

Answer 17

Vaso Vasorum - present in the tunica adventitia/externa to supply nutrients to larger vessels.

Question 18

The valves of veins are made of what?

Answer 18

They are invaginations of the tunica intima. They are covered by endothelial cells and have a core of elastic fibers.

Question 19

Give an example of an elastic artery. How are the tunics of this artery different?

Answer 19

Aorta.
Tunica Media consists largely of repeating elastic lamellae and elastic fibers.
Has all 3 tunics.

Question 20

Give an example of a muscular artery. How are the tunics of this artery different?

Answer 20

Femoral Artery.
Tunica media is primarily smooth muscle.
These arteries are generally round in cross-section. Prominent internal elastic membrane.

Question 21

What is the purpose of vascular smooth muscle?

Answer 21

Regulates diameter and tone of vessels (vasoconstriction, vasodilation).
Smooth muscle cells are arranged circumferentially within tunica media.

Question 22

Describe the structure of arterioles.

Answer 22

1-3 layers of smooth muscle. 
Has greatest effect on BP.
Nuclei bulge into lumen ***
Round appearance of vessel
No internal elastic membrane in smallest arterioles with 1 smooth muscle layer.

Question 23

What are metarterioles?

Answer 23

Terminal vessel.

Has precapillary sphincter that can regulate flow into capillary bed.

Question 24

What are pericytes?

Answer 24

Mesenchymal like contractile cells (contain actin, myosin, tropomyosin) that wrap around capillaries and ventless and “Communicate” with endothelial cells by physical contact and paracrine signaling.
Have own basal lamina.

Question 25

What is the purpose of pericytes? Where are they often found?

Answer 25

Pericytes proliferate after injury. May be replacement stem cell source. Important in angiogenesis - new vessel formation.
Pericytes are often in close proximity with capillary - have tight junctions with capillary endothelial cells.

Question 26

What are capillaries?

Answer 26

Thin walled tubules of mesenchymal origin. Only one endothelial cell rolled into a tube.
Represent the site of exchange between blood and surrounding tissue.

Question 27

What are continuous capillaries? Where are they found?

Answer 27

Most common.
Found in muscle, brain, bone
No holes in wall.

Question 28

What are fenestrated capillaries?

Answer 28

Have gaps 10-100nm in size (tiny little holes).
Found in tissues with substantial fluid exchange.
Intestinal villi, choroid plexus, ciliary process, glomerular capillary.

Question 29

What are discontinuous (sinusoidal) capillaries?

Answer 29

Large molecules can exit (RBC, etc.)
Hepatic and Splenic Sinusoids.
Lumen enlarged and irregular.
Basal lamina may be absent.

Question 30

What is the renal corpuscle (glomerulus)?

Answer 30

Tightly coiled network of fenestrated capillaries. Responsible for the filtration of plasma.

Question 31

What are venules?

Answer 31

Post capillary venules.
Very “leaky” vessels.
No smooth muscle.
Leukocyte diapedesis is possible here.

Question 32

What are lymphatic vessels?

Answer 32

Very thin wall, very low pressure, may contain valves.
No RBC in lymph - appear clear on slide.

Lymphatic capillary has similar morphology to a capillary.