Lecture 27: The Cardiovascular System Flashcards Preview

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Flashcards in Lecture 27: The Cardiovascular System Deck (13)
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List the three layers (tunics) of the heart wall.



Describe the endocardium

* Innermost layer, lining the atria and the ventricles
* Components:
- Endothelium
- Subendothelial connective tissue
* Continuous with the tunica intima of the blood vessels entering and leaving the heart
* Subendocardiumis a layer located between the endocardium and the myocardium:
- Contains nerves and Purkinje fibers (subendocardial fibers)


Describe the myocardium

Consists of cardiac muscle cells. That's about it.


Describe the epicardium

* External surface is covered by simple squamous epithelium (mesothelium).
* Mesothelium overlies fibroelastic connective tissue containing adipose cells, nerves, and coronary vessels.


What are Purkinje Fibers?

* Large, specialized cardiac muscle cells
* Carry impulses to ordinary cardiomyocytes

- See Slide 8-9


Describe Cardiac Skeleton

- Dense collagenous connective tissue
- Myocardial fibers originate and insert into the cardiac skeleton.


The Walls of all blood vessels except capillaries are characterized by three vascular layers (tunics).
Describe the tunica intima?

* Components:
- Endothelium and its basal lamina
-- Found in all arteries and arterioles
-- Endothelial cells produce von Willebrand’s factor VIII.
- Subendothelial connective tissue:
-- Found in all elastic and muscular arteries and some arterioles
- Internal elastic membrane:
-- Incomplete in elastic arteries but thick and complete in muscular arteries.


The Walls of all blood vessels except capillaries are characterized by three vascular layers (tunics).
Describe the two layers that "aren't" the tunica intima.

* Tunica media:
- Made up of circular smooth muscle tissue and fibroblasts
- Contains collagen and elastic fibers
* Tunica adventitia:
- Outermost layer: Lacking in arterioles
- Consists of loose areolar tissue
- Contains irregular fibroelastic tissue with adipocytes
- Has small vessels (vasa vasorum) and nerves (nervi vasorum)


Describe the relationship between vascular anatomy (size and shape) vs. blood pressure.

* Note the drop in pressure as arteries leave the heart and become progressively smaller.
* The structure of the tunic, especially the tunica media changes from that of an elastic tunic to that of a muscular tunic.
* The more elastic arteries are conducting arteries.
* The more muscular arteries are distributing arteries.

- See Slide 13-14


Describe the elastic artery

* Conducting arteries
* Stretch during systole and recoil during diastole
* Tunica media consists of layers of elastic fibers organized into elastic laminae:
- 40 layers in newborn to 70 layers in older adult
- Connective tissue is interspersed between the elastic laminae.
* Include:
- Aorta
- Pulmonary trunk
- Large branches of aorta


Describe the muscular artery

* Distributing arteries
* Tunica media consists of smooth muscle that responds to autonomic stimulation and hormones:
- Thickness of smooth muscle layer decreases as diameter becomes smaller.
- Gradual transition from elastic artery to muscular artery
* Include: All named arteries of body except elastic arteries

- See Slide 18


Describe arterioles

* Small arteries
* Tunica media consists of one to three layers of smooth muscle cells.
* Mean arterial pressure depends on proper tone of smooth muscles in arterioles (peripheral resistance arterioles).
- Thickness of smooth muscle layer decreases as diameter becomes smaller.
* Give rise to metarterioles which have a discontinuous layer of smooth muscle tissue.
* Microcirculation: Components and function:
- Pericytes:
-- Undifferentiated mesenchymal cells
-- May be contractile
-- May serve as stem cellsto differentiate into fibroblasts, etc.

- See Slide 21-24. And notice what he said on that last one.


Compare veins to arteries.

What are the characteristics of lymphatics?

* Comparison with arteries:
- Larger lumen
- Thinner wall
- Valves are present in many veins.
* Larger veins have a layer of longitudinal smooth muscle in the inner aspect of the tunica adventitia.

* Lymphatic Characteristics:
- Single layer of endothelial cells
- Basal lamina may be absent
- Anchoring filaments
- Valves in larger lymphatics
- See Slide 26-32