Lecture 27: The Cardiovascular System Flashcards Preview

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Flashcards in Lecture 27: The Cardiovascular System Deck (13):
1

List the three layers (tunics) of the heart wall.

Endocardium:
Myocardium
Epicardium

2

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)

3

Describe the myocardium

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

4

Describe the epicardium

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

5

What are Purkinje Fibers?

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

- See Slide 8-9

6

Describe Cardiac Skeleton

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

7

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.

8

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)

9

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

10

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

11

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

12

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.

13

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