Cardiovascular 3

Question 1

What are the subdivisions of cathe cardiovascular system?

Answer 1

Heart: modified vessel that pumps blood through the network

Macrovessels: arteries and veins that serve as large conduit between organs and body parts

Micro vessels: capillaries and venules carrying metabolites, gases, immune cells and waste products

Question 2

What are the layers of large vessels of the cardiovascular system?

Answer 2

Large vessels (including the heart) are composed of 3 layers or tunics

Vessel:
1. Tunica intima

2. Tunica media (smooth muscle)
3. Tunica adventitia (outer connective tissue)

Heart:
1. Endocardium

2. Myocardium
3. Epicardium

Question 3

What are the types of arteries?

Answer 3

Elastic (conducting)

Muscular(distributing)

Question 4

What are elastic (conducting) arteries?

Answer 4

Large arteries

• leave the heart proper
• examples: aorta, common carotid, brachiocephalic arteries

Question 5

What is are muscular (distributing) arteries?

Answer 5

• deliver blood to the organs and small arteries

- examples: axillary, femoral arteries

Question 6

Describe elastic arteries

Answer 6

• Also known as large or conducting artery
• Elastic arteries conduct blood and help regulate the pulse so that blood moves at a steady flow despite the sharp contractions of the beating heart
• Propel blood along when ventricles are relaxing (pressure reservoir)
• Each of the tunics of the aorta have specific composition and function

Question 7

Describe the T. Intima of the elastic artery

Answer 7

Part of the elastic artery

T. Intima: is made up of endothelium, subendothelial connective tissue

-Well defined internal elastic lamina

Question 8

Describe the T. Media of the elastic artery

Answer 8

Part of elastic artery

Has 40-70 layers of elastic lamellae, smooth muscle cells

Well defined external elastic lamina

Question 9

Describe the elastic artery of the common carotid

Answer 9

Inset shows large amount of elastic fibers-imbricated arrangement

Note smooth muscle cells between elastic fibers(elongated nuclei)

Question 10

Describe T. Adventitia of elastic artery

Answer 10

T. Adventitia

• type 1 collagen, elastic fibers, fibroblasts and macrophages
• Prevents over dissension of the vessel
• Helps to anchor vessels to surrounding tissues
• Inner half of vessel wall is nourished from tunica intima while outer half is nourished from vaso vasorum (small blood vessels that supplies the tissues of larger vessels)

Question 11

Describe muscular arteries

Answer 11

• Are medium sized vessels
• Also refferred to as distributing arteries or named arteries
• Examples: brachial, radial, femoral, tibial etc
• Most abundant in the body
• Called muscular arteries because they contain more smooth muscles in the tunica media than elastic fibers
• Capable of greater vasoconstriction and vasodilation to regulate blood flow
• Muscular arteries serve as a conduit to distribute blood from elastic vessels to smaller vessels

Question 12

Describe the T. Intima of muscular arteries

Answer 12

• Distinct IEL (internal elastic lamina)

- The undulating (scalloped) appearance is a distinguishing characteristic

Question 13

Describe the T. Media of the muscular arteries

Answer 13

• up to 40 layers of smooth muscle cells arranged in circular fashion
• Few elastic fibers and collagen

Question 14

Describe T. Adventitia of the muscular arteries

Answer 14

Fibroblast, collagen and elastic fibers oriented longitudinally

• Allows changes in diameter and prevents retraction of vessels
• Vasa vasorum

Question 15

Describe the T. Intima, T. Media and T. Adventitia of the arterioles

Answer 15

Smallest arteries: range from 15-30 microns.

T. Intima: made up of endothelium

T. Media: has 1-2 layers of smooth muscle cells

T. Adventitia: ill-defined, blends with surrounding connective tissue, abundant, unmyelinated nerves

Question 16

What are arterioles?

Answer 16

Terminal end (metaarteriole), muscle cells form a precapillary sphincter

• can be closed down to generate high resistance to flow (resistance vessels)
• Major determinants of blood pressure ( R inversely proportional to 1/D^4

Question 17

What are capillaries?

Answer 17

Luminal diameter 5-10 microns

Single layer of endothelial cells + basal lamina

• Permit exchange of material
• Usually interposed between arteries and veins
• Different levels of metabolic exchange
• May be encircled by Pericytes (Rouget cells)
• Restricted “permeabilities” in some organs e.g. barriers in the brain, retina, thymus, testis etc

Question 18

What are the types of capillaries?

Answer 18

• Continuous/somatic
• Fenestrated/visceral
• Discontinuous/sinusoidal

Question 19

Describe continuous capillaries

Answer 19

• Continuous basal lamina
• no tight junctions
• no fenestrations in cytoplasmic membrane
• Found in C.T., muscle and nerve tissue, exocrine glands, tendon

Question 20

What are fenestrated capillaries?

Answer 20

• continuous basal lamina
• tight junctions present between cells
• fenestrations of about 70-100 nm on one cell membrane
• Presence of diaphragm in the fenestrations (+/-)
• Found in ciliary processes, choroid plexus, kidney, endocrine organs etc.