Anatomy of the CVS 2: histology of blood vessels

Question 1

What are the 3 tunics of blood vessels?

Answer 1

• Tunica intima
• Tunica media
• Tunica externa/adventitia

Question 2

What are the 3 layers of the heart wall?

Answer 2

• Endocardium
• Myocardium
• Epicardium

Question 3

What is the tunica intima composed of?

Answer 3

Epithelium + BM + Connective tissue

Question 4

What is the tunica media composed of?

Answer 4

Muscle + Elastic tissue

Question 5

What is the tunica externa (adventitia) composed of?

Answer 5

Fibrous connective tissue

• Connective tissue is to anchor the vessel and support it.

Question 6

Differences between arteries and veins

Answer 6

• Arteries smaller diameter than accompanying vein.
• Arteries thicker wall than accompanying vein.
• Arteries thick media thin adventitia.
• Veins thin media thick adventitia.

Question 7

What are the diameters of arteries, capillaries and arterioles from biggest to smallest?

Answer 7

Arteries > Arterioles > Capillaries

Question 8

What are the 3 types of arteries?

Answer 8

• Elastic
• Muscular
• Arterioles

Question 9

Features of elastic arteries

Answer 9

• Large conducting

e. g. aorta, common carotid, pulmonary.

Question 10

Features of muscular arteries

Answer 10

• Distributing arteries
  e. g. coronary arteries, radial, femoral.

Muscular arteries are essentially conducting the blood towards the organ.

Question 11

Features of Arterioles

Answer 11

• Terminal branches which supply blood to capillary bed.

Question 12

Why can’t you see the smooth muscle in Elastic arteries upon miscroscopy?

Answer 12

Because it is covered by elastic fibres in the media.

• The elastic fibres are secreted by smooth muscles.
• Elastic fibres are stretched during systole.

Question 13

in muscular arteries, which tunic contains smooth muscle cells?

Answer 13

• Thick tunic media has smooth muscle cells.

- No elastic laminae between muscle cells in tunic media.

Question 14

In muscular arteries, where are the elastic fibres found?

Answer 14

-Elastic fibres are concentrated in 2 well defined sheets called the internal elastic lamina (IEL) just under epithelium, and the thin external elastic lamina (EEL) between T.media & T. adventitia

Question 15

How are arterioles formed and what do they contain?

Answer 15

• The smaller muscular arteries gradually change histologically to become arterioles.
• No IEL (internal elastic lamina)
• No T.adventitia

However, they have a rich sympathetic nerve innervation.

Question 16

Features of capillaries

Answer 16

• Main exchange site for nutrients, gases.
• Therefore very thin walled
• T. intima only: endothelium on BM
• No T. media
• No T. adventitia
• Pericytes: incomplete layer of cells surrounding basement membrane – have contractile properties which help control flow of blood in the capillaries.
• Blood pressure in capillaries is LOW.

Question 17

What are the 3 types of capillaries?

Answer 17

1. Continuous
2. Fenestrated
3. Discontinous

Question 18

Features of continuous capillary

Answer 18

• Can control what is exchanged
• Material must pass through cell, or between cell(junctions can control)
• Selective transport mechanisms
• Eg. in muscle

Question 19

Example OsPe question

Answer 19

What kind of capillary is this, and give an example of where you would find this kind of capillary?

Question 20

Features of Fenestrated capillary

Answer 20

• Have fenestrations (or pores)
• Fenestrations up to 100μm
• With or without protein diaphragms
• Diaphragms filter molecules by MW &/or charge
• Eg. endocrine glands, kidney renal corpuscle

Question 21

Feautures of discontinuous capillaries

Answer 21

• Gaps between endothelial cells (and basement membrane)
• Allow free passage of fluid and cells
• Eg. liver, spleen, bone marrow

Question 22

What are Sinusoids and features of them?

Answer 22

• Large diameter discontinuous capillaries
• Found where large amount of exchange takes place
• T. intima contains phagocytic cells
• e.g. liver, some endocrine glands

Question 23

Do arteriovenous (AV) shunts bypass capillary beds?

Answer 23

Yes

e.g. in skin for thermoregulation

Question 24

Features of Superficial veins

Answer 24

• Thick walled
• No surrounding support
• Superficial veins will eventually drain blood into the deep veins!!

Question 25

Features of Deep veins

Answer 25

• Thin walled
• Surrounding support from deep fascia and muscles
• Deep veins have a corresponding artery nearby

Question 26

Features of the Lymphatic system

Answer 26

• Drains tissue fluid lost from blood capillaries
• Drains into the systemic venous system
• Nodes found alongside major veins and around origins of major arteries
• Valves direct from

Question 27

What is the lymphatic system clinically important for (bad)?

Answer 27

Tumour cell metastases

Question 28

Features of Lymph capillaries

Answer 28

• Blind-ended capillaries
• Lined by very thin endothelium
• No fenestrations
• Absent/rudimentary basal lamina
• Lumen maintained at nehative hydrostatic pressure
• Anchoring filaments: fine collagenous filaments link endothelial cell to surrounding tissue keeping lumen open.
• NO red blood cells in lumen

Question 29

Nerve supply in blood vessels as organs

Answer 29

• Sympathetic e.g. skin

- Sympathetic + parasympathetic e.g. heart

Question 30

Blood supply in blood vessels as organs

Answer 30

• Thick blood vessels have blood vessels of their own in the adventitia called VASA VASORUM, “vessels of the vessels”

Question 31

Where as lymphatics in blood vessels found?

Answer 31

In T.adventitia