Structure of vessels

Question 1

Function, mean pressure, and structural features in the left ventricle

Answer 1

Pump, 95mmHg, thick muscular walls inlet and outlet valves

Question 2

Function, mean pressure, and structural features in large arteries

Answer 2

Conduction, dampen flow from ventricles, 95mmHg, thick walls with abundant elastic fibres

Question 3

Function, mean pressure, and structural features in medium sized arterioles

Answer 3

Distributing arteries, 85-95mmHg, Muscular walls to control the diameter, connective tissue for strength.

Question 4

Function, mean pressure, and structural features in metarterioles.

Answer 4

Control pressure and flow, 35-85mmHg, smooth muscle to control diameter, little connective tissue.

Question 5

Function, mean pressure, and structural features in capillaries.

Answer 5

Slow flow and gas and nutrient exchange. 15-35mmHg, endothelium, no muscle of connective tissue.

Question 6

Function, mean pressure, and structural features in venules

Answer 6

Collecting vessels, 0-15mmHg, thin walled, large diameter

Question 7

Function, mean pressure, and structural features in veins

Answer 7

Include the named veins, transport of blood back to collecting vessels, low pressure, thin walled, variable structure (greater muscular media in legs)

Question 8

Function, mean pressure, and structural features in atrium

Answer 8

Collecting chamber for venous blood, pressure 0-2 mmHg, thin muscular walls

Question 9

Describe the layers of elastic arteries

Answer 9

Tunica intima- up to 20% of vascular wall, consists of endothelium and sub endothelial connective tissue which include longitudinal elastic fibres. Most deep is the internal elastic lamina.
Tunica media- Comprised of many lamelllar units made up of elastic lamina, smooth muscle, and collagen fibres. Most deep is external elastic lamina.
Adventitia- Contains collagen, elastic fibres, vasa vasorum and autonomic nerves.

Question 10

Describe layers of the muscular arteries

Answer 10

Tunica intima- endothelium, basement membrane of endothelium, sub endothelial connective tissue, distinctive internal elastic lamina (smooth in life but folds after death)
Tunica media- smooth muscle fibres to control the diameter of the vessel, elastin fibres (resiliency), collagen fibres to limit expansion and prevent rupture, sometimes an external elastic lamina.
Tunica adventita- Collagen and elastic fibres with vasa vasorum

Question 11

Describe a berry aneurysm

Answer 11

An arterial disease, where bleeding occurs into the media wall.

Question 12

Describe a dissecting aneurysm

Answer 12

Where the tunica intima allows blood to enter the vessel wall forcing the layers apart. There is a high risk of death if it ruptures

Question 13

Describe hypertension

Answer 13

Thickening of the artery wall (smooth muscle hypertrophy) and adventia thickening. Narrow lumen, duplication of the internal elastic lamina.

Question 14

Describe the layers of the arterioles

Answer 14

Intimate endothelial cells overlying a basement membrane, then internal elastic lamina.
Three or fewer layers of smooth muscle in the media
Wall thickness about equal to the diameter of the lumen

Question 15

Why can’t capillaries adjust their diameter?

Answer 15

No smooth muscle or connective tissue

Question 16

What does the microcirculation consist of?

Answer 16

Small arterioles, the capillary bed, postcapilliary venules

Question 17

What controls the blood flow into the microcirculation?

Answer 17

Arterioles, terminal arterioles and metarterioles. There are also precapilliary sphincters which control the entry into each capillary. Relaxation of smooth muscle in all of these locations allows blood to flow into the capilliaries

Question 18

What is the internal diameter of capillaries?

Answer 18

8-10 micrometers

Question 19

Describe the layers of capillaries

Answer 19

Endothelium, basement membrane. Some are fenestrated

Question 20

Where would you find continuous capillaries with closed intercellular clefts

Answer 20

CNS. Creates the blood brain barrier

Question 21

Where would you find continuous capillaries with open intercellular clefts?

Answer 21

Muscle, connective tissue, lungs. Allows the passage of water, ions and small molecules but not plasma proteins

Question 22

Where do you find fenestrated capillaries with closed perforations

Answer 22

Fenestrations are closed with a very thin membrane. These capillaries are found in the intestine

Question 23

Where would you find fenestrated capillaries with open fenestrations?

Answer 23

In the endocrine glands and kidney glomeruli

Question 24

Describe sinusoids

Answer 24

Large bore capillaries with wide gaps between endothelial cells allowing easy passage of large molecules and whole cells. Found in the bone marrow, spleen, and liver.

Question 25

Describe postcapillary venules, structure and response in inflammation.

Answer 25

10-25 micometers in diameter. Lack smooth muscle but have pericytes (contractile cells). During inflammations these venues respond to histamine and serotonin by becoming more leaky.

Question 26

Describe muscular venules

Answer 26

Larger venues with two layers of smooth muscle in the media. Thin wall relative to lumen- endothelial nuclei budge into lumen

Question 27

Describe veins

Answer 27

Conduct blood at low pressures so thin walled, large lumen. Structure resembles muscular arteries but all three tunics reduced in thickness, the internal elastic lamina is not well developed- in death the veins collapse due to lack of muscular media. Have bicuspid valves to prevent back flow made from folds of the tunica intima

Question 28

Which veins are most muscular

Answer 28

Those in the legs as there is significant pressure on them when standing

Question 29

What pressure does gravity exert on veins and how is the lower limb venous blood pushed upwards

Answer 29

100mmHg per 136cm column. This is dissipated through valves. The leg muscles work as pump squeezing the blood upwards when the muscles contract around the veins.

Question 30

What increases risk of venous thrombosis and where does the blood clot likely lodge

Answer 30

Any event that slows blood flow, increases coagulability, or damages endothelium. Surgery, childbirth, trauma, contraceptive pills, long flights. Lodges in the pulmonary tree

Question 31

Describe varicose veins

Answer 31

When the superficial veins of the legs become dilated sufficiently that the valve cusps no longer meet and there is back flow of blood resulting in dilated tortuous veins.

Question 32

About how much fluid and plasma proteins are lost daily into the interstitial fluid

Answer 32

3 litres or water and 120gm plasma proteins

Question 33

What is the function of lymphatic fluid

Answer 33

To return lost fluid and plasma proteins and immune function

Question 34

Describe the structure of lymphatic capillaries

Answer 34

Endothelial cells tethered to surrounding connective tissue by anchoring filaments, when the connective tissue becomes swollen with fluid it pulls on the filaments widening the lymphatic capillaries increasing their drainage. No basement membrane Large gaps between endothelial cells allowing passage of large molecules and protiens

Question 35

Describe larger lymphatic vessels

Answer 35

Resemble veins except with thinner walls and more valves

Question 36

Pathway of lymphatic vessels

Answer 36

Lymphatic capillaries, lymphatic vessels, lymph nodes, lymph vessels, lymphatic duct (right subclavian), thoracic duct (left subclavian).

Question 37

Name tissues that don't contain lymphatic vessels

Answer 37

CNS, cartilage, bone, bone marrow, thymus, cornea, teeth.