L: Blood vessels and lymphatics

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What are the types of blood vessels (7)

• elastic arteries

• muscular arteries

• arterioles

• capillaries

• venules

• medium veins

• large veins

What is the innermost layer of blood vessels called?

The tunica intima.

What does the tunica intima consist of?

Endothelium, sub-endothelial layer, internal elastic membrane (arteries only)

What type of epithelium lines the tunica intima?

Simple squamous epithelium.

What does the tunica media consist of?

Smooth muscle and elastic fibres (external elastic membrane in arteries).

How is smooth muscle arranged in the tunica media?

Concentric layers of smooth muscle.

What is the thickest layer of arteries?

Tunica media - much thicker than in veins.

What type of nerve fibres does the tunica media contain?

Sympathetic vasomotor nerve fibres.

What are the functions of sympathetic vasomotor nerve fibres?

Vasoconstriction (decreases lumen size) and vasodilation (relaxes).

What makes up the tunica externa?

collagen fibres, elastin, vasa vasorum

What type of collagen is primarily present in the tunica externa?

Type 1.

What is the thickest layer in veins?

The tunica externa.

What does the tunica externa contain?

nerve fibres, lymphatic vessels, (and elastic fibres in larger veins)

How is tissue orientated in the tunica externa?

It is a longitudinally orientated sheath.

What is the difference in layers between a muscular artery and a elastic artery?

The muscular artery doesn’t have an internal elastic layer within the tunica intima, while the elastic artery does.

What is another name for the tunica externa?

Adventitia.

What is vasa vasorum?

A network of small blood vessels in the largest vessels, such as the aorta, brachiocephalic artery and coronary arteries.

Where do vasa vasorum branch?

Profusely in the tunica externa and in the outer part of the of the media.

What is the function of vasa vasorum?

They nourish the outer layers of vessels and respond to nutrient needs.

What are elastic arteries?

Large, thick-walled arteries located near the heart.

What do elastic arteries contain - more than other vessels?

Elastin.

Which layer of elastic arteries has the most elastin?

Tunica media.

What does a large lumen mean in conducting arteries?

Lower resistance.

What happens to elastic arteries during systole and diastole?

Expansion and recoil - enables continuous flow of blood.

What are the branches of the aorta (superiorly)?

Brachiocephalic trunk branching into → right common carotid artery and right subclavian artery, left common carotid artery, left subclavian artery.

What branches off from the right common carotid?

Right internal carotid - same on the left.

How do the muscular arteries differ from elastic arteries in the tunica media?

They have more smooth muscle and less elastic tissue.

Which type of artery is more active in vasoconstriction?

Muscular arteries.

What does vasoconstriction allow muscular arteries to do?

Regulate blood flow and control distribution to tissues.

How can muscular arteries prevent haemorrhages?

By contracting.

What is an ischaemic area?

A part of the body with insufficient blood flow.

If there was occlusion of a principal artery to a region, what would carry blood tp the area?

Collateral muscular arteries.

Name the upper limb arteries?

Subclavian, axillary, brachial (same vessel, different locations), branches into radial and ulnar.

What arteries are present in the hands?

The deep palmar arch and the superficial palmar arch (more distal).

What are anastomoses?

The joining of two or more blood vessels.

What do all joints have around them?

Anastomoses.

What arteries are derived from both the radial and ulnar arteries?

The deep and superficial palmar arches.

What is the location of the inferior phrenic artery?

Just below the diaphragm.

Is the celiac artery superior or inferior to the renal arteries?

Superior.

What are the arteries that branch off from the aorta in the pelvic area?

Median sacral, left and right common iliac → internal iliac, external iliac → deep circumflex iliac and inferior epigastric, femoral.

What is the arrangement of the femoral artery, vein and nerve?

femoral nerve most laterally, then the artery, then the vein.

What is the relation between the femoral artery, vein and nerve important for?

For taking blood or inserting an arterial canulae.

Name the lower limb arteries (above the knee) extending from the aorta.

Aorta, common iliac → internal iliac, external iliac, femoral, profunda femoris (deep femoral), (superficial) femoral, popliteal.

Name the arteries extending from the popliteal artery (below the knee).

Popliteal → anterior tibial and tibio-peroneal (tibio-fibular) trunk → peroneal (fibular) and posterior tibial.

What size range do arterioles have?

0.3mm - 10um.

What layers do large arterioles have?

All three tunica layers.

What layers do small arterioles have?

A single layer of smooth muscle (tunica media) and endothelium.

What does arteriolar diameter determine?

Blood flow to tissues/organs.

What happens when arterioles constrict?

Resistance is increased and this influences the blood flow to capillary beds and blood pressure within tissues.

What is a metarteriole?

The capillary bed end of an arteriole.

What exists at pre-capillary junctions?

Sphincters that control blood flow within the tissues.

What is vasomotion?

Rhythmic oscillation that occurs in many blood vessels.

Blood flow maintains blood pressure to vital organs in response to what influences?

Neural, hormonal and chemical.

What are the layers present in capillaries?

Endothelial cells supported on a basal laminae.

What is a network of capillaries called?

A capillary bed.

What is the function of capillaries?

Exchange of O₂ , CO₂ , nutrients and hormones between cells/interstitial fluid and blood.

How do capillaries exchange materials?

active transport and passive transport (osmosis, diffusion, filtration and facilitated transportation).

What are the three capillary types?

Continuous, fenestrated and sinusoid.

What is the most common capillary type?

Continuous capillaries.

Where are continuous capillaries found?

Skin, muscle, lungs, CNS

What is the least permeable type of capillary?

Continuous.

What is the name of the cells associated with continuous capillaries?

Pericytes.

What do fenestrated capillaries have for active filtration?

Large pores.

Where are fenestrated capillaries found?

Kidneys, small intestines and in areas of hormone secretion.

What is the least common capillary type?

Sinusoid capillaries.

Where are sinusoid capillaries found?

The liver, bone marrow, spleen.

What is the speed of blood flow through sinusoid capillaries?

Slow.

What is the most permeable capillary type?

Sinusoid.

What do sinusoid capillaries allow for the passage of?

Large molecules and cells.

Capillaries unite to form what?

Venules.

What does extravasate mean?

Accidental leakage.

What feature venues allow white blood cells to extravasate to sites of inflammation?

They are extremely porous.

Which blood vessels are conducting?

Arteries.

Which blood vessels are capacitance vessels?

Veins.

What percentage of blood volume do veins carry?

65%.

What prevents back flow in veins and what is it formed from?

Venous valves and they are formed from the tunica intima.

Why does a large lumen mean that veins are at low risk of bursting?

There is little resistance.

When do venous valves close?

When blood pressure proximal to the valves is greater than distal.

What three things can aid venous return of blood?

• Associated arteries

• muscle contraction

• respiratory pump - thoracic and abdomen pressure changes as result of breathing.

What would veins be associated with arteries?

Artery pulsation can aid movement of blood within veins.

What are venae comitantes?

Deep veins that accompany smaller arteries.

What do deep veins accompany?

Arteries, they are situated deeply and have the same names (femoral vein, femoral artery)

What are two examples of superficial veins in the leg?

The great saphenous vein (upper leg), the small saphenous vein (lower).

What connects superficial veins to deep veins?

Perforating veins.

Which direction is venous flow (superficial and deep veins)?

Flow is from superficial to deep veins - due to valves inside perforating veins.

What does incompetency of the valves within veins lead to?

Varicose veins.

What do radial and ulnar veins unite to form?

The brachial vein → axillary vein → subclavian vein

Which veins are widely used for phlebotomy?

Superficial veins.

What are examples of superficial veins (in the upper limb)?

cephalic vein, basilic vein, median cubital vein.

What connects the cephalic and basilic veins?

The median cubital vein.

Which nerve does the cephalic vein lie next to?

The radial nerve.

Which is more medial, the cephalic vein or the basilic vein?

The basilic vein.

What must be avoided when taking blood?

The brachial artery and the median nerve (posteriorly).

Where does venous blood drain from into the inferior vena cava (IVC)?

Lower limbs, pelvic organs, kidneys and abdominal walls.

Where does venous blood drain from into the superior vena cava?

The head, neck and upper limbs.

Which veins drain into the SVC?

The internal/external jugular and subclavian veins draining into the brachiocephalic vein which drains into the SVC.

Which vein drains the venous blood of the posterior thoracic wall (to SVC)?

The azygos vein.

What does it mean to say that the azygous system is unpaired?

It does not follow an arterial supply - its veins don’t run alongside associated arteries.

Instead of returning directly to the heart, what does venous blood from Gastrointestinal tract components and the spleen do?

It forms the Hepatic portal vein, which takes venous blood through the liver before it then joins the inferior vena cava.

Where does the hepatic portal vein take blood through before joining the inferior vena cava?

The liver.