Blood vessels and Lymphatics Flashcards
Describe the overview of circulation
Pump (heart) to arterial system to capillary bed (to lymphatic) to venous system and then back to the heart
What is the difference between Veins and Arteries in terms of tissue type?
Veins are mainly collagenous, fibrous tissues
Arteries are mainly muscular tissues
What are the three layers of all blood vessels and briefly state their tissue type?
- Tunica interna (intima): endothelium and connective tissue
- Tunica media: muscle and connective tissue
- Tunica externa (adventitia): thick layer of connective tissue
What is Tunica interna’s lining?
It is lined by specialized simple squamous epithelium called endothelium
Where does the endothelium lining stop?
It is continuous throughout the entire vascular system
What hormones does endothelium release?
Endothelins, and they constrict the smooth muscle within the walls of the vessel (to increase BP)
What is the role of basal lamina?
It is the basement membrane that effectively binds to the endothelium to the connective tissue
What is the thick layer found in larger arteries?
Internal elastic membrane
Where is the internal elastic membrane?
Located at the boundary with the tunica media in larger arteries beneath tunica interna
What is the purpose of the internal elastic membrane in large arteries?
It provides structure while allowing the vessel to stretch
What type of muscle cells are the lining of vessels contained of?
Smooth muscle cells
What is the thickest layer in arteries?
Tunica media
What is the thickest layer in veins?
Tunica externa
Define vasoconstriction and vasodilation and state their importance
Vasoconstriction is the contraction of the circular muscles (this decreases the diameter of the vessel lumen which increases the BP)
Vasodilation is the relaxation of the circular muscles (this increases the diameter of the vessel lumen which decreases the BP)
What is the tunica media composed of?
Concentric layers of helically-arranged smooth muscle cells
What type of fibres does the tunica externa contain?
Primarly composed of Collagen I fibres
What arteries are closest to the heart?
Elastic large arteries
Describe elastic arteries and name few
They are conducting arteries closest to the heart.
They expand during systole, and elastic recoil during diastole.
Aorta and pulmonary artery are elastic arteries.
What is the function of muscular arteries?
They control distribution of blood to regions and organs
They regulate blood flow (by constriction or relaxation of their walls)
How do muscular arteries regulate blood flow?
By constriction and relaxation of their walls
List the three features of muscular arteries?
They have a thick layer of circular smooth muscle in their tunica media
They can accommodate an increase in diameter
They can contract to prevent haemorrhage
What do smooth muscle cells remain present in the media throughout all arteries?
Because the elements of control over distribution and flow is crucial in arteries
What are arterioles?
They are arteries less than 0.5mm in diameter
What is the difference between metarterioles and capillaries?
Metarterioles and capillaries are same in diameter but the first has on layer of smooth muscle in their walls, whilst the second is a tube of endothelium only
What does the subclavian artery turn into?
Axillary and brachial, then radial and ulnar
What is the name of the artery near the armpit?
Axillary
What is the name of the artery near the clavicle?
Subclavian
What is the name of the artery near the arm?
Brachial
What are the extra vessels around the elbow, shoulder and wrist? and what is their function?
They have collateral anastomoses and they allow flow/supply beyond the joint when it is compromised by being squeezed or in a weird position
What provides the collateral supply to the hand?
Deep and superficial palmar archs (arterial anastomoses)
Where are deep and superficial plamar archs derived from?
Radial and ulnar arteries
What does the common iliac artery split into? What do these branches supply?
Internal iliac artery supplies the pelvis
External iliac artery continues to the femoral artery and supplies the lower limb
What lies in the groin?
The common femoral artery lies within its vein medially and the femoral nerve laterally
Why is it important to know the relations between arteries, veins and nerves?
They are important when taking blood or inserting arterial cannulae
List the arteries beneath the popliteal artery
Anterior tibial, tibio-peroneal/fibular trunk, peroneal/fibular, posterior tibial
What is the special function of capillaries?
They are the only vessels that allow exchange of minerals (O2, CO2 and nutrients/hormones)
How do capillaries exchange of minerals?
By active transport and passive transport (osmosis, diffusion, filtration and facilitated transportation)
Why cannot capillaries contract?
Because they have no smooth muscles
What is the diameter of capillaries?
7 to 9 micrometers
Why does the basal lamina split?
To enclose pericytes
What are pericytes?
Myoepithelial cells that support endothelial cells
What regulates blood flow in capillaries?
Pre-capillary sphincter
What allows the exchange of larger molecules within capillaries?
Circular fenestrae of pores
State the types of capillaries
- Continuous capillary (most common, they are tight junctions between cells and are used for transportation)
- Fenestrated capillary (allow larger molecules to pass - in intestine)
- Sinusoid capillary (bigger gaps and are found in bone marrow)
Where are sinusoid capillaries found?
Bone marrow
Where are fenestrated capillaries found?
Intestine
What is the most common type of capillaries?
Continuous capillaries
How are veins classified?
According to their size
Why is the tunica media thin inside the veins?
There are only few smooth muscle fibres
Define diapedesis
The passage of leukocytes through the walls of venules
What are the smallest veins?
Venules
What function is found in veins but not in arteries?
Two valve leaflets that allow one-way blood flow and prevent back-flow
What covers the valve leaflets?
Endothelium
When do the valve leaflets close?
When the blood pressure proximal to the leaflets is greater than that distal to them
Larger arteries have separate veins alongside them, but what do smaller arteries have around them?
Venae comitantes (deep veins). They halp drive the venous return to the heart.
What are the two types of superficial arteries?
The great saphenous vein
The small saphenous vein
What connects the deep and superficial veins?
They are connected by perforating veins
Why is the venous flow from superficial to deep veins?
Due to the valves inside perforating veins
List the factors that help venous return to the heart against gravity?
- Valves inside the veins
- Contraction of the muscles (muscle pump)
- Arterial pulsation
- Negative intrathoracic pressure
What veins are used for phlebotomy and where do they lie?
Upper limb veins, and they are Cephalic, Basilic, Median cubital veins
What vessels are must be avoided when drawing blood?
Brachial artery and median nerve
State the large veins are what they supply
Inferior Vena Cava
- Lower limbs
- Pelvis organs
- Kidney
- Abdominal walls
Superior Vena Cava
- Head
- Neck
- Upper limb to right atrium
What are Azygos veins
They drain the venous blood of the thoracic wall to SVC
They do not follow arterial supply
What components do not have their venous return return directly to the heart?
GI tract and spleen
What vein takes drains blood from GI and spleen?
Hepatic Portal vein, which takes the venous blood through the liver before it then joins the IVC
What supplies blood to vessels?
Vasa Vasorum
What absorbs the interstitial fluid?
Lymph capillaries
Describe lymph capillaries
They are thin-walled, endothelial tubes
What is Lymph?
Interstitial fluid removed by the lymphatic system
Which lymph nodes are related to veins, and which are related to arteries?
Superficial are related to veins
Deep are related to arteries
What does drainage depends upon in lymphatic system?
Adjacent muscle activity and valves to prevent back flow
List the superficial lymphatic nodes
- Inguinal (superficial, alongside the GS vein in the groin, drain to the deep inguinal nodes)
- Deep Inguinal (alongside the femoral vein, drains the external genitalia, lower back and abdominal wall below umbilicus)
- Axillary
- Cervical (deep and superficial)
What do deep inguinal nodes drain?
External genitalia, lower back and abdominal wall below umbilicus
