Lecture 19 - Vascular System Flashcards
What is the innervation of arteries?
Vasomotor
Sympathetic innervation that controls the smooth muscle, and thus the diameter of the lumen
What is the structure of an artery?
Intima: endothelium
Media: smooth muscle
Adventitia: fibrous material
What is the major division of the circulatory system?
Pulmonary
Systemic
Describe blood flow around the heart
- Venous return via IVC and SVC into right atrium
- Right ventricle
- Pulmonary artery
- Lungs
- Pulmonary vein
- Left atrium
- Left ventricle
- Aorta
- Body
What are the different types of vessels?
Arteries Arterioles Capillaries Venules Veins Lymphatics Lymph vessels
Describe the flow of lymph around the body
- Interstitial fluid drains into lymph capillaries
- Afferent lymph vessels
- Lymph node
- Efferent lymph vessel
- Lymph duct
- Draining back into circulation
Why is there a pressure difference in the pulmonary and systemic circulation? What is this difference?
Pulmonary: low pressure, because the blood doesn’t have to travel far
Systemic: high pressure, because the blood must travel all around the body
Is any part of the body avascular?
Yes:
Epidermis
Articular cartilage
How may an artery and vein be distinguished when dissecting?
Arteries always have a lumen, due to the thick smooth muscle wall
Veins collapse, and there is no visible lumen
When does an artery normal branch?
At a joint, such as the elbow
What are the different branches that an artery can form?
Muscular branch Nutrient branch Articular Cutaneous Arteriae nervorum Vasa vasorum
Where does an artery usually run?
Down the midline, in the flexor compartment
Arteries conduct high pressure blood. What confers this function?
The elastic fibres in the artery wall allow it to expand, and then bounce back to push the blood on
How does the body control blood flow to different regions in different conditions?
The smooth muscle in the wall confers this property
When activated, the artery restricts in areas where excess blood is not needed.
The artery dilates where more blood is needed
What is one of the main functions of arterioles?
‘Resistance vessels’
Control the flow and pressure into the capillaries
What is the main function of capillaries?
‘Exchange vessels’
They have a very thin wall that allow them to carry out this function
What is an anastomosis?
This is when two arteries meet without a communicating capillary
They provide collateral circulation
What is collateral circulation?
Alternative routes of circulation
We’re are anastomoses usually found?
In skeletal muscle
Joints, where circulation may be impaired due to bending of joint
What is an anatomical end artery?
Where are they usually found?
These are arteries that do not connect with another artery
They are normally found in region that hang or stick out
Finger Toes Brain Heart Appendix
What are the two types of end arteries?
- Anatomical
* Functional / potential anastamosis
Why are end arteries clinically important?
Blockage of an end artery by an embolus will cut of all blood supply to that region
Ischemia – necrosis
Describe the vasculature of the end of a growing bone
The epiphyseal plate is avascular. Thus, there are two end arteries in the bone on either side.
When growth is finished, these arteries anastomose
What is an end organ?
It is an organ whose blood supply is an end artery
What are functional end arteries?
This is when, over time, end arteries anastomose due to some sort of pathology
Eg. In heart, an ongoing condition whereby the arteries are narrowed will cause anastomosis of coronary end arteries
In a sudden narrowing of vessels, there isn’t time for the arteries to anastomose, and tissue ischemia and necrosis will result
What is the difference between a thrombus and an embolus?
Thrombus: fibrinous clot that forms and blocks a vessel
Embolus: obstruction present in circulation, may be a detached thrombus, or a gas bubble
What is the structure of veins?
Intima: endothelium
Media: thin smooth muscle
Adventitia: fibrous material
Why is the lumen in veins wider than in arteries?
Greater volume of blood which is at lower pressure
Describe the function of valves
Valves are flaps of tissue in veins that close to prevent the back flow of blood
What systems allow blood to be returned to the heart by the veins?
- Venous valves
- Muscular pump
- Thoracic pump
What defects can occur in venous valves?
Incompetent valves –> varicosed veins
What is one of the special relationships between arteries and veins?
Venae comitantes
Where are venous valves present?
In the veins of the appendages, not in the trunk
Especially in superficial veins
Valves in perforating veins moving through the deep fascia
What are venae comitantes?
These are veins in close contact with arteries.
Function:
• Heat transfer
• Pulsation of arteries moves blood back to heart
Describe how the muscular pump works
When skeletal muscle in the leg contracts, the veins embedded in the muscle are affected, and the blood in them is shunted up the veins
Describe how the thoracic pump works to return blood
During inhalation, the pressure in the thoracic cavity drops slightly.
The blood flows into this region of lower pressure
What does Boyle’s law say?
How does this apply to inhalation
When volume increases, pressure decreases
When one inhales, the volume in the thoracic cavity increases and the pressure decreases slightly
What are perforating veins?
These are veins that perforate the deep fascia, and thus move blood from superficial veins into deep veins
What is the deep fascia?
This is thick connective tissue surrounding skeletal muscle
The presence of tortuous lumps in the veins indicates…
Varicosed veins
What is the most important principle of lymph flow?
Lymph must pass through AT LEAST ONE lymph node before returning to circulation
What is lymph made up of?
The tissue fluid that it drains:
- plasma proteins
- white blood cells
Where is lymph returned to circulation?
In the veins in the neck
Right and left side
Left side receives lymph from most of the body
What are the functions of lymph?
- recovering proteins from interstitial fluid
- presenting invading organisms to the adaptive immune system
What is one commonality between veins and lymph vessels?
Valves to ensure uni-directional flow
What sort of tissue is a lymph node made up of?
Lymphatic tissue
Where are lymph nodes predominantly found?
Cervical: neck
Axillary: armpits
Inguinal: groin
Where is lymphatic tissue found?
Lymph nodes Thymus Tonsils Peyer's patches: intestine Spleen
What causes elephantiasis?
A thread worm blocks the lymphatics.
Tissue fluid in the lower limbs is not drained
Oedema in the lower legs
What is lymphedema?
This is when lymph nodes are resected in a surgery (ed. mastectomy) and the tissue fluid in the lower limbs does not drain
What would a thromboembolus from the venous system potentially cause?
Pulmonary embolysm
What would a thromboembolus from the arterial system potentially cause?
Stroke (in brain)
